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28581. 题目: Multiple negative carbon-isotope excursions during the Carnian Pluvial Episode (Late Triassic)
文章编号: N18071301
期刊: Earth-Science Reviews
作者: Jacopo Dal Corso, Piero Gianolla, Manuel Rigo, Marco Franceschi, Guido Roghi, Paolo Mietto, Stefano Manfrin, Béla Raucsik, Tamás Budai, Hugh C. Jenkyns, Claire E. Reymond, Marcello Caggiati, Giovanni Gattolin, Anna Breda, Agostino Merico, Nereo Preto
更新时间: 2018-07-13
摘要: The Carnian Pluvial Episode was a phase of global climatic change and biotic turnover that occurred during the early Late Triassic. In marine sedimentary basins, the arrival of huge amounts of siliciclastic sediments, the establishment of anoxic conditions, and a sudden change of the carbonate factory on platforms marked the Carnian Pluvial Episode. The sedimentary changes are closely associated with abrupt biological turnover among marine and terrestrial groups as, for example, an extinction among ammonoids and conodonts in the ocean, and a turnover of the vertebrate fauna and the flora on land. Multiple negative carbon-isotope excursions were recorded during the Carnian Pluvial Episode in both organic matter and marine carbonates suggesting repeated injection of 13C-depleted CO2 into the ocean–atmosphere system, but their temporal and causal links with the sedimentological and palaeontological changes are poorly understood. We here review the existing carbon-isotope records and present new data on the carbon-isotope composition of organic carbon in selected sections of the western Tethys realm that record the entire Carnian Pluvial Episode. New ammonoid, conodont and sporomorph biostratigraphic data were collected and coupled to an extensive review of the existing biostratigraphy to constrain the age of the sampled sections. The results provide biostratigraphically constrained composite organic carbon-isotope curves for the Carnian. This sheds light on the temporal and causal links between the main carbon-isotope perturbations, and the distinct environmental and biotic changes that mark the Carnian Pluvial Episode. The carbon-isotope records suggest that a series of carbon-cycle perturbations, possibly recording multiple phases of volcanic activity during the emplacement of the Wrangellia Large Igneous Province, disrupted Carnian environments and ecosystems repeatedly over a remarkably long time interval of about 1 million years.

28582. 题目: Insights into the succession of the bacterial microbiota during biodrying of storage sludge mixed with beer lees: Studies on its biodiversity, structure, associations, and functionality
文章编号: N18071216
期刊: Science of The Total Environment
作者: Tiantian Liu, Chongwei Cui, Junguo He, Jian Tang
更新时间: 2018-07-12
摘要: Biodrying was first used for post-treatment of storage sludge mixed with beer lees. In this study, dynamic changes in dissolved organic matter (DOM), bacterial community structure, bacterial associations as well as metabolic functions were investigated using Excitation-Emission Matrix (EEM) spectra, high-throughput sequencing, network and correlation matrix analyses, and Phylogenetic Investigation of Communities by Reconstruction of Unobserved States (PICRUSt). Furthermore, a hypothetical model was proposed to better understand the biodrying process. The results showed that desired performance was obtained and DOM variations revealed that biodrying can increase biostability of the matrix. The bacterial communities differed among different stages of the biodrying. At the phylum level, the dominant phyla were Proteobacteria and Bacteroidetes in the mesophilic and cooling phases, whereas Firmicutes became the most dominant phylum in the thermophilic phase. At the genus level, the dominant bacteria in the mesophilic and cooling phases were not obvious, while Ureibacillus and Bacillus were the dominant genera in the thermophilic phase. Network and correlation matrix analyses were useful tools for insights into the bacterial interactions. PICRUSt metagenome inference indicated that metabolism, genetic information processing, and environmental information processing were the primary metabolic pathways. These results allowed us to advance a hypothetical model explaining how succession in bacterial associations regulates the dynamics of a biodrying system.

