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Bioaccumulation of Pollutants in California Waters: A Review of Historic Data and Assessment of Impacts on Fishing and Aquatic Life

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Bioaccumulation of Pollutants in California Waters: A Review of Historic Data and Assessment of Impacts on Fishing and Aquatic Life
California State Water Resources Control Board, San Francisco Estuary Institute | October 24, 2007...
Summary
This report was written for the State Water Resources Control Board’s Surface Water Ambient Monitoring Program (SWAMP) as a step toward the development...

This report was written for the State Water Resources Control Board’s Surface Water Ambient Monitoring Program (SWAMP) as a step toward the development of an improved bioaccumulation monitoring program for California. The report provides a review of bioaccumulation monitoring data generated under three historic State Board programs (the Toxic Substances Monitoring Program, the State Mussel Watch Program, and the Coastal Fish Contamination Program) and other major bioaccumulation studies since 1970. Future monitoring will be guided by assessment questions developed for the SWAMP. The objective of this report was to evaluate how well the historic data from the State Board programs and from other major monitoring efforts since 1970 address these questions. This exercise has provided a substantial amount of information about present and historical impacts of pollutant bioaccumulation on shing and aquatic life in California, and has also highlighted areas where improved sampling approaches can better address the assessment questions.

Present concentrations of pollutants in many California water bodies are high enough to cause concern for possible effects on human health and to have a significant impact on the fishing beneficial use. Consumption advisories, 303(d) listings, and the bioaccumulation database as a whole provide three indices of the status of this impact. Consumption advisories exist for an increasing number of water bodies, but these represent only a fraction of the areas likely to need them. Lack of suitable data is a major impediment to developing advice for additional water bodies. A US E.P.A. evaluation of the 2002 303(d) List indicated that large portions of the state had not been assessed, especially rivers and coastline. Most of the lake area in the state (61%) had been assessed, and a relatively small percentage of the total area (6%) was classified as impaired. Assessment of lakes, however, has focused primarily on the largest lakes, leaving the vast majority of smaller lakes unsampled. Many of these small lakes are near population centers and are popular for shing. Bays and estuaries had been thoroughly assessed (98% of the area) and 93% of the total area was impaired.

Evaluation of the most recent monitoring data (collected from 1998-2003) indicates that, for the locations sampled, 32% had low concentrations of pollutants, 42% had moderate concentrations, 18% had high concentrations, and 8% had very high concentrations (Figure 1). Concentrations in the low category are in a range where consumption is generally encouraged by the California Office of Environmental Health Hazard Assessment (OEHHA) (Klasing and Brodberg 2006). OEHHA is the agency responsible for managing health risks due to contaminated sport fish in California. Concentrations in the very high category are in a range where OEHHA discourages consumption (Klasing and Brodberg 2006). Lakes assigned to the moderate, high, or very high concentration categories were primarily affected by mercury, with PCBs also playing a lesser role.

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California Bay – Delta Authority Fish Mercury Project: The Relationship between Landscape Features and Sport Fish Mercury in the Sacramento-San Joaquin Delta Watershed
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California Bay – Delta Authority Fish Mercury Project: The Relationship between Landscape Features and Sport Fish Mercury in the Sacramento-San Joaquin Delta Watershed
San Francisco Estuary Institute | November 2, 2007...
Summary
The goal of this study was to quantify the relationship between landscape features and mercury in sport fish. We hypothesized that spatial variation...
The goal of this study was to quantify the relationship between landscape features and mercury in sport fish. We hypothesized that spatial variation in sport fish mercury would most strongly relate to major point sources associated with mining activity, habitat features (e.g., abundance of wetlands), and watershed-scale patterns in mercury deposition from the atmosphere.

Geographic information system (GIS) techniques were used to evaluate the influence of these features on the bioaccumulation of mercury in sport fish. In addition, we attempted to determine the most appropriate spatial scale for analysis of these influences. Fish mercury data were selected from a state-wide historical bioaccumulation database, which also included data collected by the Fish Mercury Project (FMP) in 2005. Based on the geographic distribution of the sampling locations, three species common across the study area were chosen for analysis: largemouth bass, channel catfish, and white catfish. For the time interval examined (1990 – 2005), the mean wet weight concentration for each species at a given location was calculated.

By superimposing hydrologic flow paths with watershed delineations, we were able to determine flow direction and pathways from upstream sources to downstream habitats. “Fish watersheds” (watershed areas upstream of fish sampling locations) were created for a subset of locations in the CalFed Ecosystem Restoration Program Geographic Scope. Regions heavily influenced by mining within each watershed were also delineated. We examined landscape features in fish watersheds and within close proximity (circular buffers) of fish locations. Using a GIS database, several statistics were derived for each fish watershed area and buffer, including the percent covered by habitat features (vegetated vs. non-vegetated wetlands, permanent vs. temporary inundation), number of gold and mercury mines, total land area (km2), and total length (km) of all streams and rivers.

The work presented in this report is the first attempt the authors are aware of to relate landscape features to fish mercury concentrations using GIS on a large regional scale. Fish mercury concentrations appeared to be influenced by many complex and interacting factors that obscured any obvious correlations with atmospheric deposition, historic mining districts, and wetlands at the watershed scale. Some features seemed to have an influence at the proximal-scale (buffer) analyses, namely vegetated wetland and temporarily inundated aquatic habitat. Though these tentative conclusions were based on small sample sizes, they contradicted the prevailing notion that wetlands generally increase methylmercury accumulation in the food web.

