HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in ISI Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via ISI Web of Science (1) Citing Articles via Google Scholar Google Scholar Articles by Gao, S. Articles by Tanji, K. K. Search for Related Content PubMed Articles by Gao, S. Articles by Tanji, K. K. GeoRef GeoRef Citation Agricola Articles by Gao, S. Articles by Tanji, K. K. Related Collections Ground Water Quality Heavy Metals Soil Chemistry

DIVISION S-2—SOIL CHEMISTRY

Evaluation of Adsorbed Arsenic and Potential Contribution to Shallow Groundwater in Tulare Lake Bed Area, Tulare Basin, California

^a Dep. of Land, Air, and Water Resources, Univ. of California, Davis, CA 95616
^b U.S. Geological Survey, Sacramento, CA 95819
^c U.S. Geological Survey, Montpelier, VT 05602

^* Corresponding author (sugao{at}ucdavis.edu).

Elevated As concentrations in shallow groundwater in parts of the Tulare Basin, California, are a concern because of potential migration into deeper aquifers that could serve as a source of future drinking water. The objectives of this study were to evaluate adsorbed As and the potential contribution to groundwater using (i) isotopic dilution, (ii) successive extraction with an electrolyte solution resembling the pore-water chemical composition, and (iii) PO₄ exchange for As. Sediment samples collected from 2 to 4 m below land surface in the Tulare Lake bed area contained a total As concentration of 24 mg As kg^–1. Pore water extracted under hydraulic pressure contained a total As concentration of 590 µg As L^–1, which predominantly contained As as arsenate [As(V), 97%], a minor amount of arsenite [As(III), 3%], and non-detectable organic As. The isotopic dilution method [⁷³As(V)] estimated that the concentration of adsorbed As(V) on the sediment was 5.7 mg As kg^–1 at pH 8.5 and 6.7 mg As kg^–1 at pH 7.5, respectively. Fourteen successive 24-h extractions with the artificial pore water released up to 57 to 61% of the adsorbed As(V) that was determined by isotopic dilution, indicating that only a portion of the adsorbed As could be released to groundwater. The phosphate-exchangeable As (0.1 M PO₄, pH 8.5 or 7.5) was 63% of the isotopically exchangeable As(V). Thus, extraction of As by 0.1 M PO₄ at ambient pHs is recommended as a method to determine the potential amount of As(V) on sediments that could be released to the solution phase. The overall results indicated that adsorbed As could be a significant source of As to groundwater. However, other factors that affect As transport such as the leaching rate need to be considered.

Abbreviations: AAS, atomic absorption spectrometry • DD, distilled deionized • MCL, maximum contaminant level • RCF, relative centrifugal force