28583. 题目: Microscale water distribution and its effects on organic carbon decomposition in unsaturated soils
文章编号: N18071215
期刊: Science of The Total Environment
作者: Zhifeng Yan, Tiejun Wang, Lichun Wang, Xiaofan Yang, Peyton Smith, Markus Hilpert, Siliang Li, Jianying Shang, Vanessa Bailey, Chongxuan Liu
更新时间: 2018-07-12
摘要: Microscale water distribution in the subsurface is key to many geochemical and biogeochemical reactions. This study investigated microscale water distribution and movement in unsaturated soils using micro-continuum hydrodynamic models, and examined the effect of microscale water distribution on organic carbon (C) decomposition using a micro-continuum biogeochemical reaction model. The micro-continuum hydrodynamic model that relates capillary pressure to porosity captured the measured water imbibition curve at the core scale, and exhibited reasonable water distribution and movement at the microscale. The simulations of organic C decomposition illustrate that microscale water distribution strongly affected the distribution of C decomposition rates by regulating the availability of dissolved organic C and oxygen. Particularly, changes in water distribution altered the location and intensity of reactive hotspots and thereby CO2 flux from soils. The microscale interactions between water content and organic C decomposition rate provide underlying mechanisms for explaining macroscale phenomenon observed in laboratory and fields. Overall, this study presents a useful tool for explicating hydro-biogeochemical behaviors in the subsurface by integrating micro-continuum hydrodynamic and biogeochemical reaction modeling.

28584. 题目: Realizing the opportunities of black carbon in urban soils: Implications for water quality management with green infrastructure
文章编号: N18071214
期刊: Science of The Total Environment
作者: L.A. Schifman, A. Prues, K. Gilkey, W.D. Shuster
更新时间: 2018-07-12
摘要: Soils and associated microbial processes regulate the carbon cycle and provide a sink for atmospheric black carbon (BC). Particularly in urban areas, present and accumulated soil BC may act as an effective sorbent of anthropogenic contaminants in green spaces. We characterized carbon concentrations that have accumulated in urban soils (organic carbon, BC, and inorganic C) and determined soil physical attributes (soil texture, hydraulic conductivity) from urban soil assessments (surface and sub-surface horizons) carried out in eleven cities in the United States. We used both ordinary least squares and non-parametric classification and regression tree (CART) methods to discern trends in soil BC concentrations with regard to soil, landscape, and emission characteristics. We found that for all cities, regional traffic density and vegetation were good predictors of soil BC concentration. Additionally, the thickness of the top soil horizon explained additional variation in sub-surface BC concentrations. Sites with coincident BC stocks and favorable infiltration rate were discussed as per their potential for improving water quality in multifunctional green infrastructure installations. In the broader sense, the high sorption capacity of existing, accumulated soil BC can contribute to regulation of contaminant cycling in urban areas and may enhance the overall value of urban soils in terms of ecosystem services.

28585. 题目: Changing rainfall frequency affects soil organic carbon concentrations by altering non-labile soil organic carbon concentrations in a tropical monsoon forest
文章编号: N18071213
期刊: Science of The Total Environment
作者: Xiaomei Chen, Qi Deng, Guojun Lin, Meizhen Lin, Hui Wei
更新时间: 2018-07-12
摘要: Soil stores a substantial proportion of carbon (C), making it the greatest terrestrial C pool and pivotal to stabilizing the global climate system. Rainfall amounts and regimes have been changing in many places, but effects of precipitation changes on soil organic C (SOC) stabilization are not completely understood. Considerable attention has been focused on the consequences of changes in rainfall amounts, with rainfall regimes having been less studied. This study was conducted in a tropical climax forest to clarify the effects of rainfall changes on SOC fractions, with permanganate oxidation and density fractionations employed to divide the labile and non-labile SOC fractions. Two rainfall manipulation treatments, i.e., increased rainfall frequency with the total rainfall amount unchanged (IRF) and decreased rainfall amount by 50% with rainfall frequency unaltered (DRA), were conducted for two years, with ambient rainfall (AR) as the control. As a result, the IRF treatment increased the SOC concentration that mainly originated from increases in the non-labile SOC content. Relative to the AR control, the DRA treatment did not change the total SOC concentration although the labile SOC concentration increased. This typically is due to a small proportion of the labile fraction to the total SOC content. Our results suggest that this water-rich mature forest is resistant to rainfall amount changes to a great extent (e.g., decrease of 50% as in the present study) from the SOC stabilization perspective, while changes in rainfall frequency could exert more notable effects.

