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25921. 题目: Removal of 17β-estradiol from Secondary Wastewater Treatment Plant Effluent Using Fe3+-Saturated Montmorillonite
文章编号: N19022413
期刊: Chemosphere
作者: Chao Qin, Chao Shang, Kang Xia
更新时间: 2019-02-24
摘要: Estrogens are of environmental concern because disruptive effect on biological functions at levels as low as ng/L. Wastewater treatment plant effluent is a significant source of estrogens in aquatic environment. Ferric ions (Fe3+)-saturated montmorillonite has been shown to effectively remove 17β-estradiol (βE2), a common estrogen, from pure water by catalyzing formation of insoluble βE2 oligomers on mineral surfaces. We investigated the effects of reaction temperature, dissolved organic matter, pH, and common cations, on Fe3+-saturated montmorillonite-surface catalyzed βE2 polymerization, and the removal of this estrogen from three different secondary wastewater effluents with more complicated matrixes. Highest βE2 removal occurred at near neutral pH and it increased with increasing treatment temperatures. Presence of common cations in the water did not affect the reaction efficiency. Dissolved organic matter at 15 mg C/L slightly lowered the βE2 removal efficiency as compared to that in pure water. Regardless of the source of wastewater effluents, βE2 removal efficiency of ~40% was achieved using the dosage of Fe3+-saturated montmorillonite similar to that tested for the aqueous phases with simpler matrix. Doubling this dosage resulted in removal of ~80% of βE2 from a tested secondary wastewater effluent within 30 min reaction. For wastewater with complex matrixes at the commonly reported βE2 levels which are magnitudes lower than the tested concentration in our study, this dosage would provide sufficient available reaction sites for the surface-catalyzed βE2 polymerization. This study demonstrated that Fe3+-saturated montmorillonite is a promising material for effective removal of phenolic estrogen compounds from domestic wastewater effluents.
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25922. 题目: Iodine budget in forest soils: Influence of environmental conditions and soil physicochemical properties
文章编号: N19022412
期刊: Chemosphere
作者: Marine Roulier, Frédéric Coppin, Maïté Bueno, Manuel Nicolas, Yves Thiry, Claire Della Vedova, Laureline Février, Florence Pannier, Isabelle Le Hécho
更新时间: 2019-02-24
摘要: Due to its longevity, radioisotope 129I is a health concern following potential releases in the environment which raises questions about residence and exposure times relevant for risk assessments. We determined 127I concentrations (as a surrogate for 129I) in a series of French forest soils (i.e. litters, humus and mineral soils) under different vegetation and climate conditions in order to identify the major processes affecting its accumulation and persistence in the soil column. The input fluxes linked to rainfall, throughfall and litterfall were also characterized. Main results obtained showed that: (i) rainfall iodine concentrations probably influenced those of litterfall through absorption by leaves/needles returning to the ground; (ii) throughfall was the major iodine input to soils (mean = 83%), compared to litterfall (mean = 17%); (iii) humus represented a temporary storage of iodine from atmospheric and biomass deposits; (iv) iodine concentrations in soils depended on both the iodine inputs and the soil's ability to retain iodine due to its organic matter, total iron and aluminium concentrations; (v) these soil properties were the main factors influencing the accumulation of iodine in the soil column, resulting in residence times of 419–1756 years; and (vi) the leaching of iodine-containing organic matter dissolved in soil solution may be an important source of labile organic iodine for groundwater and streams.
25923. 题目: Soil organic carbon and soil erosion – Understanding change at the large catchment scale
文章编号: N19022411
期刊: Geoderma
作者: G.R. Hancock, V. Kunkel, T. Wells, Cristina Martinez
更新时间: 2019-02-24
摘要: Soil organic carbon (SOC) is a major soil component. However, there is still much to learn regarding its spatial and temporal distribution as well as how SOC moves through the landscape. Of particular interest is how SOC movement is related to soil erosion and deposition. Here we examine the spatial distribution of SOC over two large (562 and 606 km2) catchments in relation to soil erosion and deposition. We found that the spatial distribution of SOC concentration on average is stable (over an eight year period) for the two study catchments. However, differences were found in SOC when concentrations were compared between samples collected in 2006 and 2014. The environmental tracer caesium-137 (137Cs) was used to assess erosion and deposition patterns across the study catchment and a significant relationship was found between SOC change and erosion and deposition at each sample point. That is, locations with an increase in SOC corresponded with an increase in 137Cs concentration (depositional sites) while locations with a decrease in SOC corresponded with a decrease in 137Cs concentration (erosional sites). A Monte-Carlo assessment confirmed these results. The driver of the SOC change and soil movement corresponds with the largest rainfall event (since 1969) in the area. The results suggest that SOC can be translocated by significant rainfall events. The findings provide insight into how catchments may respond to stronger and more frequent storm events.
