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13221. 题目: Enhanced cadmium immobilization in saturated media by gradual stabilization of goethite in the presence of humic acid with increasing pH
文章编号: N18081705
期刊: Science of The Total Environment
作者: Yali Chen, Jie Ma, Yongtao Li, Liping Weng
更新时间: 2018-08-17
摘要: Goethite (Gt) and humic acid (HA) are important components of soil that significantly affect Cd mobility. In this study, the co-transport of Cd2+ and Gt with/without HA in saturated sand columns was investigated by monitoring the breakthrough curves at different pH values. A solute transport model was used to study Cd2+ transport and retention in the saturated sand in the presence of Gt and HA, and a colloid transport model was used to describe the Gt colloid (GtC) transport in the columns. Our results showed that the transport behaviors of Cd2+ and Gt colloids/aggregates were regulated by pH. Cadmium transport was significantly inhibited at high pH due to its adsorption on the sand and Gt. Moreover, Gt retention was gradually stabilized with increasing pH regardless of its forms, i.e., individual colloids (GtC) or larger assemblages of particles due to aggregation (GtA). This retention was obviously enhanced in the presence of HA. Thus, the superposition of increased Cd2+ adsorption on Gt and Gt retention (stabilization) enhanced the immobilization of Cd2+ at high pH. In addition to stabilizing Gt, HA further enhance Cd2+ adsorption on Gt, thus promoting Cd2+ immobilization. However, only a small amount of organic-matter-bound Cd2+ was observed in the columns with injected HA. The major fractions of retained Cd2+ were exchangeable Cd2+ and Fe-oxide-bound Cd2+. Our results provide new insights into the roles of Gt and HA in the transport and mobilization of Cd2+ in soil-groundwater systems.
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13222. 题目: Efficient cephalexin degradation using active chlorine produced on ruthenium and iridium oxide anodes: Role of bath composition, analysis of degradation pathways and degradation extent
文章编号: N18081704
期刊: Science of The Total Environment
作者: Lic A. Perea, Ricardo E. Palma-Goyes, Jorge Vazquez-Arenas, Issis Romero-Ibarra, Carlos Ostos, Ricardo A. Torres-Palma
更新时间: 2018-08-17
摘要: The elimination of cephalexin (CPX) using electro-generated Cl2-active on Ti/RuO2-IrO2 anode was assessed in different effluents: deionized water (DW), municipal wastewater (MWW) and urine. Single Ti/RuO2 and Ti/IrO2 catalysts were prepared to compare their morphologies and electrochemical behavior against the binary DSA. XRD and profile refinement suggest that Ti/RuO2-IrO2 forms a solid solution, where RuO2 and IrO2 growths are oriented by the TiO2 substrate through substitution of Ir by Ru atoms within its rutile-type structure. SEM reveals mud-cracked structures with flat areas for all catalysts, while EDS analysis indicates atomic ratios in the range of the oxide stoichiometries in the nominal concentrations used during synthesis. A considerably higher CPX degradation is achieved in the presence of NaCl than in Na2SO4 or Na3PO4 media due to the active chlorine generation. A faster CPX degradation is reached when the current density is increased or the pH value is lowered. This last behavior may be ascribed to an acid-catalyzed reaction between HClO and CPX. Degradation rates of 22.5, 3.96, and 0.576 μmol L−1 min−1 were observed for DW, MWW and urine, respectively. The lower efficiency measured in these last two effluents was related to the presence of organic matter and urea in the matrix. A degradation pathway is proposed based on HPLC-DAD and HPLC-MS analysis, indicating the fast formation (5 min) of CPX-(S)-sulfoxide and CPX-(R)-sulfoxide, generated due the Cl2-active attack at the CPX thioether. Furthermore, antimicrobial activity elimination of the treated solution is reached once CPX, and the initial by-products are considerably eliminated. Finally, even if only 16% of initial TOC is removed, BOD5 tests prove the ability of electro-generated Cl2-active to transform the antibiotic into biodegradable compounds. A similar strategy can be used for the abatement of other recalcitrant compounds contained in real water matrices such as urine and municipal wastewaters.
