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23561. 题目: Experimental warming and precipitation reduction affect the biomass of microbial communities in a Sphagnum peatland
文章编号: N20021604
期刊: Ecological Indicators
作者: Anna M. Basińska, Monika K. Reczuga, Maciej Gąbka, Marcin Stróżecki, Dominika Łuców, Mateusz Samson, Marek Urbaniak, Jacek Leśny, Bogdan H. Chojnicki, Daniel Gilbert, Tadeusz Sobczyński, Janusz Olejnik, Hanna Silvennoinen, Radosław Juszczak, Mariusz Lamentowicz
更新时间: 2020-02-16
摘要: Due to their unique flora, hydrology and environmental characteristics, peatlands are precious and specific habitats for microorganisms and microscopic animals. Their microbial network structure and their biomass are crucial for peatland carbon cycling, through primary production, as well as decomposition and mineralization of organic matter. Wetlands are one of the ecosystems most at risk from anthropogenic activities and climate change. Most recent scenarios of climate change for Central Europe predict an increase in air temperature and a decrease in annual precipitation. These changes may disturb the biodiversity of aquatic organisms, and the peat carbon sink. Considering the above climatic scenarios, we aimed to: i) assess the response of microbial community biomass to warming and reduced precipitation through the lens of a manipulative experiment in a peatland ecosystem ii) predict how global warming might affect microbial biodiversity on peatlands exposed to warmer temperatures and decreased precipitation conditions. Additionally, we wanted to identify ecological indicators of warming among microorganisms living in Sphagnum peatland. The result of a manipulative experiment carried out at Rzecin peatland (W Poland) suggested that the strongest reduction in microbial biomass was observed in heated plots and plots where heating was combined with a reduction of precipitation. The most pronounced changes were observed in the case of the very abundant mixotrophic testate amoeba Hyalosphenia papilio and cyanobacteria. Shifts in the Sphagnum microbial network can be used as an early warning indicator of peatland warming, especially a decrease in the biomass of important phototrophic microbes living on the Sphagnum capitula, e.g. Hyalosphenia papilio.

23562. 题目: Paddy periphyton reduced cadmium accumulation in rice (Oryza sativa) by removing and immobilizing cadmium from the water–soil interface
文章编号: N20021603
期刊: Environmental Pollution
作者: Haiying Lu, Yue Dong, Yuanyuan Feng, Yanchao Bai, Xianjin Tang, Yuncong Li, Linzhang Yang, Junzhuo Liu
更新时间: 2020-02-16
摘要: Periphyton plays a significant role in heavy metal transfer in wetlands, but its contribution to cadmium (Cd) bioavailability in paddy fields remains largely unexplored. The main aim of this study was to investigate the effect of periphyton on Cd behavior in paddy fields. Periphyton significantly decreased Cd concentrations in paddy waters. Non-invasive micro-test technology analyses indicated that periphyton can absorb Cd from water with a maximum Cd²⁺ influx rate of 394 pmol cm⁻² s⁻¹ and periphyton intrusion significantly increased soil Cd concentrations. However, soil Cd bioavailability declined significantly due to soil pH increase and soil redox potential (Eh) decrease induced by periphyton. With periphyton, more Cd was adsorbed and immobilized on organic matter, carbonates, and iron and manganese oxides in soil. Consequently, Cd content in rice decreased significantly. These findings give insights into Cd biogeochemistry in paddy fields with periphyton, and may provide a novel strategy for reducing Cd accumulation in rice.
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23563. 题目: Effects of excessive impregnation, magnesium content, and pyrolysis temperature on MgO-coated watermelon rind biochar and its lead removal capacity
文章编号: N20021602
期刊: Environmental Research
作者: Jingzhuo Zhang, Deyi Hou, Zhengtao Shen, Fei Jin, David O'Connor, Shizhen Pan, Yong Sik Ok, Daniel C.W. Tsang, Nanthi S. Bolan, Daniel S. Alessi
更新时间: 2020-02-16
摘要: MgO-coated watermelon rind biochar (MWRB) is a potentially highly-effective waste-derived material in environmental applications. This research aims to provide valuable insights into the optimization of the production of MWRB for superior environmental performance. It was found that the Mg content of the MWRB could be easily controlled by adjusting the Mg/feedstock mass ratio during excessive impregnation. The BET surface area was found to first increase and then decrease as the Mg content of the MWRB (produced at 600 °C) increased from 1.52% to 10.1%, with an optimal surface area of 293 m²/g observed at 2.51%. Similarly, an optimum pyrolysis temperature of 600 °C was observed in the range of 400–800 °C for a maximum surface area of the MWRB at a fixed Mg/feedstock ratio of 0.48% (resulting in MWRBs with Mg contents of 1.89–2.51%). The Pb removal capacity of the MWRB (produced at 600 °C) increased with increasing Mg content, with a greatest Pb removal capacity of 558 mg/g found for the MWRB with the highest Mg content (10.1%), an improvement of 208% over the 181 mg/g Pb removal capacity of unmodified WRB produced at 600 °C. The Pb removal capacity of the MWRB (produced with 1.89–2.51% Mg) was also discovered to increase from 81.7 mg/g (at 400 °C) to 742 mg/g (at 700 °C), before dropping to 368 mg/g at 800 °C. These findings suggest that the MWRB can be more efficiently utilized in soil and water remediation by optimizing its synthesis conditions.
