ASSESSMENT OF TRACE-METAL EXTRACTION TECHNIQUES WITH REFERENCE TO AQUATIC SEDIMENTS

Different techniques have been employed to determine the extractabilit y of non-residual metals from aquatic sediments. The methods classifie d as acid extractable, cold extractable and alkaline fusion extractabl e were compared on the basis of their efficiency in extracting metals responsible for pollution in streams and rivers in the Plateau state o f Nigeria. The results show that optimum recovery of any metal depends on the choice of the decomposition procedure. While the cold extracta ble method showed affinity for most of the metals, copper and tin were optimally recovered by the acid digestion method. Generally, fusion m ethods gave scant metal recoveries which could be attributed to the lo w silicate content of the sample and volatilisation losses. In all cas es the samples were quantitatively analysed by atomic absorption spect rophotometry and the error due to determination calculated as standard deviation.