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13301. 题目: Copper-binding ligands in the NE Pacific
文章编号: N180625F4
期刊: Marine Chemistry
作者: Hannah Whitby, Anna M. Posacka, Maria T. Maldonado, Constant M.G. van den Berg
更新时间: 2018-06-25
摘要: Copper distribution and speciation were determined at stations P4 and P26 along Line P as part of a GEOTRACES Process Study in the Northeast Pacific, at depths between 10 and 1400 m. Two ligand classes (L1 and L2) were detected at both stations: the stronger L1 ligand pool with log K'Cu2+L1 15.0–16.5 and the weaker L2 ligand pool with log K'Cu2+L2 11.6–13.6. The L1 class bound on average 94% of dCu, with the ratio between L1 and dCu constant and close to unity (1.15 = [L1]:[dCu]). The concentrations of total ligands exceeded those of dCu at all depths, buffering Cu2+ concentrations ([Cu2+]) to femtomolar levels (i.e. pCu 14.1–15.7). Measurements using cathodic stripping voltammetry also identified natural copper-responsive peaks, which were attributed to thiourea- and glutathione-like thiols (TU and GSH, respectively), and Cu-binding humic substances (HSCu). Concentrations of TU, GSH and HSCu were determined by standard addition of model compounds in an attempt to identify Cu-binding ligands. HSCu concentrations were generally higher at P26 than at P4, consistent with a marine origin of the humic material. Overall, HSCu contributed to 1–27% of the total L concentration (LT) and when combined with the two thiols contributed to up to 32% of LT. This suggests other ligand types are responsible for the majority of dCu complexation in these waters, such as other thiols. Some potential candidates for detected, but unidentified, thiols are cysteine, 3-mercaptopropionic acid and 2-mercaptoethanol, all of which bind Cu. Significant correlation between the concentrations of TU-like thiols and L1, along with the high log K'Cu2+L1 values, tentatively suggest that the electrochemical TU-type peak could be part of a larger, unidentified, high-affinity Cu compound, such as a methanobactin or porphyrin, with a stronger binding capability than typical thiols. This could imply that chalkophores may play a greater role in oceanic dCu complexation than previously considered.

13302. 题目: DDT and related compounds in pore water of shallow sediments on the Palos Verdes Shelf, California, USA
文章编号: N180625F3
期刊: Marine Chemistry
作者: Robert P. Eganhouse, Erica DiFilippo, James Pontolillo, William Orem, Paul Hackley, Brian D. Edwards
更新时间: 2018-06-25
摘要: For nearly two and a half decades following World War II, production wastes from the world's largest manufacturer of technical DDT (1-chloro-4-[2,2,2-trichloro-1-(4-chlorophenyl)ethyl]benzene) were discharged into sewers of Los Angeles County. Following treatment, the wastes were released via a submarine outfall system to nearshore coastal waters where a portion accumulated in shallow sediments of the Palos Verdes Shelf (PVS). An investigation of the pore-water geochemistry of DDT-related compounds (DDX) was undertaken in an effort to understand factors controlling the rate of reductive dechlorination (RDC) of the major DDT degradate, 4,4′-DDE (1-chloro-4-[2,2-dichloro-1-(4-chlorophenyl)ethenyl]benzene). Equilibrium matrix-solid phase microextraction (matrix-SPMEeq) combined with automated thermal desorption-gas chromatography/mass spectrometry (TD-GC/MS) was used to determine freely dissolved concentrations of ten DDX analytes in sediment cores collected from three locations on the PVS (stations 3C, 6C, 8C, which are 7 km, 2 km, and 0 km, respectively, downcurrent from the outfall system). Pore-water concentrations (pM) of the principal DDX compounds involved in RDC were: 3C-DDE: 6.0–24, DDMU (1-chloro-4-[2-chloro-1-(4-chlorophenyl)ethenyl]benzene): 11–160, DDNU (1-chloro-4-[1-(4-chlorophenyl)ethenyl]benzene): 1.8–68; 6C-DDE: 5.6–170, DDMU: 5.6–177, DDNU: 1.7–87; 8C-DDE: 27–212, DDMU: 31–403, DDNU: 5.5–89. Variations in the spatial distribution of DDX analytes in pore water reflect several factors including proximity to the outfalls, RDC reaction rates, and natural variability in sedimentation and post-depositional transport processes. A comparison of pore-water data produced using matrix-SPMEeq/TD-GC/MS and whole-core squeezing/solvent extraction/liquid injection-GC/MS indicates that the majority of the DDE in the upper sediment column (≤about 10 cm) is associated with dissolved/colloidal organic matter. Below that depth, freely-dissolved DDE predominates. The principal organic geochemical phase controlling sorption of DDE in PVS sediments are residual hydrocarbons, the vast majority of which originated from petroleum refinery wastes. Organic carbon-normalized sediment-water distribution coefficients (K OC) were calculated from solid-phase and pore-water concentrations of DDX and organic carbon. Log K OC values (L/kg) were relatively invariant across the shelf and with depth in the sediment column. Shelf-wide compound-specific coefficients (log K OC) were: DDE: 7.5 ± 0.11, DDMU: 6.92 ± 0.13, DDNU: 6.37 ± 0.19. The spatial uniformity of K OC means that biological exposure and availability of the DDX compounds can, in principle, be estimated from solid-phase chemical measurements.

