农田不同利用方式下土壤重金属区域分异与评价

Regional Differentiation and Status of Heavy Metals in Rural Soils Under Different Patterns of Land Use

明确农村农田不同利用方式(露地菜田、大棚菜田、粮田)下土壤重金属区域分异与污染特征。采用土壤重金属单项污染指数和综合污染指数方法,对农田不同利用方式下北京、天津、河北和山东4个试区土壤重金属状况进行评价。天津试区3种利用方式农田土壤重金属Cu、Zn、Cd、Pb和As含量均明显高于河北、山东和北京3个试区,4个试区露地菜田和大棚菜田土壤重金属Cu、Zn、Cd和Pb含量均有较粮田高的趋势。总体上天津和河北两试区露地菜田和大棚菜田、山东试区大棚菜田土壤处于重金属轻污染状况,北京试区3种利用方式农田、天津和河北两个试区粮田土壤处于重金属污染警戒级,山东试区露地菜田和粮田土壤居重金属安全级。其中北京、天津和河北3个试区两种利用方式农田和山东试区大棚菜田均处于Cd轻污染状况,山东试区露地菜田和粮田土壤Cd居污染警戒级,而4个试区3种利用方式农田土壤均未受到Cu、Zn、Pb、Cr、As和Hg的污染。天津试区土壤重金属含量明显高于其他试区,可能主要与天津试区曾有污水灌溉历史有关;露地菜田和大棚菜田土壤重金属含量相对较高,可能的原因是露地菜田和大棚菜田肥料用量远高于粮田;采用单项污染指数和综合污染指数对农田土壤重金属污染评价的结果有所不同,两者结合应用能比较全面和准确地反映农田土壤重金属的污染状况。

To determine regional differentiation and pollution status of heavy metals in rural soils under different patterns of land use （bare vegetable field, greenhouse vegetable field, and grain crop field）. Status of heavy metals in agricultural soils from four rural experimental regions of Huabei plain under different patterns of land use was evaluated using the single - factor and comprehensive pollution indices. The contents of soil total Cu, Zn, Cd, Pb, and As were significantly higher in Tianjin experimental region under the three patterns of land use than that in Beijing, Hebei, and Shandong experimental regions, respectively. Higher contents of total Cu, Zn, Cd, and Pb in soils from the four experimental regions were found in the bare vegetable field and the greenhouse vegetable field compared with the grain crop field. Soils from the bare vegetable field and the greenhouse vegetable field for Tianjin and Hebei experimental regions, and from greenhouse vegetable field for Shandong experimental region were slightly contaminated according to the comprehensive pollution indices, soils under the three patterns of land use for Beijing experimental region, and from the grain crop field for Tianjin and Hebei experimental regions were at the warning heavy metal pollution level, and soils from the bare vegetable field and the grain crop field for Shandong experimental region were not contaminated. Soils under the three patterns of land use for Beijing, Tianjin and Hebei experimental regions were slightly contaminated with Cd according to the single pollution indices, soils from the bare vegetable field and the grain crop field for Shandong experimental region were at the warning Cd pollution level, whereas soils under the three patterns of land use were not contaminated with Cu, Zn, Pb, Cr, As, and Hg. A small quantity of irrigation of the polluted river water in Tianjin experimental region contributed to the accumulation of Cu, Zn, Cd, Pb, and As in soils to supply serious lack of water use in agricultural production during the period of 1970--1990. Higher contents of total Cu, Zn, Cd, and Pb in soils from the bare vegetable field and the greenhouse vegetable field compared with the. grain crop field were probably caused by long- term use of excessive chemical fertilizers and organic manures. Some differences in assessment of heavy metal status in agricultural soils were observed according to the comprehensive pollution index and the single -factor pollution index, indicating that contamination of heavy metals in agricultural soils could be better evaluated using combined comprehensive and single - factor pollntion indices.