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Roger Fujii

Publications and source records attributed to Roger Fujii.

28 records · Page 2Linked to original sources
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

Selenium speciation methods and application to soil saturation extracts from San Joaquin Valley, California

Methods to determine soluble concentrations of selenite, selenate, and organic Se were evaluated on saturation extracts of soil samples collected from three sites on the Panoche Creek alluvial fan in the western San Joaquin Valley, California. The methods were used in combination with hydride-generation atomic-absorption spectrometry for detection of Se, and included a selective chemical-digestion method and three chromatographic methods using XAD-8 resin, Sep-Pak C 18 cartridge, and a combination of XAD-8 resin and activated charcoal. The chromatography methods isolate dissolved organic matter that can inhibit Se detection by hydride-generation atomic-absorption spectrometry. Isolation of hydrophobic organic matter with XAD-8 did not affect concentrations of selenite and selenate, and the isolated organic matter represents a minimal estimation of organic Se. Ninety-eight percent of the Se in the extracts was selenate and about 100% of the isolated organic Se was associated with the humic acid fraction of dissolved organic matter. The depth distribution of Se species in the soil saturation extracts support a hypothesis that the distribution of soluble Se and salinity in these soils is the result of evaporation from a shallow water table and leaching by irrigation water low in Se and salinity.

California↗
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↗
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

Water-quality and sediment-chemistry data of drain water and evaporation ponds from Tulare Lake Drainage District, Kings County, California March 1985 to March 1986

Trace element and major ion concentrations were measured in water samples collected monthly between March 1985 and March 1986 at the MD-1 pumping station at the Tulare Lake Drainage District evaporation ponds, Kings County, California. Samples were analyzed for selected pesticides several times during the year. Salinity, as measured by specific conductance, ranged from 11,500 to 37,600 microsiemens/centimeter; total recoverable boron ranged from 4,000 to 16,000 micrg/L; and total recoverable molybdenum ranged from 630 to 2,600 microg/L. Median concentrations of total arsenic and total selenium were 97 and 2 microg/L. Atrazine, prometone, propazine, and simazine were the only pesticides detected in water samples collected at the MD-1 pumping station. Major ions, trace elements, and selected pesticides also were analyzed in water and bottom-sediment samples from five of the southern evaporation ponds at Tulare Lake Drainage District. Water enters the ponds from the MD-1 pumping station at pond 1 and flows through the system terminating at pond 10. The water samples increased in specific conductance (21,700 to 90,200 microsiemens/centimeter) and concentrations of total arsenic (110 to 420 microg/L), total recoverable boron (12,000 to 80,000 microg/L) and total recoverable molybdenum (1,200 to 5,500 microg/L) going from pond 1 to pond 10, respectively. Pesticides were not detected in water from any of the ponds sampled. Median concentrations of total arsenic and total selenium in the bottom sediments were 4.0 and 0.9 microg/g, respectively. The only pesticides detected in bottom sediment samples from the evaporation ponds were DDD and DDE, with maximum concentration of 0.8 microg/kilogram. (Author 's abstract)

Open-File Report↗
USGS1988

Comparison of methods to determine selenium species in saturation extracts of soils from the western San Joaquin Valley, California

Methods to determine soluble concentrations of selenite, selenate, and organic selenium were compared on saturation extracts of soil samples collected from three sites on the Panache Creek alluvial fan in the western San Joaquin Valley, California. The methods were used in combination with hydridegeneration atomic-absorption spectrometry for detection of selenium and included a selective chemical digestion method and three chromatography methods using XAD-8 resin, Sep-Pac C 18 cartridge, and a combination of XAD-8 resin and activated charcoal. Undigested organic matter in some of the extracts inhibited selenium detection when using the digestion and Sep-Pac C18 methods, but the interference was removed by using the XAD-8 method. Combining XAD-8 resin and activated charcoal was an unacceptable method, because the activated charcoal removed selenite and selenate. Ninety-eight percent of the selenium in the extracts was selenate and about 100 percent of the isolated organic selenium was associated with the humic acid fraction of dissolved-organic matter.

California↗
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↗