中文摘要：

为准确把握西部生态脆弱区耕地质量现状,了解重金属污染对西部地区耕地质量的影响程度,采用第二次全国土地调查、多目标区域地球化学及农用地基础地力调查等数据,运用GIS技术及统计方法,以兰州市榆中县为例,在考虑重金属污染的条件下,对西部生态脆弱区耕地自然质量进行综合评价研究。结果显示：①研究区耕地立地条件、土壤物理性状相对较好,质量较好的4级耕地最多;而土壤肥力较差,质量较差2、3级耕地占耕地总面积的99.63%;②研究区As、Cd、Cr、Cu、Hg、Pb、Zn等重金属元素的平均含量均高于地区背景值,其中Cd和As最大值超过土壤环境质量污染评价标准值;③土壤重金属污染综合评价结果显示北部青城镇、中部和平镇和马坡乡的东北部为污染高值区;④耕地质量综合评估结果显示研究区耕地自然质量南部和中部川区较好,北部山区较差,除部分区域出现异常点值外,基本呈现由南向北逐渐变差的规律。以上研究结果表明,西部生态脆弱区耕地自然质量虽然主要受降雨量、坡度等自然条件的影响,但重金属造成的土壤污染已成为该区域不可忽视的耕地质量问题。

英文摘要：

In order to accurately understand the status of farmland quality and the impact of heavy metal pollution in ecologically fragile zone in western China,based on the data of second national land survey,multi-objective regional geochemical survey and soil fertility survey of agricultural land,using GIS technology and statistical methods,the comprehensive evaluation of farmland natural quality considering heavy metal pollution was conducted in Yuzhong County,Lanzhou City,Gansu Province. The results showed： ① The site conditions and soil physical properties of farmlands were relatively good in the study area,in which the class-4 farmlands whose quality was relatively good took the highest proportion. However,the fertility of farmlands was relatively poor,in which the class-2 and class-3 farmlands whose quality was relatively poor took 99. 63% of the total area. ② The average contents of As,Cd,Cr,Cu,Hg,Pb and Zn were higher than the regional background values,in which those of Cd and As exceeded the assessment standard of soil envi-ronment quality. ③ According to the comprehensive evaluation of soil heavy metal pollution,Qingcheng Town,Heping Town and northeastern part of Mapo Town were highly polluted areas. ④ The farmland natural quality in the southern and central area was better than that in the northern mountainous area,and it showed an overall trend of gradual deterioration from south to north except for some abnormal sites. In conclusion,soil pollution caused by heavy metals has become a serious problem in the ecologically fragile zone of western China,although the natural quality of farmlands is mainly affected by rainfall,slope and other natural conditions.