Roxithromycin (ROX) is a widely used macrolide antibiotic and its environmental fate and ecotoxicity have attracted considerable attention. In this study, the phototransformation kinetics and products of ROX under the irradiation of simulated sunlight were investigated. The ecotoxicity of ROX before and after phototransformation were also examined using the bioluminescence bioassay and algae growth inhibition test. The results showed that ROX underwent direct photolysis and indirect photolysis in the presence of Suwannee River humic acid (SRHA) and Suwannee River natural organic matter (SRNOM). The kinetic rate constant of the photodegradation of ROX in the presence of 20 mg·L-1 SRHA and SRNOM were 4.0 and 3.6 times higher than direct photolysis in the absence of dissolved organic matter (DOM). A total of 20 phototransformation products (PTPs) formed as a result of the photodegradation of ROX by simulated solar irradiation were identified, and 10 of them were reported for the first time. The PTPs were generally formed through the N-demethylation, O-demethylation or direct cleavage of the side chain, desosamine or cladinose moiety from ROX. Solutions containing ROX and its PTPs showed an increased toxicity to Vibrio fischeri, demonstrating some PTPs were more toxic to V. fischeri. On the other hand, the toxicity of ROX after irradiation to Chlorella pyrenoidosa decreased, suggesting the phototransformation of ROX in the environment may be a positive outcome in the context of the growth of green algae.Marine mussels are key ecological engineers that form dense aggregations to maintain the vital habitat in benthic systems. It is essential to understand the consequences of mussel byssus attachment in elevated temperatures associated with ocean warming. We evaluated byssus production and the mechanical performance of threads in the mussel Mytilus coruscus at 21° (control), 27 °C (average temperature in the M. coruscus habitat during the summer season) and 31 °C (4 °C raised) for 72 h. We quantified byssus secretion and shedding number, measured byssal breaking force, byssal polyphenol oxidase (PPO) activity, byssal thread length and diameter. Expression of byssus foot protein genes was analyzed by quantitative real-time PCR in foot tissue. High seawater temperature decreased the number of newly secreted byssus and the diameter of byssal threads, leading to the reduction of byssal breaking force and the alteration of the weakest part of the thread. Increased breakpoints in the upper part of the thread (proximal region) were higher at 27 °C than at 21 °C. High-temperature stress significantly reduced the PPO activity in byssus at 31 °C in comparison to 21 °C. The expression of mussel foot protein genes was affected by elevated temperature. The increased gene expression of byssus collagen-like protein 2 (Mccol2) at 31 °C conflicted with the number of byssuses produced. Suggesting the reduction of mussel foot protein abundance is not the cause of decreased byssus production at 31 °C. These results show that byssus, as an extracellular structure of mussels, may be highly susceptible to the adverse effects of ocean warming.This study analysed the chemistry of water samples collected from mires in the south-eastern part of Western Siberia. The aim was to determine spatial and temporal patterns in the hydrochemistry of mires in relation to the environmental conditions and geological history of the region. The results show that concentrations of Fetotal, Са2+, Mg2+, Na+, and HCO3- ions are higher than those obtained in other regions of Russia and Europe, which is consistent with the geological conditions of Western Siberia. High Fetotal concentrations are associated with the distribution of sedimentary ore in the region's largest iron ore basin, the Bakchar deposit, which is represented by strata of various Cretaceous sedimentsary rock at depths of 150-200 m. The Fe-rich rocks contribute to the high Fe concentrations in deep groundwater that feeds into the fens. The increase in Са2+, Mg2+, Na+, Cl-, and HCO3- in the water resulted from a xerothermic period that occurred in the southern part of Western Siberia (4500-2500 years ago) that increased the carbonation and salinity of the rocks. A feature characteristic of the hydrochemical regime in raised bogs is the transformation of the chemical composition during the year, with a change in dominant anions from HCO3- to Cl- or SO42-. The water in transitional mires and rich fens were characterised by the predominance of HCO3- and Са2+. https://www.selleckchem.com/products/ag-825.html Studies have shown that the size and stage of development play leading roles in the formation of the water chemistry in the mires. Small bogs and transitional mires were characterised by a rich mineral nutrition; while, the chemical composition of fens was mainly determined by their geomorphologic position and proximity to large river systems. The results of this study provide a better understanding of the functions of peatland ecosystems in Western Siberia and improve water sampling strategies for future research.Agricultural landscapes are often affected by groundwater quality issues due to fertilizers leaching. To address this worldwide problem several agricultural best practices have been proposed, like limiting the amount of fertilizers and increasing soil organic matter content. To evaluate if these practices may promote groundwater quality enhancement, vadose zone retention time and complex biogeochemical processes must be known in detail. In this study, sequential undisturbed column experiments were performed to determine the amount of nutrients and heavy metals leached after simulated stormwater events. The column was amended with urea then flushed for two pore volumes, then straw residuals were incorporated and flushed for two pore volumes and finally compost was incorporated and flushed for six pore volumes. Dissolved ions, major gasses and heavy metals were determined in leachate samples. Nitrate and nitrite were leached in the urea treatment producing the highest concentrations, followed by compost and straw residuals. The redox conditions were aerobic in all treatments and pH was circumneutral or slightly basic. Denitrification was low but increased with the addition of straw residuals and compost. Heavy metals were all at very low concentrations except for lead and cadmium, which slightly exceeded threshold limits (10 and 1 μg/L, respectively) in all the treatments. The compost treatment, after three pore volumes, was affected by clay swelling due to sodium dispersion, which in turn provoked a reduction of porosity and hydraulic conductivity.


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Last-modified: 2025-01-23 (木) 06:01:32 (22d)