Department of Ecology and Resource Management, University of Venda, Private Bag X5050, Thohoyandou, 0950, South Africa.
Department of Hydrology and Water Resources, University of Venda, Private Bag X5050, Thohoyandou, 0950, South Africa.
Environ Sci Pollut Res Int. 2021 Aug;28(31):42135-42149. doi: 10.1007/s11356-021-13703-1. Epub 2021 Apr 2.
To mitigate the negative environmental and public health concerns associated with increased industrial discharges amid the rapid industrial growth, sub-Saharan African countries have instituted several environmental regulations and policies. However, a paradox of good environmental policies but inadequate enforcement exists in most of these countries, with information on the pollution level unknown due to poor monitoring resources. In this study, potentially toxic heavy metal contamination and physicochemical characteristics in effluents and dumpsite soils of two tanneries in Kenya (DB) and South Africa (BO) were evaluated during the dry and rainy season of 2018. Pollution levels and ecological risk in the dumpsite soils were assessed by adopting geoaccumulation index (I), contamination factor (CF), pollution load index (PLI), and ecological risk index (PRI). The results showed that the mean final effluent concentration for total dissolved solids (TDS), chemical oxygen demand (COD), and Cr, Cu, Fe, Ni, Zn, and Cd for BO (2127, 890, 1.82, 1.38, 1.96, 0.60, 1.21, and 1.16, respectively) and DB tanneries (8157, 1369, 7.90, 0.69, 1.05, 0.60, 1.72 mg/L, respectively) were above the limits of emission guidelines. The mean Cr and Cr(VI) concentrations in tannery dumpsite soils (204.9 ± 29.1 and 0.31 ± 0.01 and 943 ± 29.8 and 0.4 ± 0.07 mg/kg for BO and DB, respectively) and Fe (2498 ± 62 mg/kg in DB) exceeded acceptable thresholds of the World Health Organization (WHO), Food and Agriculture Organization (FAO), and local background levels. A positive strong correlation was observed between Cr and organic matter, OM (r > 0.7, p < 0.001), electrical conductivity, EC (r = 0.99, p < 0.05), and As (r = 0.62; p < 0.05), suggesting a common anthropogenic point source. The mean PLI values of 5.3 and 1.6 for DB and BO dumpsites indicated significant pollution of the soils with heavy metals, specifically Cr (I = 18 and 2.4 for DB and BO, respectively). Similarly, PRI values of 174.8 and 57.4 indicated a moderate and low potential ecological risk for DB and BO tannery dumpsite, respectively, with several plants sampled within the two sites exhibiting elevated levels of Cr contamination. In summary, these results provide scientific insights on the need for both improved effluent management and treatment technologies of tannery wastes, coupled with the strengthening of continuous monitoring and enforcement for compliance of industrial discharges in sub-Saharan countries.
为缓解撒哈拉以南非洲国家在快速工业化进程中工业排放增加所带来的负面环境和公共卫生问题，这些国家制定了若干环境法规和政策。然而，大多数国家都存在一个矛盾，即环境政策良好，但执行不力，由于监测资源有限，对污染水平的信息一无所知。本研究于 2018 年旱季和雨季评估了肯尼亚（DB）和南非（BO）两家制革厂的废水和垃圾场土壤中潜在有毒重金属的污染情况和理化特性。采用地积累指数（I）、污染因子（CF）、污染负荷指数（PLI）和生态风险指数（PRI）评估了垃圾场土壤的污染水平和生态风险。结果表明，BO 制革厂废水总溶解固体（TDS）、化学需氧量（COD）和 Cr、Cu、Fe、Ni、Zn 和 Cd 的最终废水浓度平均值（分别为 2127、890、1.82、1.38、1.96、0.60、1.21 和 1.16）和 DB 制革厂（分别为 8157、1369、7.90、0.69、1.05、0.60、1.72 mg/L）均高于排放标准的限值。BO 和 DB 制革厂垃圾场土壤中 Cr 和 Cr(VI)的浓度平均值（分别为 204.9 ± 29.1 和 0.31 ± 0.01 以及 943 ± 29.8 和 0.4 ± 0.07 mg/kg）和 Fe（DB 为 2498 ± 62 mg/kg）均超过了世界卫生组织（WHO）、粮食及农业组织（FAO）和当地背景水平的可接受阈值。Cr 与有机质、OM（r > 0.7，p < 0.001）、电导率、EC（r = 0.99，p < 0.05）和 As（r = 0.62；p < 0.05）呈正强相关，表明存在共同的人为点源。DB 和 BO 垃圾场的平均 PLI 值分别为 5.3 和 1.6，表明重金属污染严重，特别是 Cr（DB 和 BO 的 I 值分别为 18 和 2.4）。同样，DB 和 BO 制革厂垃圾场的 PRI 值分别为 174.8 和 57.4，表明存在中度和低度潜在生态风险，两个地点内的一些采样植物显示出 Cr 污染水平升高。总之，这些结果为撒哈拉以南国家需要改进制革厂废水管理和处理技术以及加强对工业排放的持续监测和执法提供了科学依据，以确保合规。
