U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2011–5202

Prepared in cooperation with the U.S. Department of Agriculture, Natural Resources Conservation Service, 

Wisconsin Department of Natural Resources, and Wisconsin Department of Health Services

Distribution and Variation of Arsenic in Wisconsin Surface 

Soils, With Data on Other Trace Elements

Distribution and Variation of Arsenic in 

Wisconsin Surface Soils, With Data on 

Other Trace Elements

By Krista A. Stensvold

Prepared in cooperation with the U.S. Department of Agriculture, Natural 

Resources Conservation Service, Wisconsin Department of Natural Resources, 

and Wisconsin Department of Health Services

Scientific Investigations Report 2011–5202

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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Suggested citation:

Stensvold, K.A., 2012, Distribution and variation of arsenic in Wisconsin surface soils, with data on other trace 

elements: U.S. Geological Survey Scientific Investigations Report 2011–5202, 41 p., 1 app.
iii

Contents

Acknowledgments.........................................................................................................................................v

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................2

Study Area..............................................................................................................................................3

Methods...........................................................................................................................................................3

Site Selection.........................................................................................................................................3

Sample Collection.................................................................................................................................3

Laboratory Analysis..............................................................................................................................6

Statistical Analysis ...............................................................................................................................6

Distribution and Variation of Arsenic .........................................................................................................8

Statewide Arsenic Distribution ..........................................................................................................8

Comparison of Soil Arsenic Concentrations Across Geographic Regions.................................9

Comparison of Soil Arsenic Concentrations in Soil Groups ........................................................11

Data on Other Trace Elements...................................................................................................................11

Summary and Conclusions.........................................................................................................................12

References Cited..........................................................................................................................................13

Figures

1. Boundaries of the geographic regions used for comparison of data in the 

arsenic baseline study. ...........................................................................................................4

2. Spatial distribution of arsenic concentrations of surface soil samples in 

Wisconsin .................................................................................................................................8

3. Statistical distribution of arsenic concentrations of surface soil samples in 

Wisconsin, categorized by the geographic regions shown in figure 1 and 

described in table 1, with outliers removed ........................................................................9

4. Statistical distribution of arsenic concentrations of surface soil samples in 

Wisconsin, categorized by soil characteristic group described in table 2, with 

outliers removed ....................................................................................................................12

Tables

1. Description of the geographic regions used for the arsenic baseline study, 

Wisconsin .................................................................................................................................5

2. Description of the soil-characteristic groups for the arsenic baseline study, 

Wisconsin .................................................................................................................................5

3. Seventeen trace elements included in the analysis by the Wisconsin State 

Laboratory of Hygiene for each soil sample taken in the arsenic baseline 

study...........................................................................................................................................6
iv 

4. Statistical summary, including 95-percent upper confidence limit of the mean 

of arsenic data from surface soil samples in Wisconsin..................................................7

5. P-values from the Wilcoxon rank-sum test for comparing two sets of data on 

arsenic concentrations in Wisconsin surface soils ........................................................10

Appendix Figures

1–1. Facsimile of draft field procedure work plan for Wisconsin arsenic 

sampling project ......................................................................................................................9

 Maps showing spatial distribution of trace-element concentrations of surface 

soil samples in Wisconsin....................................................................................................11

1–2. Aluminum ................................................................................................................................10

1–3. Barium .....................................................................................................................................11

1–4. Calcium ....................................................................................................................................12

1–5. Cadmium..................................................................................................................................13

1–6. Cobalt .......................................................................................................................................14

1–7. Chromium.................................................................................................................................15

1–8. Copper......................................................................................................................................16

1–9. Iron............................................................................................................................................17

1–10. Magnesium..............................................................................................................................18

1–11. Manganese .............................................................................................................................19

1–12. Molybdenum ...........................................................................................................................20

1–13. Nickel .......................................................................................................................................21

1–14. Lead..........................................................................................................................................22

1–15. Strontium .................................................................................................................................23

1–16. Vanadium.................................................................................................................................24

1–17. Zinc...........................................................................................................................................25

Appendix Tables

1–1. Complete dataset for arsenic baseline study. 

This table, in Microsoft Excel format, is available for downloading at 

http://pubs.usgs.gov/sir/2011/5202/.....................................................................................26

1–2. Statistical summary, including 95-percent upper confidence limit of the mean, 

of trace element data from surface soil samples in Wisconsin. ...................................27
v

Acknowledgments

The author would like to thank the soil scientists from the U.S. Department of Agriculture, 

Natural Resources Conservation Service for their assistance in the creation and implementation 

of the study design. Many thanks to Ed Lynch and Aristeo Pelayo from the Wisconsin Department of Natural Resources, David Hall and Douglas Causey from the U.S. Geological Survey, 

DeWayne Kennedy-Parker from the Wisconsin State Laboratory of Hygiene, and Henry NehlsLowe from the Wisconsin Department of Health Services for providing technical guidance during 

the report preparation. Also, thanks to Mike Eberle and Laurel Woodruff from the U.S. Geological Survey and Bruce Rheineck from the Wisconsin Department of Health Services for the valuable technical and editorial review comments that they gave on previous drafts, which helped 

improve this report greatly.

Conversion Factors

Multiply By To obtain

Length

inch (in.) 25.4 millimeter (mm)

inch (in.) 2.54 centimeter (cm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 0.4047 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2)

Mass

gram (g) 0.03527 ounce, avoirdupois (oz)

kilogram (kg) 2.205 pound avoirdupois (lb)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as 

follows:°F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as 

follows:°C=(°F-32)/1.8

Horizontal coordinate information is referenced to the World Geodetic System of 1984 (WGS 84).

Distribution and Variation of Arsenic in Wisconsin Surface 

Soils, With Data on Other Trace Elements

By Krista A. Stensvold

Abstract

A total of 664 soil samples distributed among different geographic regions and soil types were collected across 

Wisconsin to describe the distribution of arsenic relative to 

parent material, soil texture, and drainage class. Soils from 

6 inches in depth were composited, digested in aqua regia, and 

analyzed for 17 trace elements. Observed soil arsenic concentrations range from a high of 39 milligrams per kilogram 

(mg/kg) to less than the laboratory detection limit of 1 mg/kg. 

Ten samples with soil arsenic concentrations greater than 

8.5 mg/kg were determined to be significantly separate from 

the main cluster of the dataset. With these outliers removed, 

overall soil arsenic concentrations in Wisconsin have a median 

value of 1.8 mg/kg, and the 95-percent upper confidence limit 

of the mean is 2.4 mg/kg. 

Soils with sandy glacial outwash as a parent material 

have a lower median arsenic concentration (1.0 mg/kg) than 

soils forming in other parent materials (1.5 to 3.0 mg/kg). Soil 

texture and drainage category also influence median arsenic 

concentration. Finer grained soils have a higher observed 

range of concentrations. For loamy and loess-dominated 

soil groups, drainage category influences the median arsenic 

concentration and observed range of values, but a consistent 

relationship within the data is not apparent. Statistical analysis 

of the 16 other elements are presented in this report, but the 

relationships of concentrations to soil properties or geographic 

areas were not examined.

Introduction

Arsenic, a trace element commonly found in surface 

soils, has both natural and anthropogenic sources. In uncontaminated soils, the most common natural source of arsenic 

is arsenic-bearing minerals in soil parent materials. Arsenicbearing minerals, such as glauconite, arsenopyrite, pyrite, and 

other sulfides, can weather in soils and release arsenic into the 

soil system. Arsenic-bearing minerals are commonly found in 

sedimentary rocks (Smith and others, 1998). Deposition from 

atmospheric sources of arsenic can contribute significantly 

to arsenic concentrations in soils. The ratio of atmospheric 

natural sources, such as volcanic activity, to atmospheric 

anthropogenic sources, such as fossil fuel combustion, varies 

regionally but on average their mutual contributions are about 

equal (O’Neill, 1995). Other non-atmospheric anthropogenic 

sources include industrial and mining waste products and agricultural applications (Smith and others, 1998). Elevated levels 

of arsenic in soils can compromise the health of the soil system as well as human health. The greatest risk to human health 

is through exposure that comes from arsenic that has leached 

from soils or bedrock into drinking-water sources (Das and 

others, 1996; Smith and others, 2000). Repeated exposure to 

arsenic at elevated concentrations can be toxic to the human 

system (Southworth, 1995; Das and others, 1996).

If known, baseline arsenic concentrations can be used 

as a guideline for assessing contamination levels of soils 

and may be part of the process of regulating the cleanup of 

contaminated soils. An element’s baseline is defined as a range 

of concentrations around a mean, but the baseline does not 

strictly represent a natural background concentration because 

the range of values will also include contributions from nonpoint sources of anthropogenic arsenic (Gough, 1993; KabataPendis, 2001). States have used a variety of common statistics 

to characterize the baseline concentration in soils for cleanup 

purposes, including (1) the mean concentration (Illinois Environmental Protection Agency, 2007); (2) the 95th-percentile 

concentration (Vosnakis and others, 2009); and (3) the 95-percent upper confidence limit of the mean (Kentucky Energy and 

Environment Cabinet, 2004; Montana Department of Environmental Quality, 2005). However, existing data in most states 

are not abundant enough to properly estimate baseline arsenic 

concentrations.