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23564. 题目: The influence of corncob-based biochar on remediation of arsenic and cadmium in yellow soil and cinnamon soil
文章编号: N20021601
期刊: Science of The Total Environment
作者: Mingke Luo, Hai Lin, Yinhai He, Ye Zhang
更新时间: 2020-02-16
摘要: Biochar plays a significant role in soil remediation. However, the simultaneous immobilization mechanism and relationship of biochar to cations and anions have never been clear. We designed a batch incubation experiment to investigate the impact of corncob-based biochars to cadmium (Cd) and arsenic (As) contaminations in yellow soil and cinnamon soil, and analyze the relationships among biochars physicochemical characteristics (surface area: SA, total pore volume: TV, average pore size: AV and the C/O rate), soil properties, metals immobilization and microbial diversity indices. Results showed that the modified biochars (inorganic-modified biochar: BCTD) had a good effect on heavy metals immobilization and transformed acid extractable and reducible fraction into the residual fraction. Total nitrogen, organic matter and available potassium increased in both soils after biochar application. The principal component analysis presented that the smaller C/O rate was favorable to As stabilization; the SA and TV of biochar were negatively correlated with the leaching concentration of Cd. The larger surface area, higher porosity and organic matters of biochar were more beneficial to soil microbial diversity. This work not only can demonstrate remediation mechanisms of heavy metals contaminated soil by biochars, but also gain an application of biochars technology in the recycling and reutilize of agricultural waste, and provide a clear strategy for heavy metals contaminated soil, especially As and Cd.
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23565. 题目: Changes in soil microbial activity, essential oil quantity, and quality of Thai basil as response to biofertilizers and humic acid
文章编号: N20021509
期刊: Journal of Cleaner Production
作者: Anahita Boveiri Dehsheikh, Mohammad Mahmoodi Sourestani, Maryam Zolfaghari, Naeimeh Enayatizamir
更新时间: 2020-02-15
摘要: Thai basil (Ocimum basilicum var. thyrsiflorum) is an important medicinal plant that used in pharmaceutical, cosmetic, and food industries. In order to evaluate the effect of biofertilizers and humic acid on secondary metabolites of Thai basil, a factorial experiment; fertilizer treatments (Control, NF (nitrogen-fixing bacterium), PS (phosphate solubilizing bacteria), combination of NF and PS, chemical fertilizer, combination of NF and PS + 50% chemical fertilizer) and humic acid (0 and 20 kg ha−1) was conducted. The soil microbial respiration and carbon biomass, soil organic matter, leaf nitrogen and phosphorus elements, number and size of glandular trichomes as well as the quantity and quality of the essential oil were evaluated. Results showed that the application of biofertilizers greatly caused to increase 60% in soil microbial respiration (1.11 CO2 g−1 dry soil day−1) and 3-fold in carbon biomass (117.47 mg C 100 g−1 dry soil) than control. The use of humic acid enhanced the soil organic matter by 2-fold (1.15%) more than control. The highest value of phosphorus element (0.67%), size of glandular trichomes in upper (411.11 μm2) and lower (419.31 μm2) surfaces, and essential oil content (2.81%) were obtained in the inoculation of plants by PS and the lowest values were observed in control. The combination of NF and PS + 50% chemical fertilizer led to increment 45% in the nitrogen element (3.42%), 1.5-fold in number of glandular trichomes in upper (5.03 number mm−2) and lower (6.22 number mm−2) surfaces and 80% essential oil yield (7.89 g m−2) compared to the control. The maximum amount of methyl chavicol (66.26%), eucalyptol (12.98%), linalool (5.42%), and β-pinene (2.15%) was recorded in combination of NF and PS + 50% chemical fertilizer and the minimum amounts were detected in control. Despite the positive effect of the simultaneous application of humic acid and biofertilizers treatment on the soil organic matter, nitrogen element and some major oil components, humic acid had no significant impact on the phosphorus concentration, size of glandular trichomes and essential oil content and yield. Further investigation is needed to use humic acid in plant nutrition management. In conclusion, combination of NF and PS + 50% chemical fertilizer can be recommended as a suitable solution to reduce the demand for chemical fertilizers and their environmental hazards in warm regions.

