U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2020–5002

Prepared for the Mason-Griffith Founders Chapter of Trout Unlimited 

in cooperation with Lovells Township, Michigan

Evaluation of Legacy and Emerging Organic Chemicals using 

Passive Sampling Devices on the North Branch Au Sable 

River near Lovells, Michigan, June 2018
Cover. The polar organic chemical integrative sampler (POCIS) and semipermeable membrane 

device (SPMD), and replicate, deployed at the North Branch Au Sable River at The Ford Road near 

Lovells, Michigan (04135765).
Evaluation of Legacy and Emerging Organic 

Chemicals using Passive Sampling Devices 

on the North Branch Au Sable River near 

Lovells, Michigan, June 2018

By Angela K. Brennan and David A. Alvarez

Prepared for the Mason-Griffith Founders Chapter of Trout Unlimited 

in cooperation with Lovells Township, Michigan

Scientific Investigations Report 2020–5002

U.S. Department of the Interior

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

DAVID BERNHARDT, Secretary

U.S. Geological Survey

James F. Reilly II, Director

U.S. Geological Survey, Reston, Virginia: 2020

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Suggested citation:

Brennan, A.K., and Alvarez, D.A., 2020, Evaluation of legacy and emerging organic chemicals using passive sampling 

devices on the North Branch Au Sable River near Lovells, Michigan, June 2018: U.S. Geological Survey Scientific 

Investigations Report 2020–5002, 21 p., https://doi.org/ 10.3133/ sir20205002.

ISSN 2328-0328 (online)
iii

Contents

Acknowledgments........................................................................................................................................vi

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

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

Purpose and Scope ..............................................................................................................................3

Background............................................................................................................................................3

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

Field Methods........................................................................................................................................3

Laboratory Methods .............................................................................................................................6

Quality Control and Quality Assurance .............................................................................................6

Results and Evaluation of Legacy and Emerging Organic Chemicals ..................................................7

Legacy Pesticides, Total Polychlorinated Biphenyls, and Polybrominated 

Diphenyl Ethers ........................................................................................................................7

Legacy Pesticides ........................................................................................................................7

Polychlorinated Biphenyls .......................................................................................................17

Polybrominated Diphenyl Ethers .............................................................................................17

Polycyclic Aromatic Hydrocarbons .................................................................................................17

Current-Use Pesticides ......................................................................................................................17

Organic Chemical Detections above the Method Detection Limit .............................................17

Quality-Control and Quality-Assurance Results ............................................................................18

Evaluation of Organic Chemicals .....................................................................................................18

Summary........................................................................................................................................................18

References Cited..........................................................................................................................................19

Figures

1. Map showing North Branch Au Sable River passive sampler monitoring and 

streamgage locations near Lovells, Michigan, 2018 ...............................................................2

Tables

1. Passive sampler deployment and retrieval site conditions, North Branch 

Au Sable River, 2018 .....................................................................................................................4

2. Benchmark standards for those organic chemicals detected above the method 

quantitation limit ...........................................................................................................................8

3. Legacy pesticides, total polychlorinated biphenyls, and polybrominated 

diphenyl ether residues sampled by semi-permeable membrane devices 

reported as time-weighted average water concentrations in units of picograms 

per liter .........................................................................................................................................11

4. Polycyclic aromatic hydrocarbons sampled by semi-permeable membrane 

devices reported as time-weighted average water concentrations in units of 

picograms per liter .....................................................................................................................14

5. Current-use pesticides sampled by polar organic chemical integrative sampler 

reported as time-weighted average water concentrations in units of picograms 

per liter .........................................................................................................................................16
iv

Conversion Factors

U.S. customary units to International System of Units

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

acre 0.004047 square kilometer (km2)

Volume

ounce, fluid (fl. oz) 0.02957 liter (L)

pint (pt) 0.4732 liter (L)

quart (qt) 0.9464 liter (L)

gallon (gal) 3.785 liter (L)

cubic inch (in3) 0.01639 liter (L)

Mass

ounce, avoirdupois (oz) 28.35 gram (g)

pound, avoirdupois (lb) 0.4536 kilogram (kg)

picogram (pg) 1.0e-6 microgram (mg)

microgram (mg) 1.0e-6 gram (g)

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

 °F = (1.8 × °C) + 32.

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

 °C = (°F – 32) / 1.8.

Supplemental Information

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm 

at 25 °C).

Concentrations of chemical constituents in water are given in either micrograms per liter (μg/L) 

or picograms per liter (pg/L).
v

Abbreviations

CERC Columbia Environmental Research Center

DDD dichlorodiphenyldichloroethane

DDE dichlorodiphenyldichloroethylene

DDT dichlorodiphenyltrichloroethane

EGLE Michigan Department of Environment, Great Lakes, and Energy

EPA U.S. Environmental Protection Agency

EROD ethoxyresorufin O-deethylase

GLRI CEC Great Lakes Restoration Initiative Contaminants of Emerging Concern

Kow water partition coefficient

LRL laboratory reporting level

MDL method detection limit

MDNR Michigan Department of Natural Resources

MQL method quantitation limit

NWQL National Water Quality Laboratory

PAH polycyclic aromatic hydrocarbon

PBDE polybrominated diphenyl ether

PCB polychlorinated biphenyl

POCIS polar organic chemical integrative sampler

SPMD semipermeable membrane device

TWA time-weighted average

USGS U.S. Geological Survey
vi

Acknowledgments

Special thanks to Lovells Township, Michigan, for their support of this research on the North 

Branch Au Sable River and serving as the cooperator for this project. Without the commitment 

of the Mason-Griffith Founders Chapter of Trout Unlimited, this study would not have been possible. Thank you Mason-Griffith Founders Chapter of Trout Unlimited for your desire to obtain 

current data on the presence of organic chemicals in the North Branch Au Sable River and for 

your ongoing efforts to preserve and protect the Au Sable River.
Evaluation of Legacy and Emerging Organic Chemicals 

using Passive Sampling Devices on the North Branch 

Au Sable River near Lovells, Michigan, June 2018

By Angela K. Brennan and David A. Alvarez

Abstract

The North Branch Au Sable River, located in the northern lower peninsula of Michigan near Lovells, Michigan, 

has historically been known for its brook trout (Salvelinus 

fontinalis) and its status as a blue ribbon trout stream; however, within the past few decades, there has been a decline in 

fish population. The objectives of this study were to assess if 

concentrations of organic chemicals were present in quantities 

in the North Branch Au Sable River that may potentially harm 

aquatic species and to establish current baseline concentrations 

of organic chemicals against which future data can be compared. Passive sampling technology was used to collect information on the concentration, occurrence, transport, and fate 

of organic chemicals; these samplers absorb dissolved organic 

chemicals in the river over several weeks, as the timing and 

intensity of pesticide applications and the frequency of storm 

events and irrigation can cause fluctuations in organic chemical loading to surface waters. The chemical classes investigated as part of this study included pesticides (both legacy 

[organochlorine] and current use), polychlorinated biphenyls, 

polybrominated diphenyl ethers (PBDEs), and polycyclic 

aromatic hydrocarbons (PAHs).

Passive samplers, including semipermeable membrane 

devices and polar organic chemical integrative samplers, were 

deployed at four locations along the North Branch Au Sable 

River, near Lovells, Mich., in June 2018 for a total of 28 days. 

Several organic chemicals were detected in the North Branch 

Au Sable River at low concentrations. Organic chemicals 

were detected at every sampling location on the North Branch 

Au Sable River; however, not all chemicals were detected at 

every location. The highest number of organic chemicals were 

detected at the most downstream sampling site (North Branch 

Au Sable River at Kellogg's Bridge), and the lowest number 

of organic chemicals were detected at the next site upstream 

(North Branch Au Sable River at Twin Bridge Road). The 

organic contaminants most frequently detected at all sampling 

locations include the legacy pesticides pentachloroanisole, 

trans-chlordane, p,p'-dichlorodiphenyldichloroethylene, and 

p,p'-dichlorodiphenyltrichloroethane; the PBDE PBDE-28; 

and the PAHs 2-methylphenanthrene and perylene.

