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פותח על ידי קלירמאש פתרונות בע"מ -
Elevated naturally occurring arsenic in a semiarid oxidizing system, Southern High Plains aquifer, Texas, USA
Year:
2009
Source of publication :
Applied Geochemistry
Authors :
קורצמן, דניאל
;
.
Volume :
24
Co-Authors:
Scanlon, B.R., Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States
Nicot, J.P., Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States
Reedy, R.C., Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States
Kurtzman, D., Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States
Mukherjee, A., Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States
Nordstrom, D.K., Water Resources Discipline, US Geological Survey, Boulder, CO, United States
Facilitators :
From page:
2061
To page:
2071
(
Total pages:
11
)
Abstract:
High groundwater As concentrations in oxidizing systems are generally associated with As adsorption onto hydrous metal (Al, Fe or Mn) oxides and mobilization with increased pH. The objective of this study was to evaluate the distribution, sources and mobilization mechanisms of As in the Southern High Plains (SHP) aquifer, Texas, relative to those in other semiarid, oxidizing systems. Elevated groundwater As levels are widespread in the southern part of the SHP (SHP-S) aquifer, with 47% of wells exceeding the current EPA maximum contaminant level (MCL) of 10 μg/L (range 0.3-164 μg/L), whereas As levels are much lower in the north (SHP-N: 9% ≥ As MCL of 10 μg/L; range 0.2-43 μg/L). The sharp contrast in As levels between the north and south coincides with a change in total dissolved solids (TDS) from 395 mg/L (median north) to 885 mg/L (median south). Arsenic is present as arsenate (As V) in this oxidizing system and is correlated with groundwater TDS (Spearman's ρ = 0.57). The most likely current source of As is sorbed As onto hydrous metal oxides based on correlations between As and other oxyanion-forming elements (V, ρ = 0.88; Se, ρ = 0.54; B, ρ = 0.51 and Mo, ρ = 0.46). This source is similar to that in other oxidizing systems and constitutes a secondary source; the most likely primary source being volcanic ashes in the SHP aquifer or original source rocks in the Rockies, based on co-occurrence of As and F (ρ = 0.56), oxyanion-forming elements and SiO2 (ρ = 0.41), which are found in volcanic ashes. High groundwater As concentrations in some semiarid oxidizing systems are related to high evaporation. Although correlation of As with TDS in the SHP aquifer may suggest evaporative concentration, unenriched stable isotopes (δ2H: -65 to -27; δ18O: -9.1 to -4.2) in the SHP aquifer do not support evaporation. High TDS in the SHP aquifer is most likely related to upward movement of saline water from the underlying Triassic Dockum aquifer. Mobilization of As in other semiarid oxidizing systems is caused by increased pH; however, pH in the SHP aquifer is near neutral (10-90 percentiles, 7.0-7.6). Although many processes, such as competitive desorption with SiO2, VO4, or PO4, could be responsible for local mobilization of As in the SHP aquifer, the most plausible explanation for the regional As distribution and correlation with TDS is the counterion effect caused by a change from Ca- to Na-rich, water as shown by the high correlation between As and Na/(Ca)0.5 ratios (ρ = 0.57). This change in chemistry is related to mixing with saline water that moves upward from the underlying Dockum aquifer. This counterion effect may mobilize other anions and oxyanion-forming elements that are correlated with As (F, V, Se, B, Mo and SiO2). Competition among the oxyanions for sorption sites may enhance As mobilization. The SHP case study has similar As sources to those of other semiarid, oxidizing systems (original volcanic ash source followed by sorption onto hydrous metal oxides) but contrasts with these systems by showing lack of evaporative concentration and pH mobilization of As but counterion mobilization of As instead in the SHP-S aquifer. © 2009 Elsevier Ltd.
Note:
Related Files :
Adsorption
aquifers
hydrogeology
pH
saline water
Silicon
Sorption sites
Source rocks
Upward movement
עוד תגיות
תוכן קשור
More details
DOI :
10.1016/j.apgeochem.2009.08.004
Article number:
Affiliations:
Database:
סקופוס
Publication Type:
מאמר
;
.
