我国南方典型城市土壤重金属污染特征及源汇关系分析

Pollution characteristics of heavy metals and source-sink relationship in typical city of the South China

工业化和城市化带来的重金属污染问题日益引起关注,其对环境质量、食品安全、人体健康及社会经济的可持续发展构成了严重的威胁和挑战.本文以我国南方典型城市化区域为研究对象,通过采集表层(0~20 cm)、亚表层(20~40 cm)及剖面(0~100 cm)土壤,检测土壤中8种重金属元素(砷、镉、铬、铜、汞、镍、铅、锌)的含量,并对当地95个主要污染物排放企业的空间分布进行调查,对比土壤重金属高检出区的分布特征并进行源汇关系分析.结果发现,该区域整体上以重金属Cd超标率较高,是主要污染物和需要关注的重点,与农用地土壤污染风险筛选值(0.3 mg·kg^-1)相比其超标率达71.7%.通过对排放源进行分析,确定了电子电镀和染织两个主要排放行业.工业集中区北部8种重金属元素的平均含量水平显著高于其他区域,受工业和农业干扰较少的城市公园土壤重金属含量与土壤本底值接近.As、Cd、Cr、Cu、Ni、Pb和Zn的高检出区主要集中在北部区域,研究区95个主要污染物排放单位中,72个位于城市北部,主要是电镀和染色皮革行业.进一步研究证明,这些重点排污企业加重了当地土壤中重金属的污染,是当地重金属污染的主要驱动因素.

The problem of heavy metal pollution caused by industrialization and urbanization has drawn increasing attention. Heavy metals pose serious threats and challenges to environmental quality, food safety, human health and sustainable socio-economic development. In this study, the typical urbanized areas of the South China were used as research objects. Eight heavy metal elements (including arsenic, cadmium, chromium, copper, mercury, nickel, lead, zinc) in the soil were detected by collecting surface layers (0~20 cm), subsurface layers (20~40 cm) and soil profiles (0~100 cm). The spatial distribution of 95 major pollutant discharge enterprises was investigated, and the distribution characteristics of soil heavy metal high detection areas were compared to analyze the source-sink relationship. The study found that the overall Cd exceeding the standard rate of heavy metals in the region is high, which is the main pollutant and the focus of attention. The over-standard rate is 71.7% compared with the soil pollution risk screening value of agricultural land (0.3 mg·kg^-1). By analyzing the source, two major components of electroplating and dyeing are identified. The average level of the eight elements in the northern part of the industrial concentration area is significantly higher than that of other areas, and the heavy metal content of the urban parks with less interference from industry and agriculture is close to the soil background value. The high detection areas of As, Cd, Cr, Cu, Ni, Pb, and Zn are mainly concentrated in the northern units. Of the 95 major pollutant discharge units in the study area, 72 are located in the northern part of the city, mainly in the electroplating and dyeing leather industry. Further research proves that these key polluting enterprises have increased the pollution of heavy metals in the local soil and are the main driving factors for local heavy metal pollution.