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7681. 题目: Shallow ponds are biogeochemically distinct habitats in salt marsh ecosystems
文章编号: N18060117
期刊: Limnology and Oceanography
作者: Amanda C. Spivak, Kelsey M. Gosselin, Sean P. Sylva
更新时间: 2018-06-01
摘要: Runaway expansion of shallow ponds can catalyze the conversion of vegetated marshes into open water environments. Predicting how this transition affects ecosystem functioning is difficult because little is known about pond biogeochemistry. We characterized sediment organic matter sources and transformations in three ponds with different plant communities, over alternating periods of tidal isolation and flushing, during summer and fall, using a combination of stable isotopes, lipid biomarkers, and benthic fluxes. Sediment respiration rates (1.66 ± 0.09 mmol C m-2 d-1 to 28.53 ± 7.76 mmol C m-2 d-1) were comparable to shallow estuaries and driven by sulfate reduction. Rates varied across ponds, reflecting differences in summertime Ruppia maritima and macroalgae abundances, but were similar between seasons. Interactions between aboveground plant and sediment bacterial communities translated into distinct biogeochemical processes across the three ponds. Tidal isolation and summer weather intensified plant and bacterial community effects on pond carbon dynamics, resulting in algal biomass and lipid δ13C values that were 3–12‰ enriched, compared to nearby habitats. Surface sediment organic matter mainly derived from pond microalgae and was compositionally distinct from tidal creeks and marshes. Surprisingly, sediment bacteria were not tightly coupled to benthic microalgae but decomposed multiple carbon sources in surface sediments and became increasingly reliant on buried peat at deeper horizons. Pond development over time could largely be explained by sediment respiration and the simultaneous accretion of the surrounding marsh platform. The role of decomposition in pond expansion is consistent with previous assessments based on whole‐pond metabolism rates. Consequently, future pond expansion could alter ecosystem biogeochemistry and reduce carbon storage.

7682. 题目: Spatiotemporal transformation of dissolved organic matter along an alpine stream flowpath on the Qinghai-Tibetan Plateau: importance of source and permafrost degradation
文章编号: N18060116
期刊: Biogeosciences
作者: Yinghui Wang, Robert G. M. Spencer, David Podgorski, Anne Kellerman, Harunur Rashid, Phoebe Zito, Wenjie Xiao, Dandan Wei, Yuanhe Yang, and Yunping Xu
更新时间: 2018-06-01
摘要: The Qinghai-Tibetan Plateau (QTP) accounts for approximately 70% of global alpine permafrost and is an area sensitive to climate change. The thawing and mobilization of ice and organic carbon-rich permafrost impact hydrologic conditions and biogeochemical processes on the QTP. Despite numerous studies of Arctic permafrost, there are no reports to date for the molecular-level in-stream processing of permafrost-derived dissolved organic matter (DOM) on the QTP. In this study, we examine temporal and spatial changes of chemical composition of DOM and 14C age of dissolved organic carbon (DOC) along an alpine stream (3850–3207m above sea level) by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), accelerator mass spectrometry (AMS) and UV-visible spectroscopy. Compared to downstream sites, the DOM at the headstream exhibited older radiocarbon (14C-DOC) age, higher mean molecular weight, higher aromaticity and fewer polyunsaturated components. At the molecular level, 6409 and 1345 formulas were identified as unique to the active layer (AL) leachate and permafrost layer (PL) leachate, respectively. Comparing permafrost leachates to the downstream site, 59% of AL-specific formulas and 90% of PL-specific formulas were degraded, likely a result of rapid instream degradation of permafrost-derived DOM. From peak discharge in the summer to low flow in late autumn, the DOC concentration at the headstream site decreased from 13.9 to 10.2mg/L, while the 14C-DOC age increased from 745 to 1560 years before present (BP), reflecting an increase in relative contribution of deep permafrost carbon due to the effect of changing hydrological conditions over the course of the summer on DOM source (AL vs. PL). Our study thus demonstrates that hydrological conditions impact the mobilization of permafrost carbon in an alpine fluvial network, the signature of which is quickly lost through in-stream metabolism.

