Analysis of Heavy Metal Content in Water hyacinth (Eichhornia crassipes) from Lake Victoria, Kenya

Abstract

A study was conducted to determine the concentration ofheavy metals in E. crassipes along the shoreline of Winam Gulf on Lake Victoria, Kenya. Sampling from the Cereals Board, to Kiboko Bay was conducted between 18th May, 2013 and 31st August, 2013 based on the growth of fresh water hyacinth. Plants were harvested whole, washed twice with tap water and once with distilled water then weighed. The leaves, stems and roots were separated using stainless steel cutters and weighed. Simultaneously, water samples were also harvested and later filtered of algae and sediments before storage. Plant samples were dried under room temperature for two weeks followed by overnight oven drying at 1050c. They were then ground using an electric grinder. Dry ashing on 2g of powdered plant material was conducted at 6000c in a furnace for 4hrs.For water samples, 5ml was measured and dry ashed for 2hrs. The ash was then digested in 5ml of concentrated nitric acid and made to 100ml with distilled water. The digested samples were then analyzed for eight metals. Pb2+, Fe2+, Cu 2+, Zn2+, Mn2+ , Cr2+ , Cd2+and Ni2+ were detected in the samples with concentrations ranging from 0.02≤ 21ppm of dry mass. Concentration of some metals in roots was found to be up to 3 times higher than in leaves and stems. Fe2+ and Mn2+ were the highest recorded at 21 and 16 ppm of dry weight, respectively. The study shows that water hyacinth can be used as an indicator for pollution. It can also be utilized for water purification due to its high metal intake capacity.