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Arsenic Sorption in Phosphate‐Amended Soils during Flooding and Subsequent Aeration
Author(s) -
Reynolds J. G.,
Naylor D. V.,
Fendorf S. E.
Publication year - 1999
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1999.6351149x
Subject(s) - sorption , aeration , soil water , chemistry , environmental chemistry , anoxic waters , phosphate , arsenic , adsorption , soil science , environmental science , organic chemistry
Phosphate enhances the mobility of As in well‐aerated soils by competing for adsorption sites. Phosphate and As may also coexist in large concentrations in hydric soils, and the influence of P on As in anaerobic systems is largely unknown. To determine the effects of P on As dynamics during a soil flooding and aeration cycle, samples of two soils were amended with Na 2 HAsO 4 and Na 2 HPO 4 and incubated under a N 2 atmosphere for 41 d, and then reaerated for 7 d. Subsamples were collected intermittently and dissolved As, Fe, Mn, Ca, S, P, and H 3 AsO 3 concentrations were determined. Arsenic speciation in the soil solids was determined after 14 and 41 d of flooding and then after 13 h of aeration by X‐ray absorption near edge structure (XANES) spectroscopy. Arsenic sorption was small under anaerobic conditions, and H 2 PO − 4 additions enhanced As(V) reduction rate in both soils and slightly suppressed As sorption in one soil. Arsenopyrite (FeAsS) was identified in the soil solids. Rapid and simultaneous As sorption and Fe precipitation occurred during the first 0.25 d of aeration, suggesting that As was retained on freshly precipitated Fe (hydr)oxides. Manganese precipitation and concomitant As sorption occurred after 1 d of aeration. Arsenopyrite was largely destroyed upon aeration but As(III) persisted. Thus, As is partitioned into the solid phase under both aerobic and anaerobic conditions, although more appreciably under the aerobic conditions of this study, and P has little influence on dissolved As during soil flooding–aeration cycles.