Net Flux of Heavy Metals Between Estuarine and Nearshore Environments: A Case Study of the Isipingo Estuary, KwaZulu-Natal, South Africa

This study examines the transport of seventeen heavy metals between the Isipingo Estuary and the adjacent sea. Results demonstrate variability of fluxes in terms of prevalence, concentration and seasonality. Summer neap and spring tides had approximately twice the number of heavy metals compared to winter and spring seasons. Spring and winter seasons yielded higher concentrations and a greater number of metals on the spring tides whilst autumn yielded the fewest metals on both tides. Export dominance characterized the system and this was evident in the annual fluxes with 14 metals (Al, As, Ba, Cr, Cu, Fe, Mn, Mo, Pb, Se, Sr, Ti, V and Zr) being exported while 3 (Cu, Ni and Zn) were imported into the estuary over the four seasons, pointing to potential contamination from marine sources. Whilst human utilization of the catchment is often reported as the primary cause of degradation of the Isipingo Estuary, this study demonstrates that some of the contamination may also originate from the nearshore environment.