Organic chemical concentrations detected on the North 

Branch Au Sable River were below almost all water-quality 

benchmarks included in this report. However, low concentrations 

of organic chemicals may still pose a risk to aquatic organisms and 

throughout the trophic hierarchy because of low-dose additive and 

synergistic mixture effects, transgenerational effects, and a lack of 

established water-quality benchmarks for many organic chemicals. This report provides data on the current (2018) state of the 

North Branch Au Sable River and provided a baseline of organic 

contaminant data against which future data on the North Branch 

Au Sable River can be evaluated.

Introduction

The Au Sable River, located in the northern lower peninsula of Michigan, has historically been known for its brook 

trout (Salvelinus fontinalis) and its status as a blue ribbon trout 

stream (Michigan Department of Natural Resources [MDNR], 

Fisheries Division, 1987). Within the past few decades the 

MDNR, local anglers, and environmental groups have noted 

a decline in fish populations on the North Branch Au Sable 

River near Lovells, Michigan (fig. 1) (MDNR, 2018). More 

recently, there has been increased interest in determining 

whether this observed fish decline may be related to legacy or 

emerging organic chemicals entering the river from sources 

within the watershed. Potential chemical sources may include, 

but are not limited to, golf courses, private residences, gas and 

oil production wells, atmospheric contribution, and a nearby 

Department of Defense facility. The timing and intensity of 

pesticide applications and the frequency of storm events and 

irrigation can cause fluctuations in organic chemical loading 

to surface waters. In addition to agricultural use of pesticides, 

organic chemicals also come from herbicides, insecticides, 

coal tar and asphalt, manufacturing, fire retardants, combustion, fragrances, flavors, and more (Baldwin and others, 2013).

There are currently no known water-quality datasets 

describing legacy and emerging organic chemicals in the 

North Branch Au Sable River. In June 2018, the MDNR and 

the Michigan Department of Environment, Great Lakes, 

and Energy (EGLE) led an investigation concurrent with a 
2 Evaluation of Legacy and Emerging Organic Chemicals on the North Branch Au Sable River near Lovells, Michigan, June 2018

U.S. Geological Survey (USGS) passive sampling study to 

investigate the trout population in the North Branch Au Sable 

River. The MDNR/EGLE investigation was prompted owing 

to anglers’ reports of poor fishing and a measured decline 

in the number of fish surveyed by the MDNR. The EGLE’s 

Water Resources Division led three Procedure 51 habitat 

and macroinvertebrate surveys (Michigan Department of 

Environmental Quality, 2008) in mid-June and determined that 

all three sites surveyed (Twin Bridge Road, The Ford Road, 

and Dam 4) had excellent macroinvertebrate diversity, indicating excellent water quality (MDNR, 2018). In addition, the 

EGLE Fisheries Division led electrofishing surveys at three 

locations on the North Branch Au Sable River (Twin Bridge 

Road, Eamon’s Landing, and Dam 4), revealing a low density and low biomass of brook trout. Brook trout density and 

biomass at Twin Bridge Road and Dam 4 were at the lowest 

recorded levels in the past 30 years (MDNR, 2018).

The 2018 USGS study was completed in cooperation with 

Lovells Township, Michigan and prepared for the Mason-Griffith 

Founders Chapter of Trout Unlimited, to evaluate the potential 

presence and concentration of organic chemicals in the North 

Branch Au Sable River using passive sampling technology, 

#*

#*

Au Sable R

#* iver

Lovells Lovells Twp

#*

#*

Au Sable River

North Branch Au Sable Riv er

North Branch Au Sable River 

at Eamon’s Landing

North Branch Au Sable River 

at Bent Tree Drive, 04135755

North Branch Au Sable River 

at Ford Road, 04135765

North Branch Au Sable River 

at Twin Bridge Road, 04135782

North Branch Au Sable River 

at Kellogg’s Bridge, 04135800

Au Sable River 

near Red Oak, 04136000

North Branch Au Sable River 

at Dam 4

0 5 10 15 MILES

0 5 10 15 KILOMETERS

84°45' 84°40' 84°35' 84°30' 84°25' 84°20' 84°15'

45°00'

44°55'

44°50'

44°45'

44°40'

#*

#*

EXPLANATION

U.S. Geological Survey (USGS) sampling location, 

name, and identifier

USGS streamgage location, name, and identifier

Michigan Department of Environment, Great Lakes, 

and Energy (EGLE) Water Resources Division 

Procedure 51 sampling location

EGLE Fisheries Division electrofishing survey location

Camp Grayling

MICHIGAN

Study area

Lake 

Ostego

Map image is the intellectual property of Esri and is used herin under license. 

Copyright © 2019 Esri and its licensors. All rights reserved. 

Hydrography from U.S. Geological Survey, National Geospatial Program, published 

20191026 for Michigan State or Territory Shapefile Model Version 2.2.1

Figure 1. North Branch Au Sable River passive sampler monitoring and streamgage locations near Lovells, Michigan, 2018.
Methods 3

specifically semipermeable membrane devices (SPMDs) and 

polar organic chemical integrative samplers (POCISs). The first 

objective of this study was to assess if concentrations of organic 

chemicals were present in quantities that may potentially harm 

sensitive aquatic species in the North Branch Au Sable River. 

The second objective was to establish the current conditions of 

organic chemicals for the North Branch Au Sable River against 

which future data can be compared.

Passive samplers can provide information on the concentration, occurrence, transport, and fate of organic chemicals 

by absorbing dissolved organic chemicals in the river over 

the course of their deployment, which typically lasts several 

weeks. The benefits of using SPMDs and POCISs compared 

to collecting discrete water samples include the following: 

(1) passive samplers provide a way to monitor episodic events, 

such as surface runoff, spills, and other point and nonpoint 

source contamination, as well as other isolated or short-lived 

pulses of chemicals in the water; (2) passive samplers are 

relatively less expensive than trying to collect enough discrete 

samples to account for episodic events; and (3) passive samplers also offer the ability to simulate a time-period exposure 

similar to what aquatic species might endure (Alvarez, 2010). 

Passive, integrative samplers provide a means of measuring 

time-weighted average (TWA) concentrations of dissolved 

organic chemicals while meeting many of the detection limit 

requirements of common instrumental techniques by sampling large volumes of water over prolonged exposure periods 

(Huckins and others, 2006; Alvarez and others, 2007).

Purpose and Scope

The purpose of this report is to describe the evaluation of legacy and emerging organic chemicals using passive 

sampling devices that were deployed at four locations along 

the North Branch Au Sable River, near Lovells, Mich., in 

June 2018 for a total of 28 days. The chemical classes investigated as part of this study included pesticides (both legacy 

[organochlorine] and current use), polychlorinated biphenyls 

(PCBs), polybrominated diphenyl ethers (PBDEs), and polycyclic aromatic hydrocarbons (PAHs).

Background

The Au Sable River watershed is in the northern region of 

Michigan’s lower peninsula (fig. 1) and is known to have some 

of the best trout fishing in the United States (MDNR, Fisheries 

Division, 1987). The North Branch Au Sable River is approximately 36 miles long; its headwaters begin in Otsego Lake and 

the river flows generally southeastward to the north Crawford 

county line then south at the town of Lovells where it enters the 

main branch of the Au Sable River about a mile downstream 

from McMasters Bridge (MDNR, Fisheries Division, 1987) 

(fig. 1, McMaster Bridge not shown in fig. 1). The width of 

the North Branch Au Sable River varies from about 40 feet to 

more than 150 feet nearer the mouth. The National Guard Joint 

Maneuvering facility (Camp Grayling) artillery range borders 

the upper North Branch Au Sable River on the south in Otsego 

County and on the west in Crawford County (MDNR, Fisheries 

Division, 1987) (fig. 1). The main stem of the Au Sable River 

is approximately 139 miles long; it runs through the cities of 

Grayling (fig. 1) and Mio and eventually empties into Lake 

Huron in Oscoda Township (not shown in fig. 1).

