论文检索

总访问量：439529次

总访客量：23155人

所有论文

1. 题目: Biochar and effective microorganisms promote Sesbania cannabina growth and soil quality in the coastal saline-alkali soil of the Yellow River Delta, China
文章编号: N20112708
期刊: Science of The Total Environment
作者: Qian Cui, Jiangbao Xia, Hongjun Yang, Jingtao Liu, Pengshuai Shao
更新时间: 2020-11-27
摘要: Soil salinization and nutrient deficiency have emerged as the major factors negatively impacting soil quality and primary productivity in the coastal saline-alkali soil of the Yellow River Delta. Biochar has been proposed as an efficient strategy for promoting plant growth and restoring degraded saline-alkali soil. However, knowledge is inadequate regarding the effects of adding Spartina alterniflora-derived biochar alone or in combination with effective microorganisms (EM) on the growth of Sesbania cannabina and soil quality in saline-alkali soil. To enhance this knowledge, a pot experiment with different EM treatments (without EM addition, EM-; with EM addition, EM+) and a gradient of biochar treatments (0%, B0; 0.5%, B1; 1.5%, B2; and 3%, B3; biochar weight/soil weight) was conducted. Our results showed that biochar addition alone and in combination with EM significantly increased seed germination, plant height, stem diameter, total biomass and plant nutrient uptake of S. cannabina. Biochar addition, EM addition and their interaction significantly decreased soil salt content efficiently and increased soil total carbon (TC), total nitrogen (TN), available phosphorus (AP) and available potassium (AK) but had little effect on soil pH. Biochar addition increased soil organic carbon, soil NH4+ and NO3-, microbial biomass carbon, and soil enzyme activities and these effects increased in strength when biochar and EM were present simultaneously. Of the treatments, the EM+B3 treatment had the largest effects in terms of inhibiting salinization, increasing soil fertility, elevating soil nutrients and enzyme activities, and improving plant growth. Moreover, the application of biochar and EM promoted the growth of S. cannabina by enhancing plant nutrient uptake, improving soil fertility (e.g., TN, AP, AK, NH4+ and NO3-), and elevating soil enzyme activities (urease and alkaline phosphatase activity). Overall, the integrated use of an appropriate biochar rate (3%) and EM for coastal saline-alkali soil could be an effective strategy to ameliorate soil salinity, improve soil quality and promote plant productivity.

2. 题目: A meta-analysis of heavy metal bioavailability response to biochar aging: importance of soil and biochar properties
文章编号: N20112707
期刊: Science of The Total Environment
作者: Chengpeng Yuan, Baolin Gao, Yutao Peng, Xing Gao, Beibei Fan, Qing Chen
更新时间: 2020-11-27
摘要: Biochar has been widely applied to remediate the heavy metal-polluted soils, whereas biochar aging can induce the changes of the biochar physic-chemical properties. Afterwards, the bioavailability of heavy metals (BHM) will vary in soils which likely increase the unstable fractions of heavy metals and the following environmental risks. To explore the biochar aging effects on the BHM changes in responses to the variation of experimental conditions and biochar properties, a meta-analysis for the literatures published before May 2020 was conducted. A sum of 257 independent observations from 22 published papers was obtained. The results from the analysis of boosted regression tree showed that the soil pH was the most important factor influencing the BHM changes in biochar amended soil, followed by soil texture, aging time and biochar pyrolysis temperature. The results of this review showed that the BHM was decreased by 16.9%, 28.7% and 6.4% in weakly acid soil (pH 6.00 - 6.99), coarse- and medium-textured soils, respectively, but increased by 149% and 121% in the alkaline (pH > 8.00) and fine-textured soils. The BHM declined in the soils amended with biochar pyrolyzed at relative high temperature (> 500 °C), and increased during aging in soils amended with biochar pyrolyzed at relatively low temperature (401-500 °C). In terms of diverse immobilized heavy metals, only bioavailable Zn in soil decreased after aging. However, there was no significant changes in Cd, Cu and Pb’s bioavalability. Besides, the BHM was decreased by 18.6% within the short-term (less than one year) biochar aging, while showed inverse trend during the longer aging processes. Besides, the application of lignin-enriched biochar may counteract the positive effects of the biochar aging on BHM. Our works may promote the interpretation of the interference factors on the BHM changes and filled the research gaps on biochar aging process in soils.

