Godwin E. Nwajei

Chemical fractionation of some heavy metals in soil profiles in vicinity of scrap dumps in Warri, Nigeria.

Abstract The lability of Cr, Ni, Pb, Fe, Mn, Cd and Cu in soils contaminated by scrap dumps in Warri, Nigeria was assessed by a sequential chemical extraction procedure (SCE) to fractionate the metals into MgCl2extractable fraction, Na-acetate extractable fraction, hydroxylamine hydrochloride extractable fraction, HNO3/H2O2 extractable fraction and HF/aqua-regia extractable fraction. The results indicate that Pb is associated with HF/aqua-regia and hydroxylamine hydrochloride extracted fraction. Copper and chromium was associated with HNO3/H2O2 and HF/aqua-regia extracted fractions. Cd, Mn and Fe were associated with HF/aqua-regia and hydroxylamine hydrochloride extracted fractions. However, in some sites up to 45% of Cd was found in the MgCl2 and Na-acetate extracted fractions. The metals associated with hydroxylamine hydrochloride and HNO3/H2O2 extractable fractions may be available to the biota when the pH and the redox potential of the soil changes. Data presented provides information on the lability of metals in soil profiles in the vicinity of scrap dumps.

Polycyclic aromatic hydrocarbon concentrations in commercially available infant formulae in Nigeria: Estimation of dietary intakes and risk assessment

The concentrations and profiles of polycyclic aromatic hydrocarbons (PAHs) in commercially available infant formulae and follow-up formulae in Nigeria were determined with a view to providing information on the health risks to children from the consumption of these infant foods. The concentrations of PAHs were measured by means of gas chromatography-mass spectrometry (GC-MS) after extraction by ultrasonication with acetone/dichloromethane and clean-up. The concentrations of the Σ16 PAHs in these infant formulae ranged from 0.102 to 1.98 μg kg(-1), 0.054-1.98 μg kg(-1), 0.081-2.54 μg kg(-1) and 0.51-0.70 μg kg(-1) for infants of ages 0-6 months, 6-12 months, 1-3 years and 0-12 months respectively. The concentrations of benzo(a)pyrene (BaP) in all samples investigated were below the 1 μg kg(-1) European Commission permissible limit for BaP in foods meant for infants. The estimated daily intake of PAHs based on the European Food Safety Authority (EFSA) suggested indicators of occurrence and effects of PAHs in foods were not detected (nd) to 2.67 ng BaP kg(-1) bw day(-1), nd-5.29 ng PAH2 kg(-1) bw day(-1), nd-11.20 ngPAH4 kg(-1) bw day(-1) and nd-34.96 ng PAH8 kg(-1) bw day(-1). The estimated margin of exposure (MOE) values: BaP-MOE, PAH2-MOE, PAH4-MOE and PAH8-MOE values were greater than 10,000 which indicates that there are no health risks from the consumption of these products by infants. The concentrations and dietary exposure to PAHs from these products were similar to values reported in the literature for European Communities.

Impact of Land-Use Patterns on Chemical Properties of Trace Elements in Soils of Rural, Semi-Urban, and Urban Zones of the Niger Delta, Nigeria

The study of the concentrations of Cr, Zn, Cd, Pb, Ni, and Cu in soils under different land uses in rural, semi-urban, and urban zones in the Niger Delta was carried out with a view to providing information on the effects of the different land uses on the concentrations of trace elements in soils. Our results indicate significant variability in concentrations of these metals in soils under different land uses in rural, semi-urban, and urban zones. The maximum concentrations of metals in the examined soil samples were 707.5 mg.kg−1, 161.0 mg.kg−1, 2.6 mg.kg−1, 59.6 mg.kg−1, 1061.3 mg.kg−1, and 189.2 mg.kg−1 for Cr, Zn, Cd, Pb, Ni, and Cu, respectively. In the rural zone, the cassava processing mill is a potent source of Ni, Cr, Cu, and Zn while agricultural activities are a source of Cd, and automobile emissions and the use of lead oxide batteries constitute the major sources of Pb. In the urban zone, soils around the wood processing mill showed elevated concentrations of Cu, Cr, Zn, and Ni, while soils around automobile mechanic works and motor parks showed elevated levels of Pb. Elevated Cd concentrations were observed in soils under the following land uses: urban motor park, playground, welding and fabrication sheds, and metallic scrap dump. The contamination/pollution index of metals in the soil follows the order: Ni > Cd > Cr > Zn > Cu > Pb. The multiple pollution index of metals at different sites were greater than 1, indicating that these soils fit into “slight pollution” to “excessive pollution” ranges with significant contributions from Cr, Zn, Cd, Ni, and Cu.

