Environmental Sciences

Effect of amendments on the leaching behavior of alkaline anions and metal ions in bauxite residue Publication date: November 2019 Source: Journal of Environmental Sciences, Volume 85 Author(s): Tao Tian, Jingju Zhou, Feng Zhu, Yuzhen Ye, Ying Guo, William Hartley, Shengguo Xue Abstract A column leaching experiment was used to investigate the efficacy of amendments on their ability to remove alkaline anions and metal ions from bauxite residue leachates. Treatments included, simulated acid rain (AR), phosphogypsum + vermicompost (PVC), phosphogypsum + vermicompost + simulated acid rain (PVA), and biosolids + microorganisms (BSM) together with controls (CK). Results indicated that amendment could effectively reduce the leachate pH and EC values, neutralize OH−, CO32−, HCO3−, and water soluble alkali, and suppress arsenic (As) content. Correlation analysis revealed significant linear correlations with pH and concentrations of OH−, CO32−, HCO3−, water-soluble alkali, and metal ions. BSM treatment showed optimum results with neutralizing anions (OH−, CO32−, and HCO3−), water soluble alkali, and removal of metal ions (Al, As, B, Mo, V, and Na), which was attributed to neutralization from the generation of small molecular organic acids and organic matter during microbial metabolism. BSM treatment reduced alkaline anions and metal ions based on neutralization reactions in bauxite residue leachate, which reduced the potential pollution effects from leachates on the soil surrounding bauxite residue disposal areas. Graphical abstract

Arsenic mobilization from soils in the presence of herbicides Publication date: November 2019 Source: Journal of Environmental Sciences, Volume 85 Author(s): Yuxuan Jiang, Wen Zhong, Wei Yan, Li Yan Abstract Arsenic (As) mobilization in soils is a fundamental step controlling its transport and fate, especially in the presence of the co-existing components. In this study, the effect of two commonly used herbicides, glyphosate (PMG) and dicamba, and two competing ions including phosphate and humic acid, on As desorption and release was investigated using batch and column experiments. The batch kinetics results showed that As desorption in the presence of competing factors conformed to the pseudo-second order kinetics at pH range of 5–9. The impact of phosphate on desorption was greatest, followed by PMG. The competitive effect of dicamba and humic acid was at the same level with electrolyte solution. In situ flow cell ATR-FTIR analysis was performed to explore the mechanism of phosphate and PMG impact on As mobilization. The results showed that PMG promoted As(III) desorption by competiting for available adsorption sites with no change in As(III) complexing structure. On the other hand, phophate changed As(III) surface complexes from bidentate to monodentate structures, exhibiting the most siginficant effect on As(III) desorption. As(V) surface complexes remained unchanged in the presence of PMG and phosphate, implying that the competitive effect for As(V) desorption was primarily determined by the available adsorption sites. Long-term (10 days) soil column experiments suggested that the effect of humic acid on As mobilization became pronounced from 3 days (18 PVs). The insights of this study help us understand the transport and fate of As due to herbicides application. Graphical abstract

Bacterial resistance to lead: Chemical basis and environmental relevance Publication date: November 2019 Source: Journal of Environmental Sciences, Volume 85 Author(s): Qiying Nong, Ke Yuan, Zhuang Li, Ping Chen, Yongshun Huang, Ligang Hu, Jie Jiang, Tiangang Luan, Baowei Chen Abstract Natural bacterial isolates from heavily contaminated sites may evolve diverse tolerance strategies, including biosorption, efflux mechanism, and intracellular precipitation under the continually increased stress of toxic lead (Pb) from anthropogenic activities. These strategies utilize a large variety of functional groups in biological macromolecules (e.g., exopolysaccharides (EPSs) and metalloproteins) and inorganic ligands, including carboxyl, phosphate and amide groups, for capturing Pb. The amount and type of binding sites carried by biologically originated materials essentially determines their performance and potential for Pb removal and remediation. Many factors, e.g., metal ion radius, electronegativity, the shape of the cell surface sheath, temperature and pH, are thought to exert significant influences on the abovementioned interactions with Pb. Conclusively, understanding the chemical basis of Pb-binding in these bacteria can allow for the development of effective microbial Pb remediation technologies and further elucidation of Pb cycling in the environment. Graphical abstract

