13821. 题目: Using δ15N and δ13C and nitrogen functionalities to support a fire origin for certain inertinite macerals in a No. 4 Seam Upper Witbank coal, South Africa
期刊: Organic Geochemistry
作者: Ofentse M. Moroeng, Nicola J. Wagner, Grant Hall, R. James Roberts
摘要: Fires are likely to have been central to the formation of certain inertinite macerals in South African coals. To investigate this hypothesis, a Permian, medium rank C bituminous Witbank coal (No. 4 Seam Upper) was density fractionated to yield an inertinite-rich and a vitrinite-rich sample, and assessed using stable nitrogen and carbon (δ15N and δ13C) isotopes in conjunction with nitrogen functionalities. The parent coal comprises of 41.6 vol% vitrinite and 48.5 vol% inertinite. The vitrinite-rich sample is dominated by collotelinite and collodetrinite (81 vol% vitrinite), and the inertinite-rich sample by fusinite, semifusinite, and inertodetrinite (63 vol% inertinite). The δ15N and δ13C values and nitrogen functionalities were used to constrain early coal formation pathways for the dominant macerals in the density fractionated samples. The vitrinite-rich sample has a lower δ13C relative to the inertinite-rich counterpart. However, the inertinite-rich sample has the lower δ15N value, along with a lower concentration of N-quaternary and higher N-pyrrolic compounds. Because these samples are of the same coal maturity, and the major macerals were derived from similar precursors, differences in δ15N and δ13C and nitrogen functionalities reflect differences in coal formation pathways. Degradation of 13C-rich cellulose in wood through either charring or bacterial activity leads to lower δ13C values. The lower 14N content for the vitrinite-rich sample along with higher N-quaternary and N-pyridinic suggests cellulose degradation driven by bacterial activity. In contrast, the higher 14N coupled with higher N-pyrrolic and N-oxide complexes for the inertinite-rich sample, suggests fusinite and semifusinite were formed through charring. Inertodetrinite is attributed to the disintegration of the charred matter.
13822. 题目: Impact of drill core contamination on compound-specific carbon and hydrogen isotopic signatures
期刊: Organic Geochemistry
作者: Richard Schinteie, Jesse R. Colangelo-Lillis, Janet M. Hope, Junhong Chen, Daniel B. Nelson, Amber J.M. Jarrett, Jochen J. Brocks
摘要: Compound-specific carbon and hydrogen isotope ratios are routinely measured on extractable organic matter to decipher biogeochemical processes and events in Earth history. To deliver accurate interpretations, it is paramount that isotopic values are derived from indigenous compounds and are not the result of contamination. However, distinguishing between compounds from these different provenances can be difficult, especially if a degree of mixing occurred. In this study, we assess the impact of hydrocarbon contamination on the carbon and hydrogen isotopic composition of n-alkanes from ∼820 Ma Precambrian evaporitic drill core samples through exterior/interior (E/I) rock extraction experiments. In these experiments, exterior and interior portions of the same rock samples were separately crushed to powder, extracted and processed. Compound-specific isotope values of n-alkanes from the different rock portions were subsequently measured and compared. In most cases, n-alkanes from exterior rock portions had consistently more depleted δ13C and δ2H values than their interior counterparts with an E/I isotopic offset averaging 0.2–3.9‰ for δ13C and 2–33‰ for δ2H. These diverging isotope patterns tend to correspond to E/I concentration differences of n-alkanes that are the result of contaminants overprinting on indigenous isotopic signals. Through the application of E/I experiments, the degree of isotopic overprinting can be investigated and mixed indigenous/contaminant signals identified.