The lack of clear relationships in the dataset analyzed is probably due to shortcomings in the available data, rather than a true absence of influence of atmospheric deposition, mining, or wetlands on spatial patterns in mercury bioaccumulation. Future attempts to relate landscape features with mercury in the food web at the watershed scale should focus on watersheds with a stronger linkage between landscape features and mercury in fish and fewer confounding factors. Statewide monitoring of sport fish is currently being planned that should provide a better basis for conducting this type of analysis in the future.

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Contaminant Concentrations in Sport Fish from San Francisco Bay: 2014
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Contaminant Concentrations in Sport Fish from San Francisco Bay: 2014
San Francisco Estuary Institute | January 1, 2014...
Summary
This summary report presents results from a 2014 survey of contaminants in San Francisco Bay sport fish, as well as an additional 2015...
This summary report presents results from a 2014 survey of contaminants in San Francisco Bay sport fish, as well as an additional 2015 sampling of sport fish in Artesian Slough in Lower South Bay. This monitoring effort represents the seventh round of sport fish contaminant monitoring conducted by the Regional Monitoring Program for Water Quality in San Francisco Bay (RMP). This technical report is intended for agency staff charged with managing water quality issues related to bioaccumulation of contaminants in San Francisco Bay.

The RMP began sport fish monitoring in 1997, following a pilot study conducted by the Bay Protection and Toxic Cleanup Program in 1994. Data collected through this monitoring program provides updates on the status and long-term trends of contaminants in Bay sport fish, and are used to update human health consumption advisories and evaluate the effectiveness of regulatory and management efforts to reduce the impacts of contaminants of concern in the Bay.

Key analyses in this report include comparisons of concentrations to human health and regulatory thresholds, spatial trend evaluation, and temporal trend evaluation.

Mercury, polychlorinated biphenyls (PCBs), dioxins, selenium, polybrominated diphenyl ethers (PBDEs), and perfluoroalkylated substances (PFASs) were analyzed across sixteen fish species collected at eight locations in San Francisco Bay and Artesian Slough.

Fish species were selected based on a number of criteria, including species that are popular for consumption, are sensitive indicators of problems (accumulating relatively high concentrations of contaminants), are widely distributed, represent different exposure pathways (benthic vs. pelagic), and have been monitored in the past. Concentrations were compared to numeric human health thresholds established by the California Office of Environmental Health Hazard Assessment (OEHHA) for mercury, PCBs, selenium, and PBDEs. Results were also compared to regulatory thresholds for mercury, PCBs, and selenium, as well as non-regulatory screening value for dioxins, which have been established in Total Maximum Daily Load (TMDL) regulations by the San Francisco Bay Regional Water Quality Control Board (Water Board).

The OEHHA fish consumption advisory is primarily driven by human exposure risks to mercury and PCBs. The 2014 data show that mercury and PCB concentrations remain high and widespread, indicating that these contaminants continue to pose the greatest human and wildlife health risks. Mercury concentrations exceeded OEHHA’s no consumption threshold for the sensitive population (women 18-45 and children 1-17) in several white sturgeon and striped bass samples, while PCB concentrations exceeded the no consumption threshold in Pacific sardine and white sturgeon samples. The spatial distribution of contamination has remained consistent over time, reflecting current knowledge of contaminated source areas targeted for management activities. Recent data showed no clear evidence of Bay-wide declines in either mercury or PCBs, although progressively lower PCB concentrations have been observed in recent years near Berkeley and in San Pablo Bay.

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Contaminant Effects on California Bay-Delta Species & Human Health
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Contaminant Effects on California Bay-Delta Species & Human Health
San Francisco Estuary and Watershed Science | December 1, 2016...
Summary
Many contaminants in the California Bay-Delta exceed regulatory standards, impact aquatic species, and potentially affect human health. Recent studies provide evidence that contaminants...
Many contaminants in the California Bay-Delta exceed regulatory standards, impact aquatic species, and potentially affect human health. Recent studies provide evidence that contaminants impact species of concern in the Bay-Delta (e.g., the decline of several important fish species referred to as the “Pelagic Organism Decline”). Multiple chemicals impair processes at cellular and physiological levels (measured as growth, development, and behavior abnormalities), ultimately affecting populations.

As an important example, the population decline of the endangered delta smelt (Hypomesus transpacificus) is significantly associated with multiple stressors, including insecticide use. New analyses presented in this paper show significant correlations between pyrethroid (an insecticide) use and declining abundance of POD fish species.

Water sampled from the Bay-Delta causes multiple harmful effects in fish and delta smelt. Fish prey items are also impacted by contaminants; this may have an indirect effect on their populations. Co-occurrence with thermal changes or disease can worsen contaminant effects.

Contaminants also pose threats to human health via consumption of fish, drinking water, and contact recreation, in particular, mercury, toxins, disinfection byproducts, pesticides, pharmaceuticals, and personal care products. The role of contaminants in the decline of Bay-Delta species is difficult to accurately assess in a complex, dynamic system. However, tools and approaches are available to evaluate contaminant impacts on Bay-Delta species, and separate the effects of multiple stressors. Integrated monitoring and focused mechanistic studies are instrumental for addressing management needs. Impact and risk assessments should be conducted for different species across multiple life stages, with emphasis on early life stages of high-priority Bay-Delta species.

