Evaluation of Bioaccumulation and Toxicity of Bisphenol-A and Phthalates on Earthworm and Nitrifying Bacteria from Soil Collected in Waste Management Landfill, Kaduna State, Nigeria

Abstract

Additives such as bisphenol-A (BPA) and phthalates are added to plastics during production processes in order to improve their properties. Since they are not covalently bound but simply mixed with the plastic polymer. They disperse easily in the environment, especially when plastic products are degraded into microplatics. Hence, the objective of this paper was to evaluate bioaccumulation and toxicity of bisphenol-A and phthalates on  earthworm (Apporrectoda ionga) and nitrifying bacteria from soil collected in Waste management landfill, Kaduna Sate, Nigeria using standard techniques. Data obtained shows that Bisphenol A, Diethytlphalate, Dimethylphthalate and Diethylhexylphalate were detected in the plastic enriched compositing soil while only bisphenol A was detected in the control soil sample. The physico-chemical analysis of the composted soil and the control had electrical conductivity 254.00, 61.00us/cm, chloride 66.15, 16.00mg/kg, potassium 171.5, 4.25mg/kg, nickel 1.00, 0.25mg/kg, Iron 17.40, 3.11mg/kg, Zinc 2.90, 0.67mg/kg, moisture 5.32, 7.21% total organic carbon 5.26, 0.71% and total nitrogen 0.52, 0.07% respectively. The bacteriological analysis for composted soil and control soil growth ranging from 4.0 x 10³+0.12 to 3.5x10³+10⁴cfu/g and 3.2x10³+0.4 to 2.8x10³+0.10 respectively. There was significant difference (p<0.05) in the bacteria counts from the control soil sample. The toxicity analysis revealed higher percentage utilization of nitrite with LC₅₀ values of 25.04, 23.93, 15.9 and 13.39 and higher bacteria inhibition with EC₅₀ values of 52.00, 81.72, 111.31 and 123.13. The results suggest that autotrophic transformation by nitrifying bacteria which enhances soil fertility may be hindered in an ecosystem polluted with these plasticizers as nitrification process will reduced. Percentage survival rate of earth worms decreased with increase in plastic concentration (75.47-20.93%).