An analysis of the distribution and chemical forms of selected metals: cadmium (Cd), chromium (Cr... more An analysis of the distribution and chemical forms of selected metals: cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni) and lead (Pb) in subtidal sediments of Qua Iboe Estuary and adjourning creeks, collected between June 2000 and January 2001, were studied using a sequential chemical extraction method. The concentration of metals in each extracted fraction was determined using inductively coupled plasma spectrometer (ICP-AES). Pb, Cd and Cu appear to be the most abundant metal in the sediments of the systems, and are predominantly associated with the residual, organic and oxidisable phases. Results indicate that there are also insignificant components that are bound to both the exchangeable and carbonates fractions. Ni is largely associated with bioavailable phases with insignificant bound to organic matter and residual fractions. In general, an insignificant component of Cd and Pb are bound to organic matter phase. Moreover, speciation results indicate that metal contamination in the ecosystems investigated primarily comes from human-mediated sources. Thus, based on index of geoaccumulation calculated, sediments of these ecosystems have been classified as uncontaminated by Cr, Cu and Ni, strongly contaminated by Pb and extremely contaminated by Cd.
We present a seasonal and baseline survey of selected physicochemical parameters in epipelagic sa... more We present a seasonal and baseline survey of selected physicochemical parameters in epipelagic samples from Qua Iboe (QIB) and Cross River (CRV) estuaries in Niger Delta region of Nigeria. The parameters analysed were temperature, pH, salinity, turbidity, total suspended solids (TSS), dissolved oxygen (DO), biochemical oxygen demand (BOD), total organic carbon (TOC), total nitrogen, available phosphorus, Ca2 + , Mg2 + , Na + , K + (exchangeable cations) and \({\rm SO}_{4}^{2-}\) , Cl − , \({\rm NH}_{4}^{+}\) and \({\rm NO}_{3}^{-}\) . The results showed that the physicochemical parameters exhibited spatiotemporally explicit variabilities. The mean levels of the parameters were higher during the wet season (June–September) except salinity, DO, Cl − and \({\rm NH}_{4}^{+}\) in CRV, whilst QIB recorded higher mean levels for temperature, pH, salinity, BOD, TOC, \({\rm SO}_{4}^{2-}\) , Cl − and \({\rm NH}_{4}^{+}\) during the dry season (November–February). Significant seasonal variability was recorded for salinity, DO, turbidity, TSS, \({\rm SO}_{4}^{2-}\) and \({\rm NH}_{4}^{+}\) levels in CRV and for turbidity, DO, BOD, TSS, TOC, available P, Na, Cl − and \({\rm NO}_{3}^{-}\) levels in QIB. This study confirmed that the degree of variability of the various physicochemical surface water quality indicators is dependent on the prevalent environmental estuarine factors.
Inter-seasonal studies on the trace metal load of surface water, sediment and Tympanotonus fuscat... more Inter-seasonal studies on the trace metal load of surface water, sediment and Tympanotonus fuscatus var. radula of Iko River were conducted between 2003 and 2004. The impact of anthropogenic activities especially industrial effluent, petroleum related wastes, gas flare and episodic oil spills on the ecosystem are remarkable. Trace metals analyzed included cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), nickel (Ni), vanadium (V) and zinc (Zn). Sediment particle size analysis revealed that they were characteristically psammitic and were predominantly of medium to fine grained sand (>73%), less of silt (−1), Cr (0.22 ± 0.12 mg kg−1), Cd (0.05 ± 0.03 mg kg−1), Cu (0.04 ± 0.02 mg kg−1) and Mn (0.23 ± 0.22 mg kg−1) in the sediment samples. This observation is consistent with the scarcity of clayey materials known to be good scavengers for metallic and organic contaminants. Sediments indicated enhanced concentration of Fe, Ni and V, while other metal levels were relatively low. The concentrations of all the metals except Pb in surface water were within the permissible levels, suggesting that the petroleum contaminants had minimal effect on the state of pollution by trace metals in Iko River. Notably, the pollutant concentrations in the sediments were markedly higher than the corresponding concentrations in surface water and T. fuscatus tissues, and decreased with distance from point sources of pollution.
