Pollutants Co-occurring With Microcystins in Hypereutrophic Waters Used for Irrigation: A Case Study of the Crocodile West River Catchment

Abstract

Most urban water catchments are confronted with the challenges of eutrophication and other anthropogenic-related pollutants that can pose human health threats. To assess the suitability of using such anthropogenically polluted dam water for agricultural purposes the study monitored the co-existence of microcystins (MCs), metal pollutants, and anionic surfactants in irrigation canals and farm dams around Roodeplaat and Hartbeespoort Dams in South Africa. Field sampling was conducted four times between June 2019 and March 2021. The enzyme-linked immunosorbent assay (ELISA) method, a Hanna (HI96769) anionic surfactant portable photometer, and the inductively coupled plasma mass spectrometry (ICP-MS), were used to detect and quantify microcystins (MCs), anionic surfactants, and metals respectively. The results indicated that the water exceeded the guidelines for pH, EC, TDS, and nitrates. Eutrophication-related parameters such as MCs, chlorophyll a , and anionic surfactants were also relatively high. The Principal Component Analysis (PCA) showed the co-occurrence of MCs with EC, TDS, Pb, Cu, Al, and Ni in Hartbeespoort Dam-derived water, whereas pH and turbidity co-occurred with MCs in Roodeplaat Dam water. Such co-occurrences suggest that these parameters can be routinely monitored in place of MCs and this can be crucial in developing countries where resources and skilled manpower could be lacking.