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S. J. Deverel

Publications and source records attributed to S. J. Deverel.

At least 19 recordsLinked to original sources
USGS2010

Processes affecting the distribution of selenium in shallow groundwater of agricultural areas, western San Joaquin Valley, California

A study was undertaken to evaluate the processes affecting the chemistry of shallow groundwater associated with agricultural drainage systems in the western San Joaquin Valley, California. The study was prompted by a need for an understanding of selenium mobility in areas having high selenium concentrations in shallow groundwater. Groundwater samples were collected along transects in three artificially drained fields where the age of the drainage system varied (15, 6, and 1.5 years). Selenium concentrations in the drain water also varied (430, 58, and 3700 μg/L, respectively). Isotopic enrichment and chemical composition of the groundwater samples indicate that saline- and selenium-enriched water has evolved as a result of evaporation or transpiration of groundwater. This evaporated, isotopically enriched water is being displaced by more recent, less saline irrigation water percolating through the root zone. This displacement seems to be a process whereby sodium chloride and sodium sulfate water is being replaced by more dilute calcium sulfate and calcium bicarbonate water.

California↗
USGS2008

Groundwater flow and solute movement to drain laterals, western San Joaquin Valley, California: 1. Geochemical assessment

A study was undertaken to quantitatively evaluate the hydrologic processes affecting the chemical and isotopic composition of drain lateral water in a drained agricultural field in the western San Joaquin Valley, California. The results elucidate the process of mixing of deep and shallow groundwater (below and within 6 m from land surface) entering the drain laterals. The deep groundwater was subject to evapoconcentration prior to drainage system installation and has been displaced downward (to depths greater than 6 m) in the groundwater system. The proportions of deep and shallow groundwater entering the drain laterals was calculated from the end-member oxygen 18 compositions determined in groundwater samples. The percentage of total drain lateral flow which is deep groundwater flow is about 30% for the shallow drain lateral (1.8 m below land surface) (drain lateral 1)) and 60% for the deep drain lateral (2.7 m below land surface (drain lateral 2)). During irrigation, the percentages of deep groundwater flow decrease to 0 and 30% for the shallow and deep drain laterals, respectively. Selenium concentrations in drain lateral waters decrease during irrigation but selenium loads increase. Total estimated annual loads were 1.1 and 5.4 kg of selenium for drain laterals 1 and 2, respectively. Substantial percentages of the annual load occurred during 8 days of irrigation, 23 and 9% for drain laterals 1 and 2, respectively.

California↗
USGS2008

Groundwater flow and solute movement to drain laterals, western San Joaquin Valley, California: 2. Quantitative hydrologic assessment

Groundwater flow modeling was used to quantitatively assess the hydrologic processes affecting ground water and solute movement to drain laterals. Modeling results were used to calculate the depth distribution of groundwater flowing into drain laterals at 1.8 m (drain lateral 1) and 2.7 m (drain lateral 2) below land surface. The simulations indicated that under nonirrigated conditions about 89% of the flow in drain lateral 2 was from groundwater originating from depths greater than 6 m below land surface. The deep groundwater has higher selenium concentrations than shallow groundwater. Simulation of irrigated conditions indicates that as recharge (deep percolation) increases, the proportional contribution of deep groundwater to drain lateral flow decreases. Groundwater flow paths and travel times estimated from the simulation results indicate that groundwater containing high concentrations of selenium (greater than 780 μg L −1 ) probably will continue to enter drain lateral 2 for decades.

