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28341. 题目: Factors Influencing Inhibitory Effect of Alginic Acid on the Growth Rate of Struvite Crystals
文章编号: N19010210
期刊: Water, Air, & Soil Pollution
作者: Lin Wei, Tianqiu Hong, Tianhu Chen, Xiaoyang Li, Qiang Zhang
更新时间: 2019-01-02
摘要: Phosphorus-rich sludge is one of most suitable raw materials for phosphorus recovery as slow release fertilizers by struvite crystallization. However, alginic acid as a surrogate for extracellular polymeric substances in the sludge has been proved to adversely inhibit struvite crystallization. To quantitatively evaluate the inhibitory effect, the study aimed to investigate the influence of the concentration of alginic acid (0–250 mg/L), reactant concentration (2.5–3.5 mmol/L), pH (8.0–9.5), and ionic strength (0.01–0.2 mol/L NaCl), on the inhibition of the growth rate of struvite crystals, which was accurately determined by constant composition technique. The results indicated that the growth rate of struvite crystals substantially decreased with increasing the concentration of alginic acid, thereby adversely affecting the quantity and quality of struvite crystals. Moreover, as reactant concentration or pH increased, the growth rate of struvite crystals showed a considerable increase, whereas the weaker inhibitory effect of alginic acid was observed. Conversely, the increase of ionic strength drastically reduced the growth rate of struvite crystals, but moderately enhanced the inhibitory effect. Our study provides an effective theoretical foundation for deriving high-quality struvite crystals as slow release fertilizers from the phosphorus-rich sludge commonly containing a considerable number of organic pollutants.

28342. 题目: Ecological stoichiometry characteristics of the leaf–litter–soil continuum of Quercus acutissima Carr. and Pinus densiflora Sieb. in Northern China
文章编号: N19010209
期刊: Environmental Earth Sciences
作者: Jianni Sun, Peng Gao, Cheng Li, Rongjia Wang, Xiang Niu, Bing Wang
更新时间: 2019-01-02
摘要: To research the nutrient circulation laws of the pine-oak forest ecosystem, this paper studied the ecological stoichiometry characteristics of organic carbon (C), total nitrogen (N) and total phosphorus (P) in the two “leaf–litter–soil” continuums (QAC: Quercus acutissima Carr., PDS: Pinus densiflora Sieb.) in China and their intrinsic relationships. Results showed that (1) Contents of C, N and P in the two continuums were C > N > P, and total contents of the different components were leaf > litter > soil. (2) Ecological stoichiometry characteristics of C, N and P in the two continuums were C:P > C:N > N:P. For the different components, the C:N and C:P were litter > leaf > soil, and the N:P was leaf > litter > soil. (3) Content of C in leaves was higher than that of the global and Chinese values and indicated that their defense capabilities against outside environmental forces were very strong. While contents of N and P in soil were lower than that of the global and Chinese values. Therefore, attention should be paid to selecting nitrogen fixing species and strengthening the construction of a mixed forest in mountainous area of northern China and similar areas around the world.

28343. 题目: Investigating responses of soil bacterial community composition to hardwood biochar amendment using high-throughput PCR sequencing
文章编号: N19010208
期刊: Applied Soil Ecology
作者: Emily J. Cole, Omid R. Zandvakili, Jeffrey Blanchard, Baoshan Xing, Masoud Hashemi, Fatemeh Etemadi
更新时间: 2019-01-02
摘要: The objectives of this field study were to evaluate the influence of sugar maple hardwood biochar on soil bacterial communities using next-generation sequencing via the Illumina MiSeq platform. Bacterial communities were sampled in soils with application rates of biochar including a control of 0%, 2% and a high rate of 4% by weight three years after incorporation of biochar. Bacterial 16S rRNA (V4 region) was sequenced using the Illumina MiSeq platform and identified using the SILVA database. Overall, the changes in the microbial communities with the addition of biochar were modest, potentially indicating an overall temporal-stability of diverse microbial communities in soil after biochar amendment. While individual taxa were significantly affected, including N-Cycling bacteria, there was no overall significant difference in total abundance, observed OTUs or alpha diversity indices.

