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25801. 题目: Spatial differentiation of cultivated soils using compound-specific stable isotopes (CSSIs) in a temperate agricultural watershed in Manitoba, Canada
文章编号: N19072608
期刊: Journal of Soils and Sediments
作者: Dominic G. Reiffarth, Ellen L. Petticrew, Philip N. Owens, David A. Lobb
更新时间: 2019-07-26
摘要: Purpose: Compound-specific stable isotopes (CSSIs) of very long-chain fatty acids (VLCFAs) of plant origin were investigated in a soil and sediment tracing context in a watershed in Manitoba, Canada. Spatial and temporal variability in δ13CFA values and concentrations was examined at the point, transect, and field scales to determine the (1) ability to differentiate sediment sources in C3-cropped fields, (2) impact of subsampling on source tracer fingerprints, and (3) major sediment source for a downstream mixture using the Bayesian unmixing model MixSIAR. Materials and methods: Analysis was performed for five agricultural fields over six sampling periods. Soil and sediment samples (320) were processed for VLCFA analyses (C20:0–C30:0, C32:0). Quantification was performed by gas chromatography–flame ionization detection (GC-FID) and 13C determination by GC combustion–isotope ratio mass spectrometry (GCC-IRMS). Data were analyzed using weighted t tests to differentiate fields by δ13CFA values. The major sediment source was determined using the following steps: (1) a point-in-polygon approach to identify VLCFA tracers; (2) unmixing using MixSIAR; (3) source apportioning using VLCFA concentrations and %C. Results and discussion: VLCFA δ13CFA values vary spatially within a cropped field due to environmental factors. Sediment source fingerprints are dependent on the variability in δ13CFA values and the quantitative combining of subsamples. Cropped fields that appeared homogeneous exhibited a large range in δ13CFA values, with variability greatest for fall and spring samples; concentrations were lowest at these times. Historical field boundaries played a role. A downstream sediment mixture (June 2013) was analyzed and found to correspond with source data from August 2012. Sediment mixture data (δ13CFA) for several VLCFAs were found to fall within the source mixing polygons produced by using two cultivated fields and a riparian zone sample as sources. Conclusions: Variability in δ13CFA values increased in fall and spring, which could affect the number of subsamples required per source. Most fields could be spatially differentiated using a weighted t test, but not necessarily using the same VLCFA chain lengths. Two spatially separated fields with similar cropping histories were difficult to differentiate, but one of the fields was more prone to VLCFA losses. Only one of several source sampling periods led to successful unmixing, suggesting multiple sampling periods for source and/or mixture are necessary. Understanding the spatial and temporal variability affecting δ13CFA values in source sediments is particularly important for tracing studies using biomarkers in producing a representative fingerprint.
25802. 题目: Increased microbial growth, biomass and turnover drive soil organic carbon accumulation at higher plant diversity
文章编号: N19072607
期刊: Global Change Biology
作者: Judith Prommer, Tom W. N. Walker, Wolfgang Wanek, Judith Braun, David Zezula, Yuntao Hu, Florian Hofhansl, Andreas Richter
更新时间: 2019-07-26
摘要: Species‐rich plant communities have been shown to be more productive and to exhibit increased long‐term soil organic carbon (SOC) storage. Soil microorganisms are central to the conversion of plant organic matter into SOC, yet the relationship between plant diversity, soil microbial growth, turnover as well as carbon use efficiency (CUE) and SOC accumulation is unknown. As heterotrophic soil microbes are primarily carbon limited, it is important to understand how they respond to increased plant‐derived carbon inputs at higher plant species richness (PSR). We used the long‐term grassland biodiversity experiment in Jena, Germany, to examine how microbial physiology responds to changes in plant diversity and how this affects SOC content. The Jena Experiment considers different numbers of species (1‐60), functional groups (1‐4) as well as functional identity (small herbs, tall herbs, grasses and legumes). We found that plant species richness (PSR) accelerated microbial growth and turnover and increased microbial biomass and necromass. Plant species richness also accelerated microbial respiration, but this effect was less strong than for microbial growth. In contrast, PSR did not affect microbial CUE or biomass‐specific respiration. Structural equation models (SEMs) revealed that PSR had direct positive effects on root biomass, and thereby on microbial growth and microbial biomass carbon. Finally, PSR increased SOC content via its positive influence on microbial biomass carbon.
