Zinc And Cadmium Distribution And Leaching In A Metalliferous Peat

Abstract

Peat soils with a gradient of naturally high Cd and Zn (up to 190 and 70,000 mg/kg, respectively) were sampled at several depths from a wetland overlying Zn-rich dolomitic bedrock. Total concentrations of Zn, Cd and S were generally much higher in the seasonally water-saturated subsoils than at the surface. Leaching studies with intact soil columns showed the subsoils generally have a greater tendency to release Zn, Cd and S than the topsoils. Zn and Cd leaching were correlated to sulfate dissolution, with 6 successive leaching events removing up to 4% and 13% of the total Zn and S, respectively, from the most metal-rich subsoils. Relative leaching losses were less from the surface soils, not exceeding 1% and 3% of total Zn and S. Because Zn was relatively more soluble and extractable by 0.01 M CaCl 2 than Cd, Zn/Cd ratios in column leachates and field-sampled groundwater were higher than the soil Zn/Cd ratios. Consequently, the potential for loss of Zn from the soil by leaching was higher than that of Cd, particularly from the subsoil. Nevertheless, some soil layers of the profile were enriched in total Zn relative to Cd, indicated by Zn/Cd ratios well above that of the Cd-rich sphalerite in the parent dolomitic rock. This enrichment may be explained by historical migration and re-immobilization of Zn as sulfides. The low solubility of Cd in the peats despite high total Cd suggests preferential immobilization of this metal by organic sulfur or sulfide.

Fate of cadmium in the rhizosphere of Arabidopsis halleri grown in a contaminated dredged sediment

“…Previous studies on mixed metallic sulfides suggested different sensitivities of metals towards oxidation, with preferential release of Zn relative to Cd (O'Day et al, 1998;Barret and McBride, 2007). The same tendency was observed in Zn, Cdcontaining soils rich in sulfur (McBride et al, 2006;de Livera et al, 2011). These results are not in contradiction with our results because in the Scarpe sediment, Cd was mostly present in a mixed (Zn, Cd, Fe)sulfide, whereas Zn was mostly present as pure ZnS.…”

Accounting for surface roughness effects in the near-infrared reflectance sensing of soils

“…The "Elba" soil should not be confused with the Elba soil series in southeastern Ohio. Selected soil characteristics obtained from Macedo and Bryant (1987), Jacobson et al (2005) and McBride et al (2006) are listed in Table 1. The colors of the five soils were measured by using Munsell Soil Color Charts.…”

Alleviating Moisture Content Effects on the Visible Near-Infrared Diffuse-Reflectance Sensing of Soils

“…The Elba soil should not be confused with the Elba soil series in southeastern Ohio. Selected soil characteristics obtained from Jacobson et al (2005) and McBride et al (2006) are listed in Table 1 of Wu et al (2009). The bulk density of the various samples, needed if one wanted to transform the gravimetric water contents used in this text into volumetric water contents, are provided in Table 2 of Wu et al (2009).…”