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24041. 题目: Predicting the decomposability of arctic tundra soil organic matter with mid infrared spectroscopy 文章编号: N18102501 期刊: Soil Biology and Biochemistry 作者: Roser Matamala, Julie D. Jastrow, Francisco J. Calderón, Chao Liang, Zhaosheng Fan, Gary J. Michaelson, Chien-Lu Ping 更新时间: 2018-10-25 摘要: Vast amounts of soil organic matter (SOM) have been preserved in arctic soils over millennia time scales due to the limiting effects of cold and wet environments on decomposer activity. With the increase in high latitude warming due to climate change, the potential decomposability of this SOM needs to be assessed. In this study, we investigated the capability of mid infrared (MIR) spectroscopy to quickly predict soil carbon and nitrogen concentrations and carbon (C) mineralized during short-term incubations of tundra soils. Active layer and upper permafrost soils collected from four tundra sites on the North Slope of Alaska were incubated at 1, 4, 8 and 16 °C for 60 days. All incubated soils were scanned to obtain the MIR spectra and analyzed for total organic carbon (TOC) and total nitrogen (TN) concentrations, and salt-extractable organic matter carbon (SEOM). Partial least square regression (PLSR) models, constructed using the MIR spectral data for all soils, were excellent predictors of soil TOC and TN concentrations and good predictors of mineralized C for these tundra soils. We explored whether PLSR models of mineralized C could be improved by splitting the soils into the groups defined by the influential factors and thresholds identified in a principal components analysis: (1) TOC > 10%, (2) TOC < 10%, (3) TN < 0.6%, (4) TN > 0.6%, (5) acidic tundra, and (6) non-acidic tundra. The best PLSR mineralization models were found for soils with TOC <10% and TN < 0.6%. Analysis of the PLSR loadings and beta coefficients from these models indicated a small number of influential spectral bands. These bands were associated with clay content, phenolics, aliphatics, silicates, carboxylic acids, and amides. Our results suggest that MIR could serve as a useful tool for quickly and reasonably estimating the initial decomposability of tundra soils, particularly for mineral soils and the mixed organic-mineral horizons of cryoturbated soils. |
24042. 题目: Negative Impacts of Biochars on Urease Activity: High pH, Heavy Metals, Polycyclic Aromatic Hydrocarbons, or Free Radicals? 文章编号: N18102415 期刊: Environmental Science & Technology 作者: Yang Liu, Qunying Dai, Xiuqi Jin, Xudong Dong, Juan Peng, Min Wu, Ni Liang, Bo Pan, Baoshan Xing 更新时间: 2018-10-24 摘要: Although biochars show promise for soil remediation, their negative impacts have not been systematically assessed. This study investigated the effects of corn cob biochars on urease-mediated urea hydrolysis and attempted to determine the mechanisms underlying those effects. The results showed that biochars inhibited urease activity (indicated by the NH4+ generation). Released heavy metals and polyaromatic hydrocarbons explained the 20% inhibition of urease activity in biochar supernatants (200 °C) but could not explain the 70% inhibition in particle systems (400 °C). The levels of protein carbonyl and nitrotyrosine, common oxidative damagers of urease, were high in particle systems but very low in biochar supernatants. The electron paramagnetic resonance signal intensity reached its highest level in the 400 °C biochar and decreased in the 500 °C biochar, possibly due to the decomposition of organic molecules. The observed inhibition of urease activity may be the result of oxidative reactions with free radicals on the biochar surface or oxidative reactions with reactive oxygen species promoted by free radicals. We suggest that these potential hazards be evaluated further to gauge the relevance of these findings to field conditions and to assist in the development of safe and sustainable application schemes for biochars. 图文摘要:
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24043. 题目: New methods for assessing electron storage capacity and redox reversibility of biochar 文章编号: N18102414 期刊: Chemosphere 作者: Danhui Xin, Minghan Xian, Pei C. Chiu 更新时间: 2018-10-24 摘要: Black carbon such as biochar has been shown to support microbial redox transformation by accepting and/or donating electrons. Electron storage capacity (ESC) is an important property that determines the capacity of a biochar to mediate redox processes in natural and engineered systems. However, it remained unclear whether a biochar's ESC is constant and reversible and if so to what extent, over what redox potential range ESC is distributed, and what fraction of the ESC is microbially accessible. In this study, we developed chemical methods that employed combinations of reductants and oxidants of different potentials – Ti(III) citrate, ferricyanide, dithionite, and dissolved O2 – to measure the ESC of Soil Reef biochar, a wood-derived biochar that can serve as an electron donor or acceptor for Geobacter metallireducens. For a given oxidant–reductant pair, the ESC obtained over multiple redox cycles was constant and fully reversible, though lower than that of the virgin biochar. Pore diffusion within biochar particles was rate-limiting and controlled the timescale for redox equilibrium. Results suggest that redox-facile functional groups in biochar were distributed over a broad range of potentials. The ESC measured using dithionite indicates approximately 22% of the biochar's reversible ESC was accessible to G. metallireducens. We propose that reversible ESC may be regarded as a constant and quantifiable property of black carbon. 图文摘要:
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24044. 题目: Methylmercury in environmental compartments of a hydroelectric reservoir in the Western Amazon, Brazil 文章编号: N18102413 期刊: Chemosphere 作者: Inacio A. Pestana, Wanderley R. Bastos, Marcelo G. Almeida, Marilia H. Mussy, Cristina MM. Souza 更新时间: 2018-10-24 摘要: Damming rivers to generate electricity creates a lentic environment that favors methylmercury (MeHg) formation. Reservoirs in the Amazon are critical environments for MeHg formation, considering its old soils and the use of Hg in gold mining in the region. The objective of this study was to evaluate MeHg accumulation in three environmental compartments (aquatic macrophytes, suspended particulate matter (SPM) and sediment) of the Samuel reservoir (Western Amazon, Brazil), during the low water, ebb and high water hydrological periods, characterizing the dry season, the end of the rainy season and the rainy season, respectively. MeHg concentrations were determined through GC-AFS. The aquatic macrophytes presented higher %MeHg in their roots (up to 12%) compared to their other tissues. This ratio was 1.7 and 5.9 times higher than those observed for SPM and the sediment, but MeHg concentrations were the lowest (0.5–4.5 ng g−1) among the three environmental compartments. Contrary, the highest MeHg concentration was observed in SPM (104 ng g−1) during the low water period. The MeHg concentration in the sediment profile decreased with increasing depth (0.93–0.48 ng g−1) and with decreasing organic matter lability (increasing C:N ratio). In the SPM, on the other hand, MeHg concentration showed a positive association with increasing C:N ratio. We conclude that MeHg dynamics in the SPM are associated with the hydrological periods, with peaks during the low water period. The organic matter lability of the sediments is more limiting to the production of MeHg than the total Hg concentrations. |
24045. 题目: Organic matter in temperate cultivated floodplain soils: Light fractions highly contribute to subsoil organic carbon 文章编号: N18102412 期刊: Geoderma 作者: Stefanie Mayer, Angelika Kölbl, Jörg Völkel, Ingrid Kögel-Knabner 更新时间: 2018-10-24 摘要: Floodplain soils are important reservoirs of organic carbon (OC) in the terrestrial carbon cycle. Few rivers and floodplains in the world and particularly in central Europe are in a natural state. They are regulated, stabilised from erosion behind artificial levees, drained and used for agriculture. Fluvisols store high amounts of OC from the topsoil to the subsoil, but little is known about the soil organic matter (SOM) quality and its vulnerability to decomposition. In this study, two regulated floodplains originating from different parent materials under grassland use in Southern Germany (Alpine Foreland and the Bavarian Forest) were sampled and analysed for the quantity and quality of inherent SOM in the topsoil and two subsoil levels. We characterised bulk soil (pH, texture, inorganic carbon and total nitrogen) and applied a combined density and size fractionation scheme to obtain six fractions. The chemical composition of the fractions was further determined using solid-state 13C NMR spectroscopy (SOM composition), as well as X-ray diffraction (clay mineralogy) and N2-BET (specific surface area (SSA)). Contributions of light fractions and especially of occluded particulate organic matter (oPOMfine) to the total OC were remarkably high in the subsoils. Organo-mineral associations (OMFfine) highly contributed to total OC at both sites but only in the topsoils. The highest OC concentrations of OMFfine were found in calcareous parent material, which shows that polyvalent cations promote OC storage. However, the inter-site as well as intra-site heterogeneity of oPOMfine and OMFfine OC contribution was highly variable. In the Bavarian Forest, oPOMfine was enriched in lipids in the subsoil. This was most probably due to a limited supply of oxygen in the aggregates through fluctuating groundwater levels that retarded decomposition and selectively preserved aliphatic compounds. In the Alpine Foreland, soil biota had mixed fresh SOM into the subsoil. There, oPOMfine contained all the functional C-groups, particularly carbohydrates. A changing global climate jeopardises OC reservoirs in floodplains, due to increased flooding and associated river bank erosion. Such disturbances not only cause losses of productive land but also release OC stored in light fractions that could be oxidised to CO2, depending on its chemical composition, thus adding to global warming. 图文摘要:
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24046. 题目: High-efficiency removal of Pb(II) and humate by a CeO2–MoS2 hybrid magnetic biochar 文章编号: N18102411 期刊: Bioresource Technology 作者: Ronghua Li, Hongxia Deng, Xiaofeng Zhang, Jim J. Wang, Mukesh Kumar Awasthi, Quan Wang, Ran Xiao, Baoyue Zhou, Juan Du, Zengqiang Zhang 更新时间: 2018-10-24 摘要: This work prepares a novel CeO2–MoS2 hybrid magnetic biochar (CMMB) for the adsorptive removal of Pb(II) and humate from aqueous solution. The CMMB was evaluated against magnetic biochar (MB). The results showed that CMMB exhibited strong magnetic separation ability. Hybridization of CMMB greatly improved Pb(II) and humate removal compared to MB, with>99% Pb(II) and humate removed within 6 h. Pb(II) and humate removal capacities of CMMB were 263.6 mg/g and 218.0 mg/g, respectively, with negligible influence of ion strength in the range of 0–0.1 mol/L NaNO3. Pb(II) removal mechanism involved predominately with electrostatic attraction, Cπ–Pb(II) bond interaction, and surface adsorption and complexation combined processes; while pore-filling, partition effect and π–π interaction contributed to the adsorption of humate. Overall, the introduction of graphene-like MoS2 materials into biochar benefits both of the biomass resources recovery and environmental protection. |
24047. 题目: Linking microbial respiratory activity with phospholipid fatty acid of biofilm from full-scale bioreactors 文章编号: N18102410 期刊: Bioresource Technology 作者: Hui Huang, Xuan Fan, Chong Peng, Jinju Geng, Lili Ding, Xuxiang Zhang, Hongqiang Ren 更新时间: 2018-10-24 摘要: Deficiency of researches on biotic community-driven biofilm activity makes biofilm regulation lack of quantitative response for decades. Based on three full-scale aerobic bioreactors in wastewater treatment plants, this study for the first time linked microbial respiratory activity with phospholipid fatty acid (PLFA) of biofilm developed on fixed and suspended carriers. Results showed that C16:00, C18:00, C16:1, ω7c, C18:1, ω7c, C12:00 and C18:1ω9c were top six biomarkers of PLFA among different sources of samples and Gram-negative bacteria (G-) was more abundant than Gram-positive bacteria (G+) with average G-/G+ of 2.98. It’s interesting to find defective revealing of PLFA-based biofilm activity by specific oxygen uptake rate (SOUR). Further modeling indicated that C16:00 achieved the optimal quantitative response to STOUR with the best model of composite, growth, or exponential curve (R2=0.416, p = 0.005). This research was promising to provide important reference for biofilm regulation and accurate control of biofilm-based process. 图文摘要:
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24048. 题目: Iron complexation by phenolic ligands in seawater 文章编号: N18102409 期刊: Chemical Geology 作者: Aridane G. González, M. Isabel Cadena-Aizaga, Geraldine Sarthou, Melchor González-Dávila, J.M. Santana-Casiano 更新时间: 2018-10-24 摘要: Iron is an essential micronutrient for phytoplankton and can limit primary production in the ocean. Fe chemistry is highly controlled by its interaction with organic complexes (>99%). It is still unknown which organic compounds produced by cells have the ability to bind Fe. Within the pool of organic ligands, polyphenols are known to be exudated by marine diatoms and, in this study, the role of three polyphenols ((±) – catechin, sinapic acid and gallic acid) was studied in terms of dissolved Fe complexation via kinetic and titration approaches, and also their role as a source of Fe(II) in seawater. The results demonstrated that these three polyphenols are weak L2-type Fe-binding ligands according to the conditional stability constant, computed by using the kinetic approach (log K′Fe′L = 8.86–9.2), where the formation rate constant (kf) was 3.1·105–4.2·105 M−1 s−1 and the dissociation rate constant (kd) was 2.43·10−4–4.4·10−4 s−1. The conditional stability was also computed from the titration approach with log K′Fe′L from 8.6 to 9.5. These studied ligands also regenerated Fe(II) in seawater from 0.05% to 11.92%. The results obtained in this study suggest that polyphenols increase the persistence of dissolved Fe and should be considered as an important Fe-binding ligands in seawater to better understand the global biogeochemical cycles.This article is part of a special issue entitled: “ConwayGEOTRACES” - edited by Catherine Chauvel. |
24049. 题目: Evaluating ultraviolet (UV) based photochemistry in optically complex coastal waters using the Hyperspectral Imager for the Coastal Ocean (HICO) 文章编号: N18102408 期刊: Estuarine, Coastal and Shelf Science 作者: Fang Cao, Deepak R. Mishra, John F. Schalles, William L. Miller 更新时间: 2018-10-24 摘要: Knowledge of light partitioning into different optically active constituents, particularly chromophoric dissolved organic matter (CDOM) in the ultraviolet (UV) is indispensable for understanding UV dependent biogeochemical issues including photochemical processes in optically complex waters. Herein a new approach is presented to investigate photochemistry by blending two ocean color algorithms, namely the composite SeaUV (Cao et al., 2014) and the SeaCDOM (Cao and Miller, 2014) algorithms, and applying them to visible remote sensing reflectance (Rrs) measured using the Hyperspectral Imager for the Coastal Ocean (HICO). As illustrated using photochemical carbon monoxide (CO) production from CDOM, this model approach allows high resolution examination of UV optical details with estimates of both depth-specific and depth-integrated photoproduction rates in a dynamic estuarine/coastal environment. Decoupled retrievals of inherent and apparent optical properties (i.e. diffuse attenuation coefficient (Kd) and CDOM absorption coefficient (ag)) using two distinct ocean color algorithms over the entire UV spectrum allow a synoptically dynamic view of CDOM's contribution to light attenuation (ag/Kd). This provides new potential to probe UV processes in complex coastal waters on regional as well as global scales using remote sensing of ocean color. |
24050. 题目: Soil micro-food web interactions and rhizosphere priming effect 文章编号: N18102407 期刊: Plant and Soil 作者: Xinchang Kou, Tongqing Su, Ningning Ma, Qi Li, Peng Wang, Zhengfang Wu, Wenju Liang, Weixin Cheng 更新时间: 2018-10-24 摘要: Background and aims: The rhizosphere priming effect (RPE) is the stimulation or suppression of soil organic matter decomposition by living roots and associated rhizosphere organisms. The RPE is pivotal in regulating biogeochemical cycles in terrestrial ecosystems. However, biological mechanisms, especially soil micro-food web interactions, behind the RPE remain largely unknown. Methods: We quantified the RPE of soybean and cottonwood at three growth stages using a natural 13C tracer method, measured soil microbial and nematode community composition, and investigated their relations with the RPE. Results: The magnitude of the RPE varied widely at different growth stages. Soybean produced a greater cumulative RPE than cottonwood. The plant species effect was also observed in the bacterial PLFA with higher values found in the soybean treatment. Mantel test analysis suggested that the variations in microbial community were closely related with the RPE, soil and plant characteristics. The nematode community affected the RPE indirectly through altering the structure of the microbial community. Conclusions: We demonstrated that the RPE was connected with interactions of soil micro-food webs. This connection indicates that soil micro-food web interactions in the rhizosphere may either regulate microbial turnover and/or microbial community composition, subsequently modulating the RPE. |
24051. 题目: Shooting range contamination: mobility and transport of lead (Pb), copper (Cu) and antimony (Sb) in contaminated peatland 文章编号: N18102406 期刊: Journal of Soils and Sediments 作者: Gudny Okkenhaug, Andreas Botnen Smebye, Thomas Pabst, Carl Einar Amundsen, Hilmar Sævarsson, Gijs D. Breedveld 更新时间: 2018-10-24 摘要: Purpose: Small arm shooting ranges located in peatland areas are gathering increased attention due to severe metal and antimony (Sb) contamination and challenging conditions for remediation. The goal of the present study was to gain further understanding of the distribution, binding and transport of lead (Pb), copper (Cu) and Sb in peatland contaminated by small arm shooting range activities. Materials and methods: A field experiment was carried out at a recently closed shooting range facility in Norway, including (i) peat soil sampling for various selective extractions (water, chemical extractions, extractions by diffusive gradients in thin films, DGT), (ii) establishing groundwater wells for groundwater sampling and monitoring of groundwater level and (iii) sampling of water and sediments in surface water. The results from groundwater monitoring were used to carry out hydrogeological numerical simulations using Seep/W and CTran/W. These models were used to evaluate the residence time of the contaminants in the peatland. Results and discussion: Increased metal concentrations were observed in the top layer of the peatland, indicating low vertical transport. Groundwater revealed high concentrations of Pb (22 ± 5 μg/L), Cu (16 ± 6 μg/L) and Sb (11 ± 2 μg/L), the dominating contaminant source to the downstream surface water. Hydrogeological modelling indicated that transport mainly happened in the upper peat layer, as a result of a higher hydraulic conductivity close to the surface and a high groundwater table. Pb (6.9 ± 0.1 μg/L), Cu (24.0 ± 0.0 μg/L) and Sb (7.4 ± 0.1 μg/L) concentrations in the stream samples confirmed the spreading of contaminants at levels toxic to aquatic organisms. Pb and Cu were most likely associated with dissolved organic carbon (DOC), whereas Sb showed no correlation with DOC. Conclusions: The elements contaminating the peatland may leak to the nearby water course over a long-term period. Copper showed the highest concentration in the stream water despite considerably higher levels of Pb in the peat soil. Strong complexation of Cu to dissolved organic matter might explain this observation. Only a little fraction of the contaminants is transported in a particulate form, and therefore are increased sedimentation measures not considered as viable remediation option. |
