The interplay between temporal and seasonal distribution of heavy metals and physiochemical properties in Kaap River

Abstract

A key aspect of climate change is its impact on river water quality. Most research focuses on the impact of physiochemical parameters on water quality. However, the long-term shifts in temperatures and weather patterns coupled with anthropogenic activities play a significant role in river contamination. Metals are known to have toxic effects and environmental persistence. This study evaluated the heavy metal content of the Kaap River, where mining and agriculture are the primary land use. A 7-year study was conducted to investigate the seasonal relationship between heavy metals and physiochemical parameters (EC and pH). Fe, Al, As, and Mn concentrations were analysed in a laboratory accredited by the South African National Accreditation System (SANAS). The Python package Seaborn was used to generate heat maps for improved data visualization. Seasonal and temporal fluctuations had a combinatorial impact on Mn, Fe, and Al levels of the river. However, As levels were unaffected. The pH of the rivers was within the recommended range, despite flow regime, seasonal, and time-dependent fluctuations. Seasonal and temporal variations were also observed for EC, with the highest value of 42.35 mS/m being recorded during the winter of 2022, exceeding the recommended threshold of 30 mS/m. The correlation analysis revealed positive and significant correlations for the EC/pH and Al/Fe combinations and a weak degree of association for other parameters (P < 0.05). A permanent monitoring of water quality is required to ensure sustainable livelihoods and the safety of Kaap River water, which is subject to significant heavy metal fluctuations over time.