Interannual variation in metal concentrations in surface waters of the Marico River, South Africa

Abstract

This study was conducted to establish the interannual variation in the concentration of metals regarded as toxic to aquatic fauna in the Marico River of South Africa. Five surveys were conducted between 2013 and 2015 at six sites in the river. Water samples were collected and analysed for metals by means of ICP-MS, whereas pH was measured in situ. From these results it is evident that all the metals generally regarded as toxic to macroinvertebrates namely aluminium, titanium, chromium, manganese, iron, cobalt, nickel, copper, zinc, cadmium and lead, were detected at each of the sites, but not during every survey. Significant variations in the mean metal concentrations were demonstrated across all sites and surveys, with the intersurvey coefficient of variance exceeding 80% for all metals, except for Ti, Fe, Co and Ni. These results should be considered in defining the baseline metal concentrations of the Marico River.