Jacob A Fleck
Science and Products
High Resolution Temporal and Spatial Mapping of Mercury and Methylmercury in Surface Waters of the Sacramento – San Joaquin Delta
Mercury (Hg) is a contaminant of significant concern in the San Francisco Bay-Delta estuary and watershed (Bay-Delta). The formation, fate, and transport of methylmercury (MeHg), a particularly toxic organic form of Hg that readily bioaccumulates in wildlife, has been studied extensively throughout the system. However, there is widespread recognition of the need for more comprehensive...
Assessment of environmental impacts of mercury treatability test using suction dredging, South Yuba River
The goals of the BLM suction dredging treatability study are to (1) assess the effectiveness of suction dredging in removing mercury from the environment and (2) assess potential impacts of suction dredging with regard to discharging mercury-contaminated suspended sediment to the aquatic environment.
Mercury and Dissolved Organic Matter in Delta Wetlands
Between 1860 and 1914, hydraulic mining activities sent more than 800,000,000 cubic yards of mercury-laden sediment into the Delta altering the landscape, water flows, and contributing to the leveeing and reclamation of the Delta's marshes. Transport of mercury from historic mining areas continues today. The sedimentary supply of mercury to the Delta and in Delta sediments (cinnabar,...
A Non-Point Source Of Contaminants To The Estuarine Food Web: Mobilized Particles From The Intertidal Zone
The San Francisco Bay and Sacramento-San Joaquin Delta (Bay-Delta) region is a highly urbanized and contaminated estuary with a valuable commercial and recreational fishery (Nichlos et al., 1986; SFEI, 2004). Many fish and birds in the San Francisco Estuary exhibit high levels of contaminants (metals and organic pollutants), which have been shown to affect their behavior and reproductive...
Methylmercury cycling and export from agricultural and natural wetlands in the Yolo Bypass
The purpose of the work conducted by the USGS California Water Science Center is to help guide Yolo Wildlife Area management practices by identifying the relationships between management effects on dissolved organic matter properties and the resulting role of dissolved organic matter in mercury methylation and biotic uptake measured by the cooperating USGS scientists. The information gathered...
Investigation of Linkages Between Management Practices Used in Sacramento-San Joaquin Delta Rice Production and Loads of Dissolved Organic Matter and Disinfection Byproduct Precursors
The primary objective of this study is to expand our current understanding of how to manage rice production in the Sacramento-San Joaquin Delta in a manner that minimizes loads of water quality contaminants to Delta waters.
Evaluating coagulation techniques to reduce the transport of Hg from mine-affected and active geothermal Hg-source watersheds
Our objective is to determine the effectiveness of coagulation and adsorption techniques in removing mercury from contaminated surface waters of the Cache Creek watershed.
Assessment of methyl mercury (MeHg) release from sediment formed in wetland treatment cells designed to remove mercury from surface waters using in situ coagulation
Our objective is to determine the relative propensity of sediment material formed under two different in situ coagulation treatments (iron sulfate, polyaluminum chloride) to release MeHg into surface waters under environmentally relevant conditions that may affect flocculant stability and MeHg production rates.
Monitoring Mercury and Methylmercury in Water, Sediment and Biota in Combie Reservoir Before and After Dredging and Mercury Removal
Dredging to maintain water storage capacity by the Nevada Irrigation District (NID) occurred at Lake Combie reservoir, one of several reservoirs along the Bear River, California over the past 40 years on an as-needed basis to maintain water storage capacity. Maintenance dredging operations were halted by the Central Valley Regional Water...
Wetland management strategy to reduce mercury export in water and bioaccumulation in fish
Wetland environments provide numerous ecosystem services but also facilitate methylmercury (MeHg) production and bioaccumulation. We developed a wetland‐management technique to reduce MeHg concentrations in wetland fish and water. We physically modified seasonal wetlands by constructing open‐ and deep‐water treatment cells at the downstream end of...
Ackerman, Joshua T.; Fleck, Jacob; Eagles-Smith, Collin A.; Marvin-DiPasquale, Mark C.; Windham-Myers, Lisamarie; Herzog, Mark P.; McQuillen, Harry L.
Coagulant and sorbent efficacy in removing mercury from surface waters in the Cache Creek watershed, California
Cache Creek drains part of northern California’s Coast Ranges and is an important source of mercury (Hg) to the Sacramento–San Joaquin Delta. Cache Creek is contaminated with Hg from several sources, including historical Hg and gold mines, native Hg in the soils, and active mineral springs. In laboratory experiments in a study conducted by the U.S...
De Parsia, Erica R.; Fleck, Jacob A.; Krabbenhoft, David P.; Hoang, Kim; Roth, David; Randall, Paul
Geochemical data for water, streambed sediment, and fish tissue from the Sierra Nevada Mercury Impairment Project, 2011–12
This report presents geochemical data for surface water, streambed sediment, and fish tissue samples collected during low-flow conditions in 20 to 24 Sierra Nevada streams during 2011 and 2012. The dataset is part of a larger study designed to assess the factors that control mercury concentrations in fish tissue and to develop a model that...
Stumpner, Elizabeth B.; Alpers, Charles N.; Marvin-DiPasquale, Mark C.; Agee, Jennifer L.; Kakouros, Evangelos; Arias, Michelle R.; Kieu, Le H.; Roth, David A.; Slotton, Darrell G.; Fleck, Jacob A.
