Antibiotic resistant bacteria/genes dissemination in lacustrine sediments highly increased following cultural eutrophication of Lake Geneva (Switzerland)

This study investigates faecal indicator bacteria (FIB), multiple antibiotic resistant (MAR), and antibiotic resistance genes (ARGs), of sediment profiles from different parts of Lake Geneva (Switzerland) over the last decades. MARs consist to expose culturable Escherichia coli (EC) and Enterococcus (ENT) to mixed five antibiotics including Ampicillin, Tetracycline, Amoxicillin, Chloramphenicol and Erythromycin. Culture-independent is performed to assess the distribution of ARGs responsible for, β-lactams (blaTEM; Amoxicillin/Ampicillin), Streptomycin/Spectinomycin (aadA), Tetracycline (tet) Chloramphenicol (cmlA) and Vancomycin (van). Bacterial cultures reveal that in the sediments deposited following eutrophication of Lake Geneva in the 1970s, the percentage of MARs to five antibiotics varied from 0.12% to 4.6% and 0.016% to 11.6% of total culturable EC and ENT, respectively. In these organic-rich bacteria-contaminated sediments, the blaTEM resistant of FIB varied from 22% to 48% and 16% to 37% for EC and ENT respectively, whereas the positive PCR assays responsible for tested ARGs were observed for EC, ENT, and total DNA from all samples. The aadA resistance gene was amplified for all the sediment samples, including those not influenced by WWTP effluent water. Our results demonstrate that bacteria MARs and ARGs highly increased in the sediments contaminated with WWTP effluent following the cultural eutrophication of Lake Geneva. Hence, the human-induced changing limnological conditions highly enhanced the sediment microbial activity, and therein the spreading of antibiotic resistant bacteria and genes in this aquatic environment used to supply drinking water in a highly populated area. Furthermore, the presence of the antibiotic resistance gene aadA in all the studied samples points out a regional dissemination of this emerging contaminant in freshwater sediments since at least the late nineteenth century.     

Photocatalytic oxidation of monuron in the suspension of WO3 under the irradiation of UV-visible light

A comprehensive study of the degradation of monuron, one of the phenylurea herbicides, was conducted by UV-Vis/WO₃ process. It was found that hydroxyl radicals played a major role in the decay of monuron while other radicals (e.g. superoxide) and hole might also contribute to the decomposition of monuron. The oxidation path likely plays a major role in the generation of hydroxyl radicals. The effects of initial pH level, initial concentration of monuron, and inorganic oxidants on the performance of UV-Vis/WO₃ process were also investigated and optimized. Comparison between monuron decay pathways by UV-Vis/WO₃ and UV/TiO₂ was conducted. The decay mechanisms, including N-terminus demethylation, dechlorination and direct hydroxylation on benzene ring, were observed to be involved in the oxidation of monuron in these two processes. Sixteen intermediates were identified during the photodegradation of monuron and degradation pathways were proposed accordingly.     

Transformation of tetrabromobisphenol A in the presence of different solvents and metals

Solvent-based separation method is presumably an efficient and environmentally beneficial approach for elimination of brominated flame retardants (BFRs) from waste electrical and electronic equipment (WEEE). The overall goal of this study was to evaluate possible effects of organic solvent on the behavior of BFRs during solvent-based processing of WEEE. We initiated a set of batch experiments for examining the rates and possible pathways of transformation of a representative BFR (tetrabromobisphenol A, TBBPA) using acetone, toluene, and methanol as the solvents. Our results showed that toluene and methanol had no effect on the transformation of TBBPA, but approximately 20% of TBBPA (100 mg L⁻¹) was transformed by acetone within 2 h at 50 °C. Analysis of the products with GC-MS showed that two high-molecular-weight products (MW = 586) were major products of the transformation reactions. The role of acetone as a reactant in the transformation of TBBPA was further validated with dueterated acetone. In addition, the effects of co-existing metals in WEEE (i.e., Zn, Cu, and Ni) on the transformation of TBBPA in the solvent systems were investigated. These metals tested were found to greatly enhance the rates of TBBPA transformation. The metal facilitated solvent reactions with TBBPA may lower the extractability of TBBPA by formation of larger and less soluble products, hence potentially increasing the cost for separating the chemical from WEEE.     

Phytoavailability and geospeciation of cadmium in contaminated soil remediated by Rhodobacter sphaeroides

A microorganism was isolated from oil field injection water and identified as Rhodobacter sphaeroides. It was used for the remediation of simulated cadmium-contaminated soil. The phytoavailability of Cd was investigated through wheat seedling method to determine the efficiency of remediation. It was found that after remediation, the accumulation of Cd in wheat roots and leaves decreased by 67% and 53%, respectively. The Cd speciation in soil was determined with Tessier extraction procedure. It was found that the total Cd content in soil did not change during the experiments, but the geo-speciation of Cd changed remarkably. Among the five fractions, the concentration of exchangeable phases decreased by 27-46% and that of the phases bound to Fe-Mn oxides increased by 22-44%. The decrease of Cd accumulation in wheat showed significant positive correlation with the decrease of exchangeable phases. It could be concluded that the remediation of R. sphaeroides was carried out through the conversion of Cd to more stable forms. The decrease of sulfate concentration in supernatant indicated that the R. sphaeroides consumed sulfate.     

