Background. Heavy metal contamination has become a challenge in Nigerian cities. Objective. This review updates our current understanding of the environmental health effects of metal pollution in Nigeria. Methods. The review was conducted by systematically searching the databases of GOOGLESCHOLAR, MEDLINE, PUBMED CENTRAL, and PUBMED libraries for original research using search terms such as ‘metal pollution in Nigeria’, ‘bio-monitoring of lead, cadmium, nickel and chromium in Nigeria’, ‘lead in Nigeria’, ‘cadmium in Nigeria’, ‘nickel in Nigeria, and ‘chromium in Nigeria’. Discussion. This review highlights the need for the study of the toxicological implications of chronic, low-level exposure to heavy metals in African markets. Elevated blood lead levels (BLLs) have been documented in Nigerian populations across all ages, socioeconomic classes, sex, etc. Conclusions. There is a need to assess BLLs across populations in Nigeria by undertaking sound scientific studies using appropriate sample sizes and methodologies. In particular, information is needed on both non-occupational and occupational exposures to adults that may result in children being exposed. A comprehensive strategy is needed to reduce lead exposure in order to reduce the future economic and disease burden in Nigeria. Competing Interests. The authors declare no competing financial interests.

The purpose of this research was to thoroughly analyze the influences of environmental factors on denitrification processes in urban riparian soils. Besides, the study was also carried out to identify whether the denitrification processes in urban riparian soils could control nonpoint source nitrogen pollution in urban areas. The denitrification rates (DR) over 1 year were measured using an acetylene inhibition technique during the incubation of intact soil cores from six urban riparian sites, which could be divided into three types according to their vegetation. The soil samples were analyzed to determine the soil organic carbon (SOC), soil total nitrogen (STN), C/N ratio, extractable NO₃⁻-N and NH₄⁺-N, pH value, soil water content (SWC), and the soil nitrification potential to evaluate which of these factors determined the final outcome of denitrification. A nitrate amendment experiment further indicated that the riparian DR was responsive to added nitrate. Although the DRs were very low (0.099 ~ 33.23 ng N₂O-N g⁻¹ h⁻¹) due to the small amount of nitrogen moving into the urban riparian zone, the spatial and temporal patterns of denitrification differed significantly. The extractable NO₃⁻-N proved to be the dominant factor influencing the spatial distribution of denitrification, whereas the soil temperature was a determinant of the seasonal DR variation. The six riparian sites could also be divided into two types (a nitrate-abundant and a nitrate-stressed riparian system) according to the soil NO₃⁻-N concentration. The DR in nitrate-abundant riparian systems was significantly higher than that in the nitrate-stressed riparian systems. The DR in riparian zones that were covered with bushes and had adjacent cropland was higher than in grass-covered riparian sites. Furthermore, the riparian DR decreased with soil depth, which was mainly attributed to the concentrated nitrate in surface soils. The DR was not associated with the SOC, STN, C/N ratio, and pH. Nitrate supply and temperature finally decided the spatiotemporal distribution patterns of urban riparian denitrification. Considering both the low DR of existing riparian soils and the significance of nonpoint source nitrogen pollution, the substantial denitrification potential of urban riparian soils should be utilized to reduce nitrogen pollution using proper engineering measures that would collect the polluted urban rainfall runoff and make it flow through the riparian zones.

The annual atmospheric deposition rates of²¹⁰Po and²¹⁰Pb were determined in İzmir, Turkey. The samples were collected from 18 November 2008 to 17 November 2009. The annual²¹⁰Po deposition flux was determined as 44.1 ± 3.0 Bq m⁻² year⁻¹, while²¹⁰Pb flux was calculated as 73.1 ± 4.4 Bq m⁻² year⁻¹using bulk collectors. The monthly deposition fluxes of²¹⁰Po and²¹⁰Pb were correlated with the amount of precipitation. The activity concentrations of the samples were found to vary between 5.7 ± 1.1 and 167.1 ± 7.5 mBq L⁻¹, with an average value of 41.2 ± 1.9 mBq L⁻¹for²¹⁰Po; and between 5.3 ± 0.6 and 265.7 ± 10.8 mBq L⁻¹, with an average value of 67.3 ± 2.7 mBq L⁻¹for²¹⁰Pb. The activity ratios of²¹⁰Po/²¹⁰Pb in the samples ranged from 0.16 to 3.39, with an average value of 0.80. During the course of the study,²¹⁰Po enhancement from both natural and anthropogenic sources was observed.

