Toxicity assessment of Olusosun and Igando leachates using the African catfish (<i>Clarias gariepinus</i>) as bioindicator species Part I

Abstract

Olusosun and Igando landfill leac ahates were investigated for their toxicity using Clarias gariepinus as the bioindicator species. Physical and chemical analyses of leachates showed that pH was generally basic (11.46; 10.15 respectively). The electrical conductivity, total dissolved solids, total hardness, chloride, nitrate and sulphate for Olusosun and Solous landfills leachates were found to have exceeded the WHO limits for drinking water. Heavy metals analyses showed that the concentration of nickel (75.5 ± 6.9 to 269.7 ± 1.33 μg/L), lead (74.7± 9.8 to 259.83 ± 8.3 μg/L), zinc (20 ± 7.5 to 198.2 ± 5.5 μg/L), cobalt (< detection limit to 12.1 ± 0.7 μg/L), cadmium (4.3 ± 0.6 to 4.7 ±0.2 μg/L) and copper (29.5 ± 1.3 to 220.3 ± 1.9 μg/L) were above the WHO (2007) recommended limits. Toxicity assessments carried out showed that the treatment level of 7.5 % was the least toxic to the fingerlings. The haematological results showed that Packed cell volume, Red Blood Cell count (1.5  9 9 ×10¹² /L, 1.85 x 10¹² /L), Haemoglobin (6.5 g/dL, 7 g/dL), White Blood Cell (10.95 ×10⁹/L, 13.5 x 10⁹/L), Heterophils (28.5 %, 38 %), Lymphocytes (70.5%, 62%), Eosinophils (0.5 %, 00 %), Basophils (0.5 %, 01 %) and Monocytes (00 % 00%) for Olusosun and Solous landfills leachates respectively were higher than in the control fish not exposed to leachate samples. Histopathological analyses of the fishes that survived the leachate exposures showed damage to the gills and liver of the fishes.

Keywords: Leachate, Landfill, Toxicity, Bio-indicator species