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Occurrence and Sources of Pesticides to Urban Wastewater and the Environment

American Chemical Society (ACS) | March 26th, 2019

Summary

Municipal wastewater has not been extensively examined as a pathway by which pesticides contaminate surface water, particularly relative to the well-recognized pathways o

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Occurrence of hexavalent chromium in ground water in the western Mojave Desert, California

Applied Geochemistry (Elsevier) | July 1st, 2004

Summary

About 200 samples from selected public supply, domestic, and observation wells completed in alluvial aquifers underlying the western Mojave Desert were analyzed for total

About 200 samples from selected public supply, domestic, and observation wells completed in alluvial aquifers underlying the western Mojave Desert were analyzed for total dissolved Cr and Cr(VI). Because Cr(VI) is difficult to preserve, samples were analyzed by 3 methods. Chromium(VI) was determined in the field using both a direct colorimetric method and EPA method 218.6, and samples were speciated in the field for later analysis in the laboratory using a cation-exchange method developed for the study described in this paper. Comparison of the direct colorimetric method and EPA method 218.6 with the new cation-exchange method yielded r2 values of 0.9991 and 0.9992, respectively. Total dissolved Cr concentrations ranged from less than the 0.1 μg/l detection limit to 60 μg/l, and almost all the Cr present was Cr(VI). Near recharge areas along the mountain front pH values were near neutral, dissolved O2 concentrations were near saturation, and Cr(VI) concentrations were less than the 0.1 μg/l detection limit. Chromium(VI) concentrations and pH values increased downgradient as long as dissolved O2 was present. However, low Cr(VI) concentrations were associated with low dissolved O2concentrations near ground-water discharge areas along dry lakes. Chromium(VI) concentrations as high as 60 μg/l occurred in ground water from the Sheep Creek fan alluvial deposits weathered from mafic rock derived from the San Gabriel Mountains, and Cr(VI) concentrations as high as about 36 μg/l were present in ground water from alluvial deposits weathered from less mafic granitic, metamorphic, and volcanic rocks. Chromium(III) was the predominant form of Cr only in areas where dissolved O2 concentrations were less than 1 mg/l and was detected at a median concentration of 0.1 μg/l, owing to its low solubility in water of near-neutral pH. Depending on local hydrogeologic conditions and the distribution of dissolved O2, Cr(VI) concentrations may vary considerably with depth. Samples collected under pumping conditions from different depths within wells show that Cr(VI) concentrations can range from less than the 0.1 μg/l detection limit to 36 μg/l in a single well and that dissolved O2 concentrations likely control the concentration and redox speciation of Cr in ground water.

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Occurrence of natural and anthropogenic hexavalent chromium (Cr VI) in groundwater near a mapped plume, Hinkley, CA

U.S. Geological Survey (USGS) | March 22nd, 2018

Summary

This report describes (1) work done between January 2015 and May 2017 as part of the U.S. Geological Survey (USGS) hexavalent chromium, Cr(VI), background study and (2) t

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Occurrence of water and thermogenic gas from oil-bearing formations in groundwater near the Orcutt Oil Field, California, USA

Journal of Hydrology: Regional Studies (Elsevier) | April 11th, 2022

Summary

Study region: Santa Barbara County, California, USA. Study focus: To analyze a wide array of newly collected chemical, isotopic, dissolved gas, and age dating tracers

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Ocean Climate Indicators: A Monitoring Inventory and Plan for Tracking Climate Change in the North-central California Coast and Ocean Region

Gulf of the Farallones National Marine Sanctuary Advisory Council | August 14th, 2014

Summary

The impacts of climate change, defined as increasing atmospheric and oceanic carbon dioxide and associated increases in average global temperature and oceanic a

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Ocean, Harbor and Bay Water Quality Report 2019-2020

Orange County Health Care Agency (OCHCA) | April 30th, 2021

Summary

The 2019–2020 Ocean, Harbor and Bay Water Quality Report provides updated data on sewage spills and their impacts resulting in ocean water closures and provid

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Ocean, Harbor and Bay Water Quality Report 2023 – 2024

Orange County Health Care Agency (OCHCA) | May 30th, 2025

Summary

The 2023-2024 Ocean, Harbor and Bay Water Quality Report provides updated data on sewage spills, the spill impacts resulting in ocean water closures and an analysis of ba

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Off-Lake Sources of Airborne Dust in Owens Valley, California

National Academy of Sciences (NAS) | June 17th, 2025

Summary

Since 2017, the District has used additional information to attribute PM10 exceedances to specific sources within the Owens Valley Planning Area. This information include

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Optimizing sampling methods for monitoring pollutant trends in San Francisco Bay urban stormwater

San Francisco Estuary Institute (SFEI) | July 1st, 2016

Summary

The Small Tributaries Loading Strategy (STLS) focuses on urban stormwater loadings from small tributaries. To date, STLS monitoring has been geared towards dete

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Ordinary High Flows and the Stage–Discharge Relationship in the Arid West Region

U.S. Army Corps of Engineers (USACE) | July 14th, 2011

Summary

The Ordinary High Water Mark (OHWM) defines the lateral extent of non-wetland waters and is regulated as “Waters of the United States” under Sec. 404 of the Clean Wat

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Occurrence and Sources of Pesticides to Urban Wastewater and the Environment

Occurrence of hexavalent chromium in ground water in the western Mojave Desert, California

Occurrence of natural and anthropogenic hexavalent chromium (Cr VI) in groundwater near a mapped plume, Hinkley, CA

Occurrence of water and thermogenic gas from oil-bearing formations in groundwater near the Orcutt Oil Field, California, USA

Ocean Climate Indicators: A Monitoring Inventory and Plan for Tracking Climate Change in the North-central California Coast and Ocean Region

Ocean, Harbor and Bay Water Quality Report 2019-2020

Ocean, Harbor and Bay Water Quality Report 2023 – 2024

Off-Lake Sources of Airborne Dust in Owens Valley, California

Optimizing sampling methods for monitoring pollutant trends in San Francisco Bay urban stormwater

Ordinary High Flows and the Stage–Discharge Relationship in the Arid West Region

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