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DRERIP Ecosystem Conceptual Model: Chemical stressors
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DRERIP Ecosystem Conceptual Model: Chemical stressors
California Department of Fish and Wildlife | February 5, 2008...
Summary
The Sacramento-San Joaquin Delta ecosystem comprises many different habitat types, and is home to a large number of species. Thousands of chemical contaminants...
The Sacramento-San Joaquin Delta ecosystem comprises many different habitat types, and is home to a large number of species. Thousands of chemical contaminants have been or are being introduced into the Delta. The conceptual model presented here is therefore general in nature, and is intended to provide a framework for more refined models for individual species, habitats and, in particular, contaminants of interest, for example selenium, mercury and pyrethroids.

The model consists of three major submodels (Figure 1). Submodel 1: Exposure assessment which includes fate and transport of contaminants and the co-occurrence of chemicals with Delta organisms; the intermediate outcome of this submodel is “Exposure Concentration”. Submodel 2: Bioavailability of contaminants to Delta organisms; the intermediate outcome of this submodel is “Bioavailable Concentration” or “Dose”. Submodel 3: Toxic effects assessment with the final model outcome “Population Level Effects”.

In the following narrative, we provide a description for each submodel, its parameters, and linkages to other models. We discuss the model’s limitations and provide recommendations for its application in management.

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DRERIP Ecosystem Conceptual Model: Mercury
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DRERIP Ecosystem Conceptual Model: Mercury
California Department of Fish and Wildlife | January 24, 2008...
Summary
Mercury has been identified as an important contaminant in the Delta, based on elevated concentrations of methylmercury (a toxic, organic form that readily...
Mercury has been identified as an important contaminant in the Delta, based on elevated concentrations of methylmercury (a toxic, organic form that readily bioaccumulates) in fish and wildlife. There are health risks associated with human exposure to methylmercury by consumption of sport fish, particularly top predators such as bass species. Original mercury sources were upstream tributaries where historical mining of mercury in the Coast Ranges and gold in the Sierra Nevada and Klamath-Trinity Mountains caused contamination of water and sediment on a regional scale. Remediation of abandoned mine sites may reduce local sources in these watersheds, but much of the mercury contamination occurs in sediments stored in the riverbeds, floodplains, and the Bay-
Delta, where scouring of Gold-Rush-era sediment represents an ongoing source.

Conversion of inorganic mercury to toxic methylmercury occurs in anaerobic environments including some wetlands. Wetland restoration managers must be cognizant of potential effects on mercury cycling so that the problem is not exacerbated. Recent research suggests that wetting-drying cycles can contribute to mercury methylation. For example, high marshes (inundated only during the highest tides for several days per month) tend to have higher methylmercury concentrations in water, sediment, and biota compared with low marshes, which do not dry out completely during the tidal cycle. Seasonally inundated flood plains are another environment experiencing wetting and drying where methylmercury concentrations are typically elevated.

Stream restoration efforts using gravel injection or other reworking of coarse sediment in most watersheds of the Central Valley involve tailings from historical gold mining that are likely to contain elevated mercury in associated fines. Habitat restoration projects, particularly those involving wetlands, may cause increases in methylmercury exposure in the watershed. This possibility should be evaluated.

The DRERIP mercury conceptual model and its four submodels (1. Methylation, 2. Bioaccumulation, 3. Human Health Effects, and 4. Wildlife Heath Effects) can be used to understand the general relationships among drivers and outcomes associated with mercury cycling in the Delta. Several linkages between important drivers and outcomes have been identified as important but highly uncertain (i.e. poorly understood). For example, there may be significant wildlife health effect of mercury on mammals and reptiles in the Delta, but there is currently very little or no information about it. The characteristics of such linkages are important when prioritizing and funding restoration projects and associated monitoring in the Delta and its tributaries.

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Environmental Health Risks from Abandoned Mines in the Sierra Nevada
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Environmental Health Risks from Abandoned Mines in the Sierra Nevada
The Sierra Fund | June 9, 2014...
Summary
The widespread pollution from Gold Rush mining activities, including mercury, arsenic and lead, constitutes the oldest and longest neglected environmental justice problem in...
The widespread pollution from Gold Rush mining activities, including mercury, arsenic and lead, constitutes the oldest and longest neglected environmental justice problem in California. The effects of this pollution on human health and the environment are only now beginning to be addressed.

Today, the effects of historic mining pollution are an invisible but very real threat to people who live, work or recreate in the Sierra Nevada. Toxins of concern include mercury, arsenic, lead and asbestos. There is little information about these potential exposures available to Sierra residents. State-issued fish consumption advisories in the region
do not provide site-specific advice for many locations people fish, or the species people eat.

In 2006, The Sierra Fund, in partnership with California State University Chico, conducted a survey of Sierra clinics. This study found that not one of 13 surveyed clinics included information on mercury in fish as part of their maternal/infant health programs, whether caught locally or not. Additionally, the study learned that none of the clinics surveyed administer an environmental health history form, so it is difficult to connect current health problems to environmental exposures.

In order to address this lack of information and provide a springboard for more research, The Sierra Fund conducted three pilot studies of potential environmental exposures in 2009 and 2010 and a pilot outreach program to present these findings to Sierra communities in 2013-14. This report summarizes findings and recommendations from these efforts, in order to encourage continued research into these potentially serious health exposures.

