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29141. 题目: Liming effects on soil pH and crop yield depend on lime material type, application method and rate, and crop species: a global meta-analysis
文章编号: N18082310
期刊: Journal of Soils and Sediments
作者: Yuan Li, Song Cui, Scott X. Chang, Qingping Zhang
更新时间: 2018-08-23
摘要: Purpose: The aim of this meta-analysis was to investigate the interactive effects of environmental and managerial factors on soil pH and crop yield related to liming across different cropping systems on a global scale. Materials and methods: This study examined the effects of liming rate, lime application method, and liming material type on various soil chemical properties and crop yield based on data collected from 175 published studies worldwide since 1980. Results and discussion: The most important variables that drive changes in soil pH and crop yield were liming rate and crop species, respectively. Soil conditions, such as initial soil organic matter and soil pH, were more important for increasing soil pH in field-based experiments, while lime material type and application method were more important for improving crop yield. To effectively neutralize soil acidity, the optimum liming duration, rate, and material type were < 3 years, 3–6 Mg ha−1, and Ca (OH)2, respectively. Averaged across different crop species, the application of CaO, CaCO3, Ca (OH)2, and CaMg (CO3)2 increased yield by 13.2, 34.3, 29.2, and 66.5%, respectively. Conclusions: This meta-analysis will help design liming management strategies to ameliorate soil acidity and thus improve crop yield in agroecosystems.
29142. 题目: Halogen Radical Oxidants in Natural and Engineered Aquatic Systems
文章编号: N18082309
期刊: Environmental Science & Technology
作者: Ke Zhang, Kimberly M. Parker
更新时间: 2018-08-23
摘要: Photochemical reactions contribute to the transformation of contaminants and biogeochemically important substrates in environmental aquatic systems. Recent research has demonstrated that halogen radicals (e.g., Cl•, Br•, Cl2•–, BrCl•–, Br2•–) impact photochemical processes in sunlit estuarine and coastal waters rich in halides (e.g., chloride, Cl–, and bromide, Br–). In addition, halogen radicals participate in contaminant degradation in some engineered processes, including chlorine photolysis for drinking water treatment and several radical-based processes for brine and wastewater treatment. Halogen radicals react selectively with substrates (with bimolecular rate constants spanning several orders of magnitude) and via several potential chemical mechanisms. Consequently, their role in photochemical processes remains challenging to assess. This review presents an integrative analysis of the chemistry of halogen radicals and their contribution to aquatic photochemistry in sunlit surface waters and engineered treatment systems. We evaluate existing data on the generation, speciation, and reactivity of halogen radicals, as well as experimental and computational approaches used to obtain this data. By evaluating existing data and identifying major uncertainties, this review provides a basis to assess the impact of halogen radicals on photochemical processes in both saline surface waters and engineered treatment systems.
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29143. 题目: The fate of dichloroacetonitrile in UV/Cl2 and UV/H2O2 processes: implications on potable water reuse
文章编号: N18082308
期刊: Environmental Science: Water Research & Technology
作者: Ran Yin, Zhuozhi Zhong, Li Ling, Chii Shang
更新时间: 2018-08-23
摘要: This study investigated the fate of DCAN in UV/Cl2 and UV/H2O2 processes under the conditions relevant to potable water reuse (e.g., two pH values and three oxidant dosages). At pH 6 and an oxidant dosage of 500 μM, the degradation of DCAN in the UV/Cl2 process was attributed to UV photolysis (4.5%), HO−-assisted hydrolysis (10.5%), nucleophilic attack by ClO− (32.2%), and oxidation by radicals (i.e., HO˙ and Cl˙) (52.8%), while that in the UV/H2O2 process was mainly attributed to HO2− (32%) and HO˙ (48%). In both processes, the DCAN degradation rates were higher with increasing solution pH from 5 to 6, because the increased HO−-assisted hydrolysis and nucleophilic attack of DCAN surpassed the decreased radical oxidation of DCAN. The DCAN degradation was enhanced with increasing chlorine or H2O2 dosage from 100 to 1000 μM, mainly due to the increased contribution from the nucleophilic attack. DCAN was mostly transformed into dichloroacetic acid (DCAA) through different pathways in the two processes. At the same pH and oxidant dosage conditions, the degradation rates of DCAN in the UV/Cl2 process were higher than those in the UV/H2O2 process, due to the higher nucleophilic attack rates and radical oxidation rates in the former process. The cost of degrading 90% of DCAN using the UV/Cl2 process is about 1/8 of that using the UV/H2O2 process, making the UV/Cl2 process a more cost-effective UV-AOP in DCAN abatement for potable water reuse.
