基于^(137)Cs示踪的丹江口市农用地土壤侵蚀与有机质流失分析

Evaluating Soil Erosion and Organic Matter Loss in the Danjiangkou City Using ^(137)Cs Tracing Method

运用137Cs示踪技术探讨了丹江口市小流域不同土地利用方式的土壤侵蚀,并分析了137Cs含量与有机质和重金属含量之间的关系。结果表明:农用地土壤侵蚀速率从大到小依次为沟谷旱地>坡耕地>菜田>水田>草地>灌丛,耕作土的侵蚀强度多为中度和强度侵蚀,非耕作土则是微度和轻度侵蚀;不同土地利用方式对土壤有机质和重金属分布影响很大,有机质含量分布规律为草地>灌丛>菜田>水田>沟谷旱地>坡耕地;Pb与Ni含量为灌丛>草地>坡耕地>沟谷旱地>菜田>水田;Cr与Cu含量为灌丛>菜田>坡耕地>草地>沟谷旱地>水田;Zn含量为灌丛>菜田>草地>坡耕地>沟谷旱地>水田。对137Cs含量与土壤有机质、重金属含量进行回归分析的相关系数均在0.7以上,说明在景观简单的小流域,可以利用137Cs含量和数学模型预测土壤有机质和重金属的含量变化。

Based on ^137Cs tracer method, the soil erosion rate, organic matters and heavy metals loss on the agricultural lands of Danjiangkou city, Hubei Province, were studied. The results showed that predicted soil erosion rates for different land use varied from 599.07 t/km^2·a to 6 055.5 t/km^2·a, the highest erosion rates are observed in dry land distributing on hilly areas, followed in sequence by cultivated slope soils, kale yard soils, paddy soils, grassland soils and shrub soils. Erosion intensity belongs to moderate water erosion （quite obvious soil loss） and strong water erosion （relatively high soil loss） in cultivated soil, and slight water erosion （no soil loss or inconspicuous loss feature） and light water erosion （relatively obvious soil loss） in uncultivated soil. Distribution of organic matters were increased in the following order： grassland soil 〉shrub soil〉kale yard soil 〉paddy soil 〉dry land soil 〉 cultivated slope soil. The increasing order of Pb and Ni is shrub soil〉grassland soil 〉 cultivated slope soil 〉dry land soil〉kale yard soil 〉paddy soil, and Cr and Cu is shrub soil〉kale yard soil 〉 cultivated slope soil 〉grassland soil〉dry land soil 〉 paddy soil, and Zn is shrub soil〉kale yard soil 〉grassland soil〉 cultivated slope soil〉dry land soil 〉paddy soil . High correlation was apparent between ^137Cs concentrations and soil organic matters （ R =0. 721）, soil Cu （ R =0. 751）,soil Cr （ R =0. 886）, soil Pb （ R =0. 799）, soil Zn （ R =0. 756） and soil Ni （ R =0. 724）, so we can forecast the changes of organic matters and heavy metals based on ^137Cs concentrations in a small watershed.