Methods

Passive samplers were deployed at four USGS sampling locations (table 1, fig. 1) on the North Branch Au Sable 

River, near Lovells, Mich., on June 1, 2018, and retrieved on 

June 29, 2018, for a total deployment of 28 days. At each location, two SPMDs and one POCIS were installed.

The SPMDs are typically used for sampling neutral 

organic chemicals (such as PAHs, PCBs, chlorinated pesticides, PBDEs, dioxins, furans, and hydrophobic chemicals) 

with a log octanol-water partition coefficient (Kow) greater 

than 3 (Alvarez, 2010). POCISs are designed to sample the 

more water-soluble organic chemicals (including most pharmaceuticals, illicit drugs, polar pesticides, phosphate flame 

retardants, surfactants, metabolites, and degradation products) 

with a log Kow less than 3; however, chemicals with a log Kow

between 4 and 5 are frequently reported (Alvarez, 2010).

Field Methods

Samplers were deployed and the results were analyzed 

based on published techniques and methods for use of 

SPMDs and POCISs in environmental monitoring studies 

(Alvarez, 2010). General stream water chemistry data (temperature, specific conductance, dissolved oxygen, and pH) 

were measured during deployment and retrieval using a calibrated YSI 6920 multiparameter water-quality sonde using 

methods described by U.S. Geological Survey (variously 

dated). Also measured was the depth of the passive sampler 

canisters in relation to the water surface, water conditions 

(clear, murky), flow conditions (characterized using the nearest USGS streamgage, Au Sable River near Red Oak, Mich., 

04136000; U.S. Geological Survey, 2018) (fig. 1), and stream 

substrate type (table 1).

Sampling devices were deployed in approximately 2 to 

3 feet of water, ensuring that the devices remain submerged 

under water for the entirety of the 28 days, as exposure to the 

atmosphere could potentially contaminate the passive sampling devices owing to the presence of airborne chemicals. 

Each sampling device was attached to a cinder block using 

stainless steel clamps and the cinder blocks were placed in a 

location in the river where there was constant flow; areas of 

highest flow were avoided to reduce potential damage from 

debris and boat traffic. The cinder blocks were secured to a 

fixed point on the streambank so that the samples would be 

retrievable if there were high flow velocities.
Table 1. Passive sampler deployment and retrieval site conditions, North Branch Au Sable River, 2018. [Mich., Michigan; M, month; D, day; YYYY, year; EST, eastern standard time; °C, degree Celsius; μS/cm, microsiemen per centimeter; mg/L, milligram per liter; ft, foot] Site conditions North Branch Au Sable River at Bent Tree Drive near Gaylord, Mich. (04135755) North Branch Au Sable River at The Ford Road near Lovells, Mich. (04135765) Replicate - North Branch Au Sable River at The Ford Road near Lovells, Mich. (04135765) North Branch Au Sable River at Twin Bridge Road near Lovells, Mich. (04135782) 

Deployment Deployment date (M/D/YYYY) 6/1/2018 6/1/2018 6/1/2018 6/1/2018 

Deployment time (EST) 8:30 a.m. 10:00 a.m. 10:07 a.m. 11:00 a.m. 

Water temperature (°C) 14.4 18.9 18.9 17.5 

Specific conductance (μS/cm) 425 299 299 299 Dissolved oxygen (mg/L) 6.9 7 7 8.4 pH 8.7 8.9 8.9 8.8 Depth of canister (ft) 1 1.5 1.5 1.5 

Water conditions Clear Clear Clear Clear 

Substrate conditions Gravel, sand, muck Gravel, sand, muck Gravel, sand, muck Gravel, sand Flow conditions Slow Moderate Moderate Moderate Field blank collected Yes No No No 

Retrieval Retrieval date (M/D/YYYY) 6/29/2018 6/29/2018 6/29/2018 6/29/2018 

Retrieval time (EST, a.m.) 8:30 a.m. 9:30 a.m. 9:37 a.m. 10:30 a.m. 

Water temperature (°C) 14.4 18.9 18.9 16.8 

Specific conductance (μS/cm) 447 325 325 321 Dissolved oxygen (mg/L) 7.9 7.8 7.8 8.8 pH 7.9 7.7 7.7 7.8 Depth of canister (ft) 0.8 1 1 0.7 

Water conditions Clear Clear Clear Clear 

Substrate conditions Sand, muck, silt Cobble, gravel, sand Cobble, gravel, sand Gravel, sand Flow conditions Slow Moderate Moderate Moderate Field blank collected Yes No No No 
Methods 5

A, Internal view of polar organic 

chemical integrative sampler (POCIS) 

and B, semipermeable membrane device 

(SPMD) deployment canister.

B

A

.
6 Evaluation of Legacy and Emerging Organic Chemicals on the North Branch Au Sable River near Lovells, Michigan, June 2018

Upon retrieval, the SPMD and POCISs were sealed in 

clean, airtight metal cans and shipped chilled with freezer 

packs overnight to the USGS Columbia Environmental 

Research Center (CERC). SPMD and POCIS field blanks 

were exposed to the air during sampler deployment on 

June 1, 2018, then resealed in clean, airtight metal cans and 

placed in the freezer at less than 0 degrees Celsius until 

sample retrieval on June 29, 2018, when the metal cans were 

re-opened, exposed to the air during retrieval, and then resealed for a final time.

Laboratory Methods

Chemicals were recovered from the SPMDs using a 

hexane dialysis followed by fractionation using size-exclusion 

chromatography to isolate chemicals of interest from potential 

interferences. Fractions designated for PAH analyses were 

passed through columns of acidic, neutral, and basic silica gel 

as a final cleanup step. These samples were then analyzed using 

gas chromatography/mass spectrometry. Fractions designated 

for legacy pesticides, total PCBs, and PBDEs underwent additional cleanup and fractionation using sequential columns of 

Florisil® and deactivated silica gel. Analyses for these chemicals were performed using gas chromatography with electron 

capture detections. Details of the process and analysis methods 

have been previously described (Alvarez and others, 2008).

Current-use pesticides were extracted from the POCIS 

using a solvent mixture of 80:20 volume per volume 

dichloromethane:methyl-tert-butyl ether, which was then 

solvent exchanged into ethyl acetate prior to ampoulation. 

The sealed ampoules containing the POCIS extracts were then 

sent to the USGS National Water Quality Laboratory (NWQL) 

for analysis for current-use pesticides and herbicides (NWQL 

lab code 8156) using methods described by Zaugg and others (2007).

An approach for providing a TWA assessment is critical for an improved understanding of the consequences of 

prolonged exposure to environmental chemical mixtures. 

The TWA assessment provides an average concentration over 

time; therefore, there is no way to distinguish whether the 

chemical concentration occurred during one episodic event 

or many episodic events, or whether there was a continuous 

input of chemicals to the river. Passive, integrative samplers 

provide a means of measuring the TWA concentrations of 

dissolved organic chemicals while meeting many of the detection limit requirements of common instrumental techniques 

by sampling large volumes of water over prolonged exposure periods (Huckins and others, 2006; Alvarez and others, 

2007). TWA water concentrations of targeted chemicals were 

determined from measured amounts in the SPMDs and POCIS 

using first-order models for chemical uptake as described in 

Alvarez (2010).

Quality Control and Quality Assurance

Replicate SPMD and POCIS devices were deployed 

at the North Branch Au Sable River at The Ford Road near 

Lovells, Michigan (04135765) (fig. 1). Field replicate data 

are reported as relative percent difference and calculated 

for constituents with values above the method detection 

limit (MDL) and laboratory reporting level (LRL) by using 

equation 1.

RPDaverage = [|sample 1–sample 2|/Average]*100, (1)

where

RPDaverage is the average relative percent difference;

sample 1 is the concentration in sequential replicate 1, 

in picograms or micrograms per liter;

sample 2 is the concentration in sequential

replicate 2, in picograms or micrograms 

per liter; and

Average is the average of concentration in the two 

concurrent replicates, in picograms or 

micrograms per liter.