28586. 题目: Effects of biochar on the ecological performance of a subtropical landfill
文章编号: N18071212
期刊: Science of The Total Environment
作者: Xun Wen Chen, James Tsz Fung Wong, Zhan Ting Chen, Thomas Wui Lung Tang, Hao Wen Guo, Anna Oi Wah Leung, Charles Wang Wai Ng, Ming Hung Wong
更新时间: 2018-07-12
摘要: Landfills commonly occupy large areas of land that may be ecologically important. Ecological restoration of landfill cover is a necessary approach to rebuild sustainable habitats. However, unfavourable soil conditions and invasion by exotic plants in certain regions hinder the restoration. In this study, the effects of biochar as a soil amendment on the restoration of a landfill cover were investigated under field condition. Topsoils of a landfill cover in the subtropical region (Shenzhen, China) were mixed with 0, 5 and 10% (v/v) of biochar. Soil pH, electronic conductivity, organic matter, total organic carbon, water content, total N and total P were enhanced by biochar amendment. After nine months of self-succession, plant productivity, species richness and diversity were enhanced by biochar. The structures of soil bacterial and arbuscular mycorrhizal (AM) fungal communities were changed, and species richness and diversity were moderately promoted. Enhanced plant growth and diversity were probably attributed to a number of enhanced bacterial functions related to nutrient cycling including aerobic ammonia oxidation, aerobic nitrite oxidation, nitrification, sulphur respiration, nitrate respiration, nitrogen respiration, ureolysis, chemoheterotrophy and fermentation. The higher abundances of bacteria Streptomyces sp. and Pseudomonas sp. in biochar treatments potentially enhanced the AM fungal diversity. The bacterial diversity was more related to the soil properties, especially pH, than AM fungi. Continuous monitoring is necessary to track the changes of species composition and ecological functions over time. This is the first comprehensive study on the effects of biochar on the ecological performance of a man-made ecosystem. In addition to agricultural application, biochar can be used for restoring degraded lands.

28587. 题目: Treatment of rural domestic wastewater using multi-soil-layering systems: Performance evaluation, factorial analysis and numerical modeling
文章编号: N18071211
期刊: Science of The Total Environment
作者: Pei Song, Guohe Huang, Chunjiang An, Ju Shen, Peng Zhang, Xiujuan Chen, Jian Shen, Yao Yao, Rubing Zheng, Chaoxing Sun
更新时间: 2018-07-12
摘要: The discharge of wastewater in rural areas without effective treatment may result in contamination of surrounding surface water and groundwater resources. This study explored the wastewater treatment performance of multi-soil-layering (MSL) systems through interactive factorial analysis. MSL systems showed good performances under various operating conditions. The COD and BOD5 removal rates in MSL systems could reach 98.53 and 93.66%, respectively. The performances of MSL systems in TP removal stayed at high levels ranged from 97.97 to 100% throughout the experiments. The NH4+ N removal rates of the well performed MSL systems reached highest levels ranging from 89.96 to 100%. The TN removal rates of aerated MSL systems ranged from 51.11 to 64.44% after 72 days of operation. The independent effects of bottom submersion, microbial amendment and aeration, as well as most interactions were significant. The performance of MSL systems was mainly affected by bottom submersion and aeration as well as their interactions. Aeration was the most positive factor for the removal of organic matter, TP and NH4+ N. However, oxygenated environment was unfavorable for NO3 N removal. In the submerged area with limited oxygen, the microbial transformation of NO3 N still occurred. A stepwise-cluster inference model was developed for tackling the multivariate nonlinear relationships in contaminant removal processes. The results can help obtain a better understanding of the complicated processes among contaminant removal in MSL systems.

28588. 题目: Biofouling in ultrafiltration process for drinking water treatment and its control by chlorinated-water and pure water backwashing
文章编号: N18071210
期刊: Science of The Total Environment
作者: Senlin Shao, Yue Wang, Danting Shi, Xuezhi Zhang, Chuyang Y. Tang, Zizheng Liu, Jiangyun Li
更新时间: 2018-07-12
摘要: We investigated biofouling in ultrafiltration (UF) for drinking water treatment and its control by backwashing with chlorinated-water or pure water. By using sodium azide to suppress biological growth, the relative contribution of biofouling to total fouling was estimated, and its value (5.3–56.0%) varied with the feed water, and increased with the increases of filtration time and membrane flux. The biofouling layer could partially remove biodegradable organic matter and ammonia (32.9–74.2%). Backwashing using chlorinated-water partly inactivated the microorganisms (23.8%) but increased the content of extracellular polymeric substances (7.7%) in the biofouling layer. In contrast, backwashing using pure water led to a looser and more porous fouling layer according to optical coherence tomography observation. Consequently, the latter was more effective in reducing fouling resistance (33.41% reduction) compared to backwashing by chlorinated-water (8.6%). These findings reveal the critical roles of biofouling in pollutants removal in addition to membrane permeability, which has important implications for addressing seasonal ammonia pollution.