Baseline concentrations can have natural variations that 

are influenced by a soil’s physical and chemical properties. 

Arsenic availability in a soil system is controlled by chemical processes, mainly sorption, which is affected by specific 

physical and chemical soil properties. The presence of iron, 

aluminum, and manganese oxides increases the sorption 

of arsenic to soil surfaces (Elkhatib and others, 1984). Soil 

with fine-grained textures, such as clays, and soils with high 

organic matter content, such as wetland soils, have more 

exchange sites and thus have higher sorption capacity (Chen 

and others, 1999; Girouard and Zagury, 2009). Arsenic sorption on oxides, clays, and organic material can be influenced 
2 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

by pH (Frost and Griffen, 1977; Thanabalasingam and Pickering, 1986; Goldberg and Glaubig, 1988) and redox conditions 

(Kabata-Pendias, 2001).

Regional studies have quantified arsenic concentrations 

in soils with respect to parent material and soil physical and 

chemical properties. In New Jersey, soil samples were analyzed from three physiographic provinces: Valley and Ridge, 

Highlands, and Coastal Plain (Sanders, 2003). Mean arsenic 

concentrations of the Valley and Ridge and the Highlands 

provinces (4.98 and 6.04 mg/kg, respectively) were found 

to be significantly different from that of the Coastal Plain 

province (2.33 mg/kg). It is assumed, given the study design, 

that these differences were due to differences in soil parent materials among the three provinces. A California study 

developed a comprehensive database of trace elements in 

soils to determine baseline concentrations in benchmark soils 

(Bradford and others, 1996). In that study, positive correlation 

coefficients for some elements (for example, iron-vanadium, 

nickel-chromium, and copper-cobalt) indicated that chemical 

and physical properties of soils and parent materials influenced 

trace element distribution within a soil. Other states have also 

attempted to identify variations in baseline concentrations 

on the basis of changes in soil texture and parent material 

(Michigan Department of Environmental Quality, 2005) and 

soil taxonomic orders and chemical characteristics (Chen and 

others, 2002). For example, Chen and others (2002) found 

that wetland soils in Florida had high arsenic concentrations, 

which were attributed to immobilization of arsenic by high 

concentrations of organic matter, iron and aluminum oxides, 

and clays that accumulated in wetlands.

A low-density geochemical soil survey of the United 

States (approximate spacing of one site per 6,000 km2 (2,300 

mi2)) was completed by scientists from the U.S. Geological 

Survey (USGS). During this survey, soil samples were collected from a depth of about 20 cm (8 in.) across the conterminous United States from 1958 to 1976 (Boerngen and 

Shacklette, 1981; Shacklette and Boerngen, 1984). As part of 

the National Uranium Resource Evaluation Program (NURE), 

the Hydrogeochemical and Stream Sediment Reconnaissance 

(HSSR) component collected stream sediments across the conterminous United States between 1976 and 1984. The initial 

purpose of NURE was to identify potential uranium resources, 

but the scope was broadened to include analyses of additional 

elements, creating a second national-scale geochemical survey 

for the United States (Smith, 1997). Sampling density for the 

NURE program ranged from one sample per 10 km2 (3.9 mi2) 

to one sample per 23 km2 (8.9 mi2) (Information Systems 

Programs-Energy Resources Institute, 1985). Samples selected 

for a systematic reanalysis of NURE soil and stream sediment samples by the USGS to improve data quality have a 

sampling density of about one per 289 km2 (112 mi2). Data 

from these studies and more recent regional USGS geochemical baseline studies are available in the National Geochemical 

Survey database (U.S. Geological Survey, 2004). The National 

Geochemical Survey contains total elemental data from soil, 

stream sediment, and rock samples collected across the United 

States, though stream sediment samples make up the majority 

of the data. 

Soil analyses in the National Geochemical Survey 

database have been used to characterize regional soil composition. Grosz and others (2004) combined the U.S. data with an 

extensive Canadian geochemical database to create a map of 

arsenic concentrations. Their results show that typical arsenic 

concentrations in northern Wisconsin are less than 0.5 mg/kg 

and that the observed variability in surficial arsenic concentrations is controlled by bedrock characteristics. Cannon and 

others (2004) reanalyzed archived NURE stream sediment 

samples collected across northern Wisconsin. These data were 

compared to near-surface and subsurface soil samples collected from the same area to determine whether stream sediment samples could predict regional geochemical patterns in 

soils. Comparison of mean element concentrations of the three 

sample groups (stream sediments, surface soils, subsurface 

soils) showed that element concentrations among the groups 

were significantly different from one another. However, with 

some statistical manipulation that included multiple-sample 

averaging and smoothing, stream sediment data could be 

extrapolated to soil compositions for some elements (Cannon 

and others, 2004). Thus, in the absence of a high-density soil 

geochemical dataset, element concentration predictions based 

on stream sediment geochemistry could be used for regional 

background concentrations for some elements (Cannon and 

others, 2004).

Despite these efforts to collect and compile a comprehensive geochemical database, sufficient data do not exist to 

determine baseline reference values for all of Wisconsin’s 

soils. The USGS, in cooperation with the U.S. Department of 

Agriculture, Natural Resources Conservation Service (NRCS), 

Wisconsin Department of Natural Resources (WDNR), and 

Wisconsin Department of Health Services, designed this study 

to collect trace element data from samples that are representative of all soils types and parent material sources in the State 

of Wisconsin. Data from this study will be used to characterize 

the baseline concentration of arsenic and any variation in this 

baseline value that may be a result of changing soil physical 

and chemical properties or parent material.

Purpose and Scope

The objective of this report is to describe the distribution 

of arsenic in Wisconsin surface soils and identify potential 

systematic variations of arsenic concentrations with respect 

to soil properties or parent materials. This information about 

the distribution and controls on arsenic concentrations in soils 

across Wisconsin could be helpful for the determination of 

regulatory levels of arsenic in soils. Sampling and analytic 

methods were designed to exclude obvious anthropogenic 

influences to achieve values that are as close as possible to a 

natural baseline while recognizing that few areas are pristine.

Data from this study are not directly comparable to 

the geochemical data in the USGS National Geochemical 
Methods 3

database. The samples in this study were analyzed by using 

an aqua regia partial digestion technique rather than a fouracid total digestion method that was common for the NURE 

program and the soils collected for the Shacklette and Boerngen (1984) survey. The partial digestion method was used 

as results from this analytical method are indicative of the 

environmentally available fraction for each element and are 

thus more comparable to values required by the regulatory 

community. 

Study Area

The state of Wisconsin comprises approximately 35 

million acres. Glaciers played a significant role in the formation of both the landscape and the soils. Three-fourths of the 

soils in the State are forming in glacial deposits made up of 

sand and gravel derived from glacial outwash, loamy glacial 

tills, or glacial lacustrine sediments, whereas the remainder 

of the soils are developing in either loess deposits or bedrock 

residuum (Syverson and Colgan, 2004; U.S. Department of 

Agriculture, 2006). Sampling for this study focused on soils 

under natural vegetation regimes that ranged from forest to 

wetland to prairie and avoided soils forming under disturbed 

agricultural and urban landscapes (Hole, 1976).

Methods

Site Selection

The site selection and soil sampling for this project were 

done by the NRCS, and were designed to meet two objectives. The first objective was to represent the major variations 

in soil type and parent material proportional to their current 

areal extent. The second objective was to sample locations that 

would best represent naturally occurring arsenic concentration 

in surface soils. The target sample count was 650 samples, 

resulting in a sampling density of 1 sample per 84 mi2. A 

detailed description of the site selection and sampling plan is 

given in the appendix (fig. 1–1). 

To meet the first study objective, the State was divided 

into six geographic regions; within each of the six regions, 

soils were assigned into nine soil groups on the basis of parent 

material, surface texture, and drainage. The six geographic 

regions are based on differences in parent material, primarily influenced by glacial history, including time interval of 

glacial advance and direction of flow representing differences 

in source and age of parent material. The six regions are (1) 

Copper Falls Formation (2) Green Bay Lobe, (3) Lake Michigan Lobe, (4) Central Sands, (5) Driftless Area, and (6) Des 

Moines Lobe. These regions are shown in figure 1, and brief 

descriptions of the parent materials (Syverson and Colgan, 

2004) and glacial history (Clayton and others 2006) are listed 

in table 1.

The different soil series in Wisconsin were placed into 

nine soil groups based on a combination of parent material, 

surface layer texture, and NRCS drainage classification of 

the series (U.S. Department of Agriculture, Soil Survey Staff, 

1993). Detailed descriptions of the nine soil groups are listed 

in table 2. The soil groups were sampled in proportion to their 

areal extent within a geographic region, with a minimum of 

two samples per soil group per region. 

Actual sampling locations were determined in the field 

and were selected with reference to the following criteria to 

fulfill the second objective of this study:

1. Must be in a forested lot, permanent pasture, or otherwise 

undisturbed area at least 20 ft away from a fence line.

2. Must not be within 1 mi of any other arsenic study sample 

site.

3. Must not be within 5 mi of any other sample from the 

same soil group.

4. Must not be within 100 ft of existing known historical 

construction site or disturbed area (such as roads, dumps, 

pits, pipelines, or homesites). 

5. Must not be within 300 ft of a potential source of contamination (for example, past or present orchard or vegetable 

growing area; cattle-dipping sites; wood preservation 

activities; grasshopper bait; land that has had poultry or 

swine manure, sewage waste, or paper mill sludge applied 

to it; areas listed by the WDNR Bureau for Remediation 

and Redevelopment Tracking System).

These guidelines were followed as closely as possible, 

although in some cases it was not possible to meet all five 

criteria.

Sample Collection

Samples were collected at 664 locations across Wisconsin 

during late fall 2006 and spring, summer, and fall 2007. 

Following field selection of an appropriate sampling location, 

a brief in-field description and classification (to the series 

level) of the soil profile at the sampling site was done prior to 

sampling. This step provided field verification of soil series 

and, therefore, soil group. Geographic coordinates were 

recorded for each site with a handheld global positioning 

system (GPS). A sample was taken from the upper 6 inches 

of the soil profile, first discarding by hand any overlying 

undecomposed organic material as well as any coarse 

fragments contained within the sample. The samples were 

collected with a stainless steel spade and stored in laboratorygrade plastic bags. At 62 locations (approximately 10 percent 

of the sites), two samples were collected, composited, and 

then split. These field duplicate samples were submitted to the 

same laboratory as the primary samples for quality-assurance 

purposes.
4 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

92° 90° 88°

46°30'

45°

43°30'

42°

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

0 25 50 MILES

0 50 KILOMETERS 25

EXPLANATION

Figure 1. 

Lake Superior

Lake Michigan

ILLINOIS

WISCONSIN

IOWA

MICHIGAN

MINNESOTA

Figure 1. Boundaries of the geographic regions used for comparison of data in the arsenic baseline study.
Methods 5

Table 1. Description of the geographic regions used for the arsenic baseline study, Wisconsin.

[%, percent of State area; ka, kiloannum (thousands of years ago)]

Geographic region Area (%) Most recent glacial 

deposition (ka)2 Parent material1 Direction of glacial advance2

Copper Falls Formation 39.6 26–14 Lacustrine silts and clays in the northwest, 

sandy tills in the remaining area.

South-southwest

Green Bay Lobe 29.9 25–9 Clay tills in northeast and sandy tills in 

southwest.

Southwest

Lake Michigan Lobe 4.0 25–9 Fine-textured tills. Southwest

Central Sands 6.8 19–14 Unconsolidated sand, glacial outwash. —

Driftless Area 19.1 — Loess, residuum. —

Des Moines Lobe 0.6 14–12 Silty, calcareous tills. East-southeast

1

Syverson and Colgan, 2004.

2

Clayton and others, 2006.

Table 2. Description of the soil-characteristic groups for the arsenic 

baseline study, Wisconsin.

[Drainage category: PD, poor to very poor drainage; WD, somewhat poor to excessive 

drainage]

Soil group Soil texture

PD, Loess Loess or loess derived silts.

WD, Loess Loess or loess derived silts.

PD, Sand Sand or loamy sand.

WD, Sand Sand or loamy sand.

PD, Clay Sandy clay, clay, clay loam, silty clay loam, or silty clay.

WD, Clay Sandy clay, clay, clay loam, silty clay loam, or silty clay.

PD, Loam Silt, silt loam, loam, or sandy loam.

WD, Loam Silt, silt loam, loam, or sandy loam.

Organic Organic soils.
6 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

Laboratory Analysis

Samples were sent to the Wisconsin State Laboratory of 

Hygiene (WSLH) for chemical analysis of 17 trace elements 

(table 3). Individual samples were oven-dried at 103°C, sieved 

to less than 2 mm (about 0.079 in), and ground to increase 

subsample homogeneity for analysis. An aliquot of each 

sample was refluxed in nitric and hydrochloric acid to bring a 

number of elements into aqueous solution. This type of aqua 

regia partial digestion results in an extract from which the total 

recoverable portion of a particular element can be measured 

and excludes the portion of that element that resides in the 

silicate structure of soil minerals. The extraction solution 

was analyzed for 17 trace elements by using inductively 

coupled plasma-atomic emission spectrometry (ICP-AES; 

Method 200.7, U.S. Environmental Protection Agency, 1994). 

The resulting concentration is considered to represent the 

environmentally available portion of a trace element that 

would be available for biological uptake or mobile within the 

soil system under ideal conditions.

Analytical precision was calculated by taking the average 

percent difference between duplicate samples (table 3). 

Duplicate pairs were included in the overall average only if 

both samples had values above the detection limit. Average 

Table 3. Seventeen trace elements included in the analysis by 

the Wisconsin State Laboratory of Hygiene for each soil sample 

taken in the arsenic baseline study. (Calculations of analytical 

precision values are described in the laboratory methods 

section.)

[mg/kg, milligrams per kilogram; %, percent]

Element Detection limit 

(mg/kg)

Analytical precision 

(%)

Aluminum 1.0 14

Arsenic 1.0 25

Barium 0.5 20

Calcium 10 26

Cadmium 0.1 38

Chromium 0.5 14

Cobalt 0.5 17

Copper 0.5 24

Iron 10 17

Lead 1.0 25

Magnesium 10 17

Manganese 0.1 20

Molybdenum 1.0 18

Nickel 0.5 13

Strontium 0.5 20

Vanadium 0.5 15

Zinc 0.5 18

precision percentages for each of the trace elements ranged 

from 14 and 38 percent. For this study, one source of error 

in analytical precision is the general heterogeneity of the soil 

matrix. The way that a specific trace element is distributed 

within a soil sample depends largely on particle size and 

organic matter concentration. An unequal distribution of 

these characteristics within each subsample split can cause 

disparity between analytical results for the same field sample. 

Another source of error that is specific to the arsenic data is 

low concentrations relative to the method detection limit. 

The limit of quantification for this method when analyzing 

arsenic is 3 mg/kg. When a value drops below this limit but is 

above the method limit of detection of 1 mg/kg, uncertainty 

is high and variability can also be high (D. Kennedy-Parker, 

Wisconsin State Laboratory of Hygiene, written commun., 

2008). Additionally, when overall trace element concentrations 

are particularly low, uncertainty can be attributed to spectral 

interferences, which will result in a sample having a negative 

result. In most cases, compensation for such interference can 

be used to adjust a value and report a corrected concentration 

given for a sample. Of the 733 primary and duplicate samples 

analyzed, 120 were reported as negative values, possibly as 

a result of this interference (D. Kennedy-Parker, Wisconsin 

State Laboratory of Hygiene, written commun., 2009).

As a result of the high level of variability in our dataset 

and the high incidence of “censored” or “non-detect” values 

(that is, values reported as less than the method detection 

limit), we examined our data to determine which samples to 

include in a subset of samples that would be submitted to the 

WSLH for reanalysis. Samples that were chosen included 

those with a reported arsenic concentration greater than 

8 mg/kg, a portion of the samples reported as non-detect 

values, and main and duplicate samples whose concentrations 

had an absolute difference of 1 mg/kg or greater. In 2009, 

a subset of 81 samples from the original 726 samples was 

reanalyzed, and results are included in the appendix, in 

table 1–1. Columns are labeled with a “2” after the type of 

sample in the heading, for example, As_value_main2. Where 

applicable, the results of the reanalysis were compared to 

the corresponding primary sample data, and the higher of 

the two concentrations was used in statistical calculations. 

These final arsenic values are labeled in appendix table 1 as 

As_value_final.

Statistical Analysis

All statistics were calculated by using the ProUCL 

statistical package (U.S. Environmental Protection Agency, 

2010). ProUCL is a public domain software package 

released by the U.S. Environmental Protection Agency 

for environmental datasets in support of site evaluation, 

risk assessments, and cleanup regulations. This software 

was created for critical statistical concerns in any baseline 

concentration study and is designed to (1) manipulate censored 

datasets, (2) test and identify outliers, and (3) identify data 

distribution. The ProUCL software has several parametric and 
Methods 7

nonparametric statistical methods that can be used to estimate 

upper limits and upper percentiles, commonly used to estimate 

baseline threshold values of datasets, including censored 

datasets. The test for outliers is separate from the calculation 

of upper limits and percentiles, so after removal of the outliers, 

another iteration is necessary to determine the higher-order 

statistics. 

The main objective of using statistics in this study was 

to model the majority of the arsenic data representing the 

main dominant population rather than to accommodate high 

outlying observations that may yield inflated higher-order 

statistics. Multiple summary statistics were calculated for 

the entire dataset as well as subsets of the data defined by the 

geographic and soil groups described in tables 1 and 2. The 

fundamental assumptions for calculating upper confidence 

limits of the mean (UCL) are that all of the data belong to a 

single population and that outliers are removed (Singh and 

others, 2006). The Wisconsin soil arsenic dataset did not have 

either a parametric or lognormal distribution, so nonparametric 

methods were used when applicable. Prior to calculating 

summary statistics, outliers were identified using Rosner’s 

outlier test. The outliers in all cases were unusually large 

values and were removed on the assumption that the sample 

represented a site that was likely more heavily influenced 

by anthropogenic sources of arsenic than was desired for the 

purposes of this study. At the 1-percent significance level a 

total of 10 outliers were removed (samples with concentrations 

greater than 8.5 mg/kg), leaving 654 samples in the dataset 

for further statistical analysis. Owing to the nature of the 

dataset and laboratory analysis method, there was a large 

percentage of samples with arsenic concentrations below the 

laboratory detection limit of 1 mg/kg (table 4). ProUCL has 

multiple censored data methods available depending on data 

distribution and the level of censoring within a dataset. For 

this study we used the Kaplan-Meier estimation methods for 

the summary statistics with bias-corrected bootstrap method 

for computing the 95-percent upper confidence limit. The 

choice of these methods was based on guidance in Singh 

and others (2006). The nonparametric Wilcoxon rank-sum 

test was used to determine whether significant differences 

exist in the distributions of arsenic data among individual 

geographic regions or soil groups. This test is quite similar 

to the more common student’s t-test but is more robust if 

data are not normally distributed. All statistics, outlier tests, 

and summary statistics were applied to the other 16 trace 

elements, and results are listed in the appendix (table 1–2). 

