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24621. 题目: As(III) and As(V) Removal Mechanisms by Fe-modified Biochar Characterized Using Synchrotron-based X-ray Absorption Spectroscopy and Confocal Micro-X-ray Fluorescence Imaging
文章编号: N20021409
期刊: Bioresource Technology
作者: Yong Xu, Xianjun Xie, Yu Feng, Muhammad Aqeel Ashraf, YingYing Liu, Chunli Su, Kun Qian, Peng Liu
更新时间: 2020-02-14
摘要: Batch experiments followed by solid-phase analyses were conducted to explore As(III) and As(V) removal mechanisms by Fe-modified biochars (FeBC) pyrolyzed at different temperatures (300, 600, and 900 °C). Arsenic removal by FeBC, best described by pseudo-second order kinetic and Langmuir isotherm models, increased from 73.8 to 99.9% for As(III) and 86.8 to 99.9% for As(V) as the pyrolysis temperature increased. The addition of calcite enhanced the removal efficiency (all >99%). Confocal micro-X-ray fluorescence imaging (CMXRFI) analyses indicated As co-located with Fe and diffused deeper into the particles as the pyrolysis temperature increased. For As(III)-spiked systems, X-ray absorption near-edge structure (XANES) data indicated 20.2 to 81.5% of As(III) was oxidized to As(V) as the pyrolysis temperature increased; an increase of oxidation efficiency was observed after adding calcite. For As(V)-spiked systems, no As(V) reduction was observed. Overall, As(III/V) removal using FeBC was affected by the spatial distribution and species of As.
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24622. 题目: Effects of high concentrations of sulfate on dissolved organic matter in paddy soils revealed by excitation-emission matrix analyzing
文章编号: N20021408
期刊: Chemosphere
作者: Qin Chen, Rong Jia, Lina Li, Dong Qu
更新时间: 2020-02-14
摘要: The problem of sulfate pollution is becoming increasingly serious in freshwater and wetlands. Since paddy fields are the largest constructed wetland in Earth’s surface, the increased sulfate input may have great effect on dissolved organic matter (DOM) in paddy soils. To understand these effects, a 24-day anaerobic incubation experiment was conducted with four Chinese paddy soils amended with high concentrations (0, 10, 25, 50, and 100 mmol·L⁻¹) of Na₂SO₄. Dissolved organic carbon (DOC) and chlorophyll a (Chl a) concentrations were determined after incubation. Parallel factor analysis (PARAFAC) of the excitation–emission matrix (EEM) spectra was used to analyze the DOM composition. In all four soils, DOC concentrations generally increased with increasing sulfate concentration, while the Chl a concentrations decreased. The EEM spectra of DOM were resolved into four components by PARAFAC. With increasing sulfate concentration, the proportion of the ultraviolet C humic acid-like compound decreased and the tyrosine-like compound increased in two algae-rich soils (Sichuan and Tianjin). No obvious variation was observed in the humification index (HIX) or the ratio of peak β to peak α (β:α) in any soils with added sulfate. Specific ultra-violet absorbance at 254 nm (SUVA₂₅₄) decreased with increasing sulfate concentration in Jilin, Tianjin, and Ningxia soils, and the fluorescence index (FI) decreased in two algae-rich soils. In conclusion, although sulfate addition increased the DOC concentration, the DOM composition depended more strongly on soil type and physicochemical properties than sulfate. Sulfate addition only affected soil DOM origin and composition by inhibiting algal growth in algae-rich paddy soils.

24623. 题目: Assessing the sensitivity and repeatability of permanganate oxidizable carbon as a soil health metric: An interlab comparison across soils
文章编号: N20021407
期刊: Geoderma
作者: Jordon Wade, Gabriel Maltais-Landry, Dawn E. Lucas, Giulia Bongiorno, Timothy M. Bowles, Francisco J. Calderón, Steve W. Culman, Rachel Daughtridge, Jessica G. Ernakovich, Steven J. Fonte, Dinh Giang, Bethany L. Herman, Lindsey Guan, Julie D. Jastrow, Bryan H.H. Loh, Courtland Kelly, Meredith E. Mann, Roser Matamala, Elizabeth A. Miernicki, Brandon Peterson
更新时间: 2020-02-14
摘要: Soil organic matter is central to the soil health framework. Therefore, reliable indicators of changes in soil organic matter are essential to inform land management decisions. Permanganate oxidizable carbon (POXC), an emerging soil health indicator, has shown promise for being sensitive to soil management. However, strict standardization is required for widespread implementation in research and commercial contexts. Here, we used 36 soils—three from each of the 12 USDA soil orders—to determine the effects of sieve size and soil mass of analysis on POXC results. Using replicated measurements across 12 labs in the US and the EU (n = 7951 samples), we quantified the relative importance of 1) variation between labs, 2) variation within labs, 3) effect soil mass, and 4) effect of soil sieve size on the repeatability of POXC. We found a wide range of overall variability in POXC values across labs (0.03 to 171.8%; mean = 13.4%), and much of this variability was attributable to within-lab variation (median = 6.5%) independently of soil mass or sieve size. Greater soil mass (2.5 g) decreased absolute POXC values by a mean of 177 mg kg⁻¹ soil and decreased analytical variability by 6.5%. For soils with organic carbon (SOC) >10%, greater soil mass (2.5 g) resulted in more frequent POXC values above the limit of detection whereas the lower soil mass (0.75 g) resulted in POXC values below the limit of detection for SOC contents <5%. A finer sieve size increased absolute values of POXC by 124 mg kg⁻¹ while decreasing the analytical variability by 1.8%. In general, soils with greater SOC contents had lower analytical variability. These results point to potential standardizations of the POXC protocol that can decrease the variability of the metric. We recommend that the POXC protocol be standardized to use 2.5 g for soils <10% SOC. Sieve size was a relatively small contributor to analytical variability and therefore we recommend that this decision be tailored to the study purpose. Tradeoffs associated with these standardizations can be mitigated, ultimately providing guidance on how to standardize POXC for routine analysis.

24624. 题目: Preparation of montmorillonite modified biochar with various temperatures and their mechanism for Zn ion removal
文章编号: N20021406
期刊: Journal of Hazardous Materials
作者: Jingpeng Song, Shuaishuai Zhang, Guixiang Li, Qing Du, Fan Yang
更新时间: 2020-02-14
摘要: Because of its layered structure, excellent adsorption, catalytic and ion exchange properties, strong passivation, and superior adsorption capacity for heavy metals, montmorillonite as biochar modifier was introduced. Montmorillonite modified biochar composites (BC-MNT) were successfully prepared by one-step hydrothermal progress and subsequent pyrolysis for the application of Zn (II) removal from aqueous solution. Herein, our research mainly explored the effect of different hydrothermal method/pyrolysis temperatures on the adsorption properties of montmorillonite-biochar composites, since that temperature can greatly change the surface functional groups and chemical composition and structure of biochar. Primarily, adopting VK analysis method analyzed raw biochar and montmorillonite modified biochar at different temperature condition. For further research, adsorption mechanism was realized by means of SEM-EDS, XRD, FTIR, and XPS, as concluded that electrostatic interaction between the negative charge of the interlayers and Zn (II) and surface complexation took up a dominant role. The kinetic and isothermal adsorption mathematical model fitting were also performed, which was more suitable for pseudo-second order and Freundlich model, suggesting that the limited speed stage was dominated by chemical forces. The optimal preparation temperature (350 °C) and maximum adsorption amount (8.163 mg·g⁻¹) were determined by the adsorption experiment model.
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24625. 题目: Paleo-environmental variation and its control on organic matter enrichment of black shales from shallow shelf to slope regions on the Upper Yangtze Platform during Cambrian Stage 3
文章编号: N20021405
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Yaowen Wu, Hui Tian, Dajian Gong, Tengfei Li, Qin Zhou
更新时间: 2020-02-14
摘要: To understand the evolution of oceanic redox conditions and organic matter (OM) accumulation in the shelf and slope regions of the Upper Yangtze Platform during Cambrian Stage 3, high-resolution geochemical data were obtained from two wells respectively representing shelf and slope environments. Based on redox proxies, widespread anoxic/euxinic waters with intermittent sulfidic water columns were formed from shallow shelf to deep water slope and basinal regions during Stage 2 and early Stage 3; then, widespread anoxic waters were reduced and oxic waters expanded during the middle Stage 3, after which fluctuating suboxic and oxic (occasionally anoxic) environments became predominant during late Stage 3. The presence of hyalophane and positive Eu anomalies suggest strong Ba-rich hydrothermal activities in the shelf and deep basin regions during early and middle Stage 3. The Ba-rich hydrothermal fluids and upwelling events enhanced the primary productivity in surface waters and subsequently promoted organic matter enrichment. During Stage 2 and early Stage 3, the high primary productivity driven by coastal upwelling and hydrothermal activity were the main factors controlling OM enrichment; during middle Stage 3, the local anoxic water condition became responsible for OM enrichment when oxic waters began to gradually expand; during late Stage 3, both primary productivity and redox conditions became the main control factors for OM enrichment. According to the analysis of primary productivity, redox conditions, hydrothermal activity and upwelling events, an evolution model is proposed to account for the paleo-environmental variation and the OM enrichment from shallow shelf to slope regions during Cambrian Stage 3.