25803. 题目: Functionalized biochar/clay composites for reducing the bioavailable fraction of arsenic and cadmium in river sediment
文章编号: N19072606
期刊: Environmental Toxicology and Chemistry
作者: Xiaohua Wang, Yanling Gu, Xiaofei Tan, Yunguo Liu, Yahui Zhou, Xinjiang Hu, XiaoXi Cai, Weihua Xu, Chen Zhang, Shaoheng Liu
更新时间: 2019-07-26
摘要: Biochar has been frequently applied for the treatment of heavy metals pollution in water and soil, its effect in contaminated sediments needs further research. In order to improve the ability of biochar for heavy metals immobilization in sediment, this study prepared functionalized biochar/attapulgite composite by pyrolysis of the clay attapulgite and zinc chloride pretreated rice straw biomass. Compared with the original biochar, biochar/attapulgite composite had a large increase in specific surface area, pore volume, oxygen‐containing functional groups and cation exchange capacity. Biochar could effectively improve the dispersibility of attapulgite as a matrix. The results showed that the biochar/attapulgite composite could effectively reduce the bioavailable fraction of As and Cd in the river sediment, which had a great improvement compared with the raw biochar. After the sediment was treated by different biochar/attapulgite composites, the concentrations of As and Cd in the overlying water and pore water, and the content of acid extractable and TCLP extractable As and Cd in solid phase of sediment decreased significantly. Both zinc chloride activation and attapulgite were benefit for As and Cd immobilization in sediment by biochar/attapulgite composite. The results suggested that biochar/attapulgite composite can be used as an efficient in‐situ sorbent amendments to improve the immobilization ability of the sediment to heavy metals.
25804. 题目: Photovoltaic electrolysis improves nitrogen and phosphorus removals of biochar-amended constructed wetlands
文章编号: N19072605
期刊: Ecological Engineering
作者: Yan Gao, Cheng Yan, Ruping Wei, Wen Zhang, Jianing Shen, Mingxuan Wang, Bin Gao, Yicheng Yang, Liuyan Yang
更新时间: 2019-07-26
摘要: To deeply remove nitrogen (N) and phosphorus (P) from constructed wetlands (CWs), the authors found that CWs can be combined with the use of photovoltaic energy for best results. Thus, electrolysis-integrated, biochar-amended, horizontal (subsurface)-flow-constructed wetlands (E-BHFCWs) were combined with free-water, surface-constructed wetlands (FWSCWs) to remove N and P from secondary effluent water of a wastewater treatment plant (WWTP). Photovoltaic energy was used for electrolysis to intensify the removal of nitrate nitrogen (NO3−-N), ammonium nitrogen (NH3-N), and phosphate phosphorus (PO43−-P) in E-BHFCWs. In addition, FWSCWs were constructed to further remove NO3−-N, NH3-N, PO43−-P and iron ions in effluent of E-BHFCWs and to enhance DO concentration. For the E-BHFCWs combined with FWSCWs, the removal rates of NO3−-N, NH3-N, and PO43−-P were 73.28%, 53.11% and 67.58% respectively. The removal amounts of NO3−-N, NH3-N, and PO43−-P were about 211.08 kg N/a, 64.81 kg N/a and 10.46 kg P/a by E-BHFCWs. Photovoltaic electrolysis in E-BHFCWs was able to enhance NO3−-N removal through electrochemical reduction by iron cathodes, enriched hydrogenotrophic bacteria in the substrate, and by modified biochar substrate in situ with iron ions. Meanwhile, NH3-N was mainly removed by modified biochar adsorption, nitrifying microbes, and plant uptake. The removal rate of PO43−-P was also enhanced due to the formation of ferric ions by the anodization of sacrificial iron anodes, causing chemical precipitation, physical adsorption, and flocculation of PO43−-P. Thus, E-BHFCWs combined with FWSCWs are capable of effectively promoting removals of NO3−-N, NH3-N, and PO43−–P and provide a new insight into a new energy flow that can enhance N and P removals of CWs.
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25805. 题目: Impacts of carbonization temperature on the Pb(II) adsorption by wheat straw-derived biochar and related mechanism
文章编号: N19072604
期刊: Science of The Total Environment
作者: Yaoyao Cao, Guanghui Shen, Yang Zhang, Chongfeng Gao, Yanfei Li, Peizhen Zhang, Weihua Xiao, Lujia Han
更新时间: 2019-07-26
摘要: To determine the quantitative correlations between physicochemical characteristics and Pb(II) adsorption amounts of biochar fractions, we prepared wheat straw-derived biochar under various carbonization temperatures (300–900 °C). The different fractions of the wheat straw-derived biochar, water-soluble material (WM), acid-soluble material (AM), and organic material (OM), were acquired. The ash content, ultimate analysis, pH, ion strength (IS), cation exchange capacity (CEC), and acidic functional groups (AFG) were characterized. The Pb(II) adsorption amounts of different biochars and their fractions were determined. The results revealed that the proportions of biochar fractions (WM, AM, and OM) varied with various carbonization temperatures. The maximum Pb(II) adsorption amount of wheat straw-derived biochar (qTotal) was 157.95 ± 0.13 mg/g obtained at 800 °C, and the quantitative correlations between Pb(II) adsorption amount (q) and carbonization temperature (T) can be elaborated by qTotal = 170.72–336.62exp(−0.0035T) (R2 = 0.97), qWM = 106.18–390.10exp(−0.0046T) (R2 = 0.98), qAM = 496.16–477.74exp(−0.0001T) (R2 = 0.79), and qOM = 1.80 + 34.69exp(−0.0038T) (R2 = 0.85). For rate of contribution (RC) for Pb(II) adsorption, when T < 400 °C, the order was AM (60.72 ± 7.33%) > OM (23.41 ± 7.33%) > WM (15.87 ± 0.30%); however, when T ≥ 400 °C, the order was WM (52.31 ± 0.85% - 67.65 ± 2.99%) > AM (29.65 ± 0.46% - 35.77 ± 0.12%) > OM (2.30 ± 0.47% - 12.02 ± 2.43%). Moreover, qWM and qAM exhibited significant positive linear correlations with ash (qWM = 9.92Ash - 123.65, and qAM = 2.13Ash - 0.49), qTotal was predominantly affected by ash content (qTotal = 10.97 Ash - 95.49). The EDX, XRD, and FTIR analysis results further clarified that ion exchange and precipitation were the main adsorption mechanisms for Pb(II) adsorption by wheat straw-derived biochar.