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Estimating Exposure of Piscivorous Birds and Sport Fish to Mercury in California Lakes Using Prey Fish Monitoring—A Predictive Tool for Managers

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Estimating Exposure of Piscivorous Birds and Sport Fish to Mercury in California Lakes Using Prey Fish Monitoring—A Predictive Tool for Managers
U.S. Geological Survey (USGS) | May 22, 2015...
Summary
Numerous water bodies in California are listed under the Clean Water Act as being impaired due to mercury (Hg) contamination. The Surface Water...
Numerous water bodies in California are listed under the Clean Water Act as being impaired due to mercury (Hg) contamination. The Surface Water Ambient Monitoring Program (SWAMP), via the Bioaccumulation Oversight Group (BOG), has recently completed statewide surveys of contaminants in sport fish tissue from more than 250 lakes and rivers in California and throughout coastal waters. This effort focused on human health issues but did not include beneficial uses by wildlife. Many piscivorous birds such as grebes, terns, cormorants, and mergansers eat fish smaller than those that were sampled by BOG, and sport fish Hg concentrations are not always indicative of wildlife exposure to Hg; therefore, the BOG surveys could not address whether wildlife were at risk due to Hg-induced reproductive impairment in these lakes.

We used western grebes (Aechmophorus occidentalis) and Clark’s grebes (Aechmophorus clarkii) as our index of wildlife exposure to Hg in California lakes. Grebes are widely distributed in lakes throughout California and, as piscivorous waterbirds, are near the top of the food chain in lakes. Additionally, grebes become flightless after they arrive at their summer locations. Thus, grebes are useful representatives for wildlife risk from local, lake-specific contaminant exposure. Grebes also breed at many lakes throughout California, making them susceptible to impaired reproduction due to local Hg contamination.

We developed a tool for estimating wildlife and sport fish risk from Hg exposure based on Hg concentrations in prey fish. This quantitative tool can be used to predict Hg concentrations in grebe blood, grebe eggs, and sport fish, thus facilitating a feasible alternative for adequately estimating wildlife exposure when more comprehensive wildlife sampling is not possible. Specifically, we sampled grebes, prey fish, and sport fish simultaneously at 25 lakes throughout California during the spring and summer of 2012 and 2013 when breeding birds are particularly vulnerable to Hg-induced reproductive impairment. We selected lakes based on a combination of factors, including lakes
1. from southern and northern California,
2. of various sizes, shapes, and elevations,
3. with a range of sport fish Hg exposure levels
4. where largemouth bass (Micropterus salmoides) was the primary sport fish, and
5. with a history of use by grebes.
Using these factors ensured that our results are representative of a broad range of lakes and reservoirs in California and are comparable to prior BOG studies.

Specifically, we addressed three management questions:
1. Does methylmercury pose significant risks to aquatic life in a representative sample of California lakes and reservoirs?
2. Can a correlational approach be applied on a statewide basis to estimate risks to birds?
3. What are appropriate water-quality monitoring requirements to address methylmercury exposure in wildlife?
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Long-term Monitoring of Pollutants in Fish and Mussels Documents Major Improvements and Persistent Problems

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Long-term Monitoring of Pollutants in Fish and Mussels Documents Major Improvements and Persistent Problems
California State Water Resources Control Board | December 1, 2007...
Summary
Of the 390 sites sampled between 1998 and 2003, 32 percent fell into the “low” contamination category. These sites were scattered throughout the...

Of the 390 sites sampled between 1998 and 2003, 32 percent fell into the “low” contamination category. These sites were scattered throughout the state, with a particular prevalence in the Sierra Nevada and the area north of San Diego. Unfortunately, the Delta region had relatively few sites with low concentration of pollutants. In general, PCB and DDT levels in fish and mussels across California have declined greatly since the 1970s, and many species have bounced back in response to the decline in DDT levels.

However, the report also found that present concentrations of pollutants in fish collected from many California water bodies are high enough to cause concern for possible effects on human health and to have a significant impact on the fishing beneficial use. The report found that fish in 68 percent of the water bodies sampled have “moderate to very high levels of mercury or persistent organics (such as PCBs and organochlorinated pesticides like DDT).” Consumption advisories exist for only a fraction of the water bodies likely to need them. Many water bodies with elevated contaminant levels in fish are near population centers and are popular for fishing. Furthermore, subsistence fishing is increasing, and consumption of contaminated fish is an environmental justice issue.

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Mercury levels in nearshore fish from the Central Coast area: Important information for fish consumers
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Mercury levels in nearshore fish from the Central Coast area: Important information for fish consumers
State Water Resources Control Board | April 11, 2017...
Summary
Several species of marine fish commonly caught in nearshore Central Coast waters may contain high levels of mercury. Several rockfish species, especially Black-and-Yellow,...
Several species of marine fish commonly caught in nearshore Central Coast waters may contain high levels of mercury. Several rockfish species, especially Black-and-Yellow, China, Copper, and Gopher, and sharks and bat rays are species of concern. People who routinely consume fish from nearshore waters are advised to follow the recent statewide coastal advisory released in November 2016 by the California Office of Environmental Health Hazard Assessment (OEHHA) regarding consumption of these and other species. The advisory recommends “no consumption” of several fish species for women 18-45 years and for children 1-17 years, and limiting consumption of some species for all population groups. The advisory can be found online at http://oehha.ca.gov/advisories/statewide-advisory-eating-fish-california-coastal-locations-without-site-specific-advice. Site-specific advice was also developed for Elkhorn Slough, and can be viewed at http://oehha.ca.gov/advisories/elkhorn-slough.

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Mercury losses and recovery during a suction dredge test in the South Fork of the American River
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Mercury losses and recovery during a suction dredge test in the South Fork of the American River
State Water Resources Control Board | July 29, 2005...
Summary
Mercury has been used widely since the dawn of recorded history for gold mining. During California’s gold rush, gold miners used about 6...
Mercury has been used widely since the dawn of recorded history for gold mining. During California’s gold rush, gold miners used about 6 million kilograms or 6.6 thousand tons of mercury (Churchill, 2000) to recover over 3.6 thousand tons of gold (Bulletin 193). The weight of mercury used is roughly equal to the total weight of a 9-mile long line of 2,750, full sized pickup trucks (note: the pick up truck line equaling gold recovered would only be 5 miles long). The miners lost about half of the mercury to the environment.

