Behavior of Chromium in Soils: II. Hexavalent Forms

Abstract

Adsorption and reduction of added Cr(VI) were characterized in soils with contrasting pH's, organic matter contents, and chemical and mineralogical properties.Presence of soil organic matter brought about spontaneous reduction of Cr(VI) to Cr(III), even at pH's above neutrality. Reduction did not occur in soils very low in organic matter unless an energy source was added. Cow manure added to practically organic‐free Cecil B2 reduced Cr(IV) only after the pH had been lowered below 3 with HCl.The solubility of Cr(VI) in the presence of excess Al changed in a pattern remindful of orthophosphate. All of the soils, except a pH 7.8 Cca horizon material, adsorbed Cr(VI). Presence of orthophosphate prevented the adsorption of Cr(VI), presumably by competition for the adsorption sites. Consistent with this finding, KH2PO4 was found to be the best extracting agent for Cr(VI).It was concluded that behavior of Cr(VI), if it remains in soils, is similar to that of orthophosphate. However, unlike phosphate, Cr(VI) is quickly reduced by soil organic matter. Thus, Cr(VI) added to a soil will remain mobile only if its concentration exceeds both the adsorbing and the reducing capacities of the soil.

Chromium and Nickel Accumulation by Plants Along an Altitudinal Gradient in Western Carpathian Secondary Spruce Stands

“…On the other hand, faster decomposition of soil organic matter of less acidic cambisols may result in the Cr amount becoming more available to plants. Similar findings were noted by [38]. According to [6], above, all presence of Cr in the external environment leads to changes in the growth and development pattern of the plants.…”

Soil humic acids may favour the persistence of hexavalent chromium in soil

“…On the other hand, transport and reduction of Cr(VI) in soil ultimately reflects the interdependent influences of chemical, physical and microbial processes in the contaminated soil. More than three decades ago Bartlett and Kimble (1976) and recently also several other scientists (Banks et al, 2006;Jardine et al, 1999), recognised that Cr(VI) can be rapidly reduced to Cr(III) by soil organic matter. In fact, Cr(VI), being a strong oxidant, can be readily reduced to Cr(III) in the presence of various electron donors (Nakayasu et al, 1999;Palmer and Wittbrodt, 1991).…”

A physico-chemical analysis of soil and selected fruits in one rehabilitated mined out site in the Sierra Rutile environs for the presence of heavy metals: Lead, Copper, Zinc, Chromium and Arsenic

“…Cr(VI) was found to be highly mobile in alkaline soils (Griffin and Shimp, 1978) and can be reduced to Cr(III) under normal soil pH and redox conditions. Soil organic matter has been identified as the electron donor in this reaction (Bartlett and Kimble, 1976). The presence of sulfate can enhance Cr(VI) adsorption to kaolinite (Zarchara et al, 1988).…”