24626. 题目: Goethite-modified biochar ameliorates the growth of rice (Oryza sativa L.) plants by suppressing Cd and As-induced oxidative stress in Cd and As co-contaminated paddy soil
文章编号: N20021404
期刊: Science of The Total Environment
作者: Muhammad Kashif Irshad, Ali Noman, Haifa A.S. Alhaithloul, Muhammad Adeel, Yukui Rui, Tufail Shah, Sihang Zhu, Jianying Shang
更新时间: 2020-02-14
摘要: Co-contamination of soils with cadmium (Cd) and arsenic (As) in rice growing areas is a serious threat to environment and human health. Increase in soil Cd and As levels curtail the growth and development of rice plants by causing oxidative stress and reduction in photosynthetic activity. Therefore, it is necessary to formulate and evaluate different strategies for minimizing the Cd and As uptake in rice plant. We modified biochar (BC) with goethite and assessed the effects of goethite-modified biochar (GB) application on mitigating Cd and As stress in rice plant. Although BC supply to rice plants enhanced their performance in contaminated soil but application of different GB levels i.e.1.5% GB to the soil resulted in prominent improvements in physiological and biochemical attributes of rice plants grown in Cd and As co-contaminated paddy soil. It was observed that soil amendment with GB increased the plant growth, biomass, photosynthetic pigments, gas exchange attribute of rice plant and suppressed the oxidative stress in rice leaves and roots by increased antioxidant enzymes activities. Supplementing the soil with 1.5% GB incremented the iron plaque (Fe-plaque) formation and enhanced the Cd and As sequestration by Fe-plaque. Application of GB (1.5%) significantly improved the Fe content of Fe-plaque by 68.7%. Maximum Cd (1.57 mg kg⁻¹) and As (0.85 mg kg⁻¹) sequestration by Fe-plaque was observed with 1.5% GB treatment. Compared to the control, 1.5% GB treatment application prominently reduced the Cd content in the rice roots and shoots by 42.9%, and 56.7%, respectively and As content in the rice roots and shoots declined by 32.2%, 46.6%, respectively, compared to the control. These findings demonstrate that amending the soil with 1.5% GB can be a potential remediation strategy for checking Cd and As accumulation, reducing oxidative stress and increasing the growth of rice plant.
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24627. 题目: Effects of biochar on soil microbial community and functional genes of a landfill cover three years after ecological restoration
文章编号: N20021403
期刊: Science of The Total Environment
作者: Hang Lu, Mengxue Yan, Ming Hung Wong, Wing Yin Mo, Yinghui Wang, Xun Wen Chen, Jun-Jian Wang
更新时间: 2020-02-14
摘要: Landfills, as the most common approach to disposing of municipal solid waste worldwide, disturb native ecosystems and create a need for ecological restoration. The restoration of landfill cover with biochar has shown immediate potential to improve soil microbial functions within one year. However, such characteristics could change after a longer period of time. Here, soil properties, microbial communities, and microbial functional genes related to nutrient cycling were investigated three years after the biochar amendment of the topsoil of a subtropical landfill cover. The results showed that the levels of soil organic matter, water content, total carbon (C), total nitrogen (N) and total phosphorus (P) of biochar-amended soils were higher than those of control soil. Different soil microbial community structures were observed in the biochar-amended and control soils. Nine phyla, including Proteobacteria and Acidobacteria, but not Actinobacteria or Chloroflexi, were enriched in the biochar-amended soil. Although the impact of biochar on shaping microbial communities increased after a longer period of restoration, no differences were observed in soils that were amended using different biochar:soil ratios. The abundances of functional genes related to C and N cycling decreased, whereas those of genes related to P cycling were higher in soils that received biochar amendment. This finding suggests that compared with the control soil, biochar-amended soils were less active in processes involved in C and N cycling but enhanced in processes related to P cycling. This study can serve as a reference for future ecological restoration of degraded lands using biochar.
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24628. 题目: Application of organic carbon affects mineral nitrogen uptake by winter wheat and leaching in subsoil: Proximal sensing as a tool for agronomic practice
文章编号: N20021402
期刊: Science of The Total Environment
作者: Petr Holub, Karel Klem, Ivan Tůma, Jana Vavříková, Kateřina Surá, Barbora Veselá, Otmar Urban, Jaroslav Záhora
更新时间: 2020-02-14
摘要: We tested the hypothesis that application of stable forms of organic carbon (C) into the soil reduces leaching of nitrogen (N). We also examined the potential to estimate N leaching employing N-sensitive spectral reflectance indices. During three growing seasons 2013–2015, field experiment at two experimental sites combining application of distinct N doses (0 (N₀), 35 (N₃₅), 70 (N₇₀), and 140 (N₁₄₀) kg N ha⁻¹) and two stable forms of organic C (lignohumate and compost) was established to measure N uptake by winter wheat and its leaching to subsoil layers. The spectral reflectance at canopy level was measured simultaneously with N content in leaf dry matter at the beginning of the grain filling phase. At full maturity, the above-ground biomass, grain yield, and grain protein content were evaluated. That data was used to calculate N uptake in grain. The N₁₄₀ dose led to increased N uptake by grain of 64% and 73% in the wetter years 2013 and 2014, respectively, and even by 118% in the drier year 2015 in comparison with the N₀ treatment. N leaching to subsoil increased substantially with higher N dose, but only in wetter years 2013 (by 74%) and 2014 (by 87%). By contrast, no effect of N dose on leached N was found in the dry year 2015. The application of organic C along with the N₁₄₀ dose substantially reduced N leaching by 26% and 29% in 2014 and 2015, respectively. Moreover, we demonstrated that normalized red-edge spectral reflectance index (NRERI) is able to predict N uptake by wheat and it can serve as an indicator of N leaching in heavy-rainfall years. Our results thus point towards possible agronomic practices and use of remote-sensing techniques to reduce groundwater contamination by N-based fertilizers.
