Arsenic and Chromium Partitioning in a Podzolic Soil Contaminated by Chromated Copper Arsenate

Abstract

This research combined the use of selective extractions and x-ray spectroscopy to examine the fate of As and Cr in a podzolic soil contaminated by chromated copper arsenate (CCA). Iron was enriched in the upper 30 cm due to a previous one-time treatment of the soil with Fe(II). High oxalate-soluble Al concentrations in the Bs horizon of the soil and micro-XRD data indicated the presence of short-range ordered aluminosilicates (i.e. proto-imogolite allophane, PIA). In the surface layers, Cr, as Cr(III), was partitioned between a mixed Fe(III)/Cr(III) solid phase that formed upon the Fe(II) application (25-50%) and a recalcitrant phase (50-75%) likely consisting of organic material such as residual CCA-treated wood. Deeper in the profile Cr appeared to be largely in the form of extractable (hydr)oxides. Throughout the soil, As was present as As(V). In the surface layers a considerable fraction of As was also associated with a recalcitrant phase, probably CCA-treated woody debris, and the remainder was associated with (hydr)oxide-like solid phases. In the Bs horizon, however, XAS and XRF findings strongly pointed to the presence of PIA acting as an effective adsorbent for As. This research shows for the first time the relevance of PIA for the adsorption of As in natural soils.

Immobilization of Cu and As in two contaminated soils with zero-valent iron – Long-term performance and mechanisms

“…Consequently the EXAFS interpretation implies that arsenate was primarily complexed to aluminum hydroxides in the AsUNT and that surface complexation to both aluminum and that iron (hydr)oxide was important in AsZVI. It is well known that arsenate adsorbs strongly to both aluminum and iron (hydr)oxides in soil (Hopp et al, 2008;Manning, 2005) and both are stable at the pH (almost 8) of the samples. Oxalate-extractable aluminum and iron (Table 1) indicated about 1/3 iron and 2/3 aluminum (hydr)oxides in AsUNT while the relation was the opposite, 2/3 iron and 1/3 aluminum (hydr)oxides in AsZVI which agrees well with the EXAFS interpretations.…”

“…Arsenate is strongly bound as inner-sphere surface complexes to iron and aluminum (hydr)oxides in soils (Hopp et al, 2008;Violante and Pigna, 2002). Earlier investigations of ZVI-stabilized As-contaminated soil (Komarek et al, 2013;Mench et al, 2006) …”

Synchrotron‐based X‐Ray Approaches for Examining Toxic Trace Metal(loid)s in Soil–Plant Systems

“…Studying an industrially contaminated soil, Terzano et al (2007) reported that Cr was present largely as chromite. In a similar manner, Szulczewski et al (1997) examined contaminated soils from the United States and found that <10% was present as Cr(VI) in most samples, while Hopp et al (2008) examined a CCA contaminated soil and reported that Cr was present as Cr(III), either in a recalcitrant phase (such as residual CCA-treated wood) or in a mixed Fe(III)/Cr(III) solid phase. This reduction of Cr(VI) to Cr(III), such as during the remediation of a contaminated soil, can occur due to the influence of organic matter.…”

The influence of temperature, pH/molarity and extractant on the removal of arsenic, chromium and zinc from contaminated soil

“…The untreated soil contains substantial amounts of Fe and 2% organic matter. Arsenic has been shown to co-locate with Fe, Cr, Cu and Zn-Fe in CCA-contaminated soil (Gräfe et al 2008;Hopp et al 2008) and combines with Zn to form adamitelike and koritnigite-like precipitates on goethite surfaces (Gräfe and Sparks 2005). Zn is a rather mobile element in acidic and oxidised soils (McBride 1994).…”