玉米和小麦对城市污泥施用土壤中多氯联苯的吸收和传输特征

Uptake and Transport Characteristics of Polychlorinated Biphenyls in Soil Applied with Municipal Sludge in Guanzhong Area by Maize and Wheat

城市污泥施用农田能够改善土壤性状及促进作物生长,但也会使农田存在重金属和有机污染物等污染风险.多氯联苯(polychlorinated biphenyls,PCBs)作为一类持久性有机污染物,被作物吸收、累积后经食物链传递,潜在威胁着人体健康.为探究城市污泥施用农田后PCBs在土壤和作物(玉米和小麦)中的分布特征,解析玉米和小麦对土壤PCBs的吸收和传输规律与差异,以关中地区城市污泥施用土壤为研究对象,设置不同植物种属、污泥施用量和污泥类型的土壤盆栽培养试验.结果表明:①城市污泥施用后造成土壤、玉米和小麦的PCBs污染,土壤、植物根和地上部分以低氯代PCBs〔一氯代PCBs(mono-PCBs)~五氯代PCBs(penta-PCBs)〕为主,且百分含量呈依次增加趋势.②与种植前相比,种植植物后土壤中更低氯代的PCBs占主导;且土壤∑PCBs消减了20.00%~79.30%,各处理对∑PCBs的消减差异表现为玉米高于小麦、单倍污泥施用量高于双倍污泥施用量、有机质含量最高的污泥施用处理∑PCBs的消减率最高.③植物根可以吸收土壤PCBs并向地上部分传输,且吸收和传输能力与植物种属、污泥施用量和污泥类型有关,小麦对污染土壤∑PCBs及各PCBs同系物的吸收能力均强于玉米,而传输能力较弱;双倍污泥量施用下植物根对∑PCBs、一氯代PCBs(mono-PCBs)~四氯代PCBs(tetra-PCBs)和六氯代PCBs(hexa-PCBs)的吸收减弱;有机质含量最低的污泥施用下植物根对∑PCBs的吸收能力最强.研究显示,城市污泥施用会引起土壤和作物PCBs污染,种植作物能消减污染土壤PCBs,而小麦和玉米对土壤∑PCBs及各PCBs同系物的消减和吸收传输存在种属差异.

The application of municipal sludge to farmland can improve soil properties and promote crop growth,but it can also cause pollution risks such as heavy metals and organic pollutants.Polychlorinated biphenyls(PCBs),as typical persistent organic pollutants,are absorbed and accumulated by crops and passed through the food chain,posing potential risks to human health.Soil pot culture experiments with different plant species,sludge application quantities,and sludge types were conducted to explore the distribution characteristics of PCBs in soil and crops(maize and wheat)after the application of municipal sludge to farmland.The uptake and translocation characteristics of PCBs in maize and wheat were further analyzed.The results showed that:(1)The application of municipal sludge led to PCBs pollution in soil,maize and wheat.The soil,plant roots,and above-ground parts of plants were dominated by low-chlorinated PCBs(mono-PCBs-penta-PCBs),and the total percentage concentrations increased sequentially.(2)Compared with before planting,lower chlorinated PCBs were dominant in soil after planting,and∑PCBs in soil were reduced by 20.00%-79.30%.The∑PCBs reductions in different treatments were as follows:maize was higher than wheat,single sludge application was higher than double sludge application,and reduction rate of∑PCBs in sludge application with the highest organic matter content was the highest.(3)Plant roots absorbed PCBs from the soil and transfered them to the above-ground parts of plants.The uptake and transport abilities of PCBs were related to plant species,sludge application quantity,and sludge type.The uptake ability of wheat to∑PCBs and PCBs homologues in polluted soil was stronger than that of maize,though the transport ability was weaker.Double sludge application quantity weakened the uptake of∑PCBs,mono-PCBs-tetra-PCBs,and hexa-PCBs by plant roots.The uptake ability of plant roots to∑PCBs was the highest in the treatment with the lowest organic matter concentration sludge.The results demonstrated that the application of municipal sludge caused PCBs pollution in soil and crops,and planting crops could reduce the PCBs pollution in soil,while wheat and maize had species differences in the uptake and transport of∑PCBs and PCBs homologues in soils.