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24629. 题目: In situ nitrogen functionalization of biochar via one-pot synthesis for catalytic peroxymonosulfate activation: Characteristics and performance studies
文章编号: N20021401
期刊: Separation and Purification Technology
作者: Zaeni Julia Raudlatul Jannah, Jun-Wei Lim, Zhaohui Wang, Dahu Ding, Yong-Shen Chua, Si-Ling Ng, Wen-Da Oh
更新时间: 2020-02-14
摘要: A facile and scalable one-pot synthesis method was designed to fabricate N-doped biochar from wood residue for peroxymonosulfate (PMS) activation. The urea:wood residue w/w ratio was varied from 0:1 to 100:1, and the intrinsic (surface chemistry) and extrinsic (morphology, specific surface area, etc.) properties of the N-doped biochar were systematically investigated. Notably, the urea:wood residue w/w ratio played a significant role in tuning the N species composition in the N-doped biochar. A higher urea:wood residue w/w ratio resulted in greater at.% of graphitic N and higher specific surface area. The results show that the catalyst prepared with urea:wood residue w/w ratio of 100:1 (NC800-20) manifested the greatest catalytic activity as PMS activator for organics removal due to its highly favorable combination of intrinsic (highest at.% graphitic N) and extrinsic (excellent specific surface area) properties. The catalyst loading, PMS dosage and pH were found to be operationally crucial for PMS activation. Under the best condition, the NC800-20 can be used to degrade various organic pollutants. The recyclability of NC800-20 was studied and while the catalytic activity gradually deteriorated over successive cycles, it can be completely restored by simple calcination at 500°C. The used catalyst was extensively characterized, revealing insights into the mechanism of PMS activation. The prevailing mechanism for PMS activation was the nonradical pathway. Overall, this research provides insights into preparing N-doped biochar with favorable extrinsic and intrinsic properties from biowaste for sustainable pollutant removal via PMS activation.
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24630. 题目: Impact of Natural Organic Matter on Plutonium Vadose Zone Migration from an NH 4 Pu(V)O 2 CO 3 (s) Source
文章编号: N20021306
期刊: Environmental Science & Technology
作者: Melody Maloubier, Hilary Emerson, Kathryn Peruski, Annie B. Kersting, Mavrik Zavarin, Philip M. Almond, Daniel I Kaplan, Brian A. Powell
更新时间: 2020-02-13
摘要: We investigated the influence of natural organic matter (NOM) on the behavior of Pu(V) in the vadose zone through a combination of the field lysimeter and laboratory studies. Well-defined solid sources of NH4Pu(V)O2CO3(s) were placed in two 5-L lysimeters containing NOM-amended soil collected from the Savannah River Site (SRS) or unamended vadose zone soil and exposed to 3 years of natural South Carolina, USA, meteorological conditions. Lysimeter soil cores were removed from the field, used in desorption experiments, and characterized using wet chemistry methods and X-ray absorption spectroscopy. For both lysimeters, Pu migrated slowly with the majority (>95%) remaining within 2 cm of the source. However, without the NOM amendment, Pu was transported significantly farther than in the presence of NOM. Downward Pu migration appears to be influenced by the initial source oxidation state and composition. These Pu(V) sources exhibited significantly greater migration than previous studies using Pu(IV) or Pu(III) sources. However, batch laboratory experiments demonstrated that Pu(V) is reduced by the lysimeter soil in the order of hours, indicating that downward migration of Pu may be due to cycling between Pu(V) and Pu(IV). Under the conditions of these experiments, NOM appeared to both enhance reduction of the Pu(V) source as well as Pu sorption to soils. This indicates that NOM will tend to have a stabilizing effect on Pu migration under SRS vadose zone field conditions.

