Geogenic and anthropogenic activities introduce certain metals into the environment which tend to deteriorate the quality of both surface and groundwater in the Bosomtwe Crater Lake and its surroundings. In this study spatio-temporal variations in concentrations and risk assessment of selected trace metals (As, Fe, Pb, Zn, Cr, Cd and Ni) were investigated during the wet and dry seasons for surface and groundwater in selected human settlements around the lake. The levels of As, Cd and Ni were generally small and were below the detection limit of the instrument. The results showed no significant seasonal variations in the mean levels of Pb, Fe, Zn and Cr in water from the Bosomtwe Crater Lake. The hazard quotients and health hazard indices through ingestion and dermal contact of lake and groundwater in towns around the lake for both adults and children gave values which were below the acceptable limit of less than unity (< 1), indicating the absence of non-carcinogenic health risk to the communities. The study however reveals that ingestion of both lake and groundwater from the lake and its surroundings poses carcinogenic risk with regard to the level of Pb and Cr. Hence appropriate control measures and interventions should be put in place to protect the health of the human population in the study area.

The chemistry of group II-VI semiconductors has spurred considerable interest in decomposition reaction mechanisms and has been exploited for various technological applications. In this work, computational chemistry was employed to investigate the possible gas-phase decomposition pathways of the mixed Cd[((i)Pr)2PSSe]2 single-source precursor for the chemical vapour deposition of cadmium chalcogenides as thin films. The geometries of the species involved were optimised by employing density functional theory at the MO6/LACVP* level. The results indicate that the steps that lead to CdS formation on the singlet potential energy surface are favoured kinetically over those that lead to CdSe and ternary CdSe(x)S(1-x) formation. On the doublet PES, the steps that lead to CdSe formation are favoured kinetically over those that lead to CdS and CdSe(x)S(1-x) formation. However, thermodynamically, the steps that lead to ternary CdSe(x)S(1-x) formation are more favourable than those that lead to CdSe and CdS formation on both the singlet and the doublet PESs. Density functional theory calculations revealed that the first steps exhibit huge activation barriers, meaning that the thermodynamically favourable process takes a very long time to initiate.

Background: Geogenic and anthropogenic activities such as Artisanal and illegal gold mining continue to have negative impacts on the environment and river basins in China. This work studied the hydrogeochemical characteristics of surface water from the Birim River basin and assess the quality of water for human consumption and agricultural activities. In addition, the ecological risk assessment for Cd, Zn, Pb and As in sediment was evaluated using pollution indices. Results:The results show that the turbidity, temperature, colour and iron concentration in the water samples were above the World Health Organization guidelines. Multivariate analysis explained five components that accounted for 98.15% of the overall hydrogeochemistry and affected by anthropogenic and geogenic impacts. The surface water was observed to range from neutral to mildly acidic, with the dominance of HCO 3, and Na + in ionic strength. The Piper diagram reveals five major surface water types: Na-HCO 3 -Cl, Na-Cl-HCO 3 , Na-Ca-Mg-HCO 3 , Na-Ca-Mg-HCO 3 and Ca-Na-Mg-HCO 3 . The Gibbs plot showed that the major ion chemistry of surface water was mostly influenced by atmospheric precipitation and the water quality index showed that the majority of the surface water from settlements within the Birim River basin were of poor quality for drinking and other domestic purposes. However, irrigation suitability calculations with reference to sodium adsorption ratio, residual sodium carbonate, and magnesium ratio values, together with Wilcox and USSL models indicated that the surface water within the area under study was suitable for agriculture. The potential ecological risk for single heavy metals pollution and potential toxicity response indices gave low to considerable ecological risks for the sediments, with greater contributions from Cd, Pb and As. Whilst geo-accumulation indices indicated that the sediments ranged from unpolluted to moderately polluted Modified degree of pollution and Nemerow pollution index calculations which incorporate multi-element effects, however, indicated no pollution. Conclusion:There are some levels of both potential ecological risks and health hazards in the study area. Hence continuous monitoring should be undertaken by the relevant agencies and authorities so that various interventions could be put in place to prevent the situation from deteriorating further in order to protect the inhabitants of the settlements within the Birim River basin.

Background: Mercury (Hg) used in gold amalgamation is a major source of contamination in developing countries. The present study evaluates the concentrations of total mercury in water, sediment and fish from the Ankobra and Tano Rivers, which drain the major gold mining areas in Ghana. Total mercury (T-Hg) analysis was carried out using an atomic absorption spectroscopy (Perkin Elmer model 5100PC) equipped with a flow injection analysis system (FIAS, AS-90). Results:Water, sediment and fish T-Hg concentrations were 0.145-1.078 μg/L, 23.39-73.31, and 0.03-0.443 μg/g dw, respectively in Ankobra basin, while in Tano basin levels of 0.214-0.250 μg/L, 14.43-21.51, 0.068-0.413 μg/g were found for water, sediment and fish, respectively. The T-Hg concentration in water from both basins were within the World Health Organization threshold limits for drinking water except at River Asuo Kofi. Concentration of T-Hg in the sediment exceeded Environmental Protection Agency ecotoxicological threshold in some sampling stations, suggesting potential adverse ecological effects. T-Hg levels in fish from both basins were lower than the WHO value (<0.500 μg/g (wet wt). The target hazard quotient values, suggest that human should minimizing meals/week of the analyzed species to avoid deleterious effect during lifetime. Conclusions:The results suggested that mining activities significantly contribute to the considerable environmental Hg contamination in both Ankobra and Tano River basins. Therefore Hg levels should carefully monitored and controlled to reduce its inputs and mitigate potential health consequences of Hg accumulation in the environment.

A suitable electronic structure and efficient charge separation are significant for the performance of photocatalytic water splitting. Herein, we have designed a two-dimensional GeI2/C2N van der Waal (vdW) heterostructure and...