The objective of this study was to investigate the effect of chloride ions (Cl⁻) on Cu²⁺adsorption to carbon nanotubes (CNT). The isotherms showed a significant decrease in adsorption capacity on F-400, pristine, and acid-functionalized CNT in the presence of Cl⁻, but had little effect on alcohol-functionalized CNT. Several inductively coupled plasma (ICP) analyses measured the impurities concentration of (1) aqueous-phase isotherm solute, (2) as-received, and (3) acid-washed CNT solutions. Chemical-equilibrium-modeling software MINEQL⁺calculations were applied to compare ICP results to complexes formation. The model suggested that some solid-phase residual-catalytic metals, such as Cr²⁺, after released in water from as-received CNT, formed aqueous-phase complexes and were readsorbed. The 18-metal ICP results were more than two orders of magnitude lower (<4 μM/g-adsorbent) than the lowest isotherm Cu²⁺concentration (157 μM) without significant impact on the isotherm results. The reduced adsorptive capacity of acid-functionalized CNT was related to the mechanisms of water molecule displacement followed by deprotonation during Cu²⁺sorption in the CNT-surface hydration layer and its interaction with other species, generating different ion exchange forces. Brunauer–Emmett–Teller and pore-distribution measurements defined bulk water structure within CNT bundles. Zeta-charge and pHpzc measurements compared as-received and hybrid-CNT indicating copper chemisorption. Functionalized CNT remained negatively charged above pH 2.7, suggesting consistent adsorptive capacity at pH > 5.1, when less Cu²⁺ions are present in solution. scanning electron microscopy–energy dispersive X-ray spectroscopy analysis showed impurities on as-received F-400 and positively charged surface at pH 5.1 (pHpzc 7.1) explaining possible electrostatic attraction of Cl⁻ions, blocking adsorptive sites, reducing its adsorptive capacity for Cu²⁺.

Sulfur hexafluoride (SF₆) has been evaluated by the Intergovernmental Panel on Climate Change (IPCC) as the substance with the highest global warming index. Because of its superior insulating and arc clearing capacities, it is commonly used as an insulator in electrical machines. SF₆waste products form in the process of storing, maintaining, and repairing the machines. SF₆emitted into the atmosphere remains for 3,200 years, causing global warming. Release into the mesosphere leads to photolysis and creation of highly toxic and corrosive by-products. A review of the literature related to the retrieval and separation of SF₆using a separating membrane indicates that research on the permeability of the separating membrane material is lacking. Additionally, research on the concentrations of the SF₆waste products and the separation/retrieval with operating conditions with optimal energy efficiency is only in the initial stages. Therefore, this research assessed the permeability of commercialized separation membranes polysulfone (PSf), polycarbonate (PC), and polyimide (PI) using the gases SF₆and N₂. Using an SF₆/N₂mixture with the same concentration as the SF₆waste products, we studied the separation and retrieval capacities of PSf, PC, and PI separation membranes under varying operating conditions. The permeability tests showed that the selective permeability of N₂/SF₆is highest for the PI membrane and lowest for the PC membrane. When the concentrations of SF₆retrieved from the mixture separation process were compared, the PC membrane was found to be the highest, with 95.6 % at 0.5 MPa. The retrieval percentage of SF₆was highest for PSf, with 97.8 % at an operating pressure of 0.3 MPa and a waste production of 150 cm³/min. The retrieval rates and retrieval failure rates have an inverse relationship. In total, 99 % of the supply of SF₆was identified via the retrieval rates and retrieval failure rates, so it could be confirmed that the separation of the SF₆/N₂mixture using a macromolecular hollow fiber separation membrane works properly.