Effects of imazethapyr spraying on plant growth and leaf surface microbial communities in Arabidopsis thaliana Publication date: November 2019 Source: Journal of Environmental Sciences, Volume 85 Author(s): Wanyue Liu, Mingjing Ke, Zhenyan Zhang, Tao Lu, Youchao Zhu, Yan Li, Xiangliang Pan, Haifeng Qian Abstract Imazethapyr (IM) is an acetolactate synthase (ALS)-inhibiting herbicide that has been widely used in recent years. However, IM spraying can lead to the accumulation of herbicide residues in leaves. Here, we determined the effects of IM spraying on the plant growth and leaf surface microbial communities of Arabidopsis thaliana after 7 and 14 days of exposure. The results suggested that IM spraying inhibited plant growth. Fresh weight decreased to 48% and 26% of the control value after 7 and 14 days, respectively, of 0.035 kg/ha IM exposure. In addition, anthocyanin content increased 9.2-fold and 37.2-fold relative to the control content after 7 and 14 days of treatment, respectively. Furthermore, IM spraying destroyed the cell structures of the leaves, as evidenced by increases in the number of starch granules and the stomatal closure rate. Reductions in photosynthetic efficiency and antioxidant enzyme activity were observed after IM spraying, especially after 14 days of exposure. The diversity and evenness of the leaf microbiota were not affected by IM treatment, but the composition of community structure at the genus level was altered by IM spraying. Imazethapyr application increased the abundance of Pseudomonas, a genus that includes species pathogenic to plants and humans, indicating that IM potentially increased the abundance of pathogenic bacteria on leaves. Our findings increase our understanding of the relationships between herbicide application and the microbial community structures on plant leaves, and they provide a new perspective for studying the ecological safety of herbicide usage. Graphical abstract

Fate of antibiotics and antibiotic resistance genes in a full-scale restaurant food waste treatment plant: Implications of the roles beyond heavy metals and mobile genetic elements Publication date: November 2019 Source: Journal of Environmental Sciences, Volume 85 Author(s): Pinjing He, Zhuofeng Yu, Liming Shao, Yizhou Zhou, Fan Lü Abstract Is our food safe and free of the crisis of antibiotics and antibiotic resistance (AR)? And will the derived food waste (FW) impose AR risk to the environment after biological treatment? This study used restaurant FW leachates flowing through a 200 tons-waste/day biological treatment plant as a window to investigate the fate of antibiotics and antibiotic-resistance genes (ARGs) during the acceptance and treatment of FW. Sulfonamides (sulfamethazine, sulfamethoxazole) and quinolones (ciprofloxacin, enrofloxacin, ofloxacin) were detected during FW treatment, while tetracyclines, macrolides and chloramphenicols were not observable. ARGs encoding resistance to sulfonamides, tetracyclines and macrolides emerged in FW leachates. Material flow analysis illustrated that the total amount of antibiotics (except sulfamethazine) and ARGs were constant during FW treatment processes. Both the concentration and total amount of most antibiotics and ARGs fluctuated during treatment, physical processes (screening, centrifugation, solid–liquid and oil–water separation) did not decrease antibiotic or ARGs concentrations or total levels permanently; the affiliated wastewater treatment plant appeared to remove sulfonamides and most ARGs concentrations and total amount. Heavy metals Ni, Co and Cu were important for disseminating antibiotics concentrations and MGEs for distributing ARGs concentrations. Humic substances (fulvic acids, hydrophilic fractions), C-associated and N-associated contents were essential for the distribution of the total amounts of antibiotics and ARGs. Overall, this study implied that human food might not be free of antibiotics and ARGs, and FW was an underestimated AR pool with various determinants. Nonetheless, derived hazards of FW could be mitigated through biological treatment with well-planned daily operations. Graphical abstract

