Application of assessment models for pollution and health risk from effluent discharge into a tropical stream: case study of Inyishi River, Southeastern Nigeria.

Pollution and health risk assessment models were used to study the effects of effluents discharged into the Inyishi River, Ikeduru LGA, Imo State, Nigeria. The study aims at investigating the environmental health effects of wastewater effluent discharge from the aluminum extrusion company on the Inyishi River. Samples were collected from both the aluminum extrusion company and Inyishi River and analyzed for physicochemical and trace metal parameters. Models adopted for assessment include transfer factor (TF), contamination factor (Cf), pollution load index (PLI), ecological risk factor (Er), water quality index (WQI), hazard quotient (HQ), and hazard index (HI). The results of the study revealed that pH and TH were within the Nigerian Standard for Drinking Water Quality (NSDWQ) and World Health Organization (WHO) standards. EC values at 2235 ± 0.001 and 105 ± 0.03 µS/cm for S3 and S4 respectively were higher than the permissible standards, while the values of EC at 24.04 ± 0.03, 5.26 ± 0.005, and 0.05 ± 0.01 µS/cm respectively for S1, S2, and SR are within the WHO standard. Very high concentration of SO42- was recorded at S3, while low concentration was measured at S2. Mean values of heavy metal ions studied were within NSDWQ and WHO standards for safe drinking water except for Al, Zn, Cd, Fe, and Mn, with the mean values of metal concentrations observed in the order Al > Fe > Zn > Mn > Cd > Cr. Positive linear correlation based on heavy metal contamination was observed for samples S1 and S2 with SR. High TF values were observed in decreasing order Mn > Cd > Cr > Fe > Zn. Similarly, very high CF was observed for Cd and Al while the PLI was generally high for all the samples. Low Er values were observed for all metals except for Cd, with the mean value of Er observed in the decreasing order Cd ˃ Mn ˃ Zn ˃ Cr. The river water sample generally revealed high WQI and was thus categorized as poor quality. HQ and HI values were below unity (< 1), but might pose health risk to children in cases of prolonged dermal adsorption. In conclusion, the quality of the Inyishi River has been negatively impacted by the wastewater effluent from the aluminum extrusion company. Proper treatment of the river water is therefore recommended before use for domestic purposes as prolonged usage of the untreated water might likely pose serious environmental health risks.

Environmental and health implications of trace metal concentrations in street dusts around some electronic repair workshops in Owerri, Southeastern Nigeria.

Assessment of trace metal concentrations in street-deposited sediments around some selected electronic repair workshops in Owerri, Imo State, Nigeria, was carried out. The objective of the study was to determine the concentrations of trace metals, namely nickel (Ni), chromium (Cr), lead (Pb), copper (Cu), cadmium (Cd), and zinc (Zn), in surface dusts from streets within some electronic repair workshops in Owerri, Imo State, Nigeria. Dust samples were collected from seven locations within the month of January 2014 during the dry season when the onset of dust was high in the area. The samples were air-dried, sieved, and digested in aqua regia, with the concentrations of trace metals determined with atomic absorption spectroscopy, Agilant FS 240AA model (USA). Results of the study revealed all the trace metals assessed except Cr in dust sample from Aladinma (ALA). Though elevated concentrations of Zn and Cu were observed in all the sampled locations, the concentrations did not exceed the Dutch intervention values. Risk assessment of the heavy metals showed high average daily dose (ADD) of the heavy metals for children and adults at New Market 2 (NMK2), New Market 1 (NMK1), and Tetlow (TEL), which could be attributed to the presence of electronic repair workshops and activities of electronic scrap dealers within these areas. It was observed that the values of hazard quotient (HQ) were less than 1, while that of hazard index (HI) were all below 1-5, indicating that the heavy metals pose no health risk to adults and children in the environment. However, there may be potential danger if the waste generated from the electronic repair workshops and electronic scrap dealers are not properly disposed and managed.