28589. 题目: Estimation of soil organic carbon stocks of two cities, New York City and Paris
文章编号: N18071209
期刊: Science of The Total Environment
作者: Aurélie Cambou, Richard K. Shaw, Hermine Huot, Laure Vidal-Beaudet, Gilles Hunault, Patrice Cannavo, Fran?ois Nold, Christophe Schwartz
更新时间: 2018-07-12
摘要: In cities, the strong heterogeneity of soils, added to the lack of standardized assessment methods, serves as a barrier to the estimation of their soil organic carbon content (SOC), soil organic carbon stocks (SOCS; kgC m 2) and soil organic carbon citywide totals (SOCCT; kgC). Are urban soils, even the subsoils and sealed soils, contributing to the global stock of C To address this question, the SOCS and SOCCT of two cities, New York City (NYC) and Paris, were compared. In NYC, soil samples were collected with a pedological standardized method to 1 m depth. The bulk density (Db) was measured; SOC and SOCS were calculated for 0–30 cm and 30–100 cm depths in open (unsealed) soils and sealed soils. In Paris, the samples were collected for 0–30 cm depth in open soils and sealed soils by different sampling methods. If SOC was measured, Db had to be estimated using pedotransfer functions (PTFs) refitted from the literature on NYC data; hence, SOCS was estimated. Globally, SOCS for open soils were not significantly different between both cities (11.3 ± 11.5 kgC m 2 in NYC; 9.9 ± 3.9 kgC m 2 in Paris). Nevertheless, SOCS was lower in sealed soils (2.9 ± 2.6 kgC m 2 in NYC and 3.4 ± 1.2 kgC m 2 in Paris). The SOCCT was similar between both cities for 0–30 cm (3.8 TgC in NYC and 3.5 TgC in Paris) and was also significant for the 30–100 cm layer in NYC (5.8 TgC). A comparison with estimated SOCCT in agricultural and forest soils demonstrated that the city's open soils represent important pools of organic carbon (respectively 110.4% and 44.5% more C in NYC and Paris than in agricultural soils, for 0–30 cm depth). That was mainly observable for the 1 m depth (146.6% more C in NYC than in agricultural soils). The methodology to assess urban SOCS was also discussed.

28590. 题目: Spatial and seasonal occurrence of micropollutants in four Portuguese rivers and a case study for fluorescence excitation-emission matrices
文章编号: N18071208
期刊: Science of The Total Environment
作者: Marta O. Barbosa, Ana R. Ribeiro, Nuno Ratola, Ethan Hain, Vera Homem, M. Fernando R. Pereira, Lee Blaney, Adrián M.T. Silva
更新时间: 2018-07-12
摘要: The European Union (EU) has recommended the monitoring of specific priority substances (PSs, Directive 2013/39) and some contaminants of emerging concern (CECs, Decision 2015/495) in surface waterbodies. The present study provides spatial distributions and temporal variations of a wide range of multi-class PSs and CECs in four stressed rivers in Portugal (Ave, Le a, Antu , and Cértima). Thirteen micropollutants were found in all four rivers, including the priority pesticide isoproturon (up to 92 ng L 1), various pharmaceuticals (up to 396 ng L 1), and the UV-filter 2-ethyl-hexyl-4-methoxycinnamate (EHMC, up to 562 ng L 1) identified in Decision 2015/495. The industrial priority compound perfluorooctanesulfonic acid (PFOS) was found in three rivers (Antu , Cértima, and Le a) below the method quantification limit, together with four pharmaceuticals not included in these EU guidelines. The already banned priority pesticide atrazine was detected in Ave, Antu , and Le a (up to 41 ng L 1) and simazine in Cértima and Le a (up to 26 ng L 1). Acetamiprid and imidacloprid (included in Decision 2015/495) were only detected during the dry season in the Ave. Le a river was selected as a waterbody case study for assessment of fluorescence excitation-emission matrices (EEMs). These results matched the spatial distribution trend of micropollutants along the river, with stronger fluorescence response and higher concentrations being found downstream of industrial areas and urban wastewater treatment plants (WWTPs). Moreover, the fluorescence signature of surface water collected downstream of an urban WWTP aligned very well with that obtained for the respective WWTP effluent. Thus, actions are needed to preserve a good environmental status of these stressed European waterbodies.