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25806. 题目: Evaluation of integrated biochar with bacterial consortium on gaseous emissions mitigation and nutrients sequestration during pig manure composting
文章编号: N19072603
期刊: Bioresource Technology
作者: Yumin Duan, Sanjeev Kumar Awasthi, Tao Liu, Zengqiang Zhang, Mukesh Kumar Awasthi
更新时间: 2019-07-26
摘要: This study focused on evaluate the effectiveness of biochar alone compare integrated with bacterial consortium amendment on the gaseous emissions mitigation as well as carbon and nitrogen sequestration during pig manure composting. Six additive treatments were performed based on uniform mixing pig manure with wheat straw[bacterial consortium (T2), 12%wood biochar (T3), 12%wood biochar + bacterial consortium (T4), 12%wheat straw biochar (T5), 12%wheat straw biochar+ bacterial consortium (T6), while T1 without any additive]. The results obviously indicated that integrated use of biochar and bacterial consortium could remarkably relieved gaseous emissions, improved carbon and nitrogen conservation as well as accelerated maturity of composting. Notably the optimum combination was existed in T6 owing to lowest nutrient losses (nitrogen and carbon losses were 9.91 g/kg and 189.54 g/kg) and gas emissions (30.16 g/kg) as well as supreme maturity (germination index > 100%); it’s an economic-practical and environmental protection novel disposal approach for solid waste.
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25807. 题目: Perchlorate behavior in the context of black carbon and metal cogeneration following fireworks emission at Oak Lake, Lincoln, Nebraska, USA
文章编号: N19072602
期刊: Environmental Pollution
作者: Manish Kumar, Daniel D. Snow, Yusong Li, Patrick J. Shea
更新时间: 2019-07-26
摘要: The imprints of fireworks displays on the adjacent water body were investigated from the perspective of cogeneration of black carbon, metals and perchlorate (ClO4−). In particular, the mixing and dissipation of ClO4− were studied at Oak Lake, Lincoln, Nebraska, following fireworks displays in 2015 and 2016. Following the display, ClO4− concentration in the water increased up to 4.3 μg/L and 4.0 μg/L in 2015 and 2016, respectively. A first-order model generally provided a good fit to the measured perchlorate concentrations from which the rate of dissipation was estimated as 0.07 d−1 in 2015 and 0.43 d−1 in 2016. SEM images show imprints of soot and metal particles in aerosol samples. EDS analysis of the lake sediment confirmed the presence of Si, K, Ca, Zn and Ba, most of which are components of fireworks. The δ13C range of −7.55‰ to −9.19‰ in the lake water system closely resembles fire-generated carbon. Cogeneration of black carbon and metal with perchlorate was established, indicating that ClO4− is an excellent marker of fireworks or a burning event over all other analyzed parameters. Future microcosmic, aggregation and column-based transport studies on black carbon in the presence of perchlorate and metals under different environmental conditions will help in developing transport and fate models for perchlorate and black carbon particles.
