Assessment of Toxic Metals and Anionic Surfactants in Agricultural Soils, Crocodile River Catchment
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Increasing levels of toxic metals and surfactants in soils due to rapid urbanisation, industrialisation, intensive agriculture, and mining have led to environmental and human health concerns. In developing countries, agricultural soils are particularly vulnerable to contamination due to poor irrigation practices and effluent discharge. This study aimed to assess the levels of potentially toxic metals and anionic surfactants in agricultural soils around the Roodeplaat and Hartbeespoort Dams in the Crocodile River (West) Catchment, South Africa. Soil and water samples were collected from four agricultural sites and three control sites between June 2019 and March 2020. Soil samples were first digested using aqua regia digestion then analyzed using ICP-MS and ICP-AES. The methylene blue active substances (MBAS) assay was used to determine anionic surfactants. Data analysis involved Principal Component Analysis (PCA), the Geo-accumulation Index (Igeo), and Pearson correlation. The findings indicated that metals such as Cr, Fe, As, Pb, and Ni were above the regulatory limits. The Igeo values pointed to moderate to heavy anthropogenic contamination. Anionic surfactants were reported in all the soil samples, but they did not correlate with any of the metals. Contamination patterns between the two study sites could be differentiated by PCA, highlighting potential contamination from anthropogenic sources. Based on the findings, it was concluded that irrigation with polluted dam water was severely compromising the soil quality and raising concerns over crop safety and ecosystem health. Future studies will need to assess the levels of metals in the cultivated crops to investigate risks in the food chain.
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