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31641. 题目: Sorption of perfluoroalkyl substances (PFASs) to an organic soil horizon – Effect of cation composition and pH
文章编号: N18052912
期刊: Chemosphere
作者: Hugo Campos Pereira, Malin Ullberg, Dan Berggren Kleja, Jon Petter Gustafsson, Lutz Ahrens
更新时间: 2018-05-29
摘要: Accurate prediction of the sorption of perfluoroalkyl substances (PFASs) in soils is essential for environmental risk assessment. We investigated the effect of solution pH and calculated soil organic matter (SOM) net charge on the sorption of 14 PFASs onto an organic soil as a function of pH and added concentrations of Al3+, Ca2+ and Na+. Often, the organic C-normalized partitioning coefficients (K OC ) showed a negative relationship to both pH (Δlog K OC /ΔpH = -0.32 ± 0.11 log units) and the SOM bulk net negative charge (Δlog K OC = -1.41 ± 0.40 per log unit molc g-1). Moreover, perfluorosulfonic acids (PFSAs) sorbed more strongly than perfluorocarboxylic acids (PFCAs) and the PFAS sorption increased with increasing perfluorocarbon chain length with 0.60 and 0.83 log K OC units per CF2 moiety for C3–C10 PFCAs and C4, C6, and C8 PFSAs, respectively. The effects of cation treatment and SOM bulk net charge were evident for many PFASs with low to moderate sorption (C5–C8 PFCAs and C6 PFSA). However for the most strongly sorbing and most long-chained PFASs (C9–C11 and C13 PFCAs, C8 PFSA and perfluorooctane sulfonamide (FOSA)), smaller effects of cations were seen, and instead sorption was more strongly related to the pH value. This suggests that the most long-chained PFASs, similar to other hydrophobic organic compounds, are preferentially sorbed to the highly condensed domains of the humin fraction, while shorter-chained PFASs are bound to a larger extent to humic and fulvic acid, where cation effects are significant.
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31642. 题目: Toxicity screening of biochar-mineral composites using germination tests
文章编号: N18052911
期刊: Chemosphere
作者: Jan Mumme, Josephine Getz, Munoo Prasad, Ulf Lüder, Jürgen Kern, Ond?ej Ma?ek, Wolfram Buss
更新时间: 2018-05-29
摘要: This study assessed the properties and toxicity (water cress germination trials) of 38 waste-derived, novel biochar-mineral composites (BMCs) produced via slow pyrolysis and hydrothermal carbonization (hydrochars). The biochars were produced from sewage sludge and compost-like output (CLO) by varying the type of mineral additive (zeolite, wood ash and lignite fly ash), the mineral-to-feedstock ratio and the carbonization process. While pure hydrochars completely inhibited germination of water cress, this effect was ameliorated by mineral additives. Seedlings grew best in pyrolysis chars and while wood ash addition decreased plant growth in many cases, 1:10 addition to CLO doubled germination rate. The factors responsible for the phytotoxicity can be attributed to pH, salinity and organic contaminants. Importantly, while pure minerals inhibited germination, conversion of minerals into BMCs reduced their inhibitory effects due to buffered release of minerals. Overall, mineral wastes (e.g., combustion ashes) and waste biomass can be used safely as sources of nutrients and stable organic carbon (for soil carbon sequestration) when converted into specific biochar-mineral composites, exploiting synergies between the constituents to deliver superior performance.

