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29121. 题目: Comparative study of electrochemical hybrid systems for the treatment of real wastewaters from agri-food activities
文章编号: N18082417
期刊: Science of The Total Environment
作者: Mouna Ghazouani, Hanene Akrout, Salah Jellali, Latifa Bousselmi
更新时间: 2018-08-24
摘要: Agri-food wastewaters are characterized by high contents of hardly biodegradable organics and large amounts of inorganics especially nitrogen and phosphorus. The present work investigates the efficiency of two electrochemical treatment processes, namely electrochemical oxidation/reduction (EOR), electrocoagulation (EC) and their combination for the treatment of two types of effluents collected from poultry slaughterhouse (SHWW) and dairy (DWW) industries. The optimization of these treatment systems in terms of pollutant performance removal and energy cost were carried out. The EOR treatment was assessed on a bipolar cell with Boron-Doped Diamond (BDD) supported on silicon electrodes. While, the EC treatment was performed on a reactor containing mild steel electrodes with parallel configuration. The simultaneous removal efficiencies of the organic matter in term of the chemical oxygen demand (COD), nitrates, ammonium/ammonia and phosphates, as well as the electric energy consumption (EEC), were evaluated for the different electrochemical scenarios. Results indicated that the EOR treatment shows the highest removal efficiencies of COD, nitrates and ammonia from the two studied wastewaters. While, the phosphates were removed only by the EC process. On the other hand, the EC process shows a relatively low cost in term of EEC (0.01 kWh/g COD−1), which is about 13 times lower than the one consumed during the EOR process. The combination of the two processes leads to the improvement of the removal rate of all coexistent pollutants when the EC technology was used as a pre-treatment step. While, this coupling mode has the highest EEC. However, when the EOR process was used before the EC one, the removal rates of COD and nitrates were globally similar to the EOR process alone with a relatively low EEC.
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29122. 题目: Dissolved organic matter processing and photoreactivity in a wastewater treatment constructed wetland
文章编号: N18082416
期刊: Science of The Total Environment
作者: Arpit Sardana, Barbara Cottrell, David Soulsby, Tarek N. Aziz
更新时间: 2018-08-24
摘要: Constructed wetlands have the capacity to degrade a host of contaminants of emerging concern through photodegradation via sunlight produced reactive oxygen species. Dissolved organic matter (DOM) is a critical intermediary in photodegradation as it influences the production of reactive oxygen species. In this study, the photochemical behavior of DOM of wastewater treated in constructed wetlands was characterized. Whole water samples and fractionated DOM were characterized using SUVA254, spectral slope ratios, excitation emission matrix fluorescence spectroscopy (EEMs), and proton nuclear magnetic resonance (1H NMR). Photoreactivity was assessed by measuring formation rates and steady state concentrations of hydroxyl radical (•OH), singlet oxygen (1O2), and the triplet excited states of DOM (3DOM⁎). The effluent was observed to transition from a microbially sourced protein-like DOM to a terrestrial DOM with higher aromaticity. Size exclusion chromatography revealed an 18% increase in larger molecular weight fractions of vegetated wetland effluent DOM. Additionally, wetland effluent DOM was observed to have a 32% increase in the aromatic region of 1H NMR spectra as compared to untreated wastewater. 1H NMR analysis also indicated an increase in the complexity of wetland effluent DOM. Fluorescence intensity fraction of the protein-like Peak T (Ex/Em:278/342 nm) of EEMs decreased by 16% from the untreated wastewater to wetland effluent. A negative correlation between the percent fluorescence of Peak T (Ex/Em:278/342 nm) and Peaks A (Ex/Em:245/460 nm), C (Ex/Em:336/435 nm), and M (Ex/Em:312/400 nm) of the excitation emission spectra confirmed the transition from a spectrum of pure wastewater to a spectrum characteristic of terrestrially derived DOM. Microbial uptake of bio-labile DOM and leaching of humic like substances from vegetated wetland cells were the predominant processes involved in this transition. This transition coincided with an increase in the formation rates of 1O2 and 3DOM⁎ and in the steady state concentration of 1O2.
