Metal stock solutions were made from reagent grade metal salts, namely copper sulphate (CuSO4.5H2O), zinc sulphate (ZnSO4.7H2O) and lead nitrate (Pb(NO3)2) mixed with deionised water (ASTM 2012). Stock solutions were analysed by Environmental Laboratory Services, Lower Hutt and were always within 96% recovery for copper, 105% for lead and 110% for zinc. Therefore, all concentrations reported in this study are nominal concentrations.