Jacob A Fleck - California Water Science Center
Science and Products
Remote Sensing of Mercury Pollution in South San Francisco Bay
San Francisco Bay has a long history of being subject to natural resources exploitation and pollution. Ongoing flux of contaminants into the bay, legacy pollution from the Gold Rush era and structural modifications still influence the natural ecosystem today. This project aims to map multiple forms (i.e. species) of mercury -- one of the major contaminants in the bay -- to help inform restoration...
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 monitoring...
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, metacinnabar...
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 success...
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 will...
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 Quality Control Board (CVRWQCB) in 2002 because of elevated...
Mercury cycling, bioaccumulation, and risk across western North America: a landscape scale synthesis linking long-term datasets
Mercury (Hg) is a serious environmental problem that is impacting ecological and human health on a global scale. However, local and regional processes are largely responsible for producing methylmercury, which drives ecological risk. This is particularly true in western North America where the combination of diverse landscapes, habitat types, climates, and Hg sources may disproportionally impact t
High resolution and discrete temporal and spatial water-quality measurements in support of modeling mercury and methylmercury concentrations in surface waters of the Sacramento-San Joaquin River Delta
The Sacramento / San Joaquin River Delta (SSJRD) is contaminated with legacy mercury (Hg) from historical mining and mineral processing activities throughout the watershed, as well as from contemporary atmospheric and industrial inputs. The current project was designed for the purpose of developing high-resolution spatial and temporal models for estimating concentrations of mercury species in surf
Data from the development and testing of a multiparameter standard solution for fluorescent dissolved organic matter (fDOM) and algal fluorescence (fChl) (ver. 2.0, July 2022)
Optical sensors measuring fluorescence of non-biological sources (e.g., dissolved organic matter, wastewater, hydrocarbons, fluorescent dyes, etc.; hereafter referred to as fDOM) are increasingly used in water quality studies because they provide proxy measurements for a variety of contaminants and constituents of concern including metals, wastewater effluent, and DOM (measured in the lab as disso
Shallow Sediment Geochemistry in a Mercury-Contaminated Multi-Habitat Floodplain: Cache Creek Settling Basin, Yolo County, California (version 2.0, August 2021)
The Cache Creek Settling Basin (CCSB) is a 13.3 km2 leveed basin located at the terminal drainage of the Cache Creek watershed, immediately NE of the town of Woodland (Yolo County), California and approximately 18 km NW of Sacramento, California. The basin was constructed by the U.S. Army Corps of Engineers (completed in 1937 and modified in 1993) for the purpose of trapping suspended sediment tra
Data from the development and testing of a multiparameter standard solution for fluorescent dissolved organic matter (fDOM) and algal fluorescence (fChl)
Optical sensors measuring fluorescent dissolved organic matter (fDOM) are increasingly being used in water quality studies because they provide proxy measurements for dissolved organic matter concentrations (DOC). Similarly, chlorophyll-a (chl-a) fluorescence sensors have gained popularity as a means to measure phytoplankton concentration, biomass, and even primary productivity using various appro
Surface-Water Geochemistry of Mercury, Methylmercury, Nutrients, and other Constituents in Clear Lake, Lake County, California, July 2019
Clear Lake is a 180 km2 freshwater lake located in the California Coast Range, approximately 120 km northwest of Sacramento. The lake supports a wide variety of fish and bird species and is a very popular sport-fishing destination. However, fish consumption advisories associated with mercury (Hg) contamination exist for several popular recreational species. The lake is comprised of three main regi
Geochemistry of shallow sediment including mercury, methylmercury and other constituents in the Cache Creek Settling Basin, Yolo County, California, 2010-16