We measured C and N cycling indicators in Appalachian watersheds impacted by mountaintop removal and valley fill (MTR/VF) coal mining, and in nearby forested watersheds. These watersheds include ephemeral, intermittent, and perennial stream reaches, and the length of time since disturbance in the MTR/VF watersheds was 5 to 11 years. In forest soils compared to VF soils, both denitrification enzyme activity (DEA) and basal respiration (BR) were elevated (factor of 6 for DEA and factor of 1.8 for BR expressed on a weight basis) and bulk density was lower. Organic matter (OM) and moisture were higher in the forest soils, which likely contributed to the elevated DEA and BR levels. Evaluation of soils data from our intermittent watersheds as a chronosequence provides some evidence of soil quality (DEA, BR, and soil moisture) improvement over the course of a decade, at least in the top 5 cm. Across the hydrological permanence gradient, sediment DEA was significantly higher (factor of 1.6) and sediment OM was significantly lower in forested than in VF watersheds, whereas sediment BR did not differ between forested and VF watersheds. Dissolved organic carbon (DOC) concentrations were not different in mining-impacted and forested streams, whereas dissolved inorganic carbon (DIC) concentrations and DOC and DIC stable carbon isotopic compositions (δ¹³C) were significantly elevated in VF streams. The δ¹³C-DIC values indicate that carbonate dissolution was a dominant source of dissolved carbon in MTR/VF mining-impacted streams. The disturbance associated with MTR/VF mining significantly impacts C and N processing in soils, stream sediments, and stream water although our data suggests some improvement of soil quality during the first decade of reclamation.

Mussel (Mytilus galloprovincialis (Lamarck, 1819)) is directly exposed to sea water contamination that elicits significant physiological and cellular response, although its extent mounted in aquaculture-reared in comparison to wild bivalve populations is scarcely known. Therefore, we have compared contamination biomarkers in mussels from reared (Marina farm) and wild, anthropogenically affected site (Vranjic Bay). While predictably, the levels of metals (Cu, Cd, Pb, Zn, Fe, and Hg) in whole bivalve tissues determined by atomic absorption spectrophotometry resulted in significantly higher concentrations in wild mussels, accompanied by elevated number of apoptotic cells in gills, the activity of multixenobiotic resistance defense mechanism (MXR), measured as the accumulation rate of model substrate rhodamine B (RB) gave contrasting results. The functional RB assay evidenced a lower MXR efflux activity in the gill tissue of wild mussels, indicating two possible scenarios that will need further focus: (1) persisting sea water pollution increased cell damage of bivalve gill cells and consequently led to leakage of the RB into cytoplasm and dysfunctional MXR efflux in wild mussels; or/and (2) a mixture of different toxic compounds present in Vranjic Bay sea water induced oversaturation of MXR efflux, inducing elevated accumulation of the dye. Consequently, it seems that an efficient physiological functioning of MXR in wild mussels is strongly hampered by existence of an unknown quantity of sea water pollutants that may endanger intrinsic organismal defense system and lead toward the enhancement of toxicity.

Samples of soil and food plants were collected from wastewater-irrigated and control fields in the vicinity of Gaziantep, in southeast Turkey. The samples were analyzed for concentrations of several macro and trace elements to evaluate spatial differences and bioaccumulation. Emphasis was placed on redoximorphic metal (Mn/Fe) interactions. The plants and tissues that studied were corn (Zea mays) seeds, mint (Mentha) leaves, the vegetables eggplant (Solanum melongena L.) and pepper (Capsicum annuum L.), and tomato (Solanum lycopersicum L.) fruits. Concentrations of Mn and Fe in corn were generally lower than in the other food plants, while concentrations of Mn, Fe, and several elements in mint were higher in other plants. Except for mint, the Mn deficiencies in the various plant samples can be attributed to low Mn soil concentrations and the chemical and physical characteristics of the soil. Mn concentrations in both wastewater-irrigated soils and control soils were lower than what has been reported as an average for the Earth’s crust (crustal average). There was considerable variability in the concentrations of Fe, with mint having the highest concentration (650 mg/kg) and corn the lowest (20 mg/kg). Significant positive relationships (coefficient of determination (R²) >0.50) were calculated between Mn and Fe in corn (R² = 0.83). The R²for tomato was 0.43, but all other relationships were much poorer for all other species. Several elements (trace and macro) demonstrated positive relationships with Mn or Fe, although there was little across-species consistency. For example, the R²values for both Mn and Fe correlated with Zn, P, and Mg were all >0.80 for Z. mays, but were all <0.10 for Mentha. The response of the members of the Solanaceae family (eggplant, pepper, and tomato) to the presence of Mn, Fe, and other soil constituents was similar in many respects, showing differences from Z. mays and, in particular, Mentha. Similarities among related plants are not surprising and would be expected given similar physiologies and metabolic pathways. Higher uptake of certain metals may be associated with the dominant form of the element in the soil matrix. The uptake of chemicals to plant tissues is influenced by the chemical and physical characteristics of the soil and species-specific factors.