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22681. 题目: Using sequential extraction and DGT techniques to assess the efficacy of plant- and manure-derived hydrochar and pyrochar for alleviating the bioavailability of Cd in soils
文章编号: N19051102
期刊: Science of The Total Environment
作者: Lanfang Han, Xingjuan Zhao, Jie Jin, Bo Gao, Yan Yang, Ke Sun, Fangbai Li
更新时间: 2019-05-11
摘要: Biochar has emerged as a useful tool to reduce the bioavailability of heavy metals in contaminated soils. However, limited research has been directed towards determining the effects of pyrolysis conditions and feedstock types of biochar on the bioavailability of heavy metals in biochar-treated soils. This work evaluated the efficacy of plant- and manure-derived hydrochar and pyrochar for alleviating Cd bioavailability in soils using conventional chemical extraction, diffusive gradients in thin films (DGT) and plant uptake. For each feedstock type, hydrochar showed lower maximum adsorption capacity than pyrochar. As determined by diethylenetriamine pentaacetic acid, BCR extraction and DGT measurement, pyrochar significantly decreased the theoretical bioavailability of Cd. Moreover, a slight decrease in the ability of soil to resupply Cd to the solution was detected. Also, pyrochar induced a substantial reduction in Cd uptake in ryegrass. Corresponding to the high sorption capacity, swine solid-derived 450 °C pyrochar was the most effective in alleviating Cd bioavailability in soils, indicating its great potential for remediating Cd-contaminated soils. Additionally, the bioavailable Cd amount determined by DGT had the best correlation with the Cd content in ryegrass, showing that DGT technology could better represent the effects of biochars on Cd phytoavailability in the studied soil.
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22682. 题目: Assessing the provision of carbon-related ecosystem services across a range of temperate grassland systems in western Canada
文章编号: N19051101
期刊: Science of The Total Environment
作者: Majid Iravani, Shannon R. White, Daniel R. Farr, Thomas J. Habib, Jahan Kariyeva, Monireh Faramarzi
更新时间: 2019-05-11
摘要: Reliable data on the provision of ecosystem services (ES) is essential to the design and implementation of policies that incorporate ES into grassland conservation and restoration. We developed and applied an innovative approach for regional parameterization, and calibration of the CENTURY ecosystem model. We quantified spatiotemporal variation of soil organic carbon stock (SOC) and aboveground plant biomass production (AGB) and examined their responses to the recent climate change across a diverse range of native grassland systems in Alberta, western Canada. The simultaneous integration of SOC and AGB into calibration and analysis accounted for most of the spatiotemporal variability in the SOC and AGB measurements and resulted in reduced simulation uncertainty across nine grassland regions. These findings suggest the importance of the systematic parameterization and calibration for the reliable assessment of carbon-related ES across a wide geographic area with heterogeneous ecological conditions. Simulation results showed a pronounced variation in the spatial distribution of SOC and AGB and their associated uncertainty across grassland regions. Under baseline grazing intensity regime, an overall negative effect of recent climatic changes on the SOC, and a less consistent effect on the AGB were found. While, an overall positive or slightly negative impact of recent climate change on the SOC and AGB was found under a proposed 10% lower grazing intensity regime. These heterogeneities in the magnitude and direction of climate change effects under different grazing regimes suggest needs for a range of climate change adaptation strategies to maintain carbon-related ES in Alberta's grasslands. The modeling framework developed in this study can be used to improve the spatially explicit assessment of carbon-related ES in other geographically vast grassland areas and examine the effectiveness of alternative management scenarios to ensure the long-term provision of carbon-related ES in grassland systems.
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22683. 题目: Linking the reclaimed soils and rehabilitated vegetation in an opencast coal mining area: a complex network approach
文章编号: N19051009
期刊: Environmental Science and Pollution Research
作者: Zhaotong Zhang, Jinman Wang, Yu Feng
更新时间: 2019-05-10
摘要: As two main factors, soil and vegetation play key roles in land rehabilitation and ecological remediation of mining areas. There is a complex interaction between soil and vegetation, and understanding the mechanisms of interaction between soil and vegetation is of great significance for land rehabilitation and ecological remediation in mining areas. This study introduced complex network method to analyze the complex interaction systematically. A survey of vegetation and soil properties in 70 reclaimed plots was carried out in the Anjialing and Antaibao opencast coal-mines in Shanxi, China. The indices of soil and vegetation acted as nodes, and the interaction between these indices as sides to establish a soil-vegetation network. Calculating the network indices to analyze the structure of a complex network and explore the mechanism of interaction between soil and vegetation. SOM (soil organic matter) was at the core of the soil-vegetation interaction network. The average path length of the soil-vegetation network was 1.8, with a faster rate of information transfer. The soil-vegetation network consisted of three clusters (soil physical property cluster, soil chemical property cluster, and vegetation cluster), in which the soil chemical property cluster owned the highest clustering coefficient and the largest number of triangles, and it was most stable and the interaction within the cluster was strongest. The soil-vegetation network was stable and the connectivity of the network had robustness to node failures. The scale of the network became larger and the network became tighter and more stable with the increase of reclamation time. Some measures should be conducted to promote vegetation restoration by improving important soil nodes, e.g., surface soil covering, applying organic fertilizer, and planting nitrogen-fixing plants.

