O.I. Asubiojo

Trace elements in drinking and groundwater samples in southern Nigeria.

The levels of Al, Sn, Cs, Rb, Sr, Br, Cr, Mo, Co, Ba, Cu, Zn, Cd, Pb, Mn, Se, As, V and Ni were determined in drinking water supplies (public taps, domestic taps and treated water from public water sources) and groundwater supplies (boreholes and shallow wells) in some parts of Southern Nigeria. The water samples were analysed using inductively coupled plasma mass-spectrometry (ICP-MS). The mean levels (microgram/l) of all the elements ranged between 0.35 microgram/l for Cs and 87.3 micrograms/l for Zn in the drinking waters and between 0.54 microgram/l for Co and 420.3 micrograms/l for Ba in the groundwaters. A comparison of the elemental concentrations with WHO guidelines showed that with the exception of violations of Cd, Cr and Se limits in some of the drinking water samples, the levels of all the other elements investigated were below the WHO maximum allowable concentrations.

Trace elements in bottled and soft drinks in Nigeria — a preliminary study

The levels of Co, Cu, Zn, Cd, Pb, Cr, Se and Ni were determined in bottled waters and soft drinks in Nigeria. The mean levels of the elements ranged between 0.52 microgram/l for Co and 14.8 micrograms/l for Mn in the bottled waters and 3.10 micrograms/l for Co and 82.4 micrograms/l for Mn in the soft drinks, respectively. Comparison of the elemental concentrations in the water samples with WHO limits showed the mean levels of all the elements investigated in all the samples were below the WHO maximum allowable concentrations for drinking waters.

Effects of cement production on the elemental composition of soils in the neighborhood of two cement factories

The effects of cement production on the elemental composition of soils in the neighborhood of two cement factories in Nigeria have been investigated using the XRF and PIXE/RBS techniques. The concentration of 21 elements viz:-Mg, Al, Si, P, S, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Sr, Pb, As, Zr, Rb and Br, were determined in about 30 samples. Calcium, P, S, Cr, Ni, Cu and Zn, were found to be relatively enriched in the soils of the cement factory premises. Calcium, a cement marker element, was found to be well correlated with Mg, S, Fe, Ni and Cu in the soils, and inversely proportional to the Si and Ti concentrations. From Ca/Si ratios and enrichment factors of the marker elements, it was found that soil contamination due to cement drops sharply with distance from the factories, and with increasing depth from the surface.

PIXE characterization of PM10 and PM2.5 particulates sizes collected in Ikoyi Lagos, Nigeria

Ambient concentrations of PM10 (x ≤ 10 µm) and PM2.5 (x ≤ 2.5 µm) particulate fractions collected from Ikoyi Lagos, Nigeria, as well as their elemental compositions are presented in this study. Both size-segregated fractions were collected using a double staged ‘Gent’ stack filter unit sampler. Elemental characterizations of dust laden filters were carried out using proton-induced X-ray emission (PIXE) technique. Twenty-two elements (Si, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pb, Br, Rb, Sr, Zr, Ag, Cd, and Ta) were detected as well as their concentrations and correlations were determined for both particulate size fractions. Their correlation matrix result indicates that some of the trace elements detected could have common source origins or similar chemical properties. The results were similar to the levels observed in moderately polluted urban areas and there is need for source identification and apportionment using receptor models in future studies.

Isolation and Determination of Polycyclic Aromatic Hydrocarbons in Surface Runoff and Sediments

The distribution of Polycyclic Aromatic Hydrocarbons (PAHs) was investigated in surface runoff and sediments of Lagos, Osogbo and Ile-Ife Western areas of Nigeria. Method for the analysis of PAHs was based on Liquid-Liquid extraction of the runoff and a soxhlet extraction of the sediments followed by a clean up adsorption procedure. The PAHs were separated and quantified by Gas Chromatography-Mass spectrometry (GC-MS) technique. A blank experiment was done using triply distilled water and following the same procedure for the samples to establish blank levels. In both street runoff and sediments 13 PAHs were identified and quantified. At Osogbo and Ile-Ife areas, the mean levels of PAHs in surface runoff ranged between 0.10–15.81 mg L-1 while in the Lagos area the levels were between 0.1–73.72 mg L-1. Generally, the PAH levels in surface runoff of Lagos constitute 53.03 mg L-1 average ∑ PAH detected in the study area compared to 31.96 mg L-1 average ∑ PAH contribution made by samples from Osogbo and Ile-Ife. The levels of PAHs in sediments are relatively higher compared to those of the street runoff in the study area. PAHs in sediment of Lagos contribute an average of 228.57 mg kg-1 ∑ PAH to the total sediment PAH burden compared to Osogbo and Ile-Ife areas that contribute only 91.13 mg kg-1 average ∑ PAH to the total PAH burden of the study area. The relatively higher average ∑ PAHs reported for Lagos area compared with those of Osogbo and Ile-Ife, is consistent with higher industrial activities and traffic density of the former (1000–10000 vehicles/hr) than the later (450–1500 vehicles/hr).

