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25901. 题目: Production of Biochar from Food Waste and its Application for Phenol Removal from Aqueous Solution
文章编号: N19022612
期刊: Water, Air, & Soil Pollution
作者: Chang-Gu Lee, Seung-Hee Hong, Seong-Gu Hong, Jae-Woo Choi, Seong-Jik Park
更新时间: 2019-02-26
摘要: Deriving biochar from biowaste facilitates its reuse and application for environmental protection. This study addresses the adsorption of phenol onto food waste–based biochar (FWC). Phenol adsorption on FWC was affected by pyrolysis temperature, and the highest adsorption capacity was found at a temperature of 700 °C (FWC700). The characteristics of the biochar including morphology, surface area, functional groups, and elemental composition were analyzed. Additional batch experiments were performed to evaluate the phenol adsorption on FWC700 under various experimental conditions such as contact time, initial concentration, reaction temperature, solution pH, adsorbent dose, and presence of competing ions. The adsorption capacity of phenol decreased gradually from 9.79 ± 0.04 to 8.86 ± 0.06 mg/g between solution pH of 3 and 11. Copper sulfate showed the greatest interference on phenol adsorption to FWC in aqueous solution. Phenol removal at different contact times followed pseudo-second-order kinetics, and the Langmuir isotherm model provided the best fit of the equilibrium data with a maximum adsorption capacity of 14.61 ± 1.38 mg/g. Adsorption of phenol increased with increasing temperature from 15 to 35 °C, and thermodynamic analysis indicated an endothermic and spontaneous nature of the adsorption process. Biochar derived from food waste can be used as bio-adsorbent for the removal of phenol from aqueous solution.

25902. 题目: Formation, Characteristics, and Applications of Environmentally Persistent Free Radicals in Biochars: A Review
文章编号: N19022611
期刊: Bioresource Technology
作者: Xiuxiu Ruan, Yuqing Sun, Weimeng Du, Yuyuan Tang, Qiang Liu, Zhanying Zhang, William Doherty, Ray L. Frost, Guangren Qian, Daniel C.W. Tsang
更新时间: 2019-02-26
摘要: Due to abundant biomass and eco-friendliness, biochar is exemplified as one of the most promising candidates to mediate the degradation of environmental contaminants. Recently, environmentally persistent free radicals (EPFRs) have been detected in biochars, which can activate S₂O₈^2- or H₂O₂ to generate reactive oxygen species for effective degradation of organic and inorganic contaminants. Comprehending the formation mechanisms of EPFRs in biochars and their interactions with contaminants is indispensable to further develop their environmental applications, e.g., direct and indirect EPFR-mediated removal of organics/inorganics by biochars. With reference to the information of EPFRs in environmental matrices, this article critically reviews the formation mechanisms, characteristics, interactions, and environmental applications of EPFRs in biochars. Synthesis conditions and loading of metals/organics are considered as key parameters controlling their concentrations, types, and activities. This review provides new and important insights into the fate and emerging applications of surface-bound EPFRs in biochars.
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25903. 题目: N-doped biochar synthesized by a facile ball-milling method for enhanced sorption of CO₂ and reactive red
文章编号: N19022610
期刊: Chemical Engineering Journal
作者: Xiaoyun Xu, Yulin Zheng, Bin Gao, Xinde Cao
更新时间: 2019-02-26
摘要: Doping of nitrogen (N) on carbon materials often requires complicated synthetic steps or specific machinery. In this study, N-doped biochar was successfully synthesized by simply ball milling pristine biochar with ammonium hydroxide. The content and species of N in the resulting N-doped biochars were carefully characterized, the formation mechanisms of N-related groups were illustrated, and their applications in CO₂ uptake and reactive red removal were evaluated. Most of N introduced to biochar was loaded on its surface in forms of -NH₂ and C≡N, resulting from the dehydration of -COOH and –OH. Biochars produced at 450°C were doped with more N on the surface (XPS, 2.41%-2.65%) than those produced at 600°C (XPS, 1.18%-1.82%) because the content of O-containing functional groups in biochar decreases with increasing pyrolysis temperature. The basic properties of N-related groups enhanced the sorption performance of biochar to both acidic CO₂ and anionic reactive red. For example, the CO₂ uptake of the N-doped, 450°C hickory biochar was 31.6%-55.2% higher than the corresponding pristine and ball-milled biochars. The maximum sorption capacity of the N-doped, 600°C bagasse biochar to reactive red was about 3.66-16.2 times of the corresponding biochars without N doping. This paper provides an alternative and facile approach to prepare N-doped biochar that can be extended to other carbon materials to meet the specific needs in different applications, especially adsorption.