13823. 题目: Abundances and light absorption properties of brown carbon emitted from residential coal combustion in China
期刊: Environmental Science & Technology
作者: Meiju Li, Xingjun Fan, Mengbo Zhu, Chunlin Zou, Jianzhong Song, Siye Wei, Wanglu Jia, Ping'an Peng
摘要: Brown carbon (BrC) fractions, including water-soluble organic carbon (WSOC), water-soluble humic-like substances (HULISw), alkaline soluble organic carbon (ASOC), and methanol soluble organic carbon (MSOC) were extracted from particles emitted from the residential combustion of coal with different geological maturities. The abundances and light absorption properties of these BrC fractions were comprehensively studied. The results showed that the abundances of the different constituents of the BrC fraction varied greatly with the extraction solvent, accounting for 4.3%–46%, 2.3%–23%, 3.2%–14%, and 76%–98% of the total carbon content in particles. The specific UV–vis absorbance (SUVA254) of BrC fractions followed the order of MSOC > ASOC > HULISw > WSOC. The WSOC and MSOC fractions from the combustion of low maturity coal had relatively low SUVA254 and high SR values. The mass absorption efficiencies (MAE365) for ASOC and MSOC were higher than for WSOC, and WSOC and MSOC from low maturity coal combustion had relatively low levels of light absorption. These findings indicated that coal combustion is a potential source of atmospheric BrC and the abundance and light absorption of the coal combustion-derived BrC fractions were strongly dependent on the extraction methods used and the coal maturity rather than the coal shapes.
13824. 题目: Investigation into Photo-induced Auto-oxidation of Polycyclic Aromatic Hydrocarbons Resulting in Brown Carbon Production
期刊: Environmental Science & Technology
作者: John Haynes, Keith E. Miller, Brian J Majestic
摘要: Brown carbon (BrC) is a collection of oxidized atmospheric aromatic compounds detected worldwide with broad functionality. This multifunctional nature allows BrC to be water-soluble and bioavailable and demonstrate light absorption at multiple wavelengths. Polycyclic aromatic hydrocarbons (PAH) are major primary products of combustion emissions and have long been known to oxidize in the environment as components of secondary organic aerosols. In this study, we have exposed aqueous PAH suspensions to simulated sunlight to investigate oxidized PAH as BrC precursors. Illuminated samples of naphthalene and anthracene demonstrated growth of several new products with absorptions and oxidation consistent with humic-like substances (HULIS). Reactions of aqueous naphthalene, anthracene, and their oxidized derivatives were found to produce chromatographic and spectroscopic evidence of HULIS formation when exposed to sunlight. The association of oxyradicals with HULIS has implications on human health via lung tissue damage; and its absorption character may add to radiative forcing processes in the atmosphere. The overall product characterizations from naphthalene and anthracene indicate reaction mechanism pathways that use oxidized alcohol and quinone as intermediate species.
13825. 题目: Formation, extracellular polymeric substances, and structural stability of aerobic granules enhanced by granular activated carbon
期刊: Environmental Science and Pollution Research
作者: Zixuan Liang, Qianqian Tu, Xiaoxuan Su, Xiangyu Yang, Junyu Chen, Yi Chen, Hong Li, Caihong Liu, Qiang He
摘要: Granular activated carbon (GAC) has been proved to accelerate the formation of aerobic granules during wastewater treatment. However, there has never been a study on the extracellular polymeric substances (EPS) or structural stability of the GAC aerobic granules. Thus, this study evaluated the impact of GAC on these characteristics. With GAC addition, granules matured 12 days earlier than those of the control group. Scanning electron microscopy showed the surface of aerobic granules enhanced by GAC to be denser and smoother than the surface of control granules, which could be the first line of defense against external selection pressure. After granules matured, there was no difference in contamination removal between the two types of granules. The protein content in EPS of GAC aerobic granules was higher than that of the control group; however, there was no difference in the polysaccharide content. EPS fluorescence in situ staining demonstrated that inside the aerobic granules, a high concentration of protein encapsulated the GAC. In addition, integrity coefficients indicated that GAC significantly improved the ability of aerobic granules to resist hydraulic shear. The result of hydrolase treatment proved that the outer layer structure of the GAC aerobic granules was maintained by β-polysaccharide, and the inner layer structure was maintained by protein. The ability of GAC-enhanced aerobic granules to resist single hydrolase was stronger than that of the control group.
