RESUMO
This research examined the bioremediation of pesticides (Carbofuran and Paraquat) contaminated farmyard soil using compost and Nitrogen, Phosphorus, and Potassium (NPK) fertilizer. Microcosms representing each treatment were set-up in triplicates. Biostimulation was done using two concentrations (0.5 % and 1.0 % w/w) of NPK fertilizer and compost, following pesticides application at recommended rates [Carbofuran (1 g/kg) and Paraquat (5 ml/kg)] and four times the recommended rates. Two control soils were set-up; Abiotic control (sterile farmyard soil + pesticide) and Control (farmyard soil without treatment). Monitoring of the dynamics in microbial community abundance, and pesticide residues during the biostimulation period was done weekly for 28 days, using standard enumeration method, and High Performance Liquid Chromatography (HPLC), respectively. At the end of the monitoring period, considerable reduction in pesticide residues across the treatment set-ups was recorded. In Carbofuran-treated soils, there were no complete, but considerable losses in residual pesticide, however, in most of the Paraquat-treated soils, there were complete losses within 21 days. Lower pesticide residues were recorded in set-ups amended with compost than NPK, across both Carbofuran and Paraquat-treated soils. After pesticides application, decreases in microbial counts were recorded at Day 7 across all the treatments, followed by increases from Day 14-21, then decreases at Day 28. Microbial counts were lower in Carbofuran than in Paraquat-treated soils irrespective of nutrient (compost and NPK) amendments. Bacterial and fungal counts were in the magnitude of 106 and 105 CFU/g soil, respectively. Also, increased counts were recorded for Actinomycetes, Nitrifiers, Phosphate solubilizers across all treatments, and were in magnitude of 103-104 CFU/g soil. Soil microorganisms could breakdown and eliminate large concentrations of Carbofuran and Paraquat in compost-amended soils than in NPK-amended soils. This study suggests that bioremediation of pesticides contaminated soils can be achieved and enhanced by stimulating the indigenous microbial community with requisite nutrients (compost).
RESUMO
This study investigated the bacteriological quality of ready-to-eat (RTE) African salads in Enugu metropolis, Enugu, Nigeria. A total of 10 samples of African salad were purchased from 10 different vendors in Enugu metropolis. The samples were purchased from Agbani Road, Ogbete, Mayor, Uwani, Kenyatta, Achara Layout, Obiagu and Timber. Isolation and enumeration of bacterial isolates were done using Nutrient agar, Eosin Methylene Blue (EMB) agar, Thiosulphate-citrate-bile salts-sucrose (TCBS) agar, Salmonella-Shigella Agar (SSA) and MacConkey agar, following standard methods. Identification of the bacterial isolates were done through biochemical tests and the Analytical Profile Index (API 20E) test kit. The antibiotic sensitivity of the bacterial isolates was also done using the Kirby Bauer disc diffusion method. Total culturable heterotrophic count was above 300 colonies across the samples. The highest bacterial counts recorded on EMB, SSA and TCBS across the samples were 6.3 × 106 CFU/g, 7.4 × 106 CFU/g and 1.21 × 107 CFU/g respectively. The identities of the organisms were; Salmonella spp., Staphylococcus aureus, Escherichia coli, Vibrio mimicus, Vibrio fluvialis, Vibrio cholerae, Vibrio parahaemolyticus and Vibrio hollisae. The prevalent organism across the samples was Vibrio spp. The antibiotic sensitivity test suggested that Vibrio spp. was resistant to Ampiclox and Amoxycillin but sensitive to Erythromycin, Pefloxacin and Septrin. From this study, it was discovered that consumers of RTE African salad from majority of the vendors across Enugu metropolis are at risk of severe food poisoning.