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25904. 题目: Bench-scale assessment of the formation and control of disinfection byproducts from human endogenous organic precursors in swimming pools
文章编号: N19022609
期刊: Chemosphere
作者: Yi Liu, Chia-Yang Chen, Gen-Shuh Wang
更新时间: 2019-02-26
摘要: In this study, a bench-scale system was utilized to assess the disinfection byproduct (DBP) formation from human endogenous organic matter. Perspiration and urine, constituting the main organic substances in swimming pools, were selected to represent the major human endogenous organics. Results revealed that the continuous input of body fluids into the reactor led to rapid accumulation of endogenous organic matter, which contributed to high concentrations of DBPs in the swimming pool. The increase in nonpurgeable organic carbon concentration from the perspiration precursor was lower than that from urine during the operation. Moreover, the accumulation of swimmers' body fluids leads to increased DBP precursors, as well as increased chlorine demand and DBPs formation in swimming pool water. The concentration of the trihalomethanes (THMs) and haloacetic acids (HAAs) consistently increased during the reaction. More THMs were generated in urine solution, whereas more HAAs were found in perspiration solution. To improve the water quality in swimming pools, ozonation, UV/Chlorine, and UV/H₂O₂ treatments were evaluated for their efficacy in reducing the DBP precursors. Results revealed that all of the three treatment processes can degrade the DBP precursors in perspiration and urine, eventually decreasing the DBP concentrations. However, only the UV/H₂O₂ treatment can decrease the formation of DBPs in perspiration and urine. In addition, the results revealed that UV/Chlorine and UV/H₂O₂ treatments should be operated for a sufficient contact time to prevent the increased production of DBP precursors in water at the early stage of the treatment.
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25905. 题目: Wide-spread limitation of soil organic nitrogen transformations by substrate availability and not by extracellular enzyme content
文章编号: N19022608
期刊: Soil Biology and Biochemistry
作者: Lisa Noll, Shasha Zhang, Qing Zheng, Yuntao Hu, Wolfgang Wanek
更新时间: 2019-02-26
摘要: Proteins constitute the single largest soil organic nitrogen (SON) reservoir and its decomposition drives terrestrial N availability. Protein cleavage by extracellular enzymes is the rate limiting step in the soil organic N cycle and can be controlled by extracellular enzyme production or protein availability/stabilization in soil. Both controls can be affected by geology and land use, as well as be vulnerable to changes in soil temperature and moisture/O₂. To explore major controls of soil gross protein depolymerization we sampled six soils from two soil parent materials (calcareous and silicate), where each soil type included three land uses (cropland, pasture and forest). Soil samples were subjected to three temperature treatments (5, 15, 25 °C at 60% water-holding capacity (WHC) and aerobic conditions) or three soil moisture/O₂ treatments (30 and 60% WHC at 21% O₂, 90% WHC at 1% O₂, at 20 °C) in short-term experiments. Samples were incubated for one day in the temperature experiment and for one week in the moisture/O₂ experiment. Gross protein depolymerization rates were measured by a novel ¹⁵N isotope pool dilution approach. The low temperature sensitivity of gross protein depolymerization, the lack of relationship with protease activity and strong effects of soil texture and pH demonstrate that this process is constrained by organo-mineral associations and not by soil enzyme content. This also became apparent from the inverse effects in calcareous and silicate soils caused by water saturation/O₂ limitation. We highlight that the specific soil mineralogy influenced the response of gross depolymerization rates to water saturation/O₂ limitation, causing (I) increasing gross depolymerization rates due to release of adsorbed proteins by reductive dissolution of Fe- and Mn-oxyhydroxides in calcareous soils and (II) decreasing gross depolymerization rates due to mobilization of coagulating and toxic Al³⁺ compounds in silicate soils.