13826. 题目: Lithium adsorptive properties of H2TiO3 adsorbent from shale gas produced water containing organic compounds
作者: Yunjai Jang, Eunhyea Chung
摘要: Shale gas produced water is a by-product from shale gas production which causes environmental issues and needs for a wastewater treatment process. Lithium is one of the valuable metals that exists in the shale gas produced water, and it can be recovered during the water treatment process. However, the concentration of organic carbon in the produced water is significantly high, and these organic compounds may affect the lithium recovery efficiency. Therefore, the lithium adsorption from shale gas produced water containing organic compounds was carried out in this study to observe the influence of organic compounds on lithium adsorption using H2TiO3 adsorbent. The equilibrium time from the kinetic study and the maximum adsorption capacity calculated from the Langmuir isotherm equation decreased with the addition of organic compounds to the produced water. Overall, lithium was selectively recovered from the pH buffered shale gas produced water with or without organic compounds. However, the results indicate the addition of organic compounds, especially the smaller-molecular-weight organic compound, to the produced water inhibits the lithium adsorption significantly.
13827. 题目: Effects of natural dissolved organic matter on the complexation and biodegradation of 17α-ethinylestradiol in freshwater lakes
期刊: Environmental Pollution
作者: Leilei Bai, Qi Zhang, Changhui Wang, Xiaolong Yao, Hui Zhang, Helong Jiang
摘要: Natural dissolved organic matter (DOM) produced in algal blooms and overgrowths of macrophyte changes the elimination and ecotoxicity of estrogens in freshwater lakes. The complexation of 17α-ethinylestradiol (EE2) and various DOMs, including the water- and sediment-derived DOMs from the algal-dominant zone in Lake Taihu (TW and TS, respectively) and the macrophyte-dominant zone in Poyang Lake (PW and PS, respectively), and the humic acid (HA), was investigated along with the subsequent effects on EE2 biodegradation. Dialysis equilibrium experiments showed that binding to DOM significantly decreased the freely soluble concentrations of EE2. The binding capacity of the five DOMs followed the order of PW < TW < PS ≈ TS < HA. A negative correlation was found between the organic-carbon-normalized sorption coefficient (logKDOC) and the absorption ratio (E2/E3) of DOM, indicating that the large sized, aromatic molecules were involved in the complexation. The reduced freely soluble concentrations of EE2 did not inhibit its biodegradation by an EE2-degrading strain, Rhodobacter blasticus. Conversely, the autochthonous-dominated water-derived DOMs stimulated a more extensive biodegradation of EE2 than the sediment-derived DOMs, and the existence of HA resulted in the smallest increase in EE2 biodegradation. The promoting effect was associated with the increased concentration, activity, and transforming rate of R. blasticus by the bioavailable components in DOM. The present study suggests that the significant impact of natural DOM should be fully considered when assessing the fate and ecological risks of estrogens in eutrophic waters.
13828. 题目: Fluorescence spectroscopic characterisation of algal organic matter: towards improved in-situ fluorometer development
期刊: Environmental Science: Water Research & Technology
作者: Sara Imran Khan, Narasinga Rao Hanumanth Rao, Arash Zamyadi, Xiang Li, Richard Stuetz, Rita Henderson
摘要: Online fluorescence probes have been applied for the rapid detection of cyanobacterial and algal cells via measurement of fluorescent cell pigmentation with some success; however, this alone is not a sufficiently robust method to identify specific species, stage of the bloom, or measure the released organic matter. This study investigates whether fluorescence can be applied to characterise the AOM released by cyanobacterial and algal species which, when combined with cell pigmentation measurements, may improve the specificity and robustness of these online methods. The AOM released by key cyanobacterial (Dolichospermum circinalis, Cylindrospermopsis raciborskii, four strains of Microcystis aeruginosa) and algal (Chlorella vulgaris) species were studied at lab scale throughout their growth using 3D-fluorescent excitation-emission matrix (F-EEMs) spectroscopy combined with Parallel Factor analysis (PARAFAC). A six-component PARAFAC model was developed for the analysed dataset. Analysis of the PARAFAC data indicated that observations of certain wavelengths could be helpful for AOM monitoring in conjunction with cell pigments, giving information on both, bloom health and AOM character. The relevant wavelengths were shown to vary depending on the species; for example, the fluorescence of amino acid-like material at λex/em =290/345 nm dominated in the AOM originating from C. vulgaris, while that of M. aeruginosa (CS-555) was dominated by fluorescence at λex/em =355/475 nm which has previously been associated only with terrestrially delivered substances. Both these fluorescence signatures had significant correlations with the released AOM, measured as dissolved organic carbon (DOC), and dominated across the exponential and stationary phases relative to other PARAFAC components. With fluorescence probes on the market that measure fluorescence in AOM regions, there is an opportunity to monitor these key peaks simultaneously with pigment fluorescence to give further information on the released organic matter character and its treatability.
