Investigation of seasonal variation of groundwater quality in Jimeta-Yola area northeastern Nigeria

Seasonal variation of groundwater quality in Jimeta-Yola area was investigated using selected chemical contaminants. The results indicated that pollutant loading occurred in the dry and rainy seasons. The groundwater is fresh and varied from slightly acidic to alkaline in both the dry and rainy seasons. The mean values of BOD, COD and chloride exceeded the recommended standards of drinking water quality in the rainy season from the shallow and deep aquifers (hand-dug wells and boreholes). Nitrate and ammonium ion mean values in both seasons in shallow and deep aquifers exceeded the recommended limit of WHO. The mean coliform number counts exceeded the WHO recommended limit in both seasons in shallow and deep aquifers. The spatial distribution of EC and TDS reveal that the leachates from the dumpsites are significant source of groundwater contamination. The variation in contaminantdistribution is influenced by depth to water and well depth. There were increase in COD, BOD, nitrate, phosphate and chloride, and decrease in ammonium ion and coliform with water depth in shallow aquifer in the dry season, and COD, nitrate, ammonium ion, phosphate and chloride increase with water depth, and decrease in BOD and coliform in therainy season. COD, ammonium ion and chloride increase with well depth, and decrease in COD, BOD, nitrate, phosphate and coliform in deep aquifer in the dry season while COD, BOD, nitrate, ammonium ion, phosphate and chloride decrease in the rainy season. Coliform showed no depth control during the same period. In the dry season in leachate samples, contaminants revealed perfect correlation and nearly perfect correlation in the rainy season. The contaminants in all the aquifers revealed strong positive correlations in both seasons which are an indication of common source. Factor analysis indicates that groundwater chemistry is controlled by anthropogenic activities, salinity, ammonification and natural mineralization. It is recommended that safe waste disposal practice should be encouraged and drilling of boreholes to deeper levels is also suggested

Hydrochemical evolution of groundwater in Jimetayola area, northeastern Nigeria

Analytical results of thirty-seven water samples revealed that pH of the water samples ranged from acidic to alkaline throughout the sampling period. EC and TDS mean values were higher in the dry season in shallow aquifer and low in deep aquifer in the rainy season. This is an indication of the addition of leachable salts following the dissolution of waste materials in shallow aquifer. The low mean values of Ec and TDS in the case of deep aquifer is an indication of dilution effects due to recharging groundwater. The dominance of the cations in both seasons in shallow and deep aquifers was in the order of Na > Ca > K > Mg while the anions was in the order of Cl > HCO3 > NO3 > SO4 in both seasons in shallow aquifer and in deep aquifer in rainy season, and the anions was in the order of HCO3 >Cl>NO3> SO4 in the dry season in deep aquifer. The plots of log TDS against Na+ /(Na+ + Ca2+) indicated that most sample points plot in the region of rock dominance and weathering zone suggesting precipitation induced chemical weathering along with dissolution of rock forming minerals. Piper plots of the groundwater samples in the dry seasonin shallow aquifer classified the water types into Na-SO4-Cl, Ca-Mg-HCO3, Ca-Mg-SO4-Cl and Na-HCO3 water types while the sample plots indicated Na-SO4-Cl and Na-HCO3 water types in shallow aquifer in the rainy season. The plots of the samples indicated Na-HCO3, Ca-Mg-HCO3, Na-SO4-Cl and Ca-Mg-SO4-Cl water types in deep aquifer in both seasons. Cation exchange, salinisation and mixing processes were the processes  responsible for the chemical evolution of groundwater in the area. Organic decomposition, sewage effluent and house hold solid wastes were themajor sources of nitrate in the area. It is recommended that controlled waste disposal practice should be encouraged while drilling of productive boreholes to deeper levels is also encouraged