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13223. 题目: Comparative study of atmospheric water-soluble organic aerosols composition in contrasting suburban environments in the Iberian Peninsula Coast
文章编号: N18081703
期刊: Science of The Total Environment
作者: Regina M.B.O. Duarte, Maria Piñeiro-Iglesias, Purificación López-Mahía, Soledad Muniategui-Lorenzo, Jorge Moreda-Piñeiro, Artur M.S. Silva, Armando C. Duarte
更新时间: 2018-08-17
摘要: 'This study investigates the structural composition and major sources of water-soluble organic matter (WSOM) from PM2.5 collected, in parallel, during summer and winter, in two contrasting suburban sites at Iberian Peninsula Coast: Aveiro (Portugal) and Coruña (Spain). PM10 samples were also collected at Coruña for comparison. Ambient concentrations of PM2.5, total nitrogen (TN), and WSOM were higher in Aveiro than in Coruña, with the highest levels found in winter at both locations. In Coruña, concentrations of PM10, TN, and WSOM were higher than those from PM2.5. Regardless of the season, stable isotopic δ13C and δ15N in PM2.5 suggested important contributions of anthropogenic fresh organic aerosols (OAs) at Aveiro. In Coruña, δ13C and δ15N of PM2.5 and PM10 suggests decreased anthropogenic input during summer. Although excitation-emission fluorescence profiles were similar for all WSOM samples, multi-dimensional nuclear magnetic resonance (NMR) spectroscopy confirmed differences in their structural composition, reflecting differences in aging processes and/or local sources between the two locations. In PM2.5 WSOM in Aveiro, the relative distribution of non-exchangeable proton functional groups was in the order: HC (40–43%) > HCC (31–39%) > HCO (12–15%) > Ar-H (5.0–13%). However, in PM2.5 and PM10 WSOM in Coruña, the relative contribution of HCO groups (24–30% and 23–29%, respectively) equals and/or surpasses that of HCC(25–26% and 25–29%, respectively), being also higher than those of Aveiro. In both locations, the highest aromatic contents were observed during winter due to biomass burning emissions. The structural composition of PM2.5 and PM10 WSOM in Coruña is dominated by oxygenated aliphatic compounds, reflecting the contribution of secondary OAs from biogenic, soil dust, and minor influence of anthropogenic emissions. In contrast, the composition of PM2.5 WSOM in Aveiro appears to be significantly impacted by fresh and secondary anthropogenic OAs. Marine and biomass burning OAs are important contributors, common to both sites.'
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13224. 题目: Ballast water treatment and bacteria: Analysis of bacterial activity and diversity after treatment of simulated ballast water by electrochlorination and UV exposure
文章编号: N18081702
期刊: Science of The Total Environment
作者: Nanna B. Petersen, Torben Madsen, Mikkel A. Glaring, Fred C. Dobbs, Niels O.G. Jørgensen
更新时间: 2018-08-17
摘要: Effects of ballast water (BW) treatment by ultra-violet (UV) light and electrochlorination (EC) on survival, activity and diversity of marine bacterioplankton and release of organic matter from cell damage were examined at discharge in a large-scale BW test facility (250 m3 tanks) at Hundested harbour, Denmark. The tests were performed in accordance with the requirements for type approval testing by International Maritime Organization (IMO) and US Coast Guard. After treatment, the water was held in the tanks for one day (EC) before discharge, or 6 days (UV, including also a final UV re-treatment) before discharge. In the discharged and treated water, numbers of viable bacteria and bacterial growth rate had decreased significantly relative to the untreated water, but the total number of bacteria only was reduced in the EC-treated water. After additional storage for up to 10 days in small-scale laboratory incubations, significant regrowth of bacteria was observed after either treatment. Sequencing of 16S rRNA gene amplicons demonstrated that α-Proteobacteria initially were dominant, but γ-Proteobacteria dominated after regrowth. Bacteria used to document BW treatment efficiency (E. coli, Vibrio spp., enterococci) survived both treatments; neither treatment reduced the risk of pathogen dispersal. Concentrations of amino acids in the water were used as indicators of treatment-induced cell damage and demonstrated higher concentrations at discharge, but only after the EC treatments. Our results indicate that activity of bacteria, rather than their abundances, should be used when examining effects by ballast water treatment on microorganisms and that none of the examined treatment technologies could eliminate pathogenic bacteria.
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13225. 题目: Organic matter decomposition sustains sedimentary nitrogen loss in the Pearl River Estuary, China
文章编号: N18081701
期刊: Science of The Total Environment
作者: Ehui Tan, Wenbin Zou, Xinlei Jiang, Xianhui Wan, Ting-Chang Hsu, Zhenzhen Zheng, Ling Chen, Min Xu, Minhan Dai, Shuh-ji Kao
更新时间: 2018-08-17
摘要: The Pearl River Estuary (PRE) has long received tremendous amounts of anthropogenic nitrogen, and is facing severe environmental problems. Denitrification and anaerobic ammonium oxidation (anammox) are known to be two major nitrogen removal pathways in estuarine sediments. Through the use of slurry and intact sediment core incubations, we examined the nitrogen removal pathways and quantified the in situ denitrification and anammox with associated gaseous nitrogen production rates. Sedimentary nitrogen removal was predominated by denitrification (93–100%) relative to a minimal contribution (<7%) from anammox. Among the detected environmental factors, salinity, bottom water NOx (nitrate and nitrite) concentration, sedimentary organic matter and dissolved oxygen consumption rates showed good correlations with denitrification and anammox rates. Sedimentary nitrogen loss was mainly supported by endogenic coupled nitrification-denitrification (6.0 ± 1.5 × 106 mol N d−1), with water-column-delivered NOx (2.1 ± 0.6 × 106 mol N d−1) as the secondary source. Such results suggested that sedimentary nitrogen removal involved mainly particulate organic form (allochthonous or autochthonous) deposited onto sediments, rather than inorganic forms in overlying water. Meanwhile, total N2O production from sediments was estimated to be 7.3 ± 2.1 × 104 mol N d−1, equivalent to ~35% of the daily N2O emissions in the PRE.
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13226. 题目: Responses of soil bacterial communities, enzyme activities, and nutrients to agricultural-to-natural ecosystem conversion in the Loess Plateau, China
文章编号: N18081609
期刊: Journal of Soils and Sediments
作者: Yongxing Cui, Linchuan Fang, Xiaobin Guo, Xia Wang, Yunqiang Wang, Yanjiang Zhang, Xingchang Zhang
更新时间: 2018-08-16
摘要: Purpose: Soil microbial communities play critical function during nutrient cycling. However, with the increasing nutrient input into terrestrial ecosystems from human activities, the responses of soil microorganisms to the aboveground vegetation across agricultural-to-natural succession stages are still poorly understand. The aim of this study was to evaluate the changes of soil microbial communities in three typical succession stages (the cropland, the grassland, and the brushland, respectively). Materials and methods: A field experiment was carried out in an ecological restoration region. Soil samples were collected from three succession stages (the cropland, the grassland, and the brushland) based on their well-dated successional chronosequence in July 2016. Illumina MiSeq sequencing was used to identify the bacterial community structures. The responses of soil bacterial communities and its relationships with soil physicochemical properties and enzyme activities were assessed. Results and discussion: The results showed that soil nutrients (soil organic carbon (SOC), total N, and NH4+) and enzyme activities (β-1,4-glucosidase and phosphatase) were significantly increased across the conversion from agricultural to natural ecosystem, and the enzyme activities were significantly affected by SOC and total N. It indicated that vegetation restoration greatly improved soil quality and nutrient cycling rates mediated by microbial metabolisms. Furthermore, there were no changes in soil bacterial community structures during the three vegetation succession stages, which implied the stability and adaption of microbial communities under the vegetation succession in semiarid climate. It should be noted that Firmicutes taxa were more sensitive than other taxa during natural vegetation recovery. Structural equation model (SEM) revealed that soil nutrients (soil organic matter (SOM) and total P), element stoichiometry (SOC:total P), and extracellular enzyme activities (urease and alkaline phosphatase) were dominant factors to shape the relative abundance of Firmicutes. Conclusions: Firmicutes can be considered as bio-indicators to monitor soil quality and nutrient turnover during natural vegetation recovery. This study presents better understanding about the connections among soil nutrient cycling, enzyme activities, and soil bacterial communities during vegetation natural restoration, especially in typical ecological critical zone.

13227. 题目: Optimization process of organic matter removal from wastewater by using Eichhornia crassipes
文章编号: N18081608
期刊: Environmental Science and Pollution Research
作者: Sènandémi Edwige Reine Mahunon, Martin Pépin Aina, Akuemaho Virgile Onésime Akowanou, Edmond Konan Kouassi, Benjamin Kouassi Yao, Kopoin Adouby, Patrick Drogui
更新时间: 2018-08-16
摘要: This study aimed to determine the optimal conditions for organic matter removal from wastewater by Eichhornia crassipes (E.C). As a matter of fact, a complete factorial design was used to determine the effect of residence time (X1), plant density (X2) and initial chemical oxygen demand (COD) concentration (X3) on the phytoremediation process. The process’s performance was measured on COD (Y1), NH4+ (Y2) and PO43− (Y3), with the results indicating a reduction of 8.59–81.71% of COD (Y1); 22.53–95.81% of NH4+ (Y2) and 0.54–99.35% of PO43− (Y3). Then, the first-order models obtained for COD, NH4+ and PO43− removal were validated using different statistical approaches such as statistical and experimental validation. Moreover, multi-response optimization was carried out through different scenarios. On the whole, the results obtained indicated that two serial ponds are required for an optimum organic matter removal by Eichhornia crassipes. Indeed, for the first pond, a residence time of 15 days is needed with a plant density of 60 ft/m2 and an initial concentration of about 944 mg/L. The second was the same residence time as the first with similar plant density of 60 ft/m2 and an initial load 192 mg/L (> 200 mg/L). Optimal organic matter removal from wastewater using Eichhornia crassipes requires two ponds arranged in chain.

13228. 题目: Impact of land cover types on soil aggregate stability and erodibility
文章编号: N18081607
期刊: Environmental Monitoring and Assessment
作者: Remzi İlay, Yasemin Kavdir
更新时间: 2018-08-16
摘要: Gökçeada is the biggest island, and it is also known as the organic island of Turkey. Approximately 65% of the Gökçeada lands have slope > 12%. Climate, topography, land cover, and soil characteristics are considered to be the main natural factors affecting soil erosion severity in the Gökçeada. Prevention of soil degradation, hence the preservation or improvement of the overall quality of the soil, is directly related to the presence of stable soil aggregates. In addition, the resistance to weathering and replacement of soil particles are also relevant aspects in terms of sustainability. Aggregate stability (AS) and erodibility of land (Kfac) are related to soil properties. However, this relationship can vary under different circumstances. In this study, 248 surface soil samples have been taken from forest and semi-natural areas (FSNA) and agricultural areas (AGRA) according to CORINE 2006. Eleven selected soil properties were measured, and their impacts on AS and Kfac (RUSLE-K) were determined by using the CRT (classification and regression tree) in Gökçeada. Results showed that the relations among soil characteristics changed according to the land cover classes. Total organic carbon is much more associated with AS in AGRA, while total carbon is associated with AS in FSNA. The effect of calcium carbonate on Kfac was higher than other soil properties when the land cover type was ignored. On the other hand, in AGRA, the effect of between clay content on Kfac was greater than those of FSNA.

13229. 题目: Non-Singlet Oxygen Kinetic Solvent Isotope Effects in Aquatic Photochemistry
文章编号: N18081606
期刊: Environmental Science & Technology
作者: Caroline A. Davis, Kristopher McNeill, Elisabeth M.-L. Janssen
更新时间: 2018-08-16
摘要: The kinetic solvent isotope effect (KSIE) is typically utilized in environmental photochemistry to elucidate whether a compound is susceptible to photooxidation by singlet oxygen (1O2), due to its known difference in lifetime in water (H2O) versus heavy water (D2O). Here, the overall indirect photodegradation rates of diarylamines in the presence of dissolved organic matter (DOM) were enhanced in D2O to a greater extent than expected based on their reactivity with 1O2. For each diarylamine, the relative contribution of reaction with 1O2 to the observed KSIE was determined from high resolution data of 1O2 lifetimes by time-resolved infrared luminescence spectroscopy. The additional enhancement in D2O beyond reaction with 1O2 contributed significantly to the observed KSIE for diarylamines (8–65%) and diclofenac (100%). The enhancement was ascribed to slower reduction of transient radical species of the diarylamines due to H/D exchange at DOM’s phenolic antioxidant moieties. A slower second-order reaction rate constant with a model antioxidant was verified for mefenamic acid radicals using transient absorption spectroscopy. Changes in lifetime and reactivity with triplet sensitizers were not responsible for the additional KSIE. Other pollutants with quenchable radical intermediates may also be susceptible to such an additional KSIE, which has to be considered when using the KSIE as a diagnostic tool.
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13230. 题目: Graphene Modified Electro-Fenton Catalytic Membrane for in Situ Degradation of Antibiotic Florfenicol
文章编号: N18081605
期刊: Environmental Science & Technology
作者: Wen-Li Jiang, Xue Xia, Jing-Long Han, Yang-Cheng Ding, Muhammad Rizwan Haider, Ai-Jie Wang
更新时间: 2018-08-16
摘要: The removal of low-concentration antibiotics from water to alleviate the potential threat of antibiotic-resistant bacteria and genes calls for the development of advanced treatment technologies with high efficiency. In this study, a novel graphene modified electro-Fenton (e-Fenton) catalytic membrane (EFCM) was fabricated for in situ degradation of low-concentration antibiotic florfenicol. The removal efficiency was 90%, much higher than that of electrochemical filtration (50%) and single filtration process (27%). This demonstrated that EFCM acted not only as a cathode for e-Fenton oxidation process in a continuous mode but also as a membrane barrier to concentrate and enhance the mass transfer of florfenicol, which increased its oxidation chances. The removal rate of florfenicol by EFCM was much higher (10.2 ± 0.1 mg m–2 h–1) than single filtration (2.5 ± 0.1 mg m–2 h–1) or batch e-Fenton processes (4.3 ± 0.05 mg m–2 h–1). Long-term operation and fouling experiment further demonstrated the durability and antifouling property of EFCM. Four main degradation pathways of florfenicol were proposed by tracking the degradation byproducts. The above results highlighted the feasibility of this integrated membrane catalysis process for advanced water purification.
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13231. 题目: The remineralization of sedimentary organic carbon in different sedimentary regimes of the Yellow and East China Seas
文章编号: N18081604
期刊: Chemical Geology
作者: Bin Zhao, Peng Yao, Thomas S. Bianchi, Ana R. Arellano, Xuchen Wang, Jianbin Yang, Rongguo Su, Jinpeng Wang, Yahong Xu, Xinying Huang, Lin Chen, Jun Ye, Zhigang Yu
更新时间: 2018-08-16
摘要: We investigated the remineralization of sedimentary organic carbon (SOC) at 12 sites in East China Sea mobile-muds (ECSMMs) and South Yellow Sea central mud deposits (SYSMDs) - using a time-sequence sediment incubation experiment. We examined pore-water dissolved inorganic carbon (DIC), dissolved organic carbon (DOC), fluorescent dissolved organic matter (FDOM), dissolved inorganic nitrogen (DIN) nutrients (NH4+, NO3, and NO2), redox sensitive elements (Fe2+ and Mn2+), and major anions (SO42− and Cl) in incubated sediments, to better constrain controlling mechanisms of SOC remineralization under different sedimentary regimes. Lower DIC production rates in SYSMDs (2.36–3.13 mmol m−2 d−1) than those in ECSMMs (2.94–13.5 mmol m−2 d−1), were mainly attributed to cold bottom water masses and a relatively stable sedimentary environment in SYS. Higher DIC production rates were observed mostly at offshore sites of ECSMMs that had relatively enriched 13C of SOC - which indicated preferential degradation of labile SOC of marine origin. When compared with tropical mobile-muds, higher bottom-water temperatures, thicker mobile-muds, and large inputs of reactive terrestrial OC resulted in more intense remineralization of SOC in Amazon mobile-muds than in ECSMMs. Lower ratios of DOC/DIC production rates in ECSMMs (0.11–0.72) were likely indicative of efficient transformation of OC, and largely due to sulfate reduction. A rapid increase in marine protein-like FDOM components during the incubation indicated that less stable marine SOC was preferentially converted to DOC - and then to DIC. Our SOC budget indicates that 16.8% of SOC was decomposed in sediments of ECSMMs, but only about 5.4% of SOC was decomposed in SYSMDs, suggesting lower SOC preservation efficiency in mobile-muds than distal muds.

13232. 题目: Cork wastewater purification in a cooperative flocculation/adsorption process with microwave-regenerated activated carbon
文章编号: N18081603
期刊: Journal of Hazardous Materials
作者: Xinyu Ge, Zhilin Wu, Giancarlo Cravotto, Maela Manzoli, Pedro Cintas, Zhansheng Wu
更新时间: 2018-08-16
摘要: The aim of this work is to investigate a novel cork wastewater (CW) purification method that combines flocculation/adsorption with the microwave assisted regeneration of coconut powder activated carbon (CPAC). The flocculation treatment made use of FeSO4·7H2O/NaOH and provided high removal efficiency, as shown by the observed values of UV254 (90%), chemical oxygen demand (COD, 86%), polyphenols (PP, 81%),total solid (TS, 40%), total suspended solid (TSS, 62%), and total dissolved solid (TDS, 18%). After the flocculation and filtration, CPAC was used to further remove left TSS, TDS and dissolved organics. The effects of CPAC amount, pH value and adsorption time have been studied. It was found that 250 mg is the optimum CPAC amount for the treatment of 50 mL CW at pH 3.5 for 10 min. Overall process effectiveness can be summarised as follows: UV254 (100%), COD (98%), PP (100%), TS (58%), TSS (93%), and TDS (24%), while the characteristic colour of the CW completely disappeared. The microwave regenerated CPAC can undergo five runs without appreciable losses in removal efficiency. Predictably, this simple and scalable process could afford a promising treatment method for other industrial wastewaters with high content of organic matters such as PP, phenolic acids and tannins.
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13233. 题目: The treatment of flowback water in a sequencing batch reactor with aerobic granular sludge: Performance and microbial community structure
文章编号: N18081602
期刊: Chemosphere
作者: Xiaoting Zhang, Aoxiang Chen, Daijun Zhang, Shuangwu Kou, Peili Lu
更新时间: 2018-08-16
摘要: The extensive application of hydraulic fracturing technology has significantly promoted the large-scale development of shale gas. However, it is a great challenge for shale gas extraction to effectively manage large-volume flowback water (FW) with high salinity and complex organic substances. Here, we report an aerobic granular sludge (AGS) tolerable to high salinity, and suited to the treatment of FW. The performance of a sequencing batch reactor (SBR) with the AGS for the treatment of the synthetic FW and the microbial community structure at different salinity levels were investigated. The AGS fed with synthetic FW possessed a larger average particle size and a higher settling rate (50 m h−1). When NaCl concentration increased to 50.0 g L−1, the removal efficiency of total organic carbon (TOC) increased to 79 ± 1%, and the removal rate of polyacrylamide (PAM) raised up to 42.7 ± 0.7 g m−3 d−1. Alphaproteobacteria, Betaproteobacteria, Gammaproteobacteria, and Sphingobacteriia dominated in the microbial community of AGS. Cellvibrionaceae, Rhodocyclaceae, Enterobacteriaceae, Moraxellaceae, Pseudomonadaceae, and Halomonadaceae belonging to Betaproteobacteria and Gammaproteobacteria played important role in degrading PAM, polycyclic aromatic hydrocarbons (PAH), and some other organics in FW at high salinity. These results suggest that an AGS-based SBR is a promising technology for the treatment of FW.
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13234. 题目: Enhanced removal of bio-refractory dissolved organic matter from cassava distillery wastewater by powdered activated carbon-ballasted coagulation: Detailed study of separation characteristics and mechanisms
文章编号: N18081601
期刊: Chemosphere
作者: Ming Zhang, Yu Chen, Li Xie, Qi Zhou
更新时间: 2018-08-16
摘要: Efficient removal of bio-refractory dissolved organic matter (DOM) and colorants is essential for discharging or reusing the distillery wastewater. An important part of recalcitrant DOM still exists in the effluent of regular coagulation though the ferric coagulant has been found to be effective in decoloration. The present work adopted powdered activated carbon (PAC) as ballasting agent to achieve robust separation effect and efficiency of bio-refractory DOM from the bio-chemically treated cassava distillery wastewater (BTDWW). More than 90% of DOC could be removed at the PAC and Fe(III)-coagulant dosage of 1.40 g/L and 0.84 g/L as Fe when the BTDWW was neutral. PAC should be dosed before coagulant in order to mix well with the DOM in the BTDWW. The analyses of DOM in effluent reveal that PAC facilitated the removal of lignin breakdown products which could not be well eliminated by regular coagulation; the removal of DOM with MW < 5 kDa was mostly enhanced. The characteristics of flocs demonstrate that PAC reinforced the interaction between Fe(III) species and DOM by providing more reaction sites. The sedimentation could be completed within the initial 5 min, and the highest settling velocity was almost 8 times higher than that of the only Fe(III)-involved flocs. The large size and favorable robustness of PAC-involved flocs enabled decent sedimentation even though their stretched structure might not be desirable in regular coagulation. The PAC-ballasted coagulation is recommended as tertiary treatment of BTDWW considering its high efficiency and sound economic feasibility.
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13235. 题目: Long-term afforestation significantly improves the fertility of abandoned farmland along soil clay gradient on the Chinese Loess Plateau
文章编号: N18081516
期刊: Land Degradation & Development
作者: Yan Zhang, Liyun Wei, Xiaorong Wei, Xuetong Liu, Mingan Shao
更新时间: 2018-08-15
摘要: In China, almost half of the total land area is degraded, mainly due to the unreasonable use of land for agricultural production. During the past half‐century, afforestation has become a popular management option to remedy degraded soils. In this paper, we studied the long‐term effects of afforestation on the major properties of soils with different textures. We measured the changes in soil physical, chemical and fertility properties after 10, 20 and 30 years of afforestation with black locust (Robinia pseudoacacia) on abandoned farmland at 5 sites on the Loess Plateau, China, which is characterized by a temperate monsoon climate. The soil clay contents varied significantly among sites. The objectives were to understand how long‐term afforestation affects soil properties and whether such effects depend on the soil texture. Averaged across the 5 sites and the depths of 0‐10 and 10‐20 cm, afforestation resulted in significant increases in the proportion of macroaggregates (+22.5%), saturated hydraulic conductivity (+185.4%), organic matter content (+110.5%) and total nitrogen content (+110.5%) but significant decreases in the proportion of microaggregates (‐21.9%) and bulk density (‐10.8%). The silt+clay fraction, soil pH and nitrate content were minimally affected by afforestation. The effects of afforestation were greater at 0‐10 cm than at 10‐20 cm, but they varied between sites. Furthermore, most soil metrics linearly responded to the time of afforestation, and such responses were dependent on the soil clay content. Our results suggest that long‐term afforestation improves soil fertility better in soils with a clay content of approximately 20%.

13236. 题目: Organic carbon aging during across-shelf transport
文章编号: N18081515
期刊: Geophysical Research Letters
作者: Rui Bao, Masao Uchida, Meixun Zhao, Negar Haghipour, Daniel Montlucon, Ann McNichol, Lukas Wacker, John M. Hayes, Timothy I. Eglinton
更新时间: 2018-08-15
摘要: Compound‐specific radiocarbon analysis (CSRA) was performed on different grain‐size fractions of surficial sediments to examine and compare lateral transport times (LTTs) of organic carbon. 14C aging of long‐chain leaf wax fatty acids along two dispersal pathways of fluvially‐derived material on adjacent continental margins implies LTTs over distances of ~30 to 500 km that range from hundreds to thousands of years. The magnitude of aging differs among grain size fractions. Our finding suggests that LTTs vary both temporally and spatially as a function of the specific properties of different continental shelf settings. Observations suggest that 14C aging is widespread during lateral transport over continental shelves, with hydrodynamic particle sorting inducing age variations among organic components residing in different grain sizes. Consideration of these phenomena is of importance for understanding carbon cycle processes and interpretation on sedimentary records on continental margins.

13237. 题目: Drivers of Dissolved Organic Matter in the Vent and Major Conduits of the World's Largest Freshwater Spring
文章编号: N18081514
期刊: Journal of Geophysical Research: Biogeosciences
作者: Casey Luzius, Francois Guillemette, David C. Podgorski, Anne M. Kellerman, Robert G. M. Spencer
更新时间: 2018-08-15
摘要: Wakulla Springs is the largest and deepest freshwater spring on Earth and has exhibited increased chromophoric dissolved organic matter (CDOM) inputs (i.e. browning) in recent decades. To examine the drivers of changing dissolved organic matter (DOM) at the spring vent we examined dissolved organic carbon (DOC) concentrations and DOM composition via optical parameters (i.e. absorbance and fluorescence) in the major conduits and a connecting spring over the course of one year. Sample sites separated clearly based on DOC concentration, CDOM absorbance, and optical parameters indicative of autochthonous (clear groundwater) versus allochthonous (terrestrial) DOM. Seasonality was apparent in the allochthonous dominated sites with increasing terrestrial contribution particularly with large precipitation events post dry periods. Principle component analysis highlights the ability of optical parameters to show the dominance of sample sites draining from the southwest (i.e. Apalachicola National Forest) as responsible for the CDOM rich water at the vent, whereas water draining from the north was comparatively clear. Increasing CDOM rich waters at the vent suggests that either input from conduits draining from the southwest have increased, or the relative dilution with clear groundwater has decreased in the conduit system prior to discharge from the vent. Sea‐level rise impacts in the region have been suggested to result in more blackwaters delivered to the vent, and ongoing extraction of clear groundwater reduces the dilution capacity on CDOM rich waters. Thus, anthropogenic impacts in the region need to be addressed if the trend of increased CDOM inputs at Wakulla Springs is to be reversed.

13238. 题目: Mixing State of Carbonaceous Aerosols of Primary Emissions from “Improved” African Cookstoves
文章编号: N18081513
期刊: Environmental Science & Technology
作者: Yuchieh Ting, Edward J. S. Mitchell, James D. Allan, Dantong Liu, Dominick V. Spracklen, Alan Williams, Jenny M. Jones, Amanda R. Lea-Langton, Gordon McFiggans, Hugh Coe
更新时间: 2018-08-15
摘要: Designs of “improved” stoves are introduced recently to benefit the solid fuel consumption of cooking activities in developing countries, but the uncertainties concerning the combustion processes and particulate emissions remain poorly characterized. To help understand this, combustion in three examples of “improved” African cookstoves was investigated in the laboratory. A typical European heating stove was included for comparison purpose. Detailed aerosol emissions were studied in real-time with an Aerosol Mass Spectrometer and Single Particle Soot Photometer, to explore interactions between black carbon (BC) and organic carbon aerosols, which were parametrized according to modified combustion efficiency (MCE), a common metric used within the atmospheric emission community. Greater than 50% of the total organic matter (OM) was found in BC-containing particles when MCE was >0.95 for dry oak and coal fuels, whereas at lower MCE, over 80% of the total OM for most of the fuels existed in particles without detectable BC. When the OM mass fraction of total particulate matter (PM1) > 0.9, the mass ratio of OM to refractory BC in BC-containing particles was about 2–3, but only ∼0.8 when OM mass fraction

13239. 题目: Estimating CDOM concentration in highly turbid estuarine coastal waters
文章编号: N18081512
期刊: Journal of Geophysical Research: Oceans
作者: Jun Zhao, Wenxi Cao, Zhantang Xu, Bin Ai, Yuezhong Yang, Guangzhen Jin, Guifen Wang, Wen Zhou, Yong Chen, Haiyun Chen, Zhaohua Sun
更新时间: 2018-08-15
摘要: We proposed a support vector machine (SVM) algorithm to retrieve colored dissolved organic matter (CDOM) concentration (using ag(443) as a proxy) in the highly turbid Pearl River estuary (PRE). Two band ratios, namely Rrs(443)/Rrs(547) and Rrs(488)/Rrs(547), were used as inputs. Comparisons between the estimated and measured ag(443) illustrated high accuracy of the SVM algorithm, yielding R2s of 0.98 and 0.89, mean absolute percentage errors (MAPEs) of 5.18% and 13.1%, and root mean square deviations (RMSDs) of 0.012 and 0.034 m‐1 for the training and validation datasets, respectively. The SVM algorithm was also evaluated against existing ones for the study area and gave the best accuracy with a R2 of 0.9, a MAPE of 10.23%, and a RMSD of 0.025 m‐1. The diurnal dynamics of CDOM in the PRE was revealed showing complicated variations and influenced by the combined effects of wind, tide, circulation, and river discharge. As for remote sensing applications, the SVM‐based CDOM product exhibited great potential to trace the Pearl River plume and the satellite‐derived plume area agreed well with the FVCOM model simulation result. SVM is an accurate and fast tool for retrieving CDOM concentration, especially in highly turbid estuarine coastal waters, and thus, river plume dynamics can be traced.

13240. 题目: Joint effects of extrinsic biophysical fluxes and intrinsic hydrodynamics on the formation of hypoxia west off the Pearl River Estuary
文章编号: N18081511
期刊: Journal of Geophysical Research: Oceans
作者: Zhongming Lu, Jianping Gan, Minhan Dai, Hongbin Liu, Xiaozheng Zhao
更新时间: 2018-08-15
摘要: Using field measurements and a process‐oriented three‐dimensional coupled physical‐biogeochemical numerical model, we investigated the physical and biogeochemical processes governing the bottom hypoxic zone on the western shelf off the Pearl River Estuary. The intensity and area of the hypoxia grew with increasing total nutrient input from the Pearl River that has increased continuously in recent decades. The hypoxic zone was formed and maintained largely associated with the stable water column where the stability was provided simultaneously by wind stress and freshwater discharge, favourable local hydrodynamics for flow convergence, and westward organic matter transport. Wind stress altered the stratification, while freshwater discharge changed the stratification and baroclinic velocity shear simultaneously. Two‐layered flow with a cyclonically‐rotating current around a salient edge of the western shelf off the estuary hydrodynamically enhanced the local convergence, allowing sufficient residence time for the remineralization of organic matter produced in the hypoxic zone and organic matter transported into the region. Our results suggest that a combination of unique local hydrodynamic feature and decomposition of organic matter in water column and sediment are the cause of the formation and maintenance of the bottom hypoxia on the western shelf of the estuary during summer.

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