13829. 题目: Emerging investigator series: Photocatalysis for MBR Effluent Post-Treatment: Assessing the Effects of Effluent Organic Matter Characteristics
期刊: Environmental Science: Water Research & Technology
作者: Mostafa Maghsoodi, Céline Jacquin, Benoit Teychené, Marc Heran, Volodymyr Tarabara, Geoffroy Lesage, Samuel Snow
摘要: Dissolved organic matter (DOM) poses a serious challenge to applied photocatalysis. Membranes may offer a promising synergistic opportunity to enable efficient photocatalysts in the presence of DOM. Membrane bioreactor (MBR) effluent from a municipal treatment plant was studied to elucidate the effects of filtration and organic matter composition on photocatalysis. Effluent samples were collected from MBR units during routine operation and before/after chemical cleaning. Additional DOM samples from the bulk supernatant were separated into colloidal, hydrophobic and transphilic fractions, providing a novel examination of the inhibition potential of DOM. These DOM fractions and the effluent organic matter (EfOM) samples were then characterized utilizing three-dimensional excitation–emission matrix (3DEEM) fluorescence spectroscopy and assayed for their potential to inhibit TiO2-mediated photocatalytic degradation of a probe compound, para-chlorobenzoic acid (pCBA). The colloidal fraction of DOM was found to exert the strongest inhibition, followed by the transphilic, then the hydrophobic fractions; at 5 mgC/L, these fractions reduced the photodegradation rates by approximately 75%, 27%, and 17%, respectively. Of the effluent samples, EfOM from the recently-cleaned membrane caused the greatest inhibition of photocatalysis (~100% reduction at 0.5 to 2.0 mgC/L), whereas the effluent from the fouled membrane provided the least inhibition (~33% reduction at 2.0 mgC/L). The 3DEEM analysis predicted inhibitory action of both DOM and EfOM, based on total fluorescence volumes. Results here demonstrate the prospective utility of combining membrane technologies with photocatalytic processes.
13830. 题目: A holistic analysis of ANAMMOX process in response to salinity: from adaptation to collapse
期刊: Separation and Purification Technology
作者: Lu Huifeng, Li Yiyu, Shan Xiaoyu, Ghulam Abbas, Zeng Zhuo, Kang Da, Wang Yayi, Zheng Ping, Zhang Meng
摘要: The application of anaerobic ammonium oxidation (ANAMMOX) process to industrial wastewater treatment usually faces the challenge of high salinity. However, most of the current ANAMMOX sludge was enriched from low-salinity water, resulting in the critical gap between the inoculum and saline wastewater. In this work, an ANAMMOX reactor fed with inoculum enriched from low-salinity water successfully adapted to saline wastewater (500 mmol/L NaCl, 2.92%) after a long-term stepwise acclimatization. The nitrogen removal rate and total nitrogen removal efficiency reached 9.72 kg·m-3·d-1 and 80.90%, respectively. However, further salinity increase to 600 mmol/L caused a collapse of reactor performance. The inorganic matters’ proportion improved along with the salinity increase, which might be attributed to the compact particles observed in the microstructure of ANAMMOX sludge. A microbial community succession occurred in response to the salinity increase. When the salinity increased to 160 mmol/L, the dominant functional bacteria shifted from Candidatus Kuenenia to unclassified Brocadiaceae, which was supposed to be salt-tolerant. The up and down regulations of polysaccharides and ζ potential in EPS were positive strategies for salinity adaptation of ANAMMOX bacteria. However, the barrier of seawater salinity (3-5%) could not be overcome. The present work would provide holistic view for the enrichment of salt-tolerant AnAOB and help in the selection of seeding sludge for the treatment of saline wastewater by ANAMMOX process.