Procedures for using the Horiba Scientific Aqualog® fluorometer to measure absorbance and fluorescence from dissolved organic matter
Advances in spectroscopic techniques have led to an increase in the use of optical measurements (absorbance and fluorescence) to assess dissolved organic matter composition and infer sources and processing. Although optical measurements are easy to make, they can be affected by many variables rendering them less comparable, including by...
Hansen, Angela M.; Fleck, Jacob; Kraus, Tamara E. C.; Downing, Bryan D.; von Dessonneck, Travis; Bergamaschi, Brian Methylmercury dynamics in Upper Sacramento Valley rice fields with low background soil mercury levels
Few studies have considered how methylmercury (MeHg, a toxic form of Hg produced in anaerobic soils) production in rice (Oryza sativa L.) fields can affect water quality, and little is known about MeHg dynamics in rice fields. Surface water MeHg and total Hg (THg) imports, exports, and storage were studied in two commercial rice fields in the...
Tanner, K. Christy; Windham-Myers, Lisamarie; Marvin-DiPasquale, Mark C.; Fleck, Jacob; Tate, Kenneth W.; Linquist, Bruce A.
Mercury on a landscape scale—Balancing regional export with wildlife health
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-...
Marvin-DiPasquale, Mark C.; Windham-Myers, Lisamarie; Fleck, Jacob A.; Ackerman, Joshua T.; Eagles-Smith, Collin A.; McQuillen, Harry Alternate wetting and drying decreases methylmercury in flooded rice (Oryza sativa) systems
In flooded soils, including those found in rice (Oryza sativa L.) fields, microbes convert inorganic Hg to more toxic methylmercury (MeHg). Methylmercury is accumulated in rice grain, potentially affecting health. Methylmercury in rice field surface water can bioaccumulate in wildlife. We evaluated how introducing aerobic periods into an...
Tanner, K. Christy; Windham-Myers, Lisamarie; Marvin-DiPasquale, Mark C.; Fleck, Jacob; Linquist, Bruce A. The contribution of rice agriculture to methylmercury in surface waters: A review of data from the Sacramento Valley, California
Methylmercury (MeHg) is a bioaccumulative pollutant produced in and exported from flooded soils, including those used for rice (Oriza sativa L.) production. Using unfiltered aqueous MeHg data from MeHg monitoring programs in the Sacramento River watershed from 1996 to 2007, we assessed the MeHg contribution from rice systems to the Sacramento...
Tanner, K. Christy; Windham-Myers, Lisamarie; Fleck, Jacob; Tate, Kenneth W.; McCord, Stephen A.; Linquist, Bruce A. Mercury and methylmercury in aquatic sediment across western North America
Large-scale assessments are valuable in identifying primary factors controlling total mercury (THg) and monomethyl mercury (MeHg) concentrations, and distribution in aquatic ecosystems. Bed sediment THg and MeHg concentrations were compiled for > 16,000 samples collected from aquatic habitats throughout the West between 1965 and 2013. The...
Fleck, Jacob; Marvin-DiPasquale, Mark C.; Eagles-Smith, Collin A.; Ackerman, Joshua T.; Lutz, Michelle A.; Tate, Michael T.; Alpers, Charles N.; Hall, Britt D.; Krabbenhoft, David P.; Eckley, Chris S. Mercury in western North America: A synthesis of environmental contamination, fluxes, bioaccumulation, and risk to fish and wildlife
Western North America is a region defined by extreme gradients in geomorphology and climate, which support a diverse array of ecological communities and natural resources. The region also has extreme gradients in mercury (Hg) contamination due to a broad distribution of inorganic Hg sources. These diverse Hg sources and a varied landscape create a...
Eagles-Smith, Collin A.; Wiener, James G.; Eckley, Chris S.; Willacker, James J.; Evers, David C.; Marvin-DiPasquale, Mark C.; Obrist, Daniel; Fleck, Jacob; Aiken, George R.; Lepak, Jesse M.; Jackson, Allyson K.; Webster, Jackson; Stewart, Robin; Davis, Jay; Alpers, Charles N.; Ackerman, Joshua T. Optical properties of dissolved organic matter (DOM): Effects of biological and photolytic degradation
Advances in spectroscopic techniques have led to an increase in the use of optical properties (absorbance and fluorescence) to assess dissolved organic matter (DOM) composition and infer sources and processing. However, little information is available to assess the impact of biological and photolytic processing on the optical properties of...
Hansen, Angela; Kraus, Tamara E. C.; Pellerin, Brian; Fleck, Jacob; Downing, Bryan D.; Bergamaschi, Brian Spatial and temporal patterns of mercury concentrations in freshwater fish across the Western United States and Canada
Methylmercury contamination of fish is a global threat to environmental health. Mercury (Hg) monitoring programs are valuable for generating data that can be compiled for spatially broad syntheses to identify emergent ecosystem properties that influence fish Hg bioaccumulation. Fish total Hg (THg) concentrations were evaluated across the Western...
Eagles-Smith, Collin A.; Ackerman, Joshua T.; Willacker, James J.; Tate, Michael T.; Lutz, Michelle A.; Fleck, Jacob; Stewart, Robin; Wiener, James G.; Evers, David C.; Lepak, Jesse M.; Davis, Jay A.; Pritz, Colleen Flanagan
Reducing Mercury Loads in The Cosumnes River
The Cosumnes River watershed has seasonal, non-point source hotspots for total mercury and methylmercury production, which discharge to the Sacramento-San Joaquin River Delta in north-central California. To reduce mercury loads to the Delta, researchers created open-water deep cells at the downstream end of wetlands.