Seasonal evaluation of the hydrogeochemical interpretations of groundwater quality: a case study from automobile junk waste in Obosi and Onitsha environs, Southeast Nigeria

Automobile junk waste in Obosi and residence in housing estate in Anambra State, Southeast Nigeria, was studied for concern for human health. There is poor water quality for drinking, domestic and irrigation purposes. A seasonal study was conducted in the area for hydrogeochemical and microbial assessment for groundwater. To evaluate the release of the potentially toxic elements, 40 groundwater sources (borehole and hand-dug wells) were sampled. The groundwater was subjected to atomic absorption spectrometry and microbial methods. Particle size distributions for grain size analyses (for permeability) on the soils were conducted as a follow-up from previous study. Results show that the groundwater in the wet season (as a follow-up from dry season) is slightly acidic to neutral (6.04 to 6.54) when compared with the regulatory standards for drinking water. The heavy metal concentrations (in mg/L) in the groundwater included iron, chromium, zinc, nickel and lead that ranged from 0 to 0.73, 0 to 0.67, 0.52 to 6.45, 0 to 0.92 and 0 to 0.25 respectively. The microbial analysis in the groundwater recorded absent of faecal and lower counts of coliform (NTU) that ranged from 1.0 × 10 2 to 2.5 × 10 3 cfu/mL. The permeability K (in cm/s) is rated medium across the soils and ranged from 2.25 × 10 −2 to 4.41 × 10 −2 . Geochemical thermodynamic modelling (PHREEQC) predicts iron oxyhydroxide phases as responsible minerals precipitating in the system. Paired t test showed no significant difference on iron and nickel at wet and dry seasons while other heavy metals are statistically significant.