7683. 题目: Evidence of high N2 fixation rates in productive waters of the temperate Northeast Atlantic
文章编号: N18060115
期刊: Biogeosciences
作者: Debany Fonseca-Batista, Xuefeng Li, Virginie Riou, Valérie Michotey, Forian Deman, Fran?ois Fripiat, Sophie Guasco, Natacha Brion, Nolwenn Lemaitre, Manon Tonnard, Morgane Gallinari, Hélène Planquette, Frédéric Planchon, Géraldine Sarthou, Marc Elskens, Lei Chou, and Frank Dehairs
更新时间: 2018-06-01
摘要: Diazotrophic activity and primary production (PP) were investigated along two transects (Belgica BG2014/14 and GEOVIDE cruises) off the western Iberian Margin and the Bay of Biscay (38.8–46.5°N; 8.0–19.7°W) in May 2014 close to the end of the spring bloom. We report substantial N2 fixation activities, reaching up to 65nmolNL-1d-1 and 1533 molNm-2d-1 close to the Iberian Margin between 38.8°N and 40.7°N. Similar figures in the basin have only been reported in the temperate and tropical western North Atlantic waters with coastal, shelf or mesohaline characteristics, as opposed to the mostly open ocean conditions studied here. In agreement with previous studies, the qualitative assessment of nifH gene diversity (encoding the nitrogenase enzyme that fixes N2) suggested a predominance of heterotrophic diazotrophs, and the absence of filamentous cyanobacteria. At the sites where N2 fixation activity was highest sequences affiliated to UCYN-A1, obligate symbiont of eukaryotic prymnesiophyte algae, were recovered. The remaining phylotypes were non-cyanobacterial diazotrophs, known to live in association with suspended particles and zooplankton (i.e., Bacteroidetes, Firmicutes and Proteobacteria). Outside the area of exceptional activity, N2 fixation in the open ocean and at shelf-influenced sites was also relatively high, ranging from 81 to 384 molNm-2d-1, but was undetectable in the central Bay of Biscay. We propose that the unexpectedly high heterotrophic N2 fixation activity recorded at the time of our study was sustained by the availability of phytoplankton derived organic matter (dissolved and/or particulate) resulting from the ongoing to post spring bloom. We pose that this organic material not only sustained bacterial production, but also provided sufficient nutrients essential for the nitrogenase activity (e.g., phosphorus). Dissolved Fe was supplied through atmospheric dust deposition during the month preceding our study and through advection of surface waters from the subtropical region and the shelf area. Our findings stress the need for a more detailed monitoring of the spatial and temporal distribution of oceanic N2 fixation in productive waters of the temperate North Atlantic to better constrain the basin-scale nitrogen input to the ocean inventory.

7684. 题目: Dissolved and colloidal copper in the tropical South Pacific
文章编号: N18060114
期刊: Geochimica et Cosmochimica Acta
作者: Saeed Roshan, Jingfeng Wu
更新时间: 2018-06-01
摘要: Copper (Cu) as a bioactive trace metal in the ocean has widely been studied in the context of chemical speciation. However, this trace metal is extremely understudied in the context of physical speciation (i.e., size- or molecular weight-partitioning), which may help in characterizing dissolved Cu species. In this study, we determine total dissolved Cu (<0.2 μm) distribution and its physical speciation along the US GEOTRACES 2013 cruise, a 4300-km east-west transect in the tropical South Pacific. The distribution of dissolved Cu is rather uniform horizontally and exhibits a linear increase with depth from surface to 2500–3000 m, below which it varies less significantly both vertically and horizontally. Dissolved Cu shows a strong correlation with silicate (SiO4 4-) in the upper 1500 m, which is in agreement with previous studies in other regions. This correlation is weaker but with higher slope at depths below 1500 m, which supports the sedimentary source hypothesis. Although hydrothermal activity at the East Pacific Rise (EPR) does not show a readily evident impact on the dissolved Cu distribution, high-quality data at 2300–2800 m allow for diagnosing a subtle westward decrease in the background-subtracted dissolved Cu component. This component of dissolved Cu poorly correlates with mantle-derived 3He (R2 = 0.41), indicating a possible hydrothermal source for dissolved Cu, in contrast to previous studies. For the first time in a major basin, we also determined the physical speciation of dissolved Cu, which shows that Cu species lighter than 10 kDa (Da = 1 g mol-1) dominate the pool of dissolved Cu (<0.2 μm) below 1000 m with a contribution of 61 ± 6% (fraction of total dissolved). 39 ± 6% of dissolved Cu at depths below 1000 m, thus, occurs in the pool of colloidal matter (10 kDa–0.2 μm). Moreover, using a suite of molecular weight cutoffs indicate that Cu species are distributed between two distinct molecular weight classes: the lighter than 5 kDa and heavier than 300 kDa classes, which form 53 ± 6% and 37 ± 7% of dissolved Cu at 2200–2800 m, respectively. The Cu species with molecular weight between 5 kDa and 300 kDa contribute only to 10 ± 12% of the pool at 2200–2800 m. These results offer new insights into structure, reactivity and bioavailability of oceanic Cu compounds. As an organic-dominating metal, Cu physical speciation may also shed light on size-reactivity spectrum of dissolved organic matter (DOM) in the deep ocean.

