ARSENIC POLLUTION OF THE SUBSURFACE WATER IN ONITSHA AND ENVIRONS, ANAMBRA STATE

ABSTRACT
This work investigates the extent of Arsenic pollution of borehole waters in Onitsha and environs. Fifteen samples of drinking water sourced from boreholes were randomly collected and analyzed using Atomic Absorption Spectrometry (AAS) and the technique employed is wet oxidation method. The results of Arsenic concentration obtained from the boreholes ranged from 0.00 mg/L (53.33% of boreholes) to 1.099mg/L (46.67% of boreholes). Seven out of the fifteen samples were observed to be concentrated with Arsenic ranging from 0.16mg/L to 1.099mg/L with majority of the concentrations occurring at areas adjacent to River Niger and Nwangene Lake. The results were found to be above the Maximum Contamination Level (MCL) of 0.01mg/L set by the World Health Organization (W.H.O, 2011) therefore, the sources were found to be contaminated with abnormal concentration of arsenic and the inhabitants who consume this water without proper treatment are vulnerable to severe health hazards. The high Arsenic concentrations in the study area could be attributed to both natural and anthropogenic processes such as improper discharge of untreated industrial effluents and sewage, urban storm runoff dissolving and leaching organic and inorganic matter into the subsurface ground, undersurface weathering, agro products, automobile workshops and emissions. The discharge of these effluents into water bodies leads to the bioaccumulation of heavy metals in fishes consequently, when humans feed on these aquatic organisms it results to serious health issues therefore, there is need for effluents to be treated before being discharged into the environment.