Authors: Linde, Mats; Öborn, Ingrid; Gustafsson, Jon

Source: Water, Air, and Soil Pollution, Volume 183, Numbers 1-4, July 2007 , pp. 69-83(15)

Publisher: Springer

Abstract:

Changes in the soil chemical environment can be expected to increase the leaching of trace metals bound in soils. In this study the mobility of trace metals was monitored in a column experiment for two contaminated urban soils. Four different treatments were used (i.e. rain, acid rain, salt and bark). Leachates were analysed for pH, dissolved organic carbon (DOC) and for seven trace metals (cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), nickel (Ni), lead (Pb) and zinc (Zn)). The salt treatment produced the lowest pH values (between 5 and 6) in the effluent whereas the DOC concentration was largest in the bark treatment (40-140 mg L⁻¹) and smallest in the salt and acid treatments (7-40 mg L⁻¹). Cadmium, Ni and Zn were mainly mobilised in the salt treatment, whereas the bark treatments produced the highest concentrations of Cu and Pb. The concentrations of Cu, Cr, and Hg were strongly correlated with DOC (r ² = 0.90, 0.91 and 0.96, respectively). A multi-surface geochemical model (SHM-DLM) produced values for metal dissolution that were usually of the correct magnitude. For Pb, however, the model was not successful indicating that the retention of this metal was stronger than assumed in the model. For all metals, the SHM-DLM model predicted that soil organic matter was the most important sorbent, although for Pb and Cr(III) ferrihydrite was also important and accounted for between 15 and 50% of the binding. The results confirm the central role of DOC for the mobilization of Cu, Cr, Hg and Pb in contaminated soils.

Keywords: chemical modelling; contaminated soil; dissolved organic carbon; Fe oxides; leaching; sequential extractions; Stockholm humic model; trace metals; urban soil

Document Type: Research article

DOI: http://dx.doi.org/10.1007/s11270-007-9357-5

Affiliations: 1: Email: Mats.Linde@mv.slu.se

Publication date: 2007-07-01

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