Preliminary Analytic a l Resu lts for Ash and 

Burned So ils from the Octo b er 2007 Sou th ern 

C a lifornia Wild fires 

By Geoffrey S. Plumlee, Deborah A. Martin, Todd Hoefen, Raymond Kokaly, Philip 

Hageman, Alison Eckberg, Gregory P. Meeker, Monique Adams, Michael Anthony, and 

Paul J. Lamothe

Open-File Report 2007–1407

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia 2007

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Plumlee, G.S., Martin, D.A., Hoefen, T., Kokaly, R., Hageman, P., Eckberg, A., 

Meeker, G.P., Adams, M., Anthony, M., and Lamothe, P.J., 2007, Preliminary 

analytical results for ash and burned soils from the October 2007 southern 

California Wildfires: U.S. Geological Survey Open-File Report 2007-1407. 

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contained within this report.
1

Overview 

The U.S. Geological Survey (USGS) collected ash and burned soils from about 28 

sites in southern California wildfire areas (Harris, Witch, Ammo, Santiago, Canyon and 

Grass Valley) from Nov. 2 through 9, 2007 (table 1). USGS researchers are applying a 

wide variety of analytical methods to these samples, with the goal of helping identify 

characteristics of the ash and soils from wildland and suburban burned areas that may be 

of concern for their potential to adversely affect water quality, human health, endangered 

species, and debris-flow or flooding hazards. These studies are part of the Southern 

California Multi-Hazards Demonstration Project, and preliminary findings are presented 

here. 

 

Sampling and Sample Preparation 

Most samples were collected from wildland burn areas and typically include separate 

samples of ash and underlying burned soil. The goal of the wildland sampling was to 

understand potential differences in ash and soil characteristics that may result from 

differences in the type of burned vegetation and underlying bedrock geology. At a given 

site, sampling of ash and underlying soil was done by the collection and compositing of 

multiple subsamples at evenly spaced intervals along a transect or on spokes radiating 

from a centroid; such sampling has been found to produce the most statistically valid 

representation of spatially heterogeneous materials such as mine wastes (Smith and 

others, 2000).

Partly in response to a request from a Burned Area Emergency Rehabilitation 

(BAER) Team, USGS scientists collected composite samples of ash/debris and 

underlying soil from two burned residential areas within the Grass Valley and Harris 

burns. Each of these two composite residential samples consists of multiple random grab 

subsamples collected within or near multiple burned residences.

The USGS also recently acquired hyperspectral remote sensing data with the HyMap 

imaging spectrometer (Cocks and others, 1998) over several of the burned areas. The 

detailed chemical and physical properties of the ash and soil samples will be linked to the 

remote sensing data using field and laboratory reflectance measurements of the samples, 

resulting in maps that extend estimates of ash impact on environment and health across 

the burned areas.

Samples were shipped to Denver overnight. Samples were homogenized prior to 

splitting. Most sample analysis types are being conducted on a split that was obtained by 

cone-and-quartering of the full sample, and that was then sieved to less than 2mm to 

remove coarse particles.

Ash analyses completed to date have focused on the residential ash and burned soil 

samples, and to a lesser extent on wildland samples from the same burned areas. This 

initial focus is in response to the BAER team request to provide information on burned 

residences within the Grass Valley fire area. Additional analyses are intended on 

wildland ash and soil samples from other burned areas, pending funding availability. 

 
2

Analytical Methods 

Analytical methods (Taggart, 2002) performed to date on a subset of the samples 

include: 

(1) Bulk chemical composition on a ground < 2mm split using inductively coupled 

plasma-mass spectrometry (ICP-MS) for a 44-element suite. The analysis follows 

4-acid digestion of the sample; this digestion typically is considered a total 

digestion of most environmental materials. 

(2) Deionized water leach test on an unground <2mm split, to simulate interactions of 

ash with rainfall (Hageman, 2007). One part ash is added to 20 parts deionized 

water, the mixture shaken for 5 minutes, and the leachate is then filtered and 

analyzed for pH, alkalinity, conductivity, anions by ion chromatography, cations 

and metals by ICP-MS, and mercury by continuous flow injection-cold vaporatomic fluorescence spectrometry (AFS).

