Abass A. Olajire

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 PO43- on water samples of river Osun,selected rivers in the region and groundwaters. The pH,temperature, electrical conductivity (EC), total dissolvedsolids (TDS), total hardness (TH) and total carbon (IV) oxide(TCO2) have also been determined to asses the chemicalstatus and pollution levels of these water sources. The highervalues of certain parameters with respect to the acceptablestandard limits for drinking water indicate the pollution inboth groundwater and river water samples of the study area, and make the waters unsuitable for various applications. Thehigh pollution river water source showed higher levels ofphosphate, nitrate and ammonium ions (P < 0.05). There is nosignificant difference (P < 0.05) between the meanconcentrations of other inorganic nutrients in the high and lowpollution water source types. The correlation coefficientbetween quality parameter pairs of river water and groundwatersamples are determined and the significance of these parametersin both types of water sources are discussed.

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

A knowledge of the total content of trace metals is not enoughto fully assess the environmental impact of polluted soils. Forthis reason, the determination of metal species in solution isimportant to evaluate their behaviour in the environment andtheir mobilization capacity. Sequential extraction procedure wasused to speciate five heavy metals (Cd, Pb, Cu, Ni and Zn) fromfour contaminated soils of Southern Nigeria into sixoperationally defined geochemical species: water soluble,enchangeable, carbonates, Fe-Mn oxide, organic and residual.Metal recoveries were within ± 10% of the independentlydetermined total Cd, Pb, Cu, Ni and Zn concentrations. The highest amount of Cd (avg. 30%) in the nonresidual fractionswas found in the exchangeable fraction, while Cu and Zn weresignificantly associated with the organic fraction. Thecarbonate fraction contained on average 14, 18.6, 12.6, 13 and11% and the residual fraction contained on average 47, 18, 33,50 and 25% of Cd, Pb, Cu, Ni and Zn respectively. Assuming thatmobility and bioavailability of these metals are related to thesolubility of the geochemical form of the metals, and that theydecrease in the order of extraction sequence, the apparentmobility and potential bioavailability for these five metals inthe soil were: Pb > Zn > Cu > Ni > Cd. The mobility indexes ofcopper and nickel correlated positively and significantly withthe total content of metals, while mobility indexes of cadmiumand zinc correlated negatively and significantly with the totalcontent of metals.

Contamination of roadside soil and grass with heavy metals

The concentrations of heavy metals were determined in roadside soil and grass from different locations in Ibadan metropolis and two highways. The levels found (in μg g−1) were: Cr - 20.6-104; Mn - 86.2-355; Fe - 1737-4455; Ni - 10.9-115; Cu - 8.94-80.5; Zn - 43.5-213; Cd - 0.18-2.70; and Pb - 205-730. There was no significant difference (P < 0.10) between the mean concentrations of these metals in the high and low traffic density areas suggesting that sources other than the motorcar also influence the levels of these metals in roadside soil and grass.

Distribution of polycyclic aromatic hydrocarbons in surface soils and water from the vicinity of Agbabu bitumen field of Southwestern Nigeria

Water and soil samples from the vicinity of Agbabu bitumen field of Southwestern Nigeria, were analyzed qualitatively and quantitatively for 10 parent polycyclic aromatic hydrocarbons (PAHs) using gas chromatography coupled by flame ionization detector (GC-FID), in order to gather information on the degree of contamination by bitumen exploration and processing in this area. The total concentrations of 10 PAHs varied from 11.2 to 341.5 μ g L− 1 in water and from 101.5 to 209.7 ng g− 1 dry weight in soils. The total PAH levels in water samples from all the sampling stations (except at station WB 11), were sufficiently high (> 10 μ g/L) to cause acute toxicity to the exposed organisms. Special PAH compound ratios, such as phenanthrene/anthracene and fluoranthene/pyrene, were calculated to evaluate the relative importance of different origins. The collected data indicate pyrolytic and petrogenic sources. The anthropogenic PAHs, i.e., pyrene and benzanthracene exhibited similar distribution patterns in the studied area, implying that these compounds possess identical sources. Also, dibenzothiophene, a sulfur heterocyclic aromatic compound was determined in this study and it was not detected in all the samples analyzed.