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25808. 题目: Strategies for the efficient estimation of soil organic carbon at the field scale with vis-NIR spectroscopy: Spectral libraries and spiking vs. local calibrations
文章编号: N19072601
期刊: Geoderma
作者: Michael Seidel, Christopher Hutengs, Bernard Ludwig, Sören Thiele-Bruhn, Michael Vohland
更新时间: 2019-07-26
摘要: Soil spectroscopy in the visible-to-near-infrared (vis-NIR) range is a cost-effective alternative analysis technique to determine soil organic carbon (SOC). The development and provision of large-scale soil spectral libraries (SSLs) further facilitates the application of vis-NIR spectroscopy for the rapid assessment of SOC. However, optimal strategies to apply SOC calibrations from SSLs to independent field sites have yet to be established.We tested the predictive ability of SOC calibrations based on three external SSLs at the national, regional and field scale by applying them to two field sites in Germany. The national-scale SSL was comprised as a subset of the European LUCAS 2009 topsoil database. This subset was further classified into a randomly selected subset and target site-specific subsets based on similarity of spectral characteristics and soil parent material. A regional- and a field-scale legacy dataset were additionally used to predict SOC at the two field sites and to compare the results with the performance of the LUCAS based models. SSL-based predictive models adapted to the characteristics of the target sites by means of spiking were evaluated against purely local calibrations.Models calibrated with spectra from the LUCAS library and the regional-scale dataset predicted the SOC contents of the target field sites generally poorly (0.45 ≤ RPD ≤ 2.08), largely as a result of biased estimates. Spiking the models with only a few (~15) samples from the target sites reduced prediction bias drastically and thus yielded markedly improved SOC estimates for nearly all redeveloped models (1.30 ≤ RPD ≤ 3.69). Spiking the models based on the field-scale SSL with 15 samples produced better results than the spiked larger national and regional calibration sets, with RPD values of 5.66 and 4.14 for both target sites.Our results suggest that universal calibrations based exclusively on library spectra of larger scale are insufficient for accurate SOC assessments at the local scale even with pedogenetically or spectrally adapted calibration subsets. Spiking the vis-NIR models based on SSLs with a small number of target site samples allows a successful transfer of SOC calibrations, but does not necessarily yield more accurate predictions than local models developed exclusively with the spiking samples or calibrations based on field-scale SSL with similar characteristics, which may be preferable for model development if available.
25809. 题目: Deep Sulfate-Methane-Transition and sediment diagenesis in the Gulf of Alaska (IODP Site U1417)
文章编号: N19072510
期刊: Marine Geology
作者: Mark Zindorf, Christian März, Thomas Wagner, Sean P.S. Gulick, Harald Strauss, Jeff Benowitz, John Jaeger, Bernhard Schnetger, Laurel Childress, Leah LeVay, Cees van der Land, Michelle La Rosa
更新时间: 2019-07-25
摘要: Sediment samples from the Gulf of Alaska (GOA, IODP Expedition 341, Site U1417) have been analyzed to understand present and past diagenetic processes that overprint the primary sediment composition. No Sulfate-Methane Transition Zone (SMTZ) was observed at the zone of sulfate depletion, but a >200 m thick sulfate- and methane-free sediment interval occurred between the depth of sulfate depletion (~200 m) and the onset of methanogenesis (~440 m). We suggest that this apparent gap in biogeochemical processing of organic matter is caused by anaerobic oxidation of methane fueled by sulfate which is released during dissolution of barites at the upper boundary of the methane rich layer. Beneath the methanogenic zone, at ~650 m depth, pore-water sulfate concentrations increase again, indicating sulfate supply from greater depth feeding into a deep, inverse SMTZ. A likely explanation for the availability of sulfate in the deep sub-seafloor at U1417 is the existence of a deep aquifer related to plate bending fractures, which actively transports sulfate-rich water to, and potentially along, the interface between sediments and oceanic crust. Such inverse diagenetic zonations have been previously observed in marine sediments, but have not yet been linked to subduction-related plate bending. With the discovery of a deep inverse SMTZ in an intra-oceanic plate setting and the blocking of upward methane diffusion by sulfate released from authigenic barite dissolution, Site U1417 provides new insights into sub-seafloor pore-fluid and gas dynamics, and their implications for global element cycling and the deep biosphere.
25810. 题目: Rigorous Physicochemical Framework for Metal Ion Binding by Aqueous Nanoparticulate Humic Substances: Implications for Speciation Modeling by the NICA-Donnan and WHAM Codes
文章编号: N19072509
期刊: Environmental Science & Technology
作者: Raewyn M. Town, Herman P. van Leeuwen, Jérôme F. L. Duval
更新时间: 2019-07-25
摘要: Latest knowledge on the reactivity of charged nanoparticulate complexants toward aqueous metal ions is discussed in mechanistic detail. We present a rigorous generic description of electrostatic and chemical contributions to metal ion binding by nanoparticulate complexants, and their dependence on particle size, particle type (i.e., reactive sites distributed within the particle body or confined to the surface), ionic strength of the aqueous medium, and the nature of the metal ion. For the example case of soft environmental particles such as fulvic and humic acids, practical strategies are delineated for determining intraparticulate metal ion speciation, and for evaluating intrinsic chemical binding affinities and heterogeneity. The results are compared with those obtained by popular codes for equilibrium speciation modeling (namely NICA-Donnan and WHAM). Physicochemical analysis of the discrepancies generated by these codes reveals the a priori hypotheses adopted therein and the inappropriateness of some of their key parameters. The significance of the characteristic time scales governing the formation and dissociation rates of metal–nanoparticle complexes in defining the relaxation properties and the complete equilibration of the metal–nanoparticulate complex dispersion is described. The dynamic features of nanoparticulate complexes are also discussed in the context of predictions of the labilities and bioavailabilities of the metal species.