(3) Particle characterization using scanning electron microscopy (SEM)

Samples analyses currently in process include: X-ray diffraction for mineralogy; 

bioaccessibility of metals and metalloids in simulated biofluids; and, particle size 

distribution. If additional funding is secured, samples will also be analyzed for organic 

contaminants, microbial characteristics, and total amounts of and forms of carbon, sulfur, 

and nitrogen. 

Preliminary Findings 

Preliminary analyses of the ash and soil samples indicate several features of potential 

environmental or health concern.

(1) Water leach tests (table 2) show that the residential ash samples generate high pH 

levels (12.5–12.7). These levels suggest that ash from burned residences can 

generate caustic alkalinity when it comes into contact with rainwater or waterbased body fluids (such as perspiration or fluids lining the respiratory tract). In 

contrast, similar water leachates of the limited number of wildland ash samples 

analyzed to date generate somewhat less caustic alkalinity and lower pH (9.8–

10.9). USGS water leach tests on ash from vegetation combusted in the laboratory 

at various controlled temperatures indicate that leachate pH correlates with 

temperature of combustion, with leachate pH maximizing at 12.5 for combustion 

temperatures over 600°C (J. Crock, unpub. data). Accordingly, the higher pH and 

alkalinity of the residential ash leachates compared to wildland ash leachates might 

indicate that residential fires burned at higher temperatures than did fires in 

wildland areas; however, the combustion of diverse man-made materials in 

residences cannot be ruled out as a possible source for the high residential leachate 

pH values. 

The caustic alkalinity of exposed residential and wildland ash may diminish over 

time as it interacts with and is neutralized by rainwater and atmospheric carbon 

dioxide. However, further work is needed to determine the rate at which this 
3

neutralization may occur. High-alkalinity rainwater runoff from burned areas may 

also become neutralized as it mixes with and is diluted by sufficient quantities of 

near-neutral pH fresh water from unburned areas. 

(2) Compared to average US soils, the two residential ash samples can contain 

elevated arsenic (up to 140 parts per million, ppm or mg/kg), lead (up to 344 ppm), 

antimony (up to 32 ppm), copper (up to 1,370 ppm), or zinc (up to 2,800 ppm)

(table 3). For arsenic, lead, and antimony, concentrations in one or both of the 

residential composite ash samples approach or exceed U.S. Environmental 

Protection Agency residential soil Preliminary Remediation Goals (PRGs: 0.4–

0.62 ppm arsenic; 31 ppm antimony, 150–400 ppm lead) (EPA, 2004). Chromium 

levels are also elevated in the residential ash (up to 354 ppm); further analyses are 

underway to determine what proportion of the chromium in the residential ash is 

the more toxic hexavalent form. The EPA PRGs are “...tools for evaluating and 

cleaning up contaminated sites. They are risk-based concentrations that are 

intended to assist risk assessors and others in initial screening-level evaluations of 

environmental measurements.” (EPA, 2004). Although these PRGs were not 

designed for wildfire ash, they do provide one possible measure against which the 

chemical composition of the wildfire ash and burned soils can be preliminarily 

compared.

The water leach tests performed to date suggest that most of these metals have 

relatively low solubility under the conditions of this particular leach test; however, 

further tests are needed, as element solubilities may vary with differences in 

solid:water ratio. Results of pending physiologically based bioaccessibility tests 

using simulated gastrointestinal fluids and simulated lung fluids will provide 

insights into the potential bioaccessibility of these metals and metalloids along 

ingestion and inhalation pathways.

(3) The BAER team request for sampling and analysis of residences included a request 

to evaluate whether asbestos is present in or absent from the residential ash. 