3. 题目: Efficient removal of volatile organic compound by ball-milled biochars from different preparing conditions
文章编号: N20112706
期刊: Journal of Hazardous Materials
作者: Zhicheng Zhuang, Lan Wang, Jingchun Tang
更新时间: 2020-11-27
摘要: Adsorption is an important technology to deal with volatile organic compounds (VOCs), and biochar has attracted much attention as a new type of adsorbent for VOCs. In this study, rice husk, corn stover and pine wood sawdust biochars from different pyrolysis temperatures (300°C, 500°C and 700°C) were synthesized and treated by ball milling. The pristine and ball-milled biochars were used as adsorbents for acetone and toluene removal. Results showed that wood biochar had higher adsorption capacity for VOCs. After ball milling, the BET specific surface area and the oxygen functional group content of biochars increased. With these changes, all the ball-milled biochars showed higher adsorption rate than the pristine biochars. The ball-milled biochars under pyrolysis temperature of 300°C showed the best adsorption performance for acetone (304 mg g-1), which was 1.7- fold greater than that of pristine biochar. Increasing the surface area by ball milling is conducive to the diffusion of hydrophobic VOCs molecules such as toluene to the adsorption sites in the biochar. However, for hydrophilic VOCs such as acetone, higher oxygen functional groups were the main reason for the enhanced adsorption by ball milling. Therefore, ball-milled biochar can be used as a potential adsorbent material in VOCs treatment.

4. 题目: Canopy mitigates the effects of nitrogen deposition on soil carbon-related processes in a subtropical forest
文章编号: N20112705
期刊: Science of The Total Environment
作者: Xiaofei Lu, Yuanwen Kuang, Linyun Mou, Enqing Hou, Shenglei Fu, Jianlong Li
更新时间: 2020-11-27
摘要: The rapid increases in atmospheric nitrogen (N) deposition have greatly affected the carbon (C) cycles of terrestrial ecosystems. Most studies concerning on the effects of N deposition have simulated N deposition by directly applying N to the understory and have therefore not accounted for the possibility of N absorption, retention, and transformation by the canopy. In this study, we compared the effects of understory addition of N (UN), canopy addition of N (CN) at 25 and 50 kg N ha−1 yr−1, and ambient addition of N (CK) on soil carbon-related processes in a subtropical forest. After seven years of addition, the contribution of new C from litter (Fnew) was more than 2× greater with UN treatments than with CN treatments. UN treatments significantly increased the activity of β-1,4-glucosidase (BG) but reduced the activities of β-1,4-N-acetylglucosaminidase (NAG), polyphenol oxidase (PPO), and peroxidase (PER). CN treatments, in contrast, did not alter the activities of extracellular enzyme. Compared to CN, UN treatments significantly enhanced soil organic carbon (SOC) and mean weight diameter (MWD, represents soil aggregate stability). Differences in the responses of SOC and MWD to CN and UN treatments were positively correlated with Fnew but negatively correlated with the activities of PPO and PER. The results imply that forest canopy mitigates the effects of atmospheric N inputs on SOC, and that conventional understory N addition might overestimate the positive effects of N deposition on forest soil C-related processes. We suggest that CN rather than UN should be used to simulate the effects of atmospheric N deposition on soil C dynamics in subtropical forests.

5. 题目: Accumulation and influencing factors of novel brominated flame retardants in soil and vegetation from Fildes Peninsula, Antarctica
文章编号: N20112704
期刊: Science of The Total Environment
作者: Siyuan Xiong, Yanfen Hao, Yingming Li, Ruiqiang Yang, Zhiguo Pei, Qinghua Zhang, Guibin Jiang
更新时间: 2020-11-27
摘要: The concentrations and distributions of nine novel brominated flame retardants (NBFRs) were analyzed in soil, lichen (Usnea aurantiaco-atra), and moss (Sanionia uncinata) samples collected from the Chinese Antarctic Great Wall Station and surrounding Fildes Peninsula area in west Antarctica. Total NBFR concentrations ranged from 61.2–225 pg/g dry weight (dw) in soil, 283–1 065 pg/g dw in moss, and 135–401 pg/g dw in lichen, respectively. Decabromodiphenyl ethane (DBDPE) was the dominant NBFR in all samples, accounting for 65.2%, 50.1%, and 72.4% of cumulative NBFR concentration in soil, lichen, and moss, respectively. The concentrations of NBFRs in plant samples were higher than those in soil, which may be related to plant bioaccumulation. Significant log/log-linear correlations (p < 0.05) were found between the concentrations of BEHTEBP and total organic carbon (TOC) in soil, and between DBDPE and lipid content in mosses, indicating that TOC and lipid content potentially affect certain NBFRs in Antarctic soil and moss. This study presents the first report on NBFR contamination in soil and various vegetation in Antarctica.