28344. 题目: Cr(VI) removal from aqueous solution using biochar modified with Mg/Al-layered double hydroxide intercalated with ethylenediaminetetraacetic acid
文章编号: N19010207
期刊: Bioresource Technology
作者: Danlian Huang, Caihong Liu, Chen Zhang, Rui Deng, Rongzhong Wang, Wenjing Xue, Hao Luo, Guangming Zeng, Qing Zhang, Xueying Guo
更新时间: 2019-01-02
摘要: In this study, the bamboo biomass loaded with ethylenediaminetetraacetic acid (EDTA) intercalated Mg/Al-layered double hydroxides (LDH) was calcined to obtain a novel nano-adsorbent (BC@EDTA-LDH), and BC@EDTA-LDH was used to remove hexavalent chromium (Cr(VI)) in aqueous solutions. The results showed that the interaction between LDH and Cr(VI) on biochar played a dominant part in adsorption. The LDH of Cr(VI) intercalation was successfully reconstructed after adsorption. Fourier transform infrared spectra and X-ray diffraction results confirmed the reconstruction of Mg/Al-LDH. LDH had sustained release effect on the solution. As the pH values increased, the electrostatic repulsion between Cr₂O₇^2- and OH^- increased, and there existed competition for adsorption sites. The maximum adsorption capacity of Cr(VI) was 38 mg/g. The data was well-fitted with pseudo second-order model and Langmuir-Freundlich model. BC@EDTA-LDH showed a high adsorption capacity and was potentially suitable for removing heavy metals in wastewater.

28345. 题目: Organic carbon content drives methylmercury levels in the water column and in estuarine food webs across latitudes in the Northeast United States
文章编号: N19010206
期刊: Environmental Pollution
作者: V.F. Taylor, K.L. Buckman, E.A. Seelen, N.M. Mazrui, P.H. Balcom, R.P. Mason, C.Y. Chen
更新时间: 2019-01-02
摘要: Estuaries are dynamic ecosystems which vary widely in loading of the contaminant methylmercury (MeHg), and in environmental factors which control MeHg exposure to the estuarine foodweb. Inputs of organic carbon and rates of primary production are important influences on MeHg loading and bioaccumulation, and are predicted to increase with changes in climate and land use pressures. To further understand these influences on MeHg levels in estuarine biota, we used a field study approach in sites across different temperature regions, and with varying organic carbon levels. In paired comparisons of sites with high vs. low organic carbon, fish had lower MeHg bioaccumulation factors (normalized to water concentrations) in high carbon sites, particularly subsites with large coastal wetlands and large variability in dissolved organic carbon levels in the water column. Across sites, MeHg level in the water column was strongly tied to dissolved organic carbon, and was the major driver of MeHg concentrations in fish and invertebrates. Higher primary productivity (chlorophyll-a) was associated with increased MeHg partitioning to suspended particulates, but not to the biota. These findings suggest that increased inputs of MeHg and loss of wetlands associated with climate change and anthropogenic land use pressure will increase MeHg concentrations in estuarine food webs.
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28346. 题目: Dissolved organic matter characterization of biochars produced from different feedstock materials
文章编号: N19010205
期刊: Journal of Environmental Management
作者: Anushka Upamali Rajapaksha, Yong Sik Ok, Ali El-Naggar, Hyojeon Kim, Fanhao Song, Seoktae Kang, Yiu Fai Tsang
更新时间: 2019-01-02
摘要: Fluorescence excitation-emission matrix (EEM) spectroscopy coupled with parallel factor analysis (PARAFAC) enables better understanding of the nature of dissolved organic matter (DOM). In the current study, we characterized 10 biochar samples produced from different feedstocks using EEM/PARAFAC analysis. The composition and distribution of DOM substances present in biochar varied significantly according to feedstock, activation, and pyrolysis temperature. The integration of proximate and ultimate analyses of the solid phase together with water extractable organic matter (WEOM) phase of biochar provided new insights into the characterization of biochars, including nature and functionality. Characterization of both WEOM and solid phases is recommended for biochar research before large-scale production for various environmental and industrial applications.