23566. 题目: Plant-induced insoluble Cd mobilization and Cd redistribution among different rice cultivars
文章编号: N20021508
期刊: Journal of Cleaner Production
作者: Xinyang Li, Peiqin Peng, Jian Long, Xia Dong, Kai Jiang, Hongbo Hou
更新时间: 2020-02-15
摘要: Selecting rice varieties that adsorb less or more Cd from soil can be respectively applied to safety rice production and phytoremediation. Considering plant-induced Cd mobilization will contribute to the rice cultivar screening. We firstly executed a pot experiment to assess the effect of rice plants on soil Cd forms (BCR method). The results showed that the presence of rice significantly reduced residual-Cd (BCR4) concentrations, indicating the rice plant-induced insoluble Cd mobilization. Subsequent sand culture trial with four rice species (conventional and hybrid low-Cd rice, conventional and hybrid high-Cd rice) and four insoluble Cd compounds (CdS, [Cd3(PO3)2], CdCO3 and CdSe) were conducted to further discuss the interaction between insoluble Cd among different rice varieties. The results showed that rice plants do solubilize soil Cd especially insoluble Cd form due to the interaction among rhizosphere acidification, root secretion of organic matter ligand and other ligands, like phytosiderophore. High-Cd cultivar and hybrid rice cultivar had a greater ability to solubilize the insoluble Cd. Visual MINTEQ predicted that free Cd2+ (∼85.6%) were the dominant Cd speciation of mobilized Cd followed by Cd-DOM complexes (∼7.80%) and other ligand-complexes (∼6.51%) in the rhizosphere solution. Cd bound to protein and pectates and to undissolved phosphate were the major mobilized-Cd chemical forms in rice roots and shoots. In addition, the subcellular analysis suggested that half of mobilized-Cd precipitated in the cell wall of rice root and shoot and the other Cd entranced into the protoplast of rice cell. The fate of rice plant-induced insoluble Cd mobilization could be an indispensable factor in prospective phytoremediation and cleaner rice production.

23567. 题目: Efficient removal of refractory organics in landfill leachate concentrates by electrocoagulation in tandem with simultaneous electro-oxidation and in-situ peroxone
文章编号: N20021507
期刊: Environmental Research
作者: Ghulam Sarwar Soomro, Chao Qu, Na Ren, Shujuan Meng, Xiaohu Li, Dawei Liang, Shujun Zhang, Yangang Li
更新时间: 2020-02-15
摘要: Leachate concentrates, an effluent produced from nanofiltration and/or reverse osmosis, contains a high amount of salts and dissolved organics especially refractory organics. Thus, the treatment of leachate concentrates would consume high energy or a large amount of chemicals. The present study is to develop an effective treatment method by using coupled electrochemical methods with the least possible energy consumption. The leachate concentrates was pretreated by electrocoagulation (EC), with aluminum or iron electrodes as anodes, to decrease the dissolved organic concentration. EC with Al electrode was found to be more efficient by consuming 1.25 kWh/m3 energy to remove 70% of TOC. EC effluent was further subjected to a novel simultaneous electro-oxidation and in-situ peroxone process, which used a Ti-based nickel and antimony doped tin dioxide (NATO) as anode and a carbon nanotubes coated carbon-polytetrafluoroethylene (CNTs-C/PTFE) as cathode for oxygen reduction reaction (ORR). Compared with a traditional EO with cathode for hydrogen evolution reaction (HER-EO), ORR-EO obtained higher efficiency and lower energy consumption of 26.25 kWh/m3, which was much lower than 35.5 kWh/m3 for HER-EO. Results showed that after ORR-EO, a final TOC of 57.3 mg/L was obtained. Thus, EC in tandem with ORR-EO process has an excellent capability and economic merit in the field of treating leachate concentrates.