13303. 题目: Dissolved organic matter dynamics in Mediterranean lagoons: The relationship between DOC and CDOM
文章编号: N180625F2
期刊: Marine Chemistry
作者: A. Specchiulli, L. Cilenti, R. D'Adamo, A. Fabbrocini, W. Guo, L. Huang, A. Lugliè, B.M. Padedda, T. Scirocco, P. Magni
更新时间: 2018-06-25
摘要: Coastal lagoons are highly vulnerable to climate change-related pressures, such as floods and increasing temperatures, which lead to higher oxygen consumption, anaerobic metabolism and dystrophic events. Although these factors have a significant impact on the carbon cycle, the dynamics of dissolved organic matter (DOM) in these systems have not been extensively investigated. DOM can be analytically determined from the concentration of dissolved organic carbon (DOC) and/or from the spectral properties of chromophoric dissolved organic matter (CDOM), which is the light-absorbing fraction of DOM. In the present study, we investigated the spatio-temporal distribution of surface water trophic variables (Chl a and DOC) and CDOM in two Mediterranean lagoon systems, the Oristano Lagoon-Gulf system (OLG) and the Varano Lagoon (VL), in order to provide quantitative information on the dynamics of DOM in these systems. Furthermore, we assessed the value of CDOM-related indices (i.e. absorption coefficients, spectral slopes and Specific UV Absorbance at 254 nm [SUVA254]) as tools for describing the dynamics of DOM in coastal lagoons, irrespective of geographical settings, environmental conditions and anthropogenic pressures. In OLG, spatial heterogeneity and compartmentalization, with salinity varying from <1 (riverine sites) to >50 (Mistras Lagoon), affected the distribution of DOC and CDOM, with the lowest values on the south side and at sites far from riverine input. In OLG, the highest DOC and CDOM values were found in the sediment pore-water of the organic-rich Cabras Lagoon, where they were nearly double those of the water column. In VL, salinity was homogeneously distributed throughout the lagoon, which indicated a mixing of freshwater with marine waters. DOC and CDOM values were on average lower in VL than in OLG. However, in VL, DOC and CDOM showed strong peaks following a flood (September 2014) and a dystrophic event (July 2015), demonstrating the quick response of the system to environmental perturbation. In OLG, absorption coefficients at 280 nm and 350 nm were slightly negatively correlated with salinity, which indicated the influence of terrigenous inputs at riverine sites. In contrast, in VL, CDOM varied linearly and positively with salinity as a result of the in situ input of organic matter from phytoplankton during the dry season. Segment analysis showed that besides the differences between the two investigated systems, the trophic variables and optical parameters analyzed in the present study shared a common relationship. These results suggest that CDOM indices can be good predictors for the estimation of DOM. Overall, the present study provides insight into the dynamics of DOC and CDOM in little-studied Mediterranean lagoons and demonstrates that the CDOM indices can be a valuable, cost-effective and simple tool for describing the trophic conditions of these systems.

13304. 题目: Fe(II) oxidation kinetics in the North Atlantic along the 59.5°?N during 2016
文章编号: N180625F1
期刊: Marine Chemistry
作者: Carolina Santana-González, J. Magdalena Santana-Casiano, Melchor González-Dávila, Angelo Santana-del Pino, Sergey Gladyshev, Alexey Sokov
更新时间: 2018-06-25
摘要: The Fe(II) oxidation rate was studied in different water masses present in the subarctic North Atlantic ocean along the 59.5° N transatlantic section. Temperature, pH, salinity and total organic carbon (TOC) in natural conditions, fixed temperature conditions and both fixed temperature and pH conditions, were considered in order to understand the combined effects of the variables that control the Fe(II) oxidation kinetics in the ocean. The study shows that in natural conditions, temperature was the master variable which controlled 75% of the pseudo-first order kinetics rate (k′). This value rose to 90% when pHF (free scale) and salinity were also considered. At a fixed temperature, 72% of k′ was controlled by pH and at both fixed temperature and pH, salinity controled 62% of the Fe(II) oxidation rate. Sources and characteristics of TOC are important factors influencing the oxidation of Fe(II). The organic matter had both positive and negative effects on Fe(II) oxidation. In surface and coastal waters, TOC accelerated k′, decreasing the Fe(II) half-life time (t1/2). In Subpolar Mode Water, Labrador Sea Water (for the Irminger Basin) and Denmark Straight Overflow Water, TOC slowed down k′, increasing Fe(II) t1/2. This shifting behaviour where TOC affects Fe(II) oxidation depending on its marine or terrestrial origin, depth and remineralization stage proves that TOC cannot be used as a variable in an equation describing k′. The temperature dependence study indicated that the energy requirement for Fe(II) oxidation in surface waters was 32% lower than the required for bottom waters at both pH 7.7 and 8.0. This variability confirmed the importance of the organic matter composition of the selected samples. The Fe(II) oxidation rate constants in the region can be obtained from an empirical equation considering the natural conditions of temperature, pHF and salinity for the area, producing an error of estimation of 0.0072 min 1. This equation should be incorporated in global Fe models.

13305. 题目: First report on vertical distribution of dissolved polyunsaturated aldehydes in marine coastal waters
文章编号: N180625F0
期刊: Marine Chemistry
作者: A. Bartual, S. Morillo-García, M.J. Ortega, A. Cózar
更新时间: 2018-06-25
摘要: Polyunsaturated aldehydes (PUA) are bioactive molecules released by phytoplankton cells which can modify phytoplankton trophic interactions with grazers, bacteria or coexisting phytoplankters. Their ecological significance is still a matter of debate. There have been reports of PUA producers having been investigated at the ocean surface in both coastal and open areas, but there is little information regarding natural ranges and distribution of dissolved PUA (dPUA) once they are released. In this report, we provide novel information regarding vertical profiles of dPUA for a coastal area under two different hydrodynamical conditions (mixing and stratified waters). Results show significant concentrations of dPUA ranging from 0.061 nM to 1.87 nM during both periods. This data demonstrate a significant consistency of these compounds in coastal areas and may prove an indirect evidence of high turnover rates in seawater. The vertical distribution of dPUA showed high variability in stratification, and for the first time we describe “patches” of relatively high dPUA concentrations in the upper layer. We hypothesize that these patches of dPUA, correlated to the flow of phytoplankton-derived sinking organic matter, could be significant for increasing the turnover rates of nutrients by triggering bacterial metabolism.

13306. 题目: Interactions between iron and organic carbon in a sandy beach subterranean estuary
文章编号: N180625E9
期刊: Marine Chemistry
作者: Maude Sirois, Mathilde Couturier, Andrew Barber, Yves Gélinas, Gwéna?lle Chaillou
更新时间: 2018-06-25
摘要: Understanding the behavior of terrestrially derived dissolved organic carbon (DOC) through subterranean estuaries (STEs) is essential for determining the carbon budget in coastal waters. However, few studies exist on the interaction of organic carbon (OC) and iron (Fe) in these dynamic systems, where fresh groundwater mixes with recirculated seawater. Here, we focused on the origin and behavior of DOC, and we quantified the relative proportion of OC trapped by reactive Fe-hydroxides along a sandy beach STE. The δ13C-DOC signal in beach groundwater seems to respond rapidly to OC inputs. Our results show a terrestrial imprint from the aquifer matrix dominated by the degradation of particulate organic carbon (POC) issue from an old soil horizon composed of terrestrial plant detritus (14C dating ~800 to 700 years B.P) which is buried below the Holocene sand. Even though the system can be sporadically affected by massive inputs of marine OC, this transient marine imprint seems to be rapidly evacuated from the STE. As reported in soil and in marine mud, Fe–OC trapping occurs in the sandy sediment of the STE. At the groundwater–seawater interface, newly precipitated reactive Fe-hydroxides interact with and trap terrestrial OC independently of the DOC origin in beach groundwater. The molecular fractionation of DOC along the STE and preferential trapping of terrestrial compounds favor the in situ degradation and/or export of non-Fe-stabilized marine-derived molecules to coastal waters. These findings support the idea that the sandy beach STE acts as a transient sink for terrestrial OC at the land–sea interface and contributes to the regulation of marine vs. terrestrial carbon exports to coastal waters.

13307. 题目: Investigating the sources and structure of chromophoric dissolved organic matter (CDOM) in the North Pacific Ocean (NPO) utilizing optical spectroscopy combined with solid phase extraction and borohydride reduction
文章编号: N180625E8
期刊: Marine Chemistry
作者: Carmen M. Cartisano, Rossana Del Vecchio, Marla R. Bianca, Neil V. Blough
更新时间: 2018-06-25
摘要: Prior optical measurements of waters in the Equatorial Atlantic Ocean (EAO) provided evidence of a major terrestrial “humic-like” component of the CDOM that absorbed in the ultraviolet (UV) and visible and emitted across the visible, along with a marine component that primarily absorbed and emitted in the UV. Here we extend these measurements to the North Pacific Ocean (NPO) at Station Aloha (22o 45′ N, 158o 00′ W). Detailed optical measurements of both the natural waters (CDOM) and C18 organic matter extracts of these waters (C18-OM) were acquired before and after sodium borohydride (NaBH4) reduction of samples obtained throughout the water column. Optical properties of the “humic-like” component were relatively uniform with depth below ~600 m [aCDOM(350) ~ 0.08 (m 1), a*CDOM (350) ~ 0.2 (m 1 mg 1C L), SUVA254 ~ 0.55 (m 1 mg 1C L), E2:E3 ~ 10, S300–700 ~ 0.02 (nm 1), S350–400 ~ 0.012 (nm 1), SR ~1.7, F(350/450) ~ 0.009 (QSE), and 360 ~ 0.026], but were significantly different in surface waters, likely due to photobleaching and biological activity [aCDOM(350) ~ 0.026 (m 1), a*CDOM (350) ~ 0.027 (m 1 mg 1C L), SUVA254 ~ 0.36 (m 1 mg 1C L), E2:E3 ~ 45, S300–700 ~ 0.03 (nm 1), S350–400 ~ 0.003 (nm 1), SR ~6.8, F(350/450) ~ 0.003 (QSE), and 350 ~ 0.024]. Optical properties of the short-wavelength components (UV bands) were more variable with depth. Response to solid phase extraction was also relatively uniform with depth, with preferential extraction of the long-wavelength absorbing/emitting “humic-like” component (~30–50% extraction efficiency at λ <300 nm and ~50–80% at λ >400 nm) and virtually no extraction of the the UV absorbing/emitting bands. Response to NaBH4 reduction was also similar down the water column with preferential loss of absorption in the visible region, and enhanced, blue-shifted fluorescence emission. As in the EAO the ‘humic-like” component exhibited very similar, although not identical, optical and chemical properties to those observed for terrestrially-dominated estuarine and coastal environments, providing evidence that this component originates from a terrestrial source. Although this component dominated the absorption, marine contributions (i.e. UV bands) similar to those observed in the EAO were also observed. However, these components were found to absorb and emit primarily in the UV and were not efficiently extracted by the C18 columns, clearly showing that they are structurally distinct from the “humic-like” component.