28347. 题目: Effect of silver nanoparticles on an integrated fixed-film activated sludge–sequencing batch reactor: Performance and community structure
文章编号: N19010204
期刊: Journal of Environmental Sciences
作者: Hexi Zhou, Guoren Xu
更新时间: 2019-01-02
摘要: The effects of silver nanoparticles (AgNPs) on reactor performance, extracellular polymeric substances composition and microbial community structure and function in integrated fixed-film activated sludge–sequencing batch reactors (IFAS–SBRs) were investigated. Results showed that the addition of AgNPs from 0.1 to 10 mg/L exhibited no significant effects on nutrient removal. The average overall removal of COD, NH₄⁺–N and PO₄³⁻–P was 96.6%, 99.9% and 98.8%, respectively. The introduction of AgNPs caused an increase in extracellular polymeric substances content for the sludge and biofilm of IFAS–SBRs. The release of Ag⁺ from AgNPs and lactate dehydrogenase test implied the low toxicity of AgNPs to IFAS–SBRs. High-throughput sequencing revealed that microbial community structure showed significant shifts at phylum and genus levels after long-term exposure to AgNPs, but core functional groups responsible for nutrient removal remained at high abundance. Bacterial function prediction indicated that the metabolic categories showed no significant shifts under AgNPs stress, therefore good process performance could still be achieved.
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28348. 题目: Precipitation of calcium sulfate dihydrate in the presence of fulvic acid and magnesium ion
文章编号: N19010203
期刊: Chemical Engineering Journal
作者: Yudong Xu, Youxiang Liao, Zhenlin Lin, Jiang Lin, Qingwei Li, Jiuyang Lin, Zhengxin Jin
更新时间: 2019-01-02
摘要: The present work focused on the reduction of the calcium and sulfate ions in a membrane permeate generated from a newly developed two-stage of tight ultrafiltration (TUF) for recovering humic substance from leachate nanofiltration (NF) concentrate by a precipitation process of calcium sulfate dihydrate (gypsum). The operating parameters (temperature and pH), mechanism of precipitating behaviors, and kinetics of this process in the presence of fulvic acid (FA) and magnesium ion simultaneously were investigated. It was found that Ca²⁺ removal increased with increasing temperature. The decline in pH, especially towards low pH range of 2-3 around the point of zero charge of gypsum, showed a significant effect on gypsum precipitation. Adsorption of FA onto gypsum surface had an important effect on the precipitating behavior of gypsum whose mechanism might be mainly weak interactions of hydrogen bonding and hydrophobic effect at low pH, while electrostatic interactions became dominant at neutral pH. In contrast, retardation effect of Mg²⁺ ion on gypsum precipitation was negligible at pH 2.5. The soluble calcium removal during precipitation process corresponded with first order rate equation. The results indicated that the optimal operating parameters were found at 70 °C and around pH 2.5, which can be applied to the scale-up and industrial design of the precipitation process of gypsum for removing the calcium and sulfate ions in the presence of FA and magnesium ion.
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28349. 题目: In-situ power generation and nutrients recovery from waste activated sludge - long-term performance and system optimization
文章编号: N19010202
期刊: Chemical Engineering Journal
作者: Dan Wu, Faqian Sun, Feng Jun Desmond Chua, Dan Lu, David C. Stuckey, Yan Zhou
更新时间: 2019-01-02
摘要: This study reports an integrated sludge treatment and resource recovery system that consisted of a sludge pre-treatment reactor and a microbial fuel cell (MFC) aiming for simultaneous energy and nutrients recovery. Nearly one year performance of the system in terms of power generation, nutrients removal efficiency, key dissolved organic matters (DOMs) transformation and microbial community change were investigated and reported. Volatile fatty acids (VFAs) and other soluble organic matters was produced from fermentation of waste activated sludge under thermophilic alkaline condition. Fermented liquor (FL) was used as feed for MFC, which produced maximum voltage of 0.477 V and power density of 8.07 W m^-3. Humic-like substances (HSs) were removed by 48.27% within a 5 days cycle. The analysis on DOMs transformation revealed both high and low molecular weight protein and polysaccharides, and HSs were converted and contributed to power generation. Some unknown compounds in FL could enhance the power generation by 5.5 times more compared to pure VFA as feed. 90.59% of ammonium was removed with majority concentrated in the cathode. Phosphorus was removed and stored in the biomass in the form of polyphosphate (poly-P). Microbial community analysis indicated that Exoelectrogenic was the dominant community while Aquamicrobium, Nitrosomonas, Achromobacter and Rhodocylaceae were also enriched in the anode. This work demonstrates that the integrated system can successfully remove and recover nutrients and generate power simultaneously with long-term stable performance.
