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12861. 题目: Response of organic carbon in drainage ditch water to rainfall events in Zoige Basin in the Qinghai-Tibet Plateau
文章编号: N19100302
期刊: Journal of Hydrology
作者: Danyang Wang, Zhiwei Li, Zhongwu Li, Wenming Ma, Xiaodong Nie
更新时间: 2019-10-03
摘要: Rainfall events have been reported of great influence on concentration and flux of aquatic organic carbon, but little is known in ditch water of peatlands. In this work we chose a ditch located in a peatland of Zoige Basin in northeastern Qinghai-Tibet Plateau, and studied the response of organic carbon (in dissolved form (DOC) and in particulate form (POC)) to rainfall events with varying intensity. Organic carbon dynamics during four rainfall events were recorded in the growing season of 2016. During events, evident but different trends in both POC and DOC were observed. POC steeply increased through the rising limb of the hydrograph to maximum concentrations following the discharge peaks and followed by steep decrease, while dilution effect on DOC was observed. Different temporal patterns between POC and DOC indicated that they were transported through different flow paths. The dilution in DOC was attributed to rainwater mixing with overland flow induced by infiltration excess runoff, rainwater directly fell into the ditch and mixed with ditch water, and sampling uncertainties. Rainfall intensity had strong influence on organic carbon. The higher rainfall intensity, the higher fluctuation and higher maximum value as well as mean value of POC/DOC concentration. The investigation of the response of organic carbon to rainfall events and the mechanisms responsible is important for assessing impacts on peatland ecosystem processes.

12862. 题目: Dynamic biochar effects on nitrogen use efficiency, crop yield and soil nitrous oxide emissions during a tropical wheat-growing season
文章编号: N19100301
期刊: Journal of Environmental Management
作者: Thalita Fernanda Abbruzzini, Christian Andrew Davies, Fernando Henrique Toledo, Carlos Eduardo Pellegrino Cerri
更新时间: 2019-10-03
摘要: The application of biochar to soil combined with synthetic fertilizers has been proposed for enhancing N availability to plants and crop yields while reducing nitrous oxide (N2O) emissions. However, little is known about those interactions for tropical soils. Thus, this study evaluated the effects of sugarcane straw biochar on tropical soil attributes, crop productivity, N2O emissions and N use efficiency. It was conducted a greenhouse pot experiment with wheat cultivation using a15N-labelled source (NH415NO3). The treatments evaluated were: Soil, with N, no biochar; Soil, with N and biochar at rates equivalent to 0.4%, 0.8% and 1.9% (w/w); and a control (soil only). Increasing biochar amendments decreased cumulative N2O emissions by 71% compared to the fertilized, no-biochar soil. Moreover, increasing biochar rates to soil increased available P up to 30% and led to 8-fold higher exchangeable K+ concentrations. Grain yield and shoot biomass increased by 27 and 16%, respectively, with the rate of 1.9% biochar to soil, which also resulted in higher tillering and number of heads compared to fertilized, no-biochar soil. The amount of 15N in grains was 28% higher with 0.8 and 1.9% of biochar compared to no-biochar soil, which correspond to 25% of the total 15N-labelled fertilizer applied to soil. The 15N loss by volatilization did not differ between treatments. Nevertheless, the biochar amended soils produced less N2O than the no-biochar treatment, indicating that biochar amendment to tropical soil led to gaseous N losses in forms other than N2O. The application of biochar to soil improved N utilization and the efficiency with which N is acquired by the plants and converted to grain yield, thereby enhancing crop performance, while simultaneously reducing N2O emissions from N fertilization, thus mitigating GHG emissions to the atmosphere under tropical conditions.
图文摘要:

12863. 题目: Mechanisms of Organic Matter Export in Estuaries with Contrasting Carbon Sources
文章编号: N19100203
期刊: Journal of Geophysical Research: Biogeosciences
作者: A.R. Arellano, T.S. Bianchi, C.L. Osburn, E.J. D'Sa, N.D. Ward, D. Oviedo‐Vargas, I.D. Joshi, D.S. Ko, M.R. Shields, G. Kurian, J. Green
更新时间: 2019-10-02
摘要: Modifications in land‐use and climate will result in shifts in the magnitude and composition of organic matter (OM) transported from wetlands to coastal waters, but differentiation between riverine and wetland OM sources in coastal areas remains a challenge. Here, we evaluate particulate and dissolved OM export dynamics in two representative estuary geomorphologies—Apalachicola Bay (AP) and Barataria Bay (BB), characterized primarily by blackwater river inputs and high particle abundance, respectively. The magnitude and composition of OM exported from each estuary was evaluated based on seasonal measurements of surface water dissolved organic carbon (DOC), particulate organic carbon (POC), particulate nitrogen (PN), the stable isotopic composition of DOC and POC (δ13C‐DOC and δ13C‐POC, respectively), dissolved and particulate lignin phenols, and carbon‐normalized dissolved lignin‐phenol yields. Data and discriminant analyses support the initial hypothesis; AP is dominated by a more terrestrial source of organic matter due to importance of fluvial DOM inputs, while BB is a more particle‐rich and wetland‐carbon dominated system. Total lignin export (sum of mean dissolved and mean particulate) was higher in BB (5.73±2.50×105 kg yr‐1) than in AP (4.21±2.35×105 kg yr‐1). Particulate lignin export from BB was greater than the export of dissolved lignin at either BB or AP, suggesting coastal marsh erosion may be driving this comparatively large export of particulate lignin. These data have important implications for the stability of stored OM in coastal habitats, particularly since such habitats in this region are highly vulnerable due to relative sea level rise.

12864. 题目: Wheat‐derived soil organic carbon accumulates more than its maize counterpart in wheat‐maize cropping system after 21 years
文章编号: N19100202
期刊: European Journal of Soil Science
作者: Xinliang Dong, Hongyong Sun, Jintao Wang, Xiaojing Liu, Bhupinder Pal Singh
更新时间: 2019-10-02
摘要: Fertilization is the most common way to supply nutrients to the soil and to maintain crop productivity in agricultural ecosystems, which may also influence soil organic carbon (SOC) accumulation rates. In 1996, we set up a long‐term field experiment to explore the effect of fertilization on soil properties in a winter wheat‐summer maize cropping system in the North China Plain. Eight treatments include no fertilization (Ct), nitrogen (N), phosphorus (P) and N combined with P (NP) fertilizer application with or without potassium (K). After 21 years of fertilization, N application did not increase soil total N content, but P application significantly increased soil total P contents by 33.9%. The single application of N or P did not significantly affect SOC content, while the NP combination significantly increased SOC contents by 22.1% and 29.6% compared to Ct in the no K and K treatments, respectively. The natural 13C abundance approach and the SOC contents suggested that the NP combination increased C3 wheat‐derived SOC by 37.5% and 49.8% in the no K and K treatments; however, fertilization had no impact on C4 maize‐derived SOC content. Wheat‐derived SOC was positively correlated to the wheat yield, while maize‐derived SOC was not correlated to the maize yield, which indicated that wheat‐derived SOC accumulated more than maize‐derived SOC in the wheat‐maize cropping system. In addition, soil inorganic carbon (SIC) and its compositions were not affected by the long‐term fertilization. Our results indicate that N combined with P application is more beneficial than N or P alone to enlarge SOC sequestration, especially for wheat‐derived SOC. Thus, in soil with nutrient limitations, the nutrient resources should be supplied with a priority to the wheat growing season in wheat‐maize cropping systems, to maintain or enlarge soil C storage.

12865. 题目: Carbon stable isotope patterns of cyclic terpenoids: A comparison of cultured alkaliphilic aerobic methanotrophic bacteria and methane-seep environments
文章编号: N19100201
期刊: Organic Geochemistry
作者: Alexmar Cordova-Gonzalez, Daniel Birgel, Andreas Kappler, Jörn Peckmann
更新时间: 2019-10-02
摘要: Aerobic methanotrophic bacteria are known to synthesize a variety of cyclic terpenoids which are typified by 13C-depleted, methane-derived carbon. This peculiarity facilitates identification of methanotroph biomarkers in natural samples. However, the current biomarker database does not always allow biomarker patterns of marine samples to be assigned to the different types of aerobic methanotrophs. To overcome this shortcoming, the carbon stable isotope composition of cyclic terpenoids of two strains of the Type I methanotroph genus Methylomicrobium was analyzed. Other than aerobic methanotrophs used for biomarker studies in the past, these two strains deriving from soda lake environments are able to tolerate the conditions typifying marine environments including high alkalinity and salinity. The cyclic terpenoid inventory of the two strains comprises 4-methyl steroids, 3-methyl- and desmethyl bacteriohopanepolyols (aminotetrol and aminotriol), and tetrahymanol, all of which are 13C-depleted. The average carbon isotope fractionation between methane and the respective lipid (Δδ13Cterpenoid-methane) is found to be −25‰ for M. kenyense and −16‰ for M. alcaliphilum. These data shed new light on the previously reported compound and carbon stable isotope patterns of cyclic terpenoids from methane-seep environments. Particularly, 13C-depleted tetrahymanol and gammacerane are reinterpreted as biomarkers of aerobic methanotrophic bacteria based on their occurrence in methane-seep deposits in association with other biomarkers of aerobic methanotrophs. The use of δ13C values of anaerobic methane-oxidizing archaea (ANME) lipids for the reconstruction of the isotopic composition of parent methane allows us to calculate the Δδ13Cterpenoid-methane even for ancient seep environments. With this calculation, Type I and Type II methanotrophs can be discriminated, representing a new approach to better characterize past methanotrophy at seeps and possibly other marine environments.