25906. 题目: Unraveling the water states of waste-activated sludge through transverse spin-spin relaxation time of low-field NMR
文章编号: N19022607
期刊: Water Research
作者: Boran Wu, Kun Zhou, Yunpeng He, Xiaoli Chai, Xiaohu Dai
更新时间: 2019-02-26
摘要: The physical states of water are crucial for the dewatering efficiency of waste-activated sludge (WAS). However, to date, there is still lack of promising methods for the distinct differentiation of water states in colloidal microbial aggregates. This study proposed that the transverse spin-spin relaxation time (T₂) distribution of low-field nuclear magnetic resonance (NMR) could be a useful tool to unravel the occurrence state of water in WAS. Due to the different interaction strengths of protons with the surrounding environment, the three water states with different T₂ ranges were identified. The water trapped on the surface of solid phase could be classified as vicinal water; interstitial water refers to the water physically trapped in bio-floc by steric hindrance or adsorption; and the water that is least affected by solid compositions is categorized as moderately mobile water. The potential ways of typical conditioning approaches for shifting water states were also investigated. The removal of hydrophilic compounds in extracellular polymeric substances (EPS) and surface charge neutralization were both found to be possible ways to influence the percentage of vicinal water (Pearson correlation coefficient R_p > 0.950, p-value ≤ 0.05). The disintegration or compaction of colloidal microbial aggregates could induce the transformation of interstitial water into moderately mobile water. All the above results are believed to deepen the mechanism insights into the differentiation and interactive transformation of water states in bio-floc of WAS.
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25907. 题目: Land-based dissolved organic nitrogen dynamics and bioavailability in Jiaozhou Bay, China
文章编号: N19022606
期刊: Estuarine, Coastal and Shelf Science
作者: Keqiang Li, Cuicui Liu, Yunpeng Ma, Xiulin Wang
更新时间: 2019-02-26
摘要: Dissolved organic matter (DOM) samples from forestry, livestock breeding, urban domestic and agricultural sources around Jiaozhou Bay were incubated in seawater to examine DOM dynamics and bioavailability, which is the availability of DOM to degradation by microbes. The fluorescence signals of protein- and humic-like compounds were used as a proxy for bioavailable and refractory materials, respectively, whereas the evolution of SUVA₂₅₄, dissolved organic nitrogen (DON) and dissolved organic carbon (DOC) concentrations were used to discuss bioavailability. The high bioavailability DON sources were from livestock breeding and urban domestic sources, with no significant difference, followed by agricultural and forestry sources, with respective degradation rate constants of 0.36 ± 0.01 (mean ± SD) d⁻¹, 0.32 ± 0.03 d⁻¹, 0.22 ± 0.04 d⁻¹, and 0.18 ± 0.01 d⁻¹, and with bioavailable DON (BDON%) representing 70% ± 10%, 67% ± 7%, 62% ± 8% and 37% ± 12% of the total DON, respectively. The turnover times of BDON were 3–6 days, far less than the flushing time of Jiaozhou Bay. Approximately 66% of land-based DON may contribute to DIN by microbial re-mineralization in Jiaozhou Bay, with the main sources being urban domestic, agricultural and livestock breeding. DON seemed to exhibit higher bioavailability than DOC. The temporal evolution of fluorophores and optical indices revealed that bioavailable DOM from livestock breeding and urban domestic sources was high. Spectroscopic properties indicated that the degree of humification of the organic molecules changed significantly for DON from livestock breeding and urban domestic sources, followed by agricultural sources, and forestry sources were the lowest. SUVA₂₅₄ values and HIX were negatively correlated with DON bioavailability, which can be used as a refractory index and for predicting bioavailable DON.
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25908. 题目: Iron cycling in a mesocosm experiment in a north Patagonian fjord: Potential effect of ammonium addition by salmon aquaculture
文章编号: N19022605
期刊: Estuarine, Coastal and Shelf Science
作者: N. Sanchez, M.V. Ardelan, N. Bizsel, J.L. Iriarte, L.M. Olsen
更新时间: 2019-02-26
摘要: Salmon aquaculture in Chile has been a rapidly growing industry, generating increasing inputs of organic matter and inorganic nutrients into the ecosystem. We studied the potential impacts of ammonium input by this industry on the cycling of iron (Fe) in a Chilean fjord. The distribution of different Fe fractions at varying ammonium concentrations was monitored in a twenty-two day mesocosm experiment. The setup involved brackish water and seawater; each had a control and four ammonium concentrations. Measurements were performed for total (TFe_Ch) and dissolved (DFe_Ch) chelex labile Fe fractions, and particulate Fe (PFe). Results for both brackish and seawater showed similar trends but differences in magnitude. Over time, DFe_Ch decreased with increasing ammonium concentration, while TFe_Ch showed up to a three-fold increase positively correlated with ammonium addition, chlorophyll and particulate organic carbon. Overall, PFe values increased over time with 37%–89% of this fraction estimated to be of lithogenic origin. When normalized to particulate organic carbon and chlorophyll, PFe was negatively correlated with ammonium showing an exponential decrease. The PFe measured in the 20–140 μm fraction, showed a hyperbolic relationship with particulate phosphorus, suggesting a change in the ratio for these elements in this size fraction. The increase and dominance of diatoms over time in both water types, together with the observed PFe trend, suggest that large phytoplankton potentially act as the main carrier phase of potential scavenged Fe via the available surfaces of sinking cells. Positive correlations between changes in TFe_Ch and changes in chlorophyll and particulate organic carbon suggest a biological role in controlling the particulate labile Fe fraction, hence resulting in a potential increase of bioavailable Fe. Increasing ammonium addition in the fjords of Chile caused by salmon aquaculture may affect the phytoplankton assemblage composition and therefore the PFe to organic carbon ratio. Possible changes in biogeochemical Fe cycling may result from nutrient enhanced diatom-dominated blooms acting as more efficient vectors for downward export of organic matter.

