Quantification of Metal Contaminants and Risk Assessment in Some Urban Watersheds

Adeleke Adeniyi,Mutiu Sowemimo,Olumuyiwa Okedeyi,Ojo Oluwole,Kafeelah Yusuf,Bernadine Ejiogu,Iyabode Ajibade,Olubunmi Adeniji,Goodluck Odili,Bamitale Fabiyi

doi:10.4236/jwarp.2020.1211056

Adeleke Adeniyi, Mutiu Sowemimo + Show 8 more

Open Access

https://doi.org/10.4236/jwarp.2020.1211056

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Abstract

Contamination by heavy metals is a serious threat to aquatic systems due to their level of toxicity at elevated levels. The pollution of urban watersheds is of particular concern because of its potential impact on the watershed ecosystem and the receiving larger water bodies. This study assessed the occurrence and distribution of cadmium, copper, nickel, lead and zinc in water and sediment samples collected from three urban watersheds in Lagos, Nigeria. The concentrations of metals were determined using atomic absorption spectrometry. The health risk index (HRI) of water usage was evaluated for both adults and children. HRI for cadmium and lead in some of the watersheds recorded HRI > 1 values, a cause for health concern. The pH of water ranged from 6.48 ± 0.28 - 6.54 ± 0.47 (2016) and 6.18 ± 0.56 - 6.53 ± 0.17 (2018) respectively while, for sediments, the pH values ranged from 6.14 ± 0.48 - 6.9 ± 0.15 and 5.38 ± 0.22 - 6.4 ± 0.38 for 2016 and 2018 respectively. The levels of metals in the water samples during the 2016 sampling cycle were found to be within the World Health Organization (WHO) guideline limits for drinking water. However, the 2018 cadmium, lead and zinc concentrations for Ira-Ipaye and Akesan watersheds exceed the WHO guideline limits. Cadmium was not detected in Ira-Ipaye and Akesan 2016 sediment samples. Statistical t-test and analysis of variance (ANOVA) were used to ascertain significant differences of metals concentration in the three watersheds. The pH and metal concentration values obtained for water and sediment for the year 2016 and 2018 were non-significantly different.

Highlights

Watersheds are important in the study and management of environmental water resources [1] [2] [3] [4]
Studies have shown that atmospheric deposition, vehicular transportation-related activities and metallic building envelopes resulting from agricultural, domestic and industrial activities are among the major pollution sources of urban watersheds [7] [8]
The aim of this study was to evaluate the occurrence and distribution of cadmium, copper, nickel, lead and zinc in water and sediment samples of three urban watersheds; with a view to determine the extent of metal pollution exacerbation over the two-year period, 2016 to 2018, the health risk indices would be evaluated

Summary

Introduction

Watersheds are important in the study and management of environmental water resources [1] [2] [3] [4]. Studies have shown that atmospheric deposition, vehicular transportation-related activities and metallic building envelopes resulting from agricultural, domestic and industrial activities are among the major pollution sources of urban watersheds [7] [8]. The partitioning of sources is further complicated by source interactions [9]. The fate of these metal pollutants in the biological systems is known to be influenced by dissolved organic matter [10] [11] [12]. Pollution sources should be more closely controlled and monitored for the purposes of enhanced water quality and ecological conservation [7] [14] [15] [16]

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