Erratum to: Distribution and ecotoxicological significance of polycyclic aromatic hydrocarbons in sediments from Iko River estuary mangrove ecosystem.

The distribution of polycyclic aromatic hydrocarbons (PAHs) in epipelic and benthic sediments from Iko River estuary mangrove ecosystem has been investigated. Total PAHs ranged from 6.10 to 35.27 mg/kg dry weight. Quantitative difference between the total PAHs in epipelic and benthic sediments showed that the benthic sediment known for higher capability to serve as sink for chemical pollutants accumulated less PAHs. This implies that PAHs in the epipelic sediment may plausibly be from industrial sources via runoff and/or of biogenic origin. A strong pyrolytic source fingerprint has been detected with slight influence of petrogenic sources. Total organic carbon normalized PAHs (sum of 16 PAHs, 59.7 to 372.4 mg/kg OC) were under (except for ES3 and BS3) the threshold effects concentrations (TEC, 290 mg/kg OC). Total PAHs in Iko River estuary sediments were in the range between ERL and ERM.

A survey of heavy metal deposition in Nigeria using the moss monitoring method

The bioaccumulation of Sb, Sn, As, Fe, Ni, Mn, Pb, Cu, and Zn in mosses from polluted and unpolluted areas of the southern parts of Nigeria is presented. Results of the moss samples show strong variations in the concentration of metal ions with type of sampling sites. The concentration of accumulated heavy metals also differs in various moss species from the same biotope. Bryidae mnium is a better accumulator of heavy metals than Tetraphidae tetraphis, as evidenced from the interspecies calibration between the two moss samples.

Distribution and risk assessment of trace metals in Leptodius exarata, surface water and sediments from Douglas Creek in the Qua Iboe Estuary

Abstract Five trace metals in Leptodius exarata, epipellic sediments and surface water from an intertidal ecosystem in the Niger Delta (Nigeria) were studied to evaluate their spatial distributions, degrees of contamination, and associated ecological and health risks. The results show that the Cd (cadmium), Cr (chromium), Ni (nickel), Pb (lead) and Zn (zinc) concentrations in sediment range from 0.550–1.142, 9.57–15.95, 9.15–13.96, 2.00–8.90 and 91.5–121.6 mg kg−1 dw, respectively, while the L. exarata tissue metal content varies from 0.162–0.931, 3.81–8.62, 4.45–17.15, 1.90–7.35, and 125.55–269.75 mg kg−1 dw, respectively. The bioconcentration factor ranking for trace metals was found to follow the Zn > Ni > Pb > Cr > Cd sequence. The high biota to sediment accumulation factor (BSAF) found for L. exarata reveals a sentinel metal bioindicator. Sediments from most sites were found to be uncontaminated to moderately contaminated (geoaccumulation, Igeo > 0), with Cd and Zn associated with anthropogenic intrusions. Low mean-ERM (effect range-median) and mean-PEL (probable effect level) quotients of sediments were found, indicating low–moderate degrees of contamination with 30% and 21% probabilities of toxicity. The multi-metal potential ecological risk index (RI) for the intertidal ecosystem denotes low–moderate risk. Health risks associated with crab (L. exarata) consumption are more significant for children than for adults.

N-Alkane distributions in soil and water samples collected near Agbabu bitumen field of southwestern Nigeria

Soil and water samples from the vicinity of Agbabu bitumen field of Southwestern Nigeria were analysed by GC‐FID for n‐alkanes, in order to characterize their distributions and to gather information on the degree of contamination by bitumen exploration and processing and other biogenic contributions. Total concentrations of n‐alkanes in water and soil samples analysed ranged from 61.5 to 472.7 µg L−1 and 422.8 to 2289.4 ng g−1 dw, respectively. On the basis of the total n‐alkane concentrations, carbon preference index (CPI) values and the odd‐even carbon predominance, it is suggested that both natural (e.g. aquatic input) and anthropogenic (e.g. bitumen and synthetics) sources contribute to the n‐alkanes load in soil and water samples of the area studied.

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.

A new method for assessment of sediment-associated contamination risks using multivariate statistical approach

Graphical abstract