Background. There is increasing concern over the health effects of chromium (Cr) exposure stemming from various activities in tanneries in Kenya. Chromium is a toxic metal in its hexavalent form, and is widely used in the tanning process. Objectives. A detailed exposure assessment of Cr and related health effects among tannery workers in Kenya was performed. Methods. Spot urine and 8-hour full-shift personal breathing zone air samples of the workers (N = 40) and control group (N = 40) were collected and subsequently analyzed for total Cr using atomic absorption spectrophotometry. The medical history, respiratory, and dermatological condition of each of the selected workers was determined. Lung function was further investigated using a spirometer. Results. Tannery workers in various production lines had significantly (P < 0.05) higher mean airborne Cr levels (± standard deviation [SD] of 63.0±11.6 μg/m3) compared to those in the control group (1.39±0.64 μg/m3), and general workers had significantly (P < 0.05) higher mean concentrations of Cr (66.8±13.1 μg/m3) than those in other lines of production. A significant positive association (R2 = 0.76, P < 0.001) was also observed between urinary and breathing zone air Cr levels. Mean urinary Cr level exceeded the American Conference of Governmental Industrial Hygienists biological exposure index for Cr of 30 μg/g creatinine, and 78% of Cr levels of the general workers exceeded this limit. Tannery workers showed a significantly (P < 0.05)higher prevalence of respiratory and dermatological symptoms (30% and 20%, respectively) compared to the control group (10% and 7.5%, respectively). It was further established that production workers had significantly reduced ventilatory function, with 17% experiencing pulmonary obstruction, 13% pulmonary restriction, and 7.5% both manifestations compared to 5% for each of the listed corresponding manifestations in the control group. Conclusions. Our study revealed inadequate engineering controls, work practices and personal hygiene, together with improper management of tannery wastes that has led to considerable exposures to Cr and related health effects among workers. Competing Interests. The authors declare no competing financial interests.

Background. The potential toxicity of metals in water may have detrimental effects on the biochemical processes of aquatic organisms, especially fish, which serve as a source of protein in the protein-deficient Nigerian diet. Objective. The present study aimed to determine the concentration of heavy metals in African catfish (C. gariepinus) and investigate the health risk associated with heavy metals in fish. Methods. Heavy metal concentrations in the water samples were determined using atomic absorption spectrophotometry (AAS) and particle induced x-ray emission spectroscopy (PIXE) for sediment and fish tissues/organ samples. Results. Mean nickel (Ni) concentrations differed significantly (p<0.05) by sample type in both the dry and rainy seasons. Similarly, during the rainy season, mean lead (Pb) concentrations in all of the samples from Osogbo differed significantly (p<0.05) by type, with the highest concentration in fish muscle (10.11±1.21 μg/kg) and the lowest Pb concentration in pond water (1.72±0.05 μg/L). Mean chromium (Cr) concentrations of samples from the Ewuru/Rara stream in Yakoyo also differed significantly (p<0.05) by type, with the highest concentration in fish muscle (113.10.±10.07 μg/kg) and the lowest concentration in pond water (3.31±0.22 μg/L). Discussion. Heavy metal concentrations in pond and stream sediment samples revealed transport and deposition processes where trace metals are deposited and incorporated into sediment after entering the aquatic system. Iron (Fe) had the highest concentration levels ranging from (196.21 μg/g – 698.65 μg/g) in the three locations investigated, while Pb levels were the lowest, ranging from (9.05 μg/g – 75.30 μg/g). Conclusions. In general, the concentrations of Cr, copper (Cu) and manganese (Mn) were below standard guidelines, while the concentrations of nickel (Ni) and lead (Pb) were fairly higher than the tolerable limits for water pollution standards. Competing Interests. The authors declare no competing financial interests.

Fugitive greenhouse gas emissions from unconventional gas extraction processes (e.g. shale gas, tight gas and coal bed methane/coal seam gas) are poorly understood due in part to the extensive area over which these emissions may occur. We apply a rapid qualitative approach for source assessment at the scale of a large gas field. A mobile cavity ring down spectrometer (Picarro G2201-i) was used to provide real-time, high-precision methane and carbon dioxide concentration and carbon isotope ratios (δ¹³C), allowing for “on the fly” decision making and therefore an efficient and dynamic surveying approach. The system was used to map the atmosphere of a production coal seam gas (CSG) field (Tara region, Australia), an area containing pre-production “exploration” CSG wells (Casino, Australia), and various other potential CO₂and CH₄sources (i.e. wetlands, sewage treatment plants, landfills, urban areas and bushfires). Results showed a widespread enrichment of both CH₄(up to 6.89 ppm) and CO₂(up to 541 ppm) within the production gas field, compared to outside. The CH₄and CO₂δ¹³C source values showed distinct differences within and outside the production field, indicating a CH₄source within the production field that has a δ¹³C signature comparable to the regional CSG. While this study demonstrates how the method can be used to qualitatively assess the location and source of emissions, integration with atmospheric models may allow for quantitative assessment of emissions. The distinct patterns observed within the CSG field demonstrates the need to fully quantify the atmospheric flux of natural and anthropogenic, point and diffuse sources of greenhouse gases from individual Australian gas fields before and after production commences.