13308. 题目: Major differences in dissolved organic matter characteristics and bacterial processing over an extensive brackish water gradient, the Baltic Sea
文章编号: N180625E7
期刊: Marine Chemistry
作者: Owen F. Rowe, Julie Dinasquet, Joanna Paczkowska, Daniela Figueroa, Lasse Riemann, Agneta Andersson
更新时间: 2018-06-25
摘要: Dissolved organic matter (DOM) in marine waters is a complex mixture of compounds and elements that contribute substantially to the global carbon cycle. The large reservoir of dissolved organic carbon (DOC) represents a vital resource for heterotrophic bacteria. Bacteria can utilise, produce, recycle and transform components of the DOM pool, and the physicochemical characteristics of this pool can directly influence bacterial activity; with consequences for nutrient cycling and primary productivity. In the present study we explored bacterial transformation of naturally occurring DOM across an extensive brackish water gradient in the Baltic Sea. Highest DOC utilisation (indicated by decreased DOC concentration) was recorded in the more saline southerly region where waters are characterised by more autochthonous DOM. These sites expressed the lowest bacterial growth efficiency (BGE), whereas in northerly regions, characterised by higher terrestrial and allochthonous DOM, the DOC utilisation was low and BGE was highest. Bacterial processing of the DOM pool in the south resulted in larger molecular weight compounds and compounds associated with secondary terrestrial humic matter being degraded, and a processed DOM pool that was more aromatic in nature and contributed more strongly to water colour; while the opposite was true in the north. Nutrient concentration and stoichiometry and DOM characteristics affected bacterial activity, including metabolic status (BGE), which influenced DOM transformations. Our study highlights dramatic differences in DOM characteristics and microbial carbon cycling in sub-basins of the Baltic Sea. These findings are critical for our understanding of carbon and nutrient biogeochemistry, particularly in light of climate change scenarios.

13309. 题目: Photoreactivities of two distinct dissolved organic matter pools in groundwater of a subarctic island
文章编号: N180625E6
期刊: Marine Chemistry
作者: Liming Qi, Huixiang Xie, Jean-Pierre Gagné, Gwena?lle Chaillou, Philippe Massicotte, Gui-Peng Yang
更新时间: 2018-06-25
摘要: Groundwater is a potentially significant source of dissolved organic matter (DOM) to coastal oceans where it is subject to photochemical transformation and thus possibly influences major marine biogeochemical processes. Furthermore, groundwater DOM usually receives little prior light exposure, making it suitable for probing the photoreactivity of source organic materials. In this study we collected two DOM pools in beach and inland groundwater of the les-de-la-Madeleine in the Gulf of St. Lawrence, characterized them with absorbance and fluorescence spectroscopy, and compared their photoreactivities. Beach groundwater (BGW) primarily comprised old, highly colored terrestrial DOM having high molecular weight (MW), strong humification, and low protein contents, whereas inland groundwater (IGW) largely contained fresh, less colored microbial-derived DOM with low molecular weight (MW), weaker humification, and higher protein contents. For both BGW and IGW, exposure to solar-simulated radiation led to increases in the E2/E3 quotient, biological index (BIX), and ammonium (NH4 +) and decreases in absorbance, specific absorption coefficient at 254 nm (SUVα254), fluorescence index (FI), humification index (HIX), MW, and dissolved organic carbon (DOC). The irradiation also reduced the intensities of humic-like fluorescence peaks and PARAFAC-modeled humic components. On a fractional-absorption-loss basis, the photochemically induced fractional changes in BGW were comparable to those in IGB for SUVα254 and E2/E3, considerably larger for MW, BIX, and DOC, and substantially smaller for FI and HIX. On an absorbed-photon basis, the efficiencies of absorbance photobleaching and DOC photomineralization for DOM in BGW were 8.3 times and 2.0 times those of the respective photoprocesses for DOM in IGW, while the efficiency of photoammonification for DOM in BGW was 41% of that for DOM in IGW. Results from this study, in combination with those reported previously for surface waters, lead to a tentative paradigm: terrigenous DOM is more prone to absorbance photobleaching but less prone to photoammonification than microbial-derived DOM while the two DOM pools are comparably reactive with respect to DOC photomineralization.