25811. 题目: Mixed carbonate-siliciclastic MICROFACIES from PERMIAN deposits of western Gondwana: Evidence of gradual marine to continental transition or episodes of marine transgression?
文章编号: N19072508
期刊: Sedimentary Geology
作者: Christiano Ng, Cristina Silveira Vega, Maria da Saudade Araujo Santos Maranhão
更新时间: 2019-07-25
摘要: At the end of the Paleozoic, several intracratonic basins developed in Gondwana, including the Paraná Basin in Western Gondwana. Permian sedimentary units include the Passa Dois Group, which encompasses four formations: the Irati, Serra Alta, Teresina, and Rio do Rasto, and represents a transition from marine to continental depositional environments. Its strata correlate extensively, from Argentina to South Africa, and the Irati and Teresina formations in particular present mixed carbonate-siliciclastic successions. This interval has been speculated to have formed under several different paleoenvironmental scenarios; however, Permian Gondwana basin microfacies, with no open sea influence, have rarely been studied. In addition, in these basins there is a scarcity of micropaleontological studies and geochronological calibration, besides an absence of marine index fossils. In view of this, a comprehensive microfacies study for the unit is developed, with a large and representative surface and subsurface sample analysis of the Passa Dois Group, divided into three large geographic domains: north, central, and south of the Paraná Basin, Brazil. Thin sections distributed among the four units were analyzed with an emphasis on carbonate layers where the microfossils have a better chance to be recognized. The data were interpreted within a revised biochronostratigraphic framework and integrated with bivalves, macroflora, palynology, conchostracans, and vertebrates biozones. Microfacies analysis resulted in the recognition of 13 microfacies: four siliciclastic, eight carbonate, and one siliceous (chert). We observed a predominance of fine siliciclastic microfacies, rich in organic matter, in the Southern Domain; rudaceous carbonate microfacies in the Central Domain, with diverse allochemicals and the greater diversity of bioclasts; and an increase on siliciclastic sediments influx in the Northern Domain of the basin, where only the Irati and Teresina formations occur. A shortage of microfossils was observed in the South Domain, where the carbonate microfacies are less varied than those to the north. In the Central Domain, coarse-grained carbonates are present. Bivalves, ostracods, and sponge spicules are the main bioclasts on rudstones and grainstones from the Irati and Teresina formations, and have been interpreted as allochthonous to parautochthonous. The association of detrital and authigenic glauconite to bioaccumulations of sponge spicules is interpreted as episodes of marine transgression.
25812. 题目: Ammonia‐oxidizing archaea release a suite of organic compounds potentially fueling prokaryotic heterotrophy in the ocean
文章编号: N19072507
期刊: Environmental Microbiology
作者: Barbara Bayer, Roberta L. Hansman, Meriel J. Bittner, Beatriz E. Noriega‐Ortega, Jutta Niggemann, Thorsten Dittmar, Gerhard J. Herndl
更新时间: 2019-07-25
摘要: Ammonia‐oxidizing archaea (AOA) constitute a considerable fraction of microbial biomass in the global ocean, comprising 20‐40% of the ocean's prokaryotic plankton. However, it remains enigmatic to what extent these chemolithoautotrophic archaea release dissolved organic carbon (DOC). A combination of targeted and untargeted metabolomics was used to characterize the exometabolomes of three model AOA strains of the Nitrosopumilus genus. Our results indicate that marine AOA exude a suite of organic compounds with potentially varying reactivities, dominated by nitrogen‐containing compounds. A significant fraction of the released DOM consists of labile compounds, which typically limit prokaryotic heterotrophic activity in open ocean waters, including amino acids, thymidine, and B vitamins. Amino acid release rates corresponded with ammonia oxidation activity and the three Nitrosopumilus strains predominantly released hydrophobic amino acids, potentially as a result of passive diffusion. Despite the low contribution of DOC released by AOA (~0.08‐1.05%) to the heterotrophic prokaryotic carbon demand, the release of physiologically relevant metabolites could be crucial for microbes that are auxotrophic for some of these compounds, including members of the globally abundant and ubiquitous SAR11 clade. This article is protected by copyright. All rights reserved.