31643. 题目: Enhanced hexavalent chromium removal performance and stabilization by magnetic iron nanoparticles assisted biochar in aqueous solution: Mechanisms and application potential
文章编号: N18052910
期刊: Chemosphere
作者: Shishu Zhu, Xiaochen Huang, Dawei Wang, Li Wang, Fang Ma
更新时间: 2018-05-29
摘要: The superiority of the nanoscale zero valent iron (nZVI) assisted biochar (BC) composites compared to traditional nZVI and its application feasibility are still unclear. This study aimed to provide valuable information for practical application. Firstly, the Fe/BC mass ratio of 2:1 during the preparation of nZVI-BC was proved obtaining the complete Cr6+ removal. Then, results revealed that the initial pH value tuned Cr6+ removal performance via varying existing Cr6+ species, surface charge, and chemical states of iron nanoparticles (NPs). Improvement of colloidal stabilization and positive surface charge attributed to enhancement of Cr6+ removal of nZVI-BC. The Cr6+ removal process was well described using pseudo-second-order kinetic. By Langmuir isotherm model, the maximum removal capacity (58.82 mg g-1) was determined. Moreover, the multiple evidences (XRD, XPS, FTIR, and TEM results) explained the mechanisms of Cr6+ removal (i.e. electrostatic force, complexes, metal reduction, and precipitates on the edges). Little inhibitory effect of coexisting anions (SO4 2-, PO4 3-, and NO3 -) and well regeneration ability (82.2% removal efficiency after five cycles using acid washing), along with well Cr6+ removal efficiencies of real contaminated water (electroplating wastewater, tannery wastewater and groundwater) treatment, suggested nZVI-BC was considered as a superior and cost-effective choice for Cr6+ included polluted water treatment.
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31644. 题目: Groundwater contamination and land drainage induce divergent responses in boreal spring ecosystems
文章编号: N18052909
期刊: Science of The Total Environment
作者: Kaisa Lehosmaa, Jussi Jyv?sj?rvi, Jari Ilmonen, Pekka M. Rossi, Lauri Paasivirta, Timo Muotka
更新时间: 2018-05-29
摘要: Degradation of freshwater ecosystems has engendered legislative mandates for the protection and management of surface waters while groundwater-dependent ecosystems (GDEs) have received much less attention. This is so despite biodiversity and functioning of GDEs are currently threatened by several anthropogenic stressors, particularly intensified land use and groundwater contamination. We assessed the impacts of land drainage (increased input of dissolved organic carbon, DOC, from peatland drainage) and impaired groundwater chemical quality (NO3 --N enrichment from agricultural or urban land use) on biodiversity and ecosystem functioning in 20 southern Finnish cold-water springs using several taxonomic and functional measures. Groundwater contamination decreased macroinvertebrate and bacterial diversity and altered their community composition. Changes in macroinvertebrate and bacterial communities along the gradient of water-quality impairment were caused by the replacement of native with new taxa rather than by mere disappearance of some of the original taxa. Also species richness of habitat specialist (but not headwater generalist) bryophytes decreased due to impaired groundwater quality. Periphyton accrual rate showed a subsidy-stress response to elevated nitrate concentrations, with peak values at around 2500 μg L-1, while drainage-induced spring water brownification (increased DOC) reduced both periphyton accrual and leaf decomposition rates already at very low concentrations. Our results highlight the underutilized potential of ecosystem-level functional measures in GDE bioassessment as they seem to respond to the first signs of spring ecosystem impairment, at least for the anthropogenic stressors studied by us.
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31645. 题目: Manure digestate storage under different conditions: Chemical characteristics and contaminant residuals
文章编号: N18052908
期刊: Science of The Total Environment
作者: Yun Li, Hang Liu, Guoxue Li, Wenhai Luo, Ying Sun
更新时间: 2018-05-29
摘要: In this study, chemical characteristics and contaminant residuals in livestock manure digestate were investigated during storage under different conditions. Results show that storing digestate openly under the mesophilic condition (30 ± 1 °C) led to water evaporation and thus considerable mass reduction. As a result, concentrative effect occurred to increase the contents of organic matter, nutrients, and heavy metals during digestate storage. By contrast, ammonium (NH4 +) concentration in digestate decreased over storage period. The concentrative effect and NH4 + reduction could be mitigated by storing digestate with coverage and/or under psychrophilic conditions (e.g. 15 ± 1 °C). Regardless of storage conditions, organic matter was further biodegraded, thereby reducing the residuals of antibiotics in digestate. Antibiotic removal was more notable when digestate was stored under mesophilic conditions. Nevertheless, additional processes to control heavy metals and antibiotics in digestate are still necessary before agricultural applications.