13310. 题目: Size-fractionated distributions of suspended particle concentration and major phase composition from the U.S. GEOTRACES Eastern Pacific Zonal Transect (GP16)
文章编号: N180625E5
期刊: Marine Chemistry
作者: Phoebe J. Lam, Jong-Mi Lee, Maija I. Heller, Sanjin Mehic, Yang Xiang, Nicholas R. Bates
更新时间: 2018-06-25
摘要: Marine particles play key roles in the cycling of most elements in the ocean. Here we present full water column sections of size-fractionated (1–51μm; >51μm) concentrations of suspended particulate matter (SPM) and major particle phase composition, including particulate organic matter (POM), calcium carbonate (CaCO3), opal, lithogenic particles, and iron and manganese (oxyhydr)oxides, as well as the Redfield (C:N:P) stoichiometry of particles, from the U.S. GEOTRACES GP16 Eastern Pacific Zonal Transect (EPZT). The GP16 cruise sampled the oxygen deficient waters of the productive eastern upwelling Peru margin westward to Tahiti through the East Pacific Rise (EPR) hydrothermal plume around 12°S in October–December 2013. In this region of relatively low mineral dust deposition, the sum of POM and CaCO3 concentrations accounted for >80% of small size fraction (SSF) SPM for most of the section. Some exceptions to this include the southern EPR hydrothermal plume, where iron oxyhydroxides accounted for almost 60% of SSF SPM, and the coastal upwelling zone, where opal and lithogenic particles accounted for ~50% of SSF SPM. We discuss possible mechanisms to explain a large sediment resuspension feature on the deep Peru continental slope. Large size fraction (LSF) particles generally had relatively higher contributions of opal and lower contributions of POM compared to SSF particles, reflecting an unusually high size partitioning of opal to the LSF. Distributions of CaCO3 and other phases were more strongly controlled by particle dynamics than by dissolution. Our particle phase data are consistent with a conceptual model where particle production, aggregation, and disaggregation processes dominate in the euphotic, 100–300m, and 300–500m depth zones, respectively. Our direct measurements of particle composition showed 1) euphotic zone C vs P relationships (SSF: 48±13; LSF: 65±14) that were significantly lower than canonical Redfield values (~106), but that were consistent with previously published large scale inverse and box model estimates of exported C:P for this region, and 2) PIC:POC ratios (LSF: 0.088) that were remarkably similar to estimated rain ratios from a biogeochemical-transport box model of alkalinity and nitrate in the low latitude Pacific.

13311. 题目: Bias in carbon concentration and δ13C measurements of organic matter due to cleaning treatments with organic solvents
文章编号: N180625E4
期刊: Chemical Geology
作者: ?lodie Muller, Christophe Thomazo, Eva E. Stüeken, Christian Hallmann, Arne Leider, Carine Chaduteau, Roger Buick, Franck Baton, Pascal Philippot, Magali Ader
更新时间: 2018-06-25
摘要: Interpreting the organic carbon content (TOC) and stable carbon isotopic composition (δ13C) of organic matter in the sedimentary rock record depends on our capability to accurately measure them, while excluding sources of contamination. This however becomes increasingly problematic as we analyze samples with ever-lower organic carbon content. Accordingly, organic solvents are sometimes used to remove contaminating traces of modern organic matter from ancient rock samples. However, especially for very low TOC samples, traces of solvents or their impurities remaining in the sample may contribute a significant organic contamination that can impact the bulk measurements of both TOC and δ13C values. This study, including three independent investigations performed in different laboratories, is the first detailed examination of the effect of cleaning treatments on the reliability of TOC and δ13C values in a range of natural rock samples and synthetic materials with low TOC content from below detection limit to 3330 ppm. We investigated the four most common organic solvents used to remove modern organic matter: dichloromethane (DCM), n-hexane, methanol and ethanol, and evaluated the effect of grain size and mineralogy. We find that (i) cleaning treatments with methanol, n-hexane and dichloromethane contaminate rock samples when used directly on sample powder, regardless of the grain size; (ii) this pollution buffers the natural variability and homogenizes the δ13C values of samples around the isotopic composition of the solvent, i.e. between 27 and 29‰; (iii) the extent of contamination depends on the solvent used, DCM being the most contaminating (up to 6000 ppm) and ethanol the only solvent that does not seem to contaminate rock samples above our detection limit; (iv) sample mineralogy also exerts an influence on the extent of contamination, clay minerals being more prone to adsorb contaminants. We conclude that the response of carbon concentrations and the stable carbon isotopic composition of organic matter in geological samples to cleaning treatments is neither negligible nor systematic when investigating samples with low carbon content.

13312. 题目: Degassing of organic carbon during regional metamorphism of pelites, Wepawaug Schist, Connecticut, USA
文章编号: N180625E3
期刊: Chemical Geology
作者: Shuang Zhang, Jay J. Ague, Alberto Vitale Brovarone
更新时间: 2018-06-25
摘要: A comprehensive understanding of the degassing systematics of organic carbon (OC) during regional metamorphism is necessary to evaluate the role that metamorphism plays in the global carbon cycle. In this study, weight percentages and δ13C values of OC were measured in 70 samples of metapelites from the Wepawaug Schist, Connecticut, where classic Barrovian metamorphism occurred and graphitic OC is widespread. Relative to low-grade chlorite + biotite zone rocks, our mass balance analysis shows that OC in the metapelites underwent progressive loss from 14% ( 0.06 g OC per 100 g rock) in the garnet zone, through 21% ( 0.09 g/100 g) in the staurolite zone, to 26% ( 0.11 g/100 g) in the kyanite zone. The average δ13C values in different metamorphic zones (ranging from 14.74‰ to 16.24‰) are all much higher than normal organic material in marine sediments, and increase slightly from the chlorite + biotite zone to the garnet zone and decrease slightly at higher metamorphic grades. Organic carbon degassing in the form of CH4 during the late stage of diagenesis or in the earliest stages of metamorphism could produce this significant 13C enrichment. Under the assumption that the 13C enrichment is caused by graphite degassing during the lowest-grade metamorphism (chlorite zone or lower), the degassing profile of OC during the regional metamorphism is reconstructed by combining the δ13C and OC mass change data. The computed results indicate that graphitic OC in the Wepawaug Schist probably underwent considerable loss at lowest-grade metamorphic conditions, ranging from ~ 40% to ~ 90% (or from 0.23 g OC per 100 g rock to 2.8 g OC per 100 g rock), and remained relatively inert at higher grades. Based on the mass balance analysis, δ13C systematics, and exploratory modeling results, this study argues that the lowest-grade or pre-metamorphic stages would be the more efficient OC liberators, and that the degassing potential of OC in the major stages of Barrovian metamorphism appears to be much more restricted. Additional independent studies are required to decipher the early degassing of OC after the deposition of organic matter, which could in turn help better constrain the degassing of OC during regional metamorphism.