24631. 题目: The role of soil organic matters and minerals on hydrogen peroxide decomposition in the soil
文章编号: N20021305
期刊: Chemosphere
作者: Hamed Vafaei Molamahmood, Jiaolong Qin, Yitong Zhu, Menglin Deng, Mingce Long
更新时间: 2020-02-13
摘要: Application of H₂O₂ in in-situ chemical oxidation (ISCO) for soil remediation has been limited by its rapid decomposition. However, effect of main factors involving in this phenomenon are not well understood. In this contribution, H₂O₂ decomposition in the six types of natural soils was investigated by kinetic analyses and soil characterizations. The grassland soil (GS) and red soil (RS) have the highest H₂O₂ decomposition rates (respective 0.048 and 0.069 min⁻¹), while the paddy soil (PS) shows the lowest one (0.004 min⁻¹). The decomposition mainly takes place on the surface adsorption sites of soil particles. PS has the highest content of SOM, which can block the active adsorption sites for H₂O₂ decomposition. The effects of dissolved organic matter (DOM) and biological debris in the soil are minor. Iron and manganese containing minerals are significantly influential on H₂O₂ decomposition, and the soil with a higher content of clay can induce faster H₂O₂ decomposition. The immobilized goethite (GM) and birnessite (BM) on montmorillonite were synthesized to simulate soil minerals. Results show H₂O₂ decomposition rates in BM is even faster than GM when the former dosage is two orders of magnitude lower than that of the latter. This indicates the crucial role of manganese minerals although their contents are generally much lower than that of iron in the soils. This study advanced the understanding of H₂O₂ decomposition in the soil and bring insights for H₂O₂ based ISCO technology in soil remediation.

24632. 题目: Behaviors and fate of adsorbed Cr(VI) during Fe(II)-induced transformation of ferrihydrite-humic acid co-precipitates
文章编号: N20021304
期刊: Journal of Hazardous Materials
作者: Guangda Yu, Fenglian Fu, Chujia Ye, Bing Tang
更新时间: 2020-02-13
摘要: The mobility of Cr(VI) in the environment is affected by the transformation of ferrihydrite (Fh) and ferrihydrite-humic acid co-precipitates (Fh-HA). However, the impacts of Fe(II)-induced transformation of Fh and Fh-HA on the mobility, speciation and partitioning of associated Cr(VI) remain unclear. In this study, the behaviors of adsorbed Cr(VI) during Fh and Fh-HA aging at 70 °C for 9 days (pH₀ = 3.0 and 7.0) in the absence and presence of Fe(II) were studied. Results revealed that the main speciation of Cr(VI) after transformation was non-desorbable Cr and its formation involved the following pathways. Firstly, Fe(II) (0.2 and 2.0 mM) induced the transformation of Fh-HA to hematite and goethite, promoting the structural incorporation of adsorbed Cr into hematite and goethite via complexation. Secondly, under neutral condition (pH₀ = 7.0), the low concentration of Fe(II) (0.2 mM) could not reduce completely Cr(VI) to Cr(III) and thus residual Cr(VI) was incorporated into the Cr(III)-Fe(III) co-precipitates. Thirdly, coprecipitated humic acid not only reduced Cr(VI) to Cr(III) via polysaccharide, but also formed complexes with incorporated Cr through carboxylic groups to sequester Cr. Our results demonstrate that Fe(II)-induced transformation of Fh-HA exerts major influences on associated Cr(VI) speciation and partitioning.