California↗
USGS2003

Preliminary assessment of DOC and THM precursor loads from a freshwater restored wetland, an agricultural field, and a tidal wetland in the Sacramento-San Joaquin River Delta

Water exported from the Sacramento-San Joaquin River Delta supplies drinking water to more than 22 million people in California. At certain times of the year, Delta waters contain relatively high concentrations of dissolved organic carbon (DOC) and bromide. During these times, chlorination of Delta water for drinking water disinfection will form disinfection byproducts, such as trihalomethanes (THMs), that can exceed the U.S. Environmental Protection Agency's maximum contaminant level for THMs of 80 mg/L. Important sources of DOC and THM precursors (types of DOC that form THMs when chlorinated) to the Delta include rivers, drainage water from peat islands, water from wetlands and areas with extensive riparian vegetation, and in-channel growth of algae and macrophytes. Due to proposed ecosystem restoration and creation of wetlands in the Delta, there is an urgent need for information on the relative loads of DOC and THM precursors produced from three different land uses: restored wetlands constructed for subsidence mitigation, tidal wetlands, and agricultural operations. We have been conducting research in the Delta to provide this information. A restored wetland and agricultural field located on Twitchell Island, and a tidal wetland on Browns Island have been monitored for flow, DOC, and THM precursors. Initial results indicate that the loads of DOC and THM precursors are similar for the restored wetland (surface water only) and the agricultural field. These land uses produce DOC loads of about 14 and 11 g C/m2/yr, respectively, and THM precursor loads of about 1.7 and 1.0 g THM/m2/yr, respectively. Estimates of DOC and THM precursor loads for the tidal wetland site on Browns Island and seepage associated with the restored wetland are being developed.

Conference Paper↗
USGS2002

Distribution and mobility of selenium and other trace elements in shallow groundwater of the western San Joaquin Valley, California

Samples of shallow groundwater that underlies much of the irrigated area in the western San Joaquin Valley, CA, were analyzed for various major ions and trace elements, including selenium. Concentrations of the major ions generally were similar for groundwater collected in the two primary geologic zones - the alluvial fan and basin trough. Selenium concentrations are significantly (α = 0.05) higher in the groundwater of the alluvial-fan zone than in that of the basin-trough zone. The concentrations of oxyanion trace elements were significantly correlated (α = 0.05) with groundwater salinity, but the correlations between selenium and salinity and between molybdenum and salinity were significantly different (α = 0.05) in the alluvial-fan geologic zone compared with those in the basin-trough geologic zone. The evidence suggests that the main factors affecting selenium concentrations in the shallow groundwater are the degree of groundwater salinity and the geologic source of the alluvial soil material.

California↗
USGS1991

Selenium mobility and distribution in irrigated and nonirrigated alluvial soils

Dissolution and leaching of soil salts by irrigation water is a primary source of Se to shallow groundwater in the western San Joaquin Valley, California. In this study, the mobility and distribution of selenite and selenate in soils with different irrigation and drainage histories was evaluated using sorption experiments and an advection-dispersion model. The sorption studies showed that selenate (15–12400 µg Se L −1 ) is not adsorbed to soil, whereas selenite (10–5000 µg Se L −1 ) is rapidly adsorbed. The time lag between adsorption and desorption of selenite is considerable, indicating a dependence of reaction rate on reaction direction (hysteresis). Selenite adsorption and desorption isotherms were different, and both were described with the Freundlich equation. Model results and chemical analyses of extracts from the soil samples showed that selenite is resistant to leaching and therefore can represent a potential long-term source of Se to groundwater. In contrast, selenate behaves as a conservative constituent under alkaline and oxidized conditions and is easily leached from soil.

Soil Science Society of America Journal↗
USGS1990

Evaluation of selenium mobility in soil using sorption experiments and a numerical model, western San Joaquin Valley, California