28591. 题目: Different bacterial species and their extracellular polymeric substances (EPSs) significantly affected reverse osmosis (RO) membrane fouling potentials in wastewater reclamation
文章编号: N18071207
期刊: Science of The Total Environment
作者: Tong Yu, Hao Sun, Zhuo Chen, Yun-Hong Wang, Zheng-Yang Huo, Nozomu Ikuno, Kazuki Ishii, Yan Jin, Hong-Ying Hu, Yin-Hu Wu, Yun Lu
更新时间: 2018-07-12
摘要: Biofouling represents the “Achilles' heel” for reverse osmosis (RO) processes due to the growth of bacteria and their production of extracellular polymeric substances (EPSs). Although the microbial community structure on the RO membrane has been analysed previously, the bacterial species with a high potential of causing RO membrane fouling have not yet been identified clearly. The key components in EPSs causing RO membrane fouling have not been revealed either. In this study, seven different bacterial species were isolated from fouled RO membranes, and their EPSs were analysed in terms of the content of polysaccharides and proteins, fluorescence characteristics and molecular weight (MW) distributions. The membrane fouling potentials of these bacterial species and EPSs were evaluated based on normalized flux decline. Generally, under the same growth conditions, bacterial species with higher EPS concentrations, rather than higher cell numbers, resulted in more severe flux decline. The flux decline showed an apparent positive correlation with the EPS concentration, indicating that the concentration of EPS rather than the bacterial number mainly contributed to biofouling. Furthermore, it was found that the MW distribution was the key factor affecting the RO membrane fouling potential of EPSs from different bacterial species. With the increase in the percentage of the high-MW fraction (>10 kDa) in the EPSs from 12.6% to 74.4%, the normalized flux decline increased from 0.4 to 0.59. The components in EPSs with a MW over 10 kDa were also separated by the ultrafiltration membrane and were proven to have a higher membrane fouling potential.

28592. 题目: Feasting on terrestrial organic matter: dining in a dark lake changes microbial decomposition
文章编号: N18071206
期刊: Global Change Biology
作者: Amelia Fitch , Chloe Orland , David Willer , Erik J S Emilson , Andrew J Tanentzap
更新时间: 2018-07-12
摘要: Boreal lakes are major components of the global carbon cycle, partly because of sediment‐bound heterotrophic microorganisms that decompose within‐lake and terrestrially derived organic matter (t‐OM). The ability for sediment bacteria to break down and alter t‐OM may depend on environmental characteristics and community composition. However, the connection between these two potential drivers of decomposition is poorly understood. We tested how bacterial activity changed along experimental gradients in the quality and quantity of t‐OM inputs into littoral sediments of two small boreal lakes, a dark and a clear lake, and measured the abundance of operational taxonomic units and functional genes to identify mechanisms underlying bacterial responses. We found that bacterial production (BP) decreased across lakes with aromatic dissolved organic matter (DOM) in sediment pore water, but the process underlying this pattern differed between lakes. Bacteria in the dark lake invested in the energetically costly production of extracellular enzymes as aromatic DOM increased in availability in the sediments. By contrast, bacteria in the clear lake may have lacked the nutrients and/or genetic potential to degrade aromatic DOM, and instead mineralized photo‐degraded OM into CO2. The two lakes differed in community composition and the higher concentration of dissolved organic carbon in the clear lake was associated with the community assemblages in the clear lake. Furthermore, functional genes relating to t‐OM degradation were relatively higher in the dark lake. Our results suggest that future changes in t‐OM inputs to lake sediments will have different effects on carbon cycling depending on the potential for photo‐degradation of OM and composition of resident bacterial communities.

28593. 题目: Bacterial growth through microfiltration membranes and NOM characteristics in an MF-RO integrated membrane system: Lab-scale and full-scale studies
文章编号: N18071205
期刊: Water Research
作者: Ji Won Park, Young Joo Lee, Anne S. Meyer, Isabel Douterelo, Sung Kyu Maeng
更新时间: 2018-07-12
摘要: Biofilm formation on membrane surfaces causes many operational problems such as a decrease in permeate flux and an increase in hydraulic resistance. In this study, the ability of bacteria to pass through microfiltration (MF) membranes and the growth potential of microfilterable bacteria were investigated in order to understand biofouling in MF-reverse osmosis (RO) integrated membrane systems. Growth of microfilterable bacteria in MF permeate was observed, indicating that not all MF membranes can guarantee the total rejection of bacteria. Changes in natural organic matter (NOM) characteristics and growth potential of bacteria during the treatment process are important factors in the occurrence of biofilm development in water treatment systems. Analysis of protein-like and humic-like substances in NOM of two successive RO stages revealed an increase in the concentrations of both biopolymers and humic substances of RO concentrates. Unexpectedly, the use of antiscalants was seen to enhance the growth of bacteria in the RO feed water in this study. Bacterial 16s rRNA pyrosequencing revealed that passing source water through the MF membranes dramatically changed bacterial community structure. The bacterial communities that passed through the MF steps primarily belonged to the family Comamonadaceae. However, several bacteria groups including Flavobacteriaceae, Sphingobacteriaceae and Sphingomonadaceae selectively composed the biofilm community formed on the RO membranes. Thus, understanding the selectivity and filterability of MF towards microorganisms involved in biofouling on RO membrane surfaces is crucial for the improvement of membrane-related operational processes.

