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    珠江源老黑山区黑色岩系风化壳重金属风险及影响因素

    Risk assessment and influencing factors of heavy metals in the weathered crust of black rock series from the Laoheishan area in Zhujiangyuan (Yunnan)

      摘要
    • 摘要:
      研究目的 黑色岩系通常富含重金属，多种自然和人为因素导致山区的风化壳在地表形成细小颗粒进入耕地，威胁粮食安全和人体健康，厘清其重金属潜在的风险及影响因素意义重大。
      研究方法 于2024年5月在珠江源区黑色岩系分布的老黑山区采集弱风化—半风化—全风化基质样品共9套，分析了As、Cd、Cr、Cu、Hg、Ni、Pb、Zn、S、C、主量元素和pH，运用污染负荷指数法、潜在生态风险指数和健康风险评估模型法对潜在重金属污染状况、生态风险和人体健康风险进行评价，通过相关性分析、冗余分析讨论了其影响因素。
      研究结果 风化壳pH范围为3.18~9.02，均值6.08，以酸性为主，Cu、Cd、Ni、Cr、As、Zn超过风险筛选值的比分别为44.4%、40.7%、22.2%、14.8%、11.1%和7.4%，其中Cd超过风险管控值的比例为16.7%。污染负荷指数法评价结果显示，风化壳整体呈轻微污染。潜在生态风险指数法评价结果显示，以轻度生态风险和中度生态风险为主。非致癌危害指数(HI)和致癌风险指数(CRI)显示，儿童HI和CRI超过限值的比例分别为37.04%和40.74%，成人CRI超过限值的比例为11.11%。对生态风险贡献最大的前两种重金属是Hg和Cd，对人体健康风险贡献最大的是Cr和As。MgO、Na2O、K2O、P2O5、Fe2O3、S含量和pH以及地表植物量、坡向和侵蚀程度对全风化层和半风化层潜在重金属污染和风险影响较显著，SIC、SOC、S、坡位和岩层倾角对弱风化层的影响较显著。
      结论 研究区黑色岩系风化壳潜在重金属污染和风险主要处于轻度至中度水平，但因黑色岩系在中国及全球陆地大面积分布，极端降雨、耕地平整或开挖建设时，可能引发大规模污染风险。

       

      Abstract:
      This paper is the result of environmental geological survey engineering.
      Objective Black rock series are usually rich in heavy metals. Extreme rainfall can cause the weathered crust of the black rock series in the mountainous area of Zhujiangyuan (Yunnan) to break into fine particles on the ground surface, thereby threatening food security and human health. Therefore, it is of great significance to clarify the potential risks and influencing factors of the heavy metals therein.
      Methods In May 2024, a total of 9 sets of weakly weathered−semi-weathered−completely weathered matrix samples were collected in a mountainous area where black rock series are widely distributed in Zhujiangyuan, Qujing, Yunnan. The major elements, S, C, As, Cd, Cr, As, Cd, Cr, Cu, Hg, Ni, Pb, Zn and pH were analyzed. The pollution load index method, potential ecological risk index method, and health risk assessment model method were used to evaluate the heavy metal pollution status, potential ecological risks, and human health risks. The influencing factors were discussed through correlation analysis and redundancy analysis.
      Results The weathered crust has pH ranging from 3.78 to 9.02 (with an average of 6.08), being characterized by acidic. The proportions of Cu, Cd, Ni, Cr, As, and Zn exceeding the risk screening values are 44.4%, 40.7%, 22.2%, 14.8%, 11.1%, and 7.4% respectively, and the proportion of Cd exceeding the risk control value is 16.7%. The evaluation results of the Pollution Load Index Method show that the weathered crust as a whole presents light pollution. The evaluation results of the Potential Ecological Risk Index Method indicate that it is mainly characterized by light and moderate ecological risks. The human health risk assessment reveals that the proportions of non-carcinogenic hazards and carcinogenic risks exceeding the limits for children are 37.04% and 40.74% respectively, and the proportion of carcinogenic risks exceeding the limit for adults is 11.11%. The top two heavy metal elements contributing the most to the ecological risks are Hg and Cd, while the ones to human health risks are Cr and As. The contents of MgO, Na2O, K2O, pH, Fe2O3, S, and P2O5, as well as the vegetation amount, slope aspect, and erosion degree, have a relatively significant impact on the potential heavy metal pollution and risks in the fully weathered layer and the semi-weathered layer. SIC, SOC, and S, as well as slope position and dip angle of the rock layer, have a relatively close relationship with the potential heavy metal pollution and risks in the weakly weathered layer.
      Conclusions Although the potential heavy metal pollution and risks of the weathered crust of black rock series are only moderate or light, however, factors such as extreme rainfall, land leveling for cultivation, and excavation and construction may cause huge-scale pollution and risk situations.

       

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