通过大田试验研究种植5种植物(玉米、向日葵、大豆、高粱、菊花)对污灌区土壤锌形态的影响.结果表明,污灌区土壤中锌含量均未超过国家二级标准,且主要以残留态存在.土壤中各形态锌与种植前相比,除可交换态锌呈增加趋势,其余各形态锌均呈下降趋势.其中可交换态锌在向日葵土壤中增加最明显,达24.19%;碳酸盐结合态锌在玉米土壤中下降最明显,达47.68%;铁锰氧化物态锌和残留态锌在菊花土壤中下降最明显,分别达35.65%、27.46%;总锌和有机结合态锌在向日葵土壤中下降最明显,分别达15.68%、44.23%.土壤中可交换态锌含量与植物籽粒中锌含量显著相关(P〈0.05),适于用作土壤锌污染的生物评价指标.土壤中锌的生物活性系数与种植前相比,在玉米、高粱和菊花土壤中呈降低趋势,其中在玉米土壤中降低最明显,达31.43%,在大豆和向日葵土壤中呈增加趋势.总之,向日葵籽粒中重金属锌含量超出食品中锌限量标准(GB13106-1991),不宜在污灌区种植;玉米、高粱、大豆等植物籽粒中重金属锌含量均未超出食品中锌限量卫生标准(GB13106-1991),可以在污灌农田长期种植.
A field experiment located in sewage irrigated areas in Qixian County, Shanxi Province was conducted to study the effects of different plants (corn, sorghum, soybeans, chrysanthemum and sunflower) on the form of zinc in sewage irrigated farmland soil. The study result showed that the contents of zinc in sewage irrigated soil did not exceed the national second-level standard, existing mainly in residual state. Compared with different forms of zinc in pre-planting period, all forms of zinc except the exchangeable zinc content showed a downward trend. Obvious changes include the rising rate of exchangeable zinc content in sunflower soil (24.19%), the decreasing rate of carbonate-bound zinc content in corn soil (47.68%), the decreasing rate of contents of Fe-Mn oxide bound zinc (35.65%), the residual state zinc (27.46%), the decreasing rate of soil total zinc (15.68%) and the organic matter fraction zinc in sunflower soil (44.23%). The content of exchangeable zinc in soil was significantly correlated with content of zinc in seeds of plants, which would be an effective biochemical evaluation index for the pollution degree of zinc in soil. Compared with the pre-planting period, the biological activity factor of zinc in corn, sorghum and chrysanthemum soil decreased, with a significant decreasing rate in corn soil of 31.43%; the biological activity factor of zinc increased in soybeans and sunflower soil compared with that of the pre-planting period. The content of zinc in seeds of sunflower exceeded the limit standard of zinc in food (GB13106-1991), therefore we do not suggest planting sunflowers in sewage irrigated farmland soil. The content of zinc in seeds of corn, sorghum and soybeans did not exceed the national limit standard, so they can be planted in sewage irrigated farmland soil. The research result will provide theoretical basis and technical support for efficient utilization of sewage irrigated soil.