Sorption experiments and a numerical model were used to assess the effects of irrigation and drainage on the depth distribution of selenite and selenate in soils from the western San Joaquin Valley, California. The sorption studies show that selenate (15 to 12,400 micrograms per liter of selenium) is not adsorbed to soil, whereas selenite (10 to 5,000 micrograms per liter of selenium) is rapidly adsorbed. The time lag between adsorption and desorption is considerable, indicating nonreversible sorption, and an equation describing the desorption reaction is determined by the concentration of adsorbed selenite prior to desorption. A numerical model was used to qualitatively evaluate the nonreversible sorption reaction and its affect on selenite mobility during leaching by irrigation water. Model results show that selenite is resistant to leaching and therefore can represent a potential long-term source of selenium to ground water. In contrast, selenate behaves as a conservative constituent under alkaline and oxidized conditions and is easily leached from soil. Chemical analyses of soils from irrigated and non-irrigated sites confirm the experimental and modeling results. Increasing salinity and soluble concentrations of selenate at a site irrigated for more than 40 years indicated leaching and downward displacement by irrigation water. Decreasing salinity and soluble concentrations of selenate at a nonirrigated site probably resulted from evaporation from the shallow water table. Adsorbed selenium in the irrigated and nonirrigated soils is mostly selenite and has been minimally affected by irrigation and drainage.

California↗
USGS1990

Ground-water flow and solute movement to drain laterals, western San Joaquin Valley, California; I, Geochemical assessment

A study was undertaken to quantitatively evaluate the hydrologic processes affecting the chemical and isotopic composition of drain-lateral water in a drained agricultural field in the western San Joaquin Valley, California. The results of chemical and isotopic analysis of the samples and analysis of hydraulic-head data and drain-lateral flow data elucidate the process of mixing of deep and shallow ground water entering the drain laterals. The deep ground water was subject to partial evaporation prior to drainage-system installation and has been displaced downward (at depths greater than 6 meters) in the ground-water system. This ground water is flowing toward the drain laterals. The percentage of the deep, isotopically enriched ground water entering the drain laterals varies with time and between drain laterals. The percentage of the total drain-lateral flow, which is deep ground-water flow, is about 30 percent for the shallow drain lateral (1.8 meters below land surface) and 60 percent for the deep drain lateral (2.7 meters below land surface). During irrigation, the percentages decrease to 0 and 30 percent for the shallow and deep drain laterals, respectively. Selenium loads in the drain laterals vary with time and between drain laterals. The selenium load for the shallow drain lateral (68 kilograms) during 1 year is 21 percent of the load for the deep drain lateral (332 kilograms) because it collects less deep, high-selenium ground water and does not flow continuously. Although selenium concentrations in the drain-lateral water decreased during irrigation, selenium loads increased substantially during a preplant irrigation because of increased flow into the drain laterals. The selenium loads during 8 days of irrigation represented a substantial percentage (25 percent for the shallow drain lateral and 11 percent for the deep drain lateral) of the total selenium load for 1 year.

California↗
USGS1990

Ground-water flow and solute movement to drain laterals, western San Joaquin Valley, California; II, Quantitative hydrologic assessment

Ground-water-flow modeling was used to estimate ground-water-flow paths and traveltimes to quantitatively assess the hydrologic processes affecting ground water and solute movement to drain laterals. Modeling results were used to calculate the depth distribution of ground water flowing into drain laterals at 1.8 meters (drain lateral 1) and 2.7 meters (drain lateral 2) below land surface. The simulations indicated that under nonirrigated conditions about 89 percent of the flow in drain lateral 2 was from ground water originating from depths greater than 6 meters below land surface. The deep ground water has higher selenium concentrations than shallow ground water. Simulation of irrigated conditions indicates that as recharge increases, the proportion of deep ground water entering the drain laterals decreases. Ground-water-flow modeling also was used to estimate selenium loads in drain laterals for varying drain-lateral flow rates. Simulated loads are in general agreement with measured loads and increase with increasing drain-lateral flow. Simulations further indicate ground water that contains high-selenium concentrations probably will continue to enter drain lateral 2 for more than 8 years.