25813. 题目: Coupled steel slag and biochar amendment correlated with higher methanotrophic abundance and lower CH4 emission in subtropical paddies
文章编号: N19072506
期刊: Environmental Geochemistry and Health
作者: Miaoying Wang, Chun Wang, Xingfu Lan, Abbas Ali Abid, Xuping Xu, Ankit Singla, Jordi Sardans, Joan Llusià, Josep Peñuelas, Weiqi Wang
更新时间: 2019-07-25
摘要: Aerobic methanotrophs in paddies serve as methane (CH4) filters and thereby reduce CH4 emissions. Amending soil with waste products can mitigate CH4 emissions in crops, but little is known about the impacts of amendments with steel slag and biochar on the populations and activities of aerobic methanotrophs in rice cropland. We used real-time quantitative PCR detecting system and high-throughput sequencing to determine the effects of slag and biochar amendments on CH4 emission, abundance, and community structure of methanotrophs, and the relationships between soil properties and the abundance and community composition of methanotrophs during the rice growing season in both early and late paddies. Soil salinity and pH were significantly higher for an amendment with both slag and biochar than the control in both the early and late paddies, and pH was significantly higher for a slag amendment in the late paddy. Cumulative CH4 emission was lower for the slag and slag + biochar amendments than the control in early paddy by—34.1%. Methanotrophic abundance was three- and sixfold higher for the slag + biochar amendment than the control in the early and late paddies (p < 0.05), respectively. The abundance of different groups of methanotrophs varied among the treatments. The relative abundance of Methylosarcina was higher for the slag amendment than the control, and the relative abundance of Methylomonas was lower for biochar, and slag + biochar amendments than the control. The relative abundance of Methylocystis was higher for the slag and slag + biochar amendments than the control in the early paddy, and the relative abundance of Methylocystis was higher for the slag, biochar, and slag + biochar amendments in the late paddy. Univariate and multivariate analyses indicated that the higher abundance of methanotrophic bacteria for the slag and slag + biochar amendments was correlated with soil pH, salinity, soil organic carbon, and C/N ratio, and the relative abundances of Methylocystis, Methylomonas, and Methylosarcina were associated with the effective mitigation of CH4 emission in the paddies. A discriminant general analysis indicated that the total population of methanotrophs was larger for the slag + biochar amendment than the control, and that this effect was only weakly correlated with changes in the soil properties, demonstrating that this effect on the size and species composition of methanotrophic soil populations was mostly associated with a direct effect of the slag + biochar amendment.
25814. 题目: PLANT RESTORATION LEADS TO DIVERGENT SEQUESTRATION OF SOIL CARBON AND NITROGEN IN DIFFERENT FRACTIONS IN AN ARID DESERT REGION
文章编号: N19072505
期刊: Land Degradation & Development
作者: Xiao‐hong Jia, Yuan‐shou Li, Bo Wu, Qi Lu, Xin‐rong Li
更新时间: 2019-07-25
摘要: Soil organic carbon (OC) and nitrogen (N) associated with particle size fractions can be used as sensitive indicators to evaluate impacts of land use change on soil total OC (TOC) and total N (TN) pools. Aeolian sandy soils were collected from seven sites in the Tengger Desert, representing a 56‐year chronosequence of plant restoration at decadal intervals in an arid desert region. Bulk soils were separated into silt+clay (<53 μm), fine sand (53–100 μm), and coarse sand (>100 μm) fractions. TOC and TN concentrations of bulk soil and their levels associated with particle size fractions were analyzed. Results showed that plant restoration promoted C and N sequestration in both topsoil and subsoil layers over time, as indicated by elevated levels of OC and N associated with silt+clay and sand fractions. TOC and TN concentrations of 56‐year restored topsoil respectively increased by 31‐ and 43‐fold compared with the control (moving dunes); corresponding levels associated with silt+clay or coarse sand fraction respectively increased by more than 30‐ and 20‐fold, while less than 15‐fold increases were found in fine sand fraction. In the early stages of plant restoration, both C and N sequestration primarily resulted from finer particle size fractions. In the later stages, increased C sequestration was principally derived from coarse sand fraction, while N sequestration was mainly derived from silt+clay fraction. The results highlight that plant restoration stage and soil textural change are key factors leading to divergent soil C and N sequestration in the arid desert region.
25815. 题目: Response of bacterial communities in coastal mudflat saline soil to sewage sludge amendment
文章编号: N19072504
期刊: Applied Soil Ecology
作者: Yanchao Bai, Lijuan Mei, Wengang Zuo, Yang Zhang, Chuanhui Gu, Yuhua Shan, Jian Hu, Qigen Dai
更新时间: 2019-07-25
摘要: Microbial communities are of great importance in the development of saline soil fertility in coastal mudflats. However, the effects of sewage sludge use on the microbiome in saline soils of mudflats are unknown. This study aimed to investigate the response profile of bacterial communities in mudflat saline soil to sewage sludge amendment (SSA). Mudflat soil was treated once at the rates of 0, 30, 75, and 150 ton sewage sludge per hectare. Ryegrass, Sesbania, and Maize were successively planted and tilled. Approximately 3 years after the initial amendment, the Illumina Miseq sequencing of the 16S rRNA gene was performed to study bacterial community of mudflat soil. The results indicated that SSA significantly changed the mudflat saline soil bacterial community. A total of 37 phyla were found, dominated by Bacteroidetes, Proteobacteria, Chloroflexi, Actinobacteria, Acidobacteria, Planctomycetes, and Firmicutes. The SSA resulted in an increase in the comparable richness of Chloroflexi, Planctomycetes and Firmicutes, as well as a decrease in Proteobacteria. The canonical correspondence analysis indicated that the bacterial community structure was negatively affected by alkalinity or salinity, while positively affected by soil organic matter, and the N and P concentration in the saline soil. The bacterial community composition in the saline soil was altered by SSA. Lower salinity and alkalinity, and higher organic matter and nutrients favored microhabitats more suitable for bacteria.
