Inorganic Analysis

EPA Grant Number: R825433C041
Subproject: this is subproject number 041 , established and managed by the Center Director under grant R825433
(EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).

Center: EERC - Center for Ecological Health Research (Cal Davis)
Center Director: Rolston, Dennis E.
Title: Inorganic Analysis
Investigators: Burau, Richard
Institution: University of California - Davis
EPA Project Officer: Levinson, Barbara
Project Period: October 1, 1996 through September 30, 2000
RFA: Exploratory Environmental Research Centers (1992) RFA Text |  Recipients Lists
Research Category: Center for Ecological Health Research , Targeted Research


This project seeks to analyze water samples for arsenic and selenium by hydride generation atomic absorption spectrometry (HGAAS); studies the chemistry and the chemical remediation of acidic waters which may accelerate weathering of cinnabar into adsorbed mercury; estimates the size of this compartment as an accessible source for further biological interaction.


Speciation of mercury in the water column. Clear Lake water quality as well as total mercury data were obtained from the Clear Lake Research Laboratory. A site-specific, iterative spreadsheet program was created to perform the simultaneous equilibrium calculations given pH and ionic strength. The computations were performed over a range of redox potential that might exist in reduced as well as oxidized zones (pe 3 -- 8). The results showed only two species were important: elemental mercury and un-charged mercuric hydroxide. The calculations showed these two species to be equal in concentration at pe 5.9. Mercuric ion concentration was 6 to 10 orders of magnitude below these two species. Dimeric mercurous ion concentrations were 3 to 10 orders of magnitude less than mercuric ion.

These findings are important because the inorganic species of mercury present in the highest concentration are uncharged potentially facilitating membrane transport. Second, they suggest that a significant proportion of the inorganic mercury in solution is in a form which can be volatilized to the atmosphere. Therefore, not only can mercury be volatilized from the system as dimethylmercury but also as elemental mercury.

Labile Mercury Pool Size. A primary form of contamination of Clear Lake is cinnabar from the Sulfur Bank Mine. This material is extraordinarily insoluble in water but it is subject to weathering by microbiological oxidation of sulfur to H2SO4 with the release of mercuric ion to the aqueous environment. In sediments, it is very likely that a majority of mercuric mercury is adsorbed to humates. Undoubtedly additional local bonding to other functional groups in the same and adjacent molecules explain the capacity and energy of the adsorption in organic rich sediments. With time, the cinnabar pool diminishes in size and the adsorbed pool increases. There is a possibility that this (adsorbed) pool is labile, i.e., capable of passing from this form into solution where it can be acquired by microorganisms which methylate and excrete it for further biological interaction. The mercury pools in sediments have already been characterized as to methylation rate under standard conditions. The techniques to study labile pool size more directly include extractions with polyaminocarboxylates that have been used to characterize adsorption chemistry of metals such as cadmium, lead, copper, cobalt, zinc, etc., as well as thiocarbazones and thiocarbamates which have S(II) in molecular locations that produce very energetic associations with chalcophyllic elements such as mercury. Chelates as solid phase extractants have advantages over strong acids in that little of the solid phase is decomposed.

The Clear lake Research Laboratory collected Clear Lake sediment samples (OA: Oaks Arm, NR: Narrows, UA: Upper Arm). For a control, investigators used a YOLO soil (surface, sampled at the experiment station on campus) The extracts were analyzed by cold vapor atomic absorption spectrophotometry with a limit of detection of 0.3 microgram Hg per liter. Below is a table summarizing the average results on the sediment samples from Clear Lake and the control:

Expected Results:

The theory underlying this extraction is to provide a high concentration of bromide, a strong mercury complexing anion, so that most (> 99 percent) is present as the uncomplexed (free) ion. The concentration selected (0.1 M) is in a range where equilibrium calculations are possible. A further assumption in such a system is that the measured mercury in the extract is mostly (> 99 percent) present as bromide complexes. An advantage of the process is that the complexing can desorb mercury into solution thus raising the concentration above water extraction values so that mercury detection can be less sensitive. It is then possible to derive an expression for the sum or total concentration of mercury species in solution (mercuric ion, and the four bromide complexes: mercuric monobromide, mercuric dibromide, mercuric tribromide and mercuric tetrabromide). By substitution of the equilibrium expressions and the known values for free bromide and total mercury in solution, it is possible to rearrange the expression to calculate the activity or concentration of free mercuric ion. This calculation shows that concentration to be less than approximately 1 E-25 all the sample extracts. The data cannot be used to calculate the magnitude of the labile pool of mercury but they imply that the value is quite small even in the Oaks Arm samples where there is a high concentration of total mercury in the sediments.