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28350. 题目: Intact polar lipid and core lipid inventory of the hydrothermal vent methanogens Methanocaldococcus villosus and Methanothermococcus okinawensis
文章编号: N19010201
期刊: Organic Geochemistry
作者: Lydia M.F. Baumann, Ruth-Sophie Taubner, Thorsten Bauersachs, Michael Steiner, Christa Schleper, Jörn Peckmann, Simon K.-M.R. Rittmann, Daniel Birgel
更新时间: 2019-01-02
摘要: For the first time, a comprehensive documentation of the core and intact polar lipid composition of the hydrogenotrophic, (hyper)thermophilic, methanogenic archaea Methanocaldococcus villosus strain DSM 22612^T and Methanothermococcus okinawensis strain DSM 14208^T is provided. Intact polar lipids of both organisms consist almost exclusively of glycolipids. M. villosus has mainly diglycosidic and some monoglycosidic head groups. In contrast, M. okinawensis is typified by more monoglycosidic than diglycosidic head groups and some phosphoglycosidic head groups. Both strains exhibit mainly diether lipids, namely archaeol and macrocyclic archaeol, which together account for 95% of the total core lipids. M. villosus reveals more macrocyclic archaeol (55%) than archaeol (39%). In M. okinawensis the ratio is almost reversed (35% macrocyclic archaeol; 59% archaeol). Both organisms also show minor relative abundances of GDD-0 (glycerol dialkyl diether) and GMD-0 (glycerol monoalkyl diether). The two methanogens also contained minute abundances of tetraether lipids. GDGT-0 (glycerol dialkyl glycerol tetraether) was dominant and accompanied by smaller amounts of GMGT-0 (glycerol monoalkyl glycerol tetraether) and GTGT-0 (glycerol trialkyl glycerol tetraether). Two isomers of GMGT-0 occurred in both organisms, whereas one was predominant in M. villosus and the other one in M. okinawensis. The detection of macrocyclic archaeol represents the first report of this compound in the genus Methanothermococcus. GTGT-0 and GMGT-0 have so far not been described in any representative of both genera, and two isomers of GMGT-0 not in any other organism. These new observations will be instrumental for the interpretation of archaeal-derived molecular fossils in environmental samples.

28351. 题目: Long-term nitrogen addition suppresses microbial degradation, enhances soil carbon storage, and alters the molecular composition of soil organic matter
文章编号: N19010101
期刊: Biogeochemistry
作者: Jun-Jian Wang, Richard D. Bowden, Kate Lajtha, Susan E. Washko, Sarah J. Wurzbacher, Myrna J. Simpson
更新时间: 2019-01-01
摘要: Forest soil organic carbon (SOC) is one of the largest reservoirs of terrestrial carbon (C) and is a major component of the global C cycle. Yet there is still uncertainty regarding how ecosystems, and the SOC they store, will respond to changes due to anthropogenic processes. Current and future reactive nitrogen (N) deposition to forest soils may alter biogeochemical processes and shift both the quantity and quality of stored SOC. We studied SOC storage and molecular-level composition after 22 years of N additions (100 kg N ha⁻¹ y⁻¹) in a temperate deciduous forest. SOC storage in surface soils increased by 0.93 kg m⁻² due to a decline in microbial biomass (phospholipid fatty acids) and litter decomposition. N additions resulted in the selective preservation of a range of plant-derived compounds including steroids, lignin-derived, cutin-derived, and suberin-derived compounds that have anti-microbial properties or are non-preferred microbial substrates. This overall shift in SOC composition suggests limited sustainability and a decline in soil health. The reduction in microbial biomass and increase in specific SOC components demonstrate that long-term N fertilization negatively alters fundamental C cycling in forest soils. This study also demonstrates unequivocally that anthropogenic impacts on C and N cycling in forests at the molecular-level must be considered more holistically.