Effects of the combined application of ferrihydrite-modified diatomite (FHMD) and gypsum on phosphorus control were investigated in a laboratory-scale artificial aquarium under anoxic and agitation conditions over 120 days. Daily oscillation of a metal grid to simulate agitating effects by wind did not yield the sediment resuspension in the 120-day treatment aquarium (120-day aquarium) due to the gypsum stabilization, while significant sediment resuspension was observed in the control aquarium. The combined application of FHMD and gypsum did not affect the total kjeldahl nitrogen (TKN) concentrations in both the control aquarium and the 120-day aquarium. Under anoxic conditions and sediment resuspension conditions, a large increase in total phosphorus (TP) concentrations was observed in the control aquarium. However, the TP concentrations in the 120-day aquarium stayed relatively stable, within a range of 9.1–13.3 μg/L. After the 120 days’ incubation, translocation from mobile labile-P and organic-P to P adsorbed by FHMD occurred. The combined application of FHMD and gypsum effectively maintained TP levels within the oligotrophic range under anoxic and agitation conditions in the laboratory-scale artificial aquarium by removing phosphorus from lake water and reducing sedimentary phosphorus release via gypsum sediment stabilization and FHMD phosphorus immobilization.

Phytoremediation can be assisted by microorganisms, which promote plant growth and increase heavy metal availability in soil. In this study, we aimed at evaluating the effect of two plant growth-promoting bacteria (PGPB) on phytoextraction of copper (Cu) by maize. We chose the strains based on their ability to synthesize indole compounds, produce siderophores, solubilize phosphorus, and increase soil conductivity and extractable Cu in soil. Then, in glasshouse experiments, we assessed their ability to increase biomass, chlorophyll content, and Cu extraction by maize. Results showed that Acinetobacter sp. RG30 and Pseudomonas putida GN04 were overall the most active strains to synthesize indole, produce siderophores, and solubilize phosphorus, and hence selected for further studies. Also, both were able to significantly increase soil conductivity and release Cu from soil compared to control. Glasshouse experiments showed that Cu had a negative effect on plant growth, but inoculation with bacteria promoted plant growth and chlorophyll content in its presence (p < 0.05). Notably, the effect of inoculation on plant growth was larger on contaminated than on uncontaminated soil, which suggests an overall bacterial effect for alleviation of stress caused by Cu. Inoculation with RG30 or GN04 improved Cu extraction by maize (p < 0.05); interestingly, co-inoculation led to the highest accumulation (200 μg Cu/g plant dry weight). We conclude, therefore, that inoculation with RG30 and GN04 improves metal extraction by increasing plant growth, fitness, and availability of minerals in soil, which represents an important tool for the improvement of phytoextraction processes in polluted environments.

Novel nanocomposite hydrogels based on wheat bran-g-poly(methacrylic acid) and nano-sized clinoptilolite have been successfully utilized for the removal of Pb(II), Cu(II), Cd(II), and Ni(II) cations from their aqueous solution. The experimental results were investigated using Freundlich, Langmuir, Temkin, and Dubinin–Radushkevich isotherm models. The pseudo-first-order, pseudo-second-order and interparticle diffusion kinetic models were studied in order to analyze the kinetic data. The kinetic data indicated that the rate of cation adsorption on nanocomposite hydrogels was fast that more than 80 % of the equilibrium adsorption capacity occurs within 15 min. The maximum monolayer adsorption capacity of the nanocomposite hydrogel, as obtained from the Langmuir adsorption isotherm, was found to be 166.7, 243.9, 175.4, and 166.6 mg g⁻¹ for Pb(II), Cu(II), Cd(II), and Ni(II), respectively. Thermodynamic parameters such as free energy (ΔG ⁰), enthalpy (ΔH ⁰), and entropy (ΔS ⁰) change were determined; the sorption process was found to be endothermic. The results of five times sequential adsorption–desorption cycle showed high adsorption efficiency and a good degree of desorption.

Adsorption and degradation processes of triclosan (TCS) were studied in the laboratory using field-collected sediments of different physicochemical properties. Batch equilibrium experiment indicated that adsorption isotherms were fitted well to both linear and Freundlich model with linear sorption coefficients (K d) varied from 147 to 1,425 mL μg⁻¹. The sediment with a higher organic carbon content and a lower pH value had the greatest adsorption capability. Degradation experiment showed that triclosan was relatively stable in water with calculated half-life values ranged from 89 to 161 days. No degradation in sterilized water suggested that the loss of triclosan was due to biological processes. Degradation was more rapid in water-sediment system than in water, and the calculated half-life value in water-sediment systems ranged from 32 to 62 days. Methylation of triclosan was observed in all studied sediments, but the amount of methyl-triclosan (M-TCS) accounted for less than 5 % of the degradated TCS.

Polybrominated diphenyl ethers (PBDEs) are a class of global flame retardants whose residues have markedly increased in fish and human tissues during the last decade. They belong to persistent and toxic contaminants which need more attention and toxicological study as their degradation in the environment is not well understood. This study characterizes 2,2′,4,4′-tetrabromodiphenyl ether (BDE-47) bioconcentration, elimination and biotransformation in juvenile turbot Psetta maxima, in order to evaluate the risk of its bioaccumulation in the marine environment. During this study, juvenile turbot were exposed to environmentally relevant BDE-47 concentrations from 0.001 to 1 μg/L for 16 days via aqueous exposure. This study found that juvenile turbot bioconcentrated and biotransformed BDE-47. There was no difference in standard length or weight between control and exposed fish. Uptake and elimination of BDE-47 by the turbot during exposure were examined in controlled laboratory experiments. Bioconcentration of BDE-47 was similar in fish from all treatment groups. Bioconcentration was rapid and increased with exposure time, since the bioconcentration factor (BCF) was higher. However, elimination was slower in comparison and low elimination was detected after 10 days in clean water. BDE-47 concentration in water influences the BCF. Half-life ranged between 37 and 108 days and theoretical times t₉₀could range from 120 to 358 days. The present study demonstrates a stepwise debromination of BDE-47 to BDE-28.