22684. 题目: Effects of Ozone on the Photochemical and Photophysical Properties of Dissolved Organic Matter
文章编号: N19051008
期刊: Environmental Science & Technology
作者: Frank Leresche, Garrett McKay, Tyler Kurtz, Urs von Gunten, Silvio Canonica, Fernando L. Rosario-Ortiz
更新时间: 2019-05-10
摘要: This study focused on the effects of ozonation on the photochemical and photophysical properties of dissolved organic matter (DOM). Upon ozonation, a decrease in DOM absorbance was observed in parallel with an increase in singlet oxygen (¹O₂) and fluorescence quantum yields (Φ_1O2 and Φ_F). The increase in Φ_1O2 was attributed to the formation of quinone-like moieties during ozonation of the phenolic moieties of DOM, while the increase in Φ_F can be explained by a significant decrease in the internal conversion rate of the first excited singlet state of the DOM (¹DOM*). It is a consequence of an increase in the average energy of the first electronic transition (S₁ → S₀) that was assessed using the wavelength of maximum fluorescence emission (λ_F,max). Furthermore, ozonation did not affect the ratio of the apparent steady-state concentrations of excited triplet DOM (³DOM*) and ¹O₂, indicating that ozonation does not affect the efficiency of ¹O₂ production from ³DOM*. The consequences of these changes for the phototransformation rates of micropollutants in surface waters were examined using photochemical model calculations. The decrease in DOM absorbance caused by ozonation leads to an enhancement of direct photolysis rates due to the increased transparency of the water. Rates of indirect photooxidation induced by ¹O₂ and ³DOM* slightly decrease after ozonation.
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22685. 题目: Global Meta‐analysis on the Relationship between Mercury and Dissolved Organic Carbon in Freshwater Environments
文章编号: N19051007
期刊: Journal of Geophysical Research: Biogeosciences
作者: Raphael A. Lavoie, Marc Amyot, Jean‐François Lapierre
更新时间: 2019-05-10
摘要: In freshwater ecosystems, several studies have shown a strong linear relationship between total mercury (THg) or methylmercury (MeHg) and dissolved organic carbon (DOC) concentrations. Variations in this linear relationship have been reported, but the magnitude and causes of this variation are not well known. The objective of this study was to conduct a meta‐analysis to quantify and understand the global variation of this mercury (Hg)–DOC association. This meta‐analysis included 54 studies in lentic and lotic ecosystems for a total of 85 THg–DOC and 59 MeHg–DOC relationships. There was an increase in Hg with DOC concentrations in water with a global average slope of 0.25 (confidence interval (CI): 0.20–0.35) ng/mg for THg and 0.029 (CI: 0.014–0.044) ng/mg for MeHg. Relationships were stronger for (1) North American studies; (2) natural environments compared to those disturbed by anthropogenic activities; (3) spatial studies compared to temporal studies; (4) filtered samples (THg only); and (5) the aromatic fraction of DOC compared to the bulk DOC. Coupling with DOC was stronger for THg than for MeHg. Ecosystem type (lentic vs. lotic), geographical coordinates, and publication year did not influence the strength of relationships. Overall we show that there is a strong but variable coupling between carbon and mercury cycles in freshwater ecosystems globally and that this link is modulated regionally by geographic location, temporal scale, and human activity, with implications for understanding these rapidly changing biogeochemical processes in response to global change.