Additionally, SPMD and POCIS field blanks were 

collected at the North Branch Au Sable River at Bent Tree 

Drive near Gaylord, Michigan. The field blank was used to 

determine the MDL and method quantitation limit (MQL), 

where the MDL is the mean of the blank measurements for 

a single chemical plus three times the standard deviation 

(Alvarez, 2010).

Polar organic chemical integrative sampler (POCIS) and 

semipermeable membrane device (SPMD) deployment canister 

were attached to a concrete cinder block with stainless steel 

clamps.
Results and Evaluation of Legacy and Emerging Organic Chemicals 7

The polar organic chemical integrative sampler (POCIS) and 

semipermeable membrane device (SPMD), and replicate, 

deployed at the U.S. Geological Survey streamgage North 

Branch Au Sable River at The Ford Road near Lovells, 

Michigan (04135765).

Results and Evaluation of Legacy and 

Emerging Organic Chemicals

This section of the report presents the concentration 

results of legacy and emerging organic chemicals in samples 

collected in June 2018 at four site along the North Branch 

Au Sable River. An evaluation of the organic chemicals and 

quality-assurance results also are included in this section.

All organic chemical data detected at concentrations 

above the MQL (CERC lab results) and above the LRL 

(NWQL lab results) were compared to eight benchmark 

water-quality standards, where such standards have been set 

(table 2). To calculate the estimated water concentration of 

a chemical, an experimentally derived sampling rate for that 

chemical must be known; therefore, only those data with a 

published sampling rate available were included in this analysis (Alvarez, 2010).

Several organic chemicals were detected at concentrations above the MQL (tables 3 and 4) and above the LRL 

(table 5) and are described in further detail in the following 

sections. The use of the terms MQL, MDL, and LRL are 

defined by the laboratory performing the analyses, where 

CERC reports data using MDL and MQL (Alvarez, 2010), and 

the NWQL reports data using LRL (Oblinger Childress and 

others, 1999).

Results of organic chemicals that were detected at 

concentrations above the MDL but less than the MQL are 

included in tables 3 and 4. These data are indicated in italics and have greater uncertainty in the absolute concentration values. Further information on how the MDL and MQL 

are calculated are presented in Alvarez, 2010. These results 

are described in further detail in the “Organic Chemical 

Detections above the Method Detection Limit” section.

Legacy Pesticides, Total Polychlorinated 

Biphenyls, and Polybrominated Diphenyl Ethers

Organochlorine pesticides, or legacy pesticides, include 

pesticides that have been banned in the United States or are 

in limited use and are still being detected in surface water, 

groundwater, sediment, and biota many years later (Nowell 

and others, 1999). Similar to legacy pesticides, PCBs are no 

longer commercially produced in the United States but may 

be present in products and materials produced before the 1979 

ban. These products include transformers, capacitors, hydraulic oil and motor oil, cable insulation, adhesives and tapes, and 

oil-based paint (EPA, 2019a). Since the 1970s, PBDEs have 

been used as flame retardants in a wide variety of products, 

including plastics, furniture, upholstery, electrical equipment, 

electronic devices, textiles, and other household products 

(EPA, 2017). PBDEs are still being produced and have been 

used widely in the United States since the 1970s; however, 

there is growing concern about their persistence in the environment and their tendency to bioaccumulate (EPA, 2017). 

Concentrations for legacy pesticides, PCB, and PBDE data 

collected as part of this study are presented in table 3.

Legacy Pesticides

Eight legacy pesticides were detected above the laboratory MQL (table 3) at low concentrations with one pesticide 

exceeding the benchmark standards listed in table 2. At North 

Branch Au Sable River at Bent Tree Drive near Gaylord, 

Mich. (04135755), p,p’-dichlorodiphenyldichloroethylene 

(DDE, a common breakdown product of dichlorodiphenyltrichloroethane [DDT]) was detected at a concentration 

of 0.000021 micrograms per liter (μg/L) (table 3), which is 

above the EPA human health criteria for the consumption 

of water plus organism of 18 picograms per liter (pg/L) or 

0.000018 μg/L (EPA, 2015). The EPA human health criteria for the consumption of water plus organism includes 

the two primary pathways of human exposure to pollutants 

through direct ingestion of drinking water and consumption of fish or shellfish obtained from the water body (EPA, 

2015). Heptachlor epoxide was also detected very near the 

EPA human health criteria for the consumption of water plus 
Table 2. Benchmark water-quality standards for those organic chemicals detected above the method quantitation limit. [EPA, U.S. Environmental Protection Agency; μg/L, microgram per liter; CMC, criterion maximum concentration; CCC, criterion continuous concentration; +, plus; MCL, MaxDWEL, Drinking Water Equivalent Level; na, no benchmark standards available; DDE, dichlorodiphenyldichloroethylene; DDT, dichlorodiphenyltrichloroethane; na, not availaPBDE, polybrominated diphenyl ether; PHA, polycyclic aromatic hydrocarbon; EGLE, Michigan Department of Environment, Great Lakes, and Energy] Detected compound Common sources or uses of contaminant1,2,3,4 Michigan aquatic life final chronic value (μg/L)2 EPA office of pesticide programs aquatic life benchmarks fish acute (freshwater), (μg/L)3 EPA aquatic life criteria acute (freshwater CMC), (μg/L)5 EPA aquatic life criteria chronic (freshwater CCC) (μg/L)5 EPA human health criteria (human health for the con- sumption of water + organ- ism) (μg/L)6 EPA drinkin

water M

(μg/L)7 

Legacy (organochlorine) pesticides Trifluralin Used as an herbicide to control grasses, crops, shrubs, and flowers na 9.25 na na na na 

PCA Degradate of pentaclo- rophenol (PCP). A restricted-use pesticide, no longer available to general public. Most commonly used as a wood preservative na 28 na na na na Oxychlordane Insecticide commonly used for termite control na na na na na na Heptachlor Epoxide Insecticide used for termite control and insect con- trol on farm crops 0.0700 na 0.52 0.0038 0.000032 0.4 trans-Chlordane Insecticide commonly used for termite control 0.0290 na na na na 2.0 cis-Chlordane Insecticide commonly used for termite control 0.0290 na na na na 2.0 p,p'-DDE Breakdown product of DDT, which was used in the past as an insecticide na na na na 0.000018 na p,p'-DDT Used in the past for the control of malaria, typhus, and other insect- transmitted diseases 0.0032 na 1.10 0.0010 0.000030 na 

PBDE 2,4,4'-tribromodiphenyl ether (PBDE-28) Flame retardant na na na na na na 
Table 2. Benchmark water-quality standards for those organic chemicals detected above the method quantitation limit.—Continued[EPA, U.S. Environmental Protection Agency; μg/L, microgram per liter; CMC, criterion maximum concentration; CCC, criterion continuous concentration; +, plus; MCL, MaxDWEL, Drinking Water Equivalent Level; na, no benchmark standards available; DDE, dichlorodiphenyldichloroethylene; DDT, dichlorodiphenyltrichloroethane; na, not availaPBDE, polybrominated diphenyl ether; PHA, polycyclic aromatic hydrocarbon; EGLE, Michigan Department of Environment, Great Lakes, and Energy]

Detected compound Common sources or uses of contaminant1,2,3,4

Michigan 

aquatic life 

final chronic 

value 

(μg/L)2

EPA office 

of pesticide 

programs 

aquatic life 

benchmarks 

fish acute 

(freshwater), 

(μg/L)3

EPA 

aquatic life 

criteria acute 

(freshwater 

CMC), 

(μg/L)5

EPA 

aquatic 

life criteria 

chronic 

(freshwater 

CCC) 