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29123. 题目: Biodegradation of oxytetracycline and enrofloxacin by autochthonous microbial communities from estuarine sediments
文章编号: N18082415
期刊: Science of The Total Environment
作者: Malek Harrabi, Diogo A.M. Alexandrino, Fatma Aloulou, Boubaker Elleuch, Bei Liu, Zhongjun Jia, C. Marisa R. Almeida, Ana P. Mucha, Maria F. Carvalho
更新时间: 2018-08-24
摘要: This work investigated the potential of microbial communities native to an estuarine environment to biodegrade enrofloxacin (ENR) and oxytetracycline (OXY). Sediments collected from two sites in the Douro river estuary (Porto, Portugal) were used as inocula for the biodegradation experiments. Experiments were carried out for one month, during which ENR and OXY (1 mg L−1) were supplemented individually or in mixture to the cultures at 10-day intervals. Acetate (400 mg L−1) was added to the cultures every 3 days to support microbial growth. A series of experimental controls were established in parallel to determine the influence of abiotic breakdown and adsorption in the removal of the antibiotics. Removal of antibiotics was followed by measuring their concentration in the culture medium. Additionally, next-generation sequencing of the 16S rRNA gene amplicon was employed to understand how microbial communities responded to the presence of the antibiotics. At the end of the biodegradation experiments, microbial cultures derived from the two estuarine sediments were able to remove up to 98% of ENR and over 95% of OXY. The mixture of antibiotics did not affect their removal. ENR was removed mainly by biodegradation, while abiotic mechanisms were found to have a higher influence in the removal of OXY. Both antibiotics adsorbed at different extents to the estuarine sediments used as inocula but exhibited a higher affinity to the sediment with finer texture and higher organic matter content. The presence of ENR and OXY in the culture media influenced the dynamics of the microbial communities, resulting in a lower microbial diversity and richness and in the predominance of bacterial species belonging to the phylum Proteobacteria. Therefore, microbial communities native from estuarine environments have potential to respond to the contamination caused by antibiotics and may be considered for the recovering of impacted environments through bioremediation.
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29124. 题目: Influence of parasitic chytrids on the quantity and quality of algal dissolved organic matter (AOM)
文章编号: N18082414
期刊: Water Research
作者: Yukiko Senga, Shiori Yabe, Takaki Nakamura, Maiko Kagami
更新时间: 2018-08-24
摘要: Algae-derived dissolved organic matter (AOM) is an important nutrient source for heterotrophic bacteria, while AOM such as humic substances pose significant challenges during water treatment processing. We hypothesized that the parasitic infection of algae could change the composition and concentration of AOM. This study investigated the quality and quantity of DOM and bacterial abundance in diatom (Synedra) cultures, with and without parasitic fungi (chytrids). The quality of DOM was analyzed using three-dimensional excitation-emission matrices combined with parallel factor analysis (EEM-PARAFAC) and was compared to changes in algal and bacterial cell numbers. Bacterial abundance was higher and dissolved organic carbon concentrations were lower in the diatom cultures infected with parasitic fungi. Among the DOM compounds, the concentrations of tryptophan-like material derived from algae were significantly lower and the concentrations of humic substance-like material were higher in the infected treatment. The parasitic fungi may have consumed tryptophan-like material and stimulated the release of humic substances. These results provide the first evidence that fungal infection may modulate algal–bacterial interactions, which are associated with changes in the nature of AOM.
29125. 题目: Impact of soil properties on soil methane flux response to biochar addition: a meta-analysis
文章编号: N18082413
期刊: Environmental Science: Processes Impacts
作者: Weiwei Cong, Jun Meng, Samantha C Ying
更新时间: 2018-08-24
摘要: In an effort to optimize soil management practices that can help mitigate terrestrial carbon emissions, biochar has been applied to a wide range of soil environments to examine their effect on soil greenhouse gas emissions. Such studies have shown that soil methane (CH4) flux response can vary widely leading to both increase and decrease in CH4 flux upon biochar amendment. To address this discrepancy, multiple meta-analysis studies have been performed in recent years to determine the key factors that may control the direction of CH4 flux upon biochar treatment. However, even comparing across conclusions from meta-analyses reveals disagreement upon which factors ultimately determine the change in direction and magnitude of CH4 flux due to biochar additions. Furthermore, using multiple observations from a single study can lead to misinterpretation of the influence of a factor within a meta-analysis due to non-independence. In this study, we use a multivariate meta-regression approach that allows factor interactions to investigate which biochar, soil, and management practice factors in combination or individually best explain CH4 flux response in past biochar amendment studies. Our results show that the interaction of multiple soil factors (i.e., water saturation, soil texture, soil organic carbon content) best explains soil CH4 flux response to biochar additions (minimum deviance information criterion, DIC, value along with lowest heterogeneity) as compared to all models utilizing individual factors alone. These findings provide insight into the specific soil factors that should be taken into account simultaneously when optimizing CH4 flux response to biochar amendments and building empirical models to quantitatively predict soil CH4 flux.