California↗
USGS1989

Relation of salinity and selenium in shallow groundwater to hydrologic and geochemical processes, Western San Joaquin Valley, California

Salinity and selenium concentrations in shallow groundwater of the western San Joaquin Valley, California, are related to the geomorphology and hydrology of the alluvial fans. The highest salinity and selenium concentrations in shallow groundwater occur in alluvium deposited by ephemeral streams and at the margins of the major alluvial fans, where there were naturally saline, fine-grained soils. Low-to-moderate salinity and selenium concentrations in shallow groundwater are associated with upper and middle areas of the major alluvial fans deposited by intermittent streams. Areas with the most naturally saline soils have been irrigated in the last 40 years. These are now the areas of highest salinity and selenium concentrations in the shallow groundwater. Present-day (1986) groundwater salinity is spatially correlated with natural soil salinity in these areas. Isotopic data indicate that the highest salinity and selenium concentrations in groundwater present at low altitudes resulted from evaporative concentration when the water table was shallow.

California↗
USGS1988

Distribution of selenium in soils of agricultural fields, western San Joaquin Valley, California

Soils from three agricultural fields in the Panoche Creek alluvial fan area in the western San Joaquin Valley, California, were analyzed for soluble, adsorbed, and total concentrations of selenium (Se) to assess the distribution and forms of Se in relation to the leaching of Se from soils. This assessment is needed to evaluate the importance of soil Se in affecting ground water concentrations. Soil samples were collected from three fields with drainage systems of different ages (6, 15, 1.5 yr) and different Se concentrations in drain water (58, 430, 3700 µg L −1 , respectively). Concentrations of soluble Se and salinity were highest in soils from the field drained for 1.5 yr and lowest in the field drained for 6 yr. Of the total concentration of soil Se from all three fields, the proportion of adsorbed and soluble Se ranged from 1 to 11% and <1 to 63%, respectively. Most of the soluble Se was present as selenate and most of the adsorbed Se was found to be selenite. Consistent with a model of evaporative concentration of Se and salinity in soils and shallow ground water in this area, most of the variance in soluble Se is explained by salinity (r 2 > 0.68) in saturation extracts of soils sampled from below the water table. In contrast, most soluble salts and Se apparently have been leached from the unsaturated soils in the fields drained for 6 and 15 yr. For the leached soils, dissolution and precipitation of evaporite minerals containing Se may no longer control concentrations of soluble Se.

California↗
USGS1988

Relation of salinity and selenium in shallow ground water to hydrologic and geochemical processes, western San Joaquin Valley, California

Salinity and selenium concentrations in shallow ground water of the western San Joaquin Valley, California, are related to the geomorphology and hydrology of the alluvial fans. The highest salinity and selenium concentrations in shallow ground water occur in alluvium deposited by ephemeral streams and at the margins of the major alluvial fans, where there were naturally saline, fine-grained soils. Low-to-moderate salinity and selenium concentrations in shallow ground water are associated with upper and middle areas of the major alluvial fans deposited by intermittent streams. Areas with the most naturally saline soils have been irrigated in the last 40 years. These are now the areas of highest salinity and selenium concentrations in the shallow ground water. Present-day (1986) ground-water salinity is significantly correlated with natural soil salinity in these areas. Isotopic data indicate that the highest salinity and selenium concentrations in ground water present at low altitudes resulted from evaporative concentration when the water table was shallow.

California↗
USGS1988

Geohydrologic aspects of water-quality problems of the San Joaquin Valley, California

Salinity and selenium concentrations in shallow ground water of the western San Joaquin Valley, California, are related to the geomorphology and hydrology of the alluvial fans. High salinity and selenium concentrations are associated with ephemeral-stream deposits. Low salinity and selenium concentrations are associated with intermittent-stream deposits, which represent the major alluvial fans of the area. The highest salinity and selenium concentrations at the margins of the alluvial fans are the result of evaporation and evapotranspiration of shallow ground water, as indicated by oxygen- and hydrogen-isotopic data. The extent and direction of movement of saline ground water to drain laterals in agricultural fields are influenced by the time since installation of the drainage system, drain lateral spacing, and the regional ground-water-flow system.