(μg/L)5

EPA human 

health criteria (human health 

for the consumption of 

water + organism) (μg/L)6

dr

w

(μ

PAHs

Fluorene Used in manufacturing of dyes, 

plastics, and pesticides

12 na na na 50 

Phenanthrene Used in manufacturing explosives; component of tar, diesel 

fuel, or crude oil; combustion product

1.7 na na na na 

Fluoranthene Component of coal tar and asphalt (only traces in gasoline 

or diesel fuel), combustion product

1.6 na na na 20 

2,3,5-trimethylnaphthalene Used as an insecticide and pest 

repellent

na na na na na 

1-methylfluorene Component of coal tar and asphalt (only traces in gasoline 

or diesel fuel), combustion product

na na na na na 

2-methylphenanthrene Used in manufacturing explosives; component of tar, diesel 

fuel, or crude oil; combustion product

na na na na na 

3,6-dimethylphenanthrene Used in manufacturing explosives; component of tar, diesel 

fuel, or crude oil; combustion product

na na na na na 

Perylene Used to make dyes, plastics, 

pesticides, explosives, and drugs. It has also been used to make bile acids, cholesterol, and steroids

na na na na na 
Table 2. Benchmark water-quality standards for those organic chemicals detected above the method quantitation limit.—Continued [EPA, U.S. Environmental Protection Agency; μg/L, microgram per liter; CMC, criterion maximum concentration; CCC, criterion continuous concentration; +, plus; MCL, MaxDWEL, Drinking Water Equivalent Level; na, no benchmark standards available; DDE, dichlorodiphenyldichloroethylene; DDT, dichlorodiphenyltrichloroethane; na, not availaPBDE, polybrominated diphenyl ether; PHA, polycyclic aromatic hydrocarbon; EGLE, Michigan Department of Environment, Great Lakes, and Energy] Detected compound Common sources or uses of contaminant1,2,3,4 Michigan aquatic life final chronic value (μg/L)2 EPA office of pesticide programs aquatic life benchmarks fish acute (freshwater), (μg/L)3 EPA aquatic life criteria acute (freshwater CMC), (μg/L)5 EPA aquatic life criteria chronic (freshwater CCC) (μg/L)5 EPA human health criteria (human health for the con- sumption of water + organ- ism) (μg/L)6 EPA drinkin

water M

(μg/L)7 

Current-use pesticides Acetochlor Herbicide used to control weeds and approved for pre-emergent and pre- planting application na 190 na na na na 

Atrazine Primarily used in agricul- ture for weed control on row crops 7.3 2,650 na na na 3.0 Metolachlor Pre-emergence herbicide used in agriculture for control of broadleaf and annual grassy weeds for several crops, primarily corn and soybeans 15 1,900 na na na na 

1U.S. Geological Survey Techniques and Methods 5–B4 (Zaugg and others, 2007). 2Michigan rule 57 surface water-quality values (EGLE, 2019). 3EPA Office of Pesticide Programs, Aquatic Life Benchmarks (EPA, 2019b). 4EPA Lifetime Health Advisory and Drinking Water Standards (EPA, 2018). 5EPA National Recommended Water Quality Criteria, Aquatic Life Criteria table (EPA, 2019c). 6EPA Human Health Criteria Table (EPA, 2015). 7EPA National Primary Drinking Water Regulations (EPA, 2019d). 8Lifetime Health Advisory and Drinking Water Standards for pentachlorophenol (EPA, 2018). 9Lifetime Health Advisory and Drinking Water Standards for chlordane (EPA, 2018). 10Lifetime Health Advisory and Drinking Water Standards for naphthalene (EPA, 2018).
Table 3. Legacy (organochlorine) pesticides, total polychlorinated biphenyls (PCBs), and polybrominated diphenyl ether (PBDE) residues sampled by membrane devices (SPMDs) reported as time-weighted average (June 1–29, 2018) water concentrations in units of picograms per liter.[pg/L, picogram per liter; Mich., Michigan; <, less than; HCB, hexachlorobenzene; PCA, pentachloroanisole; a-BHC, alpha-benzenehexachloride; b-BHC, beta-benzenehexachlbenzenehexachloride; DDE, dichlorodiphenyldichloroethylene; DDD, dichlorodiphenyldichloroethane; DDT, dichlorodiphenyltrichloroethane; PCB, total polychlorinated biphediphenyl ether; EPA, U.S. Environmental Protection Agency; +, plus. Samples analyzed at the U.S. Geological Survey Columbia Environmental Research Center, Columbia, Mireportable values greater than the method quantitation limit. Italic values denote estimated values greater than the method detection limit but less than the method quantitation li

Chemical

Method 

detection limit

(pg/L)1

Method 

quantitation limit

(pg/L)1

North Branch 

Au Sable River at 

Bent Tree Drive 

near Gaylord, 

Mich. (04135755)

(pg/L)1

North Branch 

Au Sable River at 

The Ford Road 

near Lovells, 

Mich. (04135765)

(pg/L)1

Replicate–North 

Branch Au Sable 

River at The Ford 

Road near

Lovells, Mich. 

(04135765)

(pg/L)1

North Branch 

Au Sable River 

at Twin Bridge 

Road near 

Lovells, Mich. 

(04135782)

(pg/L)1

Legacy (organochlorine) pesticides

Trifluralin 0.37 1.9 440 <0.37 <0.37 <0.37 HCB 1.5 7.6 <1.5 <1.5 <1.5 <1.5 PCA 1.9 7.4 18 34 26 12 

Tefluthrin 3.1 15 <3.1 <3.1 <3.1 <3.1 

a-BHC 15 45 <15 <15 <15 <15 Lindane 7.4 37 <7.4 <7.4 <7.4 <7.4 b-BHC 5.4 27 <5.4 <5.4 <5.4 <5.4 Heptachlor 1.5 7.6 <1.5 <1.5 <1.5 <1.5 d-BHC 3.4 17 <3.4 <3.4 <3.4 <3.4 Dacthal 2.8 14 <2.8 <2.8 <2.8 <2.8 Chlorpyrifos 20 41 <20 <20 <20 <20 Oxychlordane 1.5 7.4 9.4 <1.5 10 5.6 Heptachlor 

Epoxide 2.1 11 3.3 6.4 <2.1 16 

trans-Chlordane 1.5 7.4 4.1 3.5 3.1 7.8 trans-Nonachlor 1.9 9.4 6.7 <1.9 2.9 4.9 o,p'-DDE 1.5 7.5 <1.5 <1.5 <1.5 <1.5 cis-Chlordane 1.5 7.4 6.6 <1.5 1.7 2.1 Endosulfan 22 110 <22 <22 <22 <22 p,p'-DDE 2.6 8.6 421 9.9 8 5.5 Dieldrin 6.8 14 <6.8 <6.8 <6.8 <6.8 o,p'-DDD 1.7 8.4 <1.7 <1.7 <1.7 <1.7 Endrin 1.9 9.7 <1.9 <1.9 <1.9 <1.9 cis-Nonachlor 1.8 8.8 <1.8 <1.8 <1.8 <1.8 
Table 3. Legacy (organochlorine) pesticides, total polychlorinated biphenyls (PCBs), and polybrominated diphenyl ether (PBDE) residues sampled by membrane devices (SPMDs) reported as time-weighted average (June 1–29, 2018) water concentrations in units of picograms per liter.—Continued [pg/L, picogram per liter; Mich., Michigan; <, less than; HCB, hexachlorobenzene; PCA, pentachloroanisole; a-BHC, alpha-benzenehexachloride; b-BHC, beta-benzenehexachlbenzenehexachloride; DDE, dichlorodiphenyldichloroethylene; DDD, dichlorodiphenyldichloroethane; DDT, dichlorodiphenyltrichloroethane; PCB, total polychlorinated biphediphenyl ether; EPA, U.S. Environmental Protection Agency; +, plus. Samples analyzed at the U.S. Geological Survey Columbia Environmental Research Center, Columbia, Mireportable values greater than the method quantitation limit. Italic values denote estimated values greater than the method detection limit but less than the method quantitation li