Organochlorine Pesticide Residues in Sediments and Waters from Cocoa Producing Areas of Ondo State, Southwestern Nigeria

This study investigated levels of organochlorine pesticide (OCP) residues in water and sediment samples from eleven rivers serving as drinking water sources and receiving runoff from nearby cocoa plantations in Ondo State, Nigeria. Twenty-two composite samples of surface water and sediments (0–3 cm) were collected randomly using grab technique and replicated thrice per season. The efficiency of the two techniques [supercritical fluid extraction (SFE) and liquid/liquid extraction (LLE)] was evaluated with percentage analyte recoveries to for SFE and to 1 for LLE. Determination of OCPs by gas chromatography with electron capture detection gave higher concentrations for sediments compared to the equivalent water samples. The commonly occurring pesticide residues in the sediments were (range, μg g−1) cis-chlordane 0.03–6.99; α-endosulfan 0.03–6.99; p,p′-DDE 0.08–19.04; and dieldrin 0.01–7.62; in the sediments and dieldrin (not detected-1.51 μg L−1) in water samples, during the dry season. OCP levels were significantly higher in dry season than wet season among the rivers. The study concluded that most of the rivers in cocoa growing areas were contaminated with OCPs associated with agricultural activities.

Trace element and physico-chemical characteristics of the sand and water fractions of Nigerian bituminous sands

Bituminous sands from south-western Nigeria were separated into water and sand fractions, and these were analysed for their physico-chemical properties and trace-metal contents to evaluate their potential environmental hazards. The samples were obtained from five different locations (Ilubirin, Agbabu, Mile 2, Olowo-Irele, and Loda) in Ondo State, south-western Nigeria. The water content was extracted using Dean and Stark apparatus, while the sands were collected as left-over from the thimble. The trace metal content was determined using total X-ray fluorescence (TXRF) spectrometry. The physico-chemical parameters (conductivity, pH, total alkalinity, total acidity, salinity, colour, organic matter, Cl−, , and ) were determined using standard analytical methods. Copper, Cr, Zn, and As, which are known to be toxic metals, were highly enriched (enrichment factor, EF>10) in the sand fraction samples, while comparison of some of the physico-chemical parameter values of the water and sand fractions with recommended standards showed that the values of some of the parameters were relatively high. These values indicate their potential environmental hazards. This calls for proper management of the tailings that will be produced during the exploitation of the bituminous sands. Analysis of certified IAEA standard reference material (IAEA-soil-7) was carried out to ensure accuracy and precision of the TXRF technique.

Elemental composition of drinking water supplies in three states in Southeastern Nigeria

The levels of some trace elements; Co, Mn, Cu, Zn, Cr, Cd, Pb, Fe, Hg, Se, As, Ni and minor elements; Na, K, Ca and Mg were determined in public drinking water supplies (public taps and groundwaters) in three states in Southeastern Nigeria using energy dispersive X-ray fluorescence spectrometry (EDXRF) and flame atomic absorption spectrometry (FAAS). The mean levels of most of the trace elements in the groundwater samples were below the World Health Organization (WHO) drinking water quality limits, the only exception being Hg whose mean value of 3.69 μg/l exceeded the WHO limit of 1.0 μg/l. Violations of the WHO limits were also observed for Fe, Zn, Se and Pb in some of the groundwater samples. In the public tap samples only Hg violated the WHO limit.

Removal of heavy metals from industrial wastewaters using natural adsorbents

The use of readily available natural materials as adsorbents of heavy metals from industrial wastewaters was investigated. The natural materials investigated were bagasse, paddy husk, corn cob, wheat bran, peanut skin, and human hair. Two modes of removal were carried out. In one set of experiments, effluents from different industries were run through columns packed with natural adsorbents. In the other set, the effluents were simply agitated with known weights of the natural adsorbents. Heavy metal concentrations of the industrial effluents were determined before and after contact with the natural adsorbents using atomic absorption spectroscopy. Parameters such as column height, substrate weight, particle size of the substrate, and the pH of the substrate in solution were varied to obtain optimum conditions for heavy metal removal. Virtually all the materials were found to be good scavengers of heavy metals, comparable to the conventional, expensive commercial materials such as ion-exchange resins commonly used for wastewater treatment. The mechanism of removal is proposed to be similar to ion-exchange resins and adsorption. The adsorption capacities of the natural adsorbents vary from one heavy metal to another. Based on the overall mean percentage removal of heavy metals (87.6–92.2%), the heavy metal adsorbing capacity of the natural adsorbents is of the order: corn cob > paddy husk > peanut skin > human hair > wheat bran > bagasse. In terms of heavy metal adsorbed per unit weight of adsorbent, the efficiency of heavy metal scavenging is of the following order: bagasse and human hair > corn cob and peanut skin > wheat bran > paddy husk. Efficiency of heavy metal removal by the natural adsorbents increases with column height and decreases with particle size of adsorbent and residual heavy metal concentration in the effluent. In view of its efficiency, simplicity, low cost, and reliability, this technique has very good potential for heavy metals removal from high-volume industrial wastewaters.

Elemental concentrations and source identification of air particulate matter at a Nigerian site: A preliminary study

Air particulate matter collected between July and October 1990 at a site located close to an industrial estate in Lagos, Nigeria were analyzed for 18 elements by Wavelength Dispersive X-ray Fluorescence Spectroscopy (XRF) and Atomic Absorption Spectroscopy (AAS). Varimax rotated factor analysis was used for source identification of the coarse and fine fractions. For the coarse fraction, the major sources are: Re-entrained soil, Sea-salt, Industry, Regional sulphate and fresh automobile exhaust. For the fine fraction, the sources identified are Re-entrained soil, Vehicle exhaust, Sea-salt, and Industrial processes. Two other sources which are likely to be due to specific industrues come out in the fine fraction but they have not been clearly identified.