23568. 题目: Susceptible soil organic matter, SOM, fractions to agricultural management practices in salt-affected soils
文章编号: N20021506
期刊: Geoderma
作者: Mohamed Emran, Serena Doni, Cristina Macci, Grazia Masciandaro, Mohamed Rashad, Maria Gispert
更新时间: 2020-02-15
摘要: In the recent decades, soil salinity became the main human-induced soil degradation causes in Egypt’s Nile Delta Valley (ENDV) by affecting the stabilization processes of soil organic matter (SOM). However, soil organic carbon (SOC) is highly conserved by aggregating the stabilized organic molecules under sound agricultural management. In particular, labile SOM fractions assumed to be dually influenced by salinity and agricultural management practices other than the stabilized fractions. This work aimed to study various labile and stable SOM fractions that are more susceptible to the current agricultural practices in salt-affected soils of the ENDV area. Three different agro-ecological sites were studied: Eastern (EH, EM soils) and Western (WM, WL soils) Delta regions dominated by Vertic Torrifluvents, and Coastal region (NCH, NCM soils) dominated by Typic Calcitorrerts of high CaCO₃ contents. Two different salinity levels were detected in each site; low in WL soils, medium in WM, NCM, and EM soils, and high in EH and NCH soils. The least values in EM, WL, and NCM soils were due to the recurrent legume applications. The carbon content of glomalin-related soil protein (GRSP) (C-GRSP) was positively correlated with SOC and water-extractable organic carbon (WEOC) fraction confirming the contribution of GRSP to the stabilization of SOM. The lower soil β-glucosidase, phosphatase, and protease enzymes activities were in those soils with larger salinity levels in each site as NCH < NCM, WM < WL, and EH < EM reflecting the effect of soil salinity and CaCO₃ contents on soil metabolic activities. Extracted organic carbon (EOC) in both humic and fulvic fractions was higher in EH, WM, WL, and EM soils than in NCH and NCM soils. The chemical composition of SOM obtained by the pyrolysis gas chromatography showed that lignocellulosic and condensed aromatic structures in SOM increased significantly with CaCO₃ and salinity. In conclusion, the considered SOM fractions such as WEOC, EOC, GRSP, C-GRSP, together with the pyrolytic results can be considered as significant indicators in the dynamic stability of SOM. Intercropping with legumes may increase the stability of SOM fractions in salt-affected soils of degraded lands. In calcareous soils, severe alteration in SOC conservation was observed and negatively influenced the active constituents of SOM.

23569. 题目: Methane emissions and associated microbial activities from paddy salt-affected soil as influenced by biochar and cow manure addition
文章编号: N20021505
期刊: Applied Soil Ecology
作者: Binh Thanh Nguyen, Nam Ngoc Trinh, Quang-Vu Bach
更新时间: 2020-02-15
摘要: Although previous studies showed that biochar can mitigate methane emissions through microbial activities from paddy fields, little is known about its effects on salt-affected soil. The current study aims to examine the interactive effect of biochar and cow manure (CM) on (1) methane emissions from salt-affected soil and (2) methanogenic and methanotrophic activities to identify potential mechanisms for the emissions. A two-factor pot experiment was set up, following a randomized complete block design with four replicates. Paddy rice (Oryza sativa L.) was grown on six treatments (no CM + no biochar; no CM + rice husk biochar; no CM + rice straw biochar; CM + no biochar; CM + rice husk biochar; CM + rice straw biochar). Methane emissions from salt-affected soil were relatively low and CM addition significantly increased CH₄ emissions (by 801%). For the CM treatments, biochar addition significantly reduced methane emissions (by 28 to 680%), but for the non-CM treatments, biochar addition showed no clear effect. The increase in methane emissions by CM could be involved in the improved relative abundance of methanogenic and methanotrophic genes. In contrast, the reduction of methane emissions by biochar was likely related to the reduced abundance of methanogenic and increased that of methanotrophic genes. In brief, low methane emissions from salt-affected soil were increased by CM addition and biochar addition could mitigate the CM's effect. Balancing methanogenic and methanotrophic activities could serve as a major mechanism in determining methane emissions from salt-affected soil added with cow manure and biochar.