22686. 题目: Initial lignin content is an indicator of predicting leaf litter decomposition and the mixed effects of two perennial gramineous plants in a desert steppe, a five‐year long‐term study
文章编号: N19051006
期刊: Land Degradation & Development
作者: Hao Qu, Chengchen Pan, Xueyong Zhao, Jie Lian, Shaokun Wang, Xinyuan Wang, Xujun Ma, Liangxu Liu
更新时间: 2019-05-10
摘要: Leaf is the main component of litter which often exists in mixed forms in nature. However, the mixed effects of leaf litter decomposition in the desert ecosystems remain unclear. To reveal the mixed effects and the influence of litter quality on leaf litter decomposition in desert ecosystems, a five year long‐term study was conducted to compare the observed and expected leaf litter mass loss in single‐species and mixed (equal proportions and natural proportions) litters of two typical perennial gramineous plants (Stipa klemenzii and Achnatherum splendens) in a desert steppe in northern China. The relationship between litter mass loss and litter qualities was also analyzed. The results showed that: (1) after 5 years of decomposition, the mass losses of mixed litter in natural proportions and Stipa klemenzii litter were significantly higher than those of mixed litter in equal proportions and Achnatherum splendens litter; (2) the mixed effects of two litters in different ratios varied with time, and the synergistic effect only appeared in the second year when an easily decomposed litter (Stipa klemenzii) was mixed with a slowly decomposing litter (Achnatherum splendens); (3) litter mass loss was not correlated with the initial carbon or nitrogen content but was negatively correlated with the initial lignin content, and the initial lignin content also had a significant effect on litter mixed effects of these two perennial gramineous plant litters. These results can suggest that the initial lignin content is an indicator of predicting decomposition and mixed effects of litter with low nitrogen content.

22687. 题目: Influence of reclaimed water irrigation in soil physical properties of urban parks: A case study in Madrid (Spain)
文章编号: N19051005
期刊: CATENA
作者: David Zalacáin, Ramón Bienes, Antonio Sastre-Merlín, Silvia Martínez-Pérez, Andrés García-Díaz
更新时间: 2019-05-10
摘要: Reclaimed water irrigation has been a long-standing practice, especially among water deficit areas such as Spain. This kind of water, more mineralized than drinking water, could imply changes on structural soil features. The main aim of this study was to assess the impact of reclaimed water on aggregate stability, soil penetration resistance, infiltration rate and porosity in soils of one of the urban parks of Madrid. This research was carried out on five successive years (2012–2016) in two urban park plots: one irrigated with reclaimed water (RW) and another one with drinking water (DW).Results showed that irrigation with reclaimed water increased microaggregate stability in the topsoil, probably because of higher values of soil organic matter (SOM). However, macroaggregate stability decreased after RW irrigation in the top and the deepest layer. Soil penetration resistance was significantly higher in the RW plot, probably due to a further development of the root system. Furthermore, a decrease on infiltration rate was observed for RW, apparently because of the influence of sodium. On the other hand, porosity results showed that there was no influence of the kind of irrigation water used. The prolonged use of reclaimed water to irrigate urban parks is potentially leading to a modification of some soil properties, which are key in urban parks soil system. Thus, to avoid future problems, the use of reclaimed water in urban parks irrigation should be continuously monitored.

22688. 题目: Changes in soil carbon pools and components induced by replacing secondary evergreen broadleaf forest with Moso bamboo plantations in subtropical China
文章编号: N19051004
期刊: CATENA
作者: Chuanbao Yang, Huijing Ni, Zheke Zhong, Xiaoping Zhang, Fangyuan Bian
更新时间: 2019-05-10
摘要: Moso bamboo (Phyllostachys edulis) is widely distributed in southern China, and is one of the fastest growing plants worldwide; however, information remains limited on the impact of converting secondary broad-leaved evergreen forests to Moso bamboo plantations, and how the soil organic carbon (SOC) pool and its chemical composition should be managed subsequently. To elucidate these effects, three representative areas were chosen, all with very similar site conditions. In each area, four comparable stands were selected; namely, undisturbed (M0), extensively managed (M1), and intensively managed (M2) stands in each Moso bamboo plantation, and a secondary broad-leaved evergreen forest (CK). Soil samples were collected and examined from depths of 0–20 and 20–40 cm in all 12 stands. The results showed that, SOC and mineral-associated organic matter C (MOM-C) stocks in 0–40 cm soil depths were significantly higher in M0 and M1 than in CK; however, these two parameters were significantly lower in M2. M0 and M1 showed a significant decline in the ratio of microbial biomass C (MBC) to total organic C (TOC), hot-water-extractable organic C (DOC) to TOC, and the C mineralization rate. However, M2 showed a significant increase compared to CK for all of these parameters. Fourier-transform infrared spectroscopy (FTIR) showed that land-use conversion also changed SOC chemical composition. Compared with CK and M2, M0 and M1 showed lower relative content of polysaccharides and higher content of recalcitrant compounds and soil hydrophobicity. Aliphatic and aromatic compounds were positively correlated with accumulated C sequestration in all fractions but negatively correlated with microbial activity in both soil layers; thus, chemical protection mechanism was important for stabilizing the soil in M0 and M1. Overall, Moso bamboo plantations with management strategies M0 and M1 could stabilize more C through promoting the formation of stable organic-mineral complexes and the accumulation of resistant organic components, showing much higher potential in terms of soil C sequestration than M2.

