Seasonal variation of physicochemical parameters of groundwater in sandstone – shale – intrusive aquifers in part of Mamfe embayment southeastern Nigeria. – A. N. Ugbaja, A. E. Edet and O. E. Offiong and T.N. Nganje
Water samples were collected from twenty two (22) locations in the Embayment across the periods of dry (January), dry-wet (March), wet (June), wet-dry (September), to highlight the micro-climatic conditions between January to September 2005. The main objectives of this work were to carry out hydrogeochemical studies and assessment of the sandstone – shale – intrusive aquifers in part of Mamfe embayment South Eastern Nigeria and evaluate the seasonal variation of groundwater and asses the contamination of the aquifers using Anion, Cation, NO3 and Coliform to assess the contamination of the aquifer and identify source of the contaminant. In this study, the relationship between various elements has been studied using physico-chemical/ biological parameters. The data in the stiff diagram shows variation of Anion, Cation in the three different formations with the micro seasonal period of dry, dry-wet, wet and wet-dry. In intrusive there was an increase of Bicarbonate and Magnesium in the dry-wet period and a reduction of the same element as the rain intensify, an indication of dilution while there was an increase of bicarbonate in the dry-wet period showing precipitation. In Asu-River Group, bicarbonate and Magnesium decreases in dry-wet period but rather increase it quantity during the wet period while Na+K was deceasing and this may be due to precipitation of carbonate and leaching of Na+k which continued after wet period into dry-wet period. In Eze-Aku Formation, there was an increase of Ca+ and Mg+ in the dry-wet period and a drastic reduction of Ca+ in wet period. Bicarbonate was being reduced as the period move from dry period to wet-dry period; this is due to rock type (sandstone) which helps in high infiltration of runoff. The data also show that the formations were more contaminated in the wet period in some areas than dry period while in some areas the wet period reduces the contamination due to dilution from runoff and this is evidence that the contamination of the study area is control by infiltration and runoff. And these goes further to show that the aquifers in the study area are mostly recharged by precipitation. The data also prove that the aquifers in the study area are not contaminated by nitrate, but are rather contaminated by faecal coliform due to water from runoff that infiltrate into the aquifer from the vodoze zone during precipitation in the area.