25816. 题目: Water extractable organic matter (WEOM) as an indicator of granular activated carbon (GAC) bed life and water quality outcomes in drinking water treatment
文章编号: N19072503
期刊: Environmental Science: Water Research & Technology
作者: Jonathan Peter Ritson, Nigel Graham
更新时间: 2019-07-25
摘要: Granular activated carbon (GAC) is often used in drinking water treatment to remove dissolved organic carbon (DOC), taste and odour compounds, and organic micro-pollutants. As these chemicals are adsorbed onto the GAC surface, the area available for further adsorption decrease, meaning that the removal of target compounds decreases over time. Ascertaining the correct point to regenerate the GAC is a critical parameter in terms of both water quality performance and operational expenditure for the water company. Using a test case of a UK water treatment works with five GAC beds of varying age we show that current practices of using time-in-use are ineffective for optimal removal of DOC and disinfection by-product precursors. Our data show that assessment of the water extractable organic matter (WEOM) adsorbed onto the GAC can give an accurate indicator of both DOC removal (adjusted R2 =0.985, p=0.001, n=5) and reduction in trihalomethane formation (adjusted R2 =0.970, p=0.001, n=5). These results suggest that simple methods using equipment commonly available at treatment works could be adopted for rapid assessment of remaining GAC bed life.
25817. 题目: Introducing nitrogen-fixing tree species and mixing with Pinus massoniana alters and evenly distributes various chemical compositions of soil organic carbon in a planted forest in southern China
文章编号: N19072502
期刊: Forest Ecology and Management
作者: Hui Wang, Shirong Liu, Zhanchao Song, Yujing Yang, Jingxin Wang, Yeming You, Xiao Zhang, Zuomin Shi, You Nong, Angang Ming, Lihua Lu, Daoxiong Cai
更新时间: 2019-07-25
摘要: There are potential effects of converting a planted-forest type from conifer to broadleaf or mixed-species on soil organic carbon (SOC) chemical composition, and the quantity and distribution of various chemical compositions of SOC remain uncertain. An afforestation experiment with different tree species (Pinus massoniana, Erythrophleum fordii [N-fixing species], and mixed P. massoniana and E. fordii) was conducted in clear-cut sites of P. massoniana-planted forests in a subtropical region. Topsoil organic C quality and microbial diversity were assessed after eight years of afforestation. Referring to the species diversity index in the community, Pielou’s evenness index was used for estimating the evenness of distribution of various organic C compositions in the total organic C of soil, litter, and fine roots. The proportions of alkyl C and carbonyl C in SOC, as well as the alkyl C/O-alkyl C (A/O-A) ratios and the distributed evenness of the four main SOC chemical compositions were higher in the monospecific E. fordii and mixed-species-planted forests than in the monospecific P. massoniana-planted forest. Positive relationships of the A/O-A ratio and the evenness of distribution of various SOC chemical compositions in the litter as well as fine root C quality were observed. Microbial biomass C was positively correlated with the labile SOC (O-alkyl C). Multivariate analysis showed that the fine roots had a closer correlation with the chemical composition of SOC than the litter. These results highlight that introducing native N-fixing broadleaf tree species and mixing N-fixing species into conifer forests probably enhances the SOC chemical stability. It also minimizes the risk of C decomposition posed by any one soil organic matter (SOM) constituent having a huge impact during climate change through increasing the proportion of recalcitrant C components and even distribution of various SOM chemical compositions.
25818. 题目: Selective preservation of pyrogenic carbon across soil organic matter fractions and its influence on calculations of carbon mean residence times
文章编号: N19072501
期刊: Geoderma
作者: J.M. Lavallee, R.T. Conant, M.L. Haddix, R.F. Follett, M.I. Bird, E.A. Paul
更新时间: 2019-07-25
摘要: The long-standing perspective that recalcitrance of soil organic carbon (SOC) controls its stability and persistence has shifted to one in which physical inaccessibility of SOC to microorganisms plays a predominant role. This paradigm shift has been facilitated by analytical techniques that isolate SOC into physical fractions protected from decomposers by different mechanisms. The correlation between these fractions and SOC age has reinforced the emphasis of SOC inaccessibility. Pyrogenic C (PyC; also called charcoal or black carbon), which has been thermally altered by fire, is known to contain highly recalcitrant components that decompose very slowly and could represent an exception to this paradigm shift. We employed hydrogen pyrolysis to quantify the contribution of PyC to total SOC across soil fractions from three long-term agricultural experiments with land use conversions that caused reductions in SOC. We show that all soil fractions contain PyC and up to one-fifth of SOC in soil fractions considered to have low accessibility is comprised of PyC. Regardless of the soil fraction in which it was located, PyC was relatively unaffected by land use conversion compared to biogenic C (organic C not altered by fire), which suggests that selective preservation, rather than physical protection, is the dominant mechanism limiting PyC decomposition in these sites. We accounted for PyC in calculations of C mean residence times (MRTs) using differences in stable C isotope ratios between PyC and SOC. Though results varied by site and soil fraction, MRTs for biogenic C were generally shorter than for total SOC. Based on these results, PyC decomposition is controlled by a different mechanism than biogenic C, and this should be considered in studies of soil C dynamics. In addition, methods based on physical fractionation alone may place too great an emphasis on the role of inaccessibility for long-term SOC persistence.