28594. 题目: Changes in atrazine speciation and the degradation pathway in red soil during the vermiremediation process
文章编号: N18071204
期刊: Journal of Hazardous Materials
作者: Zhong Lin, Zhen Zhen, Yanqiu Liang, Jin Li, Jiewen Yang, Laiyuan Zhong, Lirong Zhao, Yongtao Li, Chunling Luo, Lei Ren, Dayi Zhang
更新时间: 2018-07-12
摘要: Atrazine (2-chloro-4-ethylamino-6-isopropylamino-1,3,5-triazine) is a triazine herbicide intensively used in agricultural production and is often detected in different environmental matrices at concentrations above the permitted limit. This study investigated the influence of two earthworm species (epigeic Eisenia foetida and endogeic Amynthas robustus) on atrazine speciation and the degradation pathway. Our results revealed that both earthworms significantly accelerated atrazine degradation in a 28-day vermiremediation, and the residual atrazine declined from 4.23 ± 0.21 mg/kg in bulk soils to 0.51 ± 0.29 mg/kg (E. foetida) and 0.43 ± 0.19 mg/kg (A. robustus). By consuming organic matter (from 40.37 ± 1.14 to 36.31 ± 1.55 and 34.59 ± 1.13 g/kg for E. foetida and A. robustus) and neutralizing the soil pH (from 5.37 ± 0.27 to 6.36 ± 0.11 and 6.61 ± 0.30 for E. foetida and A. robustus), both earthworms reduced humus-fixed atrazine and increased the available atrazine. The percentage of available atrazine increased from 8.80 ± 0.21% in bulk soil to 10.30 ± 0.29% and 16.42 ± 0.18% in the vermiremediation treatments. Both earthworms promoted the hydroxyatrazine pathway by consuming soil organic matter and encouraged the deethylatrazine/deisopropylatrazine pathway by neutralizing the soil pH. Our findings unravel a new mechanism of vermiremediation by improving the soil physical-chemical properties and altering the atrazine degradation pathway, providing new insights into the influential factors on atrazine bioremediation in red soil.

28595. 题目: Effect of long-term electrodialytic soil remediation on Pb removal and soil weathering
文章编号: N18071203
期刊: Journal of Hazardous Materials
作者: Gry Skibsted, Lisbeth M. Ottosen, Maria Elektorowicz, Pernille E. Jensen
更新时间: 2018-07-12
摘要: Weathering of soil minerals during long-term electrochemical soil remediation was evaluated for two different soils: an industrially Pb contaminated soil with high carbonate content and an unpolluted soil with low carbonate content. A constant current of 5 mA was applied for 842 days, and sampling was made 22 times during the treatment. The overall qualitative mineral composition was unaffected by electrodialysis, except for calcite removal which was complete. However, dissolution and removal of Al, Fe, Si, Mg, Ca and Pb from the soil during the treatment exceeded the fraction extractable by digestion in 7 M HNO3, and provided evidence of enhanced mineral dissolution induced by the current. Nevertheless, the total dissolved Si and Al only constituted 0.2–0.3% and 1.1–3.5% of the total content, while the Pb overall removal from the contaminated soil was only 8.1%. An observed reduction in the dry matter of 4.5% and 13.5% from the two soils, respectively was mainly due to dissolution of CaCO3 and organic matter, but also included a minor dissolution of other soil minerals.

28596. 题目: Priming mechanisms with additions of pyrogenic organic matter to soil
文章编号: N18071202
期刊: Geochimica et Cosmochimica Acta
作者: Silene DeCiucies, Thea Whitman, Dominic Woolf, Akio Enders, Johannes Lehmann
更新时间: 2018-07-12
摘要: Additions of pyrogenic organic matter (PyOM) to soil have been shown to both increase and decrease mineralization of native soil organic carbon (nSOC). This change in mineralization rate is referred to as priming, and may have important implications for carbon (C) turnover in soil. This study quantifies both positive and negative priming mechanisms using high-resolution carbon dioxide (CO2) measurements using a series of short-term incubation experiments with 13C-labeled PyOM added to a temperate forest soil. Moisture, nutrient availability and pH were adjusted to minimize any differential effects on nSOC mineralization. Irrespective of pyrolysis temperature (200-750°C), addition of 10 mg PyOM g-1 soil significantly decreased mineralization of nSOC. Dilution was measured against inorganic bulking materials with different surface areas and accounted for 19% of negative priming observed at day 7, and 13% at day 35. In comparison, substrate switching caused only 1% of negative priming assumed to be equivalent to PyOM mineralization itself. Inhibition did not explain reductions in nSOC mineralization since the microbial biomass did not significantly decrease (p > 0.05). Sorptive protection of dissolved organic carbon (DOC) was responsible for the majority of negative priming observed with PyOM additions based on adsorption isotherm experiments as well as co-location of nSOC on PyOM surfaces shown by nanoSIMS. Maximum sorption of soil DOC was 29 times higher to PyOM pyrolyzed at 450°C than to topsoil, and tripled with an increase in pyrolysis temperature to 750°C. This tripling in DOC sorption potential to PyOM produced at 750°C in comparison to 450°C was only reflected in a less than twice lower nSOC mineralization. Sorptive protection was with 80% the dominant negative priming mechanism on monthly timescales and likely beyond. These results have implications for long-term SOC storage, because sorption has more persistent effects than substrate switching or dilution.