7685. 题目: pH-dependence of production of oxidants (Cu(III) and/or HO?) by copper-catalyzed decomposition of hydrogen peroxide under conditions typical of natural saline waters
文章编号: N18060113
期刊: Geochimica et Cosmochimica Acta
作者: Guowei Xing, A. Ninh Pham, Christopher J. Miller, T. David Waite
更新时间: 2018-06-01
摘要: The oxidation and reduction kinetics of copper in natural aquatic systems determines its prevailing redox state, with implication to its toxicity, bioavailability and solubility. When reduced copper(I) co-occurs with ubiquitous hydrogen peroxide (H2O2), their reaction forms an oxidizing intermediate able to affect redox transformation of copper, other transition metals and organic carbon. In this work the kinetics and mechanism of reactions of nanomolar concentrations of copper (Cu) with H2O2 in bicarbonate-buffered 0.7 M NaCl solutions over the pH range from 6.0 to 8.0 have been investigated and a kinetic model developed to assist in understanding the results obtained. While the rate of cuprous ion (Cu(I)) peroxidation did not vary markedly with pH, the rates of both cupric ion (Cu(II)) reduction by H2O2 and the production of oxidative intermediates showed strong pH dependence with both rates observed to increase with increasing pH. The increasing proportion of H2O2 present as the hydroperoxyl anion (HO2 -) with increasing pH plays an important role in these trends. However, in order to adequately describe the behavior observed, it is also necessary to invoke a pH-dependent intrinsic conditional rate constant for the reaction between Cu(II) and HO2 -. The nature of the oxidants formed when Cu(I) is oxidized by H2O2 has been probed by measuring the hydroxylation of phthalhydrazide and the degradation of formate in the absence and presence of probe compounds with well-established reactivity toward hydroxyl radicals (HO ). The results obtained suggest that a higher oxidation state of copper, Cu(III), rather than HO is the key oxidant formed over the pH range of 6.0–8.0. Simulations under conditions relevant to natural saline environments reveal that increase in pH results in acceleration in the H2O2-driven cycling of Cu between +I and +II oxidation states but does not significantly influence the rate of production of Cu(III) with important implication for the geochemistry of copper, other redox active elements and oxidizable organic compounds.

7686. 题目: Sources, transport and sinks of beryllium in a coastal landscape affected by acidic soils
文章编号: N18060112
期刊: Geochimica et Cosmochimica Acta
作者: Mats E. ?str?m, Changxun Yu, Pasi Peltola, Jason K. Reynolds, Peter ?sterholm, Miriam I. Nystrand, Anna Augustsson, Joonas J. Virtasalo, Linda Nordmyr, Antti E.K. Ojala
更新时间: 2018-06-01
摘要: Beryllium (Be) sources, transport and sinks were studied in a coastal landscape where acidic soils (acid sulfate soils) have developed after drainage of fine-grained sulfide-bearing sediments. The study included the determination of total abundance and speciation of Be in a variety of solid and aqueous materials in both the terrestrial and estuarine parts of the landscape. A major feature was that despite normal (background) Be concentration in the sulfide-bearing sediments, the Be leaching from these sediments after O2-exposure and acid sulfate soil development were extensive, with concentrations up to 76 μg L-1 in soil water, 39 μg L-1 in runoff and 12 μg L-1 in low-order streams. These high Be concentrations were mainly in the solution form (i.e., passing a 1 kilodalton filter) and modelled to be dominated by free Be2+. The extensive Be release within, and leaching from the acid sulfate soils was controlled by pH, with a critical value of 4.0 below which the Be concentrations increased strongly. Although plagioclase and mica were most likely the main carriers of Be within these soils, it is suggested that other minerals such as Be hydroxides, Al hydroxides carrying Be, and Be sulfides are the main contributors of the abundance of dissolved Be in the acidic waters. When the acidic and Be-rich creek water was neutralized in the estuary of relatively low salinity, the dominating solution form of Be was removed by transformation to particles, reflected in the suspended particulate matter that had hydroxylamine hydrochloride extractable Be up to 17 mg kg-1 and ammonium acetate EDTA extractable Be up to 4 mg kg-1. In corresponding pristine materials (parent material of the acid sulfate soils) in the catchment, the median Be extractability with these reagents were only 0.3 and 0.05 mg kg-1, respectively. As the Be-rich suspended particulate matter ultimately became benthic sediment, the Be was preserved in terms of total concentrations but underwent to some extent changes in speciation, including release from hydroxides and concomitant scavenging by organic matter and particle surfaces.