13831. 题目: Synergistic effects of surfactant-assisted biodegradation of wheat straw and production of polysaccharides by Inonotus obliquus under submerged fermentation
期刊: Bioresource Technology
作者: Xiangqun Xu, Pan Wu, Tianzhen Wang, Lulu Yan, Mengmeng Lin, Cui Chen
摘要: Current work proposes an innovative wheat straw biomass utilization strategy that connects efficient lignocellulose biodegradation with exo-polysaccharide (EPS) production in I. obliquus under submerged fermentation. The addition of Tween 80 increased the activities of ligninolytic enzymes MnP, LiP and Lac by 1200%, 125% and 39.9%, respectively. When wheat straw lignin recalcitrance was substantially reduced with the aid of Tween 80, I. obliquus was capable of utilizing the substrates and in turn accumulated EPS. The degradation of cellulose, hemicellulose and lignin reached 46.1%, 46.4% and 44.1% on Day 9 of growth, respectively. Meanwhile, the maximum mycelial biomass and EPS production increased by 23.3% and 142.9%, respectively. The EPS had higher contents of sugar, protein, uronic acid, and mannose ratio, and higher antioxidant activity against 2, 2 - diphenyl - 1 - picrylhydrazyl (DPPH), 2, 2 - azinobis - (3 - ethylbenzothiazoline - 6 - sulfonic acid) (ABTS•+) and hydroxyl radicals.
13832. 题目: Investigating the impact of anthropogenic land use on a hemiboreal lake ecosystem using carbon/nitrogen ratios and coupled-optical emission spectroscopy
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: N. Stivrins, M. Liiv, A. Brown, R.Y. Banerjea, A. Heinsalu, S. Veski
摘要: Anthropogenic impacts on lake ecosystems have increased substantially towards the present. However, the strength and timing in most cases are not evaluated in detail, missing valuable information on the response and recovery of an aquatic system. In this study, we use the sediment total organic carbon/total nitrogen ratio (C/N) and inductively coupled-optical emission spectroscopy (ICP-OES) elements and the available information about the biological processes to explore anthropogenic land use impact on the lake ecosystem. As a case study we selected a hemiboreal lake Trikātas (Latvia, NE Europe). The Pearson correlation was used to statistically test the correlations of all variables. Our results show that the C/N ratio lowered immediately with the onset of crop cultivation at 500 BCE. Extensive forest clearance and an abrupt increase in land use are reflected through the associated chemical elements from ICP-OES and the increasing presence of herbivore dung spores since 1200 CE. These changes concur with the excess of fish remains suggesting a decrease in fish populations. Interestingly, anthropogenic land use driven erosion and accompanied calcium carbonate (CaCO3) matter influx favoured the abundance of Chara spp. in Lake Trikātas since 500 CE, which currently forms the protected specific habitat-type (H3140) of the European Union. At present, specific submerged macrophyte Chara habitat-type diminished almost entirely due to increased nutrient input, phytoplankton blooming, hypertrophic conditions and reduced light availability. The continued land use practices led to a switch in organic matter source in the lake from macrophytes to solely algal origin. The current study underlines the need of additional methods used to detect the sensitivity of lake ecosystem to external disturbances such as minor anthropogenic land use that might not necessarily be apparent in more traditional analyses such as palynology.
13833. 题目: Carbon outwelling and emissions from two contrasting mangrove creeks during the monsoon storm season in Palau, Micronesia
期刊: Estuarine, Coastal and Shelf Science
作者: Mitchell Call, Christian J. Sanders, Paul A. Macklin, Isaac R. Santos, Damien T. Maher
摘要: Mangroves sequester large amounts of carbon in soils but limited information is available on carbon losses from tropical mangrove systems. Here we quantify carbon outwelling, CO2 emissions and pore-water exchange rates from two nearby (∼2 km apart) tropical mangrove creeks located in different geomorphic settings on the island of Palau, Micronesia during the monsoonal storm season. On average, POC and pCO2 were >100% higher and DOC, DIC and TA were 62%, 25%, 16% higher, respectively, from Creek 1 (located within a semi-enclosed bay) than from Creek 2 (located along the coast adjacent to fringing reefs). Both creeks were net exporters of DIC, DOC, POC and emitters of CO2. However, outwelling rates of POC, DIC and DOC and CO2 emissions were 27-fold, 8-fold, 4-fold and 3-fold higher at Creek 1. DIC outwelling (37%) and CO2 emissions (39%) were the major terms contributing to total carbon losses at Creek 1, whilst CO2 emission (61%) was the major contributor at Creek 2. Monsoon storms appeared to explain the organic carbon dynamics whilst tidal pumping appears to drive the inorganic carbon dynamics at both creeks. Our data demonstrates the considerable heterogeneity of mangroves creeks that are in close proximity and subject to similar weather conditions but in differing geomorphological settings.