Reconnaissance SEM analyses completed to date have not conclusively identified 

the presence of asbestos in the residential ash samples. Because the makeup of ash 

may vary substantially throughout a burned residence, and due to both the 

reconnaissance nature of our sampling within each residence and the 

reconnaissance nature of the SEM analyses of the collected samples, the negative 

finding to date for asbestos does not guarantee that asbestos is absent from the 

burned residences; it might be present locally in areas of the residences not 

sampled or analyzed. As noted by CALEPA (2003), potentially higher levels of 

asbestos (and lead) might be expected in burned residential areas with houses 

constructed earlier than the early 1980s, when use of asbestos and leaded paints in 

construction materials was common.
4

Guidance from the Findings 

These USGS findings are consistent with the scientific knowledge about wildfire ash 

that has led the California Department of Health Services (CDHS, 2003), California EPA 

(CALEPA, 2003), various California counties (i.e., San Diego County, 2007), and 

NIOSH (2007, p. 6) to issue advisories regarding appropriate precautionary measures that 

should be followed by persons working in burned wildland areas or cleaning up burned 

residences to avoid possible health problems associated with ash exposure. Such 

measures include, for example, use of appropriate respiratory protection, gloves, longsleeved shirts and long pants, dust mitigation measures, and washing of skin contacted 

by the ash. 

The USGS results further indicate that rainwater runoff from burned residential 

areas may be a source of high-alkalinity waters with possibly elevated concentrations 

of some metals or metalloids of health or environmental concern. Given the extent of 

the burned residential areas, these results suggest that residential portions of burned 

watersheds may need enhanced cleanup attention before the rains, and possibly enhanced 

monitoring during the rains. Rainwater runoff from the burned residential and wildland 

areas may also adversely affect water quality and critical species habitat in receiving 

streams by causing spikes in alkalinity, concentrations of some metals, and levels of 

some nutrients, as has been noted in burned areas elsewhere in the United States (Surber, 

2002; Meixner, 2004). 

The results also indicate that more detailed characterization of the ash and debris may 

be warranted within residential areas. In particular, more detailed characterization will 

aid in the development of appropriate disposal strategies for materials removed from 

burned residences that minimize potential metal release from the materials into landfills 

or the environment.

Results of analyses in progress will be released as they become available.

Needed Additional Studies 

The focus of the current study was primarily burned wildland areas. It is important to 

note that the two residential samples collected are not representative of all residential 

areas that burned in southern California. Therefore, additional studies are recommended 

in burned residential areas to fully examine the potential environmental and health issues 

associated with residential ash and burned soils. Needed studies include, for example (1) 

variability of ash composition within and between residences in a given neighborhood 

and (2) variability in ash composition as a function of residence age, type, and setting 

(such as north- or south-facing slope, proximity to other residences, intensity and 

duration of fire, and type of construction). 

 

Acknowledgments 

 Robert N. Fisher, Carlton Rochester, Eric Reichard, Greg Mendez, and other 

scientists from the USGS California Water Science Center office in San Diego provided 

invaluable scientific input, logistical support, and other assistance for the field sampling. 

Heather Lowers provided technical assistance with the SEM studies, and David Walters 
5

helped immensely with sample processing. James Crock, Dennis Eberl, and other 

scientists provided very helpful technical reviews on all or portions of the report.

 

USGS Contacts 

 

Geoffrey S. Plumlee, gplumlee@usgs.gov

Deborah A. Martin, damartin@usgs.gov

Todd Hoefen (field sampling), thoefen@usgs.gov

Ray Kokaly (field sampling and remote sensing), raymond@usgs.gov

Phil Hageman (leach tests), phageman@usgs.gov

Greg Meeker (SEM analysis), gmeeker@usgs.gov

Paul Lamothe (analytical chemistry), plamothe@usgs.gov

 

References 

CALEPA, 2003, Safe cleanup of fire ash: 

http://www.calepa.ca.gov/Disaster/Fire2003/FireAsh.pdf

CDHS, 2003, State health director offers advice on safe cleanup of fire ash: California 

Dept. of Health Services Press Release 03-89, 

http://www.applications.dhs.ca.gov/pressreleases/store/PressReleases/03-89.html

Cocks, T., Jenssen, R., Stewart, A., Wilson, I., and Shields, T., 1998, The HyMap 

airborne hyperspectral sensor: The system, calibration and performance, in Proceedings 

of the 1st EARSEL Workshop on Imaging Spectroscopy, Zurich.

EPA, 2004, U.S. Environmental Protection Agency, Region 9, Preliminary remediation 

goals, http://www.epa.gov/region09/waste/sfund/prg/index.html - prgtable.

Hageman, P.L., 2007, U.S. Geological Survey field leach test for assessing water 

reactivity and leaching potential of mine wastes, soils, and other geologic and 

environmental materials: U.S. Geological Survey Techniques and Methods Report 5-

D3, http://pubs.usgs.gov/tm/2007/05D03/pdf/TM5-D3_508.pdf

Meixner, T., 2004, Wildfire impacts on water quality: Southwest Hydrology, Sept./Oct. 

2004, p. 23-24, http://www.swhydro.arizona.edu/archive/V3_N5/featurette7.pdf

NIOSH, 2003, Worker safety during fire cleanup: National Institutes of Occupational 

Safety and Health Fact Sheet, 7 p., 

http://emergency.cdc.gov/disasters/wildfires/pdf/firecleanupworkers.pdf

San Diego County, 2007, Post-fire health tips and ash and debris cleanup guidance. 

http://www.sdcountyrecovery.com/documents/AshDebrisPublicHealthTipsCleanup11-

08-07.pdf
6

Smith, K.S., and Huyck, H.L.O., 1999, An overview of the abundance, relative mobility, 

bioavailability, and human toxicity of metals, Chapter 2, in Plumlee, G.S., and 

Logsdon, M.J., eds., The environmental geochemistry of mineral deposits, Part A: 

Processes, techniques, and health issues: Reviews in Economic Geology, v. 6A: 

Littleton, Colorado, Society of Economic Geologists, Inc., p. 29–70.

Smith, K.S., Ramsey, C.A., and Hageman, P.L., 2000, Sampling strategy for the rapid 

screening of mine-waste dumps on abandoned mine lands, in ICARD 2000: 

Proceedings from the Fifth International Conference on Acid Rock Drainage, Denver, 

Colorado, May 21-24, 2000: Society for Mining, Metallurgy, and Exploration, Inc., p. 

1,453-1,461.

Surber, G., 2002, Section 3, water quality concerns after wildfire, in Knight, J.E., ed., 

After wildfire—Information for landowners coping with the aftermath of wildfire: 

Montana State University Extension Service, p. 9-14, 

http://www.montana.edu/wwwpb/pubs/445503water.pdf

Taggart, J.E., Jr., ed., 2002, Analytical methods for chemical analysis of geologic and 

other materials: U.S. Geological Survey Open-File Report 02-0223, 

http://pubs.usgs.gov/of/2002/ofr-02-0223/
7

Table 1. Locations and types of samples collected in this study.

SAMPLE ID Latitude Longitude Sampling Type Location Type

Harris01 32o 37' 53.90" 116o 52' 04.08" Spoke Hilltop

Harris02W,S,A 32o 35' 46.3" 116o 46' 05.7" Opportunistic Hillside

Harris03A,B,C 32o 35' 46.3" 116o 46' 05.7" Opportunistic Tailings pile

Harris04 32o 42' 07.0" 116o 57' 36.9" Spoke Hillside near Sweetwater

Harris05 32o 42' 11.0" 116o 57' 39.8" Spoke Drainage basin near Sweetwater

Harris06 32o 39' 47.3" 116o 40' 51.2" Transect Steep hillside

Harris 07 32o 37' 22.2" 116o 41' 26.6" Random sampling Residential, mobile homes

Witch01 33o 09' 09.13" 116o 47' 00.91" Transect Steep hillside

Witch02 33o 07' 11.74" 116o 47 27.11" Transect Hillside

Witch03 33o 06' 49.4" 116o 49' 01.4" Grab Roadcut

Witch04 33o 06' 25.3" 116o 49' 37.3" Transect Hilltop

Witch05 33o 05' 2.5" 116o 59' 18.9" Transect Dried streambed

Santiago01 33o 43' 12.0" 117o 35' 54.6" Transect Sampled streambed from this point then east 150 yards

Santiago02 33o 43' 12.0" 117o 35' 54.6" Transect Sampling started and went west 140 yards in streambed

Santiago03 33o 43' 12.0" 117o 35' 54.6" Transect Sampling started and went west 140 yards on hillside