6. 题目: Hydrogen peroxide and persulfate activation using UVA-UVB radiation: degradation of estrogenic compounds and application in sewage treatment plant waters
文章编号: N20112703
期刊: Journal of Hazardous Materials
作者: Anaëlle Gabet, Hélène Métivier, Christine de Brauer, Gilles Mailhot, Marcello Brigante
更新时间: 2020-11-27
摘要: In the present work, the degradation of three estrogens (17β-estradiol (E2), estrone (E1) and 17α-ethinylestradiol (EE2)) was investigated under photoactivation of hydrogen peroxide and persulfate. Lab-scale irradiation experiments showed that both UVA and UVB radiations are able to photoactivate the oxidant precursors, although UVB is more efficient to generate radicals and therefore to degrade the targets. The efficiency of both oxidant precursors was investigated showing higher efficiency in the system with persulfate. The pseudo-first order degradation rate constants and the second order rate constants between the hydroxyl or the sulfate radicals and estrogens were measured. In order to evaluate the process efficiency in real treatment conditions, the degradation of the estrogens spiked into sewage treatment plant effluent was studied. Measurements of second order rate constants between the radical and the effluent organic matter by laser flash photolysis allowed to understand the involved quenching mechanisms. A Yeast Estrogen Screen (YES) assay was used to follow the decrease in estrogenic activity during the estrogen degradation. This assay permitted to ensure that the studied processes are not only able to degrade the estrogens but also to remove their estrogenic activity.

7. 题目: Impact of fertilization with pig slurry on the isotopic composition of nitrate retained in soil and leached to groundwater in agricultural areas
文章编号: N20112702
期刊: Applied Geochemistry
作者: Rosanna Margalef-Marti, Alba Llovet, Raúl Carrey, Angela Ribas, Xavier Domene, Stefania Mattana, Juan Chin-Pampillo, Claudio Mondini, Josep Ma Alcañiz, Albert Soler, Neus Otero
更新时间: 2020-11-27
摘要: The isotopic composition of N and O of nitrate (NO3-) is usually employed to trace its sources of pollution in groundwater. In agricultural areas, the amount of NO3- that reaches the aquifers after fertilization is controlled by different transformation processes that can affect the nitrogen species isotopic composition. Aiming to address the reliability of using isotope tools to trace sources of groundwater NO3-, the goal of this study was to check the effect of fertilization on the isotopic composition of N compounds retained and leached from soils. The concentration and isotopic composition (δ15N and δ18O) of ammonium (NH4+), NO3- and nitrite (NO2-) was characterized after the application of pig slurry in lysimeters containing either soil under fallow (LF) or the same soil continuously cropped and fertilized (LC) during the previous six years. Results showed that the leached NO3- isotopic signature did not directly reflect the isotopic composition of the applied pig slurry. Just after fertilization, nitrification led to lower δ15NNO3 values in soil extracts and leachates (e.g. from +5.9±0.9 ‰ to +3.8±3.1 ‰ in soil extracts of LF lysimeters). These values increased after complete nitrification (+11.5±1.3 ‰) towards the δ15Nbulk of pig slurry (+19.6±0.5 ‰). Later on, due to soil organic matter and plant debris mineralization and subsequent nitrification, values decreased towards the initial δ15NNO3 of soil but remained above them (+8.6±1.0 ‰). Both LF and LC experiments showed a similar trend and the latter ones allowed to reinforce that long-term fertilization with pig slurry can increase the soil δ15NNO3. Concerning the δ18O of NO3- from soil extracts and leachates, it mainly depended on the δ18O of irrigation water and oxygen, after nitrification of NH4+ from pig slurry. Therefore, studies aiming to trace groundwater NO3- pollution sources in rural areas by using an isotopic approach should consider the fertilization history of each setting. Also, analyzing the δ15Nbulk of soil is recommended, since it could mask the isotopic signature of the N applied through fertilization.

8. 题目: Electron shuttles facilitate anaerobic methane oxidation coupled to nitrous oxide reduction in paddy soil
文章编号: N20112701
期刊: Soil Biology and Biochemistry
作者: Yaohong Zhang, Fangyuan Wang, Zhongjun Jia
更新时间: 2020-11-27
摘要: Anaerobic oxidation of methane (AOM) coupled with simultaneous consumption of nitrous oxide (N2O) has been recently reported, but the underlying coupling mechanism remains unclear. Here, we investigated N2O-mediated AOM in paddy soil under amendment of electron shuttles (anthraquinone-2,6-disulphonate and methylviologen). Sixty-day anaerobic incubation showed that N2O-mediated AOM occurred in paddy soil, and that electron shuttles stimulated AOM coupled to N2O reduction. Approximate 60% of 13CH4-C was converted into soil organic matter in paddy soil during anaerobic oxidation. Our results suggest that electron shuttles may play important roles in mitigating the emission of greenhouse gases (CH4 and N2O) and increasing organic matter in paddy soils.