23570. 题目: Influence of sediment organic carbon on toxicity depends on organism’s trophic ecology
文章编号: N20021504
期刊: Environmental Pollution
作者: Mariana Aliceda Ferraz, Rodrigo Brasil Choueri, Ítalo Braga Castro, Cecília Simon da Silva, Fabiane Gallucci
更新时间: 2020-02-15
摘要: Studies which showed the influence of organic carbon on the toxicity of sediment-associated contaminants on benthic invertebrates suggest this was primarily due to its influence on the interstitial water concentrations of the contaminant. A higher organic content offers more binding sites for organic contaminants, which means lower toxicity for organisms whose exposure route is mainly through contaminated interstitial water. However, a higher organic content in the sediment could mean a higher toxicity for deposit-feeding organisms, which can assimilate the contaminant by ingestion of contaminated particles. To investigate the influence of sedimentary organic carbon content on the toxicity of an organic contaminant on a benthic community, a microcosm experiment was carried out where natural nematode assemblages were exposed to three concentrations of Irgarol in sediments with two different levels of organic carbon for 7 and 35 days. The response of the nematode assemblage to sediment contamination by Irgarol differed between organically “Lower organic carbon” and “Higher organic carbon” sediments. Responses were genus specific and although community composition was the same in both sediments in the beginning of the assay, contamination by Irgarol affected different genera at each sediment type. Also, the differential amount of organic carbon promoted responses of different functional groups. In Lower organic carbon sediments, contaminated treatments showed lower abundances of the genus Viscosia and the group of predacious nematodes, which were probably affected by an increased availability of Irgarol in the interstitial water in this treatment. In Higher organic carbon sediments, the group of deposit-feeders were mainly affected, suggesting the ingestion of contaminated food as the main route of contamination in this condition. These results indicate that the bioavailability of toxic substances in sediments is not only determined by their partitioning between the different phases of the sediment but also by the organism’s trophic ecology.
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23571. 题目: Examining the correlation between quantifiable SVOCs and organic carbon content or particulate size in benthic sediments as a function of ocean stratum
文章编号: N20021503
期刊: Environmental Science: Processes Impacts
作者: Ochan Otim
更新时间: 2020-02-15
摘要: The raw analytical concentration values of semi-volatile organic compounds (SVOCs) in ocean sediments do not necessarily reflect the bioavailable fractions of SVOCs in the sediments due to factors such as the total organic carbon content of sediment (TOC) and the percentage of fine particles in sediments (% Fines) believe to affect the extraction efficiency of SVOCs from sediment. Corrective actions are therefore taken to minimize their influence on measurements. In doing so, a broad and uniform correlation is assumed between the ‘native’ levels of the SVOCs and TOC or %Fines across ocean strata. Not yet verified though is the validity of this blanket assumption. In this study, we examined the strength of the assumption using levels of DDTs, PAHs and PCBs in sediments from Santa Monica Bay (SMB) in California, USA. (The distribution patterns of these SVOCs in SMB are known and reproducible for quality assurance.) As our results show, a uniform correlation between SVOCs levels and TOC or %Fines across strata is mostly unsupported. For example, while PAHs and PCBs levels show negative correlation with TOC or % Fines, and only in canyon sediments, DDTs levels correlate positively with both TOC and %Fines across at least three strata. Furthermore, the distribution of PAH molecules appears to be controlled by molecular size with the smaller PAHs found almost exclusively in the canyons. Our findings here, being the first of its kind, suggest that more work is actually needed to clarify the reporting of SVOCs levels in ocean sediments.

23572. 题目: Spatiotemporal distribution, source, and ecological risk of polycyclic aromatic hydrocarbons (PAHs) in the urbanized semi-enclosed Jiaozhou Bay, China
文章编号: N20021502
期刊: Science of The Total Environment
作者: Yuanxin Cao, Ming Xin, Baodong Wang, Chunye Lin, Xitao Liu, Mengchang He, Kai Lei, Ling Xu, Xuan Zhang, Shuang Lu
更新时间: 2020-02-15
摘要: Coastal contamination by polycyclic aromatic hydrocarbons (PAHs) is a worldwide issue. Nevertheless, the spatiotemporal distribution of PAHs in the urbanized semi-enclosed bays in China remains relatively uncharacterized. Here we present measurements of 15 priority PAHs in the water and sediment of the Jiaozhou Bay, as well the assessment of their spatiotemporal distribution, sources and ecological risk. The total PAH (ΣPAH) concentrations ranged from 23.6 to 86.2 ng L ⁻¹ in the water and from 37.7 to 290.9 ng g⁻¹ in the sediment. The average ΣPAH concentration in the water was significantly higher in the winter (52.8 ng L ⁻¹) than in the spring (30.4 ng L ⁻¹) (α = 0.05 level). Average concentration of phenanthrene in the water was 8.9 ng L⁻¹ in the spring and 15.7 ng L⁻¹ in the winter and the highest of PAHs, contributing about 29.4% to ΣPAHs. Compared with three-ring PAHs, four- and five-ring PAHs were more tended to accumulate in the sediment, and the partitioning into sediment was influenced by the water salinity. The spatial distribution of ΣPAH concentrations in the water were controlled by water exchange capability. Organic matter content and sediment texture played important roles in determining the spatial distribution of ΣPAHs in the sediment. Molecular diagnostic ratio analysis indicated that pyrogenic source was the main source for PAHs in the Bay. Specifically, the positive matrix factorization (PMF) model indicated that vehicle emission, biomass combustion, coal combustion, and petrogenic sources contributed for 41.6, 20.2, 20, and 18.2% of ΣPAHs, respectively. The risk assessment by sediment quality guidelines suggested that adverse biological effects are expected to occur rarely in the sediment.