7687. 题目: The molecular products and biogeochemical significance of lipid photooxidation in West Antarctic surface waters
文章编号: N18060111
期刊: Geochimica et Cosmochimica Acta
作者: James R. Collins, Helen F. Fredricks, Jeff S. Bowman, Collin P. Ward, Carly Moreno, Krista Longnecker, Adrian Marchetti, Colleen M. Hansel, Hugh W. Ducklow, Benjamin A.S. Van Mooy
更新时间: 2018-06-01
摘要: The seasonal depletion of stratospheric ozone over the Southern Hemisphere allows abnormally high doses of ultraviolet radiation (UVR) to reach surface waters of the West Antarctic Peninsula (WAP) in the austral spring, creating a natural laboratory for the study of lipid photooxidation in the shallow mixed layer of the marginal ice zone. The photooxidation of lipids under such conditions has been identified as a significant source of stress to microorganisms and short-chain fatty acids altered by photochemical processes have been found in both marine aerosols and sinking marine particle material. However, the biogeochemical impact of lipid photooxidation has not been quantitatively compared at ecosystem scale to the many other biological and abiotic processes that can transform particulate organic matter in the surface ocean. We combined results from field experiments with diverse environmental data, including high-resolution, accurate-mass HPLC-ESI-MS analysis of lipid extracts and in situ measurements of ultraviolet irradiance, to address several unresolved questions about lipid photooxidation in the marine environment. In our experiments, we used liposomes—nonliving, cell-like aggregations of lipids—to examine the photolability of various moieties of the intact polar diacylglycerol (IP-DAG) phosphatidylcholine (PC), a structural component of membranes in a broad range of microorganisms. We observed significant rates of photooxidation only when the molecule contained the polyunsaturated fatty acid (PUFA) docosahexaenoic acid (DHA). As the DHA-containing lipid was oxidized, we observed the steady ingrowth of a diversity of oxylipins and oxidized IP-DAG; our results suggest both the intact IP-DAG the degradation products were amenable to heterotrophic assimilation. To complement our experiments, we used an enhanced version of a new lipidomics discovery software package to identify the lipids in water column samples and in several diatom isolates. The galactolipid digalactosyldiacylglycerol (DGDG), the sulfolipid sulfoquinovosyldiacylglycerol (SQDG) and the phospholipids PC and phosphatidylglycerol (PG) accounted for the majority of IP-DAG in the water column particulate (≥0.2 m) size fraction; between 3.4 and 5.3% of the IP-DAG contained fatty acids that were both highly polyunsaturated (i.e., each containing ≥5 double bonds). Using a broadband apparent quantum yield (AQY) that accounted for direct and Type I (i.e., radical-mediated) photooxidation of PUFA-containing IP-DAG, we estimated that 0.7 ± 0.2 mol IP-DAG m-2 d-1 (0.5 ± 0.1 mg C m-2 d-1) were oxidized by photochemical processes in the mixed layer. This rate represented 4.4% (range, 3–21%) of the mean bacterial production rate measured in the same waters immediately following the retreat of the sea ice. Because our liposome experiments were not designed to account for oxidation by Type II photosensitized processes that often dominate in marine phytodetritus, our rate estimates may represent a sizeable underestimate of the true rate of lipid photooxidation in the water column. While production of such diverse oxidized lipids and oxylipins has been previously observed in terrestrial plants and mammals in response to biological stressors such as disease, we show here that a similar suite of molecules can be produced via an abiotic process in the environment and that the effect can be commensurate in magnitude with other ecosystem-scale biogeochemical processes.

7688. 题目: Trace element mobilization during incipient bioweathering of four rock types
文章编号: N18060110
期刊: Geochimica et Cosmochimica Acta
作者: Carmen I. Burghelea, Katerina Dontsova, Dragos G. Zaharescu, Raina M. Maier, Travis Huxman, Mary K. Amistadi, Edward Hunt, Jon Chorover
更新时间: 2018-06-01
摘要: Lithogenic trace element (TE) patterns of distribution, fate, and behavior in soils are influenced by plants and microorganisms. Our controlled mesocosm experiments quantified how incipient weathering of mineral-bound TEs (Be, V, Sr, Ba, Cr, Co, Ni, Mo, Cu, Zn, As, Se, Ag, Cd, Sn, Sb, Tl, and Pb) varies across four porous mineral substrates (basalt, rhyolite, granite, and schist), in the presence of buffalo grass (Bouteloua dactyloides), associated bacteria, and arbuscular mycorrhizal fungi (AM), a common plant symbiont. Particular focus was given to the net transfer of elements between the solid and solution phases, including chemical denudation (loss of element from the rock to the solution), plant TE uptake, and total mobilization (sum of denudation loss and uptake into plant biomass). Results revealed differences in TE denudation among rocks, basalt having the highest loss and schist the lowest. TE leaching in solution was time-dependent and it was likely influenced by variations in pH and DOC that were rock- and treatment-specific. The element with the highest rock-normalized release to the solution and highest enrichment in plant biomass was Mo across all rocks. Plants decreased denudation loss compared to abiotic controls for a large number of TEs in all substrates due to plant uptake, but for some elements increase in weathering due to plant activity resulted in increased denudation. Differences in TE patterns of behavior could be related to their Goldschmidt groups. Plant uptake was controlled by TE availability in solution, as well as plant physiological requirements. Plants and associated microbiota significantly enhanced mobilization for the majority of TEs across all rocks. Mycorrhiza significantly increased above-ground plant biomass production in rhyolite and concentrations in plant tissues for a high number of TEs in basalt. TE uptake into biomass was positively correlated with percent mycorrhizal infection, particularly in basalt and rhyolite. Mycorrhizal fungi also influenced TE denudation, rock-water fractionation, and total mobilization according to the rock type. Mycorrhizal activity was associated with a significant decrease in pH and increase in DOC fluxes in schist, supporting the idea that fungi enhance production of root exudates especially in substrates that are difficult to weather. Our results highlight the importance of incipient weathering at the plant-rock interface for patterns of TE cycling. They also indicate the importance of mycorrhiza in mineral dissolution, TE denudation, plant element uptake, and biomass growth.