Data for molybdenum had a very high percentage of nondetects (91 percent; appendix, table 1–2), so outlier tests and 

most summary statistics for that element were unable to be 

estimated with the methods used in this study.

Table 4. Statistical summary, including 95-percent upper confidence limit of the mean (95% UCL) of arsenic data from surface soil 

samples in Wisconsin. Summaries for the entire data set and for groups described in tables 1 and 2 were calculated after outliers 

were removed.

[%, percent; PD, poor to very poor drainage; WD, somewhat poor to excessive drainage; CFF, Copper Falls Formation; GBL, Green Bay Lobe; LML, Lake 

Michigan Lobe; CS, Central Sands; DA, Driftless Area; DML, Des Moines Lobe] 

Soil group 

or region 

Number of 

samples

Non-detects 

(%)

Minimum 

detected 

value

Maximum 

detected 

value

Median Mean 95% UCL 90th 

percentile

95th 

percentile

99th 

percentile

All samples 654 32 1.0 8.3 1.8 2.3 2.4 4.3 4.8 5.9

PD, Loess 11 18 1.1 4.1 1.8 2.4 3.1 3.8 4.2 5.0

WD, Loess 171 15 1.1 8.0 3.0 3.0 3.2 5.0 5.6 6.6

PD, Sand 17 53 1.1 4.5 <1 1.7 2.4 3.0 3.4 4.0

WD, Sand 116 59 1.0 4.2 <1 1.3 1.4 2.1 2.3 2.7

PD, Clay 12 25 1.7 6.0 2.9 3.1 3.9 4.8 5.3 6.3

WD, Clay 13 31 1.3 6.0 2.8 3.1 4.4 5.3 5.9 7.1

PD. Loam 29 21 1.5 7.7 2.6 3.4 4.1 6.1 6.8 8.2

WD, Loam 221 32 1.0 8.3 1.5 2.2 2.3 4.0 4.5 5.4

Organic 64 36 1.1 7.5 1.6 2.1 2.5 4.0 4.5 5.5

CFF 253 30 1.0 6.8 1.5 2.0 2.1 3.5 3.9 4.7

GBL 192 43 1.1 8.3 1.5 2.2 2.4 4.2 4.7 5.8

LML 31 10 1.1 8.0 2.2 3.1 3.8 5.8 6.6 8.0

CS 42 50 1.0 6.5 1.0 1.7 2.1 3.2 3.7 4.5

DA 122 18 1.0 7.8 3.0 3.0 3.3 5.1 5.7 6.9

DML 14 50 3.0 7.5 2.0 4.0 5.5 5.8 6.4 7.3
8 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

Distribution and Variation of Arsenic

Statewide Arsenic Distribution

Concentrations of arsenic in surface soils for the entire 

state of Wisconsin ranged from a high of 39 mg/kg to values 

below the laboratory detection limit (1 mg/kg, table 4). 

Because samples with arsenic values greater than 8.5 mg/

kg were determined to be outliers and removed from the 

dataset prior to calculation of summary statistics (appendix, 

table 1–1), the total number of samples used for the statistical 

analysis is 654. Of those 654 samples, 210 had concentrations 

below the detection limit of 1 mg/kg. The median value for 

the dataset (n=654) was 1.8 mg/kg, and the calculated mean 

was 2.3 mg/kg. The 95-percent upper confidence limit of the 

mean was 2.4 mg/kg and the, 90th, 95th, and 99th percentiles 

were 4.3, 4.8, and 5.9 mg/kg, respectively (table 4). Figure 2 

shows the sampling locations for the study; symbols on the 

map represent one of four arsenic concentration-based groups, 

as well as outliers. The first concentration group (<1.0 mg/kg), 

signified by an open box symbol, represents the sample sites 

where arsenic values were below the method detection limit. 

92° 90° 88°

46°30'

45°

43°30'

42°

<1.0

1.0 to 2.0

>2.0 to 4.0

>4.0 to 8.5

>8.5

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

EXPLANATION

Arsenic concentration (mg/kg)

0 25 50 MILES

0 50 KILOMETERS 25

0 8 16 24 32 40

100

150

50

0

200

Arsenic concentration (mg/kg)

Number of samples

Figure 2. 

Lake Superior

Lake Michigan

ILLINOIS

IOWA

MICHIGAN

MINNESOTA

WISCONSIN

Figure 2. Spatial distribution of arsenic concentrations of surface soil samples in Wisconsin. The 

histogram in the figure shows the frequency distribution of the arsenic concentrations. Data displayed 

in both the map (red squares) and the histogram include outliers that were removed prior to statistical 

analysis. (mg/kg, milligrams per kilogram)
Distribution and Variation of Arsenic 9

Outlier values are shown as red box symbols (concentration 

>8.5 mg/kg). The remainder of the samples are broken into 

three additional arsenic concentration-based groups (1.0 to 

2.0 mg/kg, >2.0 to 4.0 mg/kg, and >4.0 to 8.5 mg/kg). There 

are noticeable spatial patterns in arsenic concentrations 

across the State (fig. 2). In the north and central parts, arsenic 

concentrations are in the lower concentration ranges, whereas 

in the southwest and southeast parts, concentrations are in the 

higher concentration ranges of observed values. The histogram 

in figure 2 shows the frequency distribution of arsenic values, 

and the substantial positive skew in the dataset indicates 

relatively low arsenic concentrations.

Comparison of Soil Arsenic Concentrations 

Across Geographic Regions

Boxplots illustrating the distribution of arsenic within 

each of the six geographic regions (fig. 3) show that the range 

and median arsenic values of the Copper Falls Formation 

and Green Bay Lobe regional datasets are quite similar 

and could possibly be placed into a single group (table 4). 

Cental Sands soils have a significantly lower range of arsenic 

concentrations, with the median value at the detection limit of 

1 mg/kg. This can be attributed to the sandy-textured soils that 

Detection limit = 1

Copper Falls 

Formation (CFF)

Green Bay Lobe 

(GBL)

Lake Michigan 

Lobe (LML)

Central Sands 

(CS)

Driftless Area 

(DA)

Des Moines Lobe 

(DML)

0

10

253 192 31 42 122 14

31 Number of values

EXPLANATION 

75th percentile

Median

25th percentile

Whisker, denotes maximum 

 value of dataset

Whisker, denotes minimum 

 value of dataset

Figure 3 

2

4

6

8

Arsenic concentration, in milligrams per kilogram

Figure 3. Statistical distribution of arsenic concentrations of surface soil samples in Wisconsin, categorized by the geographic regions 

shown in figure 1 and described in table 1, with outliers removed.
10 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

dominate the region. Lake Michigan Lobe and Des Moines 

Lobe soils have similar median concentrations, 2 mg/kg and 

2.2 mg/kg, respectively, and Driftless Area soils have the 

highest median value at 3.0 mg/kg (table 4). The Des Moines 

Lobe range of values is larger than both the Lake Michigan 

Lobe and Driftless Area ranges of observed concentrations, 

which are similar (fig. 3).

Wilcoxon rank-sum test results were used to determine 

whether arsenic concentrations from the geographic regions 

were statistically different (table 5). Results generally support 

what is suggested by the spatial patterns in figure 2 and 

apparent in the boxplot of figure 3. Arsenic concentrations in 

Central Sands soils were significantly different (probability 

(p) <0.05) from three of the other soil groups. Lake Michigan 

Lobe and Driftless Area soils have significantly different 

arsenic concentrations than Copper Falls Formation, Green 

Bay Lobe, and Central Sands soils. Des Moines Lobe soil 

arsenic concentrations are not significantly different from any 

geographic region, most likely because of the large range in 

observed values. On the basis of soil texture descriptions of 

the parent materials in the individual regions (table 1), it is 

probable that the presence of finer grained soils (higher clay 

content) in Lake Michigan Lobe, Driftless Area, and Des 

Moines Lobe accounts for the higher observed arsenic values. 

The dominance of sandy, coarse-textured soils in Central 

Sands accounts for the lowest concentrations of arsenic in 

the state. A combination of fine and coarse-grained soils in 

Copper Falls Formation and Green Bay Lobe results in arsenic 

concentrations intermediate to the other geographic region 

groupings.