Using historical records,Churchill (2000) estimated that total mercury losses ranged between 2.3 million and 2.6 million kilograms for placer and lode mining in the Sierra Nevada Geomorphic Province. Consequently, elemental mercury from the gold rush is still found, sometimes in amounts that constitute a local hotspot (i.e., a location where visible elemental mercury is found) in Sierra Nevada watersheds where gold mining occurred.

In March 2003, a recreational gold miner reported a mercury hotspot in the South Fork of the American River near Coloma, to State Water Resources Control Board staff. It was the first time a recreational gold miner had revealed a hotspot locations to agency staff. Coloma is California’s historic “Gold Discovery” site as James W. Marshall’s discovery there in January 1848 initiated the 1849 gold rush. Steve Franklin, the recreational gold miner who reported the hotspot, claimed to have recovered about a kilogram of mercury while gold mining from the hotspot during January and February 2003.

Finding a hotspot near Coloma raised questions about its potential threat to human health, effects on local fi sh, and threat to water quality. Moreover, its discovery presented an opportunity to test the notion that recreational gold miners effectively clean up mercury hotspots while suction dredging for gold. There is no record of any attempts by state or federal agencies to clean up a mercury hotspot in a California river. But State and federal agencies have discussed whether encouraging or even providing support for recreational gold miners to clean up hotspots is viable and wise. The pros are that there is a potentially large, volunteer workforce. The cons are that oversight would be difficult and, up to now, no data supported the notion that suction dredges could recover mercury efficiently.

Recreational gold dredging on public and private lands is a moderately popular activity in California. The Department of Fish and Game (DFG) issues several thousand permits annually to recreational gold dredgers. Along with gold, recreational dredgers recover iron (nails bolts, etc.), lead (fishing weights, buckshot, and spent bullets) and mercury (elemental mercury, mercury/gold amalgam, and mercury stained gold). Over the past several years, United States Forest Service (USFS), Bureau of Land Management (BLM) and State agency staff have discussed setting up a mercury recovery program for recreational dredgers. Incentives (e.g., cash for mercury, free dredging permits, new areas opened for dredging) were proposed in exchange for mercury turned in by recreational dredgers.

Offering such incentives was and remains controversial for a variety of
reasons and a mercury recovery program was not started. Moreover, an important drawback was that the efficiency of a standard suction dredge at recovering mercury was unknown. Consequently, no one knew if mercury would be lost along with waste sediment from a suction dredge. Clearly, a mercury recovery program that dispersed elemental mercury back into a stream in substantial amounts would be unacceptable. The hotspot presented an opportunity to determine the mercury recovery efficiency of a suction dredge.

Studying the hotspot may also reveal bedrock characteristics and sediment transport conditions that cause hotspots, and the effects that concentrated mercury has on local fish. This report documents the results of a suction dredge test that was completed in September 2003 by State Water Board, USFS, and DFG staff.

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Mercury on a landscape scale—Balancing regional export with wildlife health
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Mercury on a landscape scale—Balancing regional export with wildlife health
U.S. Geological Survey (USGS), U.S. Environmental Protection Agency (EPA), U.S. Bureau of Land Management (BLM), California Department of Fish and Wildlife (CDWF), California Water Boards - Central Valley Regional Water Quality Control Board, Cosumnes River Preserve | June 26, 2018...
Summary
The Cosumnes River watershed requires a 57–64 percent reduction in loads to meet the new Delta methylmercury (MeHg) total maximum daily load allocation,...
The Cosumnes River watershed requires a 57–64 percent reduction in loads to meet the new Delta methylmercury (MeHg) total maximum daily load allocation, established by the Central Valley Regional Water Quality Control Board. Because there are no large point sources of MeHg in the watershed, the focus of MeHg load reductions will fall upon non-point sources, particularly the expansive wetlands considered to be a primary source of MeHg in the region. Few management practices have been implemented and tested in order to meet load reductions in managed wetlands, but recent efforts have shown promise. This project examines a treatment approach to reduce MeHg loads to the Sacramento-San Joaquin River Delta by creating open-water deep cells with a small footprint at the downstream end of wetlands to promote net demethylation of MeHg and to minimize MeHg and Hg loads exiting wetlands at the Cosumnes River Preserve. Specifically, the deep cells were were located immediately up gradient of the wetland’s outflow weir and were deep enough (75–91 centimeter depth) to be vegetation-free. The topographic and hydrologic structure of each treatment wetland was modified to include open-water deep cells so that the removal of aqueous MeHg might be enhanced through (1) particle settling, (2) photo-degradation, and (3) benthic microbial demethylation. These deep cells were, therefore, expected to clean MeHg from surface water prior to its discharge to the Cosumnes River and the downstream Delta.

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Mercury Risks to Wildlife in California Lakes: Statewide Survey Finds Fish-Eating Birds at Risk in Many Lakes

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Mercury Risks to Wildlife in California Lakes: Statewide Survey Finds Fish-Eating Birds at Risk in Many Lakes
U.S. Geological Survey | May 22, 2015...
Summary
Numerous water bodies in California are listed under the Clean Water Act as being impaired by mercury contamination. Mercury generally poses risks both...