29126. 题目: Diffusion limitations and Michaelis–Menten kinetics as drivers of combined temperature and moisture effects on carbon fluxes of mineral soils
文章编号: N18082412
期刊: Biogeosciences
作者: Fernando Esteban Moyano, Nadezda Vasilyeva, and Lorenzo Menichetti
更新时间: 2018-08-24
摘要: CO2 production in soils responds strongly to changes in temperature and moisture, but the magnitude of such responses at different timescales remains difficult to predict. Knowledge of the mechanisms leading to the often observed interactions in the effects of these drivers on soil CO2 emissions is especially limited. Here we test the ability of different soil carbon models to simulate responses measured in soils incubated at a range of moisture levels and cycled through 5, 20, and 35°C. We applied parameter optimization methods while modifying two structural components of models: (1) the reaction kinetics of decomposition and uptake and (2) the functions relating fluxes to soil moisture. We found that the observed interactive patterns were best simulated by a model using Michaelis–Menten decomposition kinetics combined with diffusion of dissolved carbon (C) and enzymes. In contrast, conventional empirical functions that scale decomposition rates directly were unable to properly simulate the main observed interactions. Our best model was able to explain 87% of the variation in the data. Model simulations revealed a central role of Michaelis–Menten kinetics as a driver of temperature sensitivity variations as well as a decoupling of decomposition and respiration C fluxes in the short and mid-term, with general sensitivities to temperature and moisture being more pronounced for respiration. Sensitivity to different model parameters was highest for those affecting diffusion limitations, followed by activation energies, the Michaelis–Menten constant, and carbon use efficiency. Testing against independent data strongly validated the model (R2 = 0.99) and highlighted the importance of initial soil C pool conditions. Our results demonstrate the importance of model structure and the central role of diffusion and reaction kinetics for simulating and understanding complex dynamics in soil C.
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29127. 题目: Soil chemistry and microbial community functional responses to invasive shrub removal in mixed hardwood forests
文章编号: N18082411
期刊: Applied Soil Ecology
作者: Graham S. Frank, Cindy H. Nakatsu, Michael A. Jenkins
更新时间: 2018-08-24
摘要: Invasive woody plant species are a threat to biodiversity and ecosystem function in forests of the eastern U.S., due in part to their effects on soil properties and nutrient cycling. Controlling invasive shrubs can benefit the ecosystem at multiple scales, but these species tend to resprout when cut, and post-cutting flushes of root exudates have been linked to accelerated decomposition of soil organic matter (SOM), a rhizosphere priming effect. We removed the invasive shrub Lonicera maackii (Rupr.) Herder (Amur honeysuckle) from forested sites in central Indiana, USA, using cut-stump and forestry mulching head treatments. For two growing seasons after the initial removal treatments, we compared the soil chemistry and microbial community function of bulk and honeysuckle rhizosphere soils in shrub removal areas to those in invaded reference areas. Microbial activity measured using multiple substrate induced respiration (MSIR) in bulk soils was generally lower in removal areas than reference areas the first year, coinciding with relatively elevated responses in the rhizosphere soils of resprouting shrubs. Elevated SOM and organic C in rhizosphere soils of resprouting shrubs suggested a flush of rhizodeposits from cutting and regrowth. However, bulk soil chemistry responses to shrub removal did not show any evidence of a rhizosphere priming effect, but instead reflected the reduced effects of honeysuckle on throughfall precipitation chemistry—higher ammonium and lower magnesium. Nonetheless, changes in bulk soil chemistry between years were driven by the chemical characteristics of rhizosphere soil associated with resprouting honeysuckle. This study is the first to document the potential for invasive shrub control to affect soil properties through rhizodeposition by the target species.
29128. 题目: What can we learn from ancient fertile anthropic soil (Amazonian Dark Earths, shell mounds, Plaggen soil) for soil carbon sequestration?
文章编号: N18082410
期刊: CATENA
作者: Jürgen Kern, Luise Giani, Wenceslau Teixeira, Giacomo Lanza, Bruno Glaser
更新时间: 2018-08-24
摘要: Historical land use and soil management left behind anthropic soils such as Amazonian Dark Earths (Terras Pretas de Índio - pretic Anthrosols), Anthropic shell mounds (Sambaquis - terric Anthrosols), and Plaggen soils (plaggic Anthrosols), enriched in soil organic matter and soil fertility. The objective of this study was to compare soil organic matter quantity and quality of these tropical and temperate anthropic soils among each other and against their adjacent non-anthropic soils. All anthropic soil horizons had enhanced total contents of C, N, P, K, Ca, Mg and Fe, reflecting a soil organic matter and nutrient enrichment compared to their reference soils, mostly expressed by the Sambaquis. In order to better understand the mechanisms of soil organic matter stability, besides black carbon analysis, topsoils and subsoils were incubated in the laboratory at 10 °C and 30 °C and the emitted CO2 was recorded for 44-days. The Plaggen soil released the highest amount of CO2 at 30 °C, being two to three times higher compared to Terra Preta de Índio and Sambaqui anthropic horizons. The highest mean residence times (MRT), between 38 and 63 years, were calculated for the subsoils of the anthropic soils incubated at 10 °C. In the artificial system of this study, the stability of anthropic soil horizons under study was not generally enhanced when compared with their reference soils. However, enhanced stability of total organic carbon (TOC) was indicated by a negative relationship between black carbon portion of TOC and the relative amount of CO2-C released from TOC of all anthropic soils. During the incubation period of 44 days, the cumulatively mineralized amount of soil organic carbon (SOC) in the top of anthropic soils at 30 °C was three to six times as high as that at 10 °C. Consequently high temperature under tropical conditions should have stimulated the decay of organic matter, which however was not reflected by high TOC contents found in Terra Preta and Sambaqui samples, corroborating their low degradability in the long term. Therefore, we propagate that a high stability of carbon stocks exists in anthropic soil horizons, which may become a promising opportunity for the establishment of a new generation of anthropic soils with improved soil fertility and soil organic matter using the principle of soil-biochar systems.
