A5070463936- Groundwater and Isotope Geochemistry
- Groundwater flow and contamination studies
- Water Quality and Resources Studies
- Water Treatment and Disinfection
- Geological and Geochemical Analysis
- High-pressure geophysics and materials
- Hydrology and Watershed Management Studies
- Geochemistry and Geologic Mapping
- Chemical Analysis and Environmental Impact
- Coastal wetland ecosystem dynamics
- Marine and coastal ecosystems
- Geological Studies and Exploration
- Radioactive contamination and transfer
- Arsenic contamination and mitigation
- Atmospheric and Environmental Gas Dynamics
- Radioactivity and Radon Measurements
- Peatlands and Wetlands Ecology
- earthquake and tectonic studies
- Radioactive element chemistry and processing
- Drilling and Well Engineering
- Constructed Wetlands for Wastewater Treatment
- Hydrocarbon exploration and reservoir analysis
- Reservoir Engineering and Simulation Methods
- Mineralogy and Gemology Studies
- Water Quality Monitoring and Analysis
United States Geological Survey
2010-2024
California Water Science Center
2009-2024
Entertainment Industries Council
2017-2019
United States Department of the Interior
2017
San Francisco Estuary Institute
2008
San Joaquin Delta College
2008
Watershed
2008
University of California, Davis
1993-2007
Stichting Afasie Nederland
2007
University of California System
1997-1999
Specific UV absorbance (SUVA) is defined as the of a water sample at given wavelength normalized for dissolved organic carbon (DOC) concentration. Our data indicate that SUVA, determined 254 nm, strongly correlated with percent aromaticity by 13C NMR 13 matter isolates obtained from variety aquatic environments. therefore, shown to be useful parameter estimating aromatic content in systems. Experiments involving reactivity DOC chlorine and tetra- methylammonium hydroxide (TMAH), however,...
Pharmaceutical compounds were detected at low concentrations in 2.3% of 1231 samples groundwater (median depth to top screened interval wells = 61 m) used for public drinking-water supply California. Samples collected statewide the California State Water Resources Control Board's Groundwater Ambient Monitoring and Assessment (GAMA) Program. Of 14 pharmaceutical analyzed, 7 greater than or equal method detection limits: acetaminophen (used as an analgesic, frequency 0.32%, maximum...
Groundwater is an important source of drinking water supplies in the conterminous United State (CONUS), and presence high nitrate concentrations may limit usability groundwater some areas because potential negative health effects. Prediction locations needed to focus mitigation relief efforts. A three-dimensional extreme gradient boosting (XGB) machine learning model was developed predict distribution nitrate. Nitrate predicted at a 1 km resolution for two zones, each variable depth, one...
Uranium (U) concentrations in groundwater several parts of the eastern San Joaquin Valley, California, have exceeded federal and state drinking water standards during last 20 years. The Valley is located within Central California one most productive agricultural areas world. Increased irrigation pumping associated with urban development 100 years changed chemistry magnitude recharge, increased rate downward movement. Strong correlations between U bicarbonate suggest that leached from shallow...
Hexavalent chromium, Cr(VI), in 918 wells sampled throughout California between 2004 and 2012 by the Groundwater Ambient Monitoring Assessment-Priority Basin Project (GAMA-PBP) ranged from less than study reporting limit of 1 microgram per liter (μg/L) to 32 μg/L. Statewide, Cr(VI) was reported 31 percent equaled or exceeded recently established (2014) Maximum Contaminant Level (MCL) for 10 μg/L 4 wells. data collected regulatory purposes overestimated occurrence compared...
Per- and polyfluoroalkyl substances (PFAS), known colloquially as "forever chemicals," have been associated with adverse human health effects contaminated drinking water supplies across the United States owing to their long-term widespread use. People in may unknowingly be that contains PFAS because of a lack systematic analysis, particularly domestic supplies. We present an extreme gradient-boosting model for predicting occurrence groundwater at depths supply conterminous States. Our...
Experimental data in the range of 1 bar to 13 kbar enable us map liquidus equilibria relevant Proterozoic (massif) anorthosites and related mafic rocks. Massif are widely believed have formed by accumulation plagioclase into high-Al basaltic liquids. Mantle-derived liquids, fractionating at pressures sufficiently high (10–13 kbar) crystallize highly aluminous orthopyroxene megacrysts typically observed anorthosite massifs, reach saturation low normative silica contents. Peritectic-like (e.g....