Comparison of Soil Arsenic Concentrations in 

Soil Groups

The highest median concentration of arsenic in Wisconsin 

soils (3.0 mg/kg) is in somewhat poorly to excessively drained 

(WD) loess soils (fig. 4, table 4). Clay-rich soils have the next 

highest median arsenic with concentrations of 2.9 and 2.8 mg/

kg, followed by poorly to very poorly drained (PD) loamy 

Table 5. P-values from the Wilcoxon rank-sum test for comparing two sets of data on arsenic concentrations in Wisconsin 

surface soils. 

[* indicates the two data sets are significantly different; p<0.05; PD, poor to very poor drainage; WD, somewhat poor to excessive drainage; 

CFF, Copper Falls Formation; GBL, Green Bay Lobe; LML, Lake Michigan Lobe; CS, Central Sands; DA, Driftless Area; 

DML, Des Moines Lobe]

Soil group

WD, Loess PD, Sand WD, Sand PD, Clay WD, Clay PD, Loam WD, Loam Organic

PD, Loess 0.21 0.08 *0.00 0.62 0.54 0.30 0.35 0.30

WD, Loess *0.00 *0.00 0.85 0.92 0.90 *0.00 *0.00

PD, Sand 0.36 *0.04 0.66 *0.00 0.10 0.22

WD, Sand *0.00 *0.00 *0.00 *0.00 *0.00

PD, Clay 0.85 0.72 0.11 0.13

WD, Clay 0.59 0.18 0.15

PD, Loam *0.01 *0.01

WD, Loam 0.69

Geographic region

GBL LML CS DA DML

CFF 0.92 *0.00 *0.03 *0.00 0.55

GBL *0.00 0.12 *0.00 0.50

LML *0.00 0.92 0.32

CS *0.00 0.28

DA 0.52
Data on Other Trace Elements 11

soils with a median arsenic concentration of 2.6 mg/kg. 

PD loess soils have a lower median arsenic concentration than 

WD loess soils, but PD loamy soils have a higher median 

arsenic concentration than WD loamy soils. Sandy soils 

have a small range of low concentrations and median arsenic 

values below the 1-mg/kg detection limit. Organic soils have a 

median arsenic concentration of 1.6 mg/kg. It is apparent from 

this dataset that soil properties can have a significant influence 

on soil arsenic concentrations.

The Wilcoxon rank-sum test results for the soil groups 

(table 5) corroborate what is evident in figure 4. WD sandy 

soils, which are typical for the CS, have significantly different 

arsenic concentrations than all other soil groups except PD 

sandy soils (table 5). PD loams and WD loams also have 

significantly different arsenic concentrations from one another, 

as apparent in figure 4. Drainage category accounts for the 

differences in arsenic concentrations in that situation. 

Data on Other Trace Elements

In addition to arsenic, 16 other trace elements were 

analyzed in the soil samples collected. The geochemical 

data are presented herein, but in-depth discussion of the 

data for the remaining 16 trace elements is beyond the scope 

of this report. The data from these elements were treated 

similarly as the arsenic data described herein, and statistical 

characteristics were calculated with the same approach. 

However, the statistical analysis of the remaining trace 

elements did not consider the relationship to soil properties 

or geographic areas. Preliminary maps and histograms are in 

the appendix (figs. 1–2 through 1–17). In the case of the trace 

element molybdenum, there were too many non-detect values 

(91 percent; appendix, table 1–2) to calculate the summary 

statistics by using the available censored-data techniques. The 

raw data for all 17 trace elements sampled and analyzed for in 

this study are available in appendix table 1–1, and summary 

statistics are in appendix table 1–2.

Detection limit = 1

PD, LoessWD, LoessPD, Sand

WD, Sand

PD, Clay

WD, Clay

PD, Loam

WD, Loam

Organic

0

8

10

11 171 7 116 12 13 29 221 64

Figure 4.

29 Number of values

EXPLANATION 

75th percentile

Median

25th percentile

Whisker, denotes maximum 

 value of dataset

Whisker, denotes minimum 

 value of dataset

6

4

2

Arsenic concentration, in milligrams per kilogram

Figure 4. Statistical distribution of arsenic concentrations of surface soil samples in Wisconsin, categorized by soil characteristic 

group described in table 2, with outliers removed. (PD, poorly drained; WD, well drained)
12 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

Summary and Conclusions

Arsenic data from 664 surface soil samples taken 

across the state of Wisconsin were statistically analyzed 

to characterize baseline concentrations and determine if 

variations in these baseline concentrations exist as a result of 

physical and chemical soil properties or parent materials. In 

general, arsenic concentrations in Wisconsin surface soils with 

minimal anthropogenic influence are low. For the 654 samples 

collected for this study (excluding the 10 outliers), soil arsenic 

concentrations ranged from less than 1 to 8.3 mg/kg, with 

median, mean, and the 95-percent upper confidence limit for 

the mean at 1.8, 2.3, and 2.4 mg/kg, respectively. These data 

underscore the narrow distribution of background soil arsenic 

concentrations in Wisconsin surface soils. Higher-order 

statistical analysis yielded 90th-, 95th-, and 99th-percentile 

concentrations of 4.3, 4.8, and 5.9 mg/kg, respectively. Sandy 

glacial outwash soils, common in the central part of the State, 

have significantly lower arsenic concentrations than soils 

formed in most of the other parent materials represented in this 

report. Soil texture of the upper 6 in. of the soil profile also 

influenced the arsenic concentration, with finer grained soils 

typically having the highest observed range of concentrations. 

Drainage category did not show a distinct relation to median 

concentration in comparison of similar soil textures. Arsenic 

concentrations of surface soils in Wisconsin appear to be 

influenced more by parent material and soil texture than by 

drainage category. 

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14 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements
Appendix 1 15

Appendix 1
16 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

Arsenic Soil Sampling Project - Field Procedure Work Plan

April 17, 2007 

Project Summary / Objectives

Initial sampling of 38 sites was completed in the fall of 2006. Results and lessons learned from the pilot 

project have guided development of this plan for the rest of the project. An estimated 650 total sites will 

be sampled.

The end product will be a statistically verified range in Arsenic content for the top 6 inches of soil for 

each of the 9 soil groups identified below in each geographic area. Other potential soil groupings will 

also be explored, after the data is obtained and analyzed. Statistical analysis of the results will guide 

combinations of groups and geographic areas for practical presentation and use of the results.

After statistical analysis establishes significant soil groupings, a key, or chart, that identifies the properties 

used to place soils in each “Background Arsenic Content” (BAC) group will be developed. All soils in 

Wisconsin will be placed in one of the groups, and the data will be released in the form of an Excel 

spreadsheet or flat ASCII file. The possibility of posting BAC levels for every Wisconsin soil on Web Soil 

Survey (http://websoilsurvey.nrcs.usda.gov/app/) will be considered as the project proceeds.

In practical application, users will be able to utilize the BAC data by one of 2 methods:

1) If analysis of the data provides technical support for significant aggregation of soils based on 

general soil patterns or geographic regions such as MLRAs, a statewide BAC map will be created 

at a scale of about 1:750,000 or smaller. A responsible party can then use this map to identify the 

regional BAC for a specific contaminated site.

If anaylsis of the data does not support aggregation, a responsible party will identify the BAC for 

each soil mapped on a contaminated site, using the official USDA, NRCS detailed (1:12,000) 

soil survey maps. Then, using rules developed by DNR, the responsible party will determine the 

remediation level required.

2) In many cases, a responsible party will create a map of the contaminated site as part of the site 

investigation which includes a determinination of soil properties by a qualified site investigator. 

The investigator will identify the study group most closely representing the soil properties of the 

contaminated site, and use the BAC for that study group to determine the appropriate site specific 

concentration and the need for remediation.

Note: In certain cases, a responsible party may still choose to sample and test for As content to establish site 

specific BAC levels. In these cases, the BAC levels determined by this study will not be used.

Figure 1–1. Facsimile of draft field procedure work plan for Wisconsin arsenic sampling project.
Appendix 1 17

Field activities & data development

Step 1: Identify the soil series occurring in each of the following geographic areas. These areas represent 

the major surficial parent material sources in Wisconsin:

1) Copper Falls Formation

2) Green Bay Lobe

3) Lake Michigan Lobe

4) Central Sands

5) Driftless area

6) Des Moines Lobe

Note: There are other potential divisions, For example, MLRAs 90B and 104 include mostly older tills, not within the 

Copper Falls Fm. The south part of 95B along the Illinois border also includes mostly older tills, and the east part of 

95B, the rolling Kettle-Moraine area of Wisconsin, includes materials from the Lake Michigan Lobe.

Although the ages of materials in these areas vary, most soils are influenced by the more recent deposition of loess. 

It is estimated that the source areas and composition of the surficial soil materials in these “sub-areas” are similar, 

for the purposes of this study, to the larger region they are included in.

Area number 6, although small, is separated out because the source material is calcareous Des Moines Lobe 

till deposited from the SW, and is considerably different in properties which may affect Arsenic content from the 

adjacent Superior Lobe till, deposited from the NE.