29129. 题目: Ozone/peroxide advanced oxidation in combination with biofiltration for taste and odour control and organics removal
文章编号: N18082409
期刊: Chemosphere
作者: Divyam Beniwal, Liz Taylor-Edmonds, John Armour, Robert C. Andrews
更新时间: 2018-08-24
摘要: The objective of this pilot-scale study was to investigate the effectiveness of incorporating ozone (O3) and advanced oxidation (hydrogen peroxide/ozone: H2O2/O3) in combination with biofiltration for taste and odour control, organic carbon removal, and disinfection byproduct (DBP) precursor reduction. Implementation of O3 and H2O2/O3 with and without biofiltration was investigated at pilot-scale in terms of geosmin, 2-methylisoborneol (MIB), and DBP precursor removal efficiency. Two media types (granular activated carbon and anthracite) were compared in conjunction with investigating the impact of pre-oxidation with O3 (2 mg/L) and varying H2O2/O3 mass ratios (0.1, 0.2, 0.35, and 0.5 mg/mg). When O3 preceded biologically active carbon (BAC) or biologically active anthracite, geosmin removals of 80% and 81%, respectively, were observed at 10 °C; this increased to 89% and 90%, respectively, at 16 °C. Optimal MIB removal (67%) was achieved with 0.1 H2O2/O3 (mg/mg) in combination with BAC at 16 °C.In general, geosmin proved to be more amenable to biodegradation than MIB. BAC without pre-oxidation removed 87% geosmin and 85% MIB, at 22 °C. MIB removals decreased to 60% and 46%, respectively at 16 °C and 10 °C. The application of 0.2 H2O2/O3 (mg/mg) prior to BAC provided treatment which effectively removed geosmin and MIB. However, in terms of DBP precursor reduction, there was no beneficial impact of H2O2 addition on trihalomethane or haloacetic acid formation potentials.
29130. 题目: Sulfur-isotope evidence for recovery of seawater sulfate concentrations from a PTB minimum by the Smithian-Spathian transition
文章编号: N18082408
期刊: Earth-Science Reviews
作者: Alan Stebbins, Thomas J. Algeo, Christian Olsen, Hiroyoshi Sano, Harold Rowe, Robyn Hannigan
更新时间: 2018-08-24
摘要: The Smithian-Spathian substage boundary (SSB) in the Early Triassic was an important time interval during the protracted recovery of marine faunas and ecosystems following the end-Permian mass extinction event. Although some Tethyan SSB sections have been studied, little information is available regarding environmental conditions in the Panthalassic Ocean, which comprised ~85% of the Early Triassic global ocean, during the Smithian-Spathian transition. Understanding changes in the carbon and sulfur cycles during the Early Triassic is important for deciphering the pattern and controls on the marine recovery. Our understanding of the Early Triassic sulfur cycle, in particular, is incomplete. In this study, we report carbonate carbon and oxygen, carbonate-associated sulfate (CAS) sulfur and oxygen, and pyritic sulfur isotopic ratios from the Jesmond section, Cache Creek Terrane, western Canada. This section, which formed as a tropical carbonate atoll in the middle of the Panthalassic Ocean, spans the latest Smithian to middle Spathian. Both δ34SCAS and δ18OCAS increased through the SSB transition before decreasing in the early Spathian, matching variation in the δ13Ccarb profile. We hypothesize that the sharp increase in δ34SCAS and δ18OCAS at the SSB reflects a global increase in the amount of microbial sulfate reduction (MSR) and pyrite burial. Driving this increase in MSR and pyrite burial were cooling temperatures, increasing primary productivity, and increasing organic matter availability. The decreasing trend immediately following the SSB indicates that these environmental changes reached maxima and began to diminish or reverse in the early Spathian. The difference between δ34SCAS and δ34Spyr values (Δ34SCAS-pyr) remained relatively stable from the latest Smithian through the middle Spathian. This stability provides an estimate of MSR sulfur-isotope depletion allowing us to estimate paleo-seawater sulfate concentrations. Using the “MSR-trend” method, we estimate that Early Triassic seawater sulfate concentrations were between 2.5 and 9.1 mM. These estimates are higher than previously published values for the Permian-Triassic boundary, suggesting an overall increase in seawater sulfate by the late Early Triassic.