12866. 题目: Responses of surface SOC to long‐term experimental warming vary between different heath types in the High Arctic tundra
文章编号: N19100108
期刊: European Journal of Soil Science
作者: J. Y. Jung, A. Michelsen, M. Kim, S. Nam, N. M. Schmidt, S. Jung, Y. H. Choe, B. Y. Lee, H. I. Yoon, Y. K. Lee
更新时间: 2019-10-01
摘要: Over the past few decades the Arctic has warmed up more than the lower latitudes. Soil organic carbon (SOC) in the Arctic is vulnerable to climate change, and carbon dioxide produced via SOC decomposition can amplify atmospheric temperature increase. Although SOC composition is relevant to decomposability, studies on its compositional changes with warming are scarce, particularly in the Arctic. Therefore, we investigated the responses of SOC and the bacterial community to climate manipulation under Cassiope and Salix heath vegetation communities in permafrost‐affected soil in Zackenberg, Greenland. After 8‐9 years of experimental warming, we evaluated changes in SOC quantity and quality of three density fractions of soil: free light fraction (FLF), occluded light fraction (OLF) and heavy fraction (HF). The SOC content at 0‐5 cm depth was significantly reduced with warming under Cassiope, and it was accompanied by decreased FLF content, attributed to accelerated decomposition of the FLF by warming. However, SOC molecular composition and bacterial community composition were not affected by warming. By contrast, there was no warming effect on SOC under Salix, which could be partially due to smaller temperature increases caused by higher moisture levels associated with larger silt and clay contents, or to different responses of the dominant plant species to temperature. In both soils, more than 55 % of SOC was associated with minerals, and its molecular composition indicated microbial decomposition. Our results suggested that long‐term warming in the High Arctic could induce the loss of SOC, particularly in the FLF; however, the response could vary with vegetation and/or soil properties, i.e. texture.

12867. 题目: Responses of soil inorganic and organic carbon stocks of alpine meadows to the disturbance by plateau pikas
文章编号: N19100107
期刊: European Journal of Soil Science
作者: Xiao Pan Pang, Qian Wang, Jing Zhang, Hai Peng Xu, Wen Na Zhang, Juan Wang, Zheng Gang Guo
更新时间: 2019-10-01
摘要: Small burrowing herbivores create extensive disturbances to grassland soil, which may change carbon cycling. We focused on the plateau pika (Ochotona curzoniae) to simultaneously investigate the responses of the soil organic carbon (SOC) and soil inorganic carbon (SIC) stocks of alpine meadows to the disturbance caused by this small burrowing herbivore and its disturbance intensity at the plot scale across five sites on the Qinghai‐Tibetan Plateau. The percentage of bare soil area in a disturbed plot was used as a proxy for the disturbance intensity of plateau pikas. Our study found that the disturbance by plateau pikas reduced the SIC stock and increased the SOC stock, whereas it had no effect on the soil total carbon (STC) stock. Our study also found that the SOC and STC stocks were higher at intermediate disturbance intensities of plateau pikas, whereas the SIC stock showed a decreasing trend as the disturbance intensity of plateau pikas increased. Our findings suggest that intermediate disturbance intensities of a small burrowing herbivore (plateau pika) improve soil quality by increasing the SOC stock and benefit soil carbon sequestration by increasing the STC stock.