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29144. 题目: Potential formation of mutagenicity by low pressure-UV/H2O2 during the treatment of nitrate-rich source waters
文章编号: N18082307
期刊: Environmental Science: Water Research & Technology
作者: S. Semitsoglou-Tsiapou, M. R. Templeton, N. J. D. Graham, S. Mandal, L. Hernández Leal, J. C. Kruithof
更新时间: 2018-08-23
摘要: Mutagenicity formation by low pressure (LP)-UV/H2O2 treatment of nitrate-rich water containing natural organic matter (NOM) was investigated. Laboratory-grade water samples spiked with either Pony Lake NOM or Suwannee River NOM (4 mg L−1 in both cases) and nitrate (50 mg L−1) were irradiated with UV fluences of 0, 1500 and 2000 mJ cm−2 and a H2O2 dose of 15 mg L−1 and tested for mutagenicity with the Ames II assay. LP-UV photolysis of nitrate in the presence of Pony Lake NOM caused a significant increase in the Ames II assay response and low concentrations of nitrite (0.08–0.09 mg NO2− L−1) and nitrophenols (0.014–0.046 μg L−1) were detected. Suwannee River NOM produced the same nitrite levels but no significant responses in the Ames II assay were observed. Additionally, samples collected from a drinking water treatment plant in the UK using LP-UV/H2O2 treatment were analysed with the Ames II assay. LC-OCD fractionation and SUVA measurements were performed to observe any changes in the properties of NOM. Significant differences in the mutagenicity response were observed between the treatment steps as well as between the two sampling periods. However, with respect to standard thresholds, none of the samples were found to be mutagenic towards the Salmonella typhimurium strain TA98 used.
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29145. 题目: Enhanced enzymatic digestibility of mixed wood sawdust by lignin modification with naphthol derivatives during dilute acid pretreatment
文章编号: N18082306
期刊: Bioresource Technology
作者: Chenhuan Lai, Bo Yang, Juan He, Caoxing Huang, Xin Li, Xiangyang Song, Qiang Yong
更新时间: 2018-08-23
摘要: Effects of the addition of 2-naphthol and 2-naphthol-7-sulfonate on the dilute acid pretreatment of mixed wood sawdust were investigated, respectively. Compared to 2-naphthol, 2-naphtnol-7-sulfonate was more effective to enhance delignification and facilitate the enzymatic hydrolysis. The 72 h hydrolysis yield was improved by 47.8% for 2-naphthol-7-sulfone, while only 9.1% was observed for 2-naphthol. The surface charges, enzyme adsorption, and cellulose accessibility of dilute acid pretreated substrates with or without naphthol derivatives were examined. The improved enzymatic hydrolysis by adding 2-naphthol-7-sulfonate was ascribed to the higher negative surface charges, the lower enzyme non-productive binding, and the higher cellulose accessibility of pretreated substrates. Additionally, the HSQC NMR and 31P NMR analysis were carried out on both decomposed lignins and residual bulk lignins. It indicated that the addition of the naphthol derivatives during pretreatment could suppress the lignin repolymerization, which further mitigated the inhibition of residual lignins on enzymatic hydrolysis.
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29146. 题目: Effect of water-washing of wheat straw and hydrothermal temperature on its hydrochar evolution and combustion properties
文章编号: N18082305
期刊: Bioresource Technology
作者: Qiulin Ma, Lujia Han, Guangqun Huang
更新时间: 2018-08-23
摘要: In order to upgrade wheat straw, hydrothermal treatment at 160–240 °C was investigated. Meanwhile, the influence of temperature and leaching on the fuel’s physicochemical and combustion properties were explored. A temperature of 180–220 °C was found to benefit the generation of hydrochar, with solid and energy yields of at least 57.3% and 69.9%, respectively. When temperature increased to 160 °C, hemicellulose was hydrolyzed and this led to the formation of carbon microspheres. The diameter of the carbon microspheres reached 0.05–0.7 μm. Hydrochars obtained at 160, 180, and 200 °C exhibited better combustion performance with higher comprehensive combustibility index value. While leaching heavily impacted the hydrochar derived at 160 °C and increased its activation energy (178 kJ/mol) above those obtained for treatment at 180 °C (164 kJ/mol) and 200 °C (169 kJ/mol). Overall, the recommended hydrothermal temperature for production of fuel from wheat straw is 180–200 °C.