The Cache Creek Settling Basin (CCSB) is a 13.3 km2 leveed basin located at the terminal drainage of the Cache Creek watershed, immediately NE of the town of Woodland (Yolo County), California and approximately 18 km NW of Sacramento, California. The basin was constructed by the U.S. Army Corps of Engineers (completed in 1937 and modified in 1993) for the purpose of trapping suspended sediment tra
Filter Total Items: 35
Field techniques for fluorescence measurements targeting dissolved organic matter, hydrocarbons, and wastewater in environmental waters: Principles and guidelines for instrument selection, operation and maintenance, quality assurance, and data reporting
The use of field deployable fluorescence sensors by the U.S. Geological Survey has become increasingly common for a wide variety of surface water and groundwater investigations. This report addresses field deployable fluorometers that measure the fluorescence response of various substances in water exposed to incident light generated by the sensor. An introduction to the basic principles of field
Authors
Amanda Booth, Jacob Fleck, Brian A. Pellerin, Angela Hansen, Alexandra Etheridge, Guy M. Foster, Jennifer L. Graham, Brian A. Bergamaschi, Kurt D. Carpenter, Bryan D. Downing, Stewart A. Rounds, JohnFranco Saraceno
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 seasonal wetlands to promote naturally occurring M
Authors
Joshua T. Ackerman, Jacob Fleck, Collin A. Eagles-Smith, Mark C. Marvin-DiPasquale, Lisamarie Windham-Myers, Mark P. Herzog, Harry L. McQuillen
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. Geological Survey, in cooperation with the U.S. E
Authors
Erica R. De Parsia, Jacob A. Fleck, David P. Krabbenhoft, Kim Hoang, David Roth, Paul Randall
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 predicts mercury concentration in the tissue of selected f
Authors
Elizabeth B. Stumpner, Charles N. Alpers, Mark C. Marvin-DiPasquale, Jennifer L. Agee, Evangelos Kakouros, Michelle R. Arias, Le H. Kieu, David A. Roth, Darrell G. Slotton, Jacob A. Fleck
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 inconsistencies in sample collection (for example, filter por
Authors
Angela M. Hansen, Jacob Fleck, Tamara E. C. Kraus, Bryan D. Downing, Travis von Dessonneck, Brian A. Bergamaschi
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 Sacramento Valley, California, where soil THg was low (
Authors
K. Christy Tanner, Lisamarie Windham-Myers, Mark C. Marvin-DiPasquale, Jacob Fleck, Kenneth W. Tate, Bruce A. Linquist
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-point sources, particularly the expansive wetlands cons
Authors
Mark C. Marvin-DiPasquale, Lisamarie Windham-Myers, Jacob A. Fleck, Joshua T. Ackerman, Collin A. Eagles-Smith, Harry McQuillen
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 otherwise continuously flooded rice growing season affects M
Authors
K. Christy Tanner, Lisamarie Windham-Myers, Mark C. Marvin-DiPasquale, Jacob Fleck, Bruce A. Linquist
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 River. Using a mixed-effects regression analysis, we co
Authors
K. Christy Tanner, Lisamarie Windham-Myers, Jacob Fleck, Kenneth W. Tate, Stephen A. McCord, Bruce A. Linquist
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 influence of aquatic feature type (canals, estuaries, lakes
Authors
Jacob Fleck, Mark C. Marvin-DiPasquale, Collin A. Eagles-Smith, Joshua T. Ackerman, Michelle A. Lutz, Michael T. Tate, Charles N. Alpers, Britt D. Hall, David P. Krabbenhoft, Chris S. Eckley
By
Ecosystems Mission Area, Water Resources Mission Area, Environmental Health Program, Toxic Substances Hydrology, California Water Science Center, Forest and Rangeland Ecosystem Science Center, John Wesley Powell Center for Analysis and Synthesis, Upper Midwest Water Science Center, Mercury Research Laboratory
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 unique and complex mosaic of ecological risk from
Authors
Collin A. Eagles-Smith, James G. Wiener, Chris S. Eckley, James J. Willacker, David C. Evers, Mark C. Marvin-DiPasquale, Daniel Obrist, Jacob Fleck, George R. Aiken, Jesse M. Lepak, Allyson K. Jackson, Jackson Webster, Robin Stewart, Jay Davis, Charles N. Alpers, Joshua T. Ackerman
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 original DOM source materials. We measured changes in comm
Authors
Angela Hansen, Tamara E. C. Kraus, Brian Pellerin, Jacob Fleck, Bryan D. Downing, Brian A. Bergamaschi
Science and Products