Santiago04 33o 43' 11.4" 117o 35' 59.6" Spoke Next to dried streambed

Santiago05 33o 43' 03.01" 117o 36' 37.8" Spoke Next to dried streambed

Santiago06 33o 42' 59.1" 117o 37' 13.2" Spoke Broad valley bottom

Santiago07 33o 43' 04.2" 117o 37' 15.0" Spoke Drainage draining into Santiago06 from the north

Santiago08 33o 43' 02.0" 117o 39' 34.6" Spoke Hillside

Santiago09 33o 43' 02.0" 117o 39' 34.6" Grab Potential hydrophobic soil

Ammo1 33o 22' 52.3" 117o 32' 55.4" Spoke Marine base hillside

Canyon01 34o 02' 44.0" 118o 42' 16.8" Transect Very steep hillside near Pepperdine U.

Canyon02 34o 3' 53.0" 118o 41' 50.0" Transect Steep hillside

Canyon03 34o 3' 45.5" 118o 41' 50.1 Transect Steep Hillside

Canyon04 34o 01' 57.7" 118o 42' 04.1" Transect Hillside near beach

GrassValley01 34o 16' 02.6" 117o 13' 06.0" Random Sampling Modern homes

GrassValley02 34o 16' 06.3" 117o 13' 06.6" Spoke Hillside
8

Table 2. Composition of water leachates of California wildfire ash and burned soil samples. Fluoride, chloride, and nitrate by ion chromatography; cations, metals and 

sulfate by ICP-MS; mercury by AFS. Analytical results are not blank subtracted. nr —not reported, nm—not measured.

Sampl e pH

Speci fi c 

Conduct ance 

( μS/ cm) F (mg/L ) Cl (mg/L )

N O3 

( mg/L ) Ag ( μg/L ) Al ( μg/L ) As ( μg/L )

Harris 06 Ash 10.9 890 4.3 32 4.1 <1 252 1 

Harris 06 Ash Duplicate 10.8 890 4 31.6 4.11 <1 235 2 

Grass Valley 02 Soil 8.2 140 3.2 1.2 0.9 <1 292 1 

Grass Valley 02 Ash 9.8 360 1.9 5.4 1.8 <1 4540 1 

Grass Valley 01 Soil 10.9 460 0.7 8.1 2 <1 1570 2 

Grass Valley 01 Ash 12.7 5040 <.08 70 <.08 <1 73.2 2 

Grass Valley 01 Ash (ICP-MS dup) nm nm nm nm nm <1 75.1 1 

Harris 07 Soil 10.6 240 1.2 25.3 1 <1 975 219 

Harris 07 Ash 12.5 3950 3 285 13.5 <1 3650 13.5 

Blank 6 0.77 <.08 <.08 <.08 <1 3.8 <1

Sampl e Ba ( μg/L ) Be ( μg/L ) Bi ( μg/L )

 Ca 

( mg/L ) Cd ( μg/L ) Ce ( μg/L ) Co ( μg/L ) Cr (μg/L )

Harris 06 Ash 109 <0.05 <0.2 21.2 0.03 <0.01 0.33 1.5 

Harris 06 Ash Duplicate 116 <0.05 <0.2 25.0 0.04 <0.01 0.38 1.5 

Grass Valley 02 Soil 29.3 <0.05 <0.2 20.5 <0.02 0.54 0.43 <1

Grass Valley 02 Ash 254 <0.05 <0.2 41.2 <0.02 <0.01 0.24 1.4 

Grass Valley 01 Soil 21.3 <0.05 <0.2 63.2 <0.02 0.03 0.10 7.7 

Grass Valley 01 Ash 158 <0.05 0.21 668 0.05 <0.01 0.28 31.9 

Grass Valley 01 Ash (ICP-MS dup) 153 0.06 <0.2 629 0.06 <0.01 0.48 32.7 

Harris 07 Soil 28.3 <0.05 <0.2 24.5 0.04 0.08 0.24 3.0 

Harris 07 Ash 1670 <0.05 <0.2 427 0.06 <0.01 <0.02 32.4 

Blank 0.41 <0.05 <0.2 <0.2 <0.02 <0.01 <0.02 <1
9

Table 2—Conti nued.