25924. 题目: Adsorptive behaviour of palm oil mill sludge biochar pyrolyzed at low temperature for copper and cadmium removal
文章编号: N19022410
期刊: Journal of Environmental Management
作者: Ching Lam Goh, Sumathi Sethupathi, Mohammed JK. Bashir, Waseem Ahmed
更新时间: 2019-02-24
摘要: In this work, the influence of pyrolysis temperature on the physicochemical properties of palm oil mill sludge biochar (POSB) and its adsorption properties towards cadmium (Cd) and copper (Cu) was investigated. Characterization experiments suggested that POSBs’ surface functional groups play the major role in the adsorption process. POSB pyrolyzed at 400 °C showed the best characteristics for Cu and Cd removal. Adsorption study indicated that contact time and shaking speed enhances the adsorption capacity of POSB. It was affirmed that pH adjustment is not necessary for POSB to adsorb Cu and Cd. Mechanism studies fitted well with Langmuir and Pseudo-Second Order model. Thermodynamic parameters indicated that the adsorption was spontaneous, endothermic and correspond to chemical adsorption. The highest uptakes of Cu and Cd were recorded at 48.8 mg/g and 46.2 mg/g respectively. This work verifies that the temperature used for palm oil mill sludge (POS) pyrolysis and adsorption condition played the most prominent role in Cu and Cd removal from aqueous solutions.
25925. 题目: Large-scale integrated assessment of soil carbon and organic matter-related nitrogen fluxes in Saxony (Germany)
文章编号: N19022409
期刊: Journal of Environmental Management
作者: Felix Witing, Michael Gebel, Hans-Joachim Kurzer, Holm Friese, Uwe Franko
更新时间: 2019-02-24
摘要: Changes in land-use, agricultural management and climate affect the turnover and storage of organic carbon in soils (SOC) as well as the nitrogen mobilization from soil organic matter (SOM), with potential side effects on nitrogen availability and leaching. When addressing the requests for increased carbon storage in soil as well as for the reduction of nitrogen losses, integrated approaches on regional scales are required that take into account the actual changes in agricultural management and climate. This study investigated the arable land (7345 km2) of Saxony (Germany) with regard to the following: (1) the trends of SOC storage and organic matter-related nitrogen fluxes, including their subregional and annual dynamics, (2) changes in the carbon input to arable soils and the turnover of organic matter, and (3) the contribution of different drivers (climate, crop production and fertilization, tillage system) to the simulated SOM changes for the period 1998–2014 on a 500 m grid. The model CANDY carbon balance (CCB) was specifically adapted for large-scale simulations of SOM turnover to link spatial data on soils and climate with regional statistics on agricultural management. This new ‘regional mode’ of CCB has been validated using data from 391 plots across different European locations. The initial SOC levels for Saxony assumed steady state conditions at the beginning of the simulation period and have been validated using data from 667 monitoring sites. The results showed an increase in the SOC stocks of the arable soils of Saxony of 785 × 103 t C (1.24‰ annually) during the simulation period. At the same time, the model simulated an average increase in organic nitrogen stored in SOM of approximately 7.5 kg N ha−1 a−1, with considerable differences between individual years and subregions. Both the increase in carbon inputs to soil (+8%) and the reduction of carbon turnover rates (−10%) had positive effects on SOC storage. While the increased use of conservation tillage was the most important driver for the overall increase in SOM storage in Saxony, climate variability and crop production and fertilization had the largest effect on its annual dynamics.
25926. 题目: Application of a hybrid gravity-driven membrane filtration and dissolved ozone flotation (MDOF) process for wastewater reclamation and membrane fouling mitigation
文章编号: N19022408
期刊: Journal of Environmental Sciences
作者: Xin Jin, Wei Wang, Shuai Wang, Pengkang Jin, Xiaochang C. Wang, Wushou Zhang, Weijun An, Yong Wang
更新时间: 2019-02-24
摘要: This study proposed a novel membrane filtration and dissolved ozone flotation integrated (MDOF) process and tested it at pilot scale. Membrane filtration in the MDOF process was operated in gravity-driven mode, and required no backwashing, flushing, or chemical cleaning. Because ozone was added in the MDOF process, ozonation, coagulation, and membrane filtration could occur in a single reactor. Moreover, in situ ozonation occurred in the MDOF process, which differs from the conventional pre-ozonation membrane filtration process. Significant enhancement of turbidity removal was further achieved through the addition of membrane filtration. Membrane fouling was mitigated in the MDOF process compared to the MDAF process. In situ ozonation in the MDOF process decreased the fluorescence intensity and transformed the high MW dissolved organics into small MW compounds. For the fouling layer, the extracellular polymeric substance (EPS) contents and cake layer morphology were analyzed. The results indicated that the contents of EPS decreased. Furthermore, a thinner and more loosely structured cake layer formed in the MDOF process. Because coagulation and ozonation occurred simultaneously in a single reactor, the generation of hydroxyl radicals was enhanced through the catalytic effect of Al-based coagulants on ozone decomposition, which further alleviated membrane fouling in the MDOF process.