Survey of trace element composition of commercial infant formulas in the Nigerian market

Concentrations of zinc (Zn), copper (Cu), cadmium (Cd), lead (Pb), iron (Fe), nickel (Ni), chromium (Cr), vanadium (V) and cobalt (Co) were measured in 190 samples covering 19 different brands of popular baby foods in Nigeria to assess whether the intakes complied with the recommended desired levels for essential metals and permissible levels for toxic elements. The mean concentrations of Zn, Cu, Cd, Pb, Fe, Ni, Cr, V and Co in different types of infant foods were found to vary from 1.8–7.8; <0.001–0.1; <0.001–0.02; 0.01–0.1; 4.4–25.8; 0.03–0.06; 0.1–1.6; <0.001–0.1 to <0.001–0.1 µg g−1, respectively. The average concentrations of these metals were higher in soy-based formulas than milk-based infant foods. The estimated average daily intakes of metals through the consumption of these brands of infant foods for ages 0–6 and 7–12 months were 118.6 and 163.5; 1.0 and 1.9; 0.2 and 0.3; 1.3 and 1.8; 294.8 and 530.6; 1.0 and 1.1; 15.1 and 20.6; and 0.8 and 4.0 µg kg−1 body weight (bw) day−1 for Zn, Cu, Pb, Cd, Fe, Ni, Cr and Co, respectively. The daily intakes of non-essential elements of these metals through baby foods are well below the recommended tolerable levels. Similarly, the daily intake levels of essential elements (e.g. Zn, Co, Cu and Fe) were also significantly lower than the recommended desirable levels in infant foods.

Concentrations and Distribution of Trace Metals in Water and Streambed Sediments of Orogodo River, Southern Nigeria

The distribution of Cd, Pb, Ni, Cr, Cu, Mn, Fe, and Zn in sediment and surface water, and some physico-chemical characteristics of Orogodo river sediments, were evaluated. The sediment pH ranged from 5.1–7.3; conductivity values ranged from 34.5 to 389.0 μScm−1. Total nitrogen values ranged from 0.06–0.10%, NH3-N values ranged from 0.25–0.44 mgkg−1, percent total organic carbon ranged from 0.21–1.68%, and total phosphorus values ranged from 0.004–0.02% for dry and wet seasons. The sand fraction consists of 87–95%, silt fractions ranged from 0–2%, and clay fraction between 4–13%. The mean concentrations of metals (dry weight basis) in the streambed sediments ranged from 1.92–17.37 mgkg−1 for Cu, 0.98–4.78 mgkg−1 for Ni, 0.01–32.98 mgkg−1 for Mn, 353.22–2045.64 mgkg−1 for Fe, 69.96–100.16 mgkg−1 for Zn, 0.21–1.32 mgkg−1 for Cr, and Cd was less than 0.001 mgkg−1 for wet and dry seasons. The mean concentrations of metals in the surface water ranged between 0.01–0.05–0.05 mg/L for Cu, nd-0.11 mg/L for Ni, 0.001–0.31 mg/L for Pb, 0.001–1.82 mg/L Mn, 0.01–3.52 mg/L for Fe, 0.16–0.61 mg/L for Zn, nd-0.007 mg/L for Cr, and <0.001 mg/L for Cd. Based on principal component analysis, two main sources of metals in the Orogodo River can be identified: (i) Cr, Cu, Pb, and Fe are mainly derived from industrial sources; (ii) Mn, Zn, and Ni associated with traffic activities. No element examined had a contamination/pollution index value greater than unity (pollution ranges). This implies that the multiple pollution indices obtained from the analysis showed that Orogodo River sediments were not polluted with heavy metals.

Concentrations and Profiles of Polycyclic Aromatic Hydrocarbons in Some Commercial Brands of Tea-, Coffee-, and Cocoa-Based Food Drinks in Nigeria

Concentrations and profiles of polycyclic aromatic hydrocarbons were determined in some popular commercial brands of tea-, coffee-, and cocoa-based food drinks in Nigeria by gas chromatograph-flame ionization after hexane/dichloromethane extraction and clean up. The concentrations of the ∑16 Polycyclic aromatic hydrocarbons in these products ranged from 5.2–913.1, 38.7–593.1, and 38.0–1406.4 μg kg−1 for tea-, coffee-, and cocoa-based food drinks, respectively. The polycyclic aromatic hydrocarbon profiles indicate the dominance of three and four rings PAHs in these food items. The concentrations of the European Food Safety Authority (EFSA) eight carcinogenic polycyclic aromatic hydrocarbons ranged from nd–218.9, nd–102.9, and nd–1248.5 μg kg−1 for tea-, coffee-, and cocoa-based food drinks, respectively.

