BIOACCUMULATION OF TOTAL AND MONOMETHYLMERCURY IN EARTHWORMS AND THE ECOLOGICAL RISKS TO BIRDS AND MAMMALS

• Sponsoring Institution: National Institute of Food and Agriculture
• Project Status: COMPLETE
• Funding Source: HATCH
• Reporting Frequency: Annual
• Accession No.: 0195342
• Project Start Date: Jul 1, 2003
• Project End Date: Jun 30, 2008
• Program Code: [(N/A)]- (N/A)

Recipient Organization
UNIV OF MARYLAND
(N/A)
COLLEGE PARK,MD 20742

Performing Department
WYE RES & EDUCATION CENTER

Non Technical Summary
A Heavy metals are common contaminants in agricultural soils B Little work has been conducted on mercury or the accumulation of monomethylmercury in earthworms. C The ecological risk to birds and mammals that feed on mercury-contaminated earthworms is not well understood. A This project will determine the bioaccumulation of total mercury and monomethylmercury in earthworms exposed to mercury-contaminated soils. B The ecological risks to birds and mammals that feed on earthworms exposed to mercury will also be determined.

Animal Health Component

50%

Research Effort Categories

Basic

50%

Applied

50%

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
133	3199	1070	20%
135	0820	1070	30%
314	0820	1150	50%

Knowledge Area
135 - Aquatic and Terrestrial Wildlife; 133 - Pollution Prevention and Mitigation; 314 - Toxic Chemicals, Poisonous Plants, Naturally Occurring Toxins, and Other Hazards Affecting Animals;

Subject Of Investigation
0820 - Wild birds; 3199 - Invertebrates, general/other;

Field Of Science
1070 - Ecology; 1150 - Toxicology;

Keywords

mercury

earthworms

nutrient accumulation

nutrient uptake

birds

toxicity

risk assessment

environmental impact

wildlife food

pollution control

soil contamination

invertebrates

food chains

screening

ecology

toxicology

shrews

diet

dietary levels

methyl mercury

Goals / Objectives
The primary objective of this study is to determine the uptake and depuration kinetics of total mercury (T-Hg) and monomethylmercury (MMHg) in an earthworm exposed to three mercury-contaminated soils. Three soils containing a high (~15 mg T-Hg/kg dry wt. soil), intermediate (~7.5 mg T-Hg/kg dry wt. soil), and low (~1 mg T-Hg/kg dry wt. soil) concentration of mercury will be studied to adequately characterize the uptake and depuration rate constants and associated kinetic data (i.e., time to 90% steady state and time to 50% clearance). The uptake (k1) and depuration (k2) rate constants will be used to determine the bioaccumulation factors (BAFs). The BAFs will be used in a screening-level ecological risk assessment (ERA) to determine the risk to a representative bird (American robin) and mammal (short-tailed shrew) that feed on earthworms exposed to mercury. Two scenarios will be used in the ERA for the proportion of the diet consisting of earthworms. The first will assume that 100% of the robin's and shrew's total diet is comprised of contaminated earthworms. The second scenario will assume a more realistic diet using dietary information taken from the scientific literature.