Language:
אנגלית
Editors' remarks:
ID:
19240
Last updated date:
02/03/2022 17:27
Creation date:
16/04/2018 23:27
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Scientific Publication
Elevated naturally occurring arsenic in a semiarid oxidizing system, Southern High Plains aquifer, Texas, USA
24
Scanlon, B.R., Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States
Nicot, J.P., Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States
Reedy, R.C., Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States
Kurtzman, D., Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States
Mukherjee, A., Bureau of Economic Geology, Jackson School of Geosciences, University of Texas at Austin, Austin, TX 78758, United States
Nordstrom, D.K., Water Resources Discipline, US Geological Survey, Boulder, CO, United States
Elevated naturally occurring arsenic in a semiarid oxidizing system, Southern High Plains aquifer, Texas, USA
High groundwater As concentrations in oxidizing systems are generally associated with As adsorption onto hydrous metal (Al, Fe or Mn) oxides and mobilization with increased pH. The objective of this study was to evaluate the distribution, sources and mobilization mechanisms of As in the Southern High Plains (SHP) aquifer, Texas, relative to those in other semiarid, oxidizing systems. Elevated groundwater As levels are widespread in the southern part of the SHP (SHP-S) aquifer, with 47% of wells exceeding the current EPA maximum contaminant level (MCL) of 10 μg/L (range 0.3-164 μg/L), whereas As levels are much lower in the north (SHP-N: 9% ≥ As MCL of 10 μg/L; range 0.2-43 μg/L). The sharp contrast in As levels between the north and south coincides with a change in total dissolved solids (TDS) from 395 mg/L (median north) to 885 mg/L (median south). Arsenic is present as arsenate (As V) in this oxidizing system and is correlated with groundwater TDS (Spearman's ρ = 0.57). The most likely current source of As is sorbed As onto hydrous metal oxides based on correlations between As and other oxyanion-forming elements (V, ρ = 0.88; Se, ρ = 0.54; B, ρ = 0.51 and Mo, ρ = 0.46). This source is similar to that in other oxidizing systems and constitutes a secondary source; the most likely primary source being volcanic ashes in the SHP aquifer or original source rocks in the Rockies, based on co-occurrence of As and F (ρ = 0.56), oxyanion-forming elements and SiO2 (ρ = 0.41), which are found in volcanic ashes. High groundwater As concentrations in some semiarid oxidizing systems are related to high evaporation. Although correlation of As with TDS in the SHP aquifer may suggest evaporative concentration, unenriched stable isotopes (δ2H: -65 to -27; δ18O: -9.1 to -4.2) in the SHP aquifer do not support evaporation. High TDS in the SHP aquifer is most likely related to upward movement of saline water from the underlying Triassic Dockum aquifer. Mobilization of As in other semiarid oxidizing systems is caused by increased pH; however, pH in the SHP aquifer is near neutral (10-90 percentiles, 7.0-7.6). Although many processes, such as competitive desorption with SiO2, VO4, or PO4, could be responsible for local mobilization of As in the SHP aquifer, the most plausible explanation for the regional As distribution and correlation with TDS is the counterion effect caused by a change from Ca- to Na-rich, water as shown by the high correlation between As and Na/(Ca)0.5 ratios (ρ = 0.57). This change in chemistry is related to mixing with saline water that moves upward from the underlying Dockum aquifer. This counterion effect may mobilize other anions and oxyanion-forming elements that are correlated with As (F, V, Se, B, Mo and SiO2). Competition among the oxyanions for sorption sites may enhance As mobilization. The SHP case study has similar As sources to those of other semiarid, oxidizing systems (original volcanic ash source followed by sorption onto hydrous metal oxides) but contrasts with these systems by showing lack of evaporative concentration and pH mobilization of As but counterion mobilization of As instead in the SHP-S aquifer. © 2009 Elsevier Ltd.
Scientific Publication
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