IMAR-CMA, Department of Life Sciences, University of Coimbra, 3001-401, Coimbra, Portugal.
Arch Environ Contam Toxicol. 2012 Aug;63(2):199-208. doi: 10.1007/s00244-012-9763-6. Epub 2012 Apr 4.
Sewage sludge application to soils is regulated by its total metal content. However, the real risk of metals is determined by the fraction that is biologically available. The available fraction is highly related to the strength of metal binding by the matrix, which is a dynamic process. The evaluation of the fate of metals in time can contribute increased accuracy of ecological risk assessment. Aiming to evaluate short-term changes in metal availability when metals were applied to soil directly (metal-spiked) or by way of an organic matrix (sludge-amended), a laboratory experiment was performed using open microcosms filled with agricultural soil. A concentration gradient of industrial sludge (11, 15, 55, and 75 t/ha) that was contaminated predominantly with chromium, copper, nickel, and zinc, or soil freshly spiked with the same concentrations of these metals, were applied on top of the agricultural soil. After 0, 3, 6, and 12 weeks, total (HNO(3) 69 %) and 0.01 M CaCl(2)-extractable metal concentrations in soil and metal content in the percolates were measured. Results demonstrated that comparison between sludge-amended and metal-spiked soils may give important information about the role of sludge matrix on metal mobility and availability in soil. In sludge-amended soils, extractable-metal concentrations were independent of the sludge concentration and did not change over time. In metal-spiked soils, metal extractability decreased with time due to ageing and transport of metals to deeper layers. In general, the sludge matrix increased the adsorption of metals, thus decreasing their mobility in soils.
污水污泥的应用受到其总金属含量的限制。然而，金属的实际风险取决于其生物可利用的部分。可利用部分与基质对金属的结合强度密切相关，而这种结合强度是一个动态的过程。评估金属在时间上的归宿可以提高生态风险评估的准确性。本研究通过使用开放微宇宙填充农业土壤的实验室实验，旨在评估当金属直接（金属添加）或通过有机基质（污泥添加）施用于土壤时金属可用性的短期变化。使用受铬、铜、镍和锌污染的工业污泥（浓度分别为 11、15、55 和 75 吨/公顷）浓度梯度，或土壤中新鲜添加相同浓度的这些金属，施用于农业土壤的顶部。在 0、3、6 和 12 周后，测量土壤中总（HNO3 69%）和 0.01 M CaCl2可提取金属浓度以及渗滤液中的金属含量。结果表明，污泥添加和金属添加土壤之间的比较可以提供关于污泥基质对土壤中金属迁移性和可用性的重要信息。在污泥添加的土壤中，可提取金属浓度与污泥浓度无关，且随着时间的推移没有变化。在金属添加的土壤中，由于老化和金属向深层的迁移，金属的可提取性随时间降低。一般来说，污泥基质增加了金属的吸附，从而降低了金属在土壤中的迁移性。