12868. 题目: Non‐target screening of leaf litter derived dissolved organic matter using liquid chromatography coupled to high resolution mass spectrometry (LC‐QTOF‐MS)
文章编号: N19100106
期刊: European Journal of Soil Science
作者: O. Brock, R. Helmus, K. Kalbitz, B. Jansen
更新时间: 2019-10-01
摘要: Leaf litter derived dissolved organic matter (DOM) is an important source of organic matter entering the mineral soil, but characterization of leaf litter DOM is often not detailed enough to understand DOM dynamics and processes at the molecular level. (Ultra‐) High resolution techniques such as Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR‐MS), Orbitrap mass spectrometry and Quadrupole time‐of‐flight (QTOF) mass spectrometry have brought a new level of detail in (D)OM research by providing molecular formulae and information on molecular structures. We present a novel approach for leaf litter DOM characterization that includes non‐target screening using liquid chromatography (LC) coupled to high‐resolution QTOF‐MS. A method validation test showed that out of 26 spiked naturally occurring DOM molecules in a leaf litter DOM sample 23 were found back as features. After implementation of additional filtering to exclude certain combinations of heteroatoms (that are difficult to resolve even by the newest high resolution MS instruments), including molecular formulae with P atoms, 22 molecular formulae were correctly assigned. Although a large part of the annotated molecular formulae was unique for the respective litter sources, the molecular compound class distribution was similar for deciduous, coniferous and mixed leaf litter DOM. Most intense masses were detected in the 100–300 Da mass range, showing a bias of QTOF‐MS towards lower masses compared to FT‐ICR‐MS. The use of LC in combination with QTOF‐MS for leaf litter (D)OM characterization provides, together with Orbitrap‐MS, a more widely available and lower cost high resolution MS alternative to FT‐ICR‐MS. Novel approach to the characterization and analysis of leaf litter derived DOM. Non‐target screening using LC‐QTOF‐MS and the patRoon R package. Similar molecular compound class distribution for three leaf litter sources. High resolution DOM characterization alternative to FT‐ICR‐MS.

12869. 题目: Use of absorption optical indices to assess seasonal variability of dissolved organic matter in amazon floodplain lakes
文章编号: N19100105
期刊: Biogeosciences
作者: Maria Paula da Silva, Lino A. Sander de Carvalho, Evlyn Novo, Daniel S. F. Jorge, and Claudio C. F. Barbosa
更新时间: 2019-10-01
摘要: Given the importance of DOM in the carbon cycling of aquatic ecosystems, information on its seasonal variability is crucial. This study assesses the use of available absorption optical indices based on in situ data to both characterize the seasonal variability of the DOM dynamics in a highly complex environment and their viability of being used for satellite remote sensing on large scale studies. The study area comprises four lakes located at the Mamirauá Sustainable Development Reserve (MSDR). Samples for the determination of coloured dissolved organic matter (CDOM) and remote sensing reflectance (Rrs) were acquired in situ. The Rrs was applied to simulate MSI visible bands and used in the proposed models. Differences between lakes were tested regarding CDOM indices. Significant difference in the average of aCDOM (440), aCDOM spectra and S275–295 were found between lakes located inside the flood forest and those near the river bank. The proposed model showed that aCDOM can be used as proxy of S275–295 during rising water with good validation results, demonstrating the potential of Sentinel/MSI imagery data in large scale studies on the dynamics of DOM.

12870. 题目: Chemical behaviors and toxic effects of ametryn during the UV/chlorine process
文章编号: N19100104
期刊: Chemosphere
作者: Weiwei Yang, Yankui Tang, Lu Liu, Xiaoyu Peng, Yaxuan Zhong, Yunong Chen, Yinfeng Huang
更新时间: 2019-10-01
摘要: Ametryn (AMT), one of the most widely used herbicides in agriculture, has been frequently detected as a micropollutant in many aquatic environments. AMT residue not only pollutes water but also acts as a precursor for the production of disinfection by-products (DBPs). This study systematically investigated the fate of AMT during the UV/chlorine process. It was observed that the combination of UV irradiation and chlorination degraded AMT synergistically. The results of the radical quenching experiments suggested that AMT degradation by the UV/chlorine process involved the participation of UV photolysis, hydroxyl radical (OH) reactions, and reactive chlorine species (RCS) reactions, which accounted for 45.4%, 36.4%, and 14.5% of the degradation, respectively. Moreover, we found that Cl– 2 was an important reactive radical for AMT degradation. The chlorine dose, pH, coexisting anions (Cl and HCO3), and natural organic matter (NOM) were found to affect AMT degradation during the UV/chlorine process. Nineteen predominant intermediates/products of AMT degradation during UV/chlorine process were identified, including atrazine. Moreover, the corresponding transformation pathways were proposed, including electron transfer, bond cleavage (C–S, C–N), radical (OH, Cl and Cl– 2) reactions, and subsequent hydroxylation. The toxicity tests with Vibrio fischeri on AMT degradation suggested that more DBPs were generated by UV/chlorine-treated AMT, which possessed higher acute toxicity than AMT did. Although the UV/chlorine process evidently promoted the AMT degradation, optimization of process parameters may reduce the DBP production and merits further investigation.
图文摘要:

12871. 题目: Characteristics of organo-mineral complexes in contaminated soils with long-term biochar application
文章编号: N19100103
期刊: Journal of Hazardous Materials
作者: Guixiang Quan, Qinya Fan, Jianxiong Sun, Liqiang Cui, Hailong Wang, Bin Gao, Jinlong Yan
更新时间: 2019-10-01
摘要: Long-term studies on the environmental effects following biochar additions to soils, while plentiful, are predominantly focused on the soil fertility, whereas few are on the soil organo-mineral complexes. This study examines the changes of organo-mineral complexes in an acidic paddy soil and a saline-alkali soil which were remediated using biochar for approximately 8 years and 3 years, respectively. The results showed that loosely combined humus increased by 30.1% and 25.1% with the application of 40 t ha–1 biochar in the acidic paddy soil and the saline-alkali soil, respectively. Meanwhile, an increase of cement (Fe-oxides) was the contributor to the rise of the complexes content. Complex iron in the saline-alkali soil were 30% higher than in the acidic paddy soil with the application of 40 t ha–1 biochar. Fourier Transform Infrared Spectroscopy showed oxygen-containing functional groups on the surface of the biochar separated from the remediated field. X-ray diffraction analysis indicated that both complexation and sedimentation were involved in heavy metal immobilization. It was found that biochar amendment mitigated the effect of acid rain leaching and reduced vertical migration of the Fe/Al-bound complex, which can prevent soil from podzolization and thus improve its fertility.

12872. 题目: Influence of green manure and rice straw management on soil organic carbon, enzyme activities, and rice yield in red paddy soil
文章编号: N19100102
期刊: Soil and Tillage Research
作者: Tao Li, Jusheng Gao, Lingyu Bai, Yanan Wang, Jing Huang, Mahendar Kumar, Xibai Zeng
更新时间: 2019-10-01
摘要: Both the quantity and quality of organic amendments can influence the accumulation of soil organic carbon (SOC) and agroecosystem functioning. However, the evidences of the effect of combination of quantity and quality of organic amendments on the paddy soil quality and rice yield are scarce. An ongoing field experiment was conducted in Hunan province of China to investigate the effect of different Chinese milk vetch (Astragalus sinicus L.) and rice (Oryza sativa L.) straw management practices on the soil biochemical properties and rice yield. The experiment consisted six treatments: applying Chinese milk vetch (MV), applying early-season rice straw (S), applying early-season and late-season rice straw (DS), applying Chinese milk vetch and early-season rice straw (SMV), applying Chinese milk vetch, early-season and late-season rice straw (DSMV), and unamended organic amendment (CK). Compared with CK, SOC content was significantly increased by 13.0%, 18.5%, 11.1%, 12.3%, and 23.0% for the MV, S, DS, SMV, and DSMV treatments, respectively. No significant correlation was found between SOC content and yearly carbon inputs. Application of organic amendments increased soil hydrolase activities (β-D-cellobiosidase, β-1,4-glucosidase, β-1,4-xylosidase, β-1,4-N-acetyl-glucosaminidase and phosphatase). The geometric mean of the assayed hydrolases followed the order: S > DSMV > SMV > DS > MV > CK. Phenol oxidase was significantly higher in CK than in the applied organic amendment treatments. The lowest ratio of β-1,4-glucosidase: phenol oxidase occurred in the S treatment, suggesting that S treatment decreased microbial substrate use efficiency. The yearly average rice yield was increased by 18.6%, 8.5%, 12.3%, 14.6%, and 24.1% for MV, S, DS, SMV, and DSMV treatment with respect to CK. There was no significant correlation between SOC content and rice yield. In general, after 4-year cultivation, our results highlight the effect of quality of organic amendments on the chemical properties of SOC and its nutrient supply. Applying high quantities of diverse organic amendments is suggested to increase SOC content and rice yield in red paddy soil.