25909. 题目: Coupling of denitrification and anaerobic ammonium oxidation with nitrification in sediments of the Yangtze Estuary: Importance and controlling factors
文章编号: N19022604
期刊: Estuarine, Coastal and Shelf Science
作者: Cheng Liu, Lijun Hou, Min Liu, Yanling Zheng, Guoyu Yin, Ping Han, Hongpo Dong, Juan Gao, Dengzhou Gao, Yongkai Chang, Zongxiao Zhang
更新时间: 2019-02-26
摘要: Coupling of denitrification and anaerobic ammonium oxidation (anammox) with nitrification is an important mechanism for controlling nitrogen removal from aquatic ecosystems. In this work, we determined ambient rates of denitrification and anammox and their coupling links to nitrification in sediments of the Yangtze Estuary along a salinity gradient, using continuous-flow experiments combined with ¹⁵N isotope pairing technique. The rates of total denitrification and coupled nitrification-denitrification ranged from 0.44 to 7.03 μmol N m⁻² h⁻¹ and from below the detection limit to 4.26 μmol N m⁻² h⁻¹, respectively. The rates of total anammox and coupled nitrification-anammox varied from 0.09 to 1.21 μmol N m⁻² h⁻¹ and from below the detection limit to 0.73 μmol N m⁻² h⁻¹, respectively. It is shown that high availability of NO₃⁻ in bottom water as well as ferrous iron and organic carbon in sediments was beneficial to the uncoupled nitrogen removal processes, while low NO₃⁻ concentration in bottom water promoted the coupled nitrification-nitrogen removal processes. Along the salinity gradient, the coupled nitrification-nitrogen removal processes were the main nitrogen removal pathway in the Yangtze Estuary, and their contribution to total nitrogen removal was affected by NO₃⁻ concentrations, dissolved oxygen and salinity of sampling sites. Overall, this study improves the understanding of nitrate transformation processes in the estuarine and coastal environments.

25910. 题目: Phosphorus cycling in Lake Cadagno, Switzerland: A low sulfate euxinic ocean analogue
文章编号: N19022603
期刊: Geochimica et Cosmochimica Acta
作者: Yijun Xiong, Romain Guilbaud, Caroline L. Peacock, Raymond P. Cox, Donald E. Canfield, Michael D. Krom, Simon W. Poulton
更新时间: 2019-02-26
摘要: Low sulfate, euxinic water-column conditions were a common feature of many Precambrian and Phanerozoic periods of ocean anoxia. The cycling of phosphorus in anoxic marine environments exerts a fundamental control on primary productivity, organic carbon production and burial, and hence ultimately oxygen production, but the dynamics of the phosphorus cycle in low sulfate, euxinic settings are largely unknown. Here, we provide a detailed geochemical investigation of phosphorus cycling in the low sulfate, euxinic Lake Cadagno, Switzerland, which is considered a prime analogue for ancient euxinic oceans. We find evidence for extensive recycling of phosphorus from the sediments back to the water column, stimulated by the microbial release of phosphorus from organic matter and Fe (oxyhydr)oxide minerals. Consistent with previous studies of modern and ancient anoxic settings, this regenerated flux maintains high concentrations of phosphorus in the water column, thus promoting a positive productivity feedback. However, the low-sulfate condition of the overlying water column, combined with the rapid removal of sulfide (as pyrite) from porewaters, promotes formation of Fe(II) phosphate minerals (e.g., vivianite) close to the sediment-water interface. This, in turn, modulates the extent of phosphorus recycling back to the water column, and contrasts with modern fully marine euxinic settings, where the higher concentrations of dissolved sulfate promote sulfide formation to greater depths, thus limiting Fe(II) phosphate formation close to the sediment-water interface. The prevalence of low-sulfate conditions during past euxinic episodes suggests that the operation of this near-surface sedimentary trap for recycled phosphorus would have limited the positive P-driven productivity feedback, promoting only a moderate degree of P recycling. Furthermore, the precise magnitude of this recycled P flux would, on a global scale, have been dependent on changes in the size of Earth’s marine sulfate reservoir through time. Thus our findings have major implications for rates of P-driven productivity and organic carbon burial in ancient euxinic settings, which have not previously been factored into reconstructions of Earth’s oxygenation history.