Step 2: Within each geographic area, assign each soil to one of the following nine groups, based on 

surface soil parent material, surface soil texture, and drainage:

Loess or loess-derived silts

1) P and VP drainage

2) SP to E drainage

Figure 1–1. Facsimile of draft field procedure work plan for Wisconsin arsenic sampling project.—Continued
18 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

Other mineral parent materials

s & ls surface textures

3) P and VP drainage

4) SP to E drainage

sc, c, cl, sicl, & sic surface textures

5) P and VP drainage

6) SP to E drainage

si, sil, l, sl, & scl surface textures

7) P and VP drainage

8) SP to E drainage

Organics

9) all

Step 3: Identify high-acreage indicator soils to represent all soils in each group. These soils will be 

targeted for sampling. In general, we will attempt to sample at least two soils for each group that occurs 

in each geographic area. The remaining samples will be chosen to provide a roughly proportional 

representation of the extent of the geographic area and each soil group in the area. For 650 samples, 

each sample represents about 84 square miles. The density of sampling in areas 3, 4, and 6 may be 

somewhat higher than in the other areas.

Notes: Within each group, we will attempt to ensure that all Suborders in the group are represented, and 

that the full extent of the geographic area is represented. We will attempt to sample at least 3 sites in 

every county.

It is anticipated that statistical analysis of the results may permit conclusions based on soil properties 

other than those used to identify the original soil groups. The statistician will also provide guidelines for 

determining when to disregard a sample with especially high Arsenic content.

Nine groups x 6 areas = 54 total soil groups to sample. If we collect 650 samples, this is an average 

of about 12 samples per group. However, the actual number of samples collected for any particular 

group will vary, because the number of samples should be roughly proportional to the extent of that 

group in the area. We anticipate that statistical analysis of the results will permit us to combine some 

geographic areas and soil groups, so that a larger sample size will ultimately be used to support results 

and conclusions.

Field Equipment

Auger, Munsell color book, Clinometer, Field data sheets, Aerial photography, Handheld or tablet GPS 

unit, Sample bags (SLOH), stainless steel spade, disposable gloves (incomplete list).

Soil Classification Guidelines 

To achieve the purposes of this study, we must be able to correlate laboratory results for content of 

Arsenic and other contaminants from specific sampled pedons to similar soils throughout each geographic 

region.

Many older soil surveys in Wisconsin were completed using taxonomic concepts, series concepts, and 

mapping procedures that do not meet current standards. Map units commonly include, as dominant 

components, several similar soil series, not just the named series. For this reason, it is not reasonable 

or necessary to require that a sampled pedon match the series of the mapped major component(s). 

Figure 1–1. Facsimile of draft field procedure work plan for Wisconsin arsenic sampling project.—Continued
Appendix 1 19

To ensure that we can draw scientifically valid conclusions, it is essential only that a sampled pedon 

represents a major component of the map unit, as it is mapped in the general area.

If the pedon meets both of the following criteria, proceed. If not, move to a different location on the map 

unit, or select a new site:

1) The sampled pedon must classify within the same “sampling group” (step 2, above) as a major 

component of the map unit.

2) The sampled pedon must, in the best professional judgement of the field soil scientists, be 

representative of the soil properties of a major component of the map unit.

For purposes of this determination, soil scientists should consider soil properties of the components of the 

map unit, not just for the individual map unit sampled, but for the entire range of soil properties within all 

delineations of the map unit throughout its extent as originally mapped and correlated. It is recognized that 

soil scientists will often have to make this judgement based on incomplete data or knowledge, and that this 

judgement, while imperfect, is the best judgement possible, given the current status of mapping and soil 

science knowledge.

A pedon should be considered “representative” if the pedon properties are similar to a documented or 

presumed dominant component of the map unit. As described above, dominant components should be 

estimated using the best available data and professional knowledge. They do not have to be named or 

correlated map unit components.

Similar, for purposes of this study, refers to properties that may influence content and retention of Arsenic 

and similar contaminants: such as texture, parent material, drainage, organic matter, and pH. For purposes 

of determining similarity, only near-surface properties, or subsurface properties, such as restrictive layers, 

that influence near-surface properties, must be considered.

If the pedon sampled does not meet the concept of the same series as a major map unit component, 

make a note on the field sheet describing why it is judged that the sampled pedon is representative of a 

map unit component, as mapped in the survey area.

Field Procedures

Sample locations will not be pre-selected. Instead samplers will choose sampling sites following the site 

selection guidelines below.

•	Sample on public lands where possible. Or, obtain landowner permission to sample following 

standard NRCS soil survey procedures. Provide an informational handout to landowners, as 

needed (see appendix).

•	Complete a brief profile description and classify the soil to the series level. Observe to the depth 

necessary to classify to the series level (usually 80”). If it is difficult or impossible to observe to the 

required depth, a shallower core is acceptable if:

1) The description and classification is still adequate to meet the purposes and intent of the “Soil 

Classification Guidelines” section above and, with reasonable assumptions or estimates, the 

pedon can be classified to the series level; OR

2) It is reasonable to estimate or project the properties of the lower part of the pedon to 80”, 

(eg: stones prevent augering below 50”, and the sampled pedon shows a calcareous, loamy till C 

horizon from 42-50”, and the sample is from a soil and area where sampling, mapping, and road cut 

Figure 1–1. Facsimile of draft field procedure work plan for Wisconsin arsenic sampling project.—Continued
20 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

observations indicate a thick stony, calcareous, loamy till is the expected soil parent material). If 

properties are estimated or projected to 80”, describe the properties on the field sheet, and 

note that they were not directly observed, but were projected.

•	Record GPS coordinates for each sample site, using a handheld or tablet GPS unit. Datum: NAD83. 

Coordinate system: Lat-Long. Elevation data is not needed. Complete an NRCS data sheet, 

including site information and the profile description (see Appendix A). Assign standard NRCS sample 

numbers.

•	Move a few inches from the sample hole, or otherwise ensure that the only tool that touches the 

sample is the stainless steel spade. Wearing laboratory-grade disposable gloves and using the 

stainless steel spade, collect a slice of the upper 6 inches of the soil, discard large coarse fragments 

and collect at least a 1.5 cup sample representative of the slice. If the surface is undisturbed, 

remove any undecomposed organic material (SPM (Oi or Oe) horizon), before collecting the sample. 

Put the sample in a laboratory grade sample bag. You do not need to mix the sample. Make sure 

the zip-loc top is closed, and expel excess air.

•	Fold over the top of the bag to minimize the chance of moisture leaking out of the bag, and doublebag the sample in a second laboratory-grade sample bag.

•	Write the sample number, in ink, on a 3x5 note card (heavy paper, less likely to disintegrate), and 

insert the note card in a small plastic zip-loc baggie. Then include this note card inside the 

second sample bag with the number visible from the outside. A tag is not needed. Include only the 

sample number inside the second bag. Do not include a copy of the Field Data Sheet. There 

should be no clues that permit the laboratory staff to distinguish between the regular samples and 

the blind duplicate samples.

•	Wipe down and water rinse the sampling equipment between sample sites. Discard disposable 

gloves after every sample.

•	Take pictures of the core and sample site if a camera and time is available. This is not required. 

•	Keep track of: 1) hours worked on the Arsenic project, 2) miles driven, and 3) days of per diem 

claimed. At the end of every pay period, populate these 3 figures in the shared spreadsheet Jesse 

maintains.

•	At the end of each day, update samples obtained on the shared spreadsheet Jesse maintains.

Blind Duplicate Procedures -

•	At 10 percent of the sites, collect a blind duplicate. These can be collected at random intervals. 

Assign a unique sample number. Note 2 numbers on a Field Data Sheet: “Blind Duplicate sample 

number: ____”, and ”This duplicate corresponds to sample number ____”. No other data is 

needed for a blind duplicate. The sample number will link the blind duplicate to the data for the 

corresponding main sample number.

•	Ensure that both samples are essentially identical duplicates of each other, so that you would expect 

laboratory tests for As content, particle size, pH, etc to be the same. You can do that by taking 2 

immediately adjacent slices, or by carefully splitting one large slice, or by thoroughly mixing a larger 

sample in a sample bag with your gloved hand and then dividing the sample in two.

•	Include only the blind duplicate sample number in the second bag, as described above. These 

samples will serve as QA/QC samples to check and evaluate laboratory procedures.

•	Enter the blind duplicate sample number and the sample number of the main sample on the shared 

spreadsheet Jesse maintains.

Figure 1–1. Facsimile of draft field procedure work plan for Wisconsin arsenic sampling project.—Continued
Appendix 1 21

Site Selection Guidelines

•	 Sample in woodlots, permanent pasture, or other relatively undisturbed areas, at least 20 feet 

away from fencelines.

•	 Do not sample within 1 mile of any other Arsenic study sample site.

•	 Do not sample within 5 miles of any other sample from the same soil group.

•	 Do not sample within 100 feet of existing or known historical construction sites or disturbed areas, 

such as roads, dumps, pits, pipelines, or homesites.

•	 Do not sample within 300 feet of areas of suspected or known contamination, such as:

o areas listed by the DNR Bureau for Remediation and Redevelopment Tracking System 

(BRRTS): http://botw.dnr.state.wi.us/botw/Welcome.do

o current or old orchards or fields used to grow vegetable crops

o cattle dipping sites

o wood preservative activities

o Poultry or swine manure spreading areas

o land spreading of sewage waste or paper mill sludge

o areas where grasshopper bait may have had historical use

Figure 1–1. Facsimile of draft field procedure work plan for Wisconsin arsenic sampling project.—Continued
22 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

Arsenic Sampling Project - Field Data Sheet (DRAFT 4-10-07 – Appendix A)

Date: __________ Time: _________ Soil Scientist: _______________________________________

Site Location: County____________________ Twp_______ Range_______ Section ____________

Field GPS (lat-long): ____________________________________________________ Air temp: _____

Slope (%):_____ Aspect (degrees): _____ Soil moisture: ___________ Weather: ______________

Map unit symbol and name: _________________________________________________________

Land use / vegetative cover: _________________________________________________________

Est distance (feet) to disturbed area: __________________________________________________

Taxclass: _________________________________________________________________________

Geographic area number: (1-6)_________ Soil group number: (1-9) _________________________

Sample number(s):_____________________________________ Series: _____________________ 

Note major horizons and parent material breaks. Estimate percent sand and clay for the surface and a 

representative subsoil horizon and note in the “texture” column, eg: 15s, 22c. Circle the horizons sampled.

Horizon depths color texture structure redox frags CO3/

pH

parent 

material

NOTES:___________________________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

________________________________________________________

Figure 1–1. Facsimile of draft field procedure work plan for Wisconsin arsenic sampling project.—Continued
Appendix 1 23

April 17, 2007

Dear Landowner,

The Wisconsin Department of Health and Family Services and Wisconsin Department of Natural 

Resources are conducting a scientific study to determine natural background levels of certain trace 

elements in Wisconsin soils. Soil samples from over 600 relatively undisturbed sites will be evaluated to 

establish target levels for cleanup of known contaminated sites.

The purpose of this study is not to identify contaminated sites, but simply to provide supporting 

background data to guide cleanup of known contaminated sites. Samples are being collected from 

indicator soils throughout Wisconsin. Soil scientists auger 3 inch diameter holes by hand, take notes, 

record the location, and collect pint sized soil samples. They will check with each landowner by phone or 

in person before walking on the land, to obtain permission to sample the soils.

This is a cooperative effort, completed in partnership with the United States Geological Survey, the USDA 

Natural Resources Conservation Service, and the Wisconsin Geological and Natural History Survey.

Please contact one of the following persons familiar with this study, if you have any questions or concerns.

Thank you,

David Hall, USGS Ed Lynch, DNR Chuck Warzecha, DHFS

608-821-3875 608-266-3084 608-267-3732

dwhall@usgs.gov edward.lynch@wisconsin.gov warzecj@dhfs.state.wi.us

Figure 1–1. Facsimile of draft field procedure work plan for Wisconsin arsenic sampling project.—Continued
24 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

92° 90° 88°

46°30'

45°

43°30'

42°

<5,000

5,000 to 10,000

>10,000 to 15,000

>15,000 to 30,000

>30,000

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

EXPLANATION

Aluminum concentration (mg/kg)

0 25 50 MILES

0 50 KILOMETERS 25

Number of samples

Aluminum concentration (mg/kg)

0

0 25,000 50,000

40

80

160

120

Appendix figure 1-2. 

Lake Superior

Lake Michigan

ILLINOIS

WISCONSIN

MICHIGAN

MINNESOTA

IOWA

Figure 1–2. Spatial distribution of aluminum concentrations of surface soil samples in Wisconsin. 

The histogram in the figure gives the frequency distribution of the aluminum concentrations. The data 

displayed in both the map and the histogram include outliers that were removed prior to statistical 

analysis and are shown on the figure as red squares.
Appendix 1 25

92° 90° 88°

46°30'

45°

43°30'

42°

<70

70 to 160

>160 to 250

>250 to 380

>380

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

EXPLANATION

Barium concentration (mg/kg)

0 25 50 MILES

0 50 KILOMETERS 25

Number of samples

Barium concentration (mg/kg)

0 160 330 500 660

40

80

0

160

120

Appendix figure 1-3. 

MINNESOTA

MICHIGAN

ILLINOIS

Lake Michigan

Lake Superior

IOWA

WISCONSIN

Figure 1–3. Spatial distribution of barium concentrations of surface soil samples in Wisconsin. The 

histogram in the figure gives the frequency distribution of the barium concentrations. The data displayed 

in both the map and the histogram include outliers that were removed prior to statistical analysis and are 

shown on the figure as red squares.
26 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

92° 90° 88°

46°30'

45°

43°30'

42°

<2,500

2,500 to 5,000

>5,000 to 10,000

>10,000 to 15,000

>15,000

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

EXPLANATION

Calcium concentration (mg/kg)

0 25 50 MILES

0 50 KILOMETERS 25

Number of samples

Calcium concentration (mg/kg)

0 30,000 60,000 110,000

200

0

400

Appendix figure 1-4. 

Lake Superior

Lake Michigan

ILLINOIS

MICHIGAN

MINNESOTA

IOWA

WISCONSIN

Figure 1–4. Spatial distribution of calcium concentrations of surface soil samples in Wisconsin. The 

histogram in the figure gives the frequency distribution of the calcium concentrations. The data displayed 

in both the map and the histogram include outliers that were removed prior to statistical analysis and are 

shown on the figure as red squares.
Appendix 1 27

92° 90° 88°

46°30'

45°

43°30'

42°

<0.1

0.1 to 0.4

>0.4 to 0.7

>0.7 to 1.1

>1.1

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

EXPLANATION

Cadmium concentration (mg/kg)

0 25 50 MILES

0 50 KILOMETERS 25

Number of samples

Cadmium concentration (mg/kg)

1.2 2.4 3.6 0

0

50

150

100

200

250

Appendix figure 1-5. 

Lake Superior

Lake Michigan

ILLINOIS

MICHIGAN

MINNESOTA

IOWA

WISCONSIN

Figure 1–5. Spatial distribution of cadmium concentrations of surface soil samples in Wisconsin. 

The histogram in the figure gives the frequency distribution of the cadmium concentrations. The data 

displayed in both the map and the histogram include outliers that were removed prior to statistical 

analysis and are shown on the figure as red squares.
28 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

92° 90° 88°

46°30'

45°

43°30'

42°

<4.0

4.0 to 10

>10 to 18

>18 to 25

>25

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

EXPLANATION

Cobalt concentration (mg/kg)

0 25 50 MILES

0 50 KILOMETERS 25

Number of samples

Cobalt concentration (mg/kg)

12 30 48 66 0

0

50

100

150

Appendix figure 1-6. 

Lake Superior

Lake Michigan

ILLINOIS

MICHIGAN

MINNESOTA

IOWA

WISCONSIN

Figure 1–6. Spatial distribution of cobalt concentrations of surface soil samples in Wisconsin. The 

histogram in the figure gives the frequency distribution of the cobalt concentrations. The data displayed 

in both the map and the histogram include outliers that were removed prior to statistical analysis and are 

shown on the figure as red squares.
Appendix 1 29

92° 90° 88°

46°30'

45°

43°30'

42°

<8.0

8.0 to 15

>15 to 25

>25 to 45

>45

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

EXPLANATION

Chromium concentration (mg/kg)

0 25 50 MILES

0 50 KILOMETERS 25

Number of samples

Chromium concentration (mg/kg)

0

40

0

80

120

24 48 72

Appendix figure 1-7.

Lake Superior

Lake Michigan

ILLINOIS

MICHIGAN

MINNESOTA

IOWA

WISCONSIN

Figure 1–7. Spatial distribution of chromium concentrations of surface soil samples in Wisconsin. 

The histogram in the figure gives the frequency distribution of the chromium concentrations. The data 

displayed in both the map and the histogram include outliers that were removed prior to statistical 

analysis and are shown on the figure as red squares.
30 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

92° 90° 88°

46°30'

45°

43°30'

42°

<5.0

5.0 to 10

>10 to 20

>20 to 36

>36

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

EXPLANATION

Copper concentration (mg/kg)

0 25 50 MILES

0 50 KILOMETERS 25

Copper concentration (mg/kg) 20 40 200 220 0

0

50

150

100

250

200

Number of samples

Appendix figure 1-8.

Lake Superior

Lake Michigan

ILLINOIS

MICHIGAN

MINNESOTA

IOWA

WISCONSIN

Figure 1–8. Spatial distribution of copper concentrations of surface soil samples in Wisconsin. The 

histogram in the figure gives the frequency distribution of the copper concentrations. The data displayed 

in both the map and the histogram include outliers that were removed prior to statistical analysis and are 

shown on the figure as red squares
Appendix 1 31

92° 90° 88°

46°30'

45°

43°30'

42°

<8,000

8,000 to 17,000

>17,000 to 25,000

>25,000 to 40,000

>40,000

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

EXPLANATION

Iron concentration (mg/kg)

0 25 50 MILES

0 50 KILOMETERS 25

Number of samples

Iron concentration (mg/kg)

0 30,000 60,000 90,000 0

50

100

150

Appendix figure 1-9. 

