养殖废水灌溉下施用生物质炭和果胶对土壤养分和重金属迁移的影响

【目的】 养殖废水中含有丰富的养分，但也含有一定的重金属。本文研究了生物质炭和果胶对养殖废水灌溉下的土壤–植物系统养分和重金属迁移规律的影响，以利用养殖废水中的养分，并对其重金属进行调控。 【方法】 选取新乡市郊区农田土壤为供试土壤，采用根箱试验方法种植玉米。设置根箱土壤中添加1%的生物质炭和果胶，分别灌溉蒸馏水和养殖废水发酵产生的沼液。测定了土壤中养分和重金属的含量，探讨了其在土壤–植物系统的迁移规律。 【结果】 沼液灌溉的植株地上部生长与蒸馏水灌溉无显著差异。果胶相比于生物质炭可以促进植株生长。沼液灌溉时，果胶处理的根系和地上部生物量分别比对照增加了25.38%和31.21%。沼液灌溉普遍降低了根际和非根际土壤的pH，生物质炭处理和果胶处理与对照根际和非根际土壤的pH均无显著差异。沼液灌溉增加了非根际土壤的电导，生物质炭相比于果胶增加了土壤的电导。沼液灌溉增加了土壤全氮、有效磷、速效钾和有机质含量。果胶根际土壤的全磷、碱解氮、有效磷、有效Fe、有效Mn均高于生物质炭处理，生物质炭处理根际和非根际土壤的全钾和速效钾含量均高于果胶处理。沼液灌溉相比于蒸馏水灌溉，增加了植株根、茎中N含量和Ca含量。生物质炭处理植株根茎叶N含量、根茎P含量、茎K含量、根茎叶Ca含量、根茎Mg含量高于果胶处理，但果胶处理养分的转运系数较高。养殖废水灌溉增加了根际和非根际土壤中有效Cu和Zn尤其是Zn的含量。与对照相比，生物质炭降低了根际土壤Cu、Pb、Ni的含量，而果胶增加了它们的含量。沼液灌溉增加了植株根茎叶中Cu、Zn、Pb含量，果胶处理植株根系Cu、Zn、Pb、Cd、Ni含量最高，但向地上部转运较少。 【结论】 在北方碱性土壤灌溉养殖废水发酵产生的沼液时，施用生物质炭和果胶可以提高土壤肥力和植株养分含量，生物质炭通过减少土壤中有效态重金属含量以减少重金属在植物体内累积，果胶虽然增加土壤有效态重金属含量，但可以降低其向地上部的转运，避免了重金属在植物体内的累积。

Migration of nutrient and heavy metals impacted by biochar and pectin under the irrigation with livestock wastewater

【Objectives】 Livestock wastewater contains abundant nutrients, but also contains some heavy metals. Migration of nutrient and heavy metals impacted by biochar and pectin application in soil-plant system irrigated by livestock wastewater was investigated to improve the use efficiencies of nutrients and control heavy metals in the livestock wastewater. 【Methods】 A rhizobox was used to carry out experiment in maize. The tested soil was collected from the suburb of Xinxiang City, and biochar and pectin were individually added in ratio of 1% into soil. Maize was irrigated with distilled water (DW) or fermented livestock waste water (FW). The nutrients and heavy metal contents in soil and plants were determined, and the immigration of them in the plant-soil system was discussed. 【Results】 There was no difference of plant shoot biomass between the FW and DW treatments, pectin showed more effective in improving plant growth than biochar did. Under FW irrigation, the root and shoot biomass in pectin treatments were 25.38% and 31.21% higher than in no pectin addition. The rhizosphere and bulk soil pH were generally decreased by FW irrigation, there was no significant difference among the pectin, biochar and no addition treatments. The electric conductivity of bulk soil was enhanced by the FW irrigation, and biochar addition increased it more than pectin did. The soil total N, available P, readily available K and organic matter contents were increased by the FW irrigation. The rhizosphere soil total P, available N, available Fe and available Mn in the pectin treatments were higher than those in the biochar treatments, while the total and readily available K contents in both rhizosphere and bulk soil of the biochar treatments were higher than those of the pectin treatments. Compared to the DW irrigation, the N and Ca contents in the plant roots and stems were enhanced by FW irrigation. Though the contents of N in roots, stems and leaves, P in roots and stems, K in stems, Ca in roots, stems and leaves, and Mg in roots and stems of the biochar treatments were all higher than those of the pectin treatments, the nutrient translation coefficients were higher in the pectin treatments. With the FW irrigation, the available Cu and Zn contents, especially available Zn contents, in rhizosphere and bulk soils were all increased; compared with the no addition treatment, biochar decreased the Cu, Pb and Ni contents in rhizosphere soil but pectin increased their contents on the contrary. The Cu, Zn and Pb contents in roots and stems were increased because of the FW irrigation. The Cu, Zn, Pb, Ni and Cd contents of plant roots were high in the pectin treatments, but their translocation amounts to the shoots were low. 【Conclusions】 In northern alkaline soils, livestock wastewater irrigation could improve the soil fertility and plant nutrient contents of soil. Addition of biochar could decrease the heavy metal contents in plants by decreasing the available heavy metals in soil. Pectin could increase the available heavy metals in soil, but decrease their translocation to the shoots, avoiding the accumulation of heavy metals in plants to some extent.