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24633. 题目: Optical properties of aerosol brown carbon (BrC) in the eastern Indo-Gangetic Plain
文章编号: N20021303
期刊: Science of The Total Environment
作者: Archita Rana, Supriya Dey, Prashant Rawat, Arya Mukherjee, Jingying Mao, Shiguo Jia, Pandit S. Khillare, Amit Kumar Yadav, Sayantan Sarkar
更新时间: 2020-02-13
摘要: We report here measurements of aerosol black carbon (BC) and aqueous and methanol-extractable brown carbon (BrC_aq and BrC_me) from a receptor location in the eastern Indo-Gangetic Plain (IGP) under two aerosol regimes: the photochemistry-dominated summer and biomass burning (BB) dominated post-monsoon. We couple time-resolved measurements of BC and aerosol light absorption coefficients (b_abs) with time-integrated analysis of BrC UV–Vis and fluorescence characteristics, along with measurements of total and water-soluble organic carbon (OC and WSOC), and ionic species (NH₄⁺, K⁺, NO₃⁻). In the BB regime, BC and its BB-derived fraction (BC_BB) increased by factors of 3–4 over summertime values. In comparison, b_{abs_365_aq} and b_{abs_365_me} (absorption coefficients of BrC_aq and BrC_me at 365 nm) increased by a factor of 5 (9.7 ± 7.8 vs 2.1 ± 1.4 Mm⁻¹) and 2.5 (17.2 ± 9.0 vs 6.9 ± 2.9 Mm⁻¹), respectively, in the BB period over summer, and were highly correlated (r = 0.82–0.87; p < 0.01) with the BB-tracer nssK⁺. The wavelength dependence of b_{abs_BrC} (Ångstrom exponent: 5.9–6.2) and the presence of characteristic fluorescence peaks at 420–430 nm suggested presence of humic-like substances (HULIS) in the aged BB aerosol, while significant association between BrC_aq and NO₃⁻ (r = 0.73; p < 0.01) possibly indicated formation of water-soluble nitroaromatic compounds. BrC_aq contributed 55% to total BrC absorption at 300–400 nm while that for the water-insoluble component (WI-BrC) increased from 41% at 340 nm to ~60% at 550 nm, suggesting formation of water-insoluble polycyclic aromatic hydrocarbons (PAHs) and/or N-PAHs. Mass absorption efficiencies at 365 nm (MAE₃₆₅) of BrC_aq and BrC_me in the BB regime (0.95 ± 0.45 and 1.17 ± 0.78 m² g⁻¹, respectively) were in line with values expected from photobleaching of BB source emissions after transport to the eastern IGP. Overall, BrC_aq and BrC_me were significant components of light absorbing aerosol in the BB regime, with contributions of 9 ± 5% and 16 ± 7%, respectively, to radiative forcing vis-à-vis BC in the 300–400 nm range.
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24634. 题目: Soil organic carbon pool and chemical composition under different types of land use in wetland: Implication for carbon sequestration in wetlands
文章编号: N20021302
期刊: Science of The Total Environment
作者: Huai Ji, Jiangang Han, Jianming Xue, Jeff A. Hatten, Minhuang Wang, Yanhui Guo, Pingping Li
更新时间: 2020-02-13
摘要: This study was conducted to understand how different wetland vegetation-land use types influenced the storage and stability of soil organic carbon (SOC) in surface soils. We determined the concentration and chemical composition of SOC in both density (including light fraction organic carbon (LFOC) and heavy fraction organic carbon (HFOC)) and particle size fractions (including <2 μm, 2–63 μm, 63–200 μm and 200–2000 μm) in four wetland land use types covered with different vegetation: lake-sedge, reed, willow and poplar wetlands. Results showed that the concentrations and stock of SOC and LFOC in willow and poplar wetlands were significantly higher than those in lake-sedge and reed. However, a higher proportion of alkyl-C and a lower proportion of O-alkyl-C were observed in lake-sedge and reed wetlands than in willow and poplar, suggesting that accumulated C in willow and poplar wetlands was less stable than that in lake-sedge and reed. For all particle-size fractions except the silt (2–63 μm), the SOC concentrations were highest in willow and lowest in reed wetland surface soils, while their alkyl-C/O-alkyl-C (A/O-A) and hydrophobic-C/hydrophilic-C ratios progressively decreased from lake-sedge and reed wetland surface soils to poplar and willow surface soils. Moreover, the ratios of A/O-A and hydrophobic-C/hydrophilic-C in surface soils generally decreased with increasing concentrations of SOC in particle-size fractions, with these stability indexes being lowest in the largest particle-size fraction. These results indicate that the wetland vegetation-land use types that could incorporate more C into finer particle-size fractions had a greater potential for sequestering more stable C in such wetland ecosystems. Different wetland vegetation-land use types resulted in significant changes in the concentration and chemical structure of SOC, which could affect soil C sequestration and dynamics, C cycling in wetland ecosystems. Although both willow and poplar forests could increase SOC stock, the stability of SOC in willow wetland was higher. Therefore, on balance (stock and stability) the land use of wetland for willow forest could be a more promising way for enhancing soil C sequestration in wetlands.
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24635. 题目: Modeling the formation of microorganism-derived dissolved organic nitrogen (mDON) in the activated sludge system
文章编号: N20021301
期刊: Water Research
作者: Haidong Hu, Kewei Liao, Wenming Xie, Jinfeng Wang, Bing Wu, Hongqiang Ren
更新时间: 2020-02-13
摘要: Microorganism-derived dissolved organic nitrogen (mDON) represents a significant and inevitable portion of dissolved organic nitrogen (DON) in the wastewater biotreatment processes. In the existing method, mDON concentrations are indirectly measured by the values of DON concentrations from the reactors with DON-free influent. However, this becomes problematic when influent contains DON. Especially when the real wastewater is involved, the paucity of the direct methods to quantitatively measure mDON is a major barrier to further research. This limitation is due to the difficulty of segregating mDON from the other nitrogenous organics, e.g., influent DON. In this study, we propose the ASM-mDON model based on ASM #1, which incorporates the production and consumption of mDON in the activated sludge processes to predict the mDON concentrations. In four independent lab-scale tests, our model was established and calibrated to obtain the accurate values of mDON (R² = 0.929, p < 0.05), and the validity and applicability of the model were successfully examined by comparing the simulated and measured data. Moreover, the universality of the ASM-mDON model was further confirmed by simulating mDON production in a full-scale wastewater treatment plant. A reasonable prediction of mDON formation was shown in a full-scale test (1.98 ± 0.71 mg/L in June and 1.51 ± 0.54 mg/L in July) and is indirectly supported by an algal bioassay (p < 0.05, t-test). This study provides a useful approach to the efficient and accurate evaluation of mDON formation, which will improve current strategies designed to minimize the effluent mDON in wastewater bioprocesses.