12873. 题目: Anion-exchange resin adsorption followed by electrolysis: A new disinfection approach to control halogenated disinfection byproducts in drinking water
文章编号: N19100101
期刊: Water Research
作者: Tong Yin, Yun Wu, Peng Shi, Aimin Li, Bin Xu, Wenhai Chu, Yang Pan
更新时间: 2019-10-01
摘要: Bromide and natural organic matter (NOM) are both precursors of halogenated disinfection byproducts (DBPs) in drinking water. During drinking water treatment process, chloride-form anion-exchange resin adsorption is expected to be capable of removing these DBP precursors and in the meantime releasing chloride ions. The released chloride as well as the chloride initially present in source water could be oxidized through electrolysis to generate free chlorine for disinfection. Based on the above assumptions, we developed a new disinfection approach using chloride-form anion-exchange resin adsorption followed by electrolysis to control halogenated DBPs. Parameter setup and optimization were performed for resin adsorption and electrolysis processes. Results showed that 93.7% of NOM and 90% of bromide could be removed at a resin dose of 20 mL per 2 L of simulated source water sample with a contact time of 1 h. Meanwhile, 49.5 mg/L of chloride was released from the resin to the water sample via anion-exchange, and the released chloride was further oxidized by electrolysis (Ti/RuO2–IrO2 anode and graphite cathode, current intensity of 0.4 A) to generate free chlorine (5 mg/L as Cl2) within 192 s. With this new approach, formation of total organic halogen, four trihalomethanes, and five haloacetic acids was reduced by 86.4%, 98.5%, and 93.2%, respectively, compared with chemical chlorination alone. Although the new approach might enhance the formation of some phenolic DBPs by decreasing bromide levels in source water, the overall cytotoxicity of the water samples treated with the new approach was significantly decreased by 68.8% according to a human hepatoma cell cytotoxicity assay. Notably, disinfection ability evaluation showed that the new approach achieved 3.36-log10 reductions of three seeded bacteria (Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus) in 19 s, suggesting that it was not only effective to E. coli but also effective to the chlorine-resistant bacteria (P. aeruginosa and S. aureus).
图文摘要:

12874. 题目: Char and tar formation during hydrothermal treatment of sewage sludge in subcritical and supercritical water: Effect of organic matter composition and experiments with model compounds
文章编号: N19093006
期刊: Journal of Cleaner Production
作者: Chenyu Wang, Yujie Fan, Ursel Hornung, Wei Zhu, Nicolaus Dahmen
更新时间: 2019-09-30
摘要: Hydrothermal treatment of sewage sludge is considered to be a promising environmentally friendly technology which can transform the organic matter in sludge into clean energy. However, the char and tar produced by side reactions will inhibit reaction. Five model compounds (humic acid, glutamic acid, glycerol, guaiacol, glucose) representing the main organic components (humus, proteins, lipids, lignin, and carbohydrates) in sewage sludge were treated in an autoclave at 300–400 °C for 30 min, the influence of the organic component on char/tar formation was studied. The char yield of humic acid was highest, up to 69.8(±3.1)%, followed by glucose. The tar yield of glycerol and guaiacol was highest in subcritical water and supercritical water, respectively. To further evaluate the utilization value of char/tar or to give a reasonable strategy for char/tar inhibition, the char/tar was characterized by elemental analysis, fourier transform infrared spectroscopy, thermosgravimetric analyzer, scanning electron microscope, and gas chromatography-mass spectrometer. The char/tar arising from the different model compounds exhibit differences in properties such as calorific value, thermal stability, and surface structure, which were due to the different pathways involved in their formation. The results provide the underlying insights needed to guide follow-up treatments or utilization of the char and tar produced during hydrothermal treatment of sewage sludge.