Effects of typical algae species (Aphanizomenon flosaquae and Microcystis aeruginosa) on photoreduction of Hg2+ in water body Publication date: November 2019 Source: Journal of Environmental Sciences, Volume 85 Author(s): Rongguo Sun, Yafei Mo, Xinbin Feng, Leiming Zhang, Lin Jin, Qiuhua Li Abstract Photoreduction characteristics of divalent inorganic mercury (Hg2+) in the presence of specific algae species are still not well known. Laboratory experiments were conducted in the present study to identify the effects of different concentrations of living/dead algae species, including Aphanizomenon flosaquae (AF) and Microcystis aeruginosa (MA), on the photoreduction rate of Hg2+ under various light conditions. The experimental results showed that percentage reduction of Hg2+ was significantly influenced by radiation wavelengths, and dramatically decreased with the presence of algae. The highest percentage reduction of Hg2+ was induced by UV-A, followed by UV-B, visible light and dark for both living and dead AF, and the order was dark > UV-A > UV-B > visible light for both living and dead MA. There were two aspects, i.e., energy and attenuation rate of light radiation and excrementitious generated from algae metabolisms, were involved in the processes of Hg2+ photoreduction with the presence of algae under different light conditions. The percentage reduction of Hg2+decreased from 15% to 11% when living and dead AF concentrations increased by 10 times (from 106 to 105 cells/mL), and decreased from 11% to ~ 9% in the case of living and dead MA increased. Algae can adsorb Hg2+and decrease the concentration of free Hg2+, thus inhibiting Hg2+ photoreduction, especially under the conditions with high concentrations of algae. No significant differences were found in percentage reduction of Hg2+between living and dead treatments of algae species. The results are of great importance for understanding the role of algae in Hg2+ photoreduction. Graphical abstract

Exposure to low-level metalaxyl impacts the cardiac development and function of zebrafish embryos Publication date: November 2019 Source: Journal of Environmental Sciences, Volume 85 Author(s): Yuqiong Wu, Ying Zhang, Meng Chen, Qihong Yang, Shanshan Zhuang, Liangju Lv, Zhenghong Zuo, Chonggang Wang Abstract Metalaxyl is an anilide pesticide that is widely used to control plant diseases caused by Peronosporales species. In order to study the toxic effects, zebrafish embryos were exposed to metalaxyl at nominal concentrations of 5, 50 and 500 ng/L for 72 hr, and the cardiac development and functioning of larvae were observed. The results showed that metalaxyl exposure resulted in increased rates of pericardial edema, heart hemorrhage and cardiac malformation. The distance between the sinus venosus and bulbus arteriosus, stroke volume, cardiac output and heart rate were significantly increased in larvae exposed to 50 and 500 ng/L metalaxyl compared to solvent control larvae. Significant upregulation in the transcription of tbx5, gata4 and myh6 was observed in the 50 and 500 ng/L treatments, and that of nkx2.5 and myl7 was observed in the 5, 50 and 500 ng/L groups. These disturbances may be related to cardiac developmental and functional defects in the larvae. The activity of Na+/K+-ATPase and Ca2+-ATPase was significantly increased in zebrafish embryos exposed to 500 ng/L metalaxyl, and the mRNA levels of genes related to ATPase (atp2a11, atp1b2b, and atp1a3b) (in the 50 and 500 ng/L groups) and calcium channels (cacna1ab) (in the 500 ng/L group) were significantly downregulated; these changes might be associated with heart arrhythmia and functional failure. Graphical abstract

Efficient adsorption of Mn(II) by layered double hydroxides intercalated with diethylenetriaminepentaacetic acid and the mechanistic study Publication date: November 2019 Source: Journal of Environmental Sciences, Volume 85 Author(s): Mingjie Huang, Yingxin Zhang, Wei Xiang, Tao Zhou, Xiaohui Wu, Juan Mao Abstract In this study, greatly enhanced Mn(II) adsorption was achieved by as-synthesized diethylenetriaminepentaacetate acid intercalated Mg/Al layered double hydroxides (LDHs-DTPA). The adsorption capacity of LDHs-DTPA was 83.5 mg/g, which is much higher than that of LDHs-EDTA (44.4 mg/g), LDHs-Oxalate (21.6 mg/g) and LDHs (28.8 mg/g). The adsorption data of aqueous Mn(II) using LDHs-DTPA could be well described by the pseudo-second order kinetics and Langmuir isotherm model. Thermodynamics study results also showed that the adsorption process of Mn(II) by LDHs-DTPA was exothermic as indicated by the negative ΔH value. Furthermore, based on the structural, morphological and thermostable features, as well as FT-IR and XPS characterizations of LDHs-DTPA and the pristine LDHs, the adsorption mechanism of Mn(II) was proposed. The carboxyl groups of DTPA were proposed to be the main binding sites for Mn(II), and the hydroxyl groups of LDHs also played a minor role in the adsorption process. Among the three common regeneration reagents, 0.1 mol/L Na2CO3 was the best for reusing LDHs-DTPA in Mn(II) adsorption. Besides, the Mn(II) adsorption performance could be hindered in the presence of typical inorganic ions, especially cations. Further specific modifications of LDHs-DTPA are suggested to get more selective adsorption of Mn(II) in practical applications. Graphical abstract