Chemical Method detection limit (pg/L)1 Method quantitation limit (pg/L)1 North Branch Au Sable River at Bent Tree Drive near Gaylord, Mich. (04135755) (pg/L)1 North Branch Au Sable River at The Ford Road near Lovells, Mich. (04135765) (pg/L)1 Replicate–North Branch Au Sable River at The Ford Road near Lovells, Mich. (04135765) (pg/L)1 North Branch Au Sable River at Twin Bridge Road near Lovells, Mich. (04135782) (pg/L)1 

Legacy (organochlorine) pesticides—Continued o,p'-DDT 1.5 7.5 <1.5 <1.5 <1.5 <1.5 

p,p'-DDD 5.5 12 <5.5 6.9 5.9 <5.5 Endosulfan-II 85 250 <85 <85 <85 <85 p,p'-DDT 5.3 7.4 9.9 8.4 6.6 5.4 Endosulfan Sulfate 32 160 <32 <32 <32 <32 p,p'- Methoxychlor 20 99 <20 <20 <20 <20 Mirex 2.5 13 <2.5 <2.5 <2.5 <2.5 cis-Permethrin 360 980 <360 <360 <360 <360 trans-Permethrin 5.5 27 <5.5 <5.5 <5.5 <5.5 

PCBs Total PCBs 270 1,400 <270 480 <270 300 
Table 3. Legacy (organochlorine) pesticides, total polychlorinated biphenyls (PCBs), and polybrominated diphenyl ether (PBDE) residues sampled by membrane devices (SPMDs) reported as time-weighted average (June 1–29, 2018) water concentrations in units of picograms per liter.—Continued[pg/L, picogram per liter; Mich., Michigan; <, less than; HCB, hexachlorobenzene; PCA, pentachloroanisole; a-BHC, alpha-benzenehexachloride; b-BHC, beta-benzenehexachlbenzenehexachloride; DDE, dichlorodiphenyldichloroethylene; DDD, dichlorodiphenyldichloroethane; DDT, dichlorodiphenyltrichloroethane; PCB, total polychlorinated biphediphenyl ether; EPA, U.S. Environmental Protection Agency; +, plus. Samples analyzed at the U.S. Geological Survey Columbia Environmental Research Center, Columbia, Mireportable values greater than the method quantitation limit. Italic values denote estimated values greater than the method detection limit but less than the method quantitation li

Chemical

Method 

detection limit

(pg/L)1

Method 

quantitation limit

(pg/L)1

North Branch 

Au Sable River at 

Bent Tree Drive 

near Gaylord, 

Mich. (04135755)

(pg/L)1

North Branch 

Au Sable River at 

The Ford Road 

near Lovells, 

Mich. (04135765)

(pg/L)1

Replicate–North 

Branch Au Sable 

River at The Ford 

Road near

Lovells, Mich. 

(04135765)

(pg/L)1

North Branch 

Au Sable River 

at Twin Bridge 

Road near 

Lovells, Mich. 

(04135782)

(pg/L)1

PBDEs

PBDE-28 2.5 7.9 3.2 3.4 3.3 4.6 PBDE-47 160 410 <160 <160 <160 <160 PBDE-66 13 36 <13 <13 <13 <13 PBDE-85 58 130 <58 <58 <58 <58 PBDE-99 100 240 <100 <100 <100 <100 PBDE-100 26 67 <26 <26 <26 <26 PBDE-153 130 370 <130 <130 <130 <130 PBDE-154 42 110 <42 <42 <42 <42 PBDE-183 16 81 <16 19 17 <16 

1To convert to micrograms per liter, divide picograms per liter by 1,000,000.2Less than (<) values are concentrations below the method detection limit.3Concentration is near the recommended EPA Human Health Criteria standard, Human Health for the consumption of water + organism (of 32 pg/L).4Concentration exceeds the recommended EPA Human Health Criteria standard, Human Health for the consumption of water + organism (of 18 pg/L).
Table 4. Polycyclic aromatic hydrocarbons (PAHs) sampled by semi-permeable membrane devices (SPMDs) reported as time-weighted average (Juconcentrations in units of picograms per liter. [pg/L, picogram per liter; Mich., Michigan; PAH, polycyclic aromatic hydrocarbon; <, less than. Samples analyzed at the USGS Columbia Environmental Research Center, Coludenote reportable values greater than the method quantitation limit. Italic values denote estimated values greater than the method detection limit but less than the method quantit

Chemical Method detection limit (pg/L)1 Method quantitation limit (pg/L)1 North Branch Au Sable River at Bent Tree Drive near Gaylord, Mich. (04135755) (pg/L)1 North Branch Au Sable River at The Ford Road near Lovells, Mich. (04135765) (pg/L)1 Replicate– North Branch Au Sable River at The Ford Road near Lovells, Mich. (04135765) (pg/L)1 N

B

Au 

R

Twi

Ro

Love

(04

(

PAHs Naphthalene 13,000 21,000 <13,000 <13,000 <13,000 <1

Acenaphthylene 150 290 <150 <150 <150 Acenaphthene 240 520 <240 <240 <240 

Fluorene 110 180 <110 <110 <110 Phenanthrene 95 110 290 250 210 

Anthracene 88 180 <88 <88 <88 

Fluoranthene 91 180 210 160 120 Pyrene 82 160 150 110 <82 Benz[a]anthracene 16 80 <16 <16 <16 Chrysene 15 75 36 35 24 Benzo[b]fluoranthene 15 77 <15 <15 <15 Benzo[k]fluoranthene 18 88 <18 <18 <18 Benzo[a]pyrene 19 94 <19 <19 <19 Indeno[1,2,3-cd]pyrene 23 120 <23 <23 <23 Dibenzo[a,h]anthracene 20 100 <20 <20 <20 Benzo[g,h,I]perylene 25 130 <25 <25 <25 Benzo[b]thiophene 530 2,600 <530 <530 <530 2-Methylnaphthalene 110 270 <110 120 120 1-Methylnaphthalene 54 270 63 190 190 Biphenyl 50 250 <50 <50 <50 1-Ethylnaphthalene 24 120 <24 <24 <24 1,2-Dimethylnaphthalene 28 140 <28 <28 <28 
Table 4. Polycyclic aromatic hydrocarbons (PAHs) sampled by semi-permeable membrane devices (SPMDs) reported as time-weighted average (Juconcentrations in units of picograms per liter.—Continued[pg/L, picogram per liter; Mich., Michigan; PAH, polycyclic aromatic hydrocarbon; <, less than. Samples analyzed at the USGS Columbia Environmental Research Center, Coludenote reportable values greater than the method quantitation limit. Italic values denote estimated values greater than the method detection limit but less than the method quantit

Chemical

Method 

detection limit

(pg/L)1

Method 

quantitation limit

(pg/L)1

North 

Branch 

Au Sable 

River at 

Bent Tree 

Drive near 

Gaylord, Mich. 

(04135755)

(pg/L)1

North 

Branch 

Au Sable 

River at The 

Ford Road 

near Lovells, 

Mich. 

(04135765)

(pg/L)1

Replicate–

North 

Branch 

Au Sable 

River at The 

Ford Road 

near Lovells, 

Mich. 