28352. 题目: Organic fertilizer, but not heavy liming, enhances banana biomass, increases soil organic carbon and modifies soil microbiota
文章编号: N18123105
期刊: Applied Soil Ecology
作者: Jiangzhou Zhang, Shuikuan Bei, Baoshen Li, Junling Zhang, Peter Christie, Xiaolin Li
更新时间: 2018-12-31
摘要: Low soil pH and low soil organic matter content are major factors limiting banana production in acid soils. A pot experiment was conducted to determine whether liming or organic fertilizer is effective in mediating banana growth and soil health. The experiment comprised an unamended control and two treatments, lime and OF (organic fertilizer) and sampling was conducted twice, 65 and 280 days after planting. Soil nutrient concentrations, soil microbial communities and enzyme activities, and banana biomass and nutrient uptake were determined. As expected, the application of lime or organic fertilizer significantly increased soil pH and mineral nutrient concentrations and decreased Al³⁺ concentration. At both harvests an increase in bacterial and fungal diversity in the lime treatment and a shift in the soil bacterial and fungal communities did not translate into increased plant biomass. Organic fertilizer application significantly increased soil organic carbon content and enzyme activities, root length density down the soil profile, plant biomass and nutrient uptake compared to the lime treatment and the control. Changes in the soil microbial community in the organic fertilizer treatment compared to the control followed the same direction as in the lime treatment. However, the relative abundances of Actinobacteria and Ascomycota increased significantly 280 days after planting and potential pathogenic fungi including Fusarium decreased. Our results indicate that heavy liming alone may not be a viable approach to overcome the growth limiting factors in banana production on acid soils. In addition to the increased soil organic matter and nutrient availability, organic fertilizer may prime microbial activities and act as biologically active agent and/or enhance synergistic interactions within the soil microbiome in enhancing plant biomass. Increased soil biological activities after organic fertilizer application emphasize the importance of soil health in promoting the yield of banana crops.
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28353. 题目: Feasibility of dry anaerobic digestion of beer lees for methane production and biochar enhanced performance at mesophilic and thermophilic temperature
文章编号: N18123104
期刊: Bioresource Technology
作者: Caiyu Sun, Fang Liu, Zhiwei Song, Jing Wang, Yongfeng Li, Yu Pan, Tao Sheng, Lixin Li
更新时间: 2018-12-31
摘要: This study investigated the feasibility of dry anaerobic digestion using beer lees as substrate and the effect of cow manure-derived biochar addition on dry anaerobic digestion performance at mesophilic and thermophilic temperature, respectively. With TS content of 25%, maximum cumulative methane production and yield were achieved to be 5230±91 mL·d^-1 and 220.1±7.7 mL·g^-1 VS at mesophilic condition and 7386±134 mL·d^-1 and 310.4±9.2 mL·g^-1 VS at thermophilic condition in the control cultures. The biochar addition has a positive effect in improving dry anaerobic digestion performance. The maximum cumulative methane production and yield in the cultures with 10 g·L^-1 biochar were substantially improved by 82.9% and 82.6% at mesophilic condition and 47.2% and 46.8% at mesophilic condition when compared to the control.

28354. 题目: Optimization of second-phase sampling for multivariate soil mapping purposes: Case study from a wine region, Hungary
文章编号: N18123103
期刊: Geoderma
作者: Gábor Szatmári, Péter László, Katalin Takács, József Szabó, Zsófia Bakacsi, Sándor Koós, László Pásztor
更新时间: 2018-12-31
摘要: Over the last decades extensive work has been done on sampling optimization. Many of the related papers focused on the optimization of sampling for only one soil property. However, there is a necessity to prepare a sampling strategy which is optimized for multivariate digital soil mapping (DSM) purposes. The aim of our work was to elaborate a sampling optimization methodology for multivariate DSM considering the demands on economic efficiency. We presented and tested it through a real-time survey at Tokaj Wine Region, Hungary. The soil properties of interest were pH, soil organic matter (SOM), and calcium carbonate (CaCO₃) content. The end-users defined the minimal requested precision for the DSM products (in terms of the average range of the 90% prediction interval), and priority areas on which more detailed survey was requested. We planned a two-phase soil survey based on regression kriging (RK). The results from the first-phase sampling were used to parameterize the second-phase sampling in which spatial simulated annealing (SSA) was applied. The spatially averaged range of the 90% prediction interval was the pre-survey quality measure which can be readily derived from the RK variance. The workflow can be summarized as follows: (1) rank the soil properties considering their spatial variabilities, and precision requests, (2) optimize the sampling design by SSA for the dominant soil property, (3) optimize the sampling by the invers application of SSA for the next soil property using the optimized design from the previous step, and (4) repeat the previous step until all soil property are being selected. In our case, SOM was the dominant property. According to the plot of the sample size vs. quality measure, the optimized design with 500 samples will ensure the minimal requested precision for the SOM map (i.e. 0.5%). In the next step, the optimal removal of those sampling points was targeted which have less information content. In the cases of pH and CaCO₃, 100 and 175 could be removed from the 500 samples, and the remaining 400 and 325 samples will ensure the requested precision for the pH (i.e. 1.2) and CaCO₃ (i.e. 5%) maps. We computed the relative sampling density on priority and non-priority areas for each sampling designs which showed that densities on priority areas were at least 1.5 times higher than on non-priority areas. We could conclude that the methodology is able to optimize the sampling design for multivariate DSM purposes considering numerous sampling constraints such as the predefined precision, priority areas, and economic efficiency.

28355. 题目: Digital soil mapping of arable land in Sweden – Validation of performance at multiple scales
文章编号: N18123102
期刊: Geoderma
作者: Kristin Piikki, Mats Söderström
更新时间: 2018-12-31
摘要: In this study, we produced a detailed digital soil map of topsoil texture and soil organic matter (SOM) content for 2.4 million ha of arable land in Sweden (DSMS). Three spatially exhaustive datasets (a laser-scanned digital elevation model, airborne gamma radiation scanning data and a legacy Quaternary deposit map) were calibrated against topsoil texture and SOM content in around 13,500 soil samples, using multivariate adaptive regression splines (MARSplines) modelling. We then deployed the MARSplines models to produce raster maps (50 m × 50 m) of clay, sand and SOM content. The modelling procedure was validated by an independent dataset of about 24,000 samples clustered on 544 farms (with a local sample density of one per 3 ha). The error in clay content was < 8% in 75% of the validation samples, while for sand content and SOM content it was 13% and 2%, respectively. Corresponding values for the farm-average level were 6%, 11% and 2%, respectively. Modelling efficiency values revealed that the clay content map was a considerable improvement over the mean of the reference values at national level, regional level and, in many cases, also farm level. However, SOM content predictions showed little or no improvement over the mean of the reference samples (at any scale), due to poor correlation with the exhaustive predictor variables at all three scales investigated. The DSMS soil geodatabase will continue to be improved and have more layers added, e.g. derived layers calculated from the primary clay, sand and SOM layers by use of pedotransfer functions. Practical use of DSMS is exemplified here in an internet application for deriving prescription files for precision agriculture.