22689. 题目: Anode potentials regulate Geobacter biofilms: New insights from the composition and spatial structure of extracellular polymeric substances
文章编号: N19051003
期刊: Water Research
作者: Guiqin Yang, Lingyan Huang, Zhen Yu, Xiaoming Liu, Shanshan Chen, Jianxiong Zeng, Shungui Zhou, Li Zhuang
更新时间: 2019-05-10
摘要: The extracellular electron transfer (EET) efficiency in bioelectrochemical systems has been proven to be dependent on anode potentials. To explore the underlying mechanism, previous studies have mainly focused on EET conduit and bacterial biomass but rarely concerned with the role of extracellular polymeric substances (EPS) surrounding electroactive cells. In this study, the response of Geobacter biofilms to anode potentials was investigated with a special emphasis on the mechanistic role of EPS. The electrochemical activities and cell viabilities of Geobacter soli biofilms were simultaneously attenuated at 0.4 and 0.6 V compared to −0.2 and 0 V. It was found that the biofilms (especially the biofilm region closer to electrode surface) grown at −0.2 and 0 V produced relatively more extracellular redox-active proteins and less extracellular polysaccharides, which conferred higher electron accepting/donating capacities to EPS and consequently facilitated EET. Meanwhile, electrically nonconductive extracellular polysaccharide-dominated interior layers were formed in the biofilms grown at 0.4 and 0.6 V, which limited direct EET but might serve as physical barriers for protecting cells in these biofilms from the increasing stress by poised electrodes. These results demonstrated that the production of EPS under different anode potentials might be finely regulated by cells to keep balance between EET efficiency and cell-protection. This study provides a new insight to investigate the Geobacter biofilms coping with various environments, and is useful for optimizing electrochemical activity of anode biofilms.
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22690. 题目: Organic matter removal and membrane fouling mitigation during algae-rich surface water treatment by powdered activated carbon adsorption pretreatment: Enhanced by UV and UV/chlorine oxidation
文章编号: N19051002
期刊: Water Research
作者: Jiajian Xing, Heng Liang, Siqi Xu, Chuah Chong Joon, Xinsheng Luo, Tianyu Wang, Jinlong Wang, Guibai Li, Shane A. Snyder
更新时间: 2019-05-10
摘要: In this work, UV and UV/chlorine (UV/Cl) were employed to enhance powdered activated carbon (PAC) adsorption pretreatment prior to ultrafiltration process for algae-contaminated surface water treatment. Their performance on membrane fouling mitigation and organic pollutant rejection was systematically evaluated. A comparative experiment was conducted under varying pollution degrees of algal extracellular organic matter (EOM) contamination in surface river water. The results indicated that UV/PAC and UV/Cl/PAC pretreatment effectively enhanced the removal of dissolved organic carbon (DOC) and UV-absorbing at 254 nm (UV₂₅₄). The characteristics of feed water after pretreatments were investigated through apparent molecular-weight (MW) distribution and fluorescence parallel factor analysis (PARAFAC). In regard to membrane fouling mitigation, UV/Cl/PAC noticeably decreased reversible and irreversible fouling resistance simultaneously and UV/PAC preferred reducing reversible membrane fouling. Combined fouling modeling was operated to scrutinize the fouling mitigation mechanisms and standard pore blocking was proved to be dominant during the filtration process. Moreover, the UV/Cl and UV/Cl/PAC pretreatments were proved positive for emerging micropollutants degradation and disinfection by-products formation potential reduction. The results suggested that UV and UV/Cl are likely strategies to enhance the efficiency of PAC adsorption pretreatments prior to ultrafiltration during algae-contaminated water treatment.
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22691. 题目: Chlorite formation during ClO₂ oxidation of model compounds having various functional groups and humic substances
文章编号: N19051001
期刊: Water Research
作者: Wenhui Gan, Sirong Huang, Yuexian Ge, Tom Bond, Paul Westerhoff, Jiaxin Zhai, Xin Yang
更新时间: 2019-05-10
摘要: Chlorine dioxide (ClO₂) has been used as an alternative to chlorine in water purification to reduce the formation of halogenated byproducts and give superior inactivation of microorganisms. But the formation of chlorite (ClO₂⁻) is a major consideration in the application of ClO₂. In order to improve understanding in ClO₂⁻ formation kinetics and mechanisms, this study investigated the reactions of ClO₂ with 30 model compounds, 10 humic substances and 2 surface waters. ClO₂⁻ yields were found to be dependent on the distribution of functional groups. ClO₂ oxidation of amines, di- and tri-hydroxybenzenes at pH 7.0 had ClO₂⁻ yields >50%, while oxidation of olefins, thiols and benzoquinones had ClO₂⁻ yields <50%. ClO₂⁻ yields from humic substances depended on the ClO₂ dose, pH and varied with different reaction intervals, which mirrored the behavior of the model compounds. Phenolic moieties served as dominant fast-reacting precursors (during the first 5min of disinfection). Aromatic precursors (e.g., non-phenolic lignin or benzoquinones) contributed to ClO₂⁻ formation over longer reaction times (up to 24 h). The total antioxidant capacity (indication of the amount of electron-donating moieties) determined by the Folin-Ciocalteu method was a good indicator of ClO₂-reactive precursors in the water, which correlated with the ClO₂ demand of waters. Waters bearing high total antioxidant capacity tended to generate more ClO₂⁻ at equivalent ClO₂ exposure, but the prediction in natural water should be conservative.