Toxicological effect of MPA-CdSe QDs exposure on zebrafish embryo and larvae

Cadmium selenium (CdSe) quantum dots (QDs) are semiconductor nanocrystals that hold wide range of applications and substantial production volumes. Due to unique composition and nanoscale properties, their potential toxicity to aquatic organisms has increasingly gained a great amount of interest. However, the impact of CdSe QDs exposure on zebrafish embryo and larvae remains almost unknown. Therefore, the lab study was performed to determine the developmental and behavioral toxicities to zebrafish under continuous exposure to low level CdSe QDs (0.05-31.25 mg L⁻¹) coated with mercaptopropionic acid (MPA). The results showed MPA-CdSe exposure from embryo to larvae stage affected overall fitness. Our findings for the first time revealed that: (1) The 120 h LC₅₀ of MPA-CdSe for zebrafish was 1.98 mg L⁻¹; (2) embryos exposed to MPA-CdSe resulted in malformations incidence and lower hatch rate; (3) abnormal vascular of FLI-1 transgenic zebrafish larvae appeared after exposure to MPA-CdSe including vascular junction, bifurcation, crossing and particle appearance; (4) larvae behavior assessment showed during MPA-CdSe exposure a rapid transition from light-to-dark elicited a similar, brief burst and a higher basal swimming rate; (5) MPA-CdSe induced embryos cell apoptosis in the head and tail region. Results of the observations provide a basic understanding of MPA-CdSe toxicity to aquatic organisms and suggest the need for additional research to identify the toxicological mechanism.     

Identification of priority pharmaceuticals in the water environment of China

In recent years, increasing attention has been paid to the trace-level contamination of pharmaceuticals in the water environment all over the world. Considering a large number of pharmaceuticals used, it is crucial to establish a priority list of pharmaceuticals that should be monitored and/or treated first. In the present study, we developed a ranking system based on the pharmaceutical consumption, removal performance in the wastewater treatment plants (WWTPs) and potential ecological effects, and applied to the situation of China. 39 pharmaceuticals, which had available consumption data and also been reported previously in the WWTPs of China, were selected as candidate pharmaceuticals. Among them, seventeen pharmaceuticals were considered as priority pharmaceuticals, out of which, erythromycin, diclofenac acid and ibuprofen, had the high priority. Compared with other literatures, we found that some pharmaceuticals given concerns to globally should also be included in the priority list in China; while some pharmaceuticals, not mentioned in other literatures, such as cefalexin, ketoconazole, should be also given prior consideration in China. Among all the therapeutic classes, antibiotics, which were grossly abused in China, contributed the most to the priority pharmaceuticals. However, priority antibiotics accounted for only 32% of candidate antibiotics, while 71% and 100% of the candidate anti-inflammatory and antilipidemic respectively were identified as the priority pharmaceuticals, indicating that antibiotics might be overanxiously considered in the previous studies on their behaviors in the WWTPs of China.     

Ozonation as an advanced oxidant in treatment of bamboo industry wastewater

The present study employed ozonation process to treat the bamboo industry wastewater (BIWW). The impact of ozone dosage and initial organic concentration on color, COD and TOC removal rates were studied along with characterization of the major organics in raw and treated wastewater. The results suggested the ozone dosage of 3.15 g h⁻¹ (concentration 52.5 mg L⁻¹) was suitable for the treatment. After 25 min ozonation of 1 L raw wastewater, the color, COD and TOC removal efficiencies were 95%, 56% and 40%, respectively, with an influent COD concentration of 835 mg L⁻¹. The ratio of kg O₃ kg⁻¹ COD at 3.15 g h⁻¹ was 2.8 (<3), revealing that ozonation was a cost effective process for tertiary treatment of BIWW. Longer oxidization time was required to achieve similar results for raw wastewater with higher COD concentration. The chromatogram from gel permeation chromatography revealed that ozonation resulted in the breakdown of high molecular weight compounds into lower molecular weight components but could not completely mineralize the organic matter. The majority of these compounds were identified in both raw and ozonated samples via GC-MS analysis. In addition to ester derivatives as the main intermediates of ozonation, 1-chloroctadecane, methyl stearate, benzophenone and α-cyperone were identified as the by-products of ozonation.     

Changes in the pore network structure of Hanford sediment after reaction with caustic tank wastes

At the former nuclear weapon production site in Hanford, WA, caustic radioactive tank waste leaks into subsurface sediments and causes dissolution of quartz and aluminosilicate minerals, and precipitation of sodalite and cancrinite. This work examines changes in pore structure due to these reactions in a previously-conducted column experiment. The column was sectioned and 2D images of the pore space were generated using backscattered electron microscopy and energy dispersive X-ray spectroscopy. A pre-precipitation scenario was created by digitally removing mineral matter identified as secondary precipitates. Porosity, determined by segmenting the images to distinguish pore space from mineral matter, was up to 0.11 less after reaction. Erosion-dilation analysis was used to compute pore and throat size distributions. Images with precipitation had more small and fewer large pores. Precipitation decreased throat sizes and the abundance of large throats. These findings agree with previous findings based on 3D X-ray CMT imaging, observing decreased porosity, clogging of small throats, and little change in large throats. However, 2D imaging found an increase in small pores, mainly in intragranular regions or below the resolution of the 3D images. Also, an increase in large pores observed via 3D imaging was not observed in the 2D analysis. Changes in flow conducting throats that are the key permeability-controlling features were observed in both methods.