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31646. 题目: Biochar enhances plant growth and nutrient removal in horizontal subsurface flow constructed wetlands
文章编号: N18052907
期刊: Science of The Total Environment
作者: Kuno Kasak, Jaak Truu, Ivika Ostonen, Jürgen Sarjas, Kristjan Oopkaup, P??rn Paiste, Margit K?iv-Vainik, ?lo Mander, Marika Truu
更新时间: 2018-05-29
摘要: Biochar has shown great potential as an amendment to improve soil quality and promote plant growth, as well as to adsorb pollutants from water. However, information about the effect of biochar on the wastewater treatment efficiency in horizontal subsurface flow (HSSF) constructed wetlands (CWs) is still scarce. In this study, we assessed the effect of biochar amendment on the purification efficiency of pretreated municipal wastewater in planted (Typha latifolia) experimental horizontal subsurface flow filters filled with lightweight expanded clay aggregates (LECA). The addition of wood-derived biochar (10% v/v) to LECA significantly increased plant biomass production and enhanced the wastewater treatment efficiency of the planted filters. Both the aboveground plant biomass and belowground plant biomass were higher (1.9- and 1.5-fold, respectively) in the filters of the LBP (LECA + biochar + plants) treatments compared to the LP (LECA + plants) filters. The water pH was significantly lower in the planted filters (LBP < LP < LB-LECA + biochar). The efficiencies of TN and TP removal from wastewater were highest in the LBP filters (20.0% and 22.5%, respectively), followed by the LP (13.7% and 16.2%, respectively) and LB (9.5% and 15.6%, respectively) filters. More N and P were incorporated into the plant biomass from wastewater in the presence of biochar in the filter medium. The study results confirm that biochar can be an advantageous supplement for planted HSSF CWs to enhance the treatment efficiency of these systems.
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31647. 题目: Arsenic speciation dynamics in paddy rice soil-water environment: sources, physico-chemical, and biological factors - A review
文章编号: N18052906
期刊: Water Research
作者: Prasanna Kumarathilaka, Saman Seneweera, Andrew Meharg, Jochen Bundschuh
更新时间: 2018-05-29
摘要: Rice is the main staple carbohydrate source for billions of people worldwide. Natural geogenic and anthropogenic sources has led to high arsenic (As) concentrations in rice grains. This is because As is highly bioavailable to rice roots under conditions in which rice is cultivated. A multifaceted and interdisciplinary understanding, both of short-term and long-term effects, are required to identify spatial and temporal changes in As contamination levels in paddy soil-water systems. During flooding, soil pore waters are elevated in inorganic As compared to dryland cultivation systems, as anaerobism results in poorly mobile As(V), being reduced to highly mobile As(III). The formation of iron (Fe) plaque on roots, availability of metal (hydro)oxides (Fe and Mn), organic matter, clay mineralogy and competing ions and compounds (PO4 3- and Si(OH)4) are all known to influence As(V) and As(III) mobility in paddy soil-water environments. Microorganisms play a key role in As transformation through oxidation/reduction, and methylation/volatilization reactions, but transformation kinetics are poorly understood. Scientific-based optimization of all biogeochemical parameters may help to significantly reduce the bioavailability of inorganic As.
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31648. 题目: Determining major factors controlling phosphorus removal by promising adsorbents used for lake restoration: A linear mixed model approach
文章编号: N18052905
期刊: Water Research
作者: A. Funes, F.J. Martínez, I. ?lvarez-Manzaneda, J.M. Conde-Porcuna, J. de Vicente, F. Guerrero, I. de Vicente
更新时间: 2018-05-29
摘要: Phosphorus (P) removal from lake/drainage waters by novel adsorbents may be affected by competitive substances naturally present in the aqueous media. Up to date, the effect of interfering substances has been studied basically on simple matrices (single-factor effects) or by applying basic statistical approaches when using natural lake water. In this study, we determined major factors controlling P removal efficiency in 20 aquatic ecosystems in the southeast Spain by using linear mixed models (LMMs). Two non-magnetic -CFH-12 and Phoslock - and two magnetic materials -hydrous lanthanum oxide loaded silica-coated magnetite (Fe-Si-La) and commercial zero-valent iron particles (FeHQ)- were tested to remove P at two adsorbent dosages. Results showed that the type of adsorbent, the adsorbent dosage and color of water (indicative of humic substances) are major factors controlling P removal efficiency. Differences in physico-chemical properties (i.e. surface charge or specific surface), composition and structure explain differences in maximum P adsorption capacity and performance of the adsorbents when competitive ions are present. The highest P removal efficiency, independently on whether the adsorbent dosage was low or high, were 85–100% for Phoslock and CFH-12 , 70–100% for Fe-Si-La and 0–15% for FeHQ. The low dosage of FeHQ, compared to previous studies, explained its low P removal efficiency. Although non-magnetic materials were the most efficient, magnetic adsorbents (especially Fe-Si-La) could be proposed for P removal as they can be recovered along with P and be reused, potentially making them more profitable in a long-term period.