24052. 题目: Positive effects of apple branch biochar on wheat yield only appear at a low application rate, regardless of nitrogen and water conditions 文章编号: N18102405 期刊: Journal of Soils and Sediments 作者: Shuailin Li, Zhouping Shangguan 更新时间: 2018-10-24 摘要: Purpose: The agriculture industry is under intense pressure to produce more food with a lower environmental impact, while also mitigating climate change. Biochar has the potential to improve food security while improving soil fertility and sequestering carbon. The aim of our research was to evaluate the effects of apple branch biochar on wheat yield and soil nutrients under different nitrogen (N) and water conditions. Materials and methods: Durum wheat was grown for nearly 6 months in pots with silt clay soil supplemented with apple branch biochar. The biochar was applied at five rates (0, 1, 2, 4, and 6% w/w; B0, B1, B2, B3, and B4), and N fertilizer was applied at three rates (0, 0.2, and 0.4 g kg−1; N0, N1, and N2). From the jointing to maturation stages, the soil water content was controlled at two rates to simulate sufficient water and drought conditions (75 and 45% of field capacity; W1 and W2). After harvest, we investigated grain yield and soil nutrient status. Results and discussion: The application of biochar alone had a positive effect on wheat production and soil nutrients, especially under sufficient water conditions. Compared with the addition of N fertilizer alone, the addition of biochar at B1 and B2 combined with N fertilizer under sufficient water conditions increased the crop yield by 7.40 to 12.00%, whereas this was not the case under drought stress. Furthermore, regardless of water conditions, compared with N fertilizer application alone, a high rate of biochar application (B3 and B4) led to a significant decrease in the grain yield of approximately 6.25–21.83%. Biochar had strong effects on soil nutrients, with NO3− and available phosphorus contents and the C:N ratio exerting the greatest effects on wheat yield. Conclusions: The effects of biochar on wheat production and soil nutrients varied with the biochar application rate, N fertilizer application rate, and water conditions. Drought stress weakened or offset the positive effect of biochar on crop production, especially under the high-N level (N2) conditions. The optimum application combination was 1% (or possibly even less) apple branch biochar (B1) and moderate N fertilizer (N1). |
24053. 题目: Land-use change affects stocks and stoichiometric ratios of soil carbon, nitrogen, and phosphorus in a typical agro-pastoral region of northwest China 文章编号: N18102404 期刊: Journal of Soils and Sediments 作者: Xiang Liu, Lanhai Li, Quan Wang, Shuyong Mu 更新时间: 2018-10-24 摘要: Purpose: The impacts of land-use change on dynamics of soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) in the subsoil (> 30 cm) are poorly understood. This study aims to investigate whether the effects of land-use change on stocks and stoichiometric ratios (RCN, RCP, and RNP) of SOC, TN, and TP can be different between topsoil (0–30 cm) and subsoil (30–60 cm) in the Ili River Valley, northwest China. Materials and methods: Soil samples (0–10, 10–20, 20–30, 30–40, 40–50, and 50–60 cm) were collected from a pasture (PT), a 27-year-old cropland (CL) converted from PT, and a 13-year-old poplar (Populus tomentosa Carr.) plantation (PP) converted from CL. SOC, TN, and TP concentrations and soil bulk density were determined to calculate stocks and stoichiometric ratios (molar ratios) of SOC, TN, and TP. Results and discussion: Conversion from PT to CL led to substantial losses in SOC, TN, and TP pools in both topsoil and subsoil, and the reduction rates in subsoil (13.8–24.7%) were higher than those in topsoil (8.5–17.3%), indicating that C, N, and P pools in subsoil could also be depleted by cultivation. Similar to topsoil, significant increases in SOC, TN, and TP stocks were detected after afforestation on CL in subsoil, although the increase rates (31.2–56.2%) were lower than those in topsoil (47.8–69.1%). Soil pH and electrical conductivity (EC), which generally increased after conversion from PT to CL while decreased after CL afforestation, showed significant negative correlations with SOC, TN, and TP, suggesting that cultivation might lead to soil degradation, whereas afforestation contributed to soil restoration in this area. Significant changes in C:N:P ratios in topsoil were only detected for RNP after conversion from CL to PP. By contrast, land-use change significantly altered both RCN and RNP in the subsoil, demonstrating that the impacts of land-use change on RCN and RNP were different between topsoil and subsoil. The significant relationship between soil EC and RNP suggested that RNP might be a useful indicator of soil salinization. Conclusions: Stocks of SOC, TN, and TP as well as RCN and RNP in subsoil showed different responses to land-use change compared to those in topsoil in this typical agro-pastoral region. Therefore, it is suggested that the effects of land-use change on dynamics of SOC, TN, and TP in subsoil should also be evaluated to better understand the role of land-use change in global biogeochemical cycles. |
24054. 题目: Effect of biochar amendment on water infiltration in a coastal saline soil 文章编号: N18102403 期刊: Journal of Soils and Sediments 作者: Junna Sun, Runya Yang, Wenxue Li, Yinghua Pan, Mengzhu Zheng, Zhenhua Zhang 更新时间: 2018-10-24 摘要: Purpose: Increasing data have shown that biochar amendment can improve soil fertility and crop production, but there is little knowledge about whether biochar amendment can improve water infiltration in saline soils. We hypothesized that biochar amendment could promote water infiltration in saline soil. The aims of this study were to evaluate the effects of biochar amendment on water infiltration and find the suitable amendment rate and particle size of biochar as a saline soil conditioner. Materials and methods: We measured water infiltration parameters in a coastal saline soil (silty loam) amended with non-sieved biochar at different rates (0.5, 1, 2, 5, and 10%, w/w) or sieved biochar of different particle sizes (≤ 0.25 mm, 0.25–1 mm, and 1–2 mm) at 1 and 10% (w/w). Results and discussion: Compared with the control, amending non-sieved biochar at 10% significantly decreased water infiltration into the saline soil (P < 0.05). In contrast, sieved biochar of ≤ 0.25 mm significantly improved water infiltration capacity, irrespective of the amendment rate. Sieved biochar of 1–2 mm was less effective to improve soil porosity and when amended at 10%, it even reduced the water infiltration capacity. The Philip model (R2 = 0.983–0.999) had a better goodness-of-fit than the Green-Ampt model (R2 = 0.506–0.923) for simulation of cumulative infiltration. Conclusions: Amending biochar sieved to a small particle size improved water infiltration capacity of the coastal saline soil compared with non-sieved biochar irrespective of the amendment rate. This study contributes toward improving the hydrological property of coastal saline soil and rationally applying biochar in the field. |
24055. 题目: Combined effects of cropping types and simulated extreme precipitation on the community composition and diversity of soil macrofauna in the eastern Qinghai-Tibet Plateau 文章编号: N18102402 期刊: Journal of Soils and Sediments 作者: Sizhong Wang, Kaiwen Pan, Akash Tariq, Lin Zhang, Xiaoming Sun, Zilong Li, Feng Sun, Qinli Xiong, Dagang Song, Olusanya Abiodun Olatunji 更新时间: 2018-10-24 摘要: Purpose: Extreme precipitation as global change greatly affects above- and below-ground biodiversity. Soil macrofauna play a key role in the agroforestry ecosystem processes. Extreme precipitation might negatively impact soil macrofauna by changing soil water content. Particularly, whether cropping types are beneficial to alleviate response of soil macrofauna to extreme precipitation remains unexplored. Materials and methods: Effects of simulated extreme precipitation of 1 month on soil macrofauna were studied under Chinese prickly ash (Zanthoxylum bungeanum) intercropped with soybean (Glycine max), Chinese prickly ash intercropped with sweet pepper (Capsicum annuum), and Chinese prickly ash monoculture. Soil macrofauna and soil samples were collected in three soil depths (0–10, 10–20, and 20–30 cm) per plot. The abundance, diversity, and vertical distribution of soil macrofauna were analyzed for each sample at genus and trophic level. Each sieved soil sample was analyzed for soil water content, soil nitrate nitrogen (NO3−–N), ammonium nitrogen (NH4+–N) and organic matter. Descriptive statistics and significance tests on raw data were carried out using the SPSS 16.0 software at P < 0.05. Results and discussion: A total of 502 soil macrofauna individuals were observed, and belonged to 14 genera, and consisted mainly of earthworms, arthropods. The richness, density, and biomass, as well as vertical distribution of total soil macrofauna were unaffected by extreme precipitation. Only Eisenia density and biomass were significantly decreased by extreme precipitation. The plots intercropped with soybean had higher density, biomass, and richness than the plots intercropped with sweet pepper and prickly ash monoculture. Cropping types significantly influenced density of total soil macrofauna under control condition but not extreme precipitation treatment. The abundance of total soil macrofauna was significantly and positively related to soil NH4+–N, total soil inorganic N, and soil organic matter. Conclusions: Our results suggest that the impacts of cropping types rather than extreme precipitation on soil macrofauna abundance, diversity, and vertical distribution are significant. However, extreme precipitation changes the response of soil macrofauna to cropping types. |
24056. 题目: Characteristics of hydrophobic and hydrophilic acid fractions in drainage waters of undisturbed soil lysimeters 文章编号: N18102401 期刊: Journal of Soils and Sediments 作者: Guixue Song, Etelvino H. Novotny, Karl G. Richards, Michael H. B. Hayes 更新时间: 2018-10-24 摘要: Purpose: Dissolved organic matter (DOM), a heterogeneous mixture of low concentrations of organic matter draining from soils, plays a significant role in soil C cycling and in nutrient and pollutant transport. DOM from undisturbed soil profiles has rarely been studied. Hydrophobic acids (Ho) and hydrophilic acids (Hi), the major components of DOM, were recovered, using XAD-8 and XAD-4 resins in series, from waters draining in winter and in spring periods from well-drained and poorly drained Irish grassland soil profiles in lysimeters. Materials and methods: Waters were collected from 45 soil undisturbed lysimeters at the Teagasc Research Centre, Johnstown Castle, Wexford, Ireland. Four Irish representative soils had been collected as undisturbed 1.0-m-deep monoliths, transported to the experiment site and arranged randomly in an experimental facility. Water collections were carried