兰州市主城区土壤重金属空间分布特征及污染评价

Spatial Distribution and Pollution Assessment of Heavy Metals in Soil of Main Districts of Lanzhou City

为查明兰州市4个主要城区土壤重金属Cu、Zn、Pb的空间分布特征和环境质量状况,应用Kriging最优内插法和地累积指数法进行研究,结果表明:Cu、Zn、Pb在研究区土壤中有一定程度的累积;3种重金属含量的空间变异较大,最高值均出现在西固区;大部分区域土壤Cu含量低于背景值,大部分区域土壤Zn、Pb均大于背景值,其中Pb在城关区土壤含量普遍较高。根据地累积指数法,Cu、Pb的大部分及Zn的全部样点都在轻污染-中污染及以下水平;土壤Cu的0级样点占50%以上,但在西固区有1个强污染样点;Zn和Pb样点主要在1级水平,Zn在七里河区污染程度相对严重;城关区土壤均受到不同程度的Pb污染;安宁区土壤环境质量相对较好。

The Kriging method was used to estimate the unobserved points and generate contour maps of Cu, Zn, Pb, and the polluting status were assessed by adopting Igeo method in the study area. The results indicated that Cu, Zn, Pb were accumulated to some extent and the spatial distribution of them variated greatly. The high concentration part of Cu was found mainly in Xigu District and the concentrations of Cu were lower than its background level in a large scale and that of Zn and Pb were higher than their background levels in many areas. The high concentration parts of Zn were found in all the districts and concentrations of Pb were high in the whole Chengguan District. According to the pollution assessment, most sampling sites of Zn,Pb and all the sampling sites of Cu ranked in the second level or lower. More than half of the sampling sites of Cu were in zero level, showing a better state and most samplings of Zn and Pb ranked in the first level. Xigu District was polluted comparatively seriously by Cu and Pb in certain parts. Chengguan District was polluted by Pb in different degrees and tile concentrations of Zn showed a worse state in Qilihe District. Soil environmental quality of Anning District was the best.