Concentrations and Health Risk of Polycyclic Aromatic Hydrocarbons in Some Brands of Biscuits in the Nigerian Market

ABSTRACT Concentrations of 16 priority polycyclic aromatic hydrocarbons (PAHs) were determined in 40 brands of biscuits in the Nigerian market. The analyses were performed by gas chromatography-flame ionisation detection (GC-FID) after Soxhlet extraction of the sample with hexane/dichloromethane and clean-up of the extract. The concentrations of Σ16 PAHs in these biscuit samples were in the range of 35.7–645.3 μg kg−1, 75.9–490.7 μg kg−1, 91.5–537 μg kg−1, 18.4–522.2 μg kg−1, 123.5–393.8 μg kg−1, 167.2–880 μg kg−1, 136.5–316 μg kg−1, and 135.5–241.6 μg kg−1 for shortcake, digestives, cookies, shortbread, wafers, crackers, Pringles, and cabin, respectively. The concentrations of Σ8 carcinogenic PAHs in the samples ranged from not detected (nd)–323.3 μg kg−1, 15.7–138 μg kg−1, 9.7–312.9 μg kg−1, nd–331.7 μg kg−1, nd–220.9 μg kg−1, nd–53.3 μg kg−1, 18.4–56.6 μg kg−1, and 6.6–170.8 μg kg−1 for shortcake, digestives, cookies, shortbread, wafers, crackers, Pringles, and cabin, respectively. The margin of exposure (MOE), based on PAH8 as an indicator for the occurrence and effects of PAHs in food, was less than 10,000, the serious health effects value, in 30% and 8% of the brands for the child and adult scenarios, respectively.

Distribution of Polycyclic Aromatic Hydrocarbons (PAHs) in Sediment Cores of Selected Creeks in Delta State, Nigeria

The spatial and seasonal distribution and concentrations of polycyclic aromatic hydrocarbons (PAHs) were investigated in core sediments of Ubeji, Ifie, and Egbokodo creeks in the Niger Delta, Nigeria. A total of 222 core sediment samples were collected during the wet season (August 2010) and the dry season (January 2011). The samples were dried, Soxhlet extracted, fractionated, and injected into a gas chromatograph with flame ionization detector (GC-FID). The concentrations of PAHs ranged from not detected to 2,654 μg/kg (wet season) and not detected to 3,513 μg/kg (dry season). In general, the concentrations of PAHs for a number of stations in this study are comparable to sites with high anthropogenic activities in the Niger Delta. The toxicity risk assessment based on the total BaP equivalent quotient of the seven carcinogenic PAHs (BaA, Chry, BbF, BkF, BaP, DBA, and Iper) was 97.416 μg/kg and did not exceed the method B cleanup level for benzo(a)pyrene (137 μg/kg), according to toxic equivalency factors, which implied that PAHs in sediments of the present study currently have minimal adverse effects. This study provided information on the concentrations and profiles of PAHs sediment cores, which is useful for source diagnosis, environmental quality management, contamination history, and environmental forensic studies.

Concentrations of selected metals in chicken eggs from commercial farms in Southern Nigeria

This work presents the results of the determination of concentrations of the trace metals Ni, Zn, Mn, Pb, Cd, Cr, Co, Cu, and Fe in eggs from farms in Southern Nigeria. The mean concentrations (µg g−1 fresh weight) ranged from 0.6 to 1.2 for Ni, 3.1 to 8.9 for Zn, 0.45 to 0.65 for Mn, 0.4 to 1.2 for Pb, <0.09 to 0.3 for Cr, 0.1 to 0.3 for Cd, 0.26 to 0.34 for Co, 0.9 to 1.2 for Cu and 19.5 to 24.0 for Fe. The concentrations and estimated dietary intakes of these metals were below the respective statutory limits. The Target Hazard Quotient (THQ) values for the individual metals in all zones are less than 1, i.e., within safe levels. The combined THQ values for the different zones were greater than 1but less than 2, with a significant contribution of cobalt.

Chemical fractionation and mobility of metals in floodplain soils of the lower reaches of the River Niger, Nigeria

The chemical fractionation of nine metals, Cd, Pb, Cr, Ni, Cu, Co, Ba, Mn and Zn, in soil profiles of the floodplain of the lower reaches of the River Niger in Nigeria, was investigated with a view to providing information on the forms, bioavailability and mobility of these metals in the soil profiles. The chemical forms of metals in the soil were determined by using the European Community Bureau of Reference (BCR) sequential chemical extraction method and the concentrations were measured by inductively coupled plasma-atomic emission spectrophotometry (ICP-AES). The results indicated that the residual and Fe-Mn oxide/hydroxide phases were the predominant forms of the metals in the soil profiles. The percentage of metals in the readily available and potentially available fractions followed the order: Pb > Ba > Cd > Ni > Co > Zn > Mn > Cu > Cr. Significant proportions of these metals were found in the potentially available phases, which indicate an increase in mobility and availability as a result of changes in the physicochemical characteristics (pH and Eh) of the soil following flooding events.