Supplemental Keywords:

Watershed, aquatic ecosystem restoration, Clear Lake, spectrometry studies, chemical remediation, mercury, arsenic., RFA, Scientific Discipline, Water, Ecosystem Protection/Environmental Exposure & Risk, POLLUTANTS/TOXICS, Chemical Engineering, Environmental Chemistry, Restoration, Arsenic, Analytical Chemistry, Monitoring/Modeling, Environmental Monitoring, Ecology and Ecosystems, Water Pollutants, Engineering, Chemistry, & Physics, Aquatic Ecosystem Restoration, hydroxyl radical, aquatic ecosystem, trace organic identification, mass spectrometry, hydride generation atomic absorption spectrometry, MTBE, pesticides, gas chromatography, arsenic removal, acuatic ecosystems, ecological recovery, ecological risk, pesticide residue, aquatic ecosystems, chemical remediation, chemical remdiation, inorganic analysis

Progress and Final Reports:

1999 Progress Report

Main Center Abstract and Reports:

R825433    EERC - Center for Ecological Health Research (Cal Davis)

Subprojects under this Center: (EPA does not fund or establish subprojects; EPA awards and manages the overall grant for this center).
R825433C001 Potential for Long-Term Degradation of Wetland Water Quality Due to Natural Discharge of Polluted Groundwater
R825433C002 Sacramento River Watershed
R825433C003 Endocrine Disruption in Fish and Birds
R825433C004 Biomarkers of Exposure and Deleterious Effect: A Laboratory and Field Investigation
R825433C005 Fish Developmental Toxicity/Recruitment
R825433C006 Resolving Multiple Stressors by Biochemical Indicator Patterns and their Linkages to Adverse Effects on Benthic Invertebrate Patterns
R825433C007 Environmental Chemistry of Bioavailability in Sediments and Water Column
R825433C008 Reproduction of Birds and mammals in a terrestrial-aquatic interface
R825433C009 Modeling Ecosystems Under Combined Stress
R825433C010 Mercury Uptake by Fish
R825433C011 Clear Lake Watershed
R825433C012 The Role of Fishes as Transporters of Mercury
R825433C013 Wetlands Restoration
R825433C014 Wildlife Bioaccumulation and Effects
R825433C015 Microbiology of Mercury Methylation in Sediments
R825433C016 Hg and Fe Biogeochemistry
R825433C017 Water Motions and Material Transport
R825433C018 Economic Impacts of Multiple Stresses
R825433C019 The History of Anthropogenic Effects
R825433C020 Wetland Restoration
R825433C021 Sierra Nevada Watershed Project
R825433C022 Regional Transport of Air Pollutants and Exposure of Sierra Nevada Forests to Ozone
R825433C023 Biomarkers of Ozone Damage to Sierra Nevada Vegetation
R825433C024 Effects of Air Pollution on Water Quality: Emission of MTBE and Other Pollutants From Motorized Watercraft
R825433C025 Regional Movement of Toxics
R825433C026 Effect of Photochemical Reactions in Fog Drops and Aerosol Particles on the Fate of Atmospheric Chemicals in the Central Valley
R825433C027 Source Load Modeling for Sediment in Mountainous Watersheds
R825433C028 Stress of Increased Sediment Loading on Lake and Stream Function
R825433C029 Watershed Response to Natural and Anthropogenic Stress: Lake Tahoe Nutrient Budget
R825433C030 Mercury Distribution and Cycling in Sierra Nevada Waterbodies
R825433C031 Pre-contact Forest Structure
R825433C032 Identification and distribution of pest complexes in relation to late seral/old growth forest structure in the Lake Tahoe watershed
R825433C033 Subalpine Marsh Plant Communities as Early Indicators of Ecosystem Stress
R825433C034 Regional Hydrogeology and Contaminant Transport in a Sierra Nevada Ecosystem
R825433C035 Border Rivers Watershed
R825433C036 Toxicity Studies
R825433C037 Watershed Assessment
R825433C038 Microbiological Processes in Sediments
R825433C039 Analytical and Biomarkers Core
R825433C040 Organic Analysis
R825433C041 Inorganic Analysis
R825433C042 Immunoassay and Serum Markers
R825433C043 Sensitive Biomarkers to Detect Biochemical Changes Indicating Multiple Stresses Including Chemically Induced Stresses
R825433C044 Molecular, Cellular and Animal Biomarkers of Exposure and Effect
R825433C045 Microbial Community Assays
R825433C046 Cumulative and Integrative Biochemical Indicators
R825433C047 Mercury and Iron Biogeochemistry
R825433C048 Transport and Fate Core
R825433C049 Role of Hydrogeologic Processes in Alpine Ecosystem Health
R825433C050 Regional Hydrologic Modeling With Emphasis on Watershed-Scale Environmental Stresses
R825433C051 Development of Pollutant Fate and Transport Models for Use in Terrestrial Ecosystem Exposure Assessment
R825433C052 Pesticide Transport in Subsurface and Surface Water Systems
R825433C053 Currents in Clear Lake
R825433C054 Data Integration and Decision Support Core
R825433C055 Spatial Patterns and Biodiversity
R825433C056 Modeling Transport in Aquatic Systems
R825433C057 Spatial and Temporal Trends in Water Quality
R825433C058 Time Series Analysis and Modeling Ecological Risk
R825433C059 WWW/Outreach
R825433C060 Economic Effects of Multiple Stresses
R825433C061 Effects of Nutrients on Algal Growth
R825433C062 Nutrient Loading
R825433C063 Subalpine Wetlands as Early Indicators of Ecosystem Stress
R825433C064 Chlorinated Hydrocarbons
R825433C065 Sierra Ozone Studies
R825433C066 Assessment of Multiple Stresses on Soil Microbial Communities
R825433C067 Terrestrial - Agriculture
R825433C069 Molecular Epidemiology Core
R825433C070 Serum Markers of Environmental Stress
R825433C071 Development of Sensitive Biomarkers Based on Chemically Induced Changes in Expressions of Oncogenes
R825433C072 Molecular Monitoring of Microbial Populations
R825433C073 Aquatic - Rivers and Estuaries
R825433C074 Border Rivers - Toxicity Studies