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22981. 题目: Iron reductive dissolution in vadose zone soils: Implication for groundwater pollution in landfill impacted sites
文章编号: N18062602
期刊: Applied Geochemistry
作者: Akua B. Oppong-Anane, Katherine Y. Deliz Qui?ones, Willie Harris, Timothy Townsend, Jean-Claude J. Bonzongo
更新时间: 2018-06-26
摘要: Iron (Fe) contamination of groundwater has become a problem of concern at a number of landfill impacted locations, and long-term monitoring studies suggest that the reductive dissolution of iron (hydr)oxide minerals present in soils and aquifer sediments could be one the sources of dissolved Fe measured in impacted aquifers. In this study, vadose zone soil samples were collected along a gradient emphasizing differences in both soil water saturation levels and degrees of crystallization of Fe-minerals. Collected soil samples were analyzed for pH, organic matter content, particle size distribution, and Fe speciation into amorphous and crystalline fractions. Batch experiments were conducted under anaerobic conditions using soil slurries with (treatments) or without (controls) landfill leachate addition to the liquid phase. Under the experimental conditions used in this study, tested soils released Fe primarily via reductive dissolution pathways, with rates ranging from 0.3 to 12 mg Fe/kg.day. However, no clear trend was evident between the amount of Fe released and the crystallinity degrees of the iron minerals present in the tested soils. The addition of organic carbon sources to prepared vadose soils slurries fueled the microbial driven Fe-reductive dissolution, suggesting that organic-rich landfill leachate would play a significant role in the dissolution of iron (hydr)oxide minerals, and potentially in the mobilization of toxic metals co-precipitated with or adsorbed onto iron (hydr)oxide minerals.

22982. 题目: Influence of colloids on metal concentrations and radiogenic strontium isotopes in groundwater and oil and gas-produced waters
文章编号: N18062601
期刊: Applied Geochemistry
作者: Thai T. Phan, J. Alexandra Hakala, Daniel J. Bain
更新时间: 2018-06-26
摘要: Concentrations and isotopic compositions of Li and Sr can be used to identify water-rock interactions and fluid mixing in petroleum reservoirs, such as mixing between hydraulic fracturing fluid and in-situ formation water in hydraulically fractured shales. However, the physical changes during mixing in the subsurface environment and during collection of produced water are not clear. We hypothesize that the colloidal particles potentially affect measured constituents in produced waters and degrade the utility of Li and Sr isotopes as geochemical tracers of fluid sources and water-rock interactions. Therefore, this study investigated the influence of colloids on the metal concentrations and isotopes (δ7Li and 87Sr/86Sr) by analyzing water that was filtered through successively smaller membranes (0.45 μm, 0.2 μm, and 3 kDa). We found that the differences in the concentrations of major and most minor elements (B, Ca, Ga, K, Li, Mg, Na, Ga, Rb, and Sr) in the <0.45 μm, the <0.2 μm, and the <3 kDa fractions of groundwater and oil produced water are not statistically different (p > 0.05; Student's t-test). Likewise, similar results were observed for the <0.45 μm, the <0.2 μm-centrifuