重金属在污泥长期施用土壤-作物系统的累积状况及淋溶特性

Analysis of heavy-metal accumulation and leaching features in the soil-plant system due to long-term application of sewage sludge

污泥农用导致的相关环境风险和粮食安全问题不容忽视。连续3 a向酸性黄壤（S1）和石灰性土（S2）中施加低污染（W1）和高污染（W2）污泥，通过盆栽试验和淋溶试验研究了污泥长期农用条件下Zn、Cd、As、Cr对土壤、作物和水体的环境风险。结果表明：1）施用污泥后Zn和Cd在石灰性土中的累积速率均高于酸性黄壤；2）施加高污染污泥后，重金属在玉米、小麦、菠菜等农作物可食部分的累积量均高于施加低污染污泥的处理；3）在污泥连续施用条件下，玉米对重金属累积量不显著，小麦和菠菜的累积量则较高（如小麦籽粒Cd、Zn、As质量比分别为0.09~0.16 mg/kg、64.99~103.45 mg/kg和0.22~0.4 mg/kg，菠菜对应值分别为0.10~0.44 mg/kg、5.19~36.73 mg/kg和0.02~0.11 mg/kg），大部分超过国家食品安全标准（GB/T 5009.36—2003）相关限定值；4）随淋溶次数增加，各处理组淋溶水中重金属的迁移速率逐渐降低并趋于稳定，但黄壤＋高污染污泥处理组中Zn、Cd、As和Cr的释放率（分别为0.83%、1.67%、0.56%和0.32%）高于对应的石灰性土＋高污染污泥处理组（分别为0.69%、1.16%、0.41%和0.28%），表明重金属在黄壤中相对石灰性土壤中更易向水体迁移，存在较大的环境安全风险。

The paper takes it as a research goal to provide an analysis of heavy-metal accumulation and leaching features in the soil-plant system due to the long-term application of sewage sludge with the increase of sewage treating plants and corresponding improvement of the sewage-treating rate in China in recent years, which means that the substantial increase of the sludge production has resulted in considerably protruding environmental problems. Among them, a particularly specific one is the environmental risks and food safety issues associated with the farm utilization of sludge. It is due to the above situation, we have chosen two types of sewage sludge with heavy and light heavy-metal contaminants in the two types of soil, namely, the acid yellow soil （S1） and the calcareous soil （S2）. The results of our tests indicate that （1） The accumulation rates for Zn and Cd in the calcareous soil after the utilization of sludge, both of which prove heavier than those in the acid yellow soil respectively; （2） The accumulation of heavy metals in the edible parts of maize, wheat and spinach heavily contaminated proves greater than that exposed to with less polluted sludge; （3） Under the condition of application of sludge, the accumulation of heavy metals proves insignificant in maize, but elevated in wheat and spinach （e.g., 0.09-0.16 mg/kg, 64.99-103.45 mg/kg and 0.22 0.4 mg/kg respectively）, for Cd, Zn and As in wheat; the corresponding values for spinach turn to be 0.10-0.44 mg/kg, 5.19-36.73 mg/kg and 0.02-0.11 mg/kg, most of which exceeded the corresponding Chinese national standard stipulated limits （GB/T 5009.36—2003）; （4） The migration rates of heavy metals in all the leaching solutions treated have been found gradually decreased and become stabilized with the increase of the leaching frequency. However, the releasing rates of Zn, Cd, As and Cr in the group treated with acid yellow soil and heavily contaminated sludge （0.83%, 1.67%, 0.56% and 0.32%, respectively） prove to be greater than those of the corresponding groups with treating the calcareous soil and heavily polluted sludge （0.69%, 1.16%, 0.41% and 0.28%）, which suggests that heavy metals in the acid yellow soil are more likely to be migrating and transferring into the water compartment, in relation to that in the calcareous soil.