西南地区典型工矿业城市土壤—作物系统中重金属和硒元素特征及评价

Characteristics and evaluation of heavy metals and selenium in the soil-crop system of a typical industrial and mining city in southwest of China

【目的】查明西南地区典型工矿业城市—云南安宁地区农作物及根系土壤重金属和硒元素的分布特征,掌握该区域农产品中重金属污染现状以及有益元素硒含量现状,促进科学管理和使用土地,保障食品安全,促进农业经济健康发展。【方法】野外采集水稻、玉米、食用玫瑰、水果、豆类蔬菜和烟叶及对应根系土壤样品,实验室测定分析根系土壤及农作物中的重金属As、Cd、Cr、Cu、Hg、Ni、Pb、Zn和Se含量。分别采用了Hankanson潜在生态风险指数法和单项污染指数法对土壤和农作物中重金属污染状况进行评价,并开展相关性分析。【结果】水稻根系土有17%样点Cd、食用玫瑰根系土有5%样点Pb以及烟叶根系土有8%样点As超标,其余均达到相关标准。根系土壤中Hg、Cd、As、Pb潜在生态风险高,尤其Hg达到了极强风险。农作物中Cd、Pb、Hg在一定程度超过相关标准,水稻中Cd、Pb、Hg超标率分别为17%、17%和5%,玉米和食用玫瑰中Pb超标率分别为5%和10%。土壤中高风险Hg在农作物的可食用部分富集程度不显著。水稻籽粒中Cd和Se分别与土壤Cd和Se含量呈现正相关性。【结论】安宁地区农作物重金属含量总体处于基本安全水平,研究区土壤重金属元素虽富集,但其在作物籽粒、果实、叶片等可食用部分富集程度不高,仅在水稻中Cd、Pb存在部分超标,籽粒中Cd主要来自于受工业企业三废排放污染的低pH土壤。

【Objective】The purpose of this study was to identify the distribution characteristics of heavy metals and selenium elements in crops and root soils in Anning, Yunnan, a typical industrial and mining city in southwest China. It can help to know the current situation of heavy metal pollution and beneficial element selenium content in agricultural products in the region, promote scientific management and use of land, ensure food safety and promote the healthy development of agricultural economy. 【Method】Rice, corn, edible roses, fruits, legumes, tobacco and corresponding root soils were sampled in the field. The contents of heavy metals As, Cd, Cr, Cu, Hg, Ni, Pb, Zn and Se in soils and crops were determined. The Hankanson potential ecological risk index method and the single factor index method were used to evaluate the pollution status of heavy metals in soil and crops, respectively, and the correlation analysis was carried out.【Result】17% samples of Cd in rice root soil, 5% samples of Pb in edible rose root soil and 8% samples of As tobacco root soil were above the standard, and the rest reached relevant standards. The potential ecological risk indices of Hg, Cd, As, Pb and Hg in the root soil were high, and especially Hg reached a very strong potential ecological risk. Cd, Pb and Hg in crops exceeded the relevant standards to a certain extent. The excess rates of Cd, Pb and Hg in rice were 17%, 17% and 5%, respectively, and the excess rates of Pb in corn and edible roses were 5% and 10%, respectively. The high-risk Hg in the soil was not significantly enriched in the edible parts of crops. Cd and Se in rice grains showed positive correlation with soil Cd and Se contents, respectively.【Conclusion】The heavy metal content of crops in Anning area was generally at a basic safe level. Although heavy metal elements were enriched in the soil in the study area, they were not highly enriched in edible parts such as crop grains, fruits, leaves, etc. The only problem was that a part of points of Cd and Pb exceeded the standard in rice. Cd mainly came from low pH soil polluted by the wastes of industrial enterprises.