An analysis of the distribution and chemical forms of selected metals: cadmium (Cd), chromium (Cr... more An analysis of the distribution and chemical forms of selected metals: cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni) and lead (Pb) in subtidal sediments of Qua Iboe Estuary and adjourning creeks, collected between June 2000 and January 2001, were studied using a sequential chemical extraction method. The concentration of metals in each extracted fraction was determined using inductively coupled plasma spectrometer (ICP-AES). Pb, Cd and Cu appear to be the most abundant metal in the sediments of the systems, and are predominantly associated with the residual, organic and oxidisable phases. Results indicate that there are also insignificant components that are bound to both the exchangeable and carbonates fractions. Ni is largely associated with bioavailable phases with insignificant bound to organic matter and residual fractions. In general, an insignificant component of Cd and Pb are bound to organic matter phase. Moreover, speciation results indicate that metal contamination in the ecosystems investigated primarily comes from human-mediated sources. Thus, based on index of geoaccumulation calculated, sediments of these ecosystems have been classified as uncontaminated by Cr, Cu and Ni, strongly contaminated by Pb and extremely contaminated by Cd.
We present a seasonal and baseline survey of selected physicochemical parameters in epipelagic sa... more We present a seasonal and baseline survey of selected physicochemical parameters in epipelagic samples from Qua Iboe (QIB) and Cross River (CRV) estuaries in Niger Delta region of Nigeria. The parameters analysed were temperature, pH, salinity, turbidity, total suspended solids (TSS), dissolved oxygen (DO), biochemical oxygen demand (BOD), total organic carbon (TOC), total nitrogen, available phosphorus, Ca2 + , Mg2 + , Na + , K + (exchangeable cations) and \({\rm SO}_{4}^{2-}\) , Cl − , \({\rm NH}_{4}^{+}\) and \({\rm NO}_{3}^{-}\) . The results showed that the physicochemical parameters exhibited spatiotemporally explicit variabilities. The mean levels of the parameters were higher during the wet season (June–September) except salinity, DO, Cl − and \({\rm NH}_{4}^{+}\) in CRV, whilst QIB recorded higher mean levels for temperature, pH, salinity, BOD, TOC, \({\rm SO}_{4}^{2-}\) , Cl − and \({\rm NH}_{4}^{+}\) during the dry season (November–February). Significant seasonal variability was recorded for salinity, DO, turbidity, TSS, \({\rm SO}_{4}^{2-}\) and \({\rm NH}_{4}^{+}\) levels in CRV and for turbidity, DO, BOD, TSS, TOC, available P, Na, Cl − and \({\rm NO}_{3}^{-}\) levels in QIB. This study confirmed that the degree of variability of the various physicochemical surface water quality indicators is dependent on the prevalent environmental estuarine factors.
Inter-seasonal studies on the trace metal load of surface water, sediment and Tympanotonus fuscat... more Inter-seasonal studies on the trace metal load of surface water, sediment and Tympanotonus fuscatus var. radula of Iko River were conducted between 2003 and 2004. The impact of anthropogenic activities especially industrial effluent, petroleum related wastes, gas flare and episodic oil spills on the ecosystem are remarkable. Trace metals analyzed included cadmium (Cd), chromium (Cr), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), nickel (Ni), vanadium (V) and zinc (Zn). Sediment particle size analysis revealed that they were characteristically psammitic and were predominantly of medium to fine grained sand (>73%), less of silt (−1), Cr (0.22 ± 0.12 mg kg−1), Cd (0.05 ± 0.03 mg kg−1), Cu (0.04 ± 0.02 mg kg−1) and Mn (0.23 ± 0.22 mg kg−1) in the sediment samples. This observation is consistent with the scarcity of clayey materials known to be good scavengers for metallic and organic contaminants. Sediments indicated enhanced concentration of Fe, Ni and V, while other metal levels were relatively low. The concentrations of all the metals except Pb in surface water were within the permissible levels, suggesting that the petroleum contaminants had minimal effect on the state of pollution by trace metals in Iko River. Notably, the pollutant concentrations in the sediments were markedly higher than the corresponding concentrations in surface water and T. fuscatus tissues, and decreased with distance from point sources of pollution.
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