9. 题目: Quantification of organic aerosol and brown carbon evolution in fresh wildfire plumes
文章编号: N20112610
期刊: Proceedings of the National Academy of Sciences
作者: Brett B. Palm, Qiaoyun Peng, Carley D. Fredrickson, Ben H. Lee, Lauren A. Garofalo, Matson A. Pothier, Sonia M. Kreidenweis, Delphine K. Farmer, Rudra P. Pokhrel, Yingjie Shen, Shane M. Murphy, Wade Permar, Lu Hu, Teresa L. Campos, Samuel R. Hall, Kirk Ullmann, Xuan Zhang, Frank Flocke, Emily V. Fischer, Joel A. Thornton
更新时间: 2020-11-26
摘要: The evolution of organic aerosol (OA) and brown carbon (BrC) in wildfire plumes, including the relative contributions of primary versus secondary sources, has been uncertain in part because of limited knowledge of the precursor emissions and the chemical environment of smoke plumes. We made airborne measurements of a suite of reactive trace gases, particle composition, and optical properties in fresh western US wildfire smoke in July through August 2018. We use these observations to quantify primary versus secondary sources of biomass-burning OA (BBPOA versus BBSOA) and BrC in wildfire plumes. When a daytime wildfire plume dilutes by a factor of 5 to 10, we estimate that up to one-third of the primary OA has evaporated and subsequently reacted to form BBSOA with near unit yield. The reactions of measured BBSOA precursors contribute only 13 ± 3% of the total BBSOA source, with evaporated BBPOA comprising the rest. We find that oxidation of phenolic compounds contributes the majority of BBSOA from emitted vapors. The corresponding particulate nitrophenolic compounds are estimated to explain 29 ± 15% of average BrC light absorption at 405 nm (BrC Abs 405 ) measured in the first few hours of plume evolution, despite accounting for just 4 ± 2% of average OA mass. These measurements provide quantitative constraints on the role of dilution-driven evaporation of OA and subsequent radical-driven oxidation on the fate of biomass-burning OA and BrC in daytime wildfire plumes and point to the need to understand how processing of nighttime emissions differs.

10. 题目: Early snowmelt and sea ice breakup enhance algal export in the Beaufort Sea
文章编号: N20112609
期刊: Progress in Oceanography
作者: Gabrielle Nadaï, Eva-Maria Nöthig, Louis Fortier, Catherine Lalande
更新时间: 2020-11-26
摘要: Microalgal cells collected with moored sediment traps deployed during three to five annual cycles at three sites in the Beaufort Sea were identified to investigate variations in the timing, abundance and composition of microalgal fluxes in relation to snow and sea ice cover. The investigation period encompassed two extremes in snow and sea ice conditions: a delayed melt due to an ice rebound in 2013 and a premature snowmelt and sea ice breakup that led to an ice-free Beaufort Sea in 2016. Diatoms dominated the microalgal fluxes, with the pelagic centric diatoms Thalassiosira spp. and the ice-associated pennate diatoms Fragilariopsis spp. consistently collected at the three sites. The export of the ice-obligated algae Nitzschia frigida indicated the release of sea ice algae at the onset of snowmelt. Early snowmelt and sea ice breakup in 2016 contributed to an early start of ice algae release accompanied with early peaks in diatom fluxes and higher diatom and phytoplankton carbon (PPC) fluxes during spring and summer. Conversely, delayed sea ice algae release, low diatom fluxes, and low PPC fluxes were observed when snowmelt and sea ice breakup occurred late over the Mackenzie shelf break. The amount of diatoms exported at ∼100 to 300 m also likely depended on a match or mismatch between algal production and zooplankton grazing. Variations in the snow and sea ice regimes at the regional scale therefore directly impact the timing and magnitude of microalgal export and its contribution to particulate organic carbon flux in the Arctic Ocean. With global warming, the ongoing sea ice reduction in the Arctic Ocean may increase PPC fluxes to the seafloor and potential carbon sequestration at depth.

