Exposure to hazardous air pollutants along Oba Akran road, Lagos-Nigeria.

We measured toxic air pollutants along Oba Akran road in Lagos to evaluate pedestrian exposure. PM10, CO, O3, NO2, SO2, CH4, noise, wind velocity and temperature were measured simultaneously with portable analyzers. Our results showed that pedestrian exposure to PM10 (with an average of 274.6 µg m(-3) for all samples) and CO (with an average of 19.27 ppm for all samples) was relatively high. CO is a traffic-related pollutant, so the influence of the local traffic emissions on CO levels is strong. The high concentration of the PM10 measured at the three environments also suggests that the traffic is a major source of ultrafine particles. The overall average concentrations for the 72-day experimental period for SO2, NO2 and O3 are 101.2, 62.5 and 0.32 ppb respectively, all of which are below the US national ambient air quality standards. Strong traffic impacts can be observed from the concentrations of some of these pollutants measured in these three environments. Most clear is a reflection of diesel truck traffic activity rich in black carbon concentrations. The diurnal variation of O3 and NO2 also showed that NO2 was depleted by photochemically formed O3 during the day and replenished at night as O3 was destroyed. A multivariate statistical analysis (Principal Component Analysis, Factor Analysis) has been applied to a set of data in order to determine the contribution of different sources. It was found that the main principal components, extracted from the air pollution data, were related to gasoline combustion, oil combustion and ozone interactions.

Heavy metal burdens in patches of asphyxiated swamp areas within the Qua Iboe estuary mangrove ecosystem.

This study examined the burden of Zn, Cu, Ni, Pb, Cr and V in patches of asphyxiated mangrove swamp areas within Qua Iboe Estuary mangrove ecosystem by sediments and surface water analysis; in order to establish natural background levels of these metals and to assess anthropogenic influences on them. The analysis shows that the mean concentrations (mg/kg, dw) of Zn, Cu, Ni, Pb, Cr and V in sediments from asphyxiated and healthy mangrove ecosystems of Qua Iboe vary from 36.3-179.4, 29.2-43.2, 3.6-37.4, 39.6-93.8, 0.15-0.53 and 2.9-9.3, with the former exhibiting higher metal accumulating potential. Although heavy metal concentrations in surface water of the asphyxiated swamp were low, their accumulative effect is significant. The concentrations of Cu and Pb in surface water of this ecosystem exceeded the water quality criteria while Ni and Cr were under the maximum concentration for drinking water quality and protection of aquatic life. The values of pollution load index (PLI), which are generally greater than unity, show that the sediments and the surface water from the asphyxiated mangrove ecosystem were polluted with heavy metals, thus suggesting anthropogenic activities as a possible source of these metals. The mean concentrations of Zn, Ni and Pb exceeded the effects range-low (ERL), indicating that there may be some ecotoxicological risk to organisms living in asphyxiated mangrove sediments.

Characterization of trace metal leachability from highway construction solid waste using the toxicity characteristic leaching procedure.

The potential risk of soil, surface and ground water contamination by trace metals leached from highway construction solid wastes is a major environmental concern. The objectives of this study were to evaluate trace metal leachability, toxicity of the leachate to aquatic organism and environmental impacts of highway construction solid waste (HCSW). Potential leachability, defined as the maximum metal pool that may become available for leaching at a constant pH 4 decreased in the following order: Zn > Ni > As > Pb > Cu. Potential metal leachability was controlled mainly by solid phase distribution of metals in wastes. The kinetics of metal release were determined using the cascade leaching test (CLT) with water at pH 4. With the exception of zinc in the first fraction, metal concentrations in all consecutive leaching fractions remained below the maximum permissible level in water for human consumption. The result of toxicity test showed that the leachates were in concentrations that did not exceed toxic concentrations for aquatic toxicity tests. The results indicate low risk of surface and ground water contamination resulting from highway construction solid wastes.

Levels and speciation of heavy metals in soils of industrial Southern Nigeria.

A knowledge of the total content of trace metals is not enough to fully assess the environmental impact of polluted soils. For this reason, the determination of metal species in solution is important to evaluate their behaviour in the environment and their mobilization capacity. Sequential extraction procedure was used to speciate five heavy metals (Cd, Pb, Cu, Ni and Zn) from four contaminated soils of Southern Nigeria into six operationally defined geochemical species: water soluble, enchangeable, carbonates, Fe-Mn oxide, organic and residual. Metal recoveries were within +/- 10% of the independently determined total Cd, Pb, Cu, Ni and Zn concentrations. The highest amount of Cd (avg. 30%) in the nonresidual fractions was found in the exchangeable fraction, while Cu and Zn were significantly associated with the organic fraction. The carbonate fraction contained on average 14, 18.6, 12.6, 13 and 11% and the residual fraction contained on average 47, 18, 33, 50 and 25% of Cd, Pb, Cu, Ni and Zn respectively. Assuming that mobility and bioavailability of these metals are related to the solubility of the geochemical form of the metals, and that they decrease in the order of extraction sequence, the apparent mobility and potential bioavailability for these five metals in the soil were: Pb > Zn > Cu > Ni > Cd. The mobility indexes of copper and nickel correlated positively and significantly with the total content of metals, while mobility indexes of cadmium and zinc correlated negatively and significantly with the total content of metals.

Water quality assessment of Osun River: studies on inorganic nutrients.

The present investigation provides data of some ions, namely Na+, Ca2+, NH4+, Cl-, NO3-, CN- and PO4(3-) on water samples of river Osun, selected rivers in the region and groundwaters. The pH, temperature, electrical conductivity (EC), total dissolved solids (TDS), total hardness (TH) and total carbon (IV) oxide (TCO2) have also been determined to asses the chemical status and pollution levels of these water sources. The higher values of certain parameters with respect to the acceptable standard limits for drinking water indicate the pollution in both groundwater and river water samples of the study area, and make the waters unsuitable for various applications. The high pollution river water source showed higher levels of phosphate, nitrate and ammonium ions (P < 0.05). There is no significant difference (P < 0.05) between the mean concentrations of other inorganic nutrients in the high and low pollution water source types. The correlation coefficient between quality parameter pairs of river water and groundwater samples are determined and the significance of these parameters in both types of water sources are discussed.