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Four soils contaminated by Pb-Zn mining, Pb-Zn smelting, sewage sludge application, and clay pigeon shooting, respectively, were evaluated for their ability to attenuate relatively high concentrations of supplied Cd and Pb. The retention characteristics of the polluted soils and ‘background’-unpolluted soils for Cd and Pb, were assessed by batch adsorption experiments and equilibrium dialysis titration of the soil organic component. From the sorption data it was observed that the mining polluted and sewage sludge treated soils showed no significant change in Cd affinity when compared to the unpolluted soils. However, for Pb, the reduction in the slopes in the isotherms of the sludge treated and shot over soils were significant when compared to the background soils – indicating a reduced affinity for Pb. The Cd and Pb complexation capacities of the organic component were reduced in the mining, smelter and shot over soil compared to their respective background soils. However, the complexation capacity for Cd of the sludged soil increased from 1.01 µmol Cd g-1 of organic matter to 4.38 µmol Cd g-1 of organic compared to the background soil, but, the stability constant of the organo-metal complex formed was lower (6.05 cf. 6.85). 相似文献
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The monitoring of heavy metal deposition onto soils surrounding old Pb-Zn mines in two locations in the UK has shown that relatively large amounts of Cd, Pb, Zn and, in one case, Cu are entering the soil annually. Small particles of ore minerals in windblown mine tailings were found to be contributing up to 1.46 g m?2 yr?1 of Pb, 1.41 g m?2 yr?1 of Zn and 0.027 g m?2 yr?1 of Cd. However, when these inputs from bulk deposition are compared with the concentrations of the same metals within the soil profiles it is apparent that relatively little long-term accumulation is occurring. Metals are being lost from the soil profiles, probably through leaching. A calculated relative retention parameter gave values that ranged from 0.01 to 0.17 for Cd, 0.11 to 0.19 for Zn, 0.32 to 0.63 for Cu and over 1 for Pb. These relative retention values were found to follow the order of electronegativity of the elements concerned: Pb>Cu>Zn>Cd. Distribution coefficient (Kd) values quantifying the adsorptive capacity of the mine soils for Cd and Pb showed marked differences for the two metals (12 to 69 cm3 g?1 for Cd and 14 to 126 cm3 g?1 for Pb) and may, in part, account for the two to one hundred-fold variation in the relative retention parameter for the different metals within these soils. 相似文献
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P. Smith A. Bhogal P. Edgington H. Black A. Lilly D. Barraclough F. Worrall J. Hillier G. Merrington 《Soil Use and Management》2010,26(4):381-398
The aim of this study was to assess the consequences of feasible land‐use change in Great Britain on GHG emissions mainly through the gain or loss of soil organic carbon. We use estimates of per‐area changes in soil organic carbon (SOC) stocks and in greenhouse gas (GHG) emissions, coupled with Great Britain (GB) county‐level scenarios of land‐use change based on historical land‐use patterns or feasible futures to estimate the impact of potential land‐use change between agricultural land‐uses. We consider transitions between cropland, temporary grassland (<5 yr under grass), permanent grass (>5 yr under grass) and forest. We show that reversion to historical land‐use patterns as present in 1930 could result in GHG emission reductions of up to ca. 11 Mt CO2‐eq./yr (relative to a 2004 baseline), because of an increased permanent grassland area. By contrast, cultivation of 20% of the current (2004) permanent grassland area for crop production could result in GHG emission increases of up to ca. 14 Mt CO2‐eq./yr. We conclude that whilst change between agricultural land‐uses (transitions between permanent and temporary grassland and cropland) in GB is likely to be a limited option for GHG mitigation, external factors such as agricultural product commodity markets could influence future land‐use. Such agricultural land‐use change in GB could have significant impacts on Land‐use, Land‐Use Change and Forestry (LULUCF) emissions, with relatively small changes in land‐use (e.g. 5% plough out of grassland to cropland, or reversion of cropland to the grassland cover in Nitrate Vulnerable Zones of 1998) having an impact on GHG emissions of a similar order of magnitude as the current United Kingdom LULUCF sink. In terms of total UK GHG emissions, however, even the most extreme feasible land‐use change scenarios account for ca. 2% of current national GHG emissions. 相似文献
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A major concern with the safe re‐use of biosolids on land is the potential for release of metals from organic matter in the biosolids, due to decomposition proceeding as biosolids age. To quantify the effects of biosolid aging on Cd and Zn bioavailability, two sewage sludges (Lagoon sludge and Filtered sludge) and a garden compost were incubated at 25°C and 35°C for 100 days. Changes in availability of Cd and Zn were determined using isotope dilution principles, with the materials being labelled with carrier‐free 109Cd and 65Zn. We determined isotopically exchangeable metal pools (E values) and plant available metal pools (L values) by measuring specific activities of Cd and Zn in soil extracts and in wheat plants, respectively. Changes in carbon content over time were determined using 13C‐NMR spectroscopy and chemical extraction methods, and related to changes in availability of metal pools as determined by isotopic procedures. Hot‐water‐extractable carbon content, assumed to represent easily decomposable organic matter, decreased during the 100 days by 80–190 mg kg?1. The Compost and Lagoon sludge showed no change in L values for Cd or Zn with time, but in the Filtered sludge the L values for Cd and Zn increased significantly, by 43% and 56%, respectively. The isotopically exchangeable pools of Cd and Zn did not change with incubation treatment of the biosolids. These data indicate that the potential for metal release from biosolids as organic matter decomposes depends to a large extent on the biosolid composition. 相似文献
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