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25927. 题目: Regulation of soil phosphorus cycling in grasslands by shrubs
文章编号: N19022407
期刊: Soil Biology and Biochemistry
作者: Xiao-Li Gao, Xiao Gang Li, Ling Zhao, Yakov Kuzyakov
更新时间: 2019-02-24
摘要: The globally expanding colonization of grasslands by shrubs increases soil organic carbon and nitrogen, but the effects of shrubs on phosphorus (P) cycling have been rarely studied. We compared P contents in roots and soil fractions, phosphatase activity in the 1 m profile, and in situ net P mineralization between shrubby Potentilla fruticosa patches and grassy interspaces in grazed shrubby meadows at three representative sites on the eastern Tibetan Plateau. The P uptake of P. fruticosa exceeded 1 m soil depth, whereas grasses acquired P mainly within the upper 0.6 m. The P contents in shoots, aboveground litter and roots under P. fruticosa were greater than those under grasses. Litter P stock under the shrubs was 4–8 times higher than that under grasses and the root P stock doubled compared to that in grass areas. P. fruticosa generally increased the organic P (OP) content in the topsoil but decreased inorganic P (IP) in the subsoil. Phosphorus availability increased in the topsoil but decreased in the subsoil under the shrubs compared to grasses. Microbial biomass P (MBP), the activities of acid and alkaline phosphatases, and OP lability were all greater in the 1 m soil under P. fruticosa than grasses, leading to faster P mineralization and the P turnover under the shrubs. In the 1 m soil, P. fruticosa increased MBP and OP stocks but decreased IP and available P stocks. The larger and deeply distributed root system of P. fruticosa improved its P uptake ability especially from the subsoil. The subsequent greater organic matter input through litter fall and root turnover under P. fruticosa fed a larger microbial biomass that synthesized more microbial-derived OP in the topsoil. We concluded that shrubs increase the biological (plant and microbial) P transformation in the soil, the P uplift in the profile, and P cycling in shrubby grassland ecosystems. Such mechanisms structuring spatial heterogeneity of P content, transformation, turnover and fluxes are common in shrubby grasslands worldwide.
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25928. 题目: Adsorption and desorption of phenanthrene by magnetic graphene nanomaterials from water: Roles of pH, heavy metal ions and natural organic matter
文章编号: N19022406
期刊: Chemical Engineering Journal
作者: Dan Huang, Baile Xu, Jizi Wu, Philip C. Brookes, Jianming Xu
更新时间: 2019-02-24
摘要: The adsorption of phenanthrene onto magnetic graphene oxide (MGO), magnetic chemically-reduced graphene (MCRG) and magnetic annealing-reduced graphene (MARG) were compared to examine their unique adsorption properties. The effects of environmental factors on the adsorption-desorption properties of phenanthrene e.g. pH, heavy metal ions, and natural organic matter were also investigated. MCRG had the highest adsorption capacity for phenanthrene, mainly due to the larger surface area and pore volume, and numerous wrinkles of MCRG. The π−π interaction was the predominant adsorption mechanism of MCRG. Coexisting Cd(II) and As(V) had minor impact on phenanthrene adsorption by MCRG, while the adsorption capacity of phenanthrene decreased considerably with coexisting humic acids. Phenanthrene caused desorption hysteresis, which was largely suppressed by humic acids. The desorption hysteresis was ascribed to the entrapment of phenanthrene molecules derived from the generation of closed interstitial spaces caused by the rearrangement of graphene nanosheets onto MCRG. Steric hindrance was much larger with adsorbed humic acid molecules. Our findings on magnetic graphene nanomaterials (MGNs) and related adsorption-desorption properties highlight their potential applications as efficient adsorbents and their possible risks in natural aquatic environments.