13834. 题目: The effects of humic water on endothelial cells under hyperglycemic conditions: inflammation-associated parameters
期刊: Environmental Geochemistry and Health
作者: Katarzyna Szot, Krzysztof Góralczyk, Małgorzata Michalska, Natallia Veryho, Jacek Chojnowski, Irena Ponikowska, Danuta Rość
摘要: Humic waters (HW) are globally unique, deep underground, dark-brown waters containing humic acids, and they present numerous therapeutic activities including anti-inflammatory. In the present study, we use HW from source in Poland. Diabetes has become an epidemic and is a risk factor of cardiovascular diseases. Hyperglycemia in diabetes is responsible for damaging of the endothelium and increases inflammation on the surface of the vascular lining. The inflammatory process in diabetes is associated with the secretion of inflammatory cytokines by endothelial cells, e.g., tumor necrosis factor alpha (TNFα) and interleukin 6 (IL-6), and with the reduction of cell proliferation. In the study, we used cultures of endothelial cells (HUVEC line—human umbilical vein endothelial cells) with the addition 30 mM/L of glucose in the culture medium which imitated the conditions of uncontrolled diabetes. The addition of HW in the proper volume to the culture medium causes reduction of inflammation by significant decrease in inflammatory cytokines such as TNFα and IL-6 and also leads to enhancement of the cell proliferation. It appears that the adverse effects of hyperglycemia on vascular endothelial cells may be corrected by addition of humic water. The above promising results of in vitro tests provide an opportunity to the possible use of humic water in the supportive treatment of endothelial dysfunction disorders in diabetes. However, this issue requires further clinical research.
13835. 题目: Quantifying degradative loss of terrigenous organic carbon in surface sediments across the Laptev and East Siberian Sea
期刊: Global Biogeochemical Cycles
作者: Lisa Bröder, August Andersson, Tommaso Tesi, Igor Semiletov, Örjan Gustafsson
摘要: Ongoing permafrost thaw in the Arctic may remobilize large amounts of old organic matter. Upon transport to the Siberian shelf seas, this material may be degraded and released to the atmosphere, exported off‐shelf or buried in the sediments. While our understanding of the fate of permafrost‐derived organic matter in shelf waters is improving, poor constraints remain regarding degradation in sediments. Here, we use an extensive dataset of organic carbon concentrations and isotopes (n=109) to inventory terrigenous organic carbon (terrOC) in surficial sediments of the Laptev and East Siberian Seas (LS+ESS). About 55 % of these ~2.7 Tg terrOC appear resistant to degradation on a millennial timescale. A first‐order degradation rate constant of 1.5 kyr‐1 is derived by combining a previously established relationship between water depth and cross‐shelf sediment‐terrOC transport time with mineral‐associated terrOC loadings. This yields a terrOC degradation flux of ~1.7 Gg yr‐1 from surficial sediments during cross‐shelf transport, which is orders of magnitude lower than earlier estimates for degradation fluxes of dissolved and particulate terrOC in the water column of the LS+ESS. The difference is mainly due to the low degradation rate constant of sedimentary terrOC, likely caused by a combination of factors: (i) the lower availability of oxygen in the sediments compared to fully oxygenated waters, (ii) the stabilizing role of terrOC‐mineral associations and (iii) the higher proportion of material that is intrinsically recalcitrant due to its chemical/molecular structure in sediments. Sequestration of permafrost‐released terrOC in shelf sediments may thereby attenuate the otherwise expected permafrost carbon‐climate feedback.