- Science
Remote Sensing of Mercury Pollution in South San Francisco Bay
San Francisco Bay has a long history of being subject to natural resources exploitation and pollution. Ongoing flux of contaminants into the bay, legacy pollution from the Gold Rush era and structural modifications still influence the natural ecosystem today. This project aims to map multiple forms (i.e. species) of mercury -- one of the major contaminants in the bay -- to help inform restoration...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 monitoring...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, metacinnabar...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 success...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 will...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 Quality Control Board (CVRWQCB) in 2002 because of elevated...Mercury cycling, bioaccumulation, and risk across western North America: a landscape scale synthesis linking long-term datasets
Mercury (Hg) is a serious environmental problem that is impacting ecological and human health on a global scale. However, local and regional processes are largely responsible for producing methylmercury, which drives ecological risk. This is particularly true in western North America where the combination of diverse landscapes, habitat types, climates, and Hg sources may disproportionally impact t - Data
High resolution and discrete temporal and spatial water-quality measurements in support of modeling mercury and methylmercury concentrations in surface waters of the Sacramento-San Joaquin River Delta
The Sacramento / San Joaquin River Delta (SSJRD) is contaminated with legacy mercury (Hg) from historical mining and mineral processing activities throughout the watershed, as well as from contemporary atmospheric and industrial inputs. The current project was designed for the purpose of developing high-resolution spatial and temporal models for estimating concentrations of mercury species in surfData from the development and testing of a multiparameter standard solution for fluorescent dissolved organic matter (fDOM) and algal fluorescence (fChl) (ver. 2.0, July 2022)
Optical sensors measuring fluorescence of non-biological sources (e.g., dissolved organic matter, wastewater, hydrocarbons, fluorescent dyes, etc.; hereafter referred to as fDOM) are increasingly used in water quality studies because they provide proxy measurements for a variety of contaminants and constituents of concern including metals, wastewater effluent, and DOM (measured in the lab as dissoShallow Sediment Geochemistry in a Mercury-Contaminated Multi-Habitat Floodplain: Cache Creek Settling Basin, Yolo County, California (version 2.0, August 2021)
The Cache Creek Settling Basin (CCSB) is a 13.3 km2 leveed basin located at the terminal drainage of the Cache Creek watershed, immediately NE of the town of Woodland (Yolo County), California and approximately 18 km NW of Sacramento, California. The basin was constructed by the U.S. Army Corps of Engineers (completed in 1937 and modified in 1993) for the purpose of trapping suspended sediment traData from the development and testing of a multiparameter standard solution for fluorescent dissolved organic matter (fDOM) and algal fluorescence (fChl)
Optical sensors measuring fluorescent dissolved organic matter (fDOM) are increasingly being used in water quality studies because they provide proxy measurements for dissolved organic matter concentrations (DOC). Similarly, chlorophyll-a (chl-a) fluorescence sensors have gained popularity as a means to measure phytoplankton concentration, biomass, and even primary productivity using various approSurface-Water Geochemistry of Mercury, Methylmercury, Nutrients, and other Constituents in Clear Lake, Lake County, California, July 2019
Clear Lake is a 180 km2 freshwater lake located in the California Coast Range, approximately 120 km northwest of Sacramento. The lake supports a wide variety of fish and bird species and is a very popular sport-fishing destination. However, fish consumption advisories associated with mercury (Hg) contamination exist for several popular recreational species. The lake is comprised of three main regiGeochemistry of shallow sediment including mercury, methylmercury and other constituents in the Cache Creek Settling Basin, Yolo County, California, 2010-16
