Role of soil-derived dissolved substances in arsenic transport and transformation in laboratory experiments

• Published in: The Science of the total environment 2008-11, Vol.406 (1), p.180-189
• Main Authors: Chen, Zhangrong, Cai, Yong, Liu, Guangliang, Solo-Gabriele, Helena, Snyder, George H., Cisar, John L.
• Format: Article
• Language: English
• Subjects: Adsorption; Applied sciences; Arsenates; Arsenates - analysis; Arsenates - chemistry; Arsenic; Arsenic - analysis; Arsenic - chemistry; Arsenicals - analysis; Arsenicals - chemistry; Biological and physicochemical properties of pollutants. Interaction in the soil; Carbon - analysis; Carbon - chemistry; Chromatography; Colloids; Colloids - analysis; Colloids - chemistry; Column experiment; Dissolution; Dissolved organic matter; Earth sciences; Earth, ocean, space; Effluents; Engineering and environment geology. Geothermics; Environmental Monitoring - methods; Exact sciences and technology; Hydrogen-Ion Concentration; Influents; Laboratories; Media; Movement; Numerical control; Pesticides; Pollution; Pollution, environment geology; Polymethyl methacrylates; Porosity; porous media; Risk assessment; Sand; Soil; Soil (material); Soil and sediments pollution; soil organic matter; soil pH; soil pollution; soil properties; soil transport processes; Soil-derived dissolved substances; Surface chemistry; Transformation; Transformations; Transport
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2008.07.017

Dissolved substances derived from soil may interact with both soil surfaces and with arsenic and subsequently influence arsenic mobility and species transformation. The purpose of this study was to investigate arsenic transport and transformation in porous media with a specific focus on the impact of soil-derived dissolved substances, mainly consisting of inorganic colloids and dissolved organic matter (DOM), on these processes. Arsenic transport and transformation through columns, which were packed with uncoated sand (UC) or naturally coated sand (NC) and fed with arsenate (As V) or monomethylarsonic acid (MMA) spiked influents, were investigated in the presence or absence of soil-derived dissolved substances. The presence of soil-derived inorganic colloids and/or DOM clearly enhanced As transport through the column, with the fraction of As leached out of column (referring to the total amount added) being increased from 23 to 46% (UC) and 21 to 50% (NC) in As V experiments while 46 to 64% (UC) and 28 to 63% (NC) in MMA experiments. The association of arsenic with DOM and the competitive adsorption between arsenic and DOM could account for, at least partly, the enhanced As movement. Distinct species transformation of As during transport through soil columns was observed. When As V was the initial species spiked in the influent solutions, only arsenite (As III) was detected in the effluents for UC columns; while both As III (dominant) and As V were present for NC columns, with As III being the dominant species. When MMA was initially spiked in the influent solutions, all method detectable As species, As III, As V, MMA, and dimethylarsenic acid (DMA) were present in the effluents for both soil columns. These results indicate that risk assessment associated with As contamination, particularly due to previous organoarsenical pesticide applications, should take into account the role of soil-derived dissolved substances in promoting As transport and As species transformation.