7689. 题目: Oxidation of Microcystins by Permanganate: pH and Temperature-Dependent Kinetics, Effect of DOM Characteristics, and Oxidation Mechanism Revisited
文章编号: N18060109
期刊: Environmental Science & Technology
作者: Min Sik Kim, Hye-Jin Lee, Ki-Myeong Lee, Jiwon Seo, Changha Lee
更新时间: 2018-06-01
摘要: Oxidative degradation of six representative microcystins (MCs) (MC-RR, -LR, -YR, -LF, -LW, and -LA) by potassium permanganate (KMnO4; Mn(VII)) was investigated, focusing on the temperature- and pH-dependent reaction kinetics, the effect of dissolved organic matter (DOM), and the oxidation mechanisms. Second-order rate constants for the reactions of the six MCs with Mn(VII) (kMn(VII),MC) were determined to be 160.4–520.1 M–1 s–1 (MC-RR > -LR ≈ -YR > -LF ≈ -LW > -LA) at pH 7.2 and 21 °C. The kMn(VII),MC values exhibited activation energies ranging from 15.1 to 22.4 kJ mol–1. With increasing pH from 2 to 11, the kMn(VII),MC values decreased until pH 5, and plateaued over the pH range of 5–11, except for that of MC-YR (which increased at pH > 8). Species-specific second-order rate constants were calculated using predicted pKa values of MCs. The oxidation of MCs in natural waters was accurately predicted by the kinetic model using kMn(VII),MC and Mn(VII) exposure (∫[Mn(VII)]dt) values. Among different characteristics of DOM in natural waters, UV254, SUVA254, and the abundance of humic-like substances characterized by fluorescence spectroscopy exhibited good correlation with ∫[Mn(VII)]dt. A thorough product study of MC-LR oxidation by Mn(VII) was performed using liquid chromatography–mass spectrometry.

7690. 题目: Environmentally Relevant Freeze–Thaw Cycles Enhance the Redox-Mediated Morphological Changes of Silver Nanoparticles
文章编号: N18060108
期刊: Environmental Science & Technology
作者: Xiaoru Guo, Yongguang Yin, Zhiqiang Tan, Jingfu Liu
更新时间: 2018-06-01
摘要: Silver nanoparticles (AgNPs) are inevitably released into natural systems, particularly into aquatic environments, where they are oxidized and release Ag+, which is reduced back to AgNPs. Environmental freeze–thaw cycles or freezing may accelerate the dynamic transformation between AgNPs and Ag+. Herein, the significant morphological changes caused by freezing treatments were assessed by UV–vis spectroscopy and high-resolution transmission electron microscopy, which revealed that reductive regeneration, particle fusion, and coalescence of the AgNPs occurred. In addition, a stable Ag isotope was used to track the AgNP redox reaction, which was found to be accelerated under freezing and freeze–thaw cycles relative to the reaction of particles stored at a normal temperature (4 °C, 25 °C). Furthermore, natural organic matter was found to stabilize the particle morphology. Ca2+ and Cl– intensified the morphological changes and redox reaction through Ca2+-induced particle coalescence and Cl–-enhanced reduction of Ag+ during the freeze–thaw treatment. These physicochemical changes also occurred for an environmentally relevant concentration of AgNPs (50 ng L–1) in simulated environmental conditions and natural water samples after freeze–thaw cycles. Since the morphological changes and redox acceleration induced by environmental freezing conditions could dramatically influence the mobility, bioavailability, toxicity, and environmental fate of AgNPs, the freeze–thaw-induced effects should be considered in the environmental risk assessment of AgNPs.

7691. 题目: Discrete Organic Phosphorus Signatures are Evident in Pollutant Sources within a Lake Erie Tributary
文章编号: N18060107
期刊: Environmental Science & Technology
作者: M. R. Brooker, K. Longnecker, E. B. Kujawinski, M. H. Evert, and P. J. Mouser
更新时间: 2018-06-01
摘要: Phosphorus loads are strongly associated with the severity of harmful algal blooms in Lake Erie, a Great Lake situated between the United States and Canada. Inorganic and total phosphorus measurements have historically been used to estimate nonpoint and point source contributions, from contributing watersheds with organic phosphorus often neglected. Here, we used ultrahigh resolution mass spectrometry to characterize the dissolved organic matter and specifically dissolved organic phosphorus composition of several nutrient pollutant source materials and aqueous samples in a Lake Erie tributary. We detected between 23 and 313 organic phosphorus formulas across our samples, with manure samples having greater abundance of phosphorus- and nitrogen containing compounds compared to other samples. Manures also were enriched in lipids and protein-like compounds. The greatest similarities were observed between the Sandusky River and wastewater treatment plant effluent (WWTP), or the Sandusky River and agricultural edge of field samples. These sample pairs shared 84% of organic compounds and 59–73% of P-containing organic compounds, respectively. This similarity suggests that agricultural and/or WWTP sources dominate the supply of organic phosphorus compounds to the river. We identify formulas shared between the river and pollutant sources that could serve as possible markers of source contamination in the tributary.