25819. 题目: Spring flood induced shifts in Fe speciation and fate at increased salinity
文章编号: N19072419
期刊: Applied Geochemistry
作者: S.D. Herzog, S. Conrad, J. Ingri, P. Persson, E.S. Kritzberg
更新时间: 2019-07-24
摘要: Rivers have traditionally been viewed as negligible sources of iron (Fe) to marine waters, as most Fe gets lost during estuarine mixing. However, recent findings demonstrate that Fe from boreal rivers display a higher resistance towards salinity-induced aggregation, presumably due to stabilizing interactions with organic matter. Previous studies have shown that Fe (oxy)hydroxides are selectively removed by aggregation processes, and that organic Fe complexes are less affected by increasing salinity. It has been further proposed that Fe speciation varies in response to seasonal differences in hydrology. In this study X-ray absorption spectroscopy was used to determine the temporal variation in Fe speciation and the connection to Fe stability in response to increasing salinity in two boreal rivers (Kalix and Råne River), with the purpose to better understand the fate of riverine Fe export. Sampling was done from winter pre-flood, over the spring flood, to post-flood conditions (early April until mid June). In addition, parallel analyses for Fe speciation and isotope composition (δ56Fe relative to IRMM-14) were made on river samples, as well as salinity-induced aggregates and the fraction remaining in suspension, with the main objective to test if δ56Fe reflect the speciation of Fe.The contribution of organically complexed Fe increased during spring flood compared to the pre- and post-flood, as did Fe transport capacity. However, since Fe (oxy)hydroxides were dominating throughout the sampling period, the seasonal variability was small. Interestingly, salinity-induced aggregation experiments revealed that Fe (oxy)hydroxide, which dominated aggregates, displayed lower δ56Fe than in the river samples Fe, while organic Fe complexes in suspension had higher δ56Fe values. The seasonal variability in Fe isotope signature could not be simply linked to Fe speciation, but was probably also influenced by variation in source areas of Fe and processes along the flow-path that alter both Fe speciation and isotopic composition.
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25820. 题目: Soil productivity drivers in New Zealand planted forests
文章编号: N19072418
期刊: Forest Ecology and Management
作者: P.N. Beets, M.O. Kimberley, L.G. Garrett, T.S.H. Paul, A.L. Matson
更新时间: 2019-07-24
摘要: Soil fertility is one of a number of environmental and biotic drivers of Pinus radiata (D. Don) productivity in New Zealand’s planted forest estate. However, its importance as a driver of productivity at a national scale is uncertain. This paper uses New Zealand’s planted forest inventory plot network, which encompasses a wide range of planted forest environments in New Zealand, to quantify climatic, soil, and biotic drivers of P. radiata productivity. The P. radiata index of site productivity used in this study, the 300 Index, is defined as the mean annual increment in stem volume under bark at age 30 years, of stands growing at a final crop stocking of 300 trees per hectare, and thinned and pruned following a standardised regime. This site productivity index was found to be significantly related to climate (30 year normalised average temperature and rainfall), solar radiation (corrected for slope, horizon and aspect using a digital terrain model), tree health, and soil fertility variables. After adjusting for the effects of solar radiation, temperature and rainfall, site productivity across the New Zealand planted estate was found to be negatively related to the soil C/N ratio and positively related to the size of the soil organic matter pool. The size of the organic matter pool could be represented in the regression model by either the total carbon, total nitrogen, or organic phosphorus concentration of the topsoil. Of these three soil variables, soil total nitrogen was statistically the most significant variable in the model, when analysed in conjunction with the soil C/N ratio. Afforested pastoral farmland previously treated with phosphatic fertilisers to stimulate nitrogen-fixation by leguminous species had soils with a lower C/N ratio and a higher organic matter content. This contributed to an 18% gain in P. radiata productivity compared to land without an agricultural land use history. Having established a relationship between the P. radiata productivity index and climate and soil fertility key drivers, we also consider methods for improving regression model accuracy.