13836. 题目: Dissolved organic matter chemistry and transport along an Arctic tundra hillslope
期刊: Global Biogeochemical Cycles
作者: Laurel M. Lynch, Megan B. Machmuller, Claudia M. Boot, Timothy P. Covino, Christopher D. Rithner, M. Francesca Cotrufo, David W. Hoyt, Matthew D. Wallenstein
摘要: Permafrost thaw is projected to restructure the connectivity of surface and subsurface flowpaths, influencing export dynamics of dissolved organic matter (DOM) through Arctic watersheds. Resulting shifts in flowpath exchange between both soil horizons (organic‐mineral) and landscape positions (hillslope‐riparian) could alter DOM mobility and molecular‐level patterns in chemical composition. Using conservative tracers, we found relatively rapid lateral flows occurred across a headwater Arctic tundra hillslope, as well as along the mineral‐permafrost interface. While pore waters collected from the organic horizon were associated with plant‐derived molecules, those collected from permafrost‐influenced mineral horizons had a microbial origin, as determined by fluorescence spectroscopy. Using high‐resolution NMR spectroscopy, we found that riparian DOM had greater structural diversity than hillslope DOM, suggesting riparian soils could supply a diverse array of compounds to surface waters if terrestrial‐aquatic connectivity increases with warming. In combination, these results suggest integrating DOM mobilization with its chemical and spatial heterogeneity can help predict how permafrost loss will structure ecosystem metabolism and carbon‐climate feedbacks in Arctic catchments with similar topographic features.
13837. 题目: Detection of transient denitrification during a high organic matter event in the Black Sea
期刊: Global Biogeochemical Cycles
作者: Clara A. Fuchsman, Barbara Paul, James T. Staley, Evgeniy V. Yakushev, James W. Murray
摘要: N2 production by denitrification can occur in anoxic water or potentially inside organic particles. Here we compare data from the Black Sea, a permanently anoxic basin, during two organic matter regimes: suspended particulate organic matter concentrations were high in the oxycline after the spring bloom in March 2005 compared to lower organic matter concentrations in June 2005, May and October 2007, July 2008 and May 2001. For all cruises, N2 gas had a maximum in the suboxic zone [O2 <10 μmol L‐1]. During the high organic matter event [March 2005], an additional shallower N2 gas and δ15N‐N2 maxima occurred above the suboxic zone in the oxycline where oxygen concentrations were 30‐50 μmol L‐1. Examination of 16S rRNA indicated that anammox bacteria were not present in the oxycline. The δ15N of biologically produced N2 in the oxycline in March 2005 was significantly enriched (+7 to +38‰), not depleted, as would be expected from water column fractionation. A simple diffusion calculation indicated that ammonium produced from remineralization inside particles could be oxidized to nitrate and then completely consumed by denitrification inside the particle. In this calculation, half of denitrified N atoms originated from organic N [δ15N = 11‰] and half of N atoms originated from ambient nitrate [δ15N = 5‐7‰], producing enriched δ15N‐N2 values. We suggest that denitrifiers were active in microzones inside particulates in hypoxic waters above the suboxic zone of the Black Sea. Denitrification in particles may also explain previous data from the oxycline above ocean oxygen deficient zones.
13838. 题目: Impacts of wise grazing on physicochemical and biological features of soil in a sandy grassland on the Tibetan Plateau
期刊: Land Degradation & Development
作者: Nan Nan Zhang, Geng Sun, Bo Zhong, En Tao Wang, Chun Zhang Zhao, Yan Jie Wang, Wei Cheng, Ning Wu
摘要: Desertification is a serious environmental problem on the Tibetan Plateau and various strategies, such as long‐term fencing and grazing management, have been implemented in that region to control the soil degradation. However, little is known about the role of interactions among the soil aggregate, microbial communities, and nutrient traits in the soil restoration. In this study, we compared the effects of different restoration strategies on the formation of aggregates, the amount and distribution of soil nutrients, as well as the abundance and diversity of bacteria in a sandy soil of grassland at the Tibetan Plateau. The results demonstrated that both the grazing exclusion (GE: artificial planting and nutrient addition) and wise grazing (WG: artificial planting and nutrient addition with controlled grazing) treatments significantly increased the proportion of macroaggregates (4.0 and 5.2 times, P < 0.05) compared with the control. Increased soil organic carbon (SOC), total carbon (TC), total nitrogen (TN), and total phosphorus (TP) were found in the aggregates of WG treatment, but not in the GE samples. In addition, WG significantly changed the bacterial composition and increased bacterial abundance in soil. This study evaluated WG as an efficient management for restoration of degraded sandy grassland in the Tibetan Plateau since it significantly enriched the soil nutrients, improved the soil structure and increased bacterial abundance. This is the first study to relate the aggregates with nutrient accumulation and bacterial community during the soil restoration in the Tibetan Plateau.