11. 题目: Enhanced technology based for sewage sludge deep dewatering: A critical review
文章编号: N20112608
期刊: Water Research
作者: Bingdi Cao, Tao Zhang, Weijun Zhang, Dongsheng Wang
更新时间: 2020-11-26
摘要: Sludge is an inevitable by product of sewage treatment, and it includes pathogens, heavy metals, organic pollutants and other toxic substances. The components of sludge are complex and variable with extracellular polymeric substances (EPS) being one. EPS are highly hydrophilic and compressible, and make sludge dewatering difficult. Therefore, the development of efficient sludge-dewatering technology is an important means of mitigating rapid sludge growth. At present, the main methods used for sludge deep-dewatering technology are chemical preconditioning with high-pressure filtration and electrical mechanical dewatering. The selection of chemical preconditioning directly determines the final efficiency of the sludge-dewatering process. In this paper, we conduct a comprehensive review of the problems related to sludge dewatering and systematically summarise the impact of different chemical conditioning technologies on the efficiency of sludge dewatering. Furthermore, the characteristics of different enhanced dewatering technologies are evaluated and analysed for their adaptability and final disposal methods. We believe that this review can clarify the chemical conditioner mechanism to improve sludge dewatering, provide reference debugging information for the sludge-dewatering process and promote the development of efficient and environmentally friendly sludge-dewatering technology.

12. 题目: Soil organic carbon stocks maintained despite intensification of shifting cultivation
文章编号: N20112607
期刊: Geoderma
作者: Thilde Bech Bruun, Casey M. Ryan, Andreas de Neergaard, Nicholas J. Berry
更新时间: 2020-11-26
摘要: Shifting cultivation systems of Southeast Asia are rapidly intensifying, especially through shortening of the fallow periods. It is typically assumed that intensification will result in a depletion of soil organic carbon (SOC) stocks, but existing estimates of carbon stocks in these systems are variable, and there is little certainty about the carbon outcomes of intensification. We investigated the effects of intensification on SOC stocks of a shifting cultivation system in northern Laos. Volume-specific soil samples were collected from 20 sites representing: i) various rotation intensities (fallow periods of 3–4 years and 7–10 years), ii) various stages of the rotation cycle (fallows and active fields) and iii) reference plots (old regrowth of 25–30 years). Samples were analyzed for SOC, soil texture, pH, Total Nitrogen and permanganate oxidizable carbon (POXC) – an active carbon fraction that has been suggested as an easily measured early indicator of land use induced changes in soil quality and SOC. There were no significant differences between SOC concentrations or stocks of any of the sites under shifting cultivation and the reference sites. However, the SOC stock under fallows in the intensive rotation category was significantly larger than the SOC stock under fallows in the extensive rotation category. This is likely because inputs of dead root biomass from the slashed vegetation provides an important input to the SOC pool. Fallow sites under intensive rotation had significantly higher contents of POXC in the topsoil than the active fields, which suggests that POXC captures the immediate effect of the decreased input of litter to the topsoil during the cultivation period. We conclude that in this study there is no evidence that intensification of shifting cultivation leads to a decline in total soil carbon stock, or to a decline in the more active carbon fraction measured by POXC. Therefore, narratives of shifting cultivation leading to a decline in soil carbon stocks need to be revisited, and land use policies related to the system should not uncritically be based on this incorrect assumption.

13. 题目: From rock eating to vegetarian ecosystems — Disentangling processes of phosphorus acquisition across biomes
文章编号: N20112606
期刊: Geoderma
作者: Moritz Koester, Svenja C. Stock, Francisco Nájera, Khaled Abdallah, Anna Gorbushina, Jörg Prietzel, Francisco Matus, Wantana Klysubun, Jens Boy, Yakov Kuzyakov, Michaela A. Dippold, Sandra Spielvogel
更新时间: 2020-11-26
摘要: Low-molecular-weight organic acids (LMWOAs) are crucial for the mobilization and acquisition of mineral phosphorus by plants. However, the role of LMWOAs in mobilizing organic phosphorus, which is the predominant phosphorus form in at least half of the world's ecosystems, especially in humid climates, is unclear. The mechanisms of phosphorus mobilization by LMWOAs depend on climate, mainly precipitation, and shape the phosphorus nutrition strategies of plants. We disentangled the impact of roots and associated microorganisms on mechanisms of phosphorus cycling mediated by LMWOAs by studying soils along an ecosystem-sequence (ecosequence) from arid shrubland (~70 mm yr−1), and Mediterranean woodland (~370 mm yr−1) to humid-temperate forest (~1470 mm yr−1). Phosphorus speciation in soil was examined by X-ray absorption near edge structure analysis (XANES). LMWOAs were quantified as biological rock-weathering and organic phosphorus mobilization agents and compared to kinetics of acid phosphatase as a proxy for organic phosphorus mineralization. Calcium-bound phosphorus in topsoils decreased from 126 mg kg−1 in the arid shrubland, to 19 mg kg−1 in the Mediterranean woodland and was undetectable in the humid-temperate forest. In contrast, organic phosphorus in topsoils in close root proximity (0–2 mm distance to roots) was absent in the arid shrubland but raised to 220 mg kg−1 in the Mediterranean woodland and to 291 mg kg- 1 in the humid-temperate forest. The organic phosphorus content in topsoils was 1.6 to 2.4 times higher in close root proximity (0–2 mm distance to roots) compared to bulk soil (4–6 mm distance to roots) in the Mediterranean woodland and humid-temperate forest, showing intensive phosphorus bioaccumulation in the rhizosphere. Redundancy analysis (RDA) revealed that LMWOAs were explained by the content of hydroxyapatite and variscite phosphorus-species in the arid shrubland, indicating that LMWOAs contribute to mineral weathering in this soil. LMWOA contents, phosphatase activity, and microbial biomass carbon correlated strongly with organic phosphorus in the humid-temperate forest soil, which implies a high relevance of LMWOAs for organic phosphorus recycling. In the Mediterranean woodland soil, however, oxalic acid correlated with organic phosphorus in the topsoil (suggesting phosphorus recycling), whereas in the subsoil malic and citric acid were correlated with primary and secondary phosphorus minerals (implying mineral weathering). We conclude that phosphorus acquisition and cycling depend strongly on climate and that the functions of LMWOAs in the rhizosphere change fundamentally along the precipitation gradient. In the arid shrubland LMWOAs facilitate biochemical weathering (rock eating), while in the humid-temperate forest their functions change towards supporting organic phosphorus recycling (vegetarian).