Conference Paper↗
USGS1987

Processes affecting the distribution of selenium in shallow ground water of agricultural areas, western San Joaquin Valley, California

A study was undertaken to evaluate the processes affecting the chemistry of shallow ground water associated with agricultural drainage systems in the western San Joaquin Valley, California. The study was prompted by a need for an understanding of selenium mobility in areas having high selenium concentrations in shallow ground water. Groundwater samples were collected along transects in three artificially drained fields where the age of the drainage system varied (15, 6, and 1.5 years). Selenium concentrations in the drainage water also varied (0F30, 58, and 3700 micrograms per liter, respectively). Isotopic enrichment and chemical composition of the ground-water samples indicate that saline- and selenium-enriched water has evolved as a result of evaporation of ground water. This evaporated, isotopically enriched water is being displaced by more recent, less saline irrigation water percolating through the root zone. This displace-ment seems to be a process whereby sodium chloride and sodium sulfate water is being replaced by more dilute calcium sulfate and calcium bicarbonate water.

California↗
USGS1987

Distribution of selenium in soils of agricultural fields, western San Joaquin Valley, California

Soils from three agricultural fields in the western San Joaquin Valley were analyzed for soluble, adsorbed, and total concentrations of selenium (Se) to assess the distribution and forms of Se, and the relation of the distribution and forms of Se to the leaching of Se from soils. Soil samples were collected in three fields with drainage systems of different ages (6, 15, 1.5 yr) and different Se concentrations in drain water (58, 430, 3700 micrograms/L respectively). Preliminary methods to determine total Se and estimate adsorbed Se were developed. Of the three fields, concentrations of soluble Se and salinity were highest in soils from the field drained for 1.5 yr and lowest in the field drained for 6 yr. The field drained for 1.5 yr also had the highest concentration of total Se in soil; a median of 1.2 microgram/gm. Of the total concentration of Se in soil from all three fields, the proportion of adsorbed Se and soluble Se ranged from 1 to 11% and < 1 to 63%, respectively. Most of the variance in soluble Se is explained by salinity ( r sq > 0.68) in saturation extracts of soils sampled from below the water table, reflecting evaporative concentration of Se and salinity. In contrast, most soluble salts and Se apparently have been leached from the unsaturated soils in the fields drained for 6 and 15 yr; therefore, the correlation was lower between Se and salinity in saturation extracts of those soils (r sq < 0.33). Among soils from all three fields, the ratio of Se to salinity in saturation extracts increased with increasing salinity. (Author 's abstract)

Open-File Report↗
USGS1986

Distribution and mobility of selenium and other trace elements in shallow ground water of the western San Joaquin Valley, California

Samples of shallow ground water that underlies much of the irrigated area in the western San Joaquin Valley of California were analyzed for various major ions and trace elements, including selenium. Concentrations of the major ions generally were similar for ground water collected in the two primary geologic zones--the alluvial fan and basin trough. Soils in the alluvial-fan zone are derived from Coast Range rocks, and soils in the basin-trough zone are from a mixture of Sierra Nevada and Coast Range sources. Most of the variance in concentrations of major ions, as determined by principal components analysis, was associated with ground-water salinity and the dominant ions--magnesium, sodium, sulfate, and chloride. Most of the variance in trace elements was associated with concentrations of boron, molybdenum, selenium, and vanadium, which are present as mobile oxyanions. The concentrations of oxyanions trace elements were significantly correlated (a=0.05) with groundwater salinity, but the correlations between selenium and salinity and molybdenum and salinity were significantly different (a=0.05) in the alluvial-fan geologic zone compared with the basin-trough geologic zone. In addition, selenium concentrations are significantly (a=0.05) higher in the ground water of the alluvial-fan zone than in the basin-trough zone. The evidence suggests that the main factors influencing selenium concentrations in the shallow ground water are the degree of ground-water salinity and the geologic source of the alluvial soil material.

California↗