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28356. 题目: Spatial distribution of microbial biomass and residues across soil aggregate fractions at different elevations in the Central Austrian Alps
文章编号: N18123101
期刊: Geoderma
作者: Rajasekaran Murugan, Ika Djukic, Katharina Keiblinger, Franz Zehetner, Michael Bierbaumer, Sophie Zechmeister-Bolternstern, Rainer Georg Joergernsen
更新时间: 2018-12-31
摘要: The distribution of microbial biomass and residues and their role in carbon (C) dynamics within soil aggregate fractions in the Alps are still poorly explored. We assessed the distribution of bacterial and fungal residues and their impact on the contribution of the microbial community to C dynamics within soil aggregate size fractions at different elevations. We sampled three sites located at different elevations (1300, 1600 and 2100 m a.s.l.) and subject to different temperature and precipitation regimes in the Central Austrian Alps. Fungal biomass and residues were higher in macro-aggregate fractions compared to micro-aggregates, as indicated by the ratios ergosterol/microbial biomass C and fungal C/bacterial C, suggesting a combined but discrete contribution of fungi and bacterial residues to soil aggregate formation. A greater contribution of microbial residues to soil organic C (SOC) in macro-aggregates demonstrates the importance of microbial residues for the soil organic matter pool's capacity to function as an active nutrient sink and source reservoir. The mid- and low-elevation spruce sites were dominated by fungi and higher aggregate stability, whereas the high-elevation grassland site exhibited a stronger bacterial community as indicated by fungal C/bacterial C ratio. In addition, greater proportions of fungal and bacterial residue in SOC at mid-elevation spruce and high-elevation grassland sites respectively, indicate differential role of fungi and bacteria in SOC sequestration. However, the observed changes in microbial community and residue contribution were mainly driven by variations in soil pH, C/N ratio and fine root biomass. Our findings indicate that fungi played a key role in the internal cycling of SOC and aggregate stability at the mid-elevation spruce site, while bacterial residues were successively activated and contributed increasingly to SOC sequestration at the high-elevation grassland site.

28357. 题目: The role of humic acids on gemfibrozil toxicity to zebrafish embryos
文章编号: N18123006
期刊: Chemosphere
作者: Ana Rita Almeida, Fátima Jesus, Jorge F. Henriques, Thayres S. Andrade, Ângela Barreto, Olga Koba, Pham Thai Giang, Amadeu M.V.M. Soares, Miguel Oliveira, Inês Domingues
更新时间: 2018-12-30
摘要: Climate change is expected to alter the dynamics of water masses, with consequent changes in water quality parameters such as dissolved organic carbon (DOC) concentration. DOC levels play a critical role in the fate of organic chemicals, influencing their bioavailability and toxicity to aquatic organisms. This study aimed to evaluate the effects of DOC, particularly humic acids (HA), in the toxicity of gemfibrozil (GEM) - a human pharmaceutical frequently detected in surface waters. Lethal and sublethal effects (genotoxic, biochemical and behavioural alterations) were evaluated in zebrafish embryos exposed to several concentrations of GEM and three HA levels, in a full factorial design. HA significantly increased GEM LC₅₀ values, mainly in the first 72 h of exposure, showing a protective effect. At sublethal levels, however, such protection was not observed since HA per se elicited adverse effects. At a biochemical level, individual exposure to HA (20 mg/L) elicited significant decreases in cholinesterase and glutathione S-transferase activities. Regarding behaviour, effects of individual exposure to HA appear to surpass the GEM effects, reducing the total distance moved by larvae. Both GEM and HA significantly increased DNA damage. Hence, this study demonstrated that abiotic factors, namely HA, should be considered in the assessment of pharmaceuticals toxicity. Moreover, it showed that lethality may not be enough to characterize combined effects since different patterns of response may occur at different levels of biological organization. Testing sublethal relevant endpoints is thus recommended to achieve a robust risk assessment in realistic scenarios.

28358. 题目: Long-term effect of crude oil and dispersant on denitrification and organic matter mineralization in a salt marsh sediment
文章编号: N18123005
期刊: Chemosphere
作者: Hanh Thi Van Le, Kewei Yu
更新时间: 2018-12-30
摘要: The 2010 BP oil spill has an unprecedented impact on coastal wetland ecosystem along the northern Gulf of Mexico. A two-dimensional analysis (dispersant concentration and duration of exposure) was conducted by pre-incubation of a salt marsh sediment under an open or closed condition. Denitrification activity was characterized by N₂O production using an acetylene (C₂H₂) blockage technique, and organic matter (OM) mineralization by CO₂ production. The results show that even trace amount of the dispersant could significantly inhibit the denitrification activity by 20% (p < 0.05). However, the sediment was resilient to the oil/dispersant contamination, likely due to shift of its microbial communities, by recovering the denitrification activity within 46 days in the open incubation. Inhibitory effect of the oil/dispersant on denitrification persisted beyond 46 days in the closed incubation, and the recovery could take up to 137 days depending on the dispersant concentration. The dispersant continuously stimulated OM mineralization that lowered the sediment redox status. Mobilization of N in the sediment from the OM mineralization forms a positive feedback loop, leading to deterioration of the coastal ecosystem. The study concludes that minimum dispersant should be applied for oil spill remediation, and oil cleanup operations should avoid moving the oil/dispersant from surface into deeper layers of the sediment. Synergistic interactions between the crude oil and dispersant and their biodegradation products deserves future examinations.