29147. 题目: The influence of pH, co-existing ions, ionic strength, and temperature on the adsorption and reduction of hexavalent chromium by undissolved humic acid
文章编号: N18082304
期刊: Chemosphere
作者: Samuel Barnie, Jia Zhang, Hui Wang, Huilin Yin, Honghan Chen
更新时间: 2018-08-23
摘要: The retention of Cr(VI) in subsurface environment is highly dependent on humic acid (HA), however, the undissolved form is poorly investigated, the amount of which can be of two magnitude higher compared with the dissolved one in soils and sediments. In this study, the effects of time, initial concentration, pH, ionic strength, ion species and temperature on the adsorption and reduction respective processes by undissolved self-extracted peat soil HA from Northeast China (EHA) and from Sigma Aldrich (CHA) were investigated by batch experiments. Cr(VI) removal rates by EHA were higher than CHA and the maximum Cr(VI) removal amount for EHA and CHA were 0.77 (±0.01) and 0.61 (±0.02) mmol/g. Of these, 98% and 54% were reduced to Cr(III) by EHA and CHA respectively, which were related to the phenolic group content of HA. With time, the adsorbed Cr(VI) on HA increased to a maximum level (equilibrium) beyond which Cr(VI) reduction dominated the removal process. Cr(VI) adsorption and reduction by undissolved HA increased as pH decreased. Co-existing ion species had varying effect on Cr(VI) adsorption and indirectly on reduction especially divalent cations which was suggestive of cation bridging between Cr anions and ionized carboxyl group of HA. The positive effect of ionic strength (Ca2+) on Cr(VI) adsorption through complexation corroborated the cation bridge effect of divalent cations. Temperature increased both Cr(VI) adsorption (complexation) and reduction with enhancing reduction rate constants and partitioning. ΔHo, ΔSo, and ΔG⁰ parameters showed that Cr(VI) adsorption and reduction processes were endothermic, irreversible and spontaneous.
29148. 题目: Selective preservation among bacterial alkyl glycerol ether lipid structures during long term oxic and anoxic incubation
文章编号: N18082303
期刊: Organic Geochemistry
作者: Arnauld Vinçon-Laugier, Cristiana Cravo-Laureau, Vincent Grossi
更新时间: 2018-08-23
摘要: Bacterial mono- and dialkyl glycerol ether lipids (MAGEs and DAGEs) are potential powerful lipid biomarkers whose respective diagenetic fate still needs to be precisely assessed. To do so, the lipid content of cultures of an anaerobic bacterium synthetizing both MAGEs and DAGEs was analyzed at different growth stages and after long-term incubation under aerobic or anaerobic conditions. The proportions of the different lipid classes (fatty acids, MAGEs and DAGEs) as well as their structural distribution did not significantly vary during anaerobic growth under optimal conditions until the stationary phase. Long-term exposure to oxygen (up to 480 days) induced the preferential degradation of fatty acids and MAGEs relative to DAGEs and of sn-1 relative to sn-2 positional isomers of MAGEs. The degradation of fatty acids and MAGEs appeared slower under anaerobic conditions and no specific structures appeared preferentially degraded. All DAGE structures were very well preserved whatever the redox conditions and the time of incubation considered (480 days and 13 years under oxic and anoxic conditions, respectively). The results highlight the excellent diagenetic stability of DAGEs and the much lower potential of preservation of MAGEs, warranting caution for an eventual use of those latter compounds as tracers of environmental or microbial community changes.