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31649. 题目: Impact of inorganic ions and natural organic matter on arsenates removal by ferrate(VI): Understanding a complex effect of phosphates ions
文章编号: N18052904
期刊: Water Research
作者: Jan Kola?ík, Robert Prucek, Ji?í Tu?ek, Jan Filip, Virender K. Sharma, Radek Zbo?il
更新时间: 2018-05-29
摘要: Arsenic compounds are carcinogenic to humans and are typically removed from contaminated water using various sorbents. The ionic composition plays a significant role in arsenate removal efficiency during the process of water remediation. Here, we quantify the effects of natural ions (chlorides, nitrates, carbonates, sulfates, and phosphates) and humic acid on the removal of arsenates by ferrate(VI) at pH = 6.6. In the experiments, the initial concentration of arsenates was 10 mg L-1 (as As) and the concentrations of ions varied in the range from 5 to 100 mg L-1 of element in ionic form and humic acid. The achieved results show that only phosphate ions had principle influence on the efficiency of arsenate removal by ferrate(VI). The effect of phosphates was elucidated by applying transmission electron microscopy, energy-dispersive X-ray spectroscopy, and low temperature in-field 57Fe M ssbauer spectroscopy to solid samples, prepared under different weight ratios of ferrate(VI), arsenates, and phosphates. These results show three crucial effects of phosphates on the arsenate removal mechanisms. At low P:As weight ratio (up to 1:1), the incorporation of arsenate ions into the crystalline structure of γ-Fe2O3/γ-FeOOH nanoparticles was found to be suppressed by the presence of phosphates. Thus, arsenates were mainly adsorbed onto the surface of γ-Fe2O3/γ-FeOOH nanoparticles. Further increase in the P:As weight ratio (more than 1:1) resulted in the competition between arsenates and phosphates sorption. With the increased concentration of phosphate ions, the number of arsenates on the surface of γ-Fe2O3/γ-FeOOH nanoparticles was reduced. Finally, the complexation of iron(III) ions with phosphate ions occurred, leading to a decrease in the arsenates removal efficiency, which resulted from a lower content of precipitated γ-Fe2O3/γ-FeOOH nanoparticles. All these aspects need to be considered prior to application of ferrate(VI) for arsenates removal in real natural waters.
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31650. 题目: Interaction of calcium, phosphorus and natural organic matter in electrochemical recovery of phosphate
文章编号: N18052903
期刊: Water Research
作者: Yang Lei, Bingnan Song, Michel Saakes, Renata D. van der Weijden, Cees J.N. Buisman
更新时间: 2018-05-29
摘要: To address the issues of eutrophication and the potential risk of phosphorus (P) shortage, it is essential to remove and recover P from P-containing streams to close this nutrient cycle. Electrochemical induced calcium phosphate (CaP) precipitation was shown to be an efficient method for P recovery. However, the influence of natural organic matter (NOM) is not known for this treatment. In this paper, the behavior of NOM and its effect on CaP precipitation was studied. In contrast to studies where NOM hindered CaP precipitation, results show that the interaction of NOM with CaP improves the removal of P, independent of the types of NOM. The P removal at the average increased from 43.8 ± 4.9% to 58.5 ± 1.2% in the presence of 1.0 mg L-1 NOM. Based on the yellow color of the CaP product, NOM is co-precipitated. The bulk solution pH with and without buffers has totally different effects on the precipitation process. Without buffer, CaP precipitates on the cathode surface in a wide pH range (pH 4.0–10.0). However, the precipitation process is completely inhibited when the bulk solution is buffered at pH 4.0 and 6.0. This is probably due to neutralization of OH - by the buffers. Regardless of the presence or absence of NOM and solution pH, the recovered products are mainly amorphous CaP unless the electrolysis time was increased to seven days with 4.0 A m-2, in which crystalline CaP formed. These findings advance our understanding on the interaction of Ca, P and NOM species for the application of electrochemical method for P recovery from real wastewater.