28359. 题目: Impact of long-term N fertilisation on CO₂ evolution from old and young SOM pools measured during the maize cropping season
文章编号: N18123004
期刊: Science of The Total Environment
作者: Muhammad Shahbaz, Lorenzo Menichetti, Thomas Kätterer, Gunnar Börjesson
更新时间: 2018-12-30
摘要: The relationship between carbon (C) inputs and nitrogen (N) fertilisation is a key element of soil organic matter (SOM) dynamics, which remains poorly resolved. In temperate climates, it is critical to investigate the interactive effect of C and N inputs on SOM stabilisation under low or high substrate availability. We measured SOM content and in situ soil respiration in a long-term field experiment in Sweden, which started in 1956. In 2000, the previous C3 crops were replaced with C4 maize, making it possible to trace old- (C3-derived) and young-C (C4-derived) sources in CO₂ and SOM under bare fallow, maize cropped with or without N-fertilisation (root C-inputs). Soil respiration and its isotopic composition were measured in the field prior to sowing, every second week during crop growth and once after harvest. During 1956–1999, the bare fallow lost 38% of its SOM, following an exponential decay trend. Despite root C inputs, total SOM content under C3 crops declined from 1.5% in 1956 to 1.4% and 1.2% C in fertilised and unfertilised treatments, respectively, in 1999. After the crop change in 2000, estimated C input increased by 5% (under fertilisation), but SOM content continued to decline (as before 2000), to 1.25% (fertilised) and 1.03% (unfertilised) in 2017. Analysis of δ¹³C revealed that 9 and 11% of young-C was retained in unfertilised and fertilised SOM, respectively. However, up to 70% of soil respiration derived from young-C. Comparing the contributions of old- and young-C to CO₂ and SOM showed that, irrespective to the time of measurement, young-C was always more available for microbial decomposition than old-C, particularly under fertilisation. We conclude that the amount of C entering the soil through root inputs was insufficient to counterbalance SOM losses over time. Moreover, soil nutrient status and recent root-C availability appear to be important for CO₂ release, and must be considered in further recommendations on maintaining/improving SOM stocks.
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28360. 题目: Fate of selenium in soil: A case study in a maize (Zea mays L.) field under two irrigation regimes and fertilized with sodium selenite
文章编号: N18123003
期刊: Science of The Total Environment
作者: M. De Feudis, R. D'Amato, D. Businelli, M. Guiducci
更新时间: 2018-12-30
摘要: Selenium (Se) is a trace element necessary for both human and livestock nutrition. To increase Se human intake, soil Se fertilizations were performed but the fate of the added Se remains unclear. The present research aims to: (1) determine the influence of Se fertilization on the fractionation of Se in soil; (2) assess the influence of water availability on the distribution of soil Se chemical fractions; and (3) monitor the Se content in soil, leachates and plants. To reach these goals, 200 g Se ha⁻¹ was applied to soil as sodium selenite in maize crops under two irrigation regimes, and the Se content in plant, soil chemical fractions and leachates were analyzed. Se application increased the total Se content of the soil, specifically it increased the Se content of the soluble, exchangeable and organic fractions with more pronounced effect in the soils with higher water availability. These differences disappeared over time likely due to the Se loss through volatilization. The hypothesis of Se volatilization is confirmed by the absence of both leachates during the maize growing season and differences among the treatments of Se content in sub-soil samples. Also, although the Se treated plants showed higher Se content than the untreated ones, overall <1% of the added Se was assimilated by plants. Hence, this study demonstrated that the addition of selenite to the soil increased the Se contents of the plants, but the Se does not accumulate in the soil because it is likely lost via volatilization. Further, leaching of Se into groundwater is avoided due to its association with both the soil organic matter and positively charged binding sites of soil, and due to its loss via volatilization. Therefore, soil Se fertilization could increase the nutritional value of plants without consequences on the environment.
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