Water hyacinth and duckweed as indicators of heavy metal pollution in River Asa. Journal of Industrial Pollution Control

Abstract

An investigation into the potentials of duckweed and water hyacinth as possible biomonitors of aquatic environment was carried out in River Asa. Water, duckweeds and water hyacinths were collected from six different locations along River Asa. The water and plant samples were analysed for physicochemical and heavy metal contents with standard methods. Result showed that temperature ranged from 25.35 to 31.20 °C. pH was high at site 1 and low at 5. Site 2 was more turbid (21.35 N.T.U.) and TSS range was 182.0 – 218.4 mg/L. BOD and COD ranges were 7.78 - 13.90 mg/L and 129.00 - 150.30 mg/L respectively. Dissolved O2, alkalinity and total hardness ranged between 12.00 and 20.32 mg/L, 5.41 and 16.90 mg/L, 12.90 and 14.40 mg/L respectively. Phosphate and nitrate levels ranged between 0.44 and 3.43 mg/L, 0.64 and 1.41 mg/L respectively. Of all the heavy metals in the plant tissues, Cd and Cr levels were highest. Except for Pb, no significant difference exists in heavy metal levels within the tissues of the two aquatic plants. The positive correlation of Cd, Cr, Ni and Pb levels in duckweed as well as those of Cd and Pb in water hyacinth to the levels in the river reflect the ability of the plants to monitor these metals. The study concluded that duckweed and water hyacinth could therefore serve as useful tools to monitor heavy metal pollution in rivers and other wetlands.