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23573. 题目: Riparian land cover and hydrology influence stream dissolved organic matter composition in an agricultural watershed
文章编号: N20021501
期刊: Science of The Total Environment
作者: Oliva Pisani, David D. Bosch, Alisa W. Coffin, Dinku M. Endale, Dan Liebert, Timothy C. Strickland
更新时间: 2020-02-15
摘要: Dissolved organic matter (DOM) represents an essential component of the carbon cycle and controls biogeochemical and ecological processes in aquatic systems. The composition and reactivity of DOM are determined by the spatial distribution of its sources and its residence time in a watershed. While the effects of agricultural land cover on DOM quality have been reported across spatial and temporal scales, the influence of riparian land cover on stream DOM composition has received little attention. Furthermore, the combined effects of riparian land cover and streamflow rates on DOM composition require investigation. To this end, a multi-year (2016–2018) DOM characterization study was conducted using bi-weekly water samples collected from seven sub-watersheds nested within the Little River Experimental Watershed (LREW) near Tifton, Georgia, USA. DOM optical properties were determined to assess compositional variations using UV–Vis and excitation-emission matrix (EEM) fluorescence spectroscopy coupled with parallel factor (PARAFAC) analysis. PARAFAC analysis indicated that DOM in the LREW was dominated by three humic-like fluorescing components of terrestrial, microbial, and anthropogenic origin and a protein-like component. DOM composition was influenced by riparian land cover and hydrology, and shifted towards recently produced, low molecular weight DOM with low aromaticity as the percentage of agricultural land within riparian wetlands increased. During periods of high discharge and high baseflow, the DOM pool was dominated by recalcitrant and terrestrial-derived material but shifted towards protein-like and microbial-derived with increasing cropland in the riparian area. The results of this two-year study indicate that the replacement of forested riparian buffers with agricultural land can result in altered DOM composition which may affect carbon cycling and downstream water quality in agricultural watersheds.
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23574. 题目: Molecular Identification of Water-Extractable Organic Carbon from Thermally Heated Soils: C-13 NMR and Accurate Mass Analyses Find Benzene and Pyridine Carboxylic Acids
文章编号: N20021415
期刊: Environmental Science & Technology
作者: E. Michael Thurman, Yun Yu, Imma Ferrer, Kevin A. Thorn, Fernando L. Rosario-Ortiz
更新时间: 2020-02-14
摘要: To simulate the effects of wildfire on the combustion process in soils and their potential to leach organic compounds into streams and groundwater, mineral soil samples were heated at temperatures of 150–550 °C. Then, the soils were leached with deionized water, filtered, and analyzed for dissolved organic carbon. The water extract was concentrated by both XAD-8 and XAD-4 resins and analyzed by C-13 nuclear magnetic resonance and liquid chromatography time-of-flight mass spectrometry. Approximately 15–20% of the water-extractable organic carbon was identified as benzene dicarboxylic acids, tricarboxylic acids, and tetracarboxylic acid isomers, commonly called BPCAs. Also identified were isomers of pyridine dicarboxylic acids and tricarboxylic acids (PCAs). The conversion of soil organic carbon to BPCAs occurs at 250 °C and reaches a maximum between 350 and 450 °C. At higher temperatures (>450 °C), the BPCA concentrations decrease, suggesting decarboxylation and conversion to carbon dioxide and water. This is the first report of BPCAs and PCAs in water-extractable organic carbon from thermally altered soil and suggest that these compounds are possible candidates for further water-quality studies in watersheds affected by wildfire. Finally, BPCAs and PCAs could contribute to the black carbon and nitrogen in seawater and are worthy of future investigation.