Project Methods
The earthworm Eisenia fetida will be exposed to three mercury-contaminated soils containing a high (~15 mg T-Hg/kg dry wt. soil), intermediate (~7.5 mg T-Hg/kg dry wt. soil), and low (~1 mg T-Hg/kg dry wt. soil) concentration of mercury. A reference soil will be taken from a non-contaminated area of the same soil type. Bioaccumulation will be determined by the steady state method. The experimental design will consist of a 28-d uptake phase in the three contaminated soils and reference soil followed by a 28-d depuration phase in reference soil only. During the uptake phase, four randomly selected replicates of 10 earthworms/replicate will be analyzed for T-Hg and MMHg in each contaminated soil and reference soil at days 1, 2, 4, 7, 14, 21, and 28. Four randomly selected replicates of 10 earthworms/replicate will be analyzed for T-Hg and MMHg from each contaminated soil and reference soil at days 35, 42, 49, and 56 during the depuration phase. At each sample period, the earthworms in each replicate will be counted (to determine survival), their guts purged for 24 hours, and weighed. At the end of the 28-day uptake phase, the earthworms in each remaining replicate will be counted, their guts purged for 24 hours, and weighed. The earthworms will then be placed in unused reference soil (soil replicates prepared from the original reference soil and sampled at the frequency described above during the 28-day depuration phase. The bioaccumulation of T-Hg and MMHg in the earthworms will be estimated using BIOFAC which is a regression model that treats each organism as a one-compartment model The uptake and depuration rate constants will be used to calculate the bioaccumulation factors (BAFs) of both T-Hg and MMHg. In addition to the uptake and depuration rate constants and the BAFs, BIOFAC will also be used to estimate time to reach 90% steady state and 50% clearance of the chemicals. To test the assumption that the shape of the curves are the same among treatments (i.e., the rate kinetics are essentially the same at different soil concentrations), a model will be constructed for the logarithm of mercury concentration (both T-Hg and MMHg) using linear and quadratic terms to form a low order polynomial of the logarithm of concentration. The effect of mercury on growth in both the uptake and depuration phases, will be analyzed by analysis of covariance. A screening-level ecological risk assessment (ERA) of monomethylmercury to the robin and shrew will be conducted. Total mercury will only be considered if the BAF is >1. The ERA with monomethylmercury will be conducted following the procedures given in the U.S. Environmental Protection Agency's (EPA) ecological risk assessment guidance for superfund sites and EPA's Risk Assessment Forum guidelines for ecological risk assessment. The ERA will include the following steps: problem formulation, exposure assessment, effects assessment, risk characterization, and associated uncertainties.

Progress 07/01/03 to 06/30/08

Outputs
OUTPUTS: The bioaccumulation factors (BAFs; see Outcomes/Impacts section) established for monomethylmercury and total mercury in a representative earthworm (Eisenia fetida) exposed to contaminated field soils are currently being used by both State (e.g., Maryland Department of the Environment) and Federal (e.g., U.S. Environmental Protection Agency) regulatory agencies in various ecological risk assessments. The experimental work to establish the BAFs has been presented at various Federal agencies (e.g., U.S. Army Environmental Protection Agency and U.S. Army Corp of Engineers); the Society of Environmental Toxicology and Chemistry; and various academic seminars. The uptake and depuration rate constants and associated kinetic data used to establish the BAFs were published in the following peer reviewed journal: Burton, Dennis T., Steven D. Turley, Daniel J. Fisher, Donald J. Green, and Tommy R. Shedd. 2006. Bioaccumulation of total mercury and monomethylmercury in the earthworm Eisenia fetida. Water, Air, Soil Pollut. 170:37-54. PARTICIPANTS: Dr. Dennis Burton was Principal Investigator of the study. He designed the experimental work, wrote the technical reports and peer reviewed publication; presented the results to various State and Federal agencies, the Society of Environmental Toxicology and Chemistry; and various academic seminars. Mr. Steven Turley was the Research Associate responsible for conducting the majority of laboratory experiments. Dr. Elgin Perry assisted Dr. Burton in the statistical and modeling analyses. Dr. Daniel Fisher assisted in the interpretation of the uptake (k1) and depuration (k2) rate constants. The U.S. Army Aberdeen Proving Ground, Aberdeen, Maryland, provided study sites and logistic support for the study. TARGET AUDIENCES: The uptake (k1) and depuration (k2) rate constants were used to establish bioaccumulation factors (BAFs) in the earthworm. The BAFs were used in a ecological risk assessment (ERA) to determine the risk to a representative bird (American robin) and mammal (short-tailed shrew) that feed on earthworms exposed to mercury. The BAFs established for monomethylmercury and total mercury are currently being used by both State (e.g., Maryland Department of the Environment) and Federal (e.g., U.S. Environmental Protection Agency) regulatory agencies in various ecological risk assessments. PROJECT MODIFICATIONS: No major changes were made during the study.