13313. 题目: Dwindling vanadium in seawater during the early Cambrian, South China
文章编号: N180625E2
期刊: Chemical Geology
作者: Tao Han, Haifeng Fan, Hanjie Wen
更新时间: 2018-06-25
摘要: Elemental vanadium (V), an essentially redox-sensitive metal in seawater, has had a significant impact on the understanding of the evolution of the atmosphere-ocean system throughout the history of the Earth. In fact, the geochemical cycle of V in early Cambrian seawater may have had an influence on the Chengjiang Biota in South China; however, it has not yet been well established. Given the authigenic vanadium accumulation is sensitive to the redox conditions of seawater, here, to constrain the geochemical cycle of V in seawater during the early Cambrian, the Mo, U and total organic carbon (TOC) distributions with high-resolution samples from both the outer shelf and slope facies (e.g., the Duoding and Longbizui sections), are applied to evaluate the redox conditions of ambient seawater. The Mo-U relationships indicate that the redox conditions of the mid-depth seawater evolved in a systematic way in South China, transitioning from an Fe-Mn reduction zone to anoxic/intermittently euxinic states and then to oxic conditions during the early Cambrian. As a consequence, the authigenic V enrichment, constrained by the marine redox conditions, was mainly controlled by the Fe-Mn particulate shuttle and the reduction and adsorption of organic matter in anoxic/euxinic conditions. However, the decoupling among V, Mo, U and TOC under anoxic/euxinic conditions suggests a dwindling vanadium concentration in the early Cambrian seawater of South China. The scavenging efficiency of V from seawater is much higher than those of Mo and U under anoxic/euxinic conditions. Ultimately, these trace elements (e.g., Mo, U, and especially V) in seawater could effectively be regulated and adjusted to a reasonable level under the widespread anoxic/euxinic conditions. The drawdown of trace elements in seawater might provide an early-stage preparation of the marine environment for the subsequent Chengjiang Biota.

13314. 题目: Fate of particulate copper and zinc isotopes at the Solim?es-Negro river confluence, Amazon Basin, Brazil
文章编号: N180625E1
期刊: Chemical Geology
作者: Damien Guinoiseau, Julien Bouchez, Alexandre Gélabert, Pascale Louvat, Patricia Moreira-Turcq, Naziano Filizola, Marc F. Benedetti
更新时间: 2018-06-25
摘要: The behaviour and fate of copper (Cu) and zinc (Zn) at river confluences is poorly understood, although chemical and physical processes during mixing of compositionally different tributaries might condition metal availability and fluxes to the ocean. To identify and quantify the effect of such processes in river mixing zones, particulate Cu and Zn isotope signatures (δ65CuSPM and δ66ZnSPM) were measured along cross sections and vertical profiles at the largest river confluence in the world, the “Encontro das Aguas” mixing zone of the Amazon River, where the organic-rich Negro River meets the sediment-rich Solim es River. The Negro River suspended sediments, with highly variable Cu and Zn concentrations as well as δ65CuSPM and δ66ZnSPM, are mostly influenced by organic matter and by the lateritic cover of the watershed. The Solim es River suspended sediments, more homogeneous in Cu and Zn concentration and isotope composition across the river section, reflect the signature of weathered silicate-rich sediments derived from the Andes. The Solim es River supplies the majority of the suspended Cu and Zn to the Amazon River, and despite important flux losses across the confluence ( 35% for Cu and 27% for Zn), δ65CuSPM and δ66ZnSPM show a conservative behaviour during the mixing. In the dissolved load, Cu concentrations and δ65Cudiss, mostly supplied by the Solim es River, behave conservatively whereas Zn, derived mainly from the Negro River, suffers an important loss ( 58%) that can be attributed to Zn adsorption onto the suspended sediments from the Solim es River. This transfer does not induce a significant δ66ZnSPM shift in the Amazon River suspended sediments. Therefore, Cu and Zn isotope ratios in the suspended sediments behave conservatively through this confluence, which mixes two very chemically-contrasted rivers. Our findings thus suggest that the riverine isotopic information on the sources of particulate Cu and Zn is preserved during tributary mixing.

