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Modelling the fate of chromated copper arsenate in a sandy soil

journal contribution
posted on 2004-07-01, 00:00 authored by X Mao, D.Andrew Barry, L Li, Francesco Stagnitti, G Allinson, N Turoczy
A pulse of chromated copper arsenate (CCA, a timber preservative) was applied in irrigation water to an undisturbed field soil in a laboratory column. Concentrations of various elements in the leachate from the column were measured during the experiment. Also, the remnants within the soil were measured at the end of the experiment. The geochemical modelling package, PHREEQC-2, was used to simulate the experimental data. Processes included in the CCA transport modelling were advection, dispersion, non-specific adsorption (cation exchange) and specific adsorption by clay minerals and organic matter, as well as other possible chemical reactions such as precipitation/dissolution. The modelling effort highlighted the possible complexities in CCA transport and reaction experiments. For example, the uneven dosing of CCA as well as incomplete knowledge of the soil properties resulted in simulations that gave only partial, although reasonable, agreement with the experimental data. Both the experimental data and simulations show that As and Cu are strongly adsorbed and therefore, will mostly remain at the top of the soil profile, with a small proportion appearing in leachate. On the other hand, Cr is more mobile and thus it is present in the soil column leachate. Further simulations show that both the quantity of CCA added to the soil and the pH of the irrigation water will influence CCA transport. Simulations suggest that application of larger doses of CCA to the soil will result in higher leachate concentrations, especially for Cu and As. Irrigation water with a lower pH will dramatically increase leaching of Cu. These results indicate that acidic rainfall or significant accidental spillage of CCA will increase the risk of groundwater pollution.

History

Journal

Water, air and soil pollution: an international journal of environmental pollution

Volume

156

Pagination

357 - 377

Publisher

Kluwer Academic Publishers

Location

Dordrecht, Netherlands

ISSN

0049-6979

eISSN

1573-2932

Language

eng

Publication classification

C1 Refereed article in a scholarly journal

Copyright notice

2004, Kluwer Academic Publishers