29131. 题目: Understanding the fate of soil organic matter in submerging coastal wetland soils: A microcosm approach
文章编号: N18082407
期刊: Geoderma
作者: Havalend E. Steinmuller, Kyle M. Dittmer, John R. White, Lisa G. Chambers
更新时间: 2018-08-24
摘要: Coastal wetland submergence can occur when rates of relative sea-level rise exceed that of soil elevation gain or landward transgression. In highly organic soils, the collapse of the wetland platform into open water can cause disarticulation of the soil structure, exposing previously protected anaerobic microzones to oxygenated seawater, which may accelerate mineralization rates. Nine soil cores (1 m deep) were collected from three sites within Barataria Bay, LA (USA), a region known for high rates of wetland submergence. Both the biogeochemical properties of the soils with depth were determined, as well as the impacts of the introduction of oxygenated seawater on carbon mineralization rates. Both field enzyme activity (β‑glucosidase, N‑acetyl‑beta‑d‑glucosaminidase, alkaline phosphatase, β‑xylosidase, and β‑cellobiosidase) and microbial biomass carbon (MBC) did not significantly change with depth until 50 cm, where activity increased dramatically, then gradually decreased. Total carbon (C), total nitrogen, and percent organic matter were highest between 50 and 100 cm. Following initial biogeochemical characterization, soil microcosms were created for 11 depth segments under anaerobic conditions (mimicking an intact wetland) and aerobic conditions (mimicking a submerging wetland mixing with oxygenated water); carbon dioxide (CO2) production was measured within the bottles over 14 days. Carbon dioxide production averaged 66% greater in the aerobic treatment than the anaerobic treatment. Both treatments exhibited a general trend of increasing CO2 production with depth (particularly from 40 to 100 cm), with the difference in CO2 production between aerobic and anaerobic treatments being 4× greater at 90–100 cm than at the soil surface (0–5 cm). The increase in C mineralization rates observed at depth was positively correlated with indicators of greater microbial activity (i.e., higher enzyme activity and MBC) and greater nutrient availability. Study results indicate coastal wetland submergence into open water could significantly enhance CO2 emissions, even in deep (40+ cm) soils, contrary to the typically observed pattern of soil microbial activity and soil quality decreasing with depth. These findings underline the need to analyze deeper soil samples (1+ m) in order to fully understand the implications of sea level rise on C loss from submerging coastal wetland soils.
29132. 题目: Influence of rice husk biochar and inorganic fertilizer on soil nutrients availability and rain-fed rice yield in two contrasting soils
文章编号: N18082406
期刊: Geoderma
作者: S.O. Oladele, A.J. Adeyemo, M.A. Awodun
更新时间: 2018-08-24
摘要: The co-application of biochar and inorganic N fertilizer has been shown to be a sustainable and environmental friendly technology for the improvement of soil fertility and crop yield. However, their interactive effects on nutrient availability and rain-fed rice productivity in contrasting soil types in the tropics have been scarcely studied. A field study was set up to investigate the effects of rice husk biochar and N-fertilizer applications at different rates on rain-fed rice yield and soil nutrient distribution in the 0–20 cm soil layer. Biochar was applied at four rates; 0, 3, 6, and 12 t/ha−1, in combination with N fertilizer (urea) applied at four rates; 0, 30, 60 and 90 kg/ha−1 to two different soil types (sandy clay loam Oxic-Paleustalf and sandy loam Oxic-Paleustult). In the Oxic-Paleustaif, biochar × N-fertilizer interaction significantly (p < 0.05) enhanced rain-fed rice yield and yield components such as number of panicles/m2 by 71%, filled spikelet (%) by 24%, grain yield (t/ha−1) by 78%, straw yield (t/ha−1) by 74% and 1000 grain weight (g) by 16% when compared to the control. In the Oxic-Paleustult, interaction between biochar and N-fertilizer significantly (p < 0.05) increased number of panicles/m2 by 73%, filled spikelet (%) by 24%, grain yield (t/ha−1) by 83%, straw yield (t/ha1) by 68% and 1000 grain weight (g) by 13% in the when compared to the control. Leaching of soil nitrate (NO3-N) was mostly reduced in the Oxic-Paleustalf, while soil pH, soil organic carbon (SOC), total nitrogen (TN), available P and K content at the soil depth of 0–10 cm were significantly (p < 0.05) increased in both soil types. The result from this study suggest that biochar amendment and N fertilization have the potential to enhance rain-fed rice productivity and soil nutrient availability, while minimizing nitrate (NO3-N) leaching.