Sampl e Cs (μg/L ) Cu ( μg/L ) Dy ( μg/L ) Er ( μg/L ) Eu ( μg/L ) Fe ( μg/L ) Ga ( μg/L ) Gd ( μg/L )

Harris 06 Ash 0.24 23.9 <0.005 <0.005 0.02 <50 0.68 <0.005

Harris 06 Ash Duplicate 0.25 23.3 <0.005 <0.005 0.02 <50 0.60 <0.005

Grass Valley 02 Soil <0.02 2.6 0.04 0.02 0.02 50 0.31 0.04 

Grass Valley 02 Ash 0.05 4.5 <0.005 <0.005 0.03 <50 1.7 <0.005

Grass Valley 01 Soil <0.02 2.8 <0.005 <0.005 <0.005 <50 1.3 0.005 

Grass Valley 01 Ash 0.32 8.9 <0.005 <0.005 0.02 <50 0.38 <0.005

Grass Valley 01 Ash (ICP-MS dup) 0.32 10.0 0.009 <0.005 0.03 <50 0.39 <0.005

Harris 07 Soil <0.02 10.4 0.01 <0.005 0.005 <50 0.96 0.009 

Harris 07 Ash 0.89 8.7 <0.005 <0.005 0.21 <50 4.5 <0.005

Blank <0.02 <0.5 <0.005 <0.005 <0.005 <50 <0.05 0.005 

Sampl e Ge ( μg/L ) Hg ( ng/L ) Ho ( μg/L ) K (mg/L ) La ( μg/L ) Li ( μg/L ) Lu ( μg/L )

 Mg 

( mg/L )

Harris 06 Ash 0.07 25 <0.005 nr <0.01 12.4 <0.1 7.13 

Harris 06 Ash Duplicate 0.08 21 <0.005 nr <0.01 13.1 <0.1 10.7 

Grass Valley 02 Soil <0.05 6 0.007 3.55 0.28 <0.1 <0.1 1.38 

Grass Valley 02 Ash 0.06 8 <0.005 14.6 <0.01 20.9 <0.1 6.05 

Grass Valley 01 Soil <0.05 <5 <0.005 5.99 0.02 0.4 <0.1 0.37 

Grass Valley 01 Ash <0.05 <5 <0.005 14.3 <0.01 12.4 <0.1 0.02 

Grass Valley 01 Ash (ICP-MS dup) <0.05 nm <0.005 14.2 <0.01 13.5 <0.1 0.04 

Harris 07 Soil 0.09 <5 <0.005 3.32 0.04 5.9 <0.1 0.85 

Harris 07 Ash <0.05 <5 <0.005 41.6 0.01 41.3 <0.1 0.03 

Blank <0.05 <5 <0.005 0.06 <0.01 0.6 <0.1 <0.01
10

Table 2—Conti nued.

Sampl e Mn ( μg/L ) Mo ( μg/L ) 

 N a 

( mg/L ) 

 N b 

( μg/L ) 

 N d 

( μg/L ) Ni ( μg/L ) P (mg/L ) Pb ( μg/L ) 

Harris 06 Ash 2.6 21.4 8.91 0.72 <0.01 2.0 0.1 0.2 

Harris 06 Ash Duplicate 3.1 18.7 9.66 <0.2 <0.01 2.0 0.1 0.3 

Grass Valley 02 Soil 172 <2 0.54 0.20 0.23 1.5 0.3 0.5 

Grass Valley 02 Ash 16.9 10.1 0.84 <0.2 <0.01 2.1 0.02 0.3 

Grass Valley 01 Soil 1.3 3.0 6.98 <0.2 0.01 0.8 0.02 0.4 

Grass Valley 01 Ash 0.3 19.5 25.7 0.31 <0.01 7.1 <0.01 157 

Grass Valley 01 Ash (ICP-MS dup) 0.4 18.7 25.4 <0.2 <0.01 11.5 <0.01 163 

Harris 07 Soil 4.1 4.6 9.10 <0.2 0.04 1.4 0.1 0.56 

Harris 07 Ash 0.4 26.7 97.4 <0.2 <0.01 2.9 <0.01 37.8 

Blank 0.3 <2 0.26 <0.2 <0.01 <0.4 <0.01 0.2 

Sampl e Pr (μg/L ) Rb ( μg/L ) Sb ( μg/L ) Sc ( μg/L ) Se ( μg/L ) 