22692. 题目: Influence of individual and combined application of biochar, Bacillus megaterium , and phosphatase on phosphorus availability in calcareous soil
文章编号: N19050920
期刊: Journal of Soils and Sediments
作者: Xiangru Zhang, Haixiao Li, Meng Li, Guoqi Wen, Zhengyi Hu
更新时间: 2019-05-09
摘要: Purpose: Phosphorus (P) in calcareous soil often needs to be replenished repeatedly. P-enriched biochar is expected to improve soil available P. However, the effect of acid biochar incorporated with other P activators on the P availability in calcareous soil is rarely reported. Materials and methods: One soil incubation for 56 days was conducted to investigate the influence of individual application of acid biochar (B), phosphatase (E), Bacillus megaterium (M), and their combined application (BE, BM, EM, BEM) on soil P availability, based on analysis of Olsen-P, water-soluble P, P forms, acid phosphomonoesterase (AcP), alkaline phosphomonoesterase (AlP) activity, and pH after 7, 14, 28, and 56 days of incubation. Results and discussion: Results indicated that individual application of B significantly increased soil Olsen-P and AcP compared with CK in the whole incubation period. Individual application of M significantly increased soil AcP and AlP on the 14th and 56th day of incubation, but decreased soil Olsen-P significantly in the whole incubation. Conclusions: Individual application of B was the best measure for improving P availability in calcareous soil, followed by application of BM. But individual application of E or M was not recommended. Further investigations are required to investigate the influence of acid biochar on P availability in calcareous soil at the field scale.

22693. 题目: Bacterial cell envelope and extracellular sulfhydryl binding s: Their roles in metal binding and bioavailability
文章编号: N19050919
期刊: Chemical Geology
作者: Jeremy B. Fein, Qiang Yu, Justin Nam, Nathan Yee
更新时间: 2019-05-09
摘要: Although carboxyl and phosphoryl functional groups within the bacterial cell envelope and on bacterial extracellular polymeric substance (EPS) molecules are the most abundant metal binding sites, recent studies suggest that sulfhydryl sites control the binding of chalcophile and similar elements under environmentally-relevant metal loading conditions. The role of cell surface sulfhydryl sites in metal binding has been demonstrated unambiguously for Zn, Cd, Hg, Cu, Au, and Se. This review article summarizes our current understanding of the nature, concentration, and reactivity of these important metal binding sites, their distribution between the cell envelope and extractable EPS molecules, and their possible role in controlling bacterial bioavailability of some elements. The objective of the review is to summarize the relatively few studies that have focussed on bacterial sulfhydryl sites, and to identify areas in which future research may be most productive.Sulfhydryl sites comprise only approximately 5–10% of the total binding site concentration of bacterial cell envelopes, but exhibit such a high affinity for some metals that under low metal loading conditions, sulfhydryl binding of metals is responsible for nearly 100% of the adsorbed metal budget. Recent experimental results have revealed that the concentration and distribution of sulfhydryl sites between cell envelope macromolecules and cell-produced EPS are dependent on the bacterial species, growth phase, and growth conditions. For example, the cell envelope sulfhydryl site concentrations of Bacillus subtilis increase with increasing glucose concentration in the growth medium. Shewanella oneidensis cells contain high concentrations of sulfhydryl sites within their cell envelopes with much lower concentrations present on EPS molecules, while Pseudomonas putida cells exhibit the opposite. We apply a proteomics approach to explain the observed differences in sulfhydryl distributions for S. oneidensis and P. putida. The proteomics analysis indicates that the outer membrane proteins of S. oneidensis contains a high concentration of cysteine residues, while the cell surface proteins of P. putida are relatively cysteine-poor, with cysteine-rich proteins of P. putida associated predominately with EPS materials. The results of this proteomics analysis demonstrate the potential to identify the range of possible protein hosts for metal binding sulfhydryl sites, and the approach represents a means for predicting the concentration and distribution of sulfhydryl metal binding sites on bacterial cells and EPS molecules.