7692. 题目: Polychlorinated diphenyl ethers (PCDEs) in surface sediments, suspended particulate matter (SPM) and surface water of Chaohu Lake, China
文章编号: N18060106
期刊: Environmental Pollution
作者: Xuesheng Zhang, Tantan Wang, Lei Gao, Mingbao Feng, Li Qin, Jiaqi Shi, Danru Cheng
更新时间: 2018-06-01
摘要: Polychlorinated diphenyl ethers (PCDEs) are typical halogenated aromatic pollutants that have shown various toxicological effects on organisms. However, the contamination status of PCDEs in the fresh water lakes of China remains poorly researched. In this study, the levels of 15 congeners of PCDEs in the sediments, suspended particulate matter (SPM) and water of Chaohu Lake were determined. The results showed that the ranges of concentrations of total PCDEs (ΣPCDEs) in the sediment, SPM and water were 0.279 ng g-1 dry weight (d.w.)–2.474 ng g-1 d.w., 0.331 ng g-1 d.w.–2.013 ng g-1 d.w. and 0.351 ng L-1–2.021 ng L-1, respectively. The most abundant congeners found in sediments, SPM and water were 3,3′,4,4′-tetra-CDE, deca-CDE and 2,4,6-tri-CDE, with average contributive ratios of 17.36%, 15.48% and 20.63%, respectively. The medium and higher chlorinated PCDEs (e.g., penta- and deca-CDEs) were the dominant congeners in sediments and SPM. The percentages of lower chlorinated PCDEs (e.g., tri-CDEs) in the water were higher than those in the sediments. The combined input of ΣPCDEs from the eight main tributaries to Chaohu Lake was estimated at 6.94 kg y-1. Strong linear correlations between the concentrations of ΣPCDEs and organic carbon (OC) contents in three type samples from Chaohu Lake suggested OC could influence the distribution of PCDEs in Chaohu Lake substantially. In addition, the calculated average organic carbon normalized partition coefficients (logK oc) of 15 PCDEs between water and SPM were in the range of 4.55–5.45 mL g-1. This study confirmed that Chaohu Lake is contaminated by PCDEs.

7693. 题目: Fabrication of magnetic particles reinforced nano-hydroxyapatite/gelatin composite for selective Cr(VI) removal from water
文章编号: N18060105
期刊: Environmental Science: Water Research & Technology
作者: Venkatrajan Gopalakannan, Soodamani Periyasamy, Natrayasamy Viswanathan
更新时间: 2018-06-01
摘要: The presence of chromium ion in drinking water has been proven to be toxic and carcinogenic. Hence, an attempt has been made to synthesize magnetic Fe3O4 fabricated with nano-hydroxyapatite (n-HAp)/gelatin (Gel) biocomposite by both in situ precipitation (in situ) and hydrothermal (hydro) methods. The hydrothermal-assisted Fe3O4@n-HApGel biocomposite achieved enhanced sorption capacity (SC) compare to the in situ precipitation method. The physico-chemical properties of the as-synthesized adsorbents were thoroughly characterized using various advanced instrumental techniques, namely, FTIR, XRD, SEM, EDAX, TEM and BET surface area analysis. Chromium adsorption mechanism of hydrothermal-assisted Fe3O4@n-HApGel composite was described by electrostatic attraction with surface complexation and reduction. The chromium adsorption behaviour of hydrothermal-assisted Fe3O4@n-HApGel biocomposite was interpreted using Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherms. The thermodynamic experimental data of Fe3O4@n-HApGel biocomposite indicates that the chromium sorption process is endothermic and spontaneous in nature. Fe3O4@n-HApGel composite can be easily recycled for more than 5 cycles using NaOH eluent. In addition, the magnetic biocomposite is also suitable for treating chromium polluted ground water.

7694. 题目: Impact of water quality parameters on bacteria inactivation by low-voltage electroporation: mechanism and control
文章编号: N18060104
期刊: Environmental Science: Water Research & Technology
作者: Zheng-Yang Huo, Guo-Qiang Li, Tong Yu, Yun Lu, Hao Sun, Yin-Hu Wu, Cecilia Yu, Xing Xie, Hong-Ying Hu
更新时间: 2018-06-01
摘要: Nanowire-assisted low-voltage electroporation enables efficient and energy-conserving bacteria inactivation without byproduct formation. This approach is promising for replacing traditional methods for reliable water disinfection. Nevertheless, studies of applying this approach to different water matrices have not yet been done. Here, we study the effect of primary water quality parameters (pH, ionic strength, ion type, and organic matters) on the effectiveness of bacteria inactivation by low-voltage electroporation. Our results show that while pH, ionic strength, and ion type cause little impact, high concentration (>5 mg L-1) of macromolecular organic matter (>5000 g mol-1) hampers the disinfection performance. These macromolecular organic matters tend to accumulate around or attach to the nanowires and hinder the bacteria from reaching the regions with enhanced electric field strength where inactivation occurs. Electrochemical reduction of the organic matters further reduces their solubility, resulting in more precipitation on the nanowires. To reduce such negative impacts, we have proposed and verified that applying alternating current instead of direct current can slow down the accumulation and electrochemical precipitation.

