白银市日光温室土壤养分累积特征及重金属污染现状评价

以甘肃省白银市的日光温室土壤为研究对象，调查分析了土壤剖面养分累积状况和土壤电导率、pH值的变化；对土壤重金属Cd、As、Pb、Cr、Cu、Zn和Ni含量进行了测定，采用单项质量指数与综合质量指数相结合的方法对土壤重金属的环境质量状况进行了评价。结果表明，日光温室土壤有机质、硝态氮、速效磷和速效钾含量显著高于农田土壤，其中速效磷在0-40 cm土层和速效钾在0-60 cm土层累积尤为明显。温室栽培条件下土壤电导率高于农田土壤，雒家滩温室土壤表层EC值为0.94 mS·cm-1，超过蔬菜的生育障碍临界点（EC〉0.50 mS·cm-1）。大部分温室土壤Cd含量超过国家土壤环境质量三级标准，其中雒家滩温室土壤Pb、Zn、Cd、As含量超过温室蔬菜地土壤环境质量评价标准（HJ 333—2006）限量值。根据各重金属的单项与综合质量指数，靖远日光温室土壤环境质量为2级，属于尚清洁水平，而雒家滩和重坪日光温室土壤环境质量为3级，属于超标水平，不适宜发展无公害蔬菜。

Characteristic of Nutrient Accumulation and Heavy Metal Pollution Assessment in Greenhouse Soils in Baiyin City

A survey was made to investigate on soils for greenhouse vegetable production in Baiyin region, Gansu to characterize nutrient accumulations in soil profile, electrical conductivity （EC）and pH values. The contents of heavy metals such as Cd, As, Pb, Cr, Cu, Zn and Ni in soil were determined and further assessed using methods combining single quality index and comprehensive quality index. The results showed that contents of soil organic matter, nitrate-N, available P, available K in greenhouse soils were significantly higher than those in open field soils. An increased available P and K concentrations in layers of 0-40 cm in greenhouse soils were noted. Soil EC was higher in greenhouse culture than in open field. Soil collected in Luojiatan had the EC value of 0.94 mS·cm^-1, exceeding the threshold value of vegetable growth （ 0.5 mS·cm^-1 ）. The soil Cd concentration in soils collected from most of greenhouses exceeded the third-class threshold set in the National Soil Environmental Quality Standard GB 15618--1995. The concentrations of Pb, Zn, Cd, As in soils collected from Luojiatan exceeded the standard threshold set for greenhouse vegetable production HJ 333--2006. According to the single quality index and comprehensive quality index of soil heavy metals, the Jingyuan soil belonged to the second class, and was considered to be clean. By contrast, the soils collected from Luojiatan and Chongpin belonged to the third class, exceeding the threshold, and was considered to be not suitable for the cultivation of pollution free vegetables.