14. 题目: Multi-proxy approach involving ultrahigh resolution mass spectrometry and self-organising maps to investigate the origin and quality of sedimentary organic matter across a subtropical reservoir
文章编号: N20112605
期刊: Organic Geochemistry
作者: Erik S.J. Gontijo, Peter Herzsprung, Oliver J. Lechtenfeld, Carolina de C. Bueno, Johannes A.C. Barth, Andre H. Rosa, Kurt Friese
更新时间: 2020-11-26
摘要: Humic substances (HS) in sediments play an important role in carbon and nutrient biogeochemical cycles and fate of contaminants in the environment. However, information regarding HS quality and transformations that may affect their behaviour in reservoirs is still limited. The aim of this investigation was to track sources and changes in sedimentary HS across a subtropical reservoir, connecting them to in-lake processes and land-use influences. Surface sediments were collected at seven sampling sites in Itupararanga Reservoir (Brazil). Humic (HA) and fulvic (FA) acids (components of HS) were extracted from the sediment samples followed by in-depth characterisation via UV/VIS, fluorescence spectroscopy, elemental (C, N) and isotopic analysis (δ13C, δ15N), nuclear magnetic resonance (13C NMR) and Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). All data were analysed by self-organising maps. The results showed that samples from the upstream part of the reservoir were older and more decomposed. They likely originated from C3 land-plants (δ13C varied from −26.3‰ to −22.4‰), having more aromatic, oxygen-poor (O/C < 0.5) and unsaturated compounds (H/C < 1.1). In contrast, near-dam samples were younger and had larger contributions of autochthonous material. This was confirmed by oxygen-rich (O/C > 0.5) and partly more unsaturated compounds for FA as well as oxygen-poor and saturated compounds with H/C > 1.1 for HA. Self-organising maps pointed out these differences between upstream and dam areas and indicated that agriculture lands were related to microbially-derived HS. Changes in HS composition revealed that internal reservoir processes may have influenced HS quality across the reservoir.

15. 题目: Mechanisms for simultaneous ozonation of sulfamethoxazole and natural organic matters in secondary effluent from sewage treatment plant
文章编号: N20112604
期刊: Frontiers of Environmental Science & Engineering
作者: Xinshu Liu, Xiaoman Su, Sijie Tian, Yue Li, Rongfang Yuan
更新时间: 2020-11-26
摘要: Sulfamethoxazole (SMX) is commonly detected in wastewater and cannot be completely decomposed during conventional treatment processes. Ozone (O3) is often used in water treatment. This study explored the influence of natural organic matters (NOM) in secondary effluent of a sewage treatment plant on the ozonation pathways of SMX. The changes in NOM components during ozonation were also analyzed. SMX was primarily degraded by hydrolysis, isoxazole-ring opening, and double-bond addition, whereas hydroxylation was not the principal route given the low maximum abundances of the hydroxylated products, with m/z of 269 and 287. The hydroxylation process occurred mainly through indirect oxidation because the maximum abundances of the products reduced by about 70% after the radical quencher was added, whereas isoxazole-ring opening and double-bond addition processes mainly depended on direct oxidation, which was unaffected by the quencher. NOM mainly affected the degradation of micropollutants by consuming •OH rather than O3 molecules, resulting in the 63%–85% decrease in indirect oxidation products. The NOM in the effluent were also degraded simultaneously during ozonation, and the components with larger aromaticity were more likely degraded through direct oxidation. The dependences of the three main components of NOM in the effluent on indirect oxidation followed the sequence: humic-like substances>fluvic-like substance-s>protein-like substances. This study reveals the ozonation mechanism of SMX in secondary effluent and provides a theoretical basis for the control of SMX and its degradation products in actual water treatment.

