Ground-water quality of coastal aquifer systems in the West Coast Basin, Los Angeles County, California, 1999-2002

Land, Michael; Reichard, Eric G.; Crawford, Steven M.; Everett, Rhett R.; Newhouse, M.W.; Williams, Colin F.

doi:10.3133/sir20045067

Cited by 23 publications

(27 citation statements)

References 8 publications

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“…Most samples for this effort were collected as part of a larger U.S. Geological Survey (USGS) project on the groundwater quality and geochemical character underlying Los Angeles County and thus more complete sampling protocols and analytical methods are described in detail therein [4][5][6]. Briefly, each well was sufficiently purged and then sampled using "clean" procedures to avoid contamination as per standard USGS water quality sampling protocols.…”

Section: Methodsmentioning

confidence: 99%

“…The hydrogeology of the Dominguez Gap region has been well studied [26,27,32] and is summarized in a shore-perpendicular cross-section ( Figure 2). Injection of fresh water in the West Coast Basin and Dominguez Gap Barrier Projects is a significant source of recharge to the West Coast Groundwater Basin [6]. Ponti et al [30] developed a sequence stratigraphic model of the Dominguez Gap area that further refined these water-bearing depositional systems relative to sediment supply, sea level, and accommodation space.…”

Section: Geographic Settingmentioning

confidence: 99%

“…Each water-mass end member is geochemically distinct and has been identified with a suite of isotopes and geochemical parameters [6]. Groundwater samples for this study were collected from the Dominguez Gap region of the southwest Los Angeles Basin, located along the coastal plain of Los Angeles County adjacent to San Pedro Bay (Figure 1).…”

Section: Geographic Settingmentioning

confidence: 99%

“…Table 2 lists summary parameters and descriptions of well waters. Water levels of many of these near-shore wells increased in response to sustained freshwater injection, yet a concomitant decrease in Cl [6,42]. Non-native water typically exhibits a dominant Ca/Na-sulfate composition, while wells intruded by seawater or mixed with oil-field brines have a Na-Cl composition [6].…”

Section: Major Ion Compositionmentioning

confidence: 99%

“…This inefficiency in halting the seawater intrusion is due in part to an incomplete characterization of the stratigraphic architecture that partially controls the groundwater flow in this region. In an effort to better understand the geochemical character of this regional groundwater and to better predict future groundwater quality change, a study incorporating stable isotopes was initiated [4][5][6] and complemented with select U/Th radionuclide work.…”

Section: Introductionmentioning

confidence: 99%

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A Combined Radio- and Stable-Isotopic Study of a California Coastal Aquifer System

Swarzenski

Baskaran

Rosenbauer

et al. 2013

Water

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Stable and radioactive tracers were utilized in concert to characterize geochemical processes in a complex coastal groundwater system and to provide constraints on the kinetics of rock/water interactions. Groundwater samples from wells within the Dominguez Gap region of Los Angeles County, California were analyzed for a suite of major cations (Na Rn and 223,224,226,228 Ra). In the study area, groundwater may consist of a complex mixture of native groundwater, intruded seawater, non-native injected water, and oil-field brine water. In some wells, Cl in host matrices, strong isotopic fractionation in these groundwater samples can be used to obtain information of adsorption/desorption kinetics. Calculated Ra residence times are short, and the associated desorption rate constant is about three orders of magnitude slower than that of the adsorption rate constant. Combined stable-and radio-isotopic results provide unique insights into aquifer characteristics, such as geochemical cycling, rock/water interactions, and subsurface transport and mixing.

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Section: Methodsmentioning

confidence: 99%

Section: Geographic Settingmentioning

confidence: 99%

Section: Geographic Settingmentioning

confidence: 99%

Section: Major Ion Compositionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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A Combined Radio- and Stable-Isotopic Study of a California Coastal Aquifer System

Swarzenski

Baskaran

Rosenbauer

et al. 2013

Water

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Replenishing an unconfined coastal aquifer to control seawater intrusion: Injection or infiltration?

Shi

Xin

et al. 2017

Water Resources Research

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In this study, we compare the performances of well injection and pond infiltration in controlling seawater intrusion in an unconfined coastal aquifer through two scenario groups: (1) a single injection well versus an elliptic infiltration pond and (2) an injection-extraction well pair system versus an elliptic infiltration pond-extraction well system. Comparison is based on quantitative indicators that include the interface toe location, saltwater volume, and maximum net extraction rate (for scenario 2). We introduce a method to determine the maximum net extraction rate for cases where the locations of stagnation points cannot be easily derived. Analytical analysis shows that the performances of injection and infiltration are the same, provided that the pond shape is circular. The examination of scenario group 1 suggests that the shape of the infiltration pond has a minor effect on the interface toe location as well as the reduction in the saltwater volume, given the same total recharge rate. The investigation of scenario group 2 indicates, by contrast, that the maximum net extraction rate increases significantly with the increasing ratio of b to a, where a and b are semiaxes of the ellipse parallel and perpendicular to the coastline, respectively. Specifically, for a typical aquifer assumed, an increase of 40% is obtained for the maximum net extraction when b/a increases from 1/200 to 200. Despite that the study is based on a simplified model, the results provide initial guidance for practitioners when planning to use an aquifer recharge strategy to restore a salinized unconfined coastal aquifer.

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Origin of Methane and Sources of High Concentrations in Los Angeles Groundwater

Kulongoski

McMahon²,

Land

et al. 2018

JGR Biogeosciences

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In 2014, samples from 37 monitoring wells at 17 locations, within or near oil fields, and one site >5 km from oil fields, in the Los Angeles Basin, California, were analyzed for dissolved hydrocarbon gas isotopes and abundances. The wells sample a variety of depths of an aquifer system composed of unconsolidated and semiconsolidated sediments under various conditions of confinement. Concentrations of methane in groundwater samples ranged from 0.002 to 150 mg/L—some of the highest concentrations reported in a densely populated urban area. The δ13C and δ2H of the methane ranged from −80.8 to −45.5 per mil (‰) and −249.8 to −134.9‰, respectively, and, along with oxidation‐reduction processes, helped to identify the origin of methane as microbial methanogenesis and CO2 reduction as its main formation pathway. The distribution of methane concentrations and isotopes is consistent with the high concentrations of methane in Los Angeles Basin groundwater originating from relatively shallow microbial production in anoxic or suboxic conditions. Source of the methane is the aquifer sediments rather than the upward migration or leakage of thermogenic methane associated with oil fields in the basin.

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Ground-water quality of coastal aquifer systems in the West Coast Basin, Los Angeles County, California, 1999-2002

Cited by 23 publications

References 8 publications

A Combined Radio- and Stable-Isotopic Study of a California Coastal Aquifer System

A Combined Radio- and Stable-Isotopic Study of a California Coastal Aquifer System

Replenishing an unconfined coastal aquifer to control seawater intrusion: Injection or infiltration?

Origin of Methane and Sources of High Concentrations in Los Angeles Groundwater

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