22694. 题目: Concurrent transport and removal of nitrate, phosphate and pesticides in low-cost metal- and carbon-based materials
文章编号: N19050918
期刊: Chemosphere
作者: Dongli Tong, Jie Zhuang, Jaehoon Lee, John Buchanan, Xijuan Chen
更新时间: 2019-05-09
摘要: Low-cost magnesium- and/or carbon-based materials have a great potential to remove soluble contaminants from surface and ground water. This study examined mechanisms that control the removal of nitrate, phosphate and pesticides (tricyclazole, malathion and isoprothiolane) during their transport through calcined magnesia (MgO) and corn stalk biochar. Various miscible column breakthrough experiments were carried out and morphology and crystallographic structures of reactive materials were examined. Approximately 96% (78,950 mg-NO₃^-/kg) and 48% (27,455 mg-NO₃^-/kg) of nitrate were removed from biochar and MgO columns, respectively. Chemical adsorption dominated nitrate removal during early phase (i.e., <11 PVs for biochar and <100 PVs for MgO, respectively), and microbial denitrification dominated during the following phase. 92% of the applied phosphate (6168 mg-PO₄^3-/kg) was removed in MgO column, while much less in biochar column (4%, 347 mg-PO₄^3-/kg). Mineral surface analyses confirmed that electrostatic attraction, ligand exchange, and chemical precipitation were responsible for phosphate removal. For the three pesticides, biochar exhibited larger removal capacity (1260–2778 mg/kg) than MgO (28–2193 mg/kg) due to the functional groups on biochar. The removal of pesticides based on their physico-chemical properties. Malathion had highest removal rate (98–100%), attributing to chemical sorption and bio-degradation, followed by isoprothiolane (47–79%) and tricyclazole (6–64%).

22695. 题目: The microbial mercury link in oligotrophic lakes: Bioaccumulation by picocyanobacteria in natural gradients of dissolved organic matter
文章编号: N19050917
期刊: Chemosphere
作者: Carolina Soto Cárdenas, Claudia Queimaliños, Sergio Ribeiro Guevara, Marina Gerea, María C. Diéguez
更新时间: 2019-05-09
摘要: Andean Patagonian lakes are oligotrophic systems characterized by low dissolved organic carbon (DOC) levels and moderate to high Hg concentration that determine naturally high Hg/DOC ratios and bioavailability. In these lakes, microbial food webs are extremely important in Hg trophodynamics, being that the picophytoplankton fraction is a major entrance path of Hg²⁺ into pelagic food webs. This study analyzed the bioaccumulation of Hg²⁺ by the picocyanobacteria Synechococcus sp. using the radiotracer ¹⁹⁷Hg²⁺ and water from four Andean Patagonian lakes presenting a natural gradient of DOM concentration and quality. Hg²⁺ bioaccumulation by Synechococcus was calculated as the uptake of Hg²⁺ per biovolume unit (volume concentration factor VCF; pL μm⁻³). Hg uptake showed a wide variation (13 < VCF< 300 pL μm⁻³) in the natural DOC gradient tested (0.7–4 mg L⁻¹; Hg²⁺/DOC ratio; 1.8–14 ng mg⁻¹). The bioaccumulation of Hg²⁺in Synechococcus decreased exponentially with DOC concentration. Differences in the quality of dissolved organic matter (DOM) among lake water influenced also Hg²⁺ bioaccumulation. Naturally degraded DOM, with low molecular weight/size, promoted higher Hg uptakes in Synechococcus compared to humic DOM, rich in high molecular weight/size aromatic compounds, that retained Hg in the dissolved phase. In Andean Patagonian lakes picocyanobacteria are pivotal organisms in the Hg cycling, taking dissolved Hg²⁺ and transferring it to pelagic food webs, as well as fueling the benthic Hg pathway through sedimentation.
