Phytotoxicity, Bioload and Heavy Metal Evaluation of a Selected Municipal Dumpsite in Obosi, Anambra State, Nigeria

Abstract

Aims: To evaluate the pollution index of municipal solid waste dumpsite site located at Obosi metropolis of Anambra state, Nigeria. Study Design: Study of the dump site bioload level using sabouraud dextrose agar and nutrient agar, heavy metal determination using atomic absorption spectrophotometry and assessment of the ecological impact of the dump using two selected agricultural plants maize (Zea mays) and beans (Vicia faba). Place and Study Duration: Department of Applied Microbiology and Brewing Nnamdi Azikiwe University, PMB 5025, Awka, Anambra state, Nigeria between Februarys, 2014 to September, 2015. Methodology: Sample collection from two locations in Obosi, Nigeria, the dumpsite and sample collected 1.10 km away from the dumpsite was used as control, determination of the physicochemical characteristics of the two soils, microbial enumeration, chemical analysis and growing of plants (phytotoxicity assay). Results: Results showed that relatively alkaline pH was observed in the dumpsite soil (DSS) while slight acidity was reported in the control soil (CSS). The list of heavy metals and minerals quantified in this work via atomic absorption spectrophotometry (AAS) included mercury, lead, arsenic, cadmium zinc, chromium, aluminum, iron, manganese, magnesium, calcium, sodium  and potassium. The heavy metal concentration of dumpsite was higher than that of control. The microorganisms isolated from the present study included; Bacillus subtilis, Aspergillus candidus, and Aspergillus flavus.  In the phytotoxicity assessment, the maize grain and beans exhibited good germination conditions in CSS with an extremely poor germination performance in DSS due to heavy metal toxicity as well as alteration of other physicochemical status such as pH, texture and particle size configurations In general, seed germination performance was higher in the maize (Zea mays) than beans (Vicia faba) with germination indices of 89.7% and 51.2% respectively.  2:1 DSS and CSS soil modification gave the best germination. Statistical analysis showed that there was a significant difference in the percentage seed germination at p<0.05. Conclusion: Present study showed that Obosi dumpsite is polluted with heavy metals particularly mercury, chromium, lead and cadmium yielding very high in concentrations of heavy metals. If proper environment action is not carried out this will affect the surrounding agricultural soil and  jeopardize human health in the area.