Assessment of the environmental impacts of marble quarrying on surface water at Kwakuti, Niger state, North Central Nigeria

Abstract

The determination of the impacts of marble quarrying on the surface water at Kwakuti was determined by assessing the physico-chemical properties of the water samples obtained from Kwakuti and its environs. The concentration of heavy metals, cations concentration, anions concentrations were determined in the laboratory. The values of the physical properties such as pH, electrical conductivity (EC), total dissolved solid (TDS) were immediately measured on the field. The average values for the concentration of heavy metals for the five locations sampled at Kwakuti are as follows; arsenic (As) (>0.01mg/l) which conforms to the World Health Organization (WHO) and Standard Organization of Nigerian (SON) standards of 0.01mg/l, cobalt (Co) was not detected in any of the five locations and zinc (Zn) with an average concentration of 0.30mg/l still lies within the allowable limits of 3.0mg/l proposed by the WHO. These were determined by the use of atomic absorption spectrophotometer (AAS) and as shown by these values, most of the heavy metals are below the maximum allowable concentrations of WHO and SON except for lead (Pb2+) which has an average concentration of 0.42mg/l which is higher than the maximum allowable concentration of 0.01mg/l which is higher than the acceptable limits of the WHO and SON. The mean concentration values of the cations are found to be as follows; calcium (Ca2+), 46.48mg/l; magnesium (Mg2+), 28.12mg/l and these values are higher than the WHO standard of 0.20mg/l. Sodium ( Na2+) has a mean value of 3.39mg/l which is an acceptable value compared to the WHO and SON standards of 200mg/l; potassium (K+) has an average concentration of 2.46mg/l and iron (Fe2+), 0.01mg/l as opposed to the Nigerian standards of 0.3mg/l. These values are all within acceptable limits except for the concentration of magnesium (Mg2+) which is quite higher than those of WHO and SON. The anions are all within the acceptable limits. Sulphate ion (SO42-) has an average value of 0.0094mg/l compared to the acceptable limits of 250mg/l while the bicarbonate ion (HCO3-) has an average value of 13.8mg/l. Nitrate ion (NO3-) has a mean concentration of 5.0mg/l well under the limits of 50mg/l, phosphate ion (PO42-) has a mean value of 0.025 and chlorite (Cl-) is at 22.33mg/l compared to the acceptable limits of 250mg/l. It was concluded that the major contaminants in the surface water at Kwakuti and its environs are mg2+ and pb2+. The effects of lead accumulation human health is well known and this has made the surface water in Kwakuti in no way suitable for the drinking either by humans or animals or even for other agricultural purposes such as irrigation due to high concentrations of Pb2+ and Mg2+ in the water and urgent steps should be taken to provide safe drinking water to the people in Kwakuti area.