Development and Evaluation of New Indices for Sediment-associated Contaminants.

New indices (modified hazard quotient, mHQ and ecological contamination index, ECI) are developed for evaluating sediment-associated heavy metals contamination. In evaluating the proposed indices, the concentration and chemical fractionation of five heavy metals (Cd, Cr, Cu, Ni and Pb) determined in benthic sediments from five tropical ecosystems off the Bight of Bonny were used to assess the degree of contamination and estimate the extent of anthropogenic inputs from industrial activities into these ecosystems. The analysis shows that the mean concentrations (mg/kg, dw) of Cd, Cr, Cu, Ni and Pb vary from 4.33 – 5.67, 11.12 – 28.52, 30.26 – 43.72, 2.02 – 2.60 and 162.0 – 190.37, respectively. An important observation is that the mean metal levels during the wet and dry seasons did not show significant variability at all sites. The spatial distribution and severity of sediment-associated contamination by heavy metals based on the developed indices (mHQ and ECI) are in the descending sequence: Cd>Pb>Cu>Cr>Ni. Hence, the observed trend is in good agreement with existing pollution indices. Contamination severity index, mean hazard quotients and modified risk assessment code are also used to identify the pollution hotspots, which reflect medium risk contamination ecological systems. Aquatic pollution indicators (potential contamination index, ECI, hazard quotients, and mHQ) reveal significant anthropogenic contamination of Cd and Pb in the sediments, while Cr, Cu and Ni show relatively low degree of contamination. PCI generally follows the sequence Cd>Pb>Cu>Cr>Ni. Principal component analysis (PCA) and factor analysis indicate that heavy metals in the benthic sediments originate mostly from anthropogenic sources

Evaluation of the Chemical Composition of Soil at E-waste Blazing Sites in Computer Village, Ikeja, Lagos, Nigeria

The evaluation of open blazing of electronic waste on the chemical composition of three different soil where e-waste were regularly being burnt with control samples at various distances away from each blazing site at computer village, Ikeja, Lagos, Nigeria was carried out using Atomic Absorption Spectroscopy. The mean concentrations of Pb, Cr, Zn, Cd and Cu from the three locations were found to be 120.3±0.4, 18.7±1.3, 90.3±0.4, 16.4±0.5 and 60.3±2.0 mg/kg respectively. There was gradual decrease in heavy metals concentrations at various distances away from each blazing site as the distances increase which suggested that there were leaching of these heavy metals from ewaste containing substances. Pearson correlation revealed that some of the heavy metals showed both positive and negative correlations with each other. When compared with standard values, only cadmium exceeded the tolerable limit recommended by European Union and USEPA. Thus, open blazing of e-waste contributed to the concentrations of these heavy metals in the soils

Carcinogenicity and Mutagenicity Assessments of Dietary Exposure to PAHs in Imported Fish Products in Nigeria.

Polycyclic aromatic hydrocarbons (PAHs) occurrence and assessment of dietary exposure from imported canned sardines (Sardinops sagax) commercially marketed in local stores and supermarkets in Nigeria were evaluated for the first time. PAHs determinations were performed using high performance liquid chromatography (HPLC) (Agilent 1290 model) equipped with UV-VIS diodes array detector (DAD) at λ =210 nm and 214 nm. The percentages recoveries were higher than 96%. The degree of contamination expressed as total concentrations of PAH (TPAHs) congeners ranged between 2.53 and 35.55 μg kg−1 dry weight (d.w.) at λ = 210 nm, and 1.30 and 27.93 μg kg−1 (d.w.) at λ = 214 nm. The carcinogenic (BaP-TEQ) and mutagenic toxicities (BaP-MEQ) of eight priority PAHs were evaluated. Benzo(a)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene and indeno(1,2,3-d) pyrene contributed significantly to the total carcinogenic equivalents of PAHs. The mutagenic equivalents were largely influenced by equivalence factors of benzo(a)anthracene, and benzo(a)pyrene and indeno(1,2,3-d) pyrene. The estimated daily intake (EDI) and excess cancer rate (ECR) were evaluated for adults and children exposure related risks

Geochemical Speciation and Risk Assessment of Trace Metals in Sediments from Coastal Ecosystems off Equatorial Atlantic Ocean

The concentrations of Cd, Cr, Cu, Ni and Pb in estuarine benthic sediments were determined through multistep speciation scheme to evaluate their spatio-temporal distributions, selective fraction magnitude, degree of contamination and potential ecological risks. The results indicated that the metal fractionation percentages in the residual, oxidizable and reducible fractions are the most significant, while the exchangeable and carbonates bound trace metals are relatively low. High mobility and bioavailability was indicated for Cu, Cr and Ni, while Cd and Pb in sediments present low bioavailability for biota. Contamination factor (CFm), degree of contamination (DC), modified degree of contamination (mCd), geoaccumulation index (Igeo), risk assessment code (RAC), and potential ecological risk index (PERI) were used to assess trace metals sedimentary pollution. The results indicate a prevalent moderate to high contamination of most trace metals analyzed. The contamination ranking of trace metals based on percent contribution to DC was Cd>Pb>Cu>Cr>Ni. RAC values indicate medium risk for Cd and Ni at all studied sites during the wet and dry seasons. Cd and Pb show moderate and very high individual metal potential ecological risk, respectively, while multi-elemental potential ecological risk indices (RIs) indicate very high ecological risk in all the ecosystem

New ecological risk indices for evaluating heavy metals contamination in aquatic sediment: A case study of the Gulf of Guinea

New indices – modified hazard quotient (m HQ) and ecological contamination index (ECI) – were developed for the evaluation of heavy metals contamination of sediment. Sequential extraction method was employed to determine the levels of cadmium (Cd), chromium (Cr), copper (Cu), nickel (Ni), and lead (Pb) in subtidal sediment samples from tropical ecosystems off the Gulf of Guinea. The results were used to assess the degree of contamination and estimate the extent of anthropogenic inputs from industrial activities. Results indicated that the concentrations of Cd, Cr, Cu, Ni and Pb ranged from 4.33 –5.67, 11.12– 28.52, 30.26–43.72, 2.02–2.60 and 162.0–190.37 mg/kg dw, respectively. The mean metal levels did not show significant variations among study sites during the wet and dry seasons. Spatial distribution and severity of sediment-associated contamination by heavy metals based on the newly developed indices (m HQ and ECI) were in good agreement with existing pollution indices and followed the descending sequence: Cd>Pb>Cu>Cr>Ni. Contamination severity index, mean hazard quotient and modified risk assessment code were also used to evaluate the sediment-heavy metal contamination, which generally indicated medium risk contamination of the investigated ecosystems. Aquatic pollution indicators (potential contamination index, ECI, hazard quotients, m HQ) revealed significant anthropogenic contamination by Cd and Pb, while Cr, Cu and Ni showed relatively low degree of contamination. Potential contamination index (PCI) generally followed the sequence Cd>Pb>Cu>Cr>Ni. A comparison of newly proposed indices with existing pollution indices revealed very good agreement. The contamination trends derived from the new indices were consistent and took into consideration site specificity, toxicity and a three-tier effect levels (threshold, mid-range and extreme effects guideline values) that support their reliability in evaluating contaminated aquatic ecosystems