Lake Superior

Lake Michigan

ILLINOIS

MICHIGAN

MINNESOTA

IOWA

WISCONSIN

Figure 1–9. Spatial distribution of iron concentrations of surface soil samples in Wisconsin. The 

histogram in the figure gives the frequency distribution of the iron concentrations. The data displayed in 

both the map and the histogram include outliers that were removed prior to statistical analysis and are 

shown on the figure as red squares.
32 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

92° 90° 88°

46°30'

45°

43°30'

42°

<1,500

1,500 to 3,000

>3,000 to 5,000

>5,000 to 8,500

>8,500

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

EXPLANATION

Magnesium concentration (mg/kg)

0 25 50 MILES

0 50 KILOMETERS 25

0 9,000 18,000 27,000

50

0

150

100

250

200

Magnesium concentration (mg/kg)

Number of samples

Appendix figure 1-10.

Lake Superior

Lake Michigan

ILLINOIS

MICHIGAN

MINNESOTA

IOWA

WISCONSIN

Figure 1–10. Spatial distribution of magnesium concentrations of surface soil samples in Wisconsin. 

The histogram in the figure gives the frequency distribution of the magnesium concentrations. The 

data displayed in both the map and the histogram include outliers that were removed prior to statistical 

analysis and are shown on the figure as red squares.
Appendix 1 33

92° 90° 88°0'0"W

46°30'

45°

43°30'

42°

<500

500 to 1,000

>1,000 to 2,000

>2,000 to 3,000

>3,000

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

EXPLANATION

Manganese concentration (mg/kg)

0 25 50 MILES

0 50 KILOMETERS 25

Number of samples

4,5000 9,000 13,500 0

100

200

300

Manganese concentration (mg/kg)

Appendix figure 1-11. 

Lake Superior

Lake Michigan

ILLINOIS

MICHIGAN

MINNESOTA

IOWA

WISCONSIN

Figure 1–11. Spatial distribution of manganese concentrations of surface soil samples in Wisconsin. 

The histogram in the figure gives the frequency distribution of the manganese concentrations. The 

data displayed in both the map and the histogram include outliers that were removed prior to statistical 

analysis and are shown on the figure as red squares.
34 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

92° 90° 88°

46°30'

45°

43°30'

42°

MINNESOTA

MICHIGAN

ILLINOIS

Lake Michigan

Lake Superior

<1.0

1.0 to 2.0

>2.0 to 5.0

>5.0

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

EXPLANATION

Molybdenum concentration (mg/kg)

0 25 50 MILES

0 50 KILOMETERS 25

Number of samples

0

200

0

400

600

3 6 9

Molybdenum concentration (mg/kg)

Appendix figure 1-12. 

IOWA

WISCONSIN

Figure 1–12. Spatial distribution of molybdenum (statistical analysis not done for this element) 

concentrations of surface soil samples in Wisconsin. The histogram in the figure gives the frequency 

distribution of the molybdenum concentrations. 
Appendix 1 35

92° 90° 88°

46°30'

45°

43°30'

42°

<6.0

6.0 to 12

>12 to 18

>18 to 32

>32

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

EXPLANATION

Nickel concentration (mg/kg)

0 25 50 MILES

0 50 KILOMETERS 25

Nickel concentration (mg/kg) 24 32 40 0

40

80

80 16

Number of samples

Appendix figure 1-13. 

Lake Superior

Lake Michigan

ILLINOIS

MICHIGAN

MINNESOTA

IOWA

WISCONSIN

Figure 1–13. Spatial distribution of nickel concentrations of surface soil samples in Wisconsin. The 

histogram in the figure gives the frequency distribution of the nickel concentrations. The data displayed 

in both the map and the histogram include outliers that were removed prior to statistical analysis and are 

shown on the figure as red squares.
36 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

92° 90° 88°

46°30'

45°

43°30'

42°

<10

10 to 25

>25 to 40

>40 to 55

>55

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

EXPLANATION

Lead concentration (mg/kg)

0 25 50 MILES

0 50 KILOMETERS 25

Lead concentration (mg/kg)

Number of samples

0 70 140 210 270 340 0

100

50

200

250

150

Appendix figure 1-14. 

Lake Superior

Lake Michigan

ILLINOIS

MICHIGAN

MINNESOTA

IOWA

WISCONSIN

Figure 1–14. Spatial distribution of lead concentrations of surface soil samples in Wisconsin. The 

histogram in the figure gives the frequency distribution of the lead concentrations. The data displayed in 

both the map and the histogram include outliers that were removed prior to statistical analysis and are 

shown on the figure as red squares.
Appendix 1 37

92° 90° 88°

46°30'

45°

43°30'

42°

<10

10 to 20

>20 to 35

>35 to 60

>60

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

EXPLANATION

Strontium concentration (mg/kg)

0 25 50 MILES

0 50 KILOMETERS 25

Number of samples

Strontium concentration (mg/kg)

0 70 140 210 270 340 0

50

150

100

250

200

Appendix figure 1-15. 

Lake Superior

Lake Michigan

ILLINOIS

MICHIGAN

MINNESOTA

IOWA

WISCONSIN

Figure 1–15. Spatial distribution of strontium concentrations of surface soil samples in Wisconsin. 

The histogram in the figure gives the frequency distribution of the strontium concentrations. The data 

displayed in both the map and the histogram include outliers that were removed prior to statistical 

analysis and are shown on the figure as red squares.
38 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

92° 90° 88°

46°30'

45°

43°30'

42°

<20

20 to 40

>40 to 60

>60 to 90

>90

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

EXPLANATION

Vanadium concentration (mg/kg)

0 25 50 MILES

0 50 KILOMETERS 25

Number of samples

Vanadium concentration (mg/kg)

14070 210 270 340 0

0

50

100

150

Appendix figure 1-16. 

Lake Superior

Lake Michigan

ILLINOIS

MICHIGAN

MINNESOTA

IOWA

WISCONSIN

Figures 1–16. Spatial distribution of vanadium concentrations of surface soil samples in Wisconsin. 

The histogram in the figure gives the frequency distribution of the vanadium concentrations. The data 

displayed in both the map and the histogram include outliers that were removed prior to statistical 

analysis and are shown on the figure as red squares.
Appendix 1 39

92° 90° 88°

46°30'

45°

43°30'

42°

<30

30 to 60

>60 to 90

>90 to 155

>155

Geographic region

Copper Falls Formation

Green Bay Lobe

Lake Michigan Lobe

Central Sands

Driftless Area

Des Moines Lobe

EXPLANATION

Zinc concentration (mg/kg)

0 25 50 MILES

0 50 KILOMETERS 25

Number of samples

Zinc concentration (mg/kg)

0 70 140 210 340270

100

150

50

0

200

Appendix figure 1-17. 

Lake Superior

Lake Michigan

ILLINOIS

IOWA

MICHIGAN

MINNESOTA

WISCONSIN

Figure 1–17. Spatial distribution of zinc concentrations of surface soil samples in Wisconsin. The 

histogram in the figure gives the frequency distribution of the zinc concentrations. The data displayed in 

both the map and the histogram include outliers that were removed prior to statistical analysis and are 

shown on the figure as red squares.
40 Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements

Table 1–1. Complete dataset for arsenic baseline study.

This table, in Microsoft Excel format, is available for downloading at http://pubs.usgs.gov/sir/2011/5202/
Table 1–2. Statistical summary, including 95-percent upper confidence limit of the mean (95% UCL), of trace element data from surface soiWisconsin. Summaries are for the entire dataset after outliers were removed. (*For the element molybdenum, the percentage of non-detect for the censored-data methods that were used in this report. None of the summary statistics were calculated for this element.) [Statistics are for concentrations in milligrams per kilogram]

Trace 

element

Number 

of samples 

Non-detects 

(%)

Minimum 

detected 

value

Maximum 

detected 

value

Median Mean 95% UCL of the mean 90th percentile 95th percentile 

Aluminum 662 0 610 28,721 8,282 9,147 9,479 15,575 17,398 Arsenic 654 32.3 1.0 8.3 1.8 2.3 2.4 4.3 4.8 Barium 658 0 3.53 364 92.0 101 105 181 204 Calcium 607 0 22.9 14,536 1,931 2,831 3,025 6,445 7,470 Cadmium 642 38 0.10 1.07 0.15 0.23 0.25 0.49 0.57 Cobalt 661 1.5 0.51 22.0 6.34 6.61 6.87 11.70 13.2 Chromium 659 0 0.95 43.5 12.5 13.7 14.2 22.5 26.2 Copper 655 0.5 0.50 35.4 6.52 8.38 8.78 16.5 18.8 Iron 659 0 442 34,314 11,800 11,976 12,377 19,638 21,810 Magnesium 633 0 66.3 8,290 1,769 2,103 2,204 4,019 4,562 Manganese 650 0 2.53 2,937 465 610 647 1,308 1,506 Molybdenum* 664 91 1.0 8.5 — — — — — Nickel 663 0.8 0.53 30.8 8.9 9.8 10.2 17.4 19.6 Lead 648 0 1.48 51.6 11.3 13.5 14.1 25.0 28.3 Strontium 653 0 0.50 54.5 11.5 13.6 14.2 26.1 29.6 Vanadium 661 0 1.76 85.0 26.1 27.4 28.2 44.9 49.9 Zinc 655 0 2.56 150 40.4 42.8 44.3 75.2 84.3 

Stensvold, K.A.—Distribution and Variation of Arsenic in Wisconsin Surface Soils, With Data on Other Trace Elements—Scientific Investigations Report 2011–5202