29149. 题目: Multiple sulfur isotopes (δ34S, Δ33S) of organic sulfur and pyrite from Late Cretaceous to Early Eocene oil shales in Jordan
文章编号: N18082302
期刊: Organic Geochemistry
作者: Katharina Siedenberg, Harald Strauss, Olaf Podlaha, Sander van den Boorn
更新时间: 2018-08-23
摘要: We present the first multiple sulfur isotope study (32S, 33S, 34S, 36S) of bulk kerogen sulfur (KS) and disulfides (’chromium-reducible sulfur’, CRS) from the oil shale of the Umm Rijam Chert-Limestone and Muwaqqar Chalk Marl Formation, Jordan (Late Cretaceous to Early Eocene, appr. 50 to 70 Ma). Analysis of the sulfur isotopic composition of KS (δ34SKS) shows values ranging from 0.3 to 17.9 ‰, which are 34S-enriched compared to the δ34SCRS ranging from -23.5 to -3.7 ‰. Values for CRS and KS are significantly 34S-depleted compared to seawater sulfate sulfur which suggests a major input of early-diagenetic, microbially-generated sulfide. A minor contribution of assimilated seawater sulfate to KS is assumed. The 34S-enrichment of KS compared to CRS can be partly explained by (1) sulfide oxidation to intermediate sulfur species prior to its incorporation into organic material, by (2) fractionations during organic sulfur generation, as well as by (3) a post-depositional timing of formation. Additionally, we hypothesize, based on parallel depth trends of maturity parameters (e.g., vitrinite reflectance) and δ34SCRS and δ34SKS values, that the sulfur isotopic compositions were influenced by thermal maturation (catagenesis). We suggest that the CRS pool comprises a contribution of sulfide released during the thermal decomposition of KS. Overall, our study highlights the importance of organic sulfur in sulfur isotopic studies and the potential of multiple sulfur isotope analyses in maturated sedimentary successions.
29150. 题目: Effect of continuous light on leaf wax isotope ratios in Betula nana and Eriophorum vaginatum: Implications for Arctic paleoclimate reconstructions
文章编号: N18082301
期刊: Organic Geochemistry
作者: William C. Daniels, Yongsong Huang, James M. Russell, Anne E. Giblin
更新时间: 2018-08-23
摘要: Reconstructions of climate using leaf wax D/H ratios (δDwax) require accounting for the apparent isotopic fractionation (εapp) between plant source water and waxes. There have been conflicting publications on whether plants in the Arctic growing under 24-hour continuous light fractionate less than temperate and tropical plants. In this study, we examine the effect of diurnal light (DL) versus 24-hour continuous light (CL) on the isotopic composition of leaf n-alkanes and n-acids in greenhouse experiments using two common Arctic plants (Eriophorum vaginatum, or tussock cottongrass, and Betula nana, or dwarf birch). For E. vaginatum, the δDwax values of various wax homologues were 5-11‰ more positive for CL plants relative to their DL counterparts, whereas for B. nana, CL waxes were 3-24‰ more negative, suggesting that daylight length is not a unifying control on leaf wax D/H ratios of Arctic plants. The δ13Cwax of B. nana was more negative for plants grown in continuous light compared to diurnal light, reflecting lower water-use efficiency associated with prolonged stomatal opening in the CL treatment. We modeled the impact of increasing stomatal conductance and effective flow path lengths (mimicking variable leaf morphologies) on the isotopic composition of leaf waters (δDlw) and find that variations in leaf-water enrichment may explain the variable δDwax responses seen between E. vaginatum and B. nana. We suggest that between-species differences in the δDlw response to light, and differences in the utilization of stored carbohydrates were important for governing δDwax. Our greenhouse results suggest that Arctic plant leaf waxes do not consistently display reduced εapp values as a result of 24-hour day light, providing additional support for field observations.