Numerous water bodies in California are listed under the Clean Water Act as being impaired by mercury contamination. Mercury generally poses risks both to humans who consume fish from these water bodies and to wildlife species at the top of the aquatic food chain. The SWAMP has recently completed statewide surveys of contaminants in sport fish from California lakes, rivers, and coastal waters. These surveys generated information regarding potential human exposure to mercury, but did not include monitoring to assess risks to wildlife.

This study was performed to address critical information gaps related to mercury risks to wildlife in California lakes. Western grebes and Clark’s grebes were chosen as the wildlife indicator species. These grebe species are widely distributed and breed in lakes throughout California, are piscivorous (fish-eaters) near the top of the lake food chain, and become flightless after they arrive at their summer locations. This makes them excellent indicators of lake-specific contaminant exposure. Mercury concentrations were measured in grebe blood at all of the lakes, and in grebe eggs where they could be collected. Mercury also was measured in the small fish species that grebes eat and in sport fish in order to determine whether correlations between fish and grebes could be used to estimate risk to grebes in cases where direct measurements of mercury in grebes are not available. Grebes, prey fish, and sport fish were sampled at 25 lakes throughout California (Figure 1) during the spring and summer of 2012 and 2013, seasons when breeding occurs and birds are vulnerable to mercury - induced impairment of reproduction. Mercury concentrations were measured in blood from 354 grebes at 25 lakes, 101 grebe eggs at 7 lakes, 505 prey fish from14 species at 25 lakes, and 230 sport fish from 5 species at 24 lakes. T he lakes included in the survey were selected to be a representative sampling spanning the entire state, a range of mercury contamination, and a variety of sizes, shapes, and elevations.

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Mercury, Monomethyl Mercury, and Dissolved Organic Carbon Concentrations in Surface Water Entering and Exiting Constructed Wetlands Treated with Metal-Based Coagulants, Twitchell Island, California
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Mercury, Monomethyl Mercury, and Dissolved Organic Carbon Concentrations in Surface Water Entering and Exiting Constructed Wetlands Treated with Metal-Based Coagulants, Twitchell Island, California
USGS | August 30, 2015...
Summary
Coagulation with metal-based salts is a practice commonly employed by drinking-water utilities to decrease particle and dissolved organic carbon concentrations in water. In...
Coagulation with metal-based salts is a practice commonly employed by drinking-water utilities to decrease particle and dissolved organic carbon concentrations in water. In addition to decreasing dissolved organic carbon concentrations, the effectiveness of iron- and aluminum-based coagulants for decreasing dissolved concentrations both of inorganic and monomethyl mercury in water was demonstrated in laboratory studies that used agricultural drainage water from the Sacramento–San Joaquin Delta of California.

To test the effectiveness of this approach at the field scale, nine 15-by-40?meter wetland cells were constructed on Twitchell Island that received untreated water from island drainage canals (control) or drainage water treated with polyaluminum chloride or ferric sulfate coagulants. Surface-water samples were collected approximately monthly during November 2012–September 2013 from the inlets and outlets of the wetland cells and then analyzed by the U.S. Geological Survey for total concentrations of mercury and monomethyl mercury in filtered (less than 0.3 micrometers) and suspended-particulate fractions and for concentrations of dissolved organic carbon.

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Mining’s Toxic Legacy: An Initiative to Address Mining Toxins in the Sierra Nevada
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Mining’s Toxic Legacy: An Initiative to Address Mining Toxins in the Sierra Nevada
The Sierra Fund | March 1, 2008...
Summary
The purpose of this report is to present current information on the nature and extent of mining toxins in the Sierra, the problems...
The purpose of this report is to present current information on the nature and extent of mining toxins in the Sierra, the problems they pose to human and environmental health, and recommendations for action to address these problems. This is accomplished by examining the best available science from the perspective of communities in the Gold Country, and directing the results to regional nonprofit organizations and local, state, federal, and tribal governments.

The area considered by this Initiative is defined to be consistent with the State of California’s Sierra Nevada Conservancy service boundary. Areas of the Sierra Nevada in the State of Nevada were also considered as a secondary topic. This enabled the Initiative to address both the east and west sides of the Sierra, as well as some parts of the Cascade region, all of which were heavily impacted by historic mining.

Though the impact of gold mining is the primary focus of the Initiative, gold prospectors found other commodities, including iron, copper, lead, silver, and tungsten which they then mined and sold. This report considers the impact of these mining activities as a secondary topic and in less detail.

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Pulse of the Delta 2012
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Pulse of the Delta 2012
Delta Regional Monitoring Program | August 2, 2013...
Summary
This second edition of the Pulse of the Delta includes the following sections: The KEY TOPIC article introduces this year’s theme, LINKING SCIENCE...
This second edition of the Pulse of the Delta includes the following sections:

The KEY TOPIC article introduces this year’s theme, LINKING SCIENCE AND MANAGEMENT THROUGH REGIONAL MONITORING (PAGE 6).

The MANAGEMENT UPDATE section provides updates on Delta RMP development (PAGE 12) and the U.S. Environmental Protection Agency (EPA)’s Delta Clean Water Act evaluation (PAGE 18). It further provides an update on the development of Nutrient Numeric Endpoints for San Francisco Bay, due to the relevance of this topic to Delta stakeholders (PAGE 28). And as a new feature, the Management Update section now also provides a regulatory status update for pollutants of concern.
This edition of the Pulse of the Delta introduces a NEW STATUS AND TRENDS section with updates on important monitoring results (PAGE 44) and leading indicators (PAGE 50) for the Delta.