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25929. 题目: Experimental process parameters optimization and in-depth product characterizations for teak sawdust pyrolysis
文章编号: N19022405
期刊: Waste Management
作者: Goutam Kishore Gupta, Pavan Kumar Gupta, Monoj Kumar Mondal
更新时间: 2019-02-24
摘要: Pyrolysis is an efficient thermochemical route to obtain biofuels in the form of bio-oil, biochar and pyrolytic gas from the processing of biomass. Pyrolysis experiments were performed with teak sawdust to determine the yield and main characteristics of solid, liquid and gaseous products. Experiments were carried out in the temperature range of 400–700 °C in 100 °C intervals, nitrogen flow rate of 150–250 mL/min, packed bed height in between 2 and 8 cm and particle size in between 0.18 and 0.60 mm. The maximum bio-oil and biochar yield were observed at 600 °C (48.8%) and 400 °C (37.42%), respectively. Physical properties (viscosity, density, carbon residue, pH and HHV) of bio-oil were determined and the chemical properties were investigated using FTIR and GC–MS. Further, biochar was characterized with proximate, ultimate, HHV, FTIR, SEM-EDX, BET surface area and XRD analysis. Non-condensable gases coming out during pyrolysis were analyzed using gas chromatography and amount of H2, CH4, CO and CO2 were determined. According to characterization results, bio-oil can be used as biofuel after up gradation or as source of valuable chemicals, biochar can be utilized as solid fuel or seems to be suitable in waste stream purification as it has very high BET surface area. In addition, pyrolytic gases have significant amount of methane and hydrogen that provides good combustion properties.
25930. 题目: Effects of pyrolysis temperature on nitrate-nitrogen (NO3−-N) and bromate (BrO3−) adsorption onto date palm biochar
文章编号: N19022404
期刊: Journal of Environmental Management
作者: Abdulaziz S. Alsewaileh, Adel R. Usman, Mohammad I. Al-Wabel
更新时间: 2019-02-24
摘要: Biochars (BCs) produced through biomass pyrolysis are highly efficient adsorbents for retaining dissolved cations in soil and water. However, their anionic sorption characteristics are unclear and depend on the feedstock used and the pyrolysis temperature. Herein, the adsorption of nitrate-nitrogen (NO3−-N) and bromate (BrO3−) anions onto date palm biochar was evaluated by considering the pyrolysis temperature in relation with the initial concentrations, initial pH, and adsorbent dose. Biochars from date palm rachis were produced at 300 °C (BC300) and 700 °C (BC700). The latter exhibited the highest adsorption efficiency of NO3−-N from aqueous solutions at an initial pH of 2, which was 25.8%–44.3% (at an adsorbent dose of 4 g L−1) and 47.0%–73.0% (at an adsorbent dose of 10 g L−1). In contrast, BC300 adsorbed BrO3− with an adsorption efficiency of 19.3%, 14.5%, 14.9%, and 13.6% at initial added concentrations of 5, 10, 15, and 20 μg L−1, respectively. However, BC700 showed zero adsorption for BrO3−. The results also showed that the non-linear models of Langmuir and/or Freundlich for NO3−-N and BrO3− adsorption described the adsorption data better in most cases. It could be concluded that high pyrolysis temperature BC are suitable for adsorbing NO3−-N, and low pyrolysis temperature BC may be used to adsorb BrO3−.
25931. 题目: Source, spatial distribution, and toxicity potential of Polycyclic Aromatic Hydrocarbons in sediments from Iran's environmentally hot zones, the Persian Gulf
文章编号: N19022403
期刊: Ecotoxicology and Environmental Safety
作者: Vahid Aghadadashi, Ali Mehdinia, Alireza Riyahi Bakhtiari, Jahangard Mohammadi, Masoud Moradi
更新时间: 2019-02-24
摘要: Surface sediments, sampled from Iranian coast of the Persian Gulf (n = 134), were analyzed in order to track spatial distribution of PAHs and their related eco-hazards. The levels of PAHs were in the range of 1.98–814 ng g−1 dw and the region was lowly to moderately polluted. The profile of PAHs was mainly composed of 2,3-ring chemicals and suggested a local source of PAHs and relatively fresh inputs. Statistical analysis and molecular fingerprints proposed that the basin receives PAHs from multiple origins including petrogenic and pyrogenic (traffic and auto emission) ones. Spatial distribution of organic matter and fine fraction of the sediments had a horizontally increasing trend in the studied basin. ∑16PAHs showed significant positive correlation with TOC and fine fraction (p < 0.05) and the spatial deposition of ∑16PAHs followed the spatial trends of TOC and fine fraction. Spatial mapping techniques confirmed that Pars Special Economic Energy Zone (PSEEZ) is the hot zone of PAH pollution. A combination of source availability, finer sediments, and great organic matter levels were the main effective factors that highlighted the deposition of PAHs in the PSEEZ. The Nayband Bay, as the Iran’s first national marine Park, possibly received PAHs from its adjacent zone, the PSEEZ. On the other hand, low organic matter and sandy nature of the Nayband Bay was not suitable for effective sequestration of PAHs. Thus, the biota of Nayband Park was encountering with relatively severe multiple eco-hazards due to both ecological and economic factors.
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25932. 题目: Effects of maize straw and its biochar application on organic and humic carbon in water-stable aggregates of a Mollisol in Northeast China: A five-year field experiment
文章编号: N19022402
期刊: Soil and Tillage Research
作者: Jinjing Zhang, Yuxuan Wei, Jianzhao Liu, Jingchao Yuan, Yao Liang, Jun Ren, Hongguang Cai
更新时间: 2019-02-24
摘要: In agricultural ecosystems, one optimized crop residue management practice, i.e., incorporating biochar produced from crop residues via pyrolysis to the soil, is considered a promising technology for mitigating climate change and improving soil quality. However, the potential mechanisms are still not well known. In this study, a five-year (2011–2015) field experiment in a Mollisol of Northeast China that included four treatments, i.e., CK (no fertilizer), NPK (mineral nitrogen, phosphorus and potassium fertilizers), NPKS (NPK plus maize straw) and NPKB (NPK plus maize straw-derived biochar), was conducted to evaluate the effects of maize straw and its derived biochar application on the following: 1) the size distribution and water stability of soil aggregates; 2) the concentrations of organic and humic carbon (C) in bulk soil and water-stable aggregate fractions; and 3) the chemical compositions of organic and humic C in water-stable aggregate fractions. Compared with the CK and NPK treatments, the proportion of macroaggregates (>0.25 mm) [mainly large macroaggregates (>2 mm)] increased whereas the proportions of microaggregates (0.25–0.053 mm) and silt + clay fractions (<0.053 mm) decreased in NPKS and NPKB treatments, resulting in the mean weight diameter (MWD) of soil aggregates being higher under NPKS and NPKB treatments than under CK and NPK treatments. The concentrations of organic and humic C in bulk soil and aggregate fractions were also generally higher under NPKS and NPKB treatments than under CK and NPK treatments. The treatment effects were more apparent for NPKB than for NPKS. With respect to other treatments, the NPKB treatment significantly increased the ratios of macroaggregate- to microaggregate-associated organic C as well as humin C. The solid-state 13C cross-polarization magic-angle-spinning (CPMAS) NMR spectra of small macroaggregates (2–0.25 mm) and its humic acid fraction showed that the NPKS treatment did not alter the proportions of the C functional groups. In contrast, the NPKB treatment clearly decreased the proportions of alkyl C and O-alkyl C but increased the proportion of aromatic C, resulting in the alkyl C/O-alkyl C and hydrophobic C/hydrophilic C ratios being higher whereas the aliphatic C/aromatic C ratio was lower under NPKB than under other treatments. These findings indicate that the application of maize straw biochar enhanced soil aggregate stability and aggregate-associated organic and humic C concentrations. Biochar C was preferentially incorporated into macroaggregates and its humin fraction with respect to microaggregates. Moreover, the molecular structure of small macroaggregates and its HA fraction became more stable, hydrophobic and aromatic. Therefore, physical protection through organic C in aggregate fractions, physical-chemical protection through the encapsulation of humic C within aggregate fractions, and physical-biochemical protection through recalcitrant alkyl C and aromatic C within aggregate fractions may be the primary mechanisms for C preservation in biochar-amended soil. Our results suggested that maize straw biochar application was an effective strategy based on the comprehensive goal of mitigating climate change and improving soil quality in Mollisols of Northeast China.
25933. 题目: Pyrogenic carbon content and dynamics in top and subsoil of French forests
文章编号: N19022401
期刊: Soil Biology and Biochemistry
作者: Laure Soucémarianadin, Moritz Reisser, Lauric Cécillon, Pierre Barré, Manuel Nicolas, Samuel Abiven
更新时间: 2019-02-24
摘要: Pyrogenic carbon (PyC) may leave the soil surface where it is deposited, either through degradation, lateral transport or transfer within the profile. However, PyC has been seldom measured in the subsoil. We estimated the quantity and molecular composition of PyC in the topsoil and subsoil of 22 French forests with diverse soil types and vegetation cover. While the absolute PyC content decreased with depth, its proportion to the soil organic carbon remained constant or tended to increase. The benzene polycarboxylic acids pattern indicated that more condensed structures were found in the subsoil. Our results show that PyC transfers through the soil profile, probably as soluble fraction, and tends to accumulate in the subsoil, specifically in podzolic soils.