25911. 题目: Effect of ligands on the production of oxidants from oxygenation of reduced Fe-bearing clay mineral nontronite
文章编号: N19022602
期刊: Geochimica et Cosmochimica Acta
作者: Qiang Zeng, Hailiang Dong, Xi Wang
更新时间: 2019-02-26
摘要: Oxygenation of reduced iron-bearing clay minerals produces highly reactive oxidants that are capable of transforming a range of organic compounds, which is of great environmental importance, but the effect of Fe-chelating ligands on this process has not been studied. In this work, oxidant production from oxygenation of reduced nontronite was investigated in the presence of four common ligands. Addition of phosphate, tripolyphosphate (TPP), nitrilotriacetic acid (NTA) and ethylene diaminetetraacetic acid (EDTA) all significantly increased the oxidant yields, but the specific mechanisms varied, depending on the ligand types. NTA and EDTA addition promoted dissolution of structural Fe, forming aqueous NTA-Fe²⁺ and EDTA-Fe²⁺ complexes. Upon exposure to air, these complexed species rapidly oxidized through homogeneous Fenton reaction, forming chelated soluble Fe³⁺ species, which were rapidly reduced back to Fe²⁺ by electrons transferred from structural Fe(II) in reduced nontronite. With increasing NTA and EDTA loadings, homogeneous Fenton reaction gradually dominated over heterogeneous oxidation of structural Fe(II). Because of rapid air oxidation of NTA-Fe²⁺ and EDTA-Fe²⁺ complexes, these species were maintained at low levels in aqueous solution, thus minimizing the quenching effect of oxidants by excess Fe²⁺and the probability of non-oxidant generation pathway, both of which contributed to the observed increase of the oxidant yields. In contrast, phosphate increased the oxidant yield through sorption to the surface of reduced NAu-2 and a subsequent shift of weak oxidant [possibly Fe(IV)] to strongly reactive hydroxyl radicals (HO). TPP played a dual role by both changing the surface catalytic properties of nontronite through sorption and enhancing homogeneous Fenton reaction by chelating with aqueous Fe²⁺ and Fe³⁺. These results shed lights on how commonly present natural and synthetic ligands affect the oxidation process of reduced iron-bearing clay minerals and oxidant production, hence providing a theoretical basis for understanding oxidant-promoted transformation mechanisms of organic matter in either natural or engineered systems.

25912. 题目: Characteristics and performance of PVDF membrane prepared by using NaCl coagulation bath: Relationship between membrane polymorphous structure and organic fouling
文章编号: N19022601
期刊: Journal of Membrane Science
作者: Yang Zhang, Lin Ye, Bopeng Zhang, Yongsheng Chen, Weigao Zhao, Guang Yang, Jie Wang, Hongwei Zhang
更新时间: 2019-02-26
摘要: In ultrafiltration (UF) applications, the antifouling modification of semi-crystalline poly (vinylidene fluoride) (PVDF) membrane aroused extensive attention. However, efforts have paid less attention to the roles of PVDF polymorphs in fouling alleviation. In this study, we report a new strategy to tailor the polymorphs and pore structure of the PVDF membranes, simultaneously, via incorporating the in-situ blending of Pluronic F127 (F127) with a sodium chloride (NaCl) coagulation bath (CB). The NaCl CBs were utilized to create ion-dipole interactions between Na⁺ and PVDF molecule chains, and to promote the formation of polar β-PVDF phase during phase inversion process. When cooperated with the NaCl CBs, due to the intensified copolymer-polymer interactions, blending amphipathic F127 was demonstrated more effective in manipulating the membrane morphology compared with blending hydrophilic additives. The prepared membrane possessed a highly porous surface with narrowed size distribution, resulting in a great enhancement for both the permeability and selectivity. Furthermore, isopropanol (IPA) post-treatment was purposely performed to wash out the F127 embedded in the membrane matrix. The dominating β-PVDF phase almost doubled the surface energy of the pure PVDF membrane compared with the α-PVDF phase, especially in electron donor functionality, which endowed the membrane enhanced fouling resistance for natural organic matter. As the fouling resistance introduced by polymer itself is more attractive than by exotic additives due to the better stability, we anticipate this new strategy will have numerous potential applications in the future.