29133. 题目: The chemical form of silicon in marine Synechococcus
文章编号: N18082405
期刊: Marine Chemistry
作者: Daniel C. Ohnemus, Jeffrey W. Krause, Mark A. Brzezinski, Jackie L. Collier, Stephen B. Baines, Benjamin S. Twining
更新时间: 2018-08-24
摘要: The widely distributed marine picocyanobacterium Synechococcus is found throughout the upper oceans. Recent observations that Synechococcus accumulates silicon indicate that it may influence the global cycle of this element. While diatoms, the organisms that dominate the marine Si cycle, have absolute Si requirements due to their precipitation of exoskeleton frustules composed of hydrated opal-A (i.e., biogenic silica), no requirements or biological roles are known for the Si associated with Synechococcus. Even less is known about the biochemical form(s) of Si in picocyanobacteria or whether it differs from diatomaceous silica. Using bulk X-ray absorption near-edge spectroscopy (XANES) across the Si K-edge, we investigated the chemical speciation of Si in dried Synechococcus laboratory isolates from several clades, representing both coastal and oligotrophic isolates grown at a range of Si(OH)4 concentrations. Silicon associated with Synechococcus is bound to oxygen and is spectroscopically distinct from opal-A precipitated by diatoms. The closest XANES spectral analogues found in the literature are dried Mg-Si gels precipitated under basic conditions, suggesting that some Synechococcus Si may be present in vivo as a hydrated siliceous network with Mg and/or Ca cations. Slight spectral variations across isolates and growth conditions suggest strain-specificity in Si chemistry and the potential for siliceous phases to bind organic matter.
29134. 题目: Potential methane production and molecular characterization of bacterial and archaeal communities in a horizontal subsurface flow constructed wetland under cold and warm seasons
文章编号: N18082404
期刊: Science of The Total Environment
作者: Daniela López, Mario Sepúlveda-Mardones, Nathaly Ruiz-Tagle, Katherine Sossa, Enrica Uggetti, Gladys Vidal
更新时间: 2018-08-24
摘要: Organic matter removal in a horizontal subsurface flow constructed wetland (HSSF) treating wastewater is associated with the presence of bacteria and archaea. These organisms perform anaerobic microbial processes such as methanogenesis, which can lead to methane emissions. The aim of this study was to evaluate methane production and characterize the bacterial and archaeal communities found in HSSFs treating secondary urban wastewater during cold and warm seasons. The pilot system used in this study corresponds to four HSSFs, two planted with Phragmites australis (HSSF−Phr) and two planted with Schoenoplectus californicus (HSSF−Sch), the monitoring was carried out for 1335 days. Removal efficiencies for organic matter (biological and chemical oxygen demand) and total and volatile suspended solids were evaluated in each HSSF. Moreover, biomass from each HSSF was sampled during warm and cold season, and methane productions determined by Specific Methanogenic Activity assays(maximum) (SMAm). In the same samples, the quantification and identification of bacteria and archaea were performed. The results showed that the degradation of organic matter (53–67% BOD5 and 51–62% COD) and suspended solids (85–93%) was not influenced by seasonal conditions or plant species. Potential methane production from HSSF-Sch was between 20 and 51% higher than from HSSF-Phr. Moreover, potential methane production during warm season was 3.4–42% higher than during cold season. The quantification of microorganisms in HSSFs, determined greater development of bacteria (38%) and archaea (50–57%) during the warm season. In addition, the species Schoenoplectus californicus has a larger number of bacteria (4–48%) and archaea (34–43%) than Phragmites australis. The identification of microorganisms evidenced the sequences associated with bacteria belong mainly to Firmicutes (42%), Proteobacteria (33%) and Bacteroidetes (25%). The archaea were represented primarily by Methanosarcinales, specifically Methanosaeta (75%) and Methanosarcina (16%). The community structure of the methanogenic archaea in HSSFs did not change throughout the seasons or plant species.