29151. 题目: Multi-sensor fusion for the determination of several soil properties in the Yangtze River Delta, China
文章编号: N18082206
期刊: European Journal of Soil Science
作者: D. Xu, R. Zhao, S. Li, S. Chen, Q. Jiang, L. Zhou, Z. Shi
更新时间: 2018-08-22
摘要: Soil organic matter (SOM), total nitrogen (TN), available nitrogen (AN), available phosphorus (AP), available potassium (AK) and pH are key chemical properties for evaluating soil fertility and quality. This study involved the integration of four soil sensors, visible near–infrared (vis–NIR) spectrometer, mid‐infrared (mid‐IR) spectrometer, portable X‐ray fluorescence (PXRF) analyser and laser‐induced breakdown spectroscopy (LIBS), to achieve rapid measurement of these soil properties. A genetic algorithm and partial least‐squares regression (GA–PLSR) was used to select characteristic bands to reduce data redundancy. We then calibrated models from three aspects: models using partial least‐squares regression (PLSR) based on single sensor data, models using PLSR based on fused sensor data, involving data combined from the four sensors into a new dataset to create a data fusion (DF) model and models with Bayesian model averaging (BMA) based on prediction results of fused sensor, involving prediction results combined from the four sensors into a new dataset to form the BMA model. The results showed the following. (i) For the single sensor, the predictive performance decreased as follows: mid‐IR > vis–NIR > LIBS > PXRF. (ii) Compared with the single sensor approach, the DF approach slightly improved or even reduced prediction accuracy and caused a large amount of redundancy. We suggest that this approach is not able to improve predictive ability. (iii) The BMA approach achieved the best prediction for the six soil properties. Our findings suggest that model averaging of vis–NIR, mid‐IR and LIBS could be a reliable and stable approach for the fast measurement of soil properties. This article is protected by copyright. All rights reserved.
29152. 题目: Chlorine Dioxide—Pollutant Transformation and Formation of Hypochlorous Acid as a Secondary Oxidant
文章编号: N18082205
期刊: Environmental Science & Technology
作者: Jens Terhalle, Pascal Kaiser, Mischa Jütte, Johanna Buss, Sermin Yasar, Robert Marks, Helmut Uhlmann, Torsten C. Schmidt, Holger V. Lutze
更新时间: 2018-08-22
摘要: Chlorine dioxide (ClO2) has been used as a disinfectant in water treatment for a long time, and its use for micropollutant abatement in wastewater has recently been suggested. Surprisingly, a mechanistic understanding of ClO2 reactions in (waste)water matrices is largely lacking. The present study contributes to this mechanistic understanding by performing a detailed investigation of ClO2 reactions with organic matter using phenol as a surrogate for reactive phenolic moieties. A concept for indirectly determining HOCl using 2- and 4-bromophenol was developed. The reaction of phenol with ClO2 formed chlorite (62 ± 4% per ClO2 consumed) and hypochlorous acid (HOCl) (42 ± 3% per ClO2 consumed). The addition of ClO2 to wastewater (5 × 10–5 M ClO2) resulted in 40% atenolol and 47% metoprolol transformation. The presence of the selective HOCl scavenger glycine largely diminished their transformation, indicating that atenolol and metoprolol were transformed by a fast reaction with HOCl (e.g., k (atenolol + HOCl) = 3.5 × 104 M–1 s–1) that formed in ClO2 reactions with the wastewater matrix. The formation of HOCl may thus increase the number of transformable micropollutants in ClO2 applications. However, chlorine related byproducts may also be formed.
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29153. 题目: Lateral Marsh Edge Erosion as a Source of Sediments for Vertical Marsh Accretion
文章编号: N18082204
期刊: Journal of Geophysical Research: Biogeosciences
作者: Charles S. Hopkinson, James T. Morris, Sergio Fagherazzi, Wilfred M. Wollheim, Peter A. Raymond
更新时间: 2018-08-22
摘要: With sea level rise accelerating and sediment inputs to the coast declining worldwide, there is concern that tidal wetlands will drown. To better understand this concern, sources of sediment contributing to marsh elevation gain were computed for Plum Island Sound estuary, MA, USA. We quantified input of sediment from rivers and erosion of marsh edges. Maintaining elevation relative to the recent sea level rise rate of 2.8 mm yr−1 requires input of 32,299 MT yr−1 of sediment. The input from watersheds is only 3,210 MT yr−1. Marsh edge erosion, based on a comparison of 2005 and 2011 LiDAR data, provides 10,032 MT yr−1. This level of erosion is met by <0.1% of total marsh area eroded annually. Mass balance suggests that 19,070 MT yr−1 should be of tidal flat or oceanic origin. The estuarine distribution of 14C and 13C isotopes of suspended particulate organic carbon confirms the resuspension of ancient marsh peat from marsh edge erosion, and the vertical distribution of 14C‐humin material in marsh sediment is indicative of the deposition of ancient organic carbon on the marsh platform. High resuspension rates in the estuarine water column are sufficient to meet marsh accretionary needs. Marsh edge erosion provides an important fraction of the material needed for marsh accretion. Because of limited sediment supply and sea level rise, the marsh platform maintains elevation at the expense of total marsh area.