12875. 题目: Increasing hypoxia in the Changjiang Estuary during the last three decades deciphered from sedimentary redox-sensitive elements
文章编号: N19093005
期刊: Marine Geology
作者: Yijing Wu, Daidu Fan, Deli Wang, Ping Yin
更新时间: 2019-09-30
摘要: Ranked as one of the world's largest seasonal hypoxic water bodies (Dissolved oxygen, DO≤2 mg l−1), the Changjiang hypoxia has been reported to grow rapidly worse in recent decades according to cruise observations, but it has been seldom studied by sedimentary records. In this paper, four gravity cores (E1-E4), retrieved from the Changjiang Estuary, were dated by excess 210Pb and analyzed with grain-size compositions, total organic carbon (TOC) contents, and RSEs (redox sensitive elements) compositions. We aim to decipher RSEs enrichment characteristics and controlling mechanisms in the Changjiang Estuary. The results show that Mo and V enrichment is highly promoted by particle absorption and FeMn redox cycling at the shallow estuarine environment (E1 and E2) with occasional hypoxic disturbances. Scavenging of Mo and V by organic complexation becomes significant at the hypoxic center (E3), together with great influence by FeMn redox cycling, but they do not work effectively for U enrichment because of its easy remobilization and abundant riverine input. Moreover, upcore increasing trends of Mo, V, and U in E3 match well with a general lowering trend of bottom water DO minima since the mid-1980s. There are two progressive hypoxic development stages intercalated with a less DO-depleted period 1991–1997 as shown by both cruise observations and RSEs/Al records. These findings are vital to better understanding coastal hypoxic development and RSEs enrichment mechanisms in the seasonal hypoxic settings, because hypoxia is predicted to increase in the near future due to intensifying human disturbances.

12876. 题目: DOC fluorescence properties and degradation in the Changjiang River Network, China: implications for estimating in-stream DOC removal
文章编号: N19093004
期刊: Biogeochemistry
作者: Shucong Lv, Fang Wang, Weijin Yan, Yuchun Wang, Qibiao Yu, Yanqiang Li
更新时间: 2019-09-30
摘要: Dissolved organic carbon (DOC) in large river networks is an important carbon pool in the global biogeochemical cycle. DOC compositions vary spatially at global and regional scales, which influences DOC degradation and subsequent in-stream removal in river networks. The Changjiang River Network (CRN) is the third largest river system worldwide and plays an important role in DOC transformation and transportation. However, the relationships between DOC composition and degradation, as well as the quantification of in-stream removal, remain poorly understood. In this study, we chose the CRN to study spatial patterns of DOC fluorescence, as proxies for chemical composition, and degradation. Laboratory degradation experiments were conducted to explore DOC degradability and mechanisms of photodegradation and microbial respiration. We found that DOC fluorescence properties and degradation showed significant spatial differences in the lower reaches of the CRN. DOC with higher proportions of humic acid-like materials showed higher photodegradability. In degradation experiments, the total DOC loss was 49.1–66.0% over about the first 6 to 7 days. Microbial respiration removed 33.0–47.3% of total DOC, while photodegradation removed 9.0–35.3%. The relative contributions of photodegradation and microbial respiration to DOC degradation varied with different DOC fluorescence properties. The experimental values of DOC decay rate constants were 0.217–0.250 d−1. Our study improves understanding of DOC degradability, linking to its composition and providing a reference for estimating DOC in-stream removal in large river networks.

12877. 题目: Reviews and syntheses: Marine biogenic aerosols and the ecophysiology of coral reefs
文章编号: N19093003
期刊: Biogeosciences
作者: Rebecca Jackson, Albert Gabric, Roger Cropp, and Matthew Woodhouse
更新时间: 2019-09-30
摘要: Coral reefs are being threatened by global climate change, with ocean warming and acidification, compounded by declining water quality in many coastal systems, adversely affecting coral health and cover. This is of great concern as coral reefs provide numerous ecosystem, economic and social services. Corals are also recognized as being amongst the strongest individual sources of natural atmospheric sulfur, through stress-induced emissions of dimethylsulfide (DMS). In the clean marine boundary layer, biogenic sulfates contribute to new aerosol formation and the growth of existing particles, with important implications for the radiative balance. Evidence suggests that DMS is not only directly involved in the coral stress response, alleviating oxidative stress, but may create an ocean thermostat which suppresses sea surface temperature (SST) through changes to aerosol and cloud properties. This review provides a summary of the current major threats facing coral reefs and describes the role of dimethylated sulfur compounds in coral physiology and climate. The role of coral reefs as a source of climatically important compounds is an emerging topic of research however, the window of opportunity to understand the complex biogeophysical processes involved is closing with ongoing degradation of the world's coral reefs. The greatest uncertainty in our estimates of radiative forcing and climate change are derived from natural aerosol sources, such as marine DMS, which constitutes the largest flux of oceanic reduced sulfur to the atmosphere. Gaining a better understanding of the role of coral reef DMS emissions is crucial to predicting the future climate of our planet.