13839. 题目: The effect of redox capacity of humic acids on hexachlorobenzene dechlorination during the anaerobic digestion process
期刊: Environmental Science and Pollution Research
作者: Dongyang Li, Beidou Xi, Yingjun Li, Xiaowei Wang, Tianxue Yang, Hong Yu, Caihong Huang, Jianchao Zhu, Qi Li, Xing Peng, Zhifei Ma
摘要: Hexachlorobenzene (HCB) dechlorination affected by humic acids (HA) was evaluated in terms of HA redox capacity, HA concentrations, and microbial community, as well as the correlation between HA redox capacity values and HCB concentrations. With addition of HA in the initial stage, redox capacity values increased by 2.19 meq/L (80 mg/L of HA addition, HA80), 2.51 meq/L (120 mg/L of HA addition, HA120), and 3.64 meq/L (200 mg/L of HA addition, HA200), respectively. The addition of HA could prominently enhance the HCB degradation rate. However, the concentration and the redox capacity of HA decreased during the anaerobic digestion process. Illumina MiSeq sequencing showed that microbial community affected by HA. Bacillus, Comamonas, and Pseudomonas were the predominant genera during the HCB dechlorination treatment. Moreover, Bacillus and Pseudomonas can improve HA electron transfer capability and promote the dechlorination of HCB.
13840. 题目: Non-additive responses of soil C and N to rice straw and hairy vetch ( Vicia villosa Roth L. ) mixtures in a paddy soil
期刊: Plant and Soil
作者: Guopeng Zhou, Weidong Cao, Jinshun Bai, Changxu Xu, Naohua Zeng, Songjuan Gao, Robert M. Rees
摘要: Aims: We studied the effects of mixing rice straw and hairy vetch plant residues in a subtropical paddy soil, on subsequent carbon (C) and nitrogen (N) dynamics. Methods: Using a theoretical framework, we designed two groups of experiments (involving equal amounts of residual C or N addition, referred to as either C or N treatments). Each experiment included mixed residues of rice straw and hairy vetch at different mixing ratios. Soils together with residues were incubated at 25 °C under waterlogged conditions for 100 days. Greenhouse gas (GHG) emissions and soil C and N fractions were measured continuously. Results: Both C and N treatments affected soil C and N dynamics, and these dynamics were quantitatively dependent on residue C/N ratios. The effect of residue mixtures on C and N dynamics could not be predicted from single residues, since there were non-additive effects of residue mixtures. Synergistic effects were generally more frequent than antagonistic effects. Residue mixtures tended to enhance CO2 and CH4 emissions in both C and N treatments but decreased N2O emissions in the N treatment. In the N treatment, dissolved organic C (DOC), dissolved organic N (DON), and microbial biomass C (MBC) concentrations increased. DOC and DON concentrations decreased in the C treatment. Residue mixtures enhanced the global warming potentials (GWP) of greenhouse gases (GHG) emitted from soil by non-additive synergistic effects. The C/N ratio of residue mixtures affected the non-additive responses of soil C and N dynamics, for example mixtures with a C/N ratio of 25 had higher CO2 emissions and DOC concentrations than those with a C/N ratio of 35 as a consequence of non-additive effects, however, CH4 emissions and MBC concentrations were higher in mixtures with a C/N ratio of 35 than in mixtures with a C/N ration of 25. Conclusions: These results indicated that non-additive effects can impact soil C and N dynamics and that residue C/N ratios play an important role in influencing non-additive effects. Applying a single residue to paddy soils may be better than residue mixtures from a GWP mitigation perspective.