16. 题目: Long-Term Warming Decreases Redox Capacity of Soil Organic Matter
文章编号: N20112603
期刊: Environmental Science & Technology Letters
作者: Rachelle E. LaCroix, Nicolas Walpen, Michael Sander, Malak M. Tfaily, Jeffrey L. Blanchard, Marco Keiluweit
更新时间: 2020-11-26
摘要: Globally rising temperatures increase microbial activity, accelerating decomposition of soil organic matter (SOM). SOM has numerous functional capabilities, of which the capacity to engage in reduction–oxidation reactions (or redox capacity) affects nearly all soil biogeochemical processes. How warming-induced microbial decomposition affects the redox capacity of SOM and its functional role in biogeochemical processes is largely unknown. We examined the impact of 15 years of in situ soil warming on the redox capacities of water-extractable organic matter (WEOM). Combining mediated electrochemical analysis with high-resolution mass spectrometry, we assessed the molecular basis for changes in the redox capacities of WEOM within heated (5°C above ambient) and non-heated organic and mineral temperate forest soils. Chronic soil warming significantly decreased both concentrations and inherent electron-accepting and -donating capacities of WEOM, particularly in the mineral soil. This decline was best explained by decreases in the relative abundance of aromatic and phenolic compounds, suggesting that enhanced microbial decomposition of redox-active moieties caused the decrease in redox capacity. Our findings suggest that global warming not only diminishes the size of the soil carbon reservoir but might also negatively alter the ability of SOM to participate in critical redox processes such as microbial respiration, nutrient cycling, or contaminant degradation.

17. 题目: Superoxide and Nitrous Acid Production from Nitrate Photolysis Is Enhanced by Dissolved Aliphatic Organic Matter
文章编号: N20112602
期刊: Environmental Science & Technology Letters
作者: Xinke Wang, Evan Z. Dalton, Zachary C. Payne, Sebastien Perrier, Matthieu Riva, Jonathan D. Raff, Christian George
更新时间: 2020-11-26
摘要: Nitrate anion (NO3–) is ubiquitous in the environment, and its photochemistry produces nitrous acid (HONO), a major source of tropospheric hydroxyl radical (OH). Enhanced HONO(g) emissions have been observed from NO3–(aq) photolysis in field studies, although the underlying reasons for this enhancement are debated. Here, we show that the enhancement is in part caused by changes in secondary nitrate anion photochemistry due to dissolved aliphatic organic matter (DAOM). Increased yields of superoxide radical (O2–) and HONO were observed when NO3– solutions (pH 6) were photolyzed in the presence of DAOM surrogates of varying solubility. In an additional experiment, nitrate titrated with additional DAOM showed a further simultaneous increase in the levels of O2–(aq) and HONO(g) with decreased yields of gaseous nitric oxide (NO) and nitrogen dioxide (NO2). To the best of our knowledge, this is the first time that superoxide was directly observed as an intermediate in nitrate photolysis experiments, produced through DOAM oxidation by OH(aq). Herein, we suggest that enhanced HONO(g) emissions from NO3–(aq) photolysis result from the reaction of O2–(aq) with NO2(aq) and NO(aq) to form peroxynitrate (OONO2–) and peroxynitrite (OONO–), respectively, which are precursors to nitrite (NO2–). Overall, this points to an important role of O2–(aq) in aqueous aerosol chemistry, which is currently underappreciated.

18. 题目: Mechanistic insights into organic carbon-driven water blackening and odorization of urban rivers
文章编号: N20112601
期刊: Journal of Hazardous Materials
作者: Zhiwei Liang, Wenwen Fang, Yukui Luo, Qihong Lu, Philippe Juneau, Zhili He, Shanquan Wang
更新时间: 2020-11-26
摘要: With rapid global urbanization, massive anthropogenic inputs of organic matter and inorganic nutrients are resulting in severe pollution of urban rivers and consequently altering the structure and function of their aquatic microbial communities. In contrast to nutrient-induced eutrophication of freshwaters, water blackening and odorization of urban rivers, as well as their microbial communities, are poorly understood at a mechanistic level. Here, in a one-year field study on the taxonomic composition, predicted function and spatiotemporal dynamics of water and sediment microbial communities in seven black-odorous urban rivers in a megacity in southern China, combined with laboratory water-sediment column experiments, we pinpointed organic carbon as a key parameter driving the overgrowth of aquatic heterogeneous microorganisms. These microorganisms are major constituents of suspended black flocs that mediate methanogenic digestion of organic carbon and consequent water blackening and odorization. Source tracking analysis revealed a strikingly high contribution of sewage communities to black-odorous water microbial communities, in which emerging pathogens are enriched. Our results provide mechanistic insight into organic carbon-driven water blackening and odorization of urban rivers, which brings up current remediation strategies in questioning and sheds light on the future sustainable management of urban aquatic ecosystems.