12878. 题目: Effect of Phosphorus-Modified Biochars on Immobilization of Cu (II), Cd (II), and As (V) in Paddy Soil
文章编号: N19093002
期刊: Journal of Hazardous Materials
作者: Han Zhang, Jingai Shao, Shihong Zhang, Xiong Zhang, Hanping Chen
更新时间: 2019-09-30
摘要: Novel phosphorus-modified biochars were produced by pyrolyzing biomass feedstocks (wood, bamboo, cornstalk and rice husk) pre-impregnated with potassium phosphate (K3PO4). The soil heavy metal immobilization performance and mechanisms of modified biochars were investigated. Incubation experiments showed that impregnation with phosphorous can decrease the extraction of Cu (II) and Cd (II) by 2 to 3 times. Phosphorus-modified biochars enhanced the transformation of Cu (II) and Cd (II) ions from acid soluble to more stable forms. Characterization results showed that phosphorus (P) compounds in modified biochar played a vital role to immobilize Cu (II) and Cd (II) by forming precipitates or complex es with them. Additionally, the modified rice husk and cornstalk biochars have in the average 14-24% and 19-33% higher immobilization efficiency for Cd (II) and Cu (II) than the other two P-assisted biochars. However, regardless of the feedstock, both the extraction and mobility of As (V) were increased by phosphorous. This study indicates that the P-modified biochar can serve as a novel remediation agent for heavy metal polluted soils.
图文摘要:

12879. 题目: Distribution and speciation of iron in Fe-modified biochars and its application in removal of As(V), As(III), Cr(VI), and Hg(II): An X-ray absorption study
文章编号: N19093001
期刊: Journal of Hazardous Materials
作者: Yu Feng, Peng Liu, Yanxin Wang, Yanhui Zou Finfrock, Xianjun Xie, Chunli Su, Na Liu, Yanyuan Yang, Yong Xu
更新时间: 2019-09-30
摘要: Characterization of the spatial distribution and speciation of iron (Fe) in Fe-modified biochars is critical for understanding the mechanisms of contaminant removal. Here, synchrotron-based techniques were applied to characterize the spatial distribution and speciation of Fe in biochars modified by FeCl3 or FeSO4 and pyrolyzed at 300, 600, and 900 °C, respectively. Confocal micro-X-ray fluorescence imaging (CMXRFI) results indicated Fe, sulfur (S), and chlorine (Cl) diffused into the basic porous structure of the biochars and aggregated to the surface as pyrolysis temperature increased. Fe K-edge X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectra revealed maghemite (γ-Fe2O3) as the primary Fe species in the modified biochars and Fe(0) was observed when pyrolyzed at 600 or 900 °C. Unmodified and FeCl3-modified biochars pyrolyzed at 900 °C were evaluated in the removal of arsenate (As(V)), arsenite (As(III)), hexavalent chromium (Cr(VI)) and Hg(II) from aqueous solution and Fe-modification enhanced the removal efficiency from 42.0%, 62.5%, 19.6%, and 97.0%, respectively, to all 99.9%. X-ray absorption spectroscopy results indicate both adsorption and redox reaction contributed to the removal mechanisms. The present study provides a prospective and sustainable material and offers information relevant to tailoring Fe-modified biochars to specific environmental applications.
图文摘要:

12880. 题目: A new strategy on biomining of low grade base-metal sulfide tailings
文章编号: N19092904
期刊: Bioresource Technology
作者: Xiaojian Liao, Shuiyu Sun, Siyu Zhou, Maoyou Ye, Jialin Liang, Jinjia Huang, Zhijie Guan, Shoupeng Li
更新时间: 2019-09-29
摘要: This study investigated the effect of designed microbial consortia on biomining of low grade base-metal sulfide tailings. The results show the amount of recycled metals were equal if the tailings were leached by mixed cultures of Leptospirillum ferriphilum and Acidithiobacillus thiooxidans at three different ratios or by pure culture of L. ferriphilum, which was better than the pure culture of Acidithiobacillus ferrooxidans. qPCR (quantitative polymerase chain reaction) demonstrated only L. ferriphilum functioned in the mixtures at initial stage. The results of extracellular polymeric substances (EPS) via three-dimensional excitation-emission matrix combined with parallel factor analysis (3DEEM-PARAFAC) collected from mixed or pure cultures indicated there were no interactions between two strains. Secondary minerals were formed, but did not influence the leaching process. A new strategy for tailings biomining was proposed: only ferrous oxidizers should be added during the initial and middle biomining stage, while sulfur oxidizers should be added at the end.

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