Impacts
The study provided definitive uptake and depuration rate constants and associated kinetic data (i.e., time to 90% steady state and time to 50% clearance) for monomethylmercury and total mercury in a representative earthworm (Eisenia fetida) exposed to contaminated field soils. The uptake (k1) and depuration (k2) rate constants were used to establish bioaccumulation factors (BAFs) in the earthworm. The BAFs were used in an ecological risk assessment (ERA) to determine the risk to a representative bird (American robin) and mammal (short-tailed shrew) that feed on earthworms exposed to mercury. Two scenarios were used in the ERA for the proportion of the diet consisting of earthworms. The first assumed that 100% of the robin's and shrew's total diet was comprised of contaminated earthworms. The second scenario assumed a more realistic diet using dietary information taken from the scientific literature. Prior to this work, State and Federal regulatory agencies had no experimental BAFs for monomethylmercury and total mercury in earthworms for use in various ecological risk assessments

Publications

• Burton, Dennis T. and Steven J. Turley. 2007. Bioaccumulation of total and monomethylmercury in earthworms and the ecological risk to birds and mammals at the Northeast Test Hut, Graces Quarters, Aberdeen Proving Ground, Maryland. Distribution No. 3552-A-6, Aberdeen Proving Ground, Aberdeen, Maryland 139 pp.
• Burton, Dennis T., Steven J. Turley, and Daniel J. Fisher. 2005. Bioaccumulation of total and monomethylmercury in earthworms at the Northeast Test Hut, Graces Quarters, Aberdeen Proving Ground, Maryland. AD-A454699. Defense Technical Information Center, Alexandria, Virginia. 106 pp.
• Burton, Dennis T. and Steven D. Turley. 2005. Survival and bioaccumulation of lead and total mercury in the earthworm, Eisenia fetida, exposed to contaminated soil from the Old Pistol Range, Camp H.M. Smith, Oahu, Hawaii. Report No. 205501, U.S. Army Camp H.M. Smith, Oahu, Hawaii. 30pp.
• Burton, Dennis T. and Steven D. Turley. 2006. Mercury bioaccumulation in yellow perch (Perca flavescens) taken from Allens Fresh Run and Mattawoman Creek, Maryland. Report No. SVMA-6200. Mirant Mid-Atlantic LLC, Upper Marlboro, Maryland. 29pp.
• Burton, Dennis T., Steven D. Turley, Daniel J. Fisher, Donald J. Green, and Tommy R. Shedd. 2006. Bioaccumulation of total mercury and monomethylmercury in the earthworm Eisenia fetida. Water, Air, Soil Pollut. 170:37-54.

Progress 01/01/07 to 12/31/07

Outputs
The research project was funded July 1, 2003. The period from July 1, 2003 to December 31, 2003 was spent setting up and calibrating a cold vapor atomic fluorescence spectrophotometry system used in the analysis of total mercury (T-Hg) and monomethylmercury (MMHg). The period from January 1, 2004 to December 31, 2004 was used to establish background concentrations of T-Hg and MMHg in the earthwrm Eisenia fetida reared in peat moss from various sources and the concentrations of mercury in various soils sampled in the 1-15 cm surface horizon. Both T-Hg and MMHg were found in the earthworm reared in peat moss from all sources investigated and all sample soils. The period from January 1, 2005 to December 31, 2005 was spent conducting bioaccumulation studies (28-d uptake phase followed by a 14-d elimination phase) in Mattapeake/Mattapex soil containing three concentrations of both metal species. Data on uptake rates, elimination rates, and bioaccumulation factors were collected from Eisenia exposed to each of the three contaminated soils. The period from January 1, 2006 to December 31, 2006 was spent completing the analysis of the data and writing a manuscript for a peer review journal. The period from January 1, 2007 to December 31, 2007 was spent developing a T-Hg and MMHg data base for an ecological risk assessment.

Impacts
Determine the uptake and depuration kinetics of total mercury and monomethylmercury in an earthworm exposed to mercury-contaminated soils. The data will ultimately be used in a screening-level ecological risk assessment using the robin and shrew as a "representative" bird and mammal.

Publications

• Burton, Dennis T., Steven D. Turley, Daniel J. Fisher, Donald J. Green, and Tommy R. Shedd. 2006. Bioaccumulation of total mercury and monomethylmercury in the earthworm Eisenia fetida. Water, Air, Soil Pollut. 170:37-54.

