An Assessment of Heavy Metals Contamination in Freshwater Sediments and Fish and Cyanide in Sediment around Gold Ridge mine site, Solomon Islands

Abstract

Heavy metals in riverine sediments around Gold Ridge mine site ranged from 0.71 ± 0.09 to 726.73 ± 0.86 µg g−1. Out of all the metals that were investigated in the area, only arsenic metal claimed the highest concentrations for all sites within the area with values exceeding those of the WHO and EPA guidelines. The moderate type of contamination was shown for cyanide in sediments with values of 0 to 4.41 ± 0.35 µg g−1 which exceeded the WHO limit of 1µg g-1. The values of metals recorded for the two selected fish species Gobiidae, Belobranchus belobranchus and Rhyacichthys aspro ranged from under 0 to 2.59 ± 0.38 µg g−1. The use of these fish species as bio-indicators of heavy metal contamination in rivers around gold ridge proved them suitable to use as bio-indicators for future studies in the area. The sequential extraction of heavy metal in sediments indicated that most metals were present in the non-resistance fraction, a fraction that was readily available to move in the environment. Comparing the present study to the baseline study in the same area, indicated a simple % ration of, Cu (17%), Pb (78%), and Cr (54%), Cd (no data) and as (55%) were noted for all metals in the sediments. The present study confirms a significant increase of metals over years in rivers around the Gold Ridge mine site. The highest levels of metals and cyanide in riverine sediment around gold ridge mine site, compared to other Pacific studies, are attributed to the discharge of wastewater from the tailing dam in the area.