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25934. 题目: Sources and transformations of anthropogenic nitrogen in the highly disturbed Huai River Basin, Eastern China
文章编号: N19022317
期刊: Environmental Science and Pollution Research
作者: Pei Ma, Shuaixia Liu, Qibiao Yu, Xinyan Li, Xinqing Han
更新时间: 2019-02-23
摘要: Due to serious nitrogen pollution in the Huai River, Eastern China, nitrogenous concentrations and dual stable isotopes (δ15N and δ18O) were measured to ascertain the sources and transformation of nitrogen in the Shaying River, the largest and most polluted tributary of the Huai River during the summer and winter seasons. Total nitrogen (TN), NO3−, and NH4+ were significantly higher in winter, with values of 7.84 ± 3.44 mg L−1, 2.31 ± 0.81 mg L−1, and 3.00 ± 2.24 mg L−1, respectively, while the highest nitrogen compounds occurred in the Jialu River, one of the tributaries of the Shaying River, in both summer and winter. Isotope characteristics of nitrate reveal that manure and sewage were the principal nitrate sources in both summer (62.44 ± 19.66%) and winter (67.33 ± 15.45%), followed by soil organic nitrogen, with 24.94 ± 15.52% in summer and 26.33 ± 9.45% in winter. Values of δ15N-suspended particulate nitrogen (SPN) ranged from 0.78 to 13.51%, revealing that point source from industrial and domestic sewage accounted for the largest input to SPN at most sites, whereas soil organic nitrogen and agricultural fertilizers were found in the Jialu River in both sampling periods. Point sources from septic/manure and household waste were the main contributors to ammonium in most river water samples in both summer and winter; most wastewater discharged into the river was untreated, which was one of the main reasons for the high level of ammonium in winter. Nitrogen pollution and the dams had an effect on N transformation in the river. Significant assimilation of NH4+ and aerobic denitrification competed for NH4+, resulting in the weakness of nitrification in the summer. Denitrification was also an important process of nitrate removal during the summer, whereas nitrification was a key N transformation process in the river in the winter time. To reduce nitrogen pollution and improve water quality, greater effort should be focused on the management of sources from urban input as well as on the improvement in sewage treatment.
25935. 题目: Nitrous oxide from streams and rivers: A review of primary biogeochemical pathways and environmental variables
文章编号: N19022316
期刊: Earth-Science Reviews
作者: Annika M. Quick, W. Jeffery Reeder, Tiffany B. Farrell, Daniele Tonina, Kevin P. Feris, Shawn G. Benner
更新时间: 2019-02-23
摘要: Atmospheric concentrations of the powerful greenhouse gas nitrous oxide (N2O) have increased dramatically over the last 100 years, and part of these emissions come from streams and rivers. N2O production has been more carefully studied in soils, but runoff of reactive nitrogen, likely from fertilizer, influences lotic N2O emissions. N2O production and consumption are strongly microbially mediated and mostly involve oxidation and reduction of the reactive nitrogen species ammonia, nitrate, and nitrite. Of the four main pathways leading to N2O production in soils and sediments, incomplete denitrification is likely the globally dominant N2O generating pathway and is favored by elevated nitrate concentrations, suboxic conditions, and sufficient organic carbon to promote reduction. The two pathways that oxidize ammonia, nitrifier denitrification and nitrification, are favored with higher concentrations of dissolved oxygen and ammonia. It is often difficult to distinguish these two pathways in field settings, but most evidence suggests that nitrifier-denitrification is likely the globally more significant of the two. The fourth reaction pathway is dissimilatory nitrate reduction to ammonia (DNRA), in which N2O may be produced from intermediate nitrite. This pathway is more recently discovered, and its global relevance remains uncertain.The key variables influencing N2O cycling, concentrations of the primary reactants (nitrate and ammonia), organic carbon, and dissolved oxygen (DO), may vary temporally with season and time of day. Increasing nitrate and ammonia generally result in higher N2O production. Elevated carbon availability generally promotes denitrification. However, N2O yield is generally higher when carbon is less available or less reactive. Efforts to quantify N2O in lotic settings include mostly studies of N2O dissolved in or emitted from surface water, with fewer studies of N2O produced or emitted from sediments. With some exceptions and limits, N2O emissions are generally positively correlated with nitrate concentration (and in some cases, ammonia concentration). Most studies observe more N2O emissions with low DO. Lotic N2O emissions were generally higher in the warmer months and at night. Most studies assume a denitrification source for N2O, except in the case of high DO and NH4+, in which nitrification is assumed.Lotic N2O production and consumption may take place in the hyporheic zone along groundwater flow paths and in the water column of streams and rivers. Because microbial nitrogen processing requires substrate, influx of reactants, appropriate redox conditions, and intermediate residence times, the hyporheic zone is likely the site of most N2O production. However, high rates of N2O production may also occur associated with suspended sediments in turbid streams and rivers. Models that combine hydromorphogical and chemical variables are most likely to provide the best predictions of N2O emissions. Such models and some observations suggest that N2O emissions decrease downstream as sedimentary processes (likely denitrification) decrease relative to processes in the surface water (likely nitrification). Downstream sites could have large N2O emissions, however, due to inputs of nitrate or ammonia. Better quantification of lotic N2O processing will inform the emission factors incorporated into greenhouse gas budgets. Both quantification and mitigation of N2O emissions will benefit from future research that more closely examines the biogeochemical pathways and physical settings for N2O production and consumption.