28597. 题目: A liquid chromatography–mass spectrometry method for analysis of intact fatty‐acid‐based lipids extracted from soil
文章编号: N18071201
期刊: European Journal of Soil Science
作者: C. R. Warren
更新时间: 2018-07-12
摘要: Fatty‐acid‐based lipids are considered to be indicators of the structure and function of soil microbial biomass. Identifying and quantifying intact fatty‐acid‐based lipids in soil extracts is challenging because lipids range from polar (e.g. phospholipids and other membrane lipids) to non‐polar (e.g. triacylglycerols involved in energy storage). The aim of this study was to develop a liquid chromatography–mass spectrometry (LC–MS) method to identify and quantify intact fatty‐acid‐based lipids in soil extracts. Reversed‐phase LC separated fatty‐acid‐based lipids ranging from polar to non‐polar in one chromatographic analysis. Within classes, individual lipid species were separated predictably from one another on the basis of carbon numbers and degree of unsaturation, such that chromatographic retention time could be used to aid identification. Lipid species were identified based on intact mass of the lipid and by fragmentation into structure‐specific fragments that enabled compound classes and fatty acyl chains to be determined. Detection limits in positive and negative mode were better than 10 nmol l 1 for most lipid standards. In an extract of soil, 74 lipids from 10 classes were identified. The main non‐polar lipids were 12 diacylglyerol species and 16 triacylglycerol species. Polar lipids included phosphatidylcholines, phosphatidylethanolamines, monomethyl‐phosphatidylethanolamines, phosphatidylinositols and three classes of betaine lipid (diacylgycerol‐N‐trimethylhomoserine; diacylglycerylhydroxymethy‐N,N,N‐trimethyl‐β‐alanine; and diacylglycerylcarboxyhydroxymethylcholine). The LC–MS method developed provides a powerful analytical tool for analysis of fatty‐acid‐based lipids ranging from polar to non‐polar and should be useful for the culture‐ and gene‐independent assay of soil function.

28598. 题目: Isolating organic carbon fractions with varying turnover rates in temperate agricultural soils – A comprehensive method comparison
文章编号: N18071115
期刊: Soil Biology and Biochemistry
作者: Christopher Poeplau, Axel Don, Johan Six, Michael Kaiser, Dinesh Benbi, Claire Chenu, M. Francesca Cotrufo, Delphine Derrien, Paola Gioacchini, Stephanie Grand, Edward Gregorich, Marco Griepentrog, Anna Gunina, Michelle Haddix, Yakov Kuzyakov, Anna Kühnel, Lynne M. Macdonald, Jennifer Soong, Sylvain Trigalet, Marie-Liesse Vermeire
更新时间: 2018-07-11
摘要: Fractionation of soil organic carbon (SOC) is crucial for mechanistic understanding and modeling of soil organic matter decomposition and stabilization processes. It is often aimed at separating the bulk SOC into fractions with varying turnover rates, but a comprehensive comparison of methods to achieve this is lacking. In this study, a total of 20 different SOC fractionation methods were tested by participating laboratories for their suitability to isolate fractions with varying turnover rates, using agricultural soils from three experimental sites with vegetation change from C3 to C4 22–36 years ago. Enrichment of C4-derived carbon was traced and used as a proxy for turnover rates in the fractions. Methods that apply a combination of physical (density, size) and chemical (oxidation, extraction) fractionation were identified as most effective in separating SOC into fractions with distinct turnover rates. Coarse light SOC separated by density fractionation was the most C4-carbon enriched fraction, while oxidation-resistant SOC left after extraction with NaOCl was the least C4-carbon enriched fraction. Surprisingly, even after 36 years of C4 crop cultivation in a temperate climate, no method was able to isolate a fraction with more than 76% turnover, which challenges the link to the most active plant-derived carbon pools in models. Particles with density >2.8 g cm 3 showed similar C4-carbon enrichment as oxidation-resistant SOC, highlighting the importance of sesquioxides for SOC stabilization. The importance of clay and silt-sized particles (<50 μm) for SOC stabilization was also confirmed. Particle size fractionation significantly outperformed aggregate size fractionation, due to the fact that larger aggregates contain smaller aggregates and organic matter particles of various sizes with different turnover rates. An evaluation scheme comprising different criteria was used to identify the most suitable methods for isolating fractions with distinct turnover rates, and potential benefits and trade-offs associated with a specific choice. Our findings can be of great help to select the appropriate method(s) for fractionation of agricultural soils.