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25913. 题目: Adsorption recovery of phosphate from aqueous solution by CaO-biochar composites prepared from eggshell and rice straw
文章编号: N19022506
期刊: Science of The Total Environment
作者: Xiaoning Liu, Feng Shen, Xinhua Qi
更新时间: 2019-02-25
摘要: CaO-biochar composites were prepared by mixed ball milling and pyrolysis of agricultural wastes eggshell and rice straw. The resulting CaO-biochar composites (E-C) showed excellent performance for phosphate adsorption from aqueous solution in a wide range of solution pH (5–11), and a maximum adsorption capacity of 231 mg/g could be obtained by E-C sample that was prepared from the eggshell and rice straw with a mass ratio of 1:1 (E-C 1:1). The adsorption of phosphate onto the E-C samples could be well described by pseudo-second-order (R² > 0.975) and Langmuir models (R² > 0.979). Thermodynamic analysis revealed that the adsorption process was spontaneous (ΔG⁰ < 0) and endothermic (ΔH⁰ > 0). This work provides a promising method to prepare functionalized biochar adsorbents from agricultural wastes for the recovery of phosphate from aqueous solution, and the phosphate adsorbed CaO-biochar composites can be directly applied as a slow-release fertilizer to farmland soil, which have the functions of improving soil physical structure, increasing soil fertility, and regulating soil pH.
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25914. 题目: Using chromatographic and spectroscopic parameters to characterize preference and kinetics in the adsorption of humic and fulvic acid to goethite
文章编号: N19022505
期刊: Science of The Total Environment
作者: Long Wang, Yongtao Li, Liping Weng, Yang Sun, Jie Ma, Yali Chen
更新时间: 2019-02-25
摘要: Humic substances (HS) are very heterogeneous, and preferential adsorption of certain components takes place during their interaction with minerals. Our results indicated that for fulvic acid (FA) the relatively large (3.6–18.2 kDa) particles were preferred in the adsorption to goethite, whereas for humic acid (HA) the intermediate sized (3.6–12.0 kDa) fractions were preferred. Correlations between molar mass (M_w) and specific UV absorption values (SUVA) with ratios of UV light absorbance (E₂/E₃, E₄/E₆) were observed. The adsorption did not change the relation between E₂/E₃ and M_w, E₄/E₆ and SUVA. The E₂/E₃ and E₄/E₆ can probably be used as indicators of molar mass and aromaticity of HS in studying the preferential adsorption. The adsorption of HA and FA to goethite was fast and reached a steady state in about 6 h. The intermediate sized HA particles (3.6–12.0 kDa) were adsorbed quickly, and part of them was subsequently replaced by somewhat larger particles (>50 kDa). For FA, preferential adsorption of relative large particles (3.6–18.2 kDa) took place quickly, and there was a limited substitution by particles with higher aromaticity. Without specifying the property especially the molar mass range of HS under study, confusion can arise from researches using different HS materials.
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25915. 题目: Role of organic carbon, nitrate and ferrous iron on the partitioning between denitrification and DNRA in constructed stormwater urban wetlands
文章编号: N19022504
期刊: Science of The Total Environment
作者: Md. Moklesur Rahman, Keryn L. Roberts, Michael R. Grace, Adam J. Kessler, Perran L.M. Cook
更新时间: 2019-02-25
摘要: Denitrification (DNF) and dissimilatory nitrate reduction to ammonium (DNRA) are two competing nitrate reduction pathways that remove or recycle nitrogen, respectively. However, factors controlling the partitioning between these two pathways are manifold and our understanding of these factors is critical for the management of N loads in constructed wetlands. An important factor that controls DNRA in an aquatic ecosystem is the electron donor, commonly organic carbon (OC) or alternatively ferrous iron and sulfide. In this study, we investigated the role of natural organic carbon (NOC) and acetate at different OC/NO₃⁻ ratios and ferrous iron on the partitioning between DNF and DNRA using the ¹⁵N-tracer method in slurries from four constructed stormwater urban wetlands in Melbourne, Australia. The carbon and nitrate experiments revealed that DNF dominated at all OC/NO₃⁻ ratios. The higher DNF and DNRA rates observed after the addition of NOC indicates that nitrate reduction was enhanced more by NOC than acetate. Moreover, addition of NOC in slurries stimulated DNRA more than DNF. Interestingly, slurries amended with Fe²⁺ showed that Fe²⁺ had significant control on the balance between DNF and DNRA. From two out of four wetlands, a significant increase in DNRA rates (p < .05) at the cost of DNF in the presence of available Fe²⁺ suggests DNRA is coupled to Fe²⁺ oxidation. Rates of DNRA increased 1.5–3.5 times in the Fe²⁺ treatment compared to the control. Overall, our study provides direct evidence that DNRA is linked to Fe²⁺ oxidation in some wetland sediments and highlights the role of Fe²⁺ in controlling the partitioning between removal (DNF) and recycling (DNRA) of bioavailable N in stormwater urban constructed wetlands. In our study we also measured anammox and found that it was always <0.05% of total nitrate reduction in these sediments.