(04135765)

(pg/L)1

N

B

Au 

R

Twi

Ro

Love

(04

(

PAHs

4-Methylbiphenyl 48 130 <48 <48 <48 2,3,5-Trimethylnaphthalene 17 83 17 120 95 1-Methylfluorene 16 81 <16 200 140 Dibenzothiophene 24 120 26 28 24 2-Methylphenanthrene 17 83 45 210 160 9-methylanthracene 16 78 <16 <16 <16 3,6-Dimethylphenanthrene 15 74 <15 84 56 2-Methylfluoranthene 15 74 <15 20 <15 Benzo[b]naphtho[2,1-d]thiophene 15 75 <15 <15 <15 Benzo[e]pyrene 19 96 <19 <19 <19 Perylene 17 85 110 1,100 770 

1To convert to micrograms per liter, divide picograms per liter by 1,000,000.2Less than (<) values are concentrations below the method detection limit.
Table 5. Current-use pesticides sampled by polar organic chemical integrative sampler (POCIS) reported as time-weighted average (June 1‒29, 2018units of picograms per liter. [pg/L, picogram per liter; Mich., Michigan; <, less than; EPTC, s-ethyl dipropylthiocarbamate . Samples analyzed at the U.S. Geological Survey National Water Quality Laboratvalues denote reportable values greater than the laboratory reporting level] Chemical Laboratory reporting level (pg/L)1 North Branch Au Sable River at Bent Tree Drive near Gaylord, Mich. (04135755) (pg/L)1 North Branch Au Sable River at The Ford Road near Lovells, Mich. (04135765) (pg/L)1 Replicate–North Branch Au Sable River at The Ford Road near Lovells, Mich. (04135765) (pg/L)1 North B

Au Sable 

Twin Brid

near Lo

Mich. (04

(pg/

Current-use pesticides Acetochlor 890 2<890 2,000 1,800 1,

Alachlor 850 <850 <850 <850 <Alpha-HCH 330 <330 <330 <330 <

Atrazine 1,200 <1,200 6,500 4,900 2,Butylate 610 <610 <610 <610 <Carbaryl 160,000 <160,000 <160,000 <160,000 <160,Carbofuran 82,000 <82,000 <82,000 <82,000 <82,Chlorpyrifos 7,100 <7,100 <7,100 <7,100 <7,Cyanazine 2,300 <2,300 <2,300 <2,300 <2,Deethylatrazine 1,900 <1,900 <1,900 <1,900 <1,Diazinon 670 <670 <670 <670 <EPTC 590 <590 <590 <590 <Fipronil 1,700 <1,700 <1,700 <1,700 <1,Linuron 9,100 <9,100 <9,100 <9,100 <9,Malathion 110,000 <110,000 <110,000 <110,000 <110,Methyl parathion 2,300 <2,300 <2,300 <2,300 <2,Metolachlor 970 <970 2,700 2,300 1,Metribuzin 2,600 <2,600 <2,600 <2,600 <2,Pendimethalin 1,600 <1,600 <1,600 <1,600 <1,Prometon 950 <950 <950 <950 <Propachlor 1,200 <1,200 <1,200 <1,200 <1,Simazine 1,300 <1,300 <1,300 <1,300 <1,

1To convert to micrograms per liter, divide picograms per liter by 1,000,000. 2Less than (<) values are concentrations below the laboratory reporting level.
Results and Evaluation of Legacy and Emerging Organic Chemicals 17

organism (table 3), at 0.000031 μg/L but did not exceed the 

benchmark standard of 0.000032 μg/L (table 2) (EPA, 2015). 

Those legacy pesticides detected above the MQL include 

trifluralin (pre-emergence herbicide), pentachloroanisole 

(pesticide/biocide for wood preservation), oxychlordane 

(insecticide), heptachlor epoxide (insecticide), trans- and 

cis-chlordane (insecticides), DDE, and DDT (pesticide/insecticide) (table 3).

Seven legacy pesticides were detected above the MQL 

at low concentrations at North Brand Au Sable River at 

Kellogg’s Bridge near Lovells, Mich. (04135800) with fewer 

quantifiable detections at the remaining three North Branch 

Au Sable locations (table 3). Pentachloroanisole was the only 

legacy pesticide detected at all four sampling locations above 

the MQL (table 3).

Polychlorinated Biphenyls

No PCBs were detected at concentrations above the MQL 

at any of the four sampling locations on the North Branch Au 

Sable River (table 3).

Polybrominated Diphenyl Ethers

One PBDE analyte (PBDE-28; used in flame retardants 

and in a variety of products including building materials, 

electronics, furnishings, motor vehicles, plastics, polyurethane foams, and textiles) was detected at a concentration 

above the MQL (table 3). This analyte was detected at North 

Brand Au Sable River at Kellogg’s Bridge near Lovells, 

Mich. (04135800) where the highest number of legacy pesticides were detected. Presently, there does not appear to be a 

benchmark water-quality standard for PBDE-28 for which to 

compare these data.

Polycyclic Aromatic Hydrocarbons

PAHs include chemicals that are released from burning 

coal, oil, gasoline, wood, and garbage, and PAHs also can 

occur naturally in coal, crude oil, and gasoline (EPA, 2009). 

Eight PAH chemicals were detected at concentrations above 

the MQL and are presented in table 4.

Those PAH chemicals detected at concentrations above 

the MQL include fluorene; phenanthrene; fluoranthene; 

2,3,5-trimethylnaphthalene; 1-methylfluorene; 2-methylphenanthrene; 3,6-dimethylphenanthrene; and perylene. Six PAH 

chemicals were detected above the MQL in low concentrations 

at North Branch Au Sable River at The Ford Road (04135765), 

followed by 5 detections at North Branch Au Sable River at 

Kellogg's Bridge (04135800) and North Branch Au Sable 

River at The Ford Road replicate sample. None of the PAH 

chemicals detected exceeded the benchmark water-quality 

standards presented in table 2, where available (four of the 

eight PAHs detected have associated benchmark standards). 

Of those PAHs detected, perylene was detected above the 

MQL at each of the four sampling locations, and phenanthrene 

was detected at all locations except North Branch Au Sable 

River at Twin Bridge Road (04135782) (table 4).

Current-Use Pesticides

Current-use pesticides include those pesticides, herbicides, and insecticides that are still in use today. Only those 

current-use pesticides with published sampling rates are presented in table 5. Three current-use pesticides were detected 

in low concentrations above the LRL and include acetochlor 

(pre-emergence herbicide), atrazine (widely used herbicide), 

and metolachlor (widely used herbicide).

North Branch Au Sable River at Bent Tree Drive 

(04135755), which is the most upstream site sampled, was 

the only location where current-use pesticides were not 

detected. Acetochlor and metalachlor were detected at all 

locations except North Branch Au Sable River at Bent Tree 

Drive (04135755) (table 5). None of the current-use pesticides 

detected exceeded the benchmark water-quality standards 

presented in table 2.

Organic Chemical Detections above the Method 

Detection Limit

The site with the highest number of organic chemicals 

detected was North Branch Au Sable River at Kellogg’s 

Bridge (04135800) with 28 organic chemicals detected of the 

97 organic chemicals analyzed (approximately 29 percent). 

North Branch Au Sable River at Kellogg’s Bridge (04135800) 

is the most downstream sampling location and has the largest contributing watershed of all the sites (fig. 1). The North 

Branch Au Sable River at The Ford Road (04135765), and 

the replicate at that location, had the second and third highest 

number of organic chemicals detected (with 25 and 24 organic 

chemical detections, respectively; and approximately 26 percent and 25 percent, respectively). North Branch Au Sable 

River at Bent Tree Drive (04135755) had 19 organic chemicals detected (approximately 20 percent), and lastly North 

Branch Au Sable River at Twin Bridge Road (04135782) with 

16 organic chemicals detected (approximately 16 percent) 

(tables 3–5). No current-use pesticides were detected at 

North Branch Au Sable River at Bent Tree Drive (04135755) 

(table 5).

The most frequently detected organic contaminants that 

were detected at all sampling locations (including replicate 

sample at North Branch Au Sable River at The Ford Road 

04135765) include the legacy pesticides pentachloroanisole, trans-chlordane, p,p'-DDE, and p,p'-DDT; the PBDE 

PBDE-28; and the PAHs 2-methylphenanthrene and perylene 

(tables 3–5). Legacy pesticides oxychlordane, heptachlor 
18 Evaluation of Legacy and Emerging Organic Chemicals on the North Branch Au Sable River near Lovells, Michigan, June 2018

epoxide, trans-nonachlor, cis-chlordane were detected at all 

four sampling locations; however, at North Branch Au Sable 

River at The Ford Road (04135765) these legacy pesticides 

were detected in either the replicate or the routine sample but 

not in both the replicate and routine samples (tables 3–5).