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24636. 题目: Element composition of soils to assess the success of wetland restoration
文章编号: N20021208
期刊: Land Degradation & Development
作者: Guodong Wang, Ming Jiang, Ming Wang, Zhenshan Xue
更新时间: 2020-02-12
摘要: The main purpose of this study is to assess if wetland restoration is associated with a directional shift in soil element concentration toward their original pre‐farming status in the peatlands of northeastern China. The concentrations of 55 soil elements and related environmental factors including organic matter content, electrical conductivity and pH were investigated in natural, restored and farmed wetlands in the Xingkai Lake Watershed of northeastern China. All but four of the soil element concentrations varied by wetland type (natural, restored, and farmed wetlands), and the soil concentrations of 41 elements increased from natural to restored to farmed wetlands. Soil organic matter and electrical conductivity explained 87.8% and 3.3% of the variation in element concentration based on ordination analysis using RDA. Both non‐metric multidimensional scaling analysis (NMDS) and cluster analysis indicated that the restored wetlands had a higher similarity with the farmed wetlands than the natural wetlands. Our findings suggest that restoration led to an increase in soil organic matter content and shifts in level of element concentration that was more similar to natural wetlands. However, differences remained so that the biogeochemistry of restored wetlands was not the same as the original pre‐farming level. This information is very important for wetland restoration, because to be successful, not only biodiversity and hydrology, but also the soil element composition and biogeochemistry need to be restored. Our approach can be used to assess the success of wetland restoration.

24637. 题目: Determinants of Soil Organic Carbon Sequestration and Its Contribution to Ecosystem Carbon Sinks of Planted Forests
文章编号: N20021207
期刊: Global Change Biology
作者: Shiqiang Wang, Yao Huang
更新时间: 2020-02-12
摘要: The area of forest established through afforestation/reforestation has been increasing on a global scale, which is particularly important as these planted forests attenuate climate change by sequestering carbon. However, the determinants of soil organic carbon sequestration and their contribution to the ecosystem carbon sink of planted forests remains uncertain. By using globally distributed data extracted from 154 peer‐reviewed publications and a total of 355 sampling points, we investigated above‐ground biomass carbon (ABC) sequestration and soil organic carbon (SOC) sequestration across three different climatic zones (tropical, warm temperate, and cold temperate) through correlation analysis, regression models, and structural equation modeling (SEM). We found that the proportion of SOC sequestration in the ecosystem C sequestration averaged 14.1% globally, being the highest (27.0%) in the warm temperate and the lowest (10.7%) in the tropical climatic zones. The proportion was mainly affected by latitude. The sink rate of ABC (RABC) in tropical climates (2.48 Mg C ha−1 yr−1) and the sink rate of SOC (RSOC) in warm temperate climates (0.96 Mg C ha−1 yr−1) were higher than other climatic zones. The main determinants of RSOC were the number of frost‐free days, latitude, mean annual precipitation (MAP), and soil organic carbon density (SOCD) at the initial observation; however, these variables depended on the climatic zone. According to the SEM, frost‐free period MAT, and MAP are the dominant driving factors affecting RSOC in Chinese plantations. MAT has an positive effect on RSOC, and global warming may increase RSOC of temperate plantations in China. Our findings highlight the determinants of SOC sequestration and quantitatively reveal the substantial global contribution of SOC sequestration to ecosystem carbon sink provided by planted forests. Our results help managers identify and control key factors to increase carbon sequestration in forest ecosystems.