The stability of levees in the Sacramento-San Joaquin Delta is threatened by continued subsidence peat islands. Up to 6 meters land-surface elevation has been lost 150 years since marshes were leveed and drained, primarily from oxidation soils. Flooding subsided islands halts creating anoxic soils, but net accumulation new material restored wetlands required recover elevations. We investigated reversal potential two 3 hectare, permanently flooded, impounded re-established on a deeply field...
The proportion of an aquifer with constituent concentrations above a specified threshold (high concentrations) is taken as nondimensional measure regional scale water quality. If computed on the basis area, it can be referred to proportion. A spatially unbiased estimate and confidence interval for that are obtained through use equal area grids binomial distribution. Traditionally, using either standard or exact interval. Research from statistics literature has shown should not used overly...
Abstract Drought‐induced pumpage has precipitated dramatic groundwater‐level declines in California's Central Valley over the past 30 yr, but impacts of aquifer overdraft on water quality are poorly understood. This study coupled 160,000 measurements nitrate from ∼6,000 public‐supply wells with a yr reconstruction groundwater levels throughout to evaluate dynamic relations between exploitation and resource quality. We find that long‐term rates decline water‐quality degradation critically...
Data from 11 000 public supply wells in 87 study areas were used to assess the quality of nearly all groundwater for California. Two metrics developed quantifying quality: area with high concentrations (km2 or proportion) and equivalent-population relying upon (number people proportion). Concentrations are considered if they above a human-health benchmark. When expressed as proportions, area-weighted population-weighted detection frequencies. On statewide-scale, about 20% has one more...
Major element, trace isotope, and petrographic studies of the basal volcanics in Kangerdlugssuaq Fjord region East Greenland margin provide constraints on generation subsequent differentiation contamination histories magmas during early stage continental rifting creating North Atlantic ocean basin. Most primitive lavas succession are shown to have accumulated olivine. Corrections for crystal accumulation yield estimates erupted liquids with MgO contents between 9 13 wt %. The occurrence...
We use data from 1626 groundwater samples collected in California, primarily public drinking water supply wells, to investigate the distribution of perchlorate deep under natural conditions. The wells were sampled for California Groundwater Ambient Monitoring and Assessment Priority Basin Project. develop a logistic regression model predicting probabilities detecting at concentrations greater than multiple threshold as function climate (represented by an aridity index) potential...
Total dissolved solids (TDS) concentrations in groundwater tapped for beneficial uses (drinking water, irrigation, freshwater industrial) have increased on average by about 100 mg/L over the last years San Joaquin Valley, California (SJV). During this period land use SJV changed from natural vegetation and dryland agriculture to dominantly irrigated with growing urban areas. Century-scale salinity trends were evaluated comparing TDS major ion compositions of wells sampled 1910 (Historic)...
The presence of contaminants in a source water can constrain its suitability for drinking. quality groundwater used public supply was assessed 25 principal aquifers (PAs) that account 84% pumped the U.S. (89.6 million people on proportional basis). Each PA sampled across lateral extent using an equal-area grid, typically with 60 wells per PA. Samples were analyzed 502 constituents, which 374 had either regulatory or nonregulatory human health benchmark (HHB). Nationally, elevated...
This systematic assessment of occurrence for 85 volatile organic compounds (VOCs) in raw (untreated) groundwater used public supply across the United States (U.S.), which includes 43 not previously monitored by national studies, relates VOC to explanatory factors and assesses detections a human-health context. Samples were collected 2013 through 2019 from 1537 public-supply wells aquifers representing 78% volume pumped drinking-water supply. Laboratory detection limits VOCs generally less...
An analytical method has been developed for the determination of dissolved organic carbon concentration in water samples. This includes results tests used to validate and quality-control practices analysis. Prior analysis, samples are filtered remove suspended particulate matter. A Shimadzu TOC-5000A Total Organic Carbon Analyzer nonpurgeable mode is analyze by high temperature catalytic oxidation. The analysis usually completed within 48 hours sample collection. laboratory reporting level...