平凉市典型作物种植区土壤重金属污染状况及其分布特征

土壤重金属污染已严重危害粮食安全与人类健康。为了解平凉市土壤重金属污染现状，摸清典型作物生长、生产环境，明确土壤重金属空间分布特征及污染源。选取506个典型作物种植区耕层土样，测量其重金属含量，并利用内梅罗指数法和潜在生态危害指数法进行土壤重金属污染评价。结果表明，平凉市土壤重金属污染等级为清洁的样品占99.41 %、尚清洁占0.59 %；潜在生态危害等级轻微的土壤样品占95.85 %、中等生态危害占4.15%。506 个点位样品中，铅和砷2种土壤重金属元素有部分超标，超标率Pd为0.45%、As为0.90%。从地理区域来看，土壤重金属潜在生态危害程度在平凉市的分布为中部 > 西部 > 东部；从土壤类型来看，土壤重金属污染占比较大的土类主要为山地草甸土、灰褐土、新积土和红粘土。

Soil Heavy Metal Pollution Status and Its Spatial Distribution Characteristics of Typical Crop Planting Areas in Pingliang

Contamination of soil with heavy metals has seriously endangered human health and food security. To understand the current situation of soil heavy metal pollution, to find out the growth and production environment of typical crops, and to clarify the spatial distribution characteristics and pollution sources of heavy metals in Pingliang, 506 farmland topsoils were collected and their heavy metal contents were measured. Results showed that the proportions of tested samples marked as clean grade and still clean grade of soil heavy metal pollution in Pingliang were 99.41% and 0.59%, respectively. The proportions of potential ecological hazard grades of minor and moderate were 95.85 % and 4.15%, respectively. Among samples from 506 points, 2 soil heavy metal elements exceeded the standard and the excess rates were Pd as 0.45% and As as 0.90%. The potential ecological hazard of soil heavy metals by geographic region was Central > West > East. In terms of soil type, the soil types with a large proportion of soil heavy metal pollution were mountain meadow soil, gray-brown soil, new accumulation soil and red clay soil.