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22696. 题目: The role of soil components in synthetic mixtures during the adsorption and speciation changes of Cr(VI): Conjunction of the modeling approach with spectroscopic and isotopic investigations
文章编号: N19050916
期刊: Environment International
作者: Veronika Veselská, Hana Šillerová, Jörg Göttlicher, Zuzana Michálková, Jamal A. Siddique, Sylva Číhalová, Vladislav Chrastný, Ralph Steininger, Stefan Mangold, Michael Komárek
更新时间: 2019-05-09
摘要: This study investigates redox transitions associated with the adsorption of Cr(VI) on commonly occurring soil components (silicates, oxides and humic acids) and their synthetic mixtures by coupling the mechanistic surface complexation modeling with spectroscopic and isotopic analyses. The mixtures of soil components were prepared to reflect the composition of the real anthroposol sample, determined by X-ray Powder Diffraction (XRD), total organic carbon (TOC) measurement and extraction methods. The effect of different initial Cr(VI) concentrations (2 × 10⁻², 5 × 10⁻⁴, 10⁻⁴, 10⁻⁵, and 10⁻⁶ M), background electrolyte (10⁻³, 10⁻², and 10⁻¹ M KNO₃), pH values (3–9), and sorbate/sorbent ratios (2 g/L - 20 g/L) were investigated. Maghemite and ferrihydrite were confirmed to be the main phases controlling Cr(VI) adsorption with increasing Cr(VI) concentration. Humic acids were primarily responsible for Cr(VI) reduction, especially at low pH values. The reduction of Cr(VI) was also proved in case of illite and kaolinite by XAS and isotopic analyses. Illite revealed higher reduction capacity in comparison with kaolinite based on XAS measurements. Chromium isotopic fractionation, resulting from Cr(VI) reduction, was the highest in the case of humic acids, followed by kaolinite and illite. However, a dissolution of intrinsic Cr originally present within kaolinite and illite might affect the final Cr isotopic composition of the supernatants due to its different Cr isotopic signature. In general, the combination of three different approaches was confirmed to offer more comprehensive information about Cr(VI) adsorption and/or reduction in soils. Detailed studies using soil mixtures can help to predict how the soil components affect Cr(VI) behavior in natural soils and possibly could improve the environmental remediation processes.
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22697. 题目: Empowering conventional Rock-Eval pyrolysis for organic matter characterization of the siderite-rich sediments of Lake Towuti (Indonesia) using End-Member Analysis
文章编号: N19050915
期刊: Organic Geochemistry
作者: Luis Ordoñez, Hendrik Vogel, David Sebag, Daniel Ariztegui, Thierry Adatte, James M. Russell, Jens Kallmeyer, Aurèle Vuillemin, André Friese, Sean A. Crowe, Kohen W. Bauer, Rachel Simister, Cynthia Henny, Sulung Nomosatryo, Satria Bijaksana, the Towuti Drilling Project Scientific Team
更新时间: 2019-05-09
摘要: Qualitative and quantitative changes of organic and carbonate carbon in sedimentary records are frequently used to reconstruct past environments, paleoproductivity and sediment provenance. Amongst the most commonly used proxies are Total organic carbon (TOC), Mineral carbon (MinC), as well as Hydrogen (HI) and Oxygen Indices (OI) of organic matter (OM). Rock Eval pyrolysis enables the assessment of these quantitative and qualitative parameters with a single analysis. This is achieved through transient pyrolysis of the samples up to 650°C followed by combustion up to 850°C, with hydrocarbons, CO and CO₂ measured during the thermal decomposition of both OM and carbonate minerals.Carbonate minerals with low thermal cracking temperatures such as siderite (<400°C) can induce significant matrix effects, which bias the TOC, MinC and OI Rock-Eval parameters. Here we assess the applicability of End-Member Analysis (EMA) as a means to correct Rock-Eval thermograms for siderite matrix effects. For this, we performed Rock-Eval pyrolysis on sideritic sediments of Lake Towuti (Indonesia). New thermal boundaries were constrained in Rock-Eval thermograms using EMA to limit siderite matrix effects and improve TOC, MinC, and OI calculations. Our approach allowed us to: 1) evaluate the influence of siderite matrix effects on Rock-Eval thermograms; 2) properly exploit a Rock-Eval dataset to characterize the type and sources of OM in siderite-rich sediments; and 3) identify the OM behind degradation and mineralization processes. The Rock-Eval dataset revealed sediments with a substantial amount of refractory OM, especially in those where TOC is high and HI characteristic of autochthonous biomass. These results, associated to alternative indices used to assess OM preservation, suggest that refractory OM is residually enriched following strong degradation of labile compounds. Finally, relatively labile and refractory organic fractions may be consumed in the formation of siderite during this sequential process of OM mineralization.