25936. 题目: Insight into the binding properties of carbamazepine onto dissolved organic matter using spectroscopic techniques during grassy swale treatment
文章编号: N19022315
期刊: Ecotoxicology and Environmental Safety
作者: Donghai Yuan, Haotian Wang, Yechen An, Xujing Guo, Liansheng He
更新时间: 2019-02-23
摘要: Carbamazepine (CBZ) is a worldwide anti-epileptic drug, whose fate and migration can be greatly influenced by contact with dissolved organic matter (DOM). The properties of DOM in road runoff can be greatly changed by grassy swale (GS) treatment, which influences the complexation of CBZ with DOM. Spectroscopic techniques were employed to explore the different binding properties between CBZ and DOM, and to understand the migration and biogeochemistry of CBZ. The two-dimensional correlation spectroscopy (2D-COS)demonstrated that effluent DOM displayed more binding sites for CBZ than influent DOM, and the binding sequencing of CBZ with DOM fluorophores can be greatly influenced by GS treatment. The results also suggest that protein-like materials exhibit higher log KM values than other fluorescent components, indicating that fluorescent protein-like materials play a crucial role in the biogeochemical behavior of CBZ. Meanwhile, the log KM values showed a remarkable increase after GS treatment. GS treatment can also remove most fluorescent DOM, reducing the risk of CBZ in the water environment.
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25937. 题目: Reduction of Cu(II) and simultaneous production of acetate from inorganic carbon by Serratia Marcescens biofilms and plankton cells in microbial electrosynthesis systems
文章编号: N19022314
期刊: Science of The Total Environment
作者: Yitong Qian, Liping Huang, Peng Zhou, Fuping Tian, Gianluca Li Puma
更新时间: 2019-02-23
摘要: Simultaneous Cu(II) reduction (6.42 ± 0.02 mg/L/h), acetate production (1.13 ± 0.02 mg/L/h) from inorganic carbon (i.e., CO2 sequestration), and hydrogen evolution (0.0315 ± 0.0005 m3/m3/d) were achieved in a Serratia marcescens Q1 catalyzed microbial electrosynthesis system (MES). The biofilms released increasing amounts of extracellular polymeric substances (EPS) with a higher compositional diversity and stronger Cu(II) complexation, compared to the plankton cells, at higher Cu(II) concentrations (up to 80 mg/L) and circuital currents (cathodic potential of −900 mV vs. standard hydrogen electrode (SHE)). Moreover, the biofilms reduced Cu(II) to Cu(0) more effectively than the plankton cells. At Cu(II) concentrations below 80 mg/L, the dehydrogenase activity in the biofilms was higher than in the plankton cells, and increased with circuital current, which was converse to the lower activities of catalase (CAT), superoxide dismutase (SOD) and antioxidative glutathione (GSH) in the biofilms than the plankton cells, although all these physiological activities were positively correlated with the concentration of Cu(II). This is the first study that evaluates the EPS constituents and the physiological activities of the biofilms and the plankton cells in the MESs, that favors the production of acetate from CO2 sequestration and the simultaneous reduction of Cu(II) from organics-barren waters contaminated with heavy metals.