Progress 01/01/06 to 12/31/06

Outputs
The research project was funded July 1, 2003. The period from July 1, 2003 to December 31, 2003 was spent setting up and calibrating a cold vapor atomic fluorescence spectrophotometry system used in the analysis of total mercury (T-Hg) and monomethylmercury (MMHg). The period from January 1, 2004 to December 31, 2004 was used to establish background concentrations of T-Hg and MMHg in the earthwrm Eisenia fetida reared in peat moss from various sources and the concentrations of mercury in various soils sampled in the 1-15 cm surface horizon. Both T-Hg and MMHg were found in the earthworm reared in peat moss from all sources investigated and all sample soils. The period from January 1, 2005 to December 31, 2005 was spent conducting bioaccumulation studies (28-d uptake phase followed by a 14-d elimination phase) in Mattapeake/Mattapex soil containing three concentrations of both metal species. Data on uptake rates, elimination rates, and bioaccumulation factors were collected from Eisenia exposed to each of the three contaminated soils. The period from January 1, 2006 to December 31, 2006 was spent completing the analysis of the data and writing a manuscript for a peer review journal. The manuscript was accepted for publication.

Impacts
Determine the uptake and depuration kinetics of total mercury and monomethylmercury in an earthworm exposed to mercury-contaminated soils. The data will ultimately be used in a screening-level ecological risk assessment using the robin and shrew as a "representative" bird and mammal.

Publications

• Burton, Dennis T., Steven D. Turley, Daniel J. Fisher, Donald J. Green, and Tommy R. Shedd. 2006. Bioaccumulation of total mercury and monomethylmercury in the earthworm Eisenia fetida. Water, Air, Soil Pollut. 170:37-54.

Progress 01/01/05 to 12/31/05

Outputs
The research project was funded July 1, 2003. The period from July 1, 2003 to December 31, 2003 was spent setting up and calibrating a cold vapor atomic fluorescence spectrophotometry system used in the analysis of total mercury (T-Hg) and monomethylmercury (MMHg). The period from January 1, 2004 to December 31, 2004 was used to establish background concentrations of T-Hg and MMHg in the earthworm Eisenia fetida reared in peat moss from various sources and the concentrations of mercury in various soils sampled in the 1-15 cm surface horizon. Both T-Hg and MMHg were found in the earthworm reared in peat moss from all sources investigated and all sample soils. The period from January 1, 2005 to December 31, 2005 was spent conducting bioaccumulation studies (28-d uptake phase followed by a 14-d elimination phase) in Mattapeake/Mattapex soil containing three concentrations of both metal species. Data on uptake rates, elimination rates, and bioaccumulation factors were collected for Eisenia exposed to each of the three contmainated soils.

Impacts
Determine the uptake and depuration kinetics of total mercury and methylmercury in an earthworm exposed to mercury-contaminated soils. The data will ultimately be used in a screening-level ecological risk assessment using the robin and shrew as a "representative" bird and mammal.

Publications

• No publications reported this period

Progress 01/01/04 to 12/30/04

Outputs
The research project was funded July 1, 2003. The period from July 1, 2003 to December 31, 2003 was spent setting up and calibrating a cold vapor atomic fluorescence spectophotometry system used in the analysis of total mercury (T-Hg) and monomethylmercury (MMHg). The period from January 1, 2004 to December 31, 2004 was used to establish background concentrations of T-Hg and MMHg in the earthworm Eisenia fetida reared in peat moss from various sources. Both T-Hg and MMHg were found in the earthworm reared in peat moss from all sources investigated.

Impacts
Determine the uptake and depuration kinetics of total mercury and methylmercury in an earthworm exposed to mercury-contaminated soils. The data will ultimately be used in a screening-level ecological risk assessment using the robin and shrew as a "representative" bird and mammal.

Publications

• No publications reported this period

Progress 01/01/03 to 12/31/03

Outputs
The research project was funded July 1, 2003. The first six months of the project were spent setting up and calibrating a cold vapor atomic fluorescence spectophotometry system to be used in the analysis of total mercury and methylmercury.

Impacts
Determine the uptake and depuration kinetics of total mercury and methylmercury in an earthworm exposed to mercury-contaminated soils. The data will ultimately be used in a screening-level ecological risk assessment using the robin and shrew as a "representative" bird and mammal.

Publications

• No publications reported this period