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29135. 题目: Land use shapes the resistance of the soil microbial community and the C cycling response to drought in a semi-arid area
文章编号: N18082403
期刊: Science of The Total Environment
作者: José Luis Moreno, Irene F. Torres, Carlos García, Rubén López-Mondéjar, Felipe Bastida
更新时间: 2018-08-24
摘要: The aim of this study was to understand the responses of the microbial community of soil under different land uses to drought in a semi-arid Mediterranean area. In a laboratory incubation, soil samples from different land uses (natural forest, drip-irrigated orchard, rain-fed almond tree cultivation and abandoned area) were maintained at 20% and 60% of the WHC. The microbial biomass and potential enzyme activities were determined after four and fifty days of soil incubation. The diversity and composition of the microbial community were studied after 50 days of incubation. The total mineralisation of soil organic C (SOC), as well as, the mineralisation of fresh organic matter (FOM) and the “priming effect” were analysed after addition of 13C-enriched plant tissue. Both land use and drought had significant effects in the soil microbial community, but the effect of land use was stronger than that of drought. The PLFA content (microbial biomass) of the forests soil was greater under drought. After 50 days of soil incubation, the microbial biomass and most of potential enzyme activities of the almond tree and abandoned soil samples were not significantly affected by drought contrary to those in orchard soil. The total and FOM mineralisation were on average lower in soil under drought than under optimal moisture for all land uses. However, the responses of the priming effect to drought were dependent on the land use. Overall, we conclude that the resistance to drought of the soil microbial community from an agroecosystem having a semi-arid climate is strongly influenced by the previous land use.
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29136. 题目: The transformation and migration of selenium in soil under different Eh conditions
文章编号: N18082402
期刊: Journal of Soils and Sediments
作者: Jianxin Fan, Yu Zeng, Jiaoxia Sun
更新时间: 2018-08-24
摘要: Purpose: Soil selenium (Se) sequestration and transformation, which are strongly controlled by soil redox conditions, are critical for understanding the mobility and bioavailability in the environment. Thus, the effect of redox potential on Se transformation was investigated for exploring the release mechanism of Se in soil. Materials and methods: Soils were incubated under anoxic condition in four treatments at room temperature over 56 days, and the soil solution pH, Eh, and Fe and Se concentrations were measured at given reaction time. The sequential extraction and X-ray photoelectron spectroscopy (XPS) were used to obtain the species distribution of Se in soil. High-resolution transmission electron microscopy (HR-TEM) was employed to observe morphology characteristic of soil. Results and discussion: Parts of soil Se can be released into solution, and Se speciation in soil changed during the incubation period. XPS and sequential extraction analyses revealed that the primary speciation of Se in soil was elemental Se, and metallic selenides were formed under aerobic condition. Moreover, XPS and HR-TEM data revealed the crystalline state of iron oxides in soil changed after anoxic incubation, and certain amorphous iron oxides were formed. Conclusions: Se release is activated by short-term incubation, whereas Se can be transformed into less soluble state after long-term incubation. Organic matter takes extremely an important role in Fe oxide reductive dissolution and Se transformation. This study is useful to understand the environmental behaviors of Se and enhance the application of Se fertilizers effectively and safely in Se deficiency area.
29137. 题目: The solid-solution distribution of copper added to soils: influencing factors and models
文章编号: N18082401
期刊: Journal of Soils and Sediments
作者: Xiaoqing Zhang, Jumei Li, Dongpu Wei, Bo Li, Yibing Ma
更新时间: 2018-08-24
摘要: Purpose: A series of empirical and mechanistic geochemical models were developed to describe the solid-solution partitioning of copper (Cu) in typical fresh spiked Chinese soils. Materials and methods: The influence of soil properties on Cu partitioning was assessed in a wide range of soils using multiple regression analysis. Geochemical models (WHAM VI and Visual MINTEQ) and simulation analyses in combination with experimental data (i.e., the bulk of soil properties and Cu contents) were performed in order to provide additional insight into the mechanisms controlling the Cu partitioning. Calculation of soluble Cu contents based on the two models was then simplified and optimized by adjusting input variables, and the calibrated outputs were used to produce reasonable predictions of soluble metal concentrations. Results and discussion: The results of the multiple regression analyses presented in this paper show strong correlations between soluble Cu concentrations and soil Cu concentrations and properties, with adjusted coefficients of determination (Radj2) ranging between 0.84 and 0.91. Soil organic carbon (OC) content was an insignificant factor in most cases, but the active fraction of dissolved organic matter was important in improving model estimates. The best fit of root mean square error (RMSE) varied between 0.42 and 0.77 for the WHAM VI model and between 0.28 and 0.57 for the Visual MINTEQ model across all pH categories. Conclusions: The models presented in this paper are suitable for investigating and simulating Cu solid-solution partitioning in a wide range of Chinese soils.