29154. 题目: Cropland Abandonment Enhances Soil Inorganic Nitrogen Retention and Carbon Stock in China: A Meta‐Analysis
文章编号: N18082203
期刊: Land Degradation & Development
作者: Dashuan Tian, Yangzhou Xiang, Bingxue Wang, Meiling Li, Yanshu Liu, Jinsong Wang, Zhaolei Li, Shuli Niu
更新时间: 2018-08-22
摘要: Transforming cropland into natural ecosystem is an effective approach to increase soil organic carbon (SOC) and nitrogen sequestration. However, we know little about large‐scale response patterns of SOC, soil inorganic nitrogen (SIN) and their interactions over long time of ecosystem restoration. Here, we conducted a meta‐analysis to examine changes in SOC, SIN and their relationship along 50 year's ecosystem development from cropland transformation in China's ‘Grain‐to‐Green Program'. Our results showed that SOC and SIN were consistently enhanced by 57% and 35% with transformation. Similar with SOC, SIN had higher response magnitudes when cropland was restored to forests (47%) than to shrublands (36%) and grasslands (24%). Both SOC and SIN response ratios showed a quadratic relationship with precipitation. Moreover, we found a strong linear relationship (R2=0.36) between SOC and SIN response ratio, with the slope indicating a 0.43% increase in SIN per 1% of increasing SOC. This SIN retention capacity (the slope) significantly increased with restoration time, but reduced with precipitation, temperature and initial SOC. Restored forest had a lower SIN retention capacity than shrubland and grassland. Overall, this study represents the first to regionally uncover SIN retention mechanism with increasing SOC during ecosystem development. It suggests that ecosystem restoration will contribute more to relieving serious environmental problems (i.e. N leaching and N2O emission) by enhancing SIN retention in China's ‘Grain‐to‐Green' Program.
29155. 题目: Modeling rhizosphere carbon and nitrogen cycling in Eucalyptus plantation soil
文章编号: N18082202
期刊: Biogeosciences
作者: Rafael Vasconcelos Valadares, Júlio César Lima Neves, Maurício Dutra Costa, Philip James Smethurst, Luiz Alexandre Peternelli, Guilherme Luiz Jesus, Reinaldo Bertola Cantarutti, and Ivo Ribeiro Silva
更新时间: 2018-08-22
摘要: Vigorous Eucalyptus plantations produce 105 to 106kmha−1 of fine roots that probably increase carbon (C) and nitrogen (N) cycling in rhizosphere soil. However, the quantitative importance of rhizosphere priming is still unknown for most ecosystems, including these plantations. Therefore, the objective of this work was to propose and evaluate a mechanistic model for the prediction of rhizosphere C and N cycling in Eucalyptus plantations. The potential importance of the priming effect was estimated for a typical Eucalyptus plantation in Brazil. The process-based model (ForPRAN – Forest Plantation Rhizosphere Available Nitrogen) predicts the change in rhizosphere C and N cycling resulting from root growth and consists of two modules: (1) fine-root growth and (2) C and N rhizosphere cycling. The model describes a series of soil biological processes: root growth, rhizodeposition, microbial uptake, enzymatic synthesis, depolymerization of soil organic matter, microbial respiration, N mineralization, N immobilization, microbial death, microbial emigration and immigration, and soil organic matter (SOM) formation. Model performance was quantitatively and qualitatively satisfactory when compared to observed data in the literature. Input variables with the most influence on rhizosphere N mineralization were (in order of decreasing importance) root diameter > rhizosphere thickness > soil temperature > clay concentration. The priming effect in a typical Eucalyptus plantation producing 42m3ha−1yr−1 of shoot biomass, with assumed losses of 40% of total N mineralized, was estimated to be 24.6% of plantation N demand (shoot+roots+litter). The rhizosphere cycling model should be considered for adaptation to other forestry and agricultural production models where the inclusion of such processes offers the potential for improved model performance.