22698. 题目: Applying a dynamic membrane filtration (DMF) process for domestic wastewater preconcentration: Organics recovery and bioenergy production potential analysis
文章编号: N19050914
期刊: Science of The Total Environment
作者: Jiaqing Xiong, Shichun Yu, Yisong Hu, Yuan Yang, Xiaochang C. Wang
更新时间: 2019-05-09
摘要: Wastewater is increasingly recognized as a valuable resource rather than as a waste, motivating a shift in the perspective of wastewater treatment from pollution control to resource recovery. This study proposes the recovery of organic matter from domestic wastewater for the production of bioenergy through a novel process of wastewater preconcentration based on dynamic membrane filtration (DMF). The selection of a dynamic membrane (DM) supporting material, the preconcentration performance of organics, and the biomethane production potential (BMP) of the organic concentrate were investigated. The process optimization results indicated that a DM module with a supporting material of a 25 μm stainless steel mesh with a three-layer structure, assisted by internal suspended particles derived from raw wastewater, enabled the rapid DM layer formation within 1 h. The DMF process operated under a constant high flux of 30–60 L/m² h at a trans-membrane pressure (TMP) of less than 40 kPa. During the continuous DMF operation, the average chemical oxygen demand (COD) of the influent, effluent and concentrate was 305, 113 and 2000–2500 mg/L, respectively, while the removal performance of other pollutants(such as nitrogen and phosphorus) varied, indicating differential retention effects for the various pollutants by the DM layer. Air back-flushing can effectively regenerate the DM layer and maintain long-term stable operation, but higher rates of TMP increase were observed for later filtration cycles, probably due to the accumulation of physically irremovable fouling. The BMP of the DMF concentrate was 0.20 L CH₄/g COD, which was comparable to the ordinary biogas yield from municipal wastewater by anaerobic digestion. The DMF process integrated with anaerobic digestion can be a promising alternative for energy-sufficient wastewater treatment.
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22699. 题目: A review on mercury biogeochemistry in mangrove sediments: Hotspots of methylmercury production
文章编号: N19050913
期刊: Science of The Total Environment
作者: Pei Lei, Huan Zhong, Dandan Duan, Ke Pan
更新时间: 2019-05-09
摘要: Wetlands are highly productive and biologically diverse environments that provide numerous ecosystem services, but can also be sources of methylmercury (MeHg) production and export. Mangrove wetlands contribute up to 15% of the coastal sediment carbon storage and ~10% of the particulate terrestrial carbon exported to the ocean. Thus, mercury (Hg) methylation in mangrove sediments and subsequent MeHg output to adjacent waters could have a great impact on global Hg cycling. In this review, we provide a comprehensive analysis of the literature on worldwide Hg concentrations in mangrove ecosystems, and the results reveal that a large range of total Hg (THg) and MeHg concentrations is detected in mangrove systems. Then, we discuss the potential roles of organic matter (OM) in controlling the Hg biogeochemistry in mangrove sediments. The intense OM decomposition by anoxic reduction (e.g., sulfate reduction) drastically affects sediment chemistries, such as redox potential, pH, and sulfur speciation, all of which may have a great impact on MeHg production. While the outwelling of carbon from mangroves has been extensively examined, little is known about their roles in exporting MeHg to adjacent waters. Our understanding of Hg biogeochemical processes in mangrove systems is constrained by the limited MeHg data and a lack of in-depth studies on the Hg methylation potential in this ecologically important environment. More efforts are needed to gain better insights into the contributions mangrove wetlands to the global Hg cycle.
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22700. 题目: Effects of forest harvest and fertiliser amendment on soil biodiversity and function can persist for decades
文章编号: N19050912
期刊: Soil Biology and Biochemistry
作者: S.L. Addison, S.J. Smaill, L.G. Garrett, S.A. Wakelin
更新时间: 2019-05-09
摘要: Effective management is critical to the establishment and growth of productive and sustainable planted forest ecosystems. Harvesting and nutrient applications can significantly disturb these ecosystems, and long-term studies are critical to evaluating the impacts of these events on the factors that contribute to sustainability. This study used long-term field trial sites to explore the direct and interactive effects of site, management, and other factors on the biogeochemical processes and phylogenetic diversity (bacterial and fungal community composition) within forest soil ecosystems. High throughput sequencing of bacterial (16S rRNA) and fungal (ITS rRNA) phylogenetic marker genes was used to characterise microbial communities in soils from two long-term soil productivity study (LTSP) sites (both >25 years old). The single species (Pinus radiata) trials, at Woodhill and Tarawera forests, allowed for testing of effects of forest management practices, including organic matter removal at harvest and fertiliser addition, on microbial communities. Addition of fertiliser resulted in distinct changes to both bacterial and fungal communities, while organic matter removal at harvest had persistent effects on the composition of fungal species in the soil ecosystem at Woodhill with smaller magnitude effects still seen at Tarawera. In contrast, there was no evidence of long-term effects related to organic matter removal at harvest on the composition of soil bacterial communities, irrespective of site. The two sites had differing soil physicochemical properties and these were also associated with location-based differences in bacterial communities. Overall, bacterial communities were relatively impervious to forest management practices, whereas fungal communities were responsive and the effects on community assemblage were enduring over time. This outcome highlights both the importance of investigating fungal and bacterial communities together in forest ecosystems, and the value of long-term field-based studies. We conclude that while conventional forestry management practices may improve the long-term physicochemical conditions and tree growth, their impacts on soil microbial populations are also enduring.