ENVIRONMENTAL RISK ASSESSMENT OF HEAVY METALS LEACHING FROM AERATED LOGOON SEDIMENT

The use of sequential extraction method and the risk assessment code (RAC) provides valuable information and useful tools for assessing the potential mobility and environmental risks of heavy metals in the aerated lagoon sediment investigated in this study. Risk assessment code (RAC) is a method for risk assessment of heavy metals. It classifies the risk levels based on the chemical speciation of heavy metals. RAC determines the availability of heavy metals in sediments by applying a scale to the percentage of heavy metals in the exchangeable and carbonate fractions. According to Risk Assessment Code-values (RAC-values), Fe and V in sediment do not pose any risk to the aquatic environment at 0.4% and 0.8%, respectively. The RAC-values for Al, Co and S were correspondingly 1.8%, 9.5% and 6.2% which means that these heavy metals pose only a low risk to aquatic environment. The RAC-value for Ni was 12.5, which poses a medium risk. Only Ba and Mn in the sediment pose high risk with the RAC-value of 37.3% and 61.7%, respectively.