Chemical Characteristics, Water Sources and Pathways, and Age Distribution of Ground Water in the Contributing Recharge Area of a Public-Supply Well near Tampa, Florida, 2002-05

Katz, Brian G.; Crandall, Christy A.; Metz, P.A.; McBride, W. Scott; Berndt, Marian P.

doi:10.3133/sir20075139

Cited by 23 publications

(56 citation statements)

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“…That well and site had a moderate length screened interval, large screen depth below the water table, moderate pumping rate and large contributing area, low recharge rate, and low velocities through the aquifer (Table 1). Short‐circuit pathways, such as long irrigation well screens that crossed multiple geologic layers in the contributing area at York [ Clark et al , 2007] and karst conduits in the contributing area at Tampa [ Katz et al , 2007], also affected age distributions in the PSW at those sites by allowing relatively rapid movement of young water to those well screens. Simulations suggest that the York PSW would not produce any water <50 years old if those short‐circuit pathways were not present in the contributing area [ Clark et al , 2007].…”

Section: Resultsmentioning

confidence: 99%

“…This is particularly evident in the chemical breakthrough curve for Tampa. Chemical data and downhole video from that PSW indicated that the well screen intersected a karst conduit that allowed young water to quickly reach the PSW [ Katz et al , 2007]. The simulated concentrations for Tampa show rapid initial responses at the beginning and end of chemical input (Figure 6a), followed by more gradual responses in concentration as older water entered the well screen.…”

Section: Resultsmentioning

confidence: 99%

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Simulated response of water quality in public supply wells to land use change

McMahon

Burow

Kauffman

et al. 2008

Water Resources Research

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[1] Understanding how changes in land use affect water quality of public supply wells (PSW) is important because of the strong influence of land use on water quality, the rapid pace at which changes in land use are occurring in some parts of the world, and the large contribution of groundwater to the global water supply. In this study, groundwater flow models incorporating particle tracking and reaction were used to analyze the response of water quality in PSW to land use change in four communities: Modesto, California (Central Valley aquifer); York, Nebraska (High Plains aquifer); Woodbury, Connecticut (Glacial aquifer); and Tampa, Florida (Floridan aquifer). The water quality response to measured and hypothetical land use change was dependent on age distributions of water captured by the wells and on the temporal and spatial variability of land use in the area contributing recharge to the wells. Age distributions of water captured by the PSW spanned about 20 years at Woodbury and >1,000 years at Modesto and York, and the amount of water <50 years old captured by the PSW ranged from 30% at York to 100% at Woodbury. Short-circuit pathways in some PSW contributing areas, such as long irrigation well screens that crossed multiple geologic layers (York) and karst conduits (Tampa), affected age distributions by allowing relatively rapid movement of young water to those well screens. The spatial component of land use change was important because the complex distribution of particle travel times within the contributing areas strongly influenced contaminant arrival times and degradation reaction progress. Results from this study show that timescales for change in the quality of water from PSW could be on the order of years to centuries for land use changes that occur over days to decades, which could have implications for source water protection strategies that rely on land use change to achieve water quality objectives.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Simulated response of water quality in public supply wells to land use change

McMahon

Burow

Kauffman

et al. 2008

Water Resources Research

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“…Redox conditions are also important for understanding occurrences of elevated arsenic concentrations in the lower intermediate aquifer. Previous studies have attributed relatively high arsenic concentrations to the infiltration of surface water and subsequent oxidation of pyrite in these formations (Katz et al ; Katz et al ; Ayotte et al ). Although the present model predicted that surface water would have reached lower intermediate aquifer wells by the early 2000s (~28–31 m; Figure C), oxygen was predicted to have been consumed prior to this depth.…”

Section: Discussionmentioning

confidence: 97%

“…The highest groundwater arsenic concentrations historically occurred in the surficial aquifer beneath the Main Plant Area and the primary process water pond (P1) (Figure ), with concentrations predominantly greater than 0.01 mg/L (the EPA Maximum Contaminant Level, or MCL) at these locations. In deeper groundwater, arsenic concentrations have generally been within the expected natural background range (0.001–0.02 mg/L) (Katz et al , ; Ayotte et al ).…”

Section: Site Backgroundmentioning

confidence: 99%

“…Prior to the 1950s, the potentiometric surface in the Floridan aquifer was higher than in the overlying strata and an upward groundwater gradient was present. The water gradient has since reversed to downward because of extensive pumping for irrigation and drinking water supply at the regional scale (Katz et al ; Ayotte et al ). At the site, water levels in the Floridan aquifer have typically been reported to be greater than 15 m lower than levels reported in the surficial aquifer, indicating a steep downward hydraulic gradient across the semi‐confining intermediate aquifer.…”

Section: Site Backgroundmentioning

confidence: 99%

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Effectiveness of Monitored Natural Attenuation (MNA) as a Groundwater Remedy for Arsenic in Phosphatic Wastes

Bessinger¹,

Hennet²

2019

Groundwater Monitoring Rem

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A study was conducted to evaluate monitored natural attenuation (MNA) as a remedy for arsenic in groundwater at a former phosphate mining and manufacturing facility. The mineralogy, speciation, and lability of arsenic in phosphatic wastes present in soils were characterized using sequential extraction procedures, leaching experiments, batch adsorption tests, and microchemical speciation analysis. A PHREEQC‐based reactive transport model was also parameterized using these laboratory results, and it was used to evaluate the importance of identified attenuation mechanisms on arsenic concentrations along a vertical flow path from a shallow, alluvial aquifer to the underlying Floridan aquifer. Arsenic was found to occur in several chemical forms in phosphatic wastes, including unstable sulfide minerals, adsorbed surface complexes, and relatively insoluble phosphate and oxide minerals. Most arsenic was associated with stable minerals. The reactive transport model predicted that historical leaching of solid‐phase waste materials in soils would not have generated enough arsenic to explain the concentrations observed in downgradient groundwater; instead, the source of arsenic to groundwater was likely acidic and saline process water that infiltrated though unlined ponds and ditches during historical manufacturing operations. A key factor affecting the long‐term effectiveness of natural attenuation of arsenic in groundwater is the occurrence and stability of iron oxyhydroxides in aquifer sediments. According to laboratory and reactive transport model results, sufficient levels were found to be present at the site to effectively limit arsenic migration at concentrations exceeding drinking water standards in the future in the Floridan aquifer. This study presents the geochemical evaluations that are needed to satisfy EPA guidelines on determining whether or not MNA is an acceptable remedy for a site. It specifically details the characterization and modeling that were used to demonstrate effectiveness at a site where MNA was ultimately selected as the remedy for arsenic in groundwater.

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Nitrate Contamination in Springs

2020

Geophysical Monograph Series

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Chemical Characteristics, Water Sources and Pathways, and Age Distribution of Ground Water in the Contributing Recharge Area of a Public-Supply Well near Tampa, Florida, 2002-05

Cited by 23 publications

References 0 publications

Simulated response of water quality in public supply wells to land use change

Simulated response of water quality in public supply wells to land use change

Effectiveness of Monitored Natural Attenuation (MNA) as a Groundwater Remedy for Arsenic in Phosphatic Wastes

Nitrate Contamination in Springs

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