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31651. 题目: New insights into the formation of silver-based nanoparticles under natural and semi-natural conditions
文章编号: N18052902
期刊: Water Research
作者: Andreas Wimmer, Anna Kalinnik, Michael Schuster
更新时间: 2018-05-29
摘要: For the first time, the natural formation of silver-based nanoparticles (Ag-b-NPs) was studied in field investigations of two pre-alpine lakes in Germany that contain geogenic silver traces in the sub-ng L-1 range. Light-sensitive microorganisms most likely accumulate and transport these silver traces from deeper water layers to the surface. At the surface of the eutrophic lake, approximately 40% of total silver (5.7 ng L-1) consisted of Ag-b-NPs, whereas in the oligotrophic lake with similar enrichment of silver species, no Ag-b-NPs were detected. Additional lab experiments with nature-related Ag(I) concentrations in the lower-ng L-1 range and natural organic matter with total organic carbon values of ≤5 mg L-1 revealed that, contrary to common interpretation in the literature, Ag-b-NPs are also or even preferably formed in the dark. Particle size increases gradually with increasing reaction time, showing that Ostwald ripening occurs even at such low particle concentrations. When sulfide ions are present, smaller Ag-b-NPs with a narrower size distribution are formed.
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31652. 题目: The dependence of chlorine decay and DBP formation kinetics on pipe flow properties in drinking water distribution
文章编号: N18052901
期刊: Water Research
作者: Yingying Zhao, Y. Jeffrey Yang, Yu Shao, Jill Neal, Tuqiao Zhang
更新时间: 2018-05-29
摘要: Simultaneous chlorine decay and disinfection byproduct (DBP) formation have been discussed extensively because of their regulatory and operational significance. This study further examines chemical reaction variability in the water quality changes under various hydrodynamic conditions in drinking water distribution. The variations of kinetic constant for overall chlorine decay ( k E ) and trihalomethane (THM) formation were determined under stagnant to turbulent flows using three devices of different wall demand and two types of natural organic matters (NOM) in water. The results from the comparative experiments and modeling analyses show the relative importance of wall demand ( k w ), DBP-forming chlorine decay ( k D ), and other bulk demand ( k b ' ) for pipe flows of Re = 0–52500. It is found that chlorine reactivity of virgin NOM is the overriding factor. Secondly, for tap water NOM of lower reactivity, pipe flow properties (Re or u) can significantly affect k E , the THM yield (T), formation potential (Y), and the time to reach the maximum THM concentration ( t max ) through their influence on kinetic ratio k D ( k b ' + k w ) . These observations, corroborating with turbidity variations during experiments, cannot be explained alone by chlorine dispersion to and from the pipe wall. Mass exchanges through deposition and scale detachment, most likely being flow-dependent, may have contributed to the overall chlorine decay and DBP formation rates. Thus for the simultaneous occurrence of chlorine decay and DBP formation, model considerations of NOM reactivity, pipe types (wall demand), flow hydraulics, and their interactions are essential.
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31653. 题目: Shifts in priming partly explain impacts of long‐term nitrogen input in different chemical forms on soil organic carbon storage
文章编号: N18052503
期刊: Global Change Biology
作者: Minghua Song, Yu Guo, Feihai Yu, Xianzhou Zhang, Guangmin Cao, Johannes H. C. Cornelissen
更新时间: 2018-05-25
摘要: Input of labile organic carbon can enhance decomposition of extant soil organic carbon (SOC) through priming. We hypothesized that long‐term nitrogen (N) input in different chemical forms alters SOC pools by altering priming effects associated with N‐mediated changes in plants and soil microbes. The hypothesis was tested by integrating field experimental data of plants, soil microbes and two incubation experiments with soils that had experienced 10 years of N enrichment with three chemical forms (ammonium, nitrate and both ammonium and nitrate) in an alpine meadow on the Tibetan Plateau. Incubations with glucose–13C addition at three rates were used to quantify effects of exogenous organic carbon input on the priming of SOC. Incubations with microbial inocula extracted from soils that had experienced different long‐term N treatments were conducted to detect effects of N‐mediated changes in soil microbes on priming effects. We found strong evidence and a mechanistic explanation for alteration of SOC pools following 10 years of N enrichment with different chemical forms. We detected significant negative priming effects both in soils collected from ammonium‐addition plots and in sterilized soils inoculated with soil microbes extracted from ammonium‐addition plots. In contrast, significant positive priming effects were found both in soils collected from nitrate‐addition plots and in sterilized soils inoculated with soil microbes extracted from nitrate‐addition plots. Meanwhile, the abundance and richness of graminoids were higher and the abundance of soil microbes was lower in ammonium‐addition than in nitrate‐addition plots. Our findings provide evidence that shifts toward higher graminoid abundance and changes in soil microbial abundance mediated by N chemical forms are key drivers for priming effects and SOC pool changes, thereby linking human interference with the N cycle to climate change.

