Abstract:

In order to explore heavy metal pollution in high geological background watershed (MS) of northwest Guizhou, TSP samples were collected in four seasons from May 2018 to November 2020 and their micro-morphology and included heavy metals (Cd, As, Pb, Cr, Cu, Ni, and Zn) were measured to study the concentrations, seasonal variations, and health risks. Additionally, samples in the control area (HS) with no obvious pollution source were also collected. The heavy metal concentrations in the TSP were measured by ICP-MS and micro-morphology and energy spectrum of the TSP were examined by SEM-EDS. The human health risks were evaluated by the health risk model of heavy metal exposure assessment recommended by US EPA. The results showed that the TSP micro-morphology in the polluted area was mainly presented as regular shapes of “lumps”, “flakes”, and “layers”, as well as irregular shapes of “spheroid” and “fluffy”. O, Si, Ca, C, and Zn were the characteristic elements, revealing from dust and industrial pollution source. In the control area, TSP mainly presented in shapes of “flaky”, “layered”, “lumpy”, and “spheroid”. O, Si, and Ca were the characteristic elements, revealing from mineral and soil sources. The TSP heavy metal concentrations ranged from 55.69 μg∙m^-3 to 84.52 μg∙m^-3 and from 130.27 μg∙m^-3 to 218.22 μg∙m^-3 in the control area and polluted area, respectively, showing seasonal variations: winter>spring>autumn>summer. Cd, As, Pb, and Zn concentrations in TSP in the polluted area were significantly higher than these in the control area. Pb and Zn concentrations were 10.12 and 14.43 times higher in polluted area than these in control area. Health risk assessment results suggested that the total non-carcinogenic risk (HI) values of heavy metals were both less than 1, suggesting no non-carcinogenic health risk in both control and polluted areas. The carcinogenic risk values (R) of Cd, Cr and Ni in the two study areas were all in the range of 10^-7-10^-4. The R values of Cd and As were much higher than these in non-geological high background areas. R values of As in the two study areas were both higher than 10^-4, indicating potential health risks. We should pay more attention to the carcinogenic risks of atmospheric TSP As in the high geological background areas of northwest Guizhou.

Key words: TSP, seasonal distribution, microscopic morphology, heavy metals, health risk assessment

摘要：

为探究黔西北地质高背景区,工业污染小流域（MS）的大气TSP微观形貌及其载带重金属（Cd、As、Pb、Cr、Cu、Ni、Zn）的质量浓度、季度分布特征和健康风险,以没有明显污染源的小流域（HS）为对照,于2018年5月—2020年11月分四季采集大气TSP样品,使用ICP-MS测定TSP的重金属（Cd、As、Pb、Cr、Cu、Ni、Zn）质量分数,SEM-EDS对TSP的微观形貌以及能谱进行分析;并采用US EPA推荐的人体暴露健康风险评价模型对TSP重金属健康风险进行评价。结果表明,污染区TSP微观形貌主要为规则的“块状”、“片状”和“层状”,以及不规则的“球状”和“蓬松状”,O、Si、Ca、C、Zn为特征元素,呈现扬尘和工业源污染特征;对照区TSP为“片状”、“层状”、“块状”和“类球状”,以O、Si、Ca为特征元素,呈现矿物源和土壤源的特征。对照和污染区的TSP质量浓度范围分别为55.69—84.52 μg∙m^-3和130.27—218.22 μg∙m^-3,均呈现冬>春>秋>夏的趋势;污染区的TSP中Cd、As、Pb、Zn的质量浓度显著大于对照区,其中,Pb和Zn的质量浓度分别是对照区的10.12倍和14.43倍。健康风险评价结果表明,两个区的重金属非致癌风险总值（HI）均小于1,没有非致癌健康风险;两个区的Cd、Cr和Ni的致癌风险值（R）均处于10^-7—10^-4之间,其Cd、As的R值远高于非地质高背景区,As的R值都达到10^-4以上,存在As的潜在健康风险,在黔西北地质高背景区需注意防范大气TSP中 As的潜在致癌风险。

关键词: TSP, 季节分布, 微观形貌, 重金属, 健康风险评价