out in winter and spring periods. The DOM was isolated and fractionated using an XAD-8 and XAD-4 resins in-tandem procedure, and hydrophobic acids (Ho) and hydrophilic acids (Hi) were isolated. Results and discussion: The amounts of DOM recovered in the winter period were much greater than those in the spring period, and the soil types had only minor influences on the DOM concentrations recovered. The Ho and Hi fraction contents ranged from 62 to 90 and 10 to 28%, respectively, of the total DOM content extracted. The Hi acids were most enriched in 13C, and considered to reflect greater microbial inputs. The neutral sugar (NS) contents for the Ho and Hi fractions were in the range of 15 to 52 μg mg−1, with the Hi fraction most enriched. The amino acids (AAs) for the Ho and Hi fractions varied from 0.6 to 2.4%, and the total AAs and NS of the Ho acids were well correlated. The DOM fractions from the drainage waters contained much less AAs and NS than the corresponding fractions in the parent soils. The solid- and liquid-state NMR data indicated organic structures with low aromaticity, significant amounts of carbohydrate and with lesser amounts of peptide structures, and with long-chain methylene (CH2)n and methine (-CH-) groups. Conclusions: The application of a variety of wet chemistry and of spectroscopy procedures has given a more in-depth awareness of the compositions of the DOM in the drainage waters from four different soils in 1.0-m-deep lysimeter arrangements. Based on wet chemistry analyses, and FTIR and liquid- and solid-state NMR spectrometry, it is clear that there are some differences between the compositions of the DOM fractions recovered. Alkyl functionalities dominated the structures. These included significant amounts or O-alkyl (predominantly carbohydrate), and with lesser (and variable amounts in the different fractions) aromatic structures (to which aromatic amino acid components were considered to be significant contributors), and with no evidence for lignin-derived structures The results suggest that, during residence in the soil solution, microbiological processes transform the SOM components released into products that are greatly different from their materials of origin in the SOM. |
24057. 题目: Toxicity of silver nanoparticles to green algae M. aeruginosa and alleviation by organic matter 文章编号: N18102307 期刊: Environmental Monitoring and Assessment 作者: Li Xiang, Juan Fang, Hua Cheng 更新时间: 2018-10-23 摘要: Silver nanoparticles (AgNPs) have been increasingly used in a wide range of consumer products over the last decade. The release of AgNPs into aquatic ecosystems raises concerns about their safety and environmental toxicity, which have been the subject of recent studies. Herein, we assess the toxicity of AgNPs to the common algae Microcystis. aeruginosa. A toxicological response by M. aeruginosa was exhibited at an early stage of exposure to AgNPs, which were also toxic to its growth, photosynthetic, and membrane systems. The attachment of AgNPs to microalgae is likely the main mechanism by which it damages cell membranes. Dissolved Ag ions, originating from internalized AgNPs, seem to directly target the photosynthetic system. We also found that several humus-related indicators of water quality (HIX and β/α) were related to reduced AgNPs toxicity. |
24058. 题目: Extreme 13C-depletions and organic sulfur content argue for S-fueled anaerobic methane oxidation in 2.72 Ga old stromatolites 文章编号: N18102306 期刊: Geochimica et Cosmochimica Acta 作者: Kevin Lepot, Kenneth H. Williford, Pascal Philippot, Christophe Thomazo, Takayuki Ushikubo, Kouki Kitajima, Smaïl Mostefaoui, John W. Valley 更新时间: 2018-10-23 摘要: The extreme 13C-depletions recorded in Neoarchean organic matter (OM) have commonly been interpreted as markers of methanotrophy. This methane oxidation metabolism could have been performed using oxidants such as dioxygen, sulfate, nitrite/nitrate, and/or Fe3+- and Mn4+-minerals. Acetogenesis using acetyl-CoA metabolism may produce similar 13C-depletions. We investigated δ13C and S/C values of OM in 2.72 Ga old lacustrine stromatolites of the Tumbiana Formation (Australia) using Secondary Ion Mass Spectrometry (SIMS), coupled with X-ray spectroscopy. Type-A OM is embedded in quartz and/or chlorite. We show that mixtures of chlorite bias negatively the δ13Corg of associated OM measured by SIMS, likely through recombination of hydrogen from chlorite with carbon from OM during analysis. Type-A OM, associated with quartz or interleaved with chlorites (but remote enough to avoid H-recombination), displays δ13Corg between –56.1 and –50.6 ‰ VPDB (mean: –53.5 ‰, SD ±1.8 ‰). The intimate association of Type-A OM with Fe-rich chlorite and its main occurrence in pyritic layers coupled with 13C-depletions is most parsimoniously interpreted as anaerobic methanotrophy using Fe3+-minerals and/or oxidized S. Type-B OM comprises <2-µm organic globules embedded in calcite. A mass balance correction using the δ13C values measured on Type-B globules mixed with calcite and those measured on pure calcite yielded corrected δ13C∗org values for the globules ranging between –65.2 and –52.5 ‰ (mean –58.8 ‰, SD ±3.6 ‰). In a context where Fe and S reduction could outcompete acetogenesis