31654. 题目: Lead Speciation and Association with Organic Matter in Various Particle-Size Fractions of Contaminated Soils
文章编号: N18052502
期刊: Environmental Science & Technology
作者: Gautier Landrot, Saengdao Khaokaew
更新时间: 2018-05-25
摘要: Lead (Pb) stabilization in polluted soils treated by a Pb immobilization technique may be dependent on the speciation of Pb present in specific particle-size fractions of the soil. However, the scale-dependency of Pb speciation in contaminated soils is still not clearly understood. In this study, the natures and amounts of Pb chemical forms were determined in five Pb-polluted soil samples from Klity Village, Thailand, and their particle-size fractions. This was achieved using multiple analytical tools, including bulk extended X-ray absorption fine structure (EXAFS) spectroscopy at the Pb LIII edge. Results suggested that cerussite, Pb sorbed to goethite, and Pb-humate were present in specific amounts in all bulk samples and their particle-size fractions. The highest amounts of Pb-humate were found in the smallest particles of the soil samples. This Pb form was present in the fine particles of a soil sample, but remained undetected when analyzing the bulk sample. Since Pb-SOM association may impede the formation of pyromorphite in soils, the results implied that the extent of Pb immobilization in a polluted soil treated by P may be less than predicted if Pb speciation is only characterized at the macroscopic scale from the bulk soil sample prior remediation.
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31655. 题目: Spatial Associations and Chemical Composition of Organic Carbon Sequestered in Fe, Ca, and Organic Carbon Ternary Systems
文章编号: N18052501
期刊: Environmental Science & Technology
作者: Tyler D. Sowers, Dinesh Adhikari, Jian Wang, Yu Yang, Donald L. Sparks
更新时间: 2018-05-25
摘要: Organo-mineral associations of organic carbon (OC) with iron (Fe) oxides play a major role in environmental OC sequestration, a process crucial to mitigating climate change. Calcium has been found to have high coassociation with OC in soils containing high Fe content, increase OC sorption extent to poorly crystalline Fe oxides, and has long been suspected to form bridging complexes with Fe and OC. Due to the growing realization that Ca may be an important component of C cycling, we launched a scanning transmission X-ray microscopy (STXM) investigation, paired with near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, in order to spatially resolve Fe, Ca, and OC relationships and probe the effect of Ca on sorbed OC speciation. We performed STXM-NEXAFS analysis on 2-line ferrihydrite reacted with leaf litter-extractable dissolved OC and citric acid in the absence and presence of Ca. Organic carbon was found to highly associate with Ca (R2 = 0.91). Carboxylic acid moieties were dominantly sequestered; however, Ca facilitated the additional sequestration of aromatic and phenolic moieties. Also, C NEXAFS revealed polyvalent metal ion complexation. Our results provide evidence for the presence of Fe–Ca–OC ternary complexation, which has the potential to significantly impact how organo-mineral associations are modeled.