The STATUS AND TRENDS section was made possible thanks to significant contributions by the Interagency Ecological Program, U.S. Geological Survey, the Central Valley Regional Water Board, California Department of Fish and Game, California Department of Water Resources, and scientists at the UC Berkeley and San Francisco State University Romberg Tiburon Center.

Two FEATURE ARTICLES provide an overview of recent research findings that could help wetland managers reduce the methylmercury problem and a glimpse into the future of the Interagency Ecological Program (IEP).
One of the main challenges as ecosystem restoration efforts are moving forward will be the mercury problem. Large-scale restoration of wetland areas will be required to provide a sufficient amount of aquatic habitat for restoring the Delta ecosystem. At the same time, water quality managers will need to identify actions to protect people and wildlife from exposure to methylmercury that may originate from restored wetlands, due to a legacy of mercury contamination in Delta soils. Recently completed and ongoing studies in the Yolo Bypass provide new information on management options for controlling methylmercury production in wetlands and offsite transport (PAGE 66).

IEP scientists have been monitoring and researching the San Francisco Estuary since 1970. Now the IEP has arrived at an important crossroads, and its future is being decided at the same time as environmental managers are determining what a desirable future ecosystem would look like, how it would function, and how it can be established (PAGE 76).

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Quantifying the Eroded Volume of Mercury-Contaminated Sediment Using Terrestrial Laser Scanning at Stocking Flat, Deer Creek, Nevada County, California, 2010–13
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Quantifying the Eroded Volume of Mercury-Contaminated Sediment Using Terrestrial Laser Scanning at Stocking Flat, Deer Creek, Nevada County, California, 2010–13
USGS | July 7, 2016...
Summary
High-resolution ground-based light detection and ranging (lidar), also known as terrestrial laser scanning, was used to quantify the volume of mercury-contaminated sediment eroded...
High-resolution ground-based light detection and ranging (lidar), also known as terrestrial laser scanning, was used to quantify the volume of mercury-contaminated sediment eroded from a stream cutbank at Stocking Flat along Deer Creek in the Sierra Nevada foothills, about 3 kilometers west of Nevada City, California. Terrestrial laser scanning was used to collect sub-centimeter, three-dimensional images of the complex cutbank surface, which could not be mapped non-destructively or in sufficient detail with traditional surveying techniques.

The stream cutbank, which is approximately 50 meters long and 8 meters high, was surveyed on four occasions: December 1, 2010; January 20, 2011; May 12, 2011; and February 4, 2013. Volumetric changes were determined between the sequential, three-dimensional lidar surveys. Volume was calculated by two methods, and the average value is reported. Between the first and second surveys (December 1, 2010, to January 20, 2011), a volume of 143 plus or minus 15 cubic meters of sediment was eroded from the cutbank and mobilized by Deer Creek. Between the second and third surveys (January 20, 2011, to May 12, 2011), a volume of 207 plus or minus 24 cubic meters of sediment was eroded from the cutbank and mobilized by the stream. Total volumetric change during the winter and spring of 2010–11 was 350 plus or minus 28 cubic meters. Between the third and fourth surveys (May 12, 2011, to February 4, 2013), the differencing of the three-dimensional lidar data indicated that a volume of 18 plus or minus 10 cubic meters of sediment was eroded from the cutbank. The total volume of sediment eroded from the cutbank between the first and fourth surveys was 368 plus or minus 30 cubic meters.

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Reducing Methylmercury Accumulation in the Food Webs of San Francisco Bay and Its Local Watersheds
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Reducing Methylmercury Accumulation in the Food Webs of San Francisco Bay and Its Local Watersheds
San Francisco Estuary Institute | April 8, 2014...
Summary
San Francisco Bay (California, USA) and its local watersheds present an interesting case study in estuarine mercury (Hg) contamination. This review focuses on...
San Francisco Bay (California, USA) and its local watersheds present an interesting case study in estuarine mercury (Hg) contamination. This review focuses on the most promising avenues for attempting to reduce methylmercury (MeHg) contamination in Bay Area aquatic food webs and identifying the scientific information that is most urgently needed to support these efforts.

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Sources, Pathways and Loadings: Multi-Year Synthesis with a Focus on PCBs and Hg
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Sources, Pathways and Loadings: Multi-Year Synthesis with a Focus on PCBs and Hg
San Francisco Estuary Institute | December 15, 2015...
Summary
This report provides a synthesis of information gathered since 2000 on sources, pathways, and loadings of pollutants of concern in the San Francisco...
This report provides a synthesis of information gathered since 2000 on sources, pathways, and loadings of pollutants of concern in the San Francisco Bay Area with a focus on polychlorinated biphenyls (PCBs) and total mercury (Hg). Concentration and load estimates for other pollutants of concern (POC) are provided in the Appendix tables but not supported by any synthesis or discussion in the main body of the report. The PCB and Hg TMDLs for San Francisco Bay call for implementation of control measures to reduce stormwater PCB loads from 20 kg to 2 kg by 2030 and to reduce stormwater Hg loads from 160 kg to 80 kg by 2028 with an interim milestone of 120 kg by 2018.

These are very challenging objectives given that the 2 kg PCB load allocation translates to a mean annual yield of 0.31 g/km2 for the free flowing areas downstream from reservoirs (6,650 km2), a mean annual concentration of 1.33 ng/L (assuming an annual average flow from small tributaries of 1.5 km3), and mean annual particle ratio of 1.4 ng/g of suspended sediment load (assuming an average annual suspended sediment load of 1.4 million metric t). Similarly for Hg, the 80 kg load allocation translates to a mean annual yield of 12 g/km2, a mean annual concentration of 53 ng/L, and mean annual particle ratio of 58 ng/g of suspended sediment load.