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25916. 题目: Increased risk of phosphorus and metal leaching from paddy soils after excessive manure application: Insights from a mesocosm study
文章编号: N19022503
期刊: Science of The Total Environment
作者: Xi-Peng Liu, Qing-Fang Bi, Lin-Lin Qiu, Ke-Jie Li, Xiao-Ru Yang, Xian-Yong Lin
更新时间: 2019-02-25
摘要: Livestock manure has gradually become an alternative fertilizer for maintaining soil fertility, whereas excessive application of manure leads to the release of phosphorus (P) and toxic metals that may cause complex environmental risks. To investigate the accumulation and migration of P within soil profiles, a mesocosm experiment was conducted to analyze the content and leaching of soil P, metals, and dissolved organic carbon after different fertilization treatments, including control (no fertilizer, CK), chemical fertilizer (CF), chemical fertilizer combined low (CF + LPM) and high (CF + HPM) rate of manure application. Results showed that a high rate of manure application significantly enhanced the accumulation of total soil P (by ~14%) and P availability (easily-available P, by ~24%; Olsen-P, by ~20%) in topsoil, and also increased the content of easily-available organic P (EA-Po) in both topsoil and subsoil compared to the CK treatment. The migration of dissolved inorganic and organic P (DIP and DOP) in leachate within soil profiles was strengthened by manure application. Moreover, significant positive correlations between P, metals, and dissolved organic carbon (DOC) in leachate indicated that downward co-migration occurred within the soil profiles, and also suggested that excessive manure application can intensify the risk of P loss by increasing the migration of manure-derived DOC. Overall, our findings provide insights into P accumulation and migration within soil profiles after excessive manure application, which is useful for predicting the potential risk of P and metal leaching from paddy soils.
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25917. 题目: Effects of fluorescent dissolved organic matters (FDOMs) on perfluoroalkyl acids (PFAAs) in lake and river water
文章编号: N19022502
期刊: Science of The Total Environment
作者: Wen-Xiu Liu, Wei He, Jing-Yi Wu, Wen-Jing Wu, Fu-Liu Xu
更新时间: 2019-02-25
摘要: This study presents the effects of fluorescent dissolved organic matters (FDOM) on perfluoroalkyl acids (PFAAs) in western Lake Chaohu and its inflow rivers. The surface water samples from the 27 sites in western Lake Chaohu and its inflow rivers were collected in March and September 2013. The contents of PFAAs and the FDOM in the water samples were measured by a high-performance liquid chromatograph - mass spectrometer (HPLC-MS) and by a fluorescence spectrophotometer, respectively. The temporal-spatial distributions of PFAAs and FDOM, as well as their interrelationships, were investigated. Eleven PFAA components were detected, and the mean concentration of total PFAAs (TPFAAs) in western Lake Chaohu and its inflow rivers were 12.93 ± 5.19 ng/L and 11.84 ± 9.50 ng/L, respectively. PFOA was the predominant contaminant in two regions (7.13 ± 3.07 ng/L and 4.30 ± 2.14 ng/L) followed by PFHxA (1.72 ± 0.80 ng/L and 1.42 ± 1.41 ng/L) and PFBA (1.44 ± 0.78 ng/L and 1.37 ± 0.78 ng/L). The mean concentration of total FDOM in western Lake Chaohu and its inflow rivers were 220.0 ± 40.30 μg quinine sulfate units (Q.S.)/L and 406.3 ± 213.1 μg Q.S./L, respectively. The significant, positive correlations were observed between the PFAAs and FDOMs in both the lake area and the inflow rivers. However, no significant correlation was observed between PFAAs and the dissolved organic carbon (DOC) in the lake area. This finding indicated that the residues and distributions of PFAAs were significantly dependent on the compositions of dissolved organic matters (DOM) and not on the total content of DOM.