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25938. 题目: Sources of dissolved organic carbon (DOC) in a mixed land use catchment (Exe, UK)
文章编号: N19022313
期刊: Science of The Total Environment
作者: J.P. Ritson, J.K. Croft, J.M. Clark, R.E. Brazier, M.R. Templeton, D. Smith, N.J.D. Graham
更新时间: 2019-02-23
摘要: Many catchment management schemes in the UK have focussed on peatland restoration to improve ecosystem services such as carbon sequestration, water quality and biodiversity. The effect of these schemes on dissolved organic carbon (DOC) flux is critical in understanding peatland carbon budgets as well as the implications for drinking water treatment. In many catchments, however, peatland areas are not the only source of DOC, meaning that their significance at the full catchment scale is unclear. In this paper we have evaluated the importance of different land uses as sources of DOC by combining three datasets obtained from the Exe catchment, UK. The first dataset comprises a weekly monitoring record at three sites for six years, the second, a monthly monitoring record of 25 sites in the same catchment for one year, and the third, an assessment of DOC export from litter and soil carbon stocks. Our results suggest that DOC concentration significantly increased from the peaty headwaters to the mixed land-use areas (ANOVA F = 12.52, p < 0.001, df = 2), leading to higher flux estimates at the downstream sites. We present evidence for three possible explanations: firstly, that poor sampling of high flows may lead to underestimation of DOC flux, second, that there are significant sources of DOC besides the peatland headwaters, and finally, that biological- and photo-degradation decreases the influence of upstream DOC sources. Our results provide evidence both for the targeting of catchment management in peatland areas as well as the need to consider DOC from agricultural and forested areas of the catchment.
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25939. 题目: National estimation of soil organic carbon storage potential for arable soils: A data-driven approach coupled with carbon-landscape zones
文章编号: N19022312
期刊: Science of The Total Environment
作者: Songchao Chen, Dominique Arrouays, Denis A. Angers, Claire Chenu, Pierre Barré, Manuel P. Martin, Nicolas P.A. Saby, Christian Walter
更新时间: 2019-02-23
摘要: Soil organic carbon (SOC) is important for its contributions to agricultural production, food security, and ecosystem services. Increasing SOC stocks can contribute to mitigate climate change by transferring atmospheric CO2 into long-lived soil carbon pools. The launch of the 4 per 1000 initiative has resulted in an increased interest in developing methods to quantity the additional SOC that can be stored in soil under different management options. In this work, we have made a first attempt to estimate SOC storage potential of arable soils using a data-driven approach based on the French National Soil Monitoring Network. The data-driven approach was used to determine the maximum SOC stocks of arable soils for France. We first defined different carbon-landscape zones (CLZs) using clustering analysis. We then computed estimates of the highest possible values using percentile of 0.8, 0.85, 0.9 and 0.95 of the measured SOC stocks within these CLZs. The SOC storage potential was calculated as the difference between the maximum SOC stocks and current SOC stocks for topsoil and subsoil. The percentile used to determine highest possible SOC had a large influence on the estimates of French national SOC storage potential. When the percentile increased from 0.8 to 0.95, the national SOC storage potential increased by two to three-fold, from 336 to 1020 Mt for topsoil and from 165 to 433 Mt for subsoil, suggesting a high sensitivity of this approach to the selected percentile. Nevertheless, we argue that this approach can offer advantages from an operational point of view, as it enables to set targets of SOC storage taking into account both policy makers' and farmers' considerations about their feasibility. Robustness of the estimates should be further assessed using complementary approaches such as mechanistic modelling.
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25940. 题目: Assessment on applicability of common source tracking tools for particulate organic matter in controlled end member mixing experiments
文章编号: N19022311
期刊: Science of The Total Environment
作者: Morgane Derrien, Kyung-Hoon Shin, Jin Hur
更新时间: 2019-02-23
摘要: In this study, ideal mixing behaviors of the three commonly-used source tracking tools, which include fluorescence spectroscopy, stable isotope ratios, and lipid biomarkers, were evaluated in controlled particular organic matter (POM) mixtures of two contrasting end members e.g., soil and algae. In parallel, three different extraction methods based on water (WEOM) and two alkaline solutions were compared to identify the preferential pre-treatment option that leads to a good performance of the spectroscopic source tracking indices on the dissolved organic matter (DOM) extracted from the POM. Based on three evaluation criteria concerning the linearity of the relationships, the discrimination sensitivity, and the conservative mixing behavior of fourteen tested indices, the fluorescence proxies such as the relative distribution of the fluorescence components and the modified fluorescence index YFI of the WEOM were found to be reliable and robust indices for POM source tracking. The carbon stable isotope ratios of the POM samples exhibited an ideal mixing behavior even after the DOM extraction, while the biomarkers of sterols/stanols did not present a good linear and conservative behavior at similar conditions. In addition, the WEOM was identified as the preferred extraction method for the application of spectroscopic indices for POM source discrimination. This study provides a guideline to select the optimum indices for the POM source discrimination via the end member mixing analysis.
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