for a fraction of any available H2, these extremely low δ13Corg values are difficult to explain with chemoautotrophic acetogenesis. Atomic S/C ratios in Type-B globules reach up to 0.042, i.e. up to tenfold the values (0.003–0.004) in Type A-OM. These organic S concentrations, combined with the extremely low δ13C∗org values, support anaerobic oxidation of methane coupled to sulfur oxidation. Finally, Type-C OM, interpreted as migrated pyrobitumen nodules, displays δ13Corg of –48 to –39.1 ‰. The most extreme low-δ13Corg values of the Precambrian are thus best interpreted as the result of lacustrine methanotrophy fueled by oxidized S and/or Fe species, which likely derived from oxygenic and/or anoxygenic photosynthesis. Photosynthesis, followed by methanogenesis and methanotrophy may have been important in lakes at a time of supercontinent growth and eruption of large subaerial igneous provinces. In this context, anaerobic methanotrophy could have played a part in regulating atmospheric methane. |
24059. 题目: Enhancement of coal waste slurry flocculation by CTAB combined with bioflocculant produced by Azotobacter chroococcum 文章编号: N18102305 期刊: Separation and Purification Technology 作者: Zhichao Yang, Shengyu Liu, Wenbing Zhang, Quanbao Wen, Yongjie Guo 更新时间: 2018-10-23 摘要: A bioflocculant produced by Azotobacter chroococcum, a natural polymer containing sugar and protein, can be used to flocculate coal waste slurry, but electrostatic repulsion impacts the flocculation of quartz attached to the solid coal particles. In this work, cetyltrimethylammonium bromide (CTAB) combined with this bioflocculant were used to flocculate coal waste slurry. The adsorption and zeta potential of CTAB on quartz, kaolinite, and organic matter were investigated in aqueous media. The results show that the data for CTAB adsorption fit the typical Langmuir adsorption model, and that the CTAB adsorption level is higher in an alkaline medium than in an acidic medium. The electrostatic interaction and formation of π-complexes contributed to the adsorption of CTAB on minerals and organic matter. Zeta potential measurements demonstrated that the point of zero charge values shifted to higher pH values after CTAB adsorption on mineral and organic matter surfaces. Furthermore, the behavior of the bioflocculant with the addition of CTAB was investigated to determine the effect of CTAB on the flocculation of coal waste slurry; quartz, kaolinite, and organic matter were used for comparison. Flocculation tests indicated that the optimum CTAB dosage for obtaining higher flocculation rates and clearer suspension of organic matter, quartz, and kaolinite was 50, 100, and 40 mg/L, respectively. A higher flocculation rate and clearer suspension of quartz were obtained in a very acidic medium, while organic matter suspension continued to increase in the pH range of 2.2–6.2 and remained almost constant in an alkaline medium. In addition, there were no significant changes in the flocculation rate or turbidity of kaolinite with an increase in pH. CTAB exhibited significant enhancement in terms of flocculation of coal waste slurry when the bioflocculant was used as a flocculant. Finally, surface tension measurements were taken to confirm the interaction between the bioflocculant and CTAB. The results show that CTAB could bind to the bioflocculant and form complexes. 图文摘要:
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24060. 题目: Selective removal of dissolved organic matter affects the production and speciation of disinfection byproducts 文章编号: N18102304 期刊: Science of The Total Environment 作者: Clayton J. Williams, Dan Conrad, Dolly N. Kothawala, Helen M. Baulch 更新时间: 2018-10-23 摘要: The heterogeneity of dissolved organic matter (DOM) in natural and human impacted waters and the variety of drinking water treatment processes employed has made a mechanistic understanding of disinfection byproduct (DBP) formation challenging. In this study, we examined the formation of the regulated DBPs (Trichloromethanes, THM, and Haloacetic acids, HAA) during full-scale water treatment operations both with prechlorination treatment (normal operations for the drinking water plant) and without (altered operations); followed by coagulation, flocculation, filtration, and chlorination. The source water DOM concentration ranged 6.4 to 7.3 mg-C/L. DOM composition was moderately humic and degraded with a mix of microbial- and terrestrial-like characteristics. Removal of raw water prechlorination caused an average reduction in total THM and HAA concentrations of 52.7% and 40.0%, respectively, with the greater reduction noted for chlorinated-DBPs rather than brominated-DBPs. Prechlorination treatment resulted in a higher relative production of Cl3CH and BrCl2CH associated with aromatic, humic, and terrestrial-like DOM. Without prechlorination, the DBP pool had higher proportions of brominated-DBPs (Br3CH, Br2ClCH, Br2CHCOOH, BrClCHCOOH, and BrCH2COOH) associated with microbial-like, processed humic-like, and protein-like DOM. These observed patterns could not be explained by chloride demand and DOM concentration, indicating that DOM composition played an important role in DBP formation. 图文摘要:
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