13315. 题目: Links between seawater paleoredox and the formation of sediment-hosted massive sulphide (SHMS) deposits — Fe speciation and Mo isotope constraints from Late Devonian mudstones
文章编号: N180625E0
期刊: Chemical Geology
作者: Joseph M. Magnall, Sarah A. Gleeson, Simon W. Poulton, Gwyneth W. Gordon, Suzanne Paradis
更新时间: 2018-06-25
摘要: Many models of sediment hosted massive sulphide (SHMS) deposit formation invoke basin restriction events that resulted in long-term stagnation and anoxia, in which sulphidic (euxinic) conditions ultimately prevailed. Euxinic conditions are then thought to provide a chemical trap for hydrothermally exhaled base metals. Here, we present Fe speciation and Mo isotope data for organic-rich mudstones from two drill-holes intersecting Upper Devonian strata, deposited along the passive margin of ancestral North America. One drill-hole intersects a 35 m thick sequence of SHMS mineralisation, while the other intersects correlative, un-mineralised strata. All samples have high FeHR/FeT values (>0.38), indicating water-column anoxia. For the majority of samples in the un-mineralised drill-hole, the levels of pyritisation fall below the threshold typically used to define euxinic conditions (FePY/FeHR ≤ 0.70). In contrast, higher levels of pyritisation in the mineralised drill-hole (median FePY/FeHR = 0.86) likely developed via diagenetic pyrite enrichment. Whereas Pb and Zn are negatively correlated with Mo, Mo-U co-variation is consistent with Fe (oxyhydr)oxide particulate shuttling in the water-column. In addition, a weak correlation between TOC/P and Mo provides further evidence that Mo was sourced via authigenic, rather than hydrothermal, processes. The δ98Mo values (+0.66 to +1.02‰) are uniform between both drill-holes, and substantially lower than constraints for Late Devonian seawater (+1.5 to +2.0‰), consistent with Mo adsorption to Fe (oxyhydr)oxides. Collectively, the data provide evidence that local seawater was dominantly ferruginous (anoxic, non-sulphidic) at Macmillan Pass. Regional variability in the extent of ferruginous (low TOC/P) and euxinic (high TOC/P) conditions likely contributed to a balance between P regeneration and P enrichment that maintained nutrient availability and productivity in the Selwyn Basin during the Late Devonian. We argue that high primary productivity and enhanced organic carbon burial are key variables for promoting sulphate reduction in the sub-surface. Moreover, how such conditions are maintained over long periods of basin evolution is more important for producing effective metal traps in SHMS systems, rather than a specific, localised redox condition of seawater (i.e. euxinia).

13316. 题目: A combination of ammonia stripping and low temperature thermal pre-treatment improves anaerobic post-digestion of the supernatant from organic fraction of municipal solid waste treatment
文章编号: N180625D9
期刊: Waste Management
作者: Chiara Pedizzi, Juan M. Lema, Marta Carballa
更新时间: 2018-06-25
摘要: Municipal Solid Waste is mostly composed of organic material which is often treated in anaerobic reactors in waste treatment plants. In most cases, the obtained digestate undergoes a solid/liquid separation step, producing a liquid fraction (known as anaerobic supernatant) rich in ammonium nitrogen that has to be further treated in order to meet discharge standards. The objective of the present work was to evaluate the feasibility of anaerobic post-digestion (37 °C) of a supernatant rich in carbon and nitrogen from a municipal waste treatment plant. In order to increase the efficiency of the process, a combined pre-treatment consisting of a low-temperature thermal process (75 °C) and ammonia stripping (1.3 Lair Lsupernatant 1 min 1) was applied. The effects of pre-treatment contact time (4 and 8 h) and the hydraulic retention time (HRT) in the anaerobic reactor (20–40 d) were studied. Supernatant pre-treatment with 8-h contact time caused 13% organic matter solubilisation, thus improving methanisation by 18% when the HRT was 40 d. At the same time, ammonia stripping allowed to maintain ammonia concentration in the digester below inhibitory values (less than 100 mg N-NH3 L 1) enabling therefore high methanogenic activity (>0.23 g COD g 1 VS d 1). The final effluent characteristics (low total ammonia nitrogen and aerobically biodegradable organic matter levels) would permit implementing subsequent less energy intensive and more environmental-friendly technologies (such as partial nitritation/anammox) to comply with discharge limits.

13317. 题目: Characterization of dissolved organic matter from biogas residue composting using spectroscopic techniques
文章编号: N180625D8
期刊: Waste Management
作者: Xujing Guo, Chongwei Li, Qili Zhu, Tao Huang, Yu Cai, Nanxi Li, Jianying Liu, Xiandong Tan
更新时间: 2018-06-25
摘要: Dissolved organic matter (DOM) extracted from composting of biogas residue was characterized using spectroscopic techniques. Spectral parameters, specific UV absorbance at 254 (SUVA254), ratios of spectral slopes (SR), and humification index (HIX) were used to assess the structural characteristics of the DOM. During composting, the UV absorbance at 254 increased as the relatively resistant aromatic fraction was released and the DOM molecular weight increased with the degree of humification. Fluorescence excitation-emission matrix (EEM) spectra with regional integration analysis (FRI) and accumulative fluorescence emission (AFE) combined with second derivative spectroscopy were used to assess the evolution of the DOM and evaluate the production of resistant humic-like substances during composting. Second derivative spectroscopy showed that microbial-derived humic-like substance A2 was easily degraded during composting. Two-dimensional correlation spectroscopy (2D-COS) combined with Fourier-transform infrared (FTIR) spectroscopy determined the preferential change sequence of the functional groups was 2000–2300 (CC or CN) → 1288 cm 1 (amide III) at x1 and 2935 (aliphatic groups) → 1420 (carboxylic groups) → 3100–3400 (hydroxyl groups) → 1660 cm 1 (aromatic CC) at x2, suggesting that functional groups of CC or CN, and amide III can be degraded preferentially, and aromatic CC groups were difficultly degraded. The present study showed spectroscopic techniques are valuable tools for assessing composting of biogas residues.

