Human activity and related land use change are the primary cause of accelerated soil erosion, which has substantial implications for nutrient and carbon cycling, land productivity and in turn, worldwide socio-economic conditions. Here we present an unprecedentedly high resolution (250 x 250 m) global potential soil erosion model, using a combination of remote sensing, GIS modelling and census data. We challenge the previous annual soil erosion reference values as our estimate, of 35.9 Pg yr(-1) of soil eroded in 2012, is at least two times lower. Moreover, we estimate the spatial and temporal effects of land use change between 2001 and 2012 and the potential offset of the global application of conservation practices. Our findings indicate a potential overall increase in global soil erosion driven by cropland expansion. The greatest increases are predicted to occur in Sub-Saharan Africa, South America and Southeast Asia. The least developed economies have been found to experience the highest estimates of soil erosion rates.

Biochar produced by thermal decomposition of biomass under oxygen-limited conditions has received increasing attention as a cost-effective sorbent to treat metal-contaminated waters. However, there is a lack of information on the roles of different sorption mechanisms for different metals and recent development of biochar modification to enhance metal sorption capacity, which is critical for biochar field application. This review summarizes the characteristics of biochar (e.g., surface area, porosity, pH, surface charge, functional groups, and mineral components) and main mechanisms governing sorption of As, Cr, Cd, Pb, and Hg by biochar. Biochar properties vary considerably with feedstock material and pyrolysis temperature, with high temperature producing biochars with higher surface area, porosity, pH, and mineral contents, but less functional groups. Different mechanisms dominate sorption of As (complexation and electrostatic interactions), Cr (electrostatic interactions, reduction, and complexation), Cd and Pb (complexation, cation exchange, and precipitation), and Hg (complexation and reduction). Besides sorption mechanisms, recent advance in modifying biochar by loading with minerals, reductants, organic functional groups, and nanoparticles, and activation with alkali solution to enhance metal sorption capacity is discussed. Future research needs for field application of biochar include competitive sorption mechanisms of co-existing metals, biochar reuse, and cost reduction of biochar production.Published by Elsevier Ltd.

The Standards, Measurements and Testing Programme (formerly BCR) of the European Commission proposed a three-step sequential extraction procedure for sediment analysis, following extensive expert consultations and two interlaboratory studies. This scheme was recently used to certify the extractable trace element contents of a sediment reference material (CRM 601). Although this procedure offers a means to ensure the comparability of data in this field, some difficulties concerning the interlaboratory reproducibility still remain, and a new project is currently being conducted to determine the causes of poor reproducibility in the extraction scheme. The final objective of the project is the certification of new sediment and soil reference materials for their extractable contents of Cd, Cr, Cu, Ni, Pb and Zn. This paper presents the results of a small-scale interlaboratory study, which aimed to test a revised version of the extraction schemes by comparing the original and the modified protocols using the CRM 601 sample. This work offers an improvement to the BCR sequential extraction procedure through intercomparison exercises. This improved procedure will allow the obtaining of CRMs to validate analytical data in the analysis of soils and sediments, and it will also facilitate comparability of data in the European Union.

采取适宜的措施对土壤重金属污染进行修复是当前的研究热点。该研究采用缺氧高温热解法成功制备出一种新型污泥生物炭（SC）,并用于土壤重金属铬（Cr）和镉（Cd）的修复。试验结果表明,所制备的污泥生物炭呈多孔结构且有丰富的含氧官能团和多种矿物质组分,污泥生物炭的施加不仅能有效地改善土壤的理化性质和提升土壤肥力,还能增强土壤酶活性和土壤微生物丰度。在40 d内,污泥生物炭对土壤重金属Cr和Cd的修复固定效率分别能达到69.2%和93.2%,Cr和Cd的形态是以残渣态为主。在盆栽试验中,污泥生物炭通过固定土壤重金属Cr和Cd,有效阻控Cr和Cd在青菜中各部位的积累,降低了重金属的生物可利用性。基于批实验结果和XPS分析结果,提出污泥生物炭修复土壤重金属Cr和Cd的可能反应机制,Cr的修复主要通过吸附、还原、络合和沉淀的作用,形成较稳定态的物质如Cr₂O₃、Cr(OH)₃和FeCr₂O₄等,而Cd的修复主要是通过吸附和沉淀的作用形成如Cd(OH)₂和CdO等稳定态物质。该研究不但为污泥生物炭在土壤重金属Cr和Cd修复提供理论基础和技术支撑,也实现了市政污泥的“以废治废”。