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31656. 题目: Tale of Two Storms: Impact of Extreme Rain Events on the Biogeochemistry of Lake Superior
文章编号: N18052403
期刊: Journal of Geophysical Research: Biogeosciences
作者: Ellen M.Cooney, PaulMcKinney, RobertSterner, Gaston E.Small, Elizabeth C.Minor
更新时间: 2018-05-24
摘要: Climate change is expected to profoundly affect the Great Lakes region of North America. An increase in intensity and frequency of rain events is anticipated to deliver more runoff and to increase riverine inputs to Lake Superior's ecosystem. The effects of these changes on key biogeochemical parameters were analyzed by coupling satellite data, water column sensor profiles, and discrete surface‐water sampling after two “500‐year” flood events in the Lake Superior basin. This study provides both a spatial and a temporal sense of how plumes interacted within the ecosystem. We also determined the significant differences in water quality parameters for plume versus nonplume waters. These two plumes were important for delivery of nutrients, with variable transport of sediments and colored dissolved organic matter (CDOM). Data from the 2012 storm event showed a significant input of total nitrogen, total phosphorus, and CDOM to the system. In the 2016 storm event, carbon cycling parameters (acidity, total inorganic carbon, and dissolved organic carbon) and ammonia levels were elevated within the plume. In neither storm event was there a significant difference in chlorophyll a between plume and nonplume waters during our sampling cruises. These two plume events were similar in amount of precipitation, but their effect on the biogeochemistry of Lake Superior varied due to differences in the watersheds where the rain fell. The studied plume events were dynamic, changing with currents, winds, and the settling of suspended sediments.

31657. 题目: Chlorate Formation Mechanism in the Presence of Sulfate Radical, Chloride, Bromide and Natural Organic Matter
文章编号: N18052402
期刊: Environmental Science & Technology
作者: Shaodong Hou, Li Ling, Dionysios D. Dionysiou , Yuru Wang, Jiajia Huang, Kaiheng Guo, Xuchun Li, Jingyun Fang
更新时间: 2018-05-24
摘要: Halides and natural organic matter (NOM) are inevitable in aquatic environment and influence the degradation of contaminants in sulfate radical (SO4 –)-based advanced oxidation processes. This study investigated the formation of chlorate in the coexposure of SO4 –, chloride (Cl–), bromide (Br–) and/or NOM in UV/persulfate (UV/PDS) and cobalt(II)/peroxymonosulfate (Co/PMS) systems. The formation of chlorate increased with increasing Cl– concentration in the UV/PDS system, however, in the Co/PMS system, it initially increased and then decreased. The chlorate formation involved the formation of hypochlorous acid/hypochlorite (HOCl/OCl–) as an intermediate in both systems. The formation was primarily attributable to SO4 – in the UV/PDS system, whereas Co(III) played a significant role in the oxidation of Cl– to HOCl/OCl– and SO4 – was important for the oxidation of HOCl/OCl– to chlorate in the Co/PMS system. The pseudo-first-order rate constants (k′) of the transformation from Cl– to HOCl/OCl– were 3.32 × 10–6 s–1 and 9.23 × 10–3 s–1 in UV/PDS and Co/PMS, respectively. Meanwhile, k′ of HOCl/OCl– to chlorate in UV/PDS and Co/PMS were 2.43 × 10–3 s–1 and 2.70 × 10–4 s–1, respectively. Br– completely inhibited the chlorate formation in UV/PDS, but inhibited it by 45.2% in Co/PMS. The k′ of SO4 – reacting with Br– to form hypobromous acid/hypobromite (HOBr/OBr–) was calculated to be 378 times higher than that of Cl– to HOCl/OCl–, but the k′ of Co(III) reacting with Br– to form HOBr/OBr– was comparable to that of Cl– to HOCl/OCl–. NOM also significantly inhibited the chlorate formation, due to the consumption of SO4 – and reactive chlorine species (RCS, such as Cl·, ClO· and HOCl/OCl–). This study demonstrated the formation of chlorate in SO4 –-based AOPs, which should to be considered in their application in water treatment.
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31658. 题目: Understanding the Role of Extracellular Polymeric Substances on Ciprofloxacin Adsorption in Aerobic Sludge, Anaerobic Sludge, and Sulfate-Reducing Bacteria Sludge Systems
文章编号: N18052401
期刊: Environmental Science & Technology
作者: Huiqun Zhang, Yanyan Jia, Samir Kumar Khanal, Hui Lu , Heting Fang, Qing Zhao
更新时间: 2018-05-24
摘要: Extracellular polymeric substances (EPS) of microbial sludge play a crucial role in removal of organic micropollutants during biological wastewater treatment. In this study, we examined ciprofloxacin (CIP) removal in three parallel bench-scale reactors using aerobic sludge (AS), anaerobic sludge (AnS), and sulfate-reducing bacteria (SRB) sludge. The results showed that the SRB sludge had the highest specific CIP removal rate via adsorption and biodegradation. CIP removal by EPS accounted up to 35. 6 ± 1.4%, 23.7 ± 0.6%, and 25.5 ± 0.4% of total removal in AS, AnS, and SRB sludge systems, respectively, at influent CIP concentration of 1000 μg/L, which implied that EPS played a critical role in CIP removal. The binding mechanism of EPS on CIP adsorption in three sludge systems were further investigated using a series of batch tests. The results suggested that EPS of SRB sludge possessed stronger hydrophobicity (proteins/polysaccharides (PN/PS) ratio), higher availability of adsorption sites (binding sites (n)), and higher binding strength (binding constant (Kb)) between EPS and CIP compared to those of AS and AnS. The findings of this study provide an insight into the role of EPS in biological process for treating CIP-laden wastewaters.
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31659. 题目: Thermodynamic Analysis of Nickel(II) and Zinc(II) Adsorption to Biochar
文章编号: N18052103
期刊: Environmental Science & Technology
作者: Md. Samrat Alam, Drew Gorman-Lewis, Ning Chen, Shannon L. Flynn, Yong Sik Ok, Kurt O. Konhauser, Daniel S. Alessi
更新时间: 2018-05-21
摘要: While numerous studies have investigated metal uptake from solution by biochar, few of these have developed a mechanistic understanding of the adsorption reactions that occur at the biochar surface. In this study, we explore a combined modeling and spectroscopic approach for the first time to describe the molecular level adsorption of Ni(II) and Zn(II) to five types of biochar. Following thorough characterization, potentiometric titrations were carried out to measure the proton (H+) reactivity of each biochar, and the data was used to develop protonation models. Surface complexation modeling (SCM) supported by synchrotron-based extended X-ray absorption fine structure (EXAFS) was then used to gain insights into the molecular scale metal–biochar surface reactions. The SCM approach was combined with isothermal titration calorimetry (ITC) data to determine the thermodynamic driving forces of metal adsorption. Our results show that the reactivity of biochar toward Ni(II) and Zn(II) directly relates to the site densities of biochar. EXAFS along with FT-IR analyses, suggest that Ni(II) and Zn(II) adsorption occurred primarily through proton-active carboxyl (-COOH) and hydroxyl (-OH) functional groups on the biochar surface. SCM-ITC analyses revealed that the enthalpies of protonation are exothermic and Ni(II) and Zn(II) complexes with biochar surface are slightly exothermic to slightly endothermic. The results obtained from these combined approaches contribute to the better understanding of molecular scale metal adsorption onto the biochar surface, and will facilitate the further development of thermodynamics-based, predictive approaches to biochar removal of metals from contaminated water.
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31660. 题目: Insights and Model for Understanding Natural Organic Matter Adsorption onto Mixed Adsorbents
文章编号: N18052102
期刊: Environmental Science & Technology
作者: Siamak Modarresi Mark M. Benjamin
更新时间: 2018-05-21
摘要: Adsorption-based processes are commonly used to remove natural organic matter (NOM) from drinking water sources and thereby mitigate its impacts on other water treatment processes and the quality of the finished water. These processes are complicated by the fact that NOM comprises multiple fractions that can exhibit disparate adsorption behaviors. Prior modeling of NOM adsorption has invariably focused on systems with a single adsorbent, but results presented here demonstrate surprising and counterintuitive behavior in systems containing two or more adsorbents. Specifically, if the sequence of affinities of the different NOM fractions are the same for two adsorbents, then overall adsorption changes monotonically as one adsorbent is gradually replaced by the other. However, if the sequence differs for the two adsorbents, overall adsorption can increase even when the nominally stronger adsorbent is gradually replaced by the weaker one. This work demonstrates and explains such behavior for a particular mixture of adsorbents and introduces a mathematical model that illustrates how other mixtures might behave.
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