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25918. 题目: Differences in soil organic carbon and soil erosion for native pasture and minimum till agricultural management systems
文章编号: N19022501
期刊: Science of The Total Environment
作者: T. Wells, G.R. Hancock, C. Martinez, C. Dever, V. Kunkel, A. Gibson
更新时间: 2019-02-25
摘要: There is considerable debate over how different agricultural management systems such as minimum tillage and grazing affect soil organic carbon (SOC), soil nitrogen (SN) concentrations and soil erosion over the long-term. In this study SOC, SN and erosion characteristics were compared over a ten year period for two neighbouring sites with longstanding but different land management strategies; one cropped under a minimum tillage (MT) regime and one used for grazing on largely native pasture. Both sites (Hunter Valley, New South Wales, Australia) shared the same soil type (Euchrozem) and climate. SOC and SN were both found to be ~50% higher at the grazing site while erosion was found to be significantly greater (an order of magnitude) at the cropping site despite the application of MT practices. No discernible link between erosion and either SOC, SN or C:N was evident. While both sites have temporally constant SOC, SN and C:N, the MT site offers scope for increased SOC sequestration.
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25919. 题目: Assessing activated sludge morphology and oxygen transfer performance using image analysis
文章编号: N19022415
期刊: Chemosphere
作者: Ken Campbell, Jianmin Wang, Margo Daniels
更新时间: 2019-02-24
摘要: The morphology of the microbial communities can have dramatic impacts on not only the treatment performance, but also the energy use performance of an activated sludge process. In this research, we developed and calibrated an image analysis technique to determine key morphological parameters such as the floc diameter and the specific filament length (SFL) and discovered that the SFL has significant impacts on sludge floc size, the specific extracellular polymeric substances production, the settleability, mixed liquor viscosity, and oxygen transfer efficiency. When the SFL increased from 2.5 × 10⁹ μm g⁻¹ to 6.0 × 10¹⁰ μm g⁻¹, the apparent viscosity normalized by the mixed liquor suspended solids concentration increased by 67%, and the oxygen transfer efficiency decreased by 29%. A long solids retention time (SRT) of 40 day reduced SFL, improved sludge settling performance, and improved oxygen transfer efficiency as compared to shorter SRTs of 10 and 20 day. The findings underscore the need to assess microbial morphology when quantifying the treatment performance and energy performance of activated sludge processes.
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25920. 题目: Arsenite and arsenate binding to ferrihydrite organo-mineral coprecipitate: Implications for arsenic mobility and fate in natural environments
文章编号: N19022414
期刊: Chemosphere
作者: Qin Xue, Ying Ran, Yunzhi Tan, Caroline L. Peacock, Huihui Du
更新时间: 2019-02-24
摘要: Arsenic mobility in soils, sediments and groundwater systems is strongly controlled by adsorption occurring at iron oxide/water interfaces, and the extent of this adsorption may be influenced by the presence of natural organic matter (NOM). This study aims to investigate the adsorption of As(III) and As(V) onto coprecipitates made with ferrihydrite (Fh) and humic acid (HA) with two organic carbon (OC) loadings of 5 and 15 wt% OC. We show that the coprecipitation of HA with Fh can significantly reduce the retention of both As(III) and As(V) over a wide pH range (4–11), and with increased OC loading, there is reduced arsenic adsorption. On pure Fh, As(III) is adsorbed to a greater extent than As(V) at pH > 6.5 (the crossover pH), whereas the crossover pH shifts to more acidic pH in the presence of HA, implying that the binding of As(III) is more favorable than As(V) in the presence of NOM. Both As(III) and As(V) are complexed with the ferric hydroxyl functional groups, and no ternary Fh-HA-As complexes are detected. We observe that ∼40% of the adsorbed As(III) is oxidized to As(V) on pure Fh, compared to only ∼29% of As(III) oxidation on the Fh-HA coprecipitate, indicating that NOM hinders As(III) oxidation on iron (hydr)oxide. The results of this study suggest that NOM interacts with arsenic in ways that promote arsenic mobility and especially promote the mobility of arsenate relative to arsenite, which is of great significance for evaluating the migration and bioavailability of arsenic in both natural and contaminated environments.