Effects of Spent Industrial Calcium Carbide on Soil Microbial and Physicochemical Properties

Abstract

The effects of different concentrations of spent calcium carbide on soil microbial and physiochemical properties were studied using standard microbiological and biochemical techniques. Soils were contaminated with varying concentrations (5 g/kg, 25 g/kg, 50 g/kg, 100 g/kg, 200 g/kg, and 400 g/kg) of spent carbide with the control having 0 g/kg of spent carbide. The effects of spent carbide were monitored weekly for four (04) weeks. Soil pH varied from 6.10±0.00 to 12.40±0.01. Total nitrogen, organic carbon, phosphorus and moisture ranged from 0.02±0.00 to 0.23±0.02 %, 9.16±0.05 to 48.76±1.00 %, 11.30±0.05 to 31.11±0.60 % and 2.88±0.06 to .91±0.20 % respectively. Cation exchange capacity (CEC) increased from 1.53±0.01 to 5.03±0.30 meq/100g and electrical conductivity (EC) from 36.5±1.05 to 390.2±3.00 μs/cm. The bacterial isolates which survived the harsh spent calcium carbide waste at 400 g/kg after 4 weeks include Bacillus subtilis, Acinetobacter calcoaceticus, Pseudomonas putida, Micrococcus luteus and Bacillus pumilis while the fungal isolates include Penicillium chrysogenum, Aspergillus niger and Rhizopus stolonifer. The total viable bacterial count decreased from 4.27×10 5 ±17.0 to 1.99×10 3 ±22.0 cfu/g and the fungi from 2.04×10 4 ±18.0 to 2.19×10 2 ±21.0 cfu/g after 4 weeks. Spent carbide waste is mainly composed of calcium oxide (Ca0) which constitute about 44.99±1.50 % of the waste. The most abundant heavy metal in the waste was zinc with a concentration of 10.11±0.62 mg/kg and the least was mercury (0.01±0.00 mg/kg). The results obtained in the study revealed that spent calcium carbide had adverse impact on both soil physiochemical and microbial numbers.