Concentrations of these low magnitudes have been observed commonly in the Bay Area for Hg and yields of this low magnitude have been observed for PCBs and Hg. However, concentrations of PCBs at these magnitudes have only been observed in Marsh Creek (a more rural watershed) and particle ratios of PCBs and Hg as low as these have never been observed in the region.

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Summary of the MeHg Panels of the 2004 CalFed Science Conference
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Summary of the MeHg Panels of the 2004 CalFed Science Conference
San Francisco Estuary Institute | November 22, 2004...
Summary
Mercury (Hg) can become an environmental problem when sulfate-reducing anaerobic bacteria, in the presence of organic substrates, form methylmercury (MeHg), a highly toxic...
Mercury (Hg) can become an environmental problem when sulfate-reducing anaerobic bacteria, in the presence of organic substrates, form methylmercury (MeHg), a highly toxic compound that endangers wildlife and people by accumulating in their food.

The spatial and temporal variation in MeHg production is mainly a function of the availability of inorganic mercury to methylating bacteria. Typically only a small percentage (e.g. < 5 %) of total inorganic mercury is available for methylation. The amount of MeHg that actually becomes available for bioaccumulation depends on many environmental factors operating at different spatial scales, from watersheds to microbes. Scientists are working to prioritize these factors for management actions.

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Bioaccumulation of Pollutants in California Waters: A Review of Historic Data and Assessment of Impacts on Fishing and Aquatic Life

Bioaccumulation of Pollutants in California Waters: A Review of Historic Data and Assessment of Impacts on Fishing and Aquatic Life

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California Bay – Delta Authority Fish Mercury Project: The Relationship between Landscape Features and Sport Fish Mercury in the Sacramento-San Joaquin Delta Watershed

California Bay – Delta Authority Fish Mercury Project: The Relationship between Landscape Features and Sport Fish Mercury in the Sacramento-San Joaquin Delta Watershed

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Contaminant Concentrations in Sport Fish from San Francisco Bay: 2014

Contaminant Concentrations in Sport Fish from San Francisco Bay: 2014

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Contaminant Effects on California Bay-Delta Species & Human Health

Contaminant Effects on California Bay-Delta Species & Human Health

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DRERIP Ecosystem Conceptual Model: Chemical stressors

DRERIP Ecosystem Conceptual Model: Chemical stressors

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DRERIP Ecosystem Conceptual Model: Mercury

DRERIP Ecosystem Conceptual Model: Mercury

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Environmental Health Risks from Abandoned Mines in the Sierra Nevada

Environmental Health Risks from Abandoned Mines in the Sierra Nevada

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Estimating Exposure of Piscivorous Birds and Sport Fish to Mercury in California Lakes Using Prey Fish Monitoring—A Predictive Tool for Managers

Estimating Exposure of Piscivorous Birds and Sport Fish to Mercury in California Lakes Using Prey Fish Monitoring—A Predictive Tool for Managers

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Long-term Monitoring of Pollutants in Fish and Mussels Documents Major Improvements and Persistent Problems

Long-term Monitoring of Pollutants in Fish and Mussels Documents Major Improvements and Persistent Problems

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Mercury levels in nearshore fish from the Central Coast area: Important information for fish consumers

Mercury levels in nearshore fish from the Central Coast area: Important information for fish consumers

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Mercury losses and recovery during a suction dredge test in the South Fork of the American River

Mercury losses and recovery during a suction dredge test in the South Fork of the American River

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Mercury on a landscape scale—Balancing regional export with wildlife health

Mercury on a landscape scale—Balancing regional export with wildlife health

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Mercury Risks to Wildlife in California Lakes: Statewide Survey Finds Fish-Eating Birds at Risk in Many Lakes

Mercury Risks to Wildlife in California Lakes: Statewide Survey Finds Fish-Eating Birds at Risk in Many Lakes

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Mercury, Monomethyl Mercury, and Dissolved Organic Carbon Concentrations in Surface Water Entering and Exiting Constructed Wetlands Treated with Metal-Based Coagulants, Twitchell Island, California

Mercury, Monomethyl Mercury, and Dissolved Organic Carbon Concentrations in Surface Water Entering and Exiting Constructed Wetlands Treated with Metal-Based Coagulants, Twitchell Island, California

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Mining’s Toxic Legacy: An Initiative to Address Mining Toxins in the Sierra Nevada

Mining’s Toxic Legacy: An Initiative to Address Mining Toxins in the Sierra Nevada

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Pulse of the Delta 2012

Pulse of the Delta 2012

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Quantifying the Eroded Volume of Mercury-Contaminated Sediment Using Terrestrial Laser Scanning at Stocking Flat, Deer Creek, Nevada County, California, 2010–13

Quantifying the Eroded Volume of Mercury-Contaminated Sediment Using Terrestrial Laser Scanning at Stocking Flat, Deer Creek, Nevada County, California, 2010–13

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Reducing Methylmercury Accumulation in the Food Webs of San Francisco Bay and Its Local Watersheds

Reducing Methylmercury Accumulation in the Food Webs of San Francisco Bay and Its Local Watersheds

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Sources, Pathways and Loadings: Multi-Year Synthesis with a Focus on PCBs and Hg

Sources, Pathways and Loadings: Multi-Year Synthesis with a Focus on PCBs and Hg

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Summary of the MeHg Panels of the 2004 CalFed Science Conference

Summary of the MeHg Panels of the 2004 CalFed Science Conference

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