23575. 题目: Application of Hydrochar Altered Soil Microbial Community Composition and the Molecular Structure of Native Soil Organic Carbon in a Paddy Soil
文章编号: N20021414
期刊: Environmental Science & Technology
作者: Ke Sun, Lanfang Han, Yan Yang, Xinghui Xia, Zhifeng Yang, Fengchang Wu, Fangbai Li, Yanfang Feng, Baoshan Xing
更新时间: 2020-02-14
摘要: The benefits and disadvantages of hydrochar incorporation into soil have been heavily researched. However, the effect of hydrochar application on the soil microbial communities and the molecular structure of native soil organic carbon (SOC) has not been thoroughly elucidated. This study conducted an incubation experiment at 25 °C for 135 days using a soil column with 0.5 and 1.5% hydrochar-amended paddy soil to explore the interconnections between changes in soil properties and microbial communities and shifts in native SOC structure using electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI-FT-ICR-MS) and NMR after hydrochar application. Hydrochar addition decreased the labile SOC fraction by 15.6–33.6% and increased the stable SOC fraction by 10.3–27.0%. These effects were significantly stronger for 1.5% hydrochar-treated soil. Additionally, hydrochar addition induced the native SOC with 1.0–3.0% more carbon and 6.0–13.0% higher molecular weight. The SOC in hydrochar-amended soil contained more aromatic compounds but fewer carbohydrates and lower polarity. This was resulted by a statistically significant reduction in Sphingobacterium, which was active in polycyclic aromatic hydrocarbon degradation, and an increase in Flavobacterium, Anaerolinea, Penicillium, and Acremonium, which were the efficient decomposers of labile SOC. These findings will help elucidate the potential influence of hydrochar on the carbon biogeochemical cycle in the soil.

23576. 题目: Major role of particle fragmentation in regulating biological sequestration of CO 2 by the oceans
文章编号: N20021413
期刊: Science
作者: Nathan Briggs, Giorgio Dall’Olmo, Hervé Claustre
更新时间: 2020-02-14
摘要: A critical driver of the ocean carbon cycle is the downward flux of sinking organic particles, which acts to lower the atmospheric carbon dioxide concentration. This downward flux is reduced by more than 70% in the mesopelagic zone (100 to 1000 meters of depth), but this loss cannot be fully accounted for by current measurements. For decades, it has been hypothesized that the missing loss could be explained by the fragmentation of large aggregates into small particles, although data to test this hypothesis have been lacking. In this work, using robotic observations, we quantified total mesopelagic fragmentation during 34 high-flux events across multiple ocean regions and found that fragmentation accounted for 49 ± 22% of the observed flux loss. Therefore, fragmentation may be the primary process controlling the sequestration of sinking organic carbon.

23577. 题目: Effects of straw and its biochar applications on the abundance and community structure of CO 2 -fixing bacteria in a sandy agricultural soil
文章编号: N20021412
期刊: Journal of Soils and Sediments
作者: Peipei Li, Wenju Chen, Yanlai Han, Daichang Wang, Yuting Zhang, Chuanfa Wu
更新时间: 2020-02-14
摘要: Purpose: Crop straw and biochar application can potentially increase carbon sequestration and lead to changes in the microbial community in agricultural soils. Sequestration of CO₂ by autotrophic microorganisms is key to biogeochemical carbon cycling in soil ecosystems. The effects of straw and its biochar, derived from slow pyrolysis, on CO₂ fixation bacteria in sandy soils, remain unclear. Therefore, this study compared the response of abundance and community of CO₂ fixation bacteria to the two straw application methods in a sandy agricultural soil. The overall aim of the study was to achieve an efficient use of straw residues for the soil sustainablility. Materials and methods: We investigated the soil organic carbon content and autotrophic bacteria over four consecutive years (2014–2018) in a field experiment, including the following four treatments: whole maize straw amendment (S), whole maize straw translated biochar amendment (B), half biochar and half straw amendment (BS), and control (CK) without straw or biochar amendment. The autotrophic bacterial abundance and community structure were measured using molecular methods of real-time PCR, terminal restriction fragment length polymorphisms (T-RFLP), and a clone library targeting the large subunit gene (cbbL) of ribulose-1,5-bisphosphate carboxylase/oxygenase. Results and discussion: The results showed that the content of soil total organic carbon (TOC), dissolved organic carbon (DOC), and microbial biomass carbon (MBC) in B, S, and BS treatments was significantly increased compared with the CK treatment. Soil TOC and available potassium (AK) in the B treatment significantly increased by 15.4% and 23.3%, respectively, but soil bulk density, DOC, and MBC significantly decreased by 8.5%, 10.6%, and 14.5%, respectively, compared with the S treatment. The abundance of the cbbL gene as well as of the bacterial 16S rRNA gene increased significantly in straw or biochar application treatments as compared to the CK treatment. The B treatment, but not the BS treatment, significantly increased the cbbL gene abundance when compared to the S treatment. No significant differences were observed in the bacterial 16S rRNA gene abundance among the three straw or biochar applications. The application of straw biochar could increase the diversity of the autotrophic bacteria, which also altered the overall microbial composition. Physicochemical properties of the soil, such as soil pH, SOC, and bulk density, can help explain the shift in soil microbial composition observed in the study. Conclusions: Taken together, our results suggest that straw biochar, rather than straw application, leads to an increase in the abundance and diversity of CO₂-fixing bacteria, which would be advantageous for soil autotrophic CO₂ fixation.

