Contribution of groundwater to dietary requirements of essential metals in Lagos and Ogun States, Nigeria.

Knowledge of dietary intakes of essential elements in groundwater is important for proper assessment of the actual contribution of drinking water to daily nutrient requirements. This study assessed the daily intake of nutritional elements in drinking groundwater of Lagos and Ogun States of Nigeria. One hundred and seventy (170) water samples were collected and analyzed for thirteen (13) nutritional elements (K, Mg, Ca, Co, Fe, Cu, Zn, Mo, Se, Na, Mn, Cr, and I) by Inductively Coupled Plasma-Mass Spectrometry (ICP/MS). Chronic daily intake CDI of the nutritional elements was higher for children and infants than adults in all cases. Percentages of tolerable daily intake reference value (TIRV) obtained for Lagos State groundwater were Mg 0.425%, Ca 0.309%, Fe 14.0%, Cu 1.84%, Zn 6.25%, Mo 0.057%, and Mn 1.08%; for Ogun State groundwater, % TIRV were Mg 1.99%, Ca 0.586%, Fe 81.1%, Cu 2.12%, Zn 9.21%, Mo 1.16%, and Mn 0.023%. The order of dermal absorption by an adult in Lagos when the water is used for bathing daily was Cr > Mn > Fe > Zn > Cu while the order in Ogun was Fe > Mn > Zn > Cu > Cr. The research concluded that groundwater alone cannot provide enough essential elements for human dietary needs in the study area.

Elemental enrichment of sediments in an unprotected shallow groundwater of Lagos and Ogun States, Nigeria.

Sediments quality is a good indicator of pollution in a water body where various elements were concentrated. Limited information is available on sediments from hand-dug wells. The present study evaluates sediment samples collected from groundwater of Lagos and Ogun States, Southwest Nigeria. Twenty sediment samples were collected from shallow groundwater, and ten rock samples were also collected from the vicinity of recently dug wells. Trace elements were determined in both the sediments and the rock samples using inductively coupled plasma-mass spectrometry. The enrichment factor was calculated for different elements using Fe, Ti, Mn and Cu as normalizing elements. The order of sediment contamination with each normalizing elements are Cu > Mn > Ti > Fe. The geo-accumulation (Igeo) indexes for Cr, Pb, Cu and Ni are 1.31, 1.05, 1.94 and 1.85, respectively. The Igeo for Lagos sediments is in the order Cr > Pb > Ni > Cu, while in Ogun sediments the order is Cu > Ni > Cr > Pb. The results were compared with Canadian Council of Ministers of Environment values of threshold effect level and probable effect level, which shows the sediments are not toxic. The pollution load index and ecological risk index values are 2.463 and 0.0014, respectively, which further indicates the sediments are not toxic in nature. The major source of most elements in sediments is the host rocks found in the vicinity of the groundwater while high level of some elements recorded in sediments are from the anthropogenic sources.

Evaluation of rare earth elements in groundwater of Lagos and Ogun States, Southwest Nigeria.

Rare earth elements in our environment are becoming important because of their utilization in permanent magnets, lamp phosphors, superconductors, rechargeable batteries, catalyst, ceramics and other applications. This study was conducted to evaluate the level of rare earth elements (REE) and the variability of their anomalous behavior in groundwater samples collected from Lagos and Ogun States, Southwest, Nigeria. REE concentrations were determined in 170 groundwater samples using inductively coupled plasma-mass spectrometry, while the physicochemical parameters were determined using standard methods. Lagos State groundwater is enriched with REE [sum REEs range (mean ± SD)]; [0.365-488 (69.5 ± 117)] µg L-1 than Ogun State groundwater [sum REEs range (mean ± SD)]; [1.14-232 (22.6 ± 41.1)] µg L-1. Boreholes are more enriched with REEs than wells. Significant (P < 0.05) positive correlation (R = Pearson) was recorded in Lagos State groundwater between sum REEs and Fe (R = 0.55). However, there were no significant correlations between sum REEs, pH (R = 0.073) and HCO32- (R = 0.157) in Ogun State groundwater. Chondrite-normalized plot shows that Lagos groundwater exhibits positive Ce anomaly, while Ogun State groundwater does not. The source of REE in Lagos State may be from the ocean and leaching from wastes dumpsites, while the source in Ogun State groundwater may be from the rocks.

Toxic elements in groundwater of Lagos and Ogun States, Southwest, Nigeria and their human health risk assessment.

A good quality drinking water is essential for human survival. However, a large percentage of the populations in most developing countries (Nigeria inclusive) do not have access to potable water. This study was therefore conducted to assess the extent of risk arising from consumption of toxic elements in groundwater samples collected from Lagos and Ogun States, Southwest, Nigeria. Twelve toxic elements concentrations (As, Mn, Cd, Cr, Pb, Ni, Al, Ti, V, Hg, Li, and Sn) were determined from 170 groundwater samples using inductively coupled plasma-mass spectrometry, and the physicochemical parameters were determined using standard methods. The pH results revealed that most of the water samples were slightly acidic. Of the twelve toxic elements, only Mn, Cd, Pb, Ni, and Al have concentrations higher than the WHO recommended limit in drinking water. The average dose of Mn and Al consumed daily from groundwater by an adult in Lagos state is 3.4 and 23.2 (µg/kg body weight), respectively. Similarly, an adult in Ogun State consumed an average daily dose of 6.09 and 25 (µg/kg body weight) Mn and Al, respectively. A greater threat was posed to children and infants. The order for risk of cancer in groundwater from Lagos State was Pb > Cr > As > Cd while the order in Ogun State groundwater was Cr > Cd > As > Pb. The relative high concentrations of Mn, Al, and Pb obtained in this study can be attributed to industrial and anthropogenic activities in the study area. Treatment of groundwater before consumption is recommended to avoid possible adverse cumulative effect. Improved waste disposal methods and regular monitoring of toxic elements in groundwater of the study area should be adopted to safeguard human health.

Chemical composition and functional properties of raw and roasted Nigerian benniseed (Sesamum indicum) and bambara groundnut (Vigna subterranean).

Benniseed and bambara groundnut seeds were roasted at 80 and 120°C for 10-60min. For both flours, the effects of roasting temperature and time on selected functional properties and chemical composition were determined, as were the effects of pH on the emulsification capacity and nitrogen solubility. The chemical constituents of the raw flours were present at higher concentrations than those of the roasted flours except for fat and ash. Protein concentrates of both flours contained 80.5-81.5% crude protein as the major constituent. Nitrogen solubility was lowest at pH 4.0 for raw and roasted benniseed flour and pH 5.0 for raw and roasted bambara groundnut flour. Roasting generally lowered the nitrogen solubility and increased the water and oil absorption capacities while decreasing the foaming capacity and emulsification capacity of both flours.