13318. 题目: Efficiency of landfill leachate treatment in a MBR/UF system combined with NF, with a special focus on phthalates and bisphenol A removal
文章编号: N180625D7
期刊: Waste Management
作者: Sylwia Fudala-Ksiazek, Mattia Pierpaoli, Aneta Luczkiewicz
更新时间: 2018-06-25
摘要: In this study, a pilot-scale membrane bioreactor (MBR) was operated at a municipal solid waste plant (MSWP) to treat a mixture of landfill leachates (LLs) obtained from modern (MP-LLs) and previous (PP-LLs) waste cells. The MBR unit combined anoxic and aerobic zones with external ultra- and nanofiltration (MBR/UF and MBR/UF/NF, respectively). In addition to the removal of macropollutants, special attention was given to phthalates (PAEs) and bisphenol A (BPA). According to the obtained results, the MBR/UF system with acclimated biomass was effective for treating LLs, and the obtained effluent was generally similar in quality to raw municipal wastewater. The MBR biomass showed high potential for BPA and PAEs biodegradation/biotransformation as confirmed by a metagenomic approach. Only a high chloride concentration (1960 mg Cl /L), which was twice the value acceptable by Polish regulations for industrial wastewater entering the municipal wastewater system, justifies the additional usage of the NF unit. Notably, a decreasing amount of biodegradable organic matter in MBR influent is expected with time because of changes in the biochemistry of modern waste cells; therefore, an external carbon source would probably be needed to support denitrification. However, the cooccurrence of an aerobic and anaerobic ammonia-oxidizing community with denitrifying bacteria provides the opportunity for advanced removal of nitrogen and organic carbon.

13319. 题目: Full scale study of Class A biosolids produced by thermal hydrolysis pretreatment and anaerobic digestion
文章编号: N180625D6
期刊: Waste Management
作者: Xuanzhao Wang, Natasha Andrade, Jessica Shekarchi, Sarah J. Fischer, Alba Torrents, Mark Ramirez
更新时间: 2018-06-25
摘要: Biosolids are the solid by-product of wastewater treatment and contain high-organic matter and nutrient content, which can be utilized in food production and gardening. In 2014, this study’s target nutrient recovery facility (NRF) in the Mid-Atlantic region of the U.S. adopted thermal hydrolysis pretreatment (THP) and anaerobic digestion (AD) to upgrade biosolids from Class B (lime-stabilized) to Class A. The pathogen, nutrients, and metals contents were compared with that of Class B biosolids from the same facility throughout a one-year period. Following optimization and equilibrium, stable biosolids were produced that satisfied all Environmental Protection Agency (EPA) Class A biosolids standards. Class A biosolids produced had fecal coliform density consistently below the 1000 MPN/g d.w. limit set by the EPA, at 35.85 ± 81.10 MPN/g d.w. (n = 301). Metal concentrations were greater in Class A than Class B biosolids as a result of biosolids mass reduction, but these levels were substantially lower than regulatory limits. Metal concentrations were (in mg/kg d.w.): As = 6.43 ± 0.400 (n = 141), Cd = 3.39 ± 0.117 (n = 147), Cr = 88.4 ± 2.00 (n = 148), Cu = 401 ± 9.81 (n = 148), Pb = 68.1 ± 2.19 (n = 148), Hg = 1.21 ± 0.116 (n = 148), Mo = 14.9 ± 0.321 (n = 148), Ni = 23.8 ± 0.911 (n = 146), Se = 10.0 ± 0.573 (n = 140), Zn = 778 ± 14.9 (n = 148), K = 850 ± 21.7 (n = 134). In addition, Class A biosolids were rich in total nitrogen (N) and higher in total phosphorus (TP), but low in potassium (K) content. Concentration of K was 850 ± 21.7 mg/kg d.w. (n = 134), TKN was 52,000 ± 13,300 mg/kg d.w. (n = 43), TP was 34,500 ± 6130 mg/kg d.w. (n = 42), and ammonia-N was 7860 ± 1350 mg/kg d.w. (n = 43).

13320. 题目: Particle-scale visualization of the evolution of methanogens and methanotrophs and its correlation with CH4 emissions during manure aerobic composting
文章编号: N180625D5
期刊: Waste Management
作者: Jinyi Ge, Guangqun Huang, Junbao Li, Lujia Han
更新时间: 2018-06-25
摘要: Methane (CH4) emissions are a major environmental concern in composting facilities. Therefore, this study initially visualized the dynamic distribution and quantity of methanogens and methanotrophs in composting particles during manure aerobic composting using fluorescence in situ hybridization–confocal laser scanning microscopy (FISH–CLSM) and quantified their correlation with CH4 emissions. The visualization results showed that methanogens existed inside the particles, while methanotrophs clustered in the outer layer; a facultative anaerobic zone existed in between. The quantification results of integral optical density of methanogens and methanotrophs per unit particle area (U gen and U oxi, respectively) indicated that, in the cooling phase, CH4 generation and oxidation could still be high and could strike a balance if the initial organic matter content of composting materials is high, while both could be extremely low if the content is low. A strong linearity between U gen obtained by FISH–CLSM and methyl-coenzyme M reductase copy number obtained by quantitative polymerase chain reaction analysis (R 2 = 0.88) was observed, which justified the effectiveness of the FISH–CLSM method and demonstrated that macro-scale CH4 emissions were essentially an accumulation of particle-scale CH4 emissions. CH4 emissions were equal to 3.3297 × 107 U gen – 3.1814 × 106 U oxi – 3902.9900 (R 2 = 0.98). Overall, the results showed that methanogens exerted more influence on CH4 emissions than methanotrophs. Combining these results with CH4-generation and -oxidation kinetics may help illustrate CH4-emission mechanisms, improve particle-scale CH4-emission models, and thereby provide theoretical guidance for operation optimization and emission reduction in composting processes.

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