The Cache Creek Settling Basin (CCSB) is a 13.3 km2 leveed basin located at the terminal drainage of the Cache Creek watershed, immediately NE of the town of Woodland (Yolo County), California and approximately 18 km NW of Sacramento, California. The basin was constructed by the U.S. Army Corps of Engineers (completed in 1937 and modified in 1993) for the purpose of trapping suspended sediment tra - Publications
Filter Total Items: 35
Field techniques for fluorescence measurements targeting dissolved organic matter, hydrocarbons, and wastewater in environmental waters: Principles and guidelines for instrument selection, operation and maintenance, quality assurance, and data reporting
The use of field deployable fluorescence sensors by the U.S. Geological Survey has become increasingly common for a wide variety of surface water and groundwater investigations. This report addresses field deployable fluorometers that measure the fluorescence response of various substances in water exposed to incident light generated by the sensor. An introduction to the basic principles of fieldAuthorsAmanda Booth, Jacob Fleck, Brian A. Pellerin, Angela Hansen, Alexandra Etheridge, Guy M. Foster, Jennifer L. Graham, Brian A. Bergamaschi, Kurt D. Carpenter, Bryan D. Downing, Stewart A. Rounds, JohnFranco SaracenoWetland 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 seasonal wetlands to promote naturally occurring MAuthorsJoshua T. Ackerman, Jacob Fleck, Collin A. Eagles-Smith, Mark C. Marvin-DiPasquale, Lisamarie Windham-Myers, Mark P. Herzog, Harry L. McQuillenCoagulant 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. Geological Survey, in cooperation with the U.S. EAuthorsErica R. De Parsia, Jacob A. Fleck, David P. Krabbenhoft, Kim Hoang, David Roth, Paul RandallGeochemical 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 predicts mercury concentration in the tissue of selected fAuthorsElizabeth B. Stumpner, Charles N. Alpers, Mark C. Marvin-DiPasquale, Jennifer L. Agee, Evangelos Kakouros, Michelle R. Arias, Le H. Kieu, David A. Roth, Darrell G. Slotton, Jacob A. FleckProcedures 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 inconsistencies in sample collection (for example, filter porAuthorsAngela M. Hansen, Jacob Fleck, Tamara E. C. Kraus, Bryan D. Downing, Travis von Dessonneck, Brian A. BergamaschiMethylmercury 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 Sacramento Valley, California, where soil THg was low (AuthorsK. Christy Tanner, Lisamarie Windham-Myers, Mark C. Marvin-DiPasquale, Jacob Fleck, Kenneth W. Tate, Bruce A. LinquistMercury 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-point sources, particularly the expansive wetlands consAuthorsMark C. Marvin-DiPasquale, Lisamarie Windham-Myers, Jacob A. Fleck, Joshua T. Ackerman, Collin A. Eagles-Smith, Harry McQuillenAlternate 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 otherwise continuously flooded rice growing season affects MAuthorsK. Christy Tanner, Lisamarie Windham-Myers, Mark C. Marvin-DiPasquale, Jacob Fleck, Bruce A. LinquistThe 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 River. Using a mixed-effects regression analysis, we coAuthorsK. Christy Tanner, Lisamarie Windham-Myers, Jacob Fleck, Kenneth W. Tate, Stephen A. McCord, Bruce A. LinquistMercury 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 influence of aquatic feature type (canals, estuaries, lakesAuthorsJacob Fleck, Mark C. Marvin-DiPasquale, Collin A. Eagles-Smith, Joshua T. Ackerman, Michelle A. Lutz, Michael T. Tate, Charles N. Alpers, Britt D. Hall, David P. Krabbenhoft, Chris S. EckleyByEcosystems Mission Area, Water Resources Mission Area, Environmental Health Program, Toxic Substances Hydrology, California Water Science Center, Forest and Rangeland Ecosystem Science Center, John Wesley Powell Center for Analysis and Synthesis, Upper Midwest Water Science Center, Mercury Research LaboratoryMercury 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 unique and complex mosaic of ecological risk fromAuthorsCollin A. Eagles-Smith, James G. Wiener, Chris S. Eckley, James J. Willacker, David C. Evers, Mark C. Marvin-DiPasquale, Daniel Obrist, Jacob Fleck, George R. Aiken, Jesse M. Lepak, Allyson K. Jackson, Jackson Webster, Robin Stewart, Jay Davis, Charles N. Alpers, Joshua T. AckermanOptical 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 original DOM source materials. We measured changes in commAuthorsAngela Hansen, Tamara E. C. Kraus, Brian Pellerin, Jacob Fleck, Bryan D. Downing, Brian A. Bergamaschi - News