Effect of Ni–V loading on the performance of hollow anatase TiO2 in the catalytic combustion of dichloromethane Publication date: October 2019 Source: Journal of Environmental Sciences, Volume 84 Author(s): Bing Zhou, Xixiong Zhang, Yong Wang, Jing Xie, Kang Xi, Ying Zhou, Hanfeng Lu Abstract A catalyst based on mixed V-Ni oxides supported on TiO2 (Ni–V/TiO2) was obtained using the sol–gel method. Its catalytic performance relative to dichloromethane (DCM) degradation was investigated. Characterization and analysis were conducted using transmission electron microscopy, H2 temperature-programmed reduction, pyridine–Fourier transform infrared spectroscopy (FTIR) characterization, and X-ray diffraction. Results showed that the original hollow anatase structure of pure TiO2 was well-maintained after Ni–V loading. The loading of NiO–VOx not only significantly improved the stability of pure TiO2 but also inhibited the formation of the by-product monochloromethane (MCM). Among the series of Ni–V/TiO2 catalysts, 4%Ni–V/TiO2 possessed the highest catalytic activity, with 90% DCM conversion at only 203°C. No by-products and no significant changes in the catalytic activity were observed during combustion of DCM after 100 hr of a continuous stability test. Furthermore, thermogravimetric analysis (O2-TG) and energy dispersive spectrometer (EDS) characterization of the used 4%Ni–V/TiO2 catalyst revealed that no coke deposition or chlorine species could be detected on the catalyst surface. Graphical abstract

Characteristics and influence factors of NO2 exchange flux between the atmosphere and P. nigra Publication date: October 2019 Source: Journal of Environmental Sciences, Volume 84 Author(s): Chun Chen, Yuzheng Wang, Yuanyuan Zhang, Chengtang Liu, Xiaoxiu Lun, Yujing Mu, Chenglong Zhang, Junfeng Liu Abstract Nitrogen dioxide (NO2) is an important substance in atmospheric photochemical processes and can also be absorbed by plants. NO2 fluxes between the atmosphere and P. nigra seedlings were investigated by a double dynamic chambers method in Beijing from June 15 to September 3, 2017. The range of NO2 exchange fluxes between P. nigra seedlings and the atmosphere was from − 14.6 to 0.8 nmol/(m2·sec) (the positive data represent NO2 emission from trees, while the negative values indicate absorption). Under ambient concentrations, the mean NO2 flux during the fast-growing stage (Jun. 15–Aug. 4) was − 3.0 nmol/(m2·sec), greater than the flux of − 1.5 nmol/(m2·sec) during the later growth stage (Aug. 8–Sept. 3). The daily exchange fluxes of NO2 obviously fluctuated. The fluxes were largest in the morning and decreased gradually over time. Additionally, the NO2 fluxes were larger under high light intensities than under low light intensities during the whole growth period. The effects of temperature on NO2 fluxes were different under two growth periods. The NO2 exchange fluxes were larger in a range of temperatures close to 44°C in the fast-growing stage, whereas there were no evident differences in NO2 exchange fluxes under widely differing temperatures in the later growth stage. Under polluted conditions, the uptake ability of NO2 was weakened. Additionally, the compensation point of NO2 was 5.6 ppb in the fast-growing stage, whereas it was 1.4 ppb in the later growth stage. The deposition velocities of NO2 were between 0.3 and 2.4 mm/sec. Graphical abstract

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