29138. 题目: Removal of tetracycline from aqueous solution by biochar derived from rice straw
文章编号: N18082313
期刊: Water, Air, & Soil Pollution
作者: Shisuo Fan, Yi Wang, Yang Li, Zhen Wang, Zhengxin Xie, Jun Tang
更新时间: 2018-08-23
摘要: Antibiotic pollution has drawn considerable attention and the removal of antibiotic from water is crucial. In the present study, biochars were produced from rice straw under different pyrolytic temperatures of 300 °C, 500 °C, and 700 °C (RSBC300, RSBC500, and RSBC700, respectively). The biochars were used to remove tetracycline (TC) from aqueous solution and the influence of different experimental conditions on TC removal was investigated. The results showed that the order of adsorption was as follows: RSBC700 > RSBC500 > RSBC300. A pseudo-second-order model and Langmuir isotherm model described the adsorption process of TC on biochars. Maximum adsorption capacity could reach 50.72 mg g−1 at 35 °C based on Langmuir fitting. Initial pH of the solution had little influence on TC removal. The inhibitory effect of Ca2+ on TC removal was greater than that of Na+. High system temperature was beneficial for TC removal. Minerals in RSBC500 affected TC removal and minerals in RSBC300 and RSBC700 had little influence on TC removal. TC removal rate decreased from 58.86 to 27.84% when the minerals were removed from RSBC500. The main mechanism involved in high-temperature biochar and TC adsorption included EDA π-π interactions and electrostatic interactions. Therefore, high-temperature biochar derived from rice straw has the potential to act as an adsorbent to remove tetracycline from aqueous solution.
29139. 题目: Spatio‐temporal variation of the quality, origin and age of particulate organic matter transported by the Yangtze River (Changjiang)
文章编号: N18082312
期刊: Journal of Geophysical Research: Biogeosciences
作者: Ying Wu, Timothy I. Eglinton, Jing Zhang, Daniel B. Montlucon
更新时间: 2018-08-23
摘要: Information on the age dynamics of particulate organic matter (POM) in large river systems is currently sparse, and represents an important knowledge gap in our understanding of the global carbon cycle. Here, we examine variations in organic geochemical characteristics of suspended sediments from the Changjiang (Yangtze River) system collected between 1997 and 2010. Higher POC% values were observed in the middle reach, especially after 2003, and are attributed to the increase of in situ (aquatic) primary production associated with decreased total suspended matter concentrations. Corresponding Δ14C values from, depth profiles taken in 2009 and 2010, indicate spatial and temporal variations in particulate organic carbon (POC) sources within the basin. Two isotopic mass balance approaches were explored to quantitatively apportion different sources of Changjiang POM. Results indicate that contributions of biomass and pre‐aged soil organic matter are dominant regardless of hydrological conditions, with soil‐derived OC comprising 17‐56% of POC based on a Monte Carlo three end‐member mixing model. In contrast, binary mixing model calculations suggest that up to 80% of POC (2009 samples only) derived from biospheric sources. The emplacement of the Three Gorges Dam and resulting trapping of sediment from the upper reach of the watershed resulted in a modification of POM 14C ages in the reservoir. With the resulting decline in sediment load and increase in the proportion of modern POC in lower reach, these changes in POM flux and composition of the Changjiang have significant implications for downstream carbon cycle processes.
29140. 题目: Spatial distribution characteristics of soil organic carbon in subtropical forests of mountain Lushan, China
文章编号: N18082311
期刊: Environmental Monitoring and Assessment
作者: Fazhan Yu, Zhongqi Zhang, Longqian Chen, Jinxin Wang, Zhengping Shen
更新时间: 2018-08-23
摘要: The study on the spatial distribution of forest soil organic carbon (SOC) is of great significance for accurate assessment of carbon storage in forest ecosystems. In the present study, by taking eight kinds of forest soils of Mountain Lushan in the subtropical area as the research object, we studied the spatial distribution characteristics of SOC in this mountainous area. The results showed that the SOC content and SOC density (SOCD) of main forest types in the Mountain Lushan were lower than the national and the world average. The soil layer of Lushan forest was thinner, and the SOC and active SOC (ASOC) contents of different forest types and SOCDs are the highest in the surface soil. SOCD of the topsoil accounts for 32.64–54.03% of the total SOCD in the whole soil profile. Surface litter is an important source of SOC, and the different vegetation types are the important reason for the different spatial distribution of SOC in this area. Soil SOC contents in the high-altitude forest (bamboo forest, deciduous broadleaf forest, Pinus taiwanensis forest, evergreen-deciduous forest, and coniferous-broadleaved mixed forest) were higher than those in the low-altitude forest (evergreen broadleaf forest, shrub, and Pinus massoniana forest). However, the difference in SOC content exhibited at the altitude gradient is significantly lower than that in SOC in the soil profile. This indicates that both soil depth and elevation are the important factors that affected SOC distribution. However, the influence of soil depth on spatial distribution of SOC may be more complex than that of altitude. Vegetation types and soil properties are the main reasons for the large differences of reduction rate in the contents of SOC and ASOC.