Ecological risk assessment of heavy metals and polycyclic aromatic hydrocarbons in sediments of rivers Niger and Benue confluence, Lokoja, Central Nigeria

Abstract

The concentrations of six heavy metals (HMs) and 16 US EPA priority polycyclic aromatic hydrocarbons (PAHs) in sediment samples of the confluence of rivers Niger and Benue were investigated. The ecological risk assessment of the contaminants was carried out. The results showed that the sediment samples were heavily polluted with iron and moderately polluted with Cd while other metals posed no pollution problem when compared with USEPA sediment quality guidelines. Only six out of the 16 priority PAHs were detected in the samples, and source apportionment of the PAHs indicated that they are of pyrogenic origin. The ∑PAHs in the samples were lower than many of similar studies and were of no pollution risk. The ecological risk assessment result of the heavy metals showed that the sediments were of considerable risk due majorly to Cd levels. The HM concentration results statistically showed significant difference between seasons at probability value (P < .05). Data analysis by PCA classified the metals into three different components according to sources. The levels of HMS and PAHs detected in the sediments were correlated for source identification, and the correlation showed that the majority of the pollutants were mainly from anthropogenic sources. There is increasing level of anthropogenic activities at the vicinity of the confluence due to urbanization which may call for periodic monitoring of the sediment quality.

Use of Chemical Indicators and Bioassays in Bottom Sediment Ecological Risk Assessment

“…According to this criterion, the sediment samples were classified as class II (moderately contaminated sediments) due to an elevated concentration of Cu (S2, S3), Cd (S1) and Ni (all stations). A relatively high concentration of Ni and Cd is a good indicator of a recent anthropogenic pollution (Ekere et al 2017 ). Nickel is commonly used in industry and it can be found at high concentration in freshwater areas surrounding developed urban areas (de Castro-Català et al 2016 ).…”

“…2 a). Strong positive correlations between individual pairs of heavy metals and PAHs indicate that they have a similar source and move together to the reservoir (Rinklebe and Shaheen 2014 ; Shaheen and Rinklebe 2014 ; Baran et al 2016 ; Ekere et al 2017 ). There are two main sources of PAH contaminations: petrogenic and pyrolytic.…”

“…The HMW PAHs contributed between 91 and 93% of the overall concentration of PAHs in the sediments, which implies the domination of pyrogenic sources. BAP often is used as an indicator for PAHs originating from combustion (Ekere et al 2017 ). In the study, a high correlation between BAP and other PAHs was found, which indicates that combustion is the primary sources of the PAHs (Fig.…”

“…The pollution of the aquatic environment by heavy metals and PAHs has been known as one of the most challenging pollution issues due to the toxicity, persistence, and bioaccumulation (Buruaem et al 2013 ; Fu et al 2014 ; Li et al 2015 ; Sukhdhane et al 2015 ; Wang et al 2016 ; Zhonghua et al 2016 ). Many authors found that the analysis of the concentration of heavy metals and PAHs in sediments could be used to investigate anthropogenic impacts on the aquatic environment and assess the ecological risk (Höss et al 2010 ; Buruaem et al 2013 ; Ekere et al 2017 ; Ezkwe and Utong 2017 ). Moreover, the chemical composition of bottom sediments is a good source of information about the human impact on the aquatic environment and an important indicator of the geochemical status in the river catchment (Roig et al 2015 ; Urbaniak et al 2015 ).…”

Content of nutrients, trace elements, and ecotoxicity of sediment cores from Rożnów reservoir (Southern Poland)

“…Deposit cores may be an excellent tool for the assessment of anthropogenic and natural impact on water environments (Harikumar and Nasir 2010; Wang et al 2012; Gao et al 2018). Bottom sediments absorb all pollutants due to their structure, which makes them a natural geosorbent where pollutants introduced to the aquatic environment accumulate (Förstner and Salomons 2010; Ekere et al 2017; Birch 2017). Moreover, their high ability to absorb and release dissolved substances causes the bottom sediments are key factor in nutrient recycling (Fafandel et al 2015).…”