 SiO2 

( mg/L ) 

 Sm 

( μg/L ) 

SO4 

( mg/L ) 

Harris 06 Ash <0.01 49.6 8.61 1.1 7.2 7.8 <0.01 170 

Harris 06 Ash Duplicate <0.01 49.6 6.88 0.9 7.3 7.9 <0.01 188 

Grass Valley 02 Soil 0.06 2.94 4.84 <0.6 <1 0.9 0.04 8 

Grass Valley 02 Ash <0.01 9.22 7.15 <0.6 3.1 1.1 <0.01 105 

Grass Valley 01 Soil <0.01 2.30 9.89 <0.6 1.6 1.8 <0.01 187 

Grass Valley 01 Ash <0.01 20.8 3.07 <0.6 3.6 1.8 <0.01 986 

Grass Valley 01 Ash (ICP-MS dup) <0.01 21.2 2.43 0.8 3.4 1.8 <0.01 941 

Harris 07 Soil <0.01 1.74 27.5 <0.6 2.7 3.2 <0.01 18 

Harris 07 Ash <0.01 59.2 4.10 <0.6 6.3 3.1 <0.01 107 

Blank <0.01 0.03 1.07 <0.6 <1 <0.2 <0.01 <2
11

Table 2—Conti nued.

Sampl e Sr (μg/L ) Ta ( μg/L ) Tb ( μg/L ) Th ( μg/L ) Ti ( μg/L ) Tl ( μg/L ) 

 Tm 

( μg/L ) U ( μg/L ) 

Harris 06 Ash 218 0.85 <0.005 <0.2 2.8 <0.1 <0.005 <0.1

Harris 06 Ash Duplicate 232 0.23 <0.005 <0.2 2.5 <0.1 <0.005 0.10 

Grass Valley 02 Soil 198 0.42 0.006 <0.2 2.7 <0.1 <0.005 0.47 

Grass Valley 02 Ash 797 0.20 <0.005 <0.2 1.7 <0.1 <0.005 1.04 

Grass Valley 01 Soil 236 0.05 <0.005 <0.2 2.9 <0.1 <0.005 <0.1

Grass Valley 01 Ash 1160 0.28 <0.005 <0.2 13.5 <0.1 <0.005 <0.1

Grass Valley 01 Ash (ICP-MS dup) 1160 0.34 <0.005 <0.2 13.6 <0.1 <0.005 <0.1

Harris 07 Soil 69.5 0.1 <0.005 <0.2 2.6 <0.1 <0.005 0.32 

Harris 07 Ash 748 <0.02 <0.005 <0.2 1.7 <0.1 <0.005 <0.1

Blank <0.5 <0.02 <0.005 <0.2 <0.5 <0.1 <0.005 <0.1

Sampl e V ( μg/L ) W ( μg/L ) Y ( μg/L ) Yb ( μg/L ) Zn ( μg/L ) 

Harris 06 Ash 39.2 1.88 0.01 0.005 3.6 

Harris 06 Ash Duplicate 33.3 1.43 0.01 0.005 2.9 

Grass Valley 02 Soil 3.6 <0.5 0.22 0.01 5.2 

Grass Valley 02 Ash 6.8 1.93 0.07 <0.005 3.3 

Grass Valley 01 Soil 16.4 <0.5 0.01 <0.005 1.9 

Grass Valley 01 Ash 10.0 0.62 0.07 <0.005 154 

Grass Valley 01 Ash (ICP-MS dup) 10.1 0.50 0.01 0.01 168 

Harris 07 Soil 16.9 0.87 0.04 0.008 6.1 

Harris 07 Ash 4.0 2.43 0.09 <0.005 71.4 

Blank <0.5 <0.5 <0.01 0.005 9.4 
12

Table 3. Bulk chemical composition of selected California wildfire ash and burned soil samples, as determined by ICP-MS. EPA residential soil preliminary 

remediation goals vary for chromium, depending upon the proportion of hexavalent chromium (VI) compared to trivalent chromium (III) present.