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29156. 题目: Performance of thin-film composite hollow fiber nanofiltration for the removal of dissolved Mn, Fe and NOM from domestic groundwater supplies
文章编号: N18082201
期刊: Water Research
作者: Maryam Haddad, Takashi Ohkame, Pierre R. Bérubé, Benoit Barbeau
更新时间: 2018-08-22
摘要: Groundwater (GW) is one of the most abundant water resource and around 1.5 billion people rely on GW as their main water supply. Manganese (Mn) and iron (Fe) are very common GW contaminants. Even though their presence is considered mainly as an organoleptic and operational nuisance, water with elevated Mn content may also lead to adverse health impacts. Amongst the most common treatment processes currently used to treat domestic GW supplies: catalytic filtration may lead to Mn leaching if improperly maintained; while ion exchange consumes a considerable amount of salt and produces a brine waste which pollutes the environment. Thus, it is proposed to design a simple, yet robust treatment system which can be implemented in small/remote communities or even domestic applications. To this end, the main objective of this investigation was to assess the potential application of novel outside-in sulfonated polyethersulfone thin-film composite hollow fiber nanofiltration (HFNF) membranes to remove dissolved Mn, Fe and natural organic matter (NOM) from domestic GW supplies. Of particular interest was the impact of GW matrix on performance of the HFNF membranes. Our experimental findings demonstrated that, in absence of hardness and the cumulative throughput of 1.9 L/m2, above 90 of Mn, Fe and NOM were retained by the examined HFNF membranes (MWCO 200 Da) regardless of their initial concentrations in the feed solution (250–1000 μ g/L). In contrast, increasing the hardness level reduced the removal of Mn and Fe ions. XPS analysis revealed that the surface properties of the HFNF membranes were altered when the membranes were exposed to calcium and magnesium salts. These observations were attributed to the propensity for Ca and Mg ions to bind to the sulfonic groups present on the surface of the HFNF membranes which, subsequently, weakens rejection by charge exclusion. On the other hand, in the absence of GW hardness, charge exclusion was mainly responsible for rejection of dissolved Mn and Fe. It was also found that GW hardness had no marked impact on the NOM rejection as the later was mostly removed by size exclusion.
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29157. 题目: Organic Carbon Processing During Transport Through Boreal Inland Waters: Particles as Important Sites
文章编号: N18082116
期刊: Journal of Geophysical Research: Biogeosciences
作者: Katrin Attermeyer, Núria Catalán, Karolina Einarsdottir, Anna Freixa, Marloes Groeneveld, Jeffrey A. Hawkes, Jonas Bergquist, Lars J. Tranvik
更新时间: 2018-08-21
摘要: The degradation and transformation of organic carbon (C) in inland waters result in significant CO2 emissions from inland waters. Even though most of the C in inland waters occurs as dissolved organic carbon (DOC), studies on particulate organic carbon (POC) and how it influences the overall reactivity of organic C in transport are still scarce. We sampled 30 aquatic ecosystems following an aquatic continuum including peat surface waters, streams, rivers, and lakes. We report DOC and POC degradation rates, relate degradation patterns to environmental data across these systems, and present qualitative changes in dissolved organic matter and particulate organic matter during degradation. Microbial degradation rates of POC were approximately 15 times higher compared to degradation of DOC, with POC half‐lives of only 17 ± 3 (mean ± SE) days across all sampled aquatic ecosystems. Rapid POC decay was accompanied by a shift in particulate C:N ratios, whereas dissolved organic matter composition did not change at the time scale of incubations. The faster degradation of the POC implies a constant replenishment to sustain natural POC concentrations. We suggest that degradation of organic matter transported through the inland water continuum might occur to a large extent via transition of DOC into more rapidly cycling POC in nature, for example, triggered by light. In this way, particles would be a dominant pool of organic C processing across the boreal aquatic continuum, partially sustained by replenishment via flocculation of DOC.
