Activity

Bacterial sulfate reduction (BSR) plays a vital but complex role in regulating groundwater arsenic concentration. A quarterly hydro-biogeochemical investigation was conducted to clarify how BSR participated in arsenic dynamics in the geogenic As-contaminated alluvial aquifers of the Jianghan Plain, central Yangtze River Basin. Anthropogenic input of sulfate was identified in the transitional season with higher Cl concentrations and Cl/Br molar ratios compared to the monsoon season. Seasonal increase of S(-II) and Fe(II) concentrations in monsoon season suggests the co-occurrence of iron and sulfate reduction. Quantitative analysis of dsrB gene abundance revealed the corresponding variations between dsrB gene abundance (up to 1.2 × 107 copies L-1) and Fe(II) in groundwater. High-throughput sequencing of the dsrB gene identified a considerable proportion of sequences in the sulfate-reducing bacterial community was affiliated with Desulfobulbus (22.7 ± 20.8%) and Desulfocapsa (11.5 ± 11.9%). Moreover, the relative abundance of Desulfocapsa increased with the Fe(II) in the groundwater (R = 0.78, P less then 0.01). These results suggest that microbially-mediated sulfate reduction facilitated the abiotic reduction of As-bearing Fe-oxides in the monsoon season after anthropogenic input of sulfate in the transitional season under oscillating redox conditions in the groundwater systems. The present research provides new insights into the critical role of BSR in the seasonal redox cycling of iron and variation of As in the aquifer systems, which are not only applicable in the central Yangtze River basin, but also to other similar As-rich alluvial aquifers worldwide.Novel composites of BEA zeolite and silver tungstophosphate were prepared by different procedures two-step impregnation, ion-exchange, and as physical mixtures with varying component mass ratios. Composites were characterized using Atomic force microscopy, Infrared, Raman and Atomic absorption spectroscopy, and results were related to adsorption properties and antimicrobial efficiencies of the composites. Prepared samples were tested as antimicrobial agents for fungal and different bacterial strains, as well as for adsorbents for pesticide nicosulfuron in aqueous solutions by using High-performance liquid chromatography. Experimental conditions for batch adsorption testing were optimized in order to efficiently eliminate nicosulfuron from aqueous solutions, while enabling antimicrobial activity of these advanced materials. Antimicrobial efficiency of composites was verified, and indicated that silver ion persistence in the solid phase is of utmost significance for the antimicrobial activity. Spectroscopic investigation revealed interaction of the silver tungstophosphate active phase and the zeolite framework, giving evidence of uniform distribution of active sites in the synthesized materials that proved to be essential for adsorption application. The best obtained adsorption capacity, as well as highest antimicrobial efficiency, is found for composite samples prepared by two-step impregnation with (BEA silver tungstophosphate) mass ratio 21. The amount of nicosulfuron removed from water suspension was 38.2 mg per gram of composite, and the minimum inhibitory concentration determined for all investigated gram-negative bacteria was 125 μg mL-1.Geosmin (trans-1, 10-dimethyl-trans-9-decalol), a volatile organic compound, has been widely detected in aquatic ecosystems. However, the ecological effects of geosmin are not clear. Here, using zebrafish (Danio rerio) embryo as a model, we investigated biological activity effects of environmentally relevant concentrations (50, 500, 5000 ng/L) of geosmin on the developing zebrafish starting from 2 h post-fertilization (hpf) to 96 hpf. Results showed geosmin had no effect on hatchability, malformations and mortality. However, we observed that geosmin exposure significantly increased zebrafish body length in a concentration dependent manner. This effect was possibly due to up-regulation of expression of genes along the growth hormone/insulin-like growth factor (GH/IGF) axis and hypothalamic-pituitary-thyroid (HPT) axis. In addition, superoxide dismutase (SOD) activities and catalase (CAT) activities significantly increased at 96 hpf when the embryos were exposed to 500 and 5000 ng/L of geosmin. The malondialdehyde (MDA) contents and glutathione S-transferase (GST) activities decreased significantly after the exposure to 5000 ng/L geosmin. Simultaneously, exposure to geosmin resulted in significant increase in cell apoptosis, mainly in the heart area. The mRNA levels of the genes related to oxidative stress and apoptosis were also altered significantly after geosmin exposure. These findings indicated that geosmin can simultaneously induce multiple responses during zebrafish embryonic development, including oxidative stress, apoptosis, and endocrine disruption.Terrestrially-derived dissolved organic carbon (DOC) and nitrogen (DON) transported by rivers have been recognised as contributors to aquatic nutrient burdens, and can be of importance in rivers and estuaries already impacted by anthropogenic inorganic nutrient discharges. The concentration of DOC and DON and the flux of both to the estuary and ultimately the coastal zone is dependent upon many factors including rainfall, catchment land use, and biological processes. DOC and DON concentrations together with nitrate plus nitrite and ammonium concentrations were measured in the anthropogenically-impacted estuary Christchurch Harbour (UK) and at sites in the lower reaches of its two source rivers, the Hampshire Avon and the Stour, at weekly intervals for a year during which time several extreme rainfall events occurred. A series of transects along the estuary were also performed after weekly sampling was completed. DOC concentrations were correlated between both rivers and the estuary and were positively related to increases in river flow, but DON concentrations revealed a more complicated picture. Peak instantaneous fluxes of DOC and DON exceeded 60,000 kg C d-1 and 7000 kg N d-1 respectively both in the Stour and the estuary during high flow periods. The sources of both and routes by which they enter the aquatic system may account for the differences in dynamics, with flushing of superficial soils being a key source of DOC and point sources such as sewage treatment works being proposed as sources of DON. this website Removal processes within the estuary were also of importance for DON concentrations whilst DOC behaved more conservatively with some evidence of local production within the estuary. Estimated annual loads of DON and DOC to the coastal zone from Christchurch Harbour were 118 kg N km-2 y-1 and 2296 kg C km-2 y-1.