The effectiveness of four organic matter amendments for decreasing resin-extractable Cr(VI) in Cr(VI)-contaminated soils

Role of organic amendments on enhanced bioremediation of heavy metal(loid) contaminated soils

“…The value of organic amendments in the reduction of metal(loid)s in relation to remediation of contaminated soil and water sources is presented in Table 4. It has often been noticed that addition of organic amendments such as manures and crop residues enhances the reduction of Cr and Se [231,233,234]. Various organic materials, such as powdered leaves [240] and Pinus sylvestris bark [241], seaweed [232], black carbon Table 4 Selected references on the potential value of organic amendments in the redox reactions of metal(loid)s from soil and water.…”

“…Addition of biological waste materials, such as poultry and livestock manures, and biosolids has often been shown to increase the amount of dissolved organic carbon (DOC) in soils either by acting as a source of DOC or by enhancing the solubilization of the soil organic matter [242,243]. The easily oxidizable organic carbon and DOC fractions provide the energy source for the soil microorganisms involved in the reduction of metal(loid)s, such as Cr [234] and Se [244] and non-metals, such as N [245] and S [246]. While Cr(III) is strongly retained onto soil particles, Cr(VI) is very weakly adsorbed and is readily available for plant uptake and leaching to groundwater [247][248][249].…”

Effects of liming on Cr(VI) reduction and Cr phytotoxicity in Cr(VI)-contaminated soils

“…Brown and Sturchio (2002) suggested that XANES spectroscopy provides a nondestructive measurement of the oxidation states of chromium on the soil surface and is a useful tool to estimate the degree of Cr(VI) reduction. Thus, XANES spectroscopy has been used to examine the extent of Cr(VI) reduction after amendment by organic materials by determining the amounts of Cr(VI) remaining in soils (Chiu et al 2009;Chen et al 2010). In our previous study, the exchanger resins Dowex M4195 and Chelex 100 were used to measure the availability of Cr(VI) and Cr(III) in soils respectively and then to assess their contributions to the phytotoxicity of soil Cr on wheat seedlings (Chen et al 2010).…”

The effectiveness of ferrous iron and sodium dithionite for decreasing resin-extractable Cr(VI) in Cr(VI)-spiked alkaline soils

“…The first group of reductants includes organic compounds such as ascorbate [15], soil organic matter [6], and composts [16,17]. In our previous study, the reduction of Cr(VI) into Cr(III) by applying cattle-dung and hog-dung composts was a feasible method to decrease the amount of resin-extractable Cr(VI) in Cr(VI)-contaminated soils.…”

“…In addition, the reduction of Cr(VI) into Cr(III) with the amendment of organic matter in Cr(VI)-contaminated soils requires a long incubation time. The effectiveness of adding organic matter to decrease the Cr(VI) concentration in Cr(VI)-spiked soils is restricted by the low decomposition rate and dissolved organic carbon content of organic matter [16,17]. Therefore, due to the slow reaction, the amendment of organic matter is not the best method to decrease the risk of Cr(VI) contamination in those cases requiring immediate remediation.…”