29158. 题目: Multi‐sensor fusion for the determination of several soil properties in the Yangtze River Delta, China
文章编号: N18082115
期刊: European Journal of Soil Science
作者: D. Xu, R. Zhao, S. Li, S. Chen, Q. Jiang, L. Zhou, Z. Shi
更新时间: 2018-08-21
摘要: Soil organic matter (SOM), total nitrogen (TN), available nitrogen (AN), available phosphorus (AP), available potassium (AK) and pH are key chemical properties for evaluating soil fertility and quality. This study involved the integration of four soil sensors, visible near–infrared (vis–NIR) spectrometer, mid‐infrared (mid‐IR) spectrometer, portable X‐ray fluorescence (PXRF) analyser and laser‐induced breakdown spectroscopy (LIBS), to achieve rapid measurement of these soil properties. A genetic algorithm and partial least‐squares regression (GA–PLSR) was used to select characteristic bands to reduce data redundancy. We then calibrated models from three aspects: models using partial least‐squares regression (PLSR) based on single sensor data, models using PLSR based on fused sensor data, involving data combined from the four sensors into a new dataset to create a data fusion (DF) model and models with Bayesian model averaging (BMA) based on prediction results of fused sensor, involving prediction results combined from the four sensors into a new dataset to form the BMA model. The results showed the following. (i) For the single sensor, the predictive performance decreased as follows: mid‐IR > vis–NIR > LIBS > PXRF. (ii) Compared with the single sensor approach, the DF approach slightly improved or even reduced prediction accuracy and caused a large amount of redundancy. We suggest that this approach is not able to improve predictive ability. (iii) The BMA approach achieved the best prediction for the six soil properties. Our findings suggest that model averaging of vis–NIR, mid‐IR and LIBS could be a reliable and stable approach for the fast measurement of soil properties.
29159. 题目: Sorption and desorption characteristics of anionic surfactants to soil sediments
文章编号: N18082114
期刊: Chemosphere
作者: Ping Zhang, Yuan Liu, Zhejun Li, Amy T. Kan, Mason B. Tomson
更新时间: 2018-08-21
摘要: Surfactants are important environmental chemicals due to their extensive domestic and industrial applications, such as subsurface organic pollution remediation and enhanced oil recovery. However, the interaction of surfactants with subsurface material particularly the desorption behavior of surfactants is less understood. Surfactant desorption is essential to control the fate and transport of surfactants as well as organic pollutants. In this study, the sorption and desorption of linear sodium dodecylbenzene sulfonate (SDBS) and sodium hexadecyl diphenyl oxide disulfonate (DPDS) with two types of soil sediment samples are compared. Sorption of surfactants can be modeled by hydrophobic sorption. Less DPDS sorption is observed at a higher aqueous concentration, which is attributed to the competition between surfactant micelles and sediment organic matter for DPDS sorption. A significant fraction of the sorbed surfactants resists desorption, and this is not a result of surfactant precipitation or desorption kinetics. Surfactant desorption behavior is similar to the irreversible desorption of hydrocarbons from soil with only half of the resistant phase surfactant being readily extracted by heated solvent extraction. The sorption/desorption data are interpreted with a molecular topology and irreversible sorption model. The knowledge of this study can be useful in understanding the environmental fate and transport of these common anionic surfactants. The methodology developed in this study can be expanded to study the sorptive nature of a wider range of surfactants in the environment.
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29160. 题目: Nitrogen removal in domestic wastewater. Effect of nitrate recycling and COD/N ratio
文章编号: N18082113
期刊: Chemosphere
作者: L. Pelaz, A. Gómez, A. Letona, G. Garralón, M. Fdz-Polanco
更新时间: 2018-08-21
摘要: A denitrification/nitrification pilot plant was designed, built and put into operation, treating the effluent of an anaerobic reactor. The operation of the plant examined the effect of the nitrate recycling and the COD/N ratio on the nitrogen and the remaining organic matter removal at 18 °C. The system consisted of a two-stage treatment process: anoxic and aerobic. The hydraulic retention time (HRT) of the system was 1 h for the anoxic bioreactor and 2 h for the aerobic one. The increase in the nitrate recycling ratio did not cause a significant improvement in the nitrogen removal due to the insufficient carbon source. The wastewater to be treated had a C/N ratio of 1.1 showing a lack of organic carbon. The addition of methanol was a key point in the denitrification process used as a model for the traditional wastewater by-pass in the WWTP. The maximum nitrogen and organic matter removal (87.1% and 96%, respectively) was achieved with a nitrate recycling ratio of 600% and a C/N of 8.25, adjusted by methanol addition.
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