28599. 题目: Nitrogen functional gene activity in soil profiles under progressive vegetative recovery after abandonment of agriculture at the Puding Karst Critical Zone Observatory, SW China
文章编号: N18071114
期刊: Soil Biology and Biochemistry
作者: Dandan Li, Xinyu Zhang, Sophie M. Green, Jennifer A.J. Dungait, Xuefa Wen, Yuqian Tang, Zhiming Guo, Yang Yang, Xiaomin Sun, Timothy A. Quine
更新时间: 2018-07-11
摘要: At the end of the 20th century, China launched the ‘Grain-for-Green’ Project (GGP) that recommended the abandonment of low-yielding sloping farmland (>15°) prone to soil degradation by erosion, to allow recovery through natural vegetative regeneration. The effect of this policy on soil nitrogen (N) cycling, as fertilization applications are also withdrawn after abandonment, is poorly understood. A space-for-time approach was applied to investigate the responses of nitrogen functional genes (NFGs) in soil profiles (surface to bedrock) associated with progressive vegetative recovery (sloping farmland > recently abandoned sloping farmland > secondary forest > primary forest) at the Puding Karst Critical Zone Observatory in Guizhou province, southwest China. Coincident soil chemical properties (dissolved organic carbon (DOC), nitrate (NO3--N), ammonium (NH4+-N), available inorganic phosphorus (AP), soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP)) were also quantified. We found that the absolute abundance of NFGs significantly varied according to the phase of vegetation recovery, and that concentrations of AP and NO3--N were the best explanatory variables. The external N from fertilizer application promoted the absolute abundances of ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) in sloping farmland. The relative abundances of chiA (associated with decomposition) increased with soil depth across all vegetation recovery phases. The relative abundances of chiA and nifH (associated with N fixation) accounted for the largest proportion (58–72%) of the measured NFGs, indicating that active N-acquisition increased along the vegetation recovery gradient. The ratios of (chiA + nifH)/(AOA + AOB) and the sums of (nirK + nirS) were larger in the forest soil than those of sloping farmland and abandoned sloping farmland, implying a greater capacity for N storage potential, though accompanied by increased gas N emission potential, in the karst forest ecosystems. Our results provide a new and comprehensive understanding of soil N cycling potentials at the microscale in degraded and recovering karst ecosystems.

28600. 题目: Responses of fungal–bacterial community and network to organic inputs vary among different spatial habitats in soil
文章编号: N18071113
期刊: Soil Biology and Biochemistry
作者: Wei Zheng, Zhiyuan Zhao, Qingli Gong, Bingnian Zhai, Ziyan Li
更新时间: 2018-07-11
摘要: Interactions among the species in microbial communities are important for organic matter turnover and nutrient cycling in the soil. Their responses to organic amendments have been studied recently but the co-occurrence patterns in different spatial soil habitats such as those with different sized aggregates are still unclear. Thus, we investigated networks comprising bacteria and fungi after the application of a cover crop for 9 years. The microbial community compositions and their co-occurrence networks were examined in the whole soil and different sized soil aggregates (>0.25 mm, 0.053–0.25 mm, and <0.053 mm). The microbial community compositions and their responses to the cover crop varied in the whole soil and aggregate fractions. Network analysis in the whole soil and different sized aggregates showed that the competition between fungi and bacteria in the whole soil increased due to the annual organic material input, but the fungi–bacteria relationships varied among different sized aggregates. In particular, the competition between fungi and bacteria increased in macroaggregates but decreased in silt + clay due to organic material inputs. Thus, the co-occurrence networks determined for the fungal and bacterial communities in various soil aggregates were very different from those in the whole soil, and their responses to organic inputs also varied in different spatial habitats in the soil.