19. 题目: Reconstructing past variations in environmental conditions and paleoproductivity over the last ∼ 8000 years off north-central Chile (30° S)
文章编号: N20112516
期刊: Biogeosciences
作者: Práxedes Muñoz, Lorena Rebolledo, Laurent Dezileau, Antonio Maldonado, Christoph Mayr, Paola Cárdenas, Carina B. Lange, Katherine Lalangui, Gloria Sanchez, Marco Salamanca, Karen Araya, Ignacio Jara, Gabriel Easton, Marcel Ramos
更新时间: 2020-11-25
摘要: 6600 cal BP, (2) 4500–1800 cal BP and (3) 140 cal BP to the present (2015 CE). The first period was characterized by a remarkably higher productivity (higher diatom abundances and opal) in which large fluxes of organic compounds were also inferred from the accumulation of elements, such as Ba, Ca, Ni, Cd and P, in the sediments. Meanwhile, significantly reduced conditions at the bottom of the bays were suggested based on the large accumulation of Mo, Re and U, showing a peak at 6600 cal BP, when sulfidic conditions could have been present. According to the pollen moisture index (PMI), this was also identified as the driest interval. These conditions should be associated with an intensification of the Southern Pacific Subtropical Anticyclone (SPSA) and stronger southerly western winds, emulating La Niña-like conditions, as has been described for the SE Pacific during the early Holocene and part of the mid-Holocene. During most of the second period, lower productivity was observed; however, a small increase was identified between 3400 and 4000 cal BP, although lower amounts of diatom (valves g−1) and nutrient-type metal accumulations were evident. Anoxic conditions at the bottom of the bays changed to an almost stable suboxic condition during this time interval. The third period was marked by intense oxygenation after 1800 cal BP, as observed by a drastic change in the accumulation of U, Mo and Re. This was followed by a return to more reduced conditions over the past 2 centuries, characterized by a small productivity rise after ∼140 cal BP, as suggested by the opal accumulations. Overall, lower primary productivity, lower reduced conditions at the bottom and higher-humidity conditions were established after 6600 cal BP to the present. We suggest that the oxygenation might be associated with a weak effect from the oxygen minimum zone over the shelf and intensified El Niño activity, introducing oxygenated waters to the coastal zones through the propagation of equatorial waves and establishment of conditions that reduced the primary productivity from the mid-Holocene toward the beginning of the modern era.]]>

20. 题目: Effect of protists on rhizobacterial community composition and rice plant growth in a biochar amended soil
文章编号: N20112515
期刊: Biology and Fertility of Soils
作者: Rasit Asiloglu, Bahar Sevilir, Solomon Oloruntoba Samuel, Murat Aycan, Muhittin Onur Akca, Kazuki Suzuki, Jun Murase, Oguz Can Turgay, Naoki Harada
更新时间: 2020-11-25
摘要: The effects of protists on an indigenous soil bacterial community, putative bacterial genes involved in N-cycling, and the rice plant growth were studied in poultry litter biochar (PL) and rice husk biochar (RH) amended (with two application doses: 2% and 4% w/w) paddy field soil. The bacterial community composition, which was evaluated using 16S rRNA gene amplicon sequencing, was significantly and differentially affected by the protists, the PL and the RH. The effects of protists on the bacterial community composition were decreased by the RH and the PL treatments. The number of protist-affected bioindicator bacterial taxa was decreased from 90 to 46, 29, 43, and 21 in the 2% RH-, 4% RH-, 2% PL-, and 4% PL-treated soils, respectively. The presence of the protist significantly increased the abundance of the putative bacterial genes involved in mineralisation, dissimilatory nitrate reduction to ammonium (DNRA), and NO3- assimilation, and the same occurred with PL treatments. The rice plant growth and N uptake were always higher in the presence of protists and PL amendments. Overall our results suggest a new insight into the effects of biochar on the bacterial community via altering the trophic interactions.