Quality-Control and Quality-Assurance Results

Relative percent differences were calculated at the North 

Branch Au Sable River at The Ford Road near Lovells, Mich., 

for replicate organic chemical concentrations when both 

constituent pairs were greater than the MDL and (or) LRL. 

Relative percent difference for the paired replicates ranged 

from 0 to 40 percent difference depending on the constituent, 

with an average percent difference of 21 percent, and was considered an acceptable indication of variability in the samplecollection method and laboratory methods.

SPMD and POCIS field blanks were used to determine 

the MDL and MQL and are reported as MDL and MQL in 

tables 3 and 4 (Alvarez, 2010). The field blank was used to 

determine the MDL and MQL, where the MDL is the mean of 

the blank measurements for a single chemical plus three times 

the standard deviation (Alvarez, 2010).

Evaluation of Organic Chemicals

The North Branch Au Sable River can be considered 

a forest-dominated watershed with a smaller percentage of 

wetland, agricultural, livestock, and government-owned land 

uses (Zorn and Sendek, 2001). Land use may be an important 

predictor of organic contaminant detection, as streams located 

in developed urban and (or) agricultural watersheds have been 

shown to have more frequent detections and higher concentrations of many organic compounds compared to undeveloped 

watersheds (Baldwin and others, 2016). Seasonality may also 

affect the presence and detection of organic contaminants in 

the watershed, as some herbicide concentrations have shown 

distinct seasonal variation (Baldwin and others, 2016) related 

to agricultural and recreational applications in the watershed. 

The amount of precipitation affecting the watershed is another 

factor that could contribute to contaminant transport to surface waters.

These current findings are not dissimilar from previous 

studies in the Great Lakes where organic chemicals have been 

generally detected at concentrations in the nanogram or microgram per liter range and often below water-quality standards 

(Baldwin and others, 2016). However, low concentrations of 

organic chemicals may still pose a risk to aquatic organisms, 

as well as throughout the trophic hierarchy, because of lowdose effects, additive and synergistic mixture effects, transgenerational effects, and a lack of established water-quality 

benchmarks for many compounds (Baldwin and others, 2016). 

In Baldwin and others (2016), water samples from 35 percent 

of sites were composed of 10 or more chemicals. In the North 

Branch Au Sable study, water samples from all four locations 

(plus the replicate), or 100 percent of sites, were composed 

of 16 to 26 organic chemicals. Water-quality benchmarks are 

often established for singular chemicals and do not account 

for synergistic effects of these chemicals. In 1993, a Texas 

A&M study evaluated manufactured gas plant-PAH mixtures 

that indicated that benzo[a]pyrene and other PAHs (which 

are known to induce hepatic microsomal ethoxyresorufin 

O-deethylase [EROD] activity in mice) were only present as 

trace components of this mixture. A comparison of the EROD 

potencies of benzo[a]pyrene and the PAH mixture showed 

that the mixture was approximately 706 times more potent 

than expected based on the benzo[a]pyrene content alone 

thereby changing the overall carcinogenicity of the mixture 

(Chaloupka and others, 1993).

Organic contaminants and other contaminants in the 

North Branch Au Sable River could be evaluated using 

the R-script ToxEval that was developed by the USGS and 

includes a set of functions to analyze, visualize, and organize water quality data as it relates to EPA ToxCast data or 

other water quality criteria (De Cicco and others, 2018). 

ToxEval is used to develop a better understanding of the 

potential biological relevance of environmental chemistry 

data. ToxEval is often used as a screening technique to predict those chemicals that ultimately can be evaluated using 

aquatic bioassays to help evaluate the cumulative and synergistic mixture of chemicals present in the river (De Cicco 

and others, 2018).

Summary

Semi-permeable membrane devices and polar organic 

chemical integrative samplers are useful in their ability to 

monitor stream water quality during episodic events and during other isolated events where pulses of chemicals can enter 

the water. Passive samplers simulate a time-period exposure 

similar to what the aquatic species might endure in the same 

environment, and the results are calculated using a timeweighted average concentration. The time-weighted average 

assessment provides an average concentration over time; 

therefore, there is no way to distinguish whether the chemical concentration occurred during one episodic event or many 

episodic events, or whether there was a continuous input of 

chemicals to the river. Semi-permeable membrane devices 

and polar organic chemical integrative samplers provided an 

improved understanding of the prolonged exposure and environmental chemical mixtures aquatic organisms were exposed 

to in the North Branch Au Sable River.

Passive samplers were deployed at four locations along 

the North Branch Au Sable River, near Lovells, Michigan, 

in June 2018 for a total of 28 days in a study completed by 

the U.S. Geological Survey in cooperation with Lovells 

Township, Michigan, and prepared for the Mason-Griffith 

Founders Chapter of Trout Unlimited, to evaluate the potential presence and concentration of organic chemicals in the 
References Cited 19

river. The objectives of this study were to assess if concentrations of organic chemicals were present in quantities in 

the North Branch Au Sable River that may potentially harm 

aquatic species and to establish current baseline concentrations of organic chemicals against which future data can be 

compared. The chemical classes investigated as part of this 

study included pesticides (both legacy [organochlorine] and 

current use), polychlorinated biphenyls, polybrominated 

diphenyl ethers (PBDEs), and polycyclic aromatic hydrocarbons (PAHs).

Several organic chemicals were detected in the North 

Branch Au Sable River at low concentrations with one detection of p,p'-dichlorodiphenyldichloroethylene (21 picograms 

per liter) detected at North Branch Au Sable River at Bent 

Tree Drive exceeding the recommended U.S. Environmental 

Protection Agency Human Health Criteria standard for the 

consumption of water plus organism (of 18 picograms per 

liter). Organic chemicals were detected at every sampling 

location on the North Branch Au Sable River; however, not 

all chemicals were detected at every location. The highest number of organic chemicals were detected at the North 

Branch Au Sable River at Kellogg's Bridge (04135800), 

and the North Branch Au Sable River at The Ford Road 

(04135765), and replicate, had the second and third highest 

number of organic chemicals detected. The most frequently 

detected organic contaminants detected at all sampling locations include the legacy pesticides pentachloroanisole, transchlordane, dichlorodiphenyldichloroethylene, and dichlorodiphenyltrichloroethane; PBDEs, including polybrominated 

diphenyl ether-28; and PAHs, including 2-methylphenanthrene and perylene.

These data establish current conditions of organic chemicals in the North Branch Au Sable River against which future 

data can be compared. The organic chemical concentrations 

detected on the North Branch Au Sable River were relatively 

low and below almost all water-quality benchmarks. Further 

evaluation would be necessary to determine the effects of seasonality and precipitation on the detection of organic chemicals on the North Branch Au Sable River. Low concentrations 

of organic chemicals may still pose a risk to aquatic organisms 

and throughout the trophic food web because of low-dose 

additive and synergistic mixture effects, transgenerational 

effects, and a lack of established water-quality benchmarks 

for many organic chemicals. Some tools that could be used 

to evaluate these cumulative and synergistic mixture effects 

of chemicals include R-script ToxEval and aquatic bioassays 

to provide an ecological endpoint and additional information 

about the effect of the observed chemicals on the ecological 

community in the North Branch Au Sable River.

This dataset of organic contaminants in the North Branch 

Au Sable River provides baseline information on the current 

(2018) state of the North Branch Au Sable River and against 

which to evaluate and compare the future health of the North 

Branch Au Sable River.

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For more information about this publication, contact:

Director, USGS Upper Midwest Water Science Center 

5840 Enterprise Drive

Lansing, MI 48911–4107

517–887–8903

For additional information, visit: https://www.usgs.gov/centers/umidwater

Publishing support provided by the 

Rolla and Madison Publishing Service Centers


Brennan and Alvarez—Evaluation of Legacy and Emerging Organic Chemicals on the North Branch Au Sable River near Lovells, Michigan, June 2018—SIR 2020–5002

ISSN 2328-0328 (online)

https://doi.org/10.3133/sir20205002