24638. 题目: Comparative study on Pb²⁺ removal from aqueous solutions using biochars derived from cow manure and its vermicompost
文章编号: N20021206
期刊: Science of The Total Environment
作者: Weiwen Zhang, Wenhui Du, Feng Wang, Huiting Xu, Tonghe Zhao, Hangjun Zhang, Ying Ding, Weiqin Zhu
更新时间: 2020-02-12
摘要: Waste emissions have increased the amount of water and soil contaminated with heavy metals such as Pb. To broaden the methods for the recycling and environmental usage of cow manure (CM) and its vermicompost (CV), CM, CV, and their derived biochars produced by the pyrolysis of CM or CV at 350 and 700 °C were used as adsorbents for Pb²⁺ removal in this batch adsorption experiment to reveal their different Pb²⁺ removal efficiencies and the underlying mechanisms. The batch experiment results revealed that all adsorbents rapidly removed Pb²⁺ within 30 min. A pH between 2.0 and 6.0 positively affected Pb²⁺ removal by CM and its biochar, whereas that by CV and its biochar was only positively affected by pH between 2.0 and 3.0. CV-derived biochar was more effective in the removal of Pb²⁺ than the other absorbents, with the maximum adsorption capacities (Qm) fitted from the Langmuir model reaching approximately 230.0 mg·g⁻¹ and the desorption rate (DR) being approximately 0.00–0.02%. Material physiochemical characterization, including X-ray diffraction analysis, showed that high pH, high ash content, rich mineral content, and high mineral contents might have been the main reasons for more effective removal of Pb²⁺ from aqueous solutions by CV-derived biochar. Fourier-transform infrared analysis indicated that surface functional groups such as –OH, CO, –COO–, and C–O; original and newly produced carbonate; and phosphate in CV also led to more effective Pb²⁺ removal efficiency from aqueous solution via surface functional group binding. Thus, pyrolyzing CVs may be used to produce biochar as a cost-effective adsorbent for heavy metal remediation in soil and water in the future.
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24639. 题目: Dissolved organic matter controls of arsenic bioavailability to bacteria
文章编号: N20021205
期刊: Science of The Total Environment
作者: Martin P. Pothier, Véronique Lenoble, Cédric Garnier, Benjamin Misson, Charlotte Rentmeister, Alexandre J. Poulain
更新时间: 2020-02-12
摘要: The presence of arsenic in irrigation and drinking waters is a threat to worldwide human health. Dissolved organic matter (DOM) is a ubiquitous and photoreactive sorbent of arsenic, capable of both suppressing and enhancing its mobility. Microbes can control the mobilization of mineral-bound arsenic, through redox processes thought to occur intracellularly. The role that DOM plays on the bioavailability of arsenic to microbes is often invoked but remains untested experimentally. Here, using a whole-cell biosensor, we tested the role of DOM on As(III) and As(V) bioavailability. Using cation amendments, we explored the nature of As-DOM interactions. We found As bioavailability to be dependent on [As]/[DOM] ratio and on the strength of As binding to DOM which varied as a function of time. We further tested the role of DOM on As(III) photooxidation and showed that As(III) photooxidation rate is limited by the strength of its interactions with DOM and sensitive to ionic competitive desorption. Our study demonstrates the dynamic control that photoreactive DOM poses on the bioavailability and reactivity of As in the environment and highlights the kinetic controls that DOM can possibly exert on As toxicity at various levels in foodwebs.
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24640. 题目: Accumulation of metals and changes in composition of freshwater lake organic sediments during the Holocene
文章编号: N20021204
期刊: Chemical Geology
作者: Karina Stankevica, Zane Vincevica-Gaile, Maris Klavins, Laimdota Kalnina, Normunds Stivrins, Ieva Grudzinska, Enn Kaup
更新时间: 2020-02-12
摘要: The distribution of metals in the strata of sediments deposited in the freshwater environment formed during the Holocene in the territory of Latvia has been studied rather insufficiently. Considering the large volume of accumulated organic matter in sediments, studies on the content of metallic elements in sediments can help to determine the peculiarities of the metal accumulation process in limnic systems and the biogeochemical cycling of metals. Lake Pilvelis, which is located in the eastern part of Latvia (the northern part of Europe), was selected as the main study site. Lake Pilvelis is a small lake of a glacial origin, and >90% of its depression is filled with organic-rich sediments. The development stages of Lake Pilvelis since circa 10,000 cal BP are described in detail via reconstruction of the Holocene palaeoenvironmental conditions using multi-proxy sedimentary records. The elemental composition and content of metallic elements in sapropel are analysed with the main objectives of characterising the accumulation rate of metals in the full profile of sapropel and determining the anthropogenic impact depending on the evolution of the lake and the genesis of sediment organic matter. The correlation among the components characterising sediments such as sapropel and metallic elements revealed that the elemental distribution could be divided into three main groups according to the content of the elements associated with organic compounds (e.g., for Zn and Mn) and mineral compounds (for Ni, Co, Cr, K, Fe, Mg, and Cu). Ni and Co are partly associated with mineral compounds and partly associated with carbonates. A principal component analysis revealed the main factors indicating the origin of metallic elements and the accumulation tendencies of metals in sediment layers: the input of the mineral matter, the characteristics of organic matter, and human impact. The content of metallic elements in sapropel from Lake Pilvelis is mainly affected by the composition of mineral matter, not by the size of the particles.
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