23578. 题目: Seasonal irrigation affects the partitioning of new photosynthate carbon in soil
文章编号: N20021411
期刊: Soil Biology and Biochemistry
作者: Carmen R. Carmona, Timothy J. Clough, Samuel R. McNally, Michael H. Beare, Craig S. Tregurtha, John E. Hunt
更新时间: 2020-02-14
摘要: Long-term irrigation of temperate pastures has been reported to either increase or decrease soil organic carbon (SOC) stocks when compared with dryland systems. Understanding the short-term effects of irrigation on the fixation and partitioning of carbon (C) to plant and soil components may be important to explaining the observed differences. Continuous ¹³CO₂ pulse labelling of ryegrass (Lolium perenne L.) and white clover (Trifolium repens L.) planted mesocosms was used to quantify the net accumulation and partitioning of new photosynthate C to above- and below-ground components of the plant-soil system, including soil particle size fractions: > 250 μm, 53–250 μm, 20–53 μm, 5–20 μm and <5 μm, under simulated irrigation and dryland conditions.After the ¹³CO₂ labelling, irrigation increased the quantity of ¹³C partitioned into herbage by 16%, while reducing the quantity partitioned into roots in the 15–25 cm soil depth by 35%. However, less new photosynthate C was observed in rhizosphere soil (0–15 cm depth), while more new photosynthate C was partitioned into the 53–250 μm and <5 μm soil fractions under irrigation. Despite these differences, the net amount of new photosynthate C in the whole soil (0–25 cm depth) was similar between treatments (2511 kg new C ha⁻¹ dryland and 2509 kg new C ha⁻¹ irrigated). Therefore, Irrigation did not increase the net amount of new photosynthate C in the soil despite increased above-ground pasture productivity.Based in our results, we hypothesise that the recently reported losses of SOC from irrigated pastures may be driven by faster turnover of root-derived C, which may explain the increase in photosynthate C in the fine POM soil size fraction (53–250 μm), rather than a reduction in photosynthate C inputs to the soil.
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23579. 题目: Evolution of the functionalities and structures of biochar in pyrolysis of poplar in a wide temperature range
文章编号: N20021410
期刊: Bioresource Technology
作者: Chenting Zhang, Zhanming Zhang, Lijun Zhang, Qingyin Li, Cuncheng Li, Guozhu Chen, Shu Zhang, Qing Liu, Xun Hu
更新时间: 2020-02-14
摘要: This study studied the change of functionalities in the biochar formed in pyrolysis of poplar wood in a wide range of temperature. The in situ Diffuse Reflectance Infrared Fourier transform spectroscopy characterization indicated that aldehydes and ketones functionalities formation initiated at 100°C, dominated at 300 to 500°C. Carboxyl group was less stable than carbonyls. Cellulose crystal in poplar decomposed slightly at 300°C and significantly at 350°C. The temperature from 250 to 350°C significantly affected biochar yields, while the drastic fusion of the ring structures in biochar occurred from 550 to 650°C, making biochar more aliphatic while less more aromatic. High pyrolysis temperature also created more defective structures in the biochar and favored the absorption of the CO₂ generated during the pyrolysis. The results provide the reference information for understanding the structural configuration and evolution of the functionalities during in pyrolysis of poplar biomass.
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23580. 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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