Sampl e Ag ppm Al ppm As ppm Ba ppm Be ppm Bi ppm Ca ppm Cd ppm Ce ppm

Detection Limit < 1 < 50 < 1 < 0.2 < 0.03 < 0.06 < 100 < 0.007 < 0.1

Harris07-soil 3.4 80400 49.4 660 1.3 0.40 29300 2.1 43.1 

Harris07-ash 8.5 76000 140 858 0.92 0.54 130000 4.8 35.2 

Grass Valley-01soil < 1 93200 4.0 892 2.1 0.13 42400 0.16 85.0 

Grass Valley-01ash 0.96 40800 17.9 541 1.0 0.27 191000 1.0 29.4 

EPA Region IX residential soil 

preliminary remediation goals 

(EPA, 2004) 390 76000 0.39–0.62 5400 150 37

Western US soil mean (Smith 

and Huyck, 1999). *US mean. 0.05* 58000 5.5 580 0.68 18000 0.06* 65

Sampl e Co ppm Cr ppm Cs ppm Cu ppm Fe ppm Ga ppm K ppm La ppm Li ppm

Detection Limit < 0.03 < 0.5 < 0.003 < 2 < 50 < 0.02 < 20 < 0.05 < 0.3

Harris07-soil 11.2 55.9 2.0 471 40400 17.4 16800 23.3 14.8 

Harris07-ash 12.2 91.1 1.8 1120 23600 15.9 16300 19.8 19.0 

Grass Valley-01soil 17.2 175 3.4 404 49900 21.7 23100 54.6 33.9 

Grass Valley-01ash 27.3 354 1.4 1370 51200 8.9 11400 16.9 14.2 

EPA Region IX residential soil 

preliminary remediation goals 

(EPA, 2004) 900

210 (1/6 VI/III), 

30 (all VI), 100000 

(all III) 3100 23000 1600

Western US soil mean (Smith 

and Huyck, 1999). *US mean. 7.1 41 6* 21 21000 16 18000 30 22
13

Table 3—Conti nued. 

Sampl e Mg ppm Mn ppm Mo ppm N a ppm N b ppm N i ppm P ppm Pb ppm Rb ppm Sb ppm

Detection Limit < 6 < 0.7 < 0.05 < 20 < 0.1 < 0.3 < 5 < 0.4 < 0.01 < 0.04

Harris07-soil 10200 727 0.86 26600 10 14.0 1080 62.9 58.9 8.6 

Harris07-ash 10800 774 3.5 21300 12 41.6 1540 192 58.3 31.5 

Grass Valley-01soil 15400 867 8.3 12700 26 14.1 1030 162 122 5.1 

Grass Valley-01ash 7840 396 73.0 9360 10 36.6 509 344 47.2 24.9 

EPA Region IX residential 

soil preliminary remediation 

goals (EPA, 2004) 1800 390 1600 150–400 31

Western US soil mean 

(Smith and Huyck, 1999). 

*US mean. 7400 380 0.85 9700 8.7 15 320 17 69 0.47

Sampl e Sc ppm Sr ppm Th ppm Ti ppm Tl ppm U ppm V ppm Y ppm Zn ppm

Detection Limit < 0.04 < 0.8 < 0.1 < 40 < 0.08 < 0.02 < 0.2 < 0.05 < 3

Harris07-soil 18.6 199 9.42 5120 0.36 2.13 100 41.1 458 

Harris07-ash 10.4 277 5.76 22500 0.38 2.23 67.8 26.0 2220 

Grass Valley-01soil 13.7 398 9.31 6730 0.70 3.15 127 29.4 211 

Grass Valley-01ash 5.3 392 5.15 6900 0.32 1.89 54.0 15.5 2800 

EPA Region IX residential 

soil preliminary 

remediation goals (EPA, 

2004) 47000 5.2 16 78 23000

Western US soil mean 

(Smith and Huyck, 1999). 

*US mean. 8.2 200 9.1 2200 2.5 70 22 55