7695. 题目: Degradation mechanisms of cefotaxime using biochar supported Co/Fe bimetallic nanoparticles
文章编号: N18060103
期刊: Environmental Science: Water Research & Technology
作者: Hongwei Wu, Qiyan Feng, Ping Lu, Meng Chen, Hong Yang
更新时间: 2018-06-01
摘要: Ecological risks caused by residual antibiotics have increasingly attracted great attention. In this study, a highly efficient novel adsorbent based on Co/Fe bimetallic nanoparticles loaded with alkali modified biochar (Co/Fe/MB) was prepared to remove cefotaxime from an aqueous solution. The prepared composites were characterized with X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effects of Co loading, adsorbent dosage, initial solution pH and anions (Cl-, HCO3- and EDTA) on the removal of cefotaxime were investigated. Due to the synergetic reaction of the adsorption and reduction mechanism, Co/Fe/MB revealed the highest cefotaxime removal efficiency (99.23%) in 100 min at the condition of pH = 5, T = 298 K, Co/Fe/MB dosage = 0.8 g L-1, Co loading = 0.4 wt%, cefotaxime = 20 mg L-1. The removal efficiency was further enhanced in the presence of EDTA and Cl- because of the destruction of a passivation layer on iron surface. Additionally, the degradation products and possible degradation pathway of cefotaxime by Co/Fe/MB were analyzed by high performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI-MS). The spectra revealed that the opening and cleavage of the β-lactam ring was the first step for cefotaxime degradation. The Co/Fe/MB composite was found to be an efficient material to remove cefotaxime from the solution.

7696. 题目: Carbon biogeochemistry of a flooded Pantanal forest over three annual flood cycles
文章编号: N18060102
期刊: Biogeochemistry
作者: Higo J. Dalmagro, Michael J. Lathuillière, Iain Hawthorne, Douglas D. Morais, Osvaldo B. Pinto Jr, Eduardo G. Couto, Mark S. Johnson
更新时间: 2018-06-01
摘要: The Pantanal is the largest wetland in the world and yet little is known about the variability in carbon (C) dynamics across its flood seasons. We examined the effect of inundation on the C cycle in the 2013–2015 flood cycles illustrated by dissolved CO2, CH4, organic C (DOC) concentration measurements, and optical properties of dissolved organic matter (DOM) evaluated by absorbance and fluorescence spectroscopy with parallel factor analysis (PARAFAC). During the 2015 flood cycle, pCO2 varied between 5973 and 14,292 μatm, with pCH4 concentrations ranging between 2956 and 51,675 μatm respectively, with high temporal variability for both gases. The supersaturation of CO2 and CH4 in relation to the atmospheric equilibrium caused the system to behave as a net source of CO2 and CH4 to the atmosphere with evasion rates of 320 mg CO2 m-2 d-1 and 20 mg CH4 m-2 d-1, respectively. Mean DOC concentration was 7.0 ± 0.4 mg L-1 and did not differ between flood cycles. Higher concentrations of DOC were measured at the start (rising floodwaters) and at the end (receding floodwaters) of flood cycles, while lower DOC concentrations were observed during the peak flood. The PARAFAC analysis indicated the presence of five DOM components: humic (C1 and C2) and fulvic type material (C3) showed the highest relative abundance (68.5% of the total PARAFAC component fluorescence), as well as protein-like material (C4 and C5) derived from microorganisms. Our measured diffusive flux levels were below the range of emissions found for wetlands and floodplains for CO2, but were slightly higher for CH4 relative to other studies in lakes and seasonally flooded areas of the Pantanal. The large variations in concentrations of CO2, CH4 and DOC and the optical properties of DOM during the course of each flood cycle suggest a close relationship between carbon and water cycles in this tropical wetland.

7697. 题目: High variability in iron-bound organic carbon among five boreal lake sediments
文章编号: N18060101
期刊: Biogeochemistry
作者: Simone Peter, Sebastian Sobek
更新时间: 2018-06-01
摘要: Being both stable carbon sinks and greenhouse gas sources, boreal lake sediments represent significant players in carbon (C) cycling. The release of dissolved organic carbon (DOC) into anoxic water is a widespread phenomenon in boreal lakes with impact on sediment C budgets. The association of OC with iron (Fe) is assumed to play an important role for this anoxic OC release via the dissimilatory reduction of Fe, but also to influence the stabilization of OC in sediments. To investigate the role of Fe–OC association for OC dynamics in different boreal lake sediments, we compared the content of Fe-bound OC [Fe–OC, defined as citrate bicarbonate dithionite (CBD) extractable OC] and the extent of reductive dissolution of solid-phase Fe and OC at anoxia. We found high among-lake variability in Fe–OC content, and while the amount of Fe–OC was high in three of the lakes (980–1920 mol g-1), the overall contribution of Fe–OC to the sediment OC pool in all study lakes was not higher than 11%. No linkages between the amount of the Fe–OC pool and lake or sediment characteristics (e.g., pH, DOC concentration, sediment OC content, C:N ratio) could be identified. The observed release of OC from anoxic sediment may be derived from dissolution of Fe–OC in the lake sediments with high Fe–OC, but in other lake sediments, OC release during anoxia exceeded the sediment Fe–OC pool, indicating low contribution of reductive Fe dissolution to OC release from these lake sediments. The range of the investigated boreal lakes reflects the high variability in the size of the sediment Fe–OC pool (0–1920 mol g-1) and CBD-extractable Fe (123–4050 mol g-1), which was not mirrored in the extent of reductive dissolution of Fe (18.9–84.6 mol g-1) and OC (1080–1700 mol g-1) during anoxia, suggesting that Fe-bound OC may play a minor role for sediment OC release in boreal lakes. However, studies of redox-related OC cycling in boreal lake sediments should consider that the amount of Fe–OC can be high in some lakes.

7698. 题目: Adsorption-desorption and degradation of insecticides clothianidin and thiamethoxam in agricultural soils
文章编号: N18053107
期刊: Chemosphere
作者: Yang Li, Peidong Su, Yadong Li, Kejun Wen, Guihong Bi, Michael Cox
更新时间: 2018-05-31
摘要: Studied were the adsorption-desorption and degradation of two widely used neonicotinoid insecticides clothianidin and thiamethoxam in three different agricultural soils in the state of Mississippi. The adsorptions of both the neonicotinoids fit a linear isotherm model. In different soils at different depths with different moisture contents, the adsorption distribution coefficients of clothianidin and thiamethoxam were found to be 0.62 to 1.94 and 0.59–2.03 L kg-1, respectively. These distribution coefficients showed strong positive correlations with organic carbon content and pH of the soils. The desorptions of clothianidin and thiamethoxam also followed a linear isotherm, but were irreversible in respect to their adsorption isotherms. The desorption distribution coefficients ranged from 0.14 to 0.62 L kg-1, increased with the decrease of organic carbon content. The degradations of clothianidin and thiamethoxam in the soils were found to be slow with half-lives ranged from 90 to 280 and 65 to 170 d for clothianidin and thiamethoxam respectively. The degradation rates increased with the increase of the organic carbon content in the soils. The moisture content in the soils had a positive effect on the degradation rates. The Groundwater Ubiquity Scores calculated from the adsorption distribution coefficient, organic content, and half-life suggest that clothianidin and thiamethoxam have moderate to high potential to leach to groundwater.

7699. 题目: Bioindication of human-induced soil degradation in enclosed karst depressions (dolines) using Ellenberg indicator values (Classical Karst, Slovenia)
文章编号: N18053106
期刊: Science of The Total Environment
作者: Mateja Breg Valjavec, Matija Zorn, Andra? ?arni
更新时间: 2018-05-31
摘要: One of the frequently used bioindication methods is Ellenberg indicator values (EIVs), which are commonly applied in Central Europe as bioindicators of ecological characteristics. However, very few studies have tested EIVs as a bioindication of human-induced soil degradation. We tested the ability of EIVs to distinguish between localities of degraded karst depressions (dolines) and localities of semi-natural (agricultural) soils in preserved dolines on the Kras Plateau (Classical Karst, SW Slovenia). We compared the results of bioindications of soil nutrient content (N), soil reaction (R) and soil moisture (M) with measured soil parameters. Low values of organic carbon, a slightly alkaline soil reaction and low organic sulphur content are chemical indicators of soil degradation in dolines, in comparison with preserved reference dolines (high organic carbon, slightly acid reaction, higher S). EIV reaction is the most reliable plant indicator value that can distinguish between degraded and non-degraded soil plots. According to a regression tree, sulphur (S) and C/N are the most important factors for division on the basis of EIV reaction. By applying the EIV reaction of diagnostic plant species, we significantly improved bioindication of soil degradation, although in the case of EIV nutrients, bioindication was not improved.

7700. 题目: Direct oxygen uptake from air by novel glycogen accumulating organism dominated biofilm minimizes excess sludge production
文章编号: N18053105
期刊: Science of The Total Environment
作者: Md Iqbal Hossain, Andrea Paparini, Ralf Cord-Ruwisch
更新时间: 2018-05-31
摘要: The cost associated with treatment and disposal of excess sludge produced is one of the greatest operational expenses in wastewater treatment plants. In this study, we quantify and explain greatly reduced excess sludge production in the novel glycogen accumulating organism (GAO) dominated drained biofilm system previously shown to be capable of extremely energy efficient removal of organic carbon (biological oxygen demand or BOD) from wastewater. The average excess sludge production rate was 0.05 g VSS g-1 BOD (acetate) removed, which is about 9-times lower than that of comparative studies using the same acetate based synthetic wastewater. The substantially lower sludge yield was attributed to a number of features such as the high oxygen consumption facilitated by direct oxygen uptake from air, high biomass content (21.41 g VSS L-1 of reactor), the predominance of the GAO (Candidatus competibacter) with a low growth yield and the overwhelming presence of the predatory protozoa (Tetramitus) in the biofilm. Overall, the combination of low-energy requirement for air supply (no compressed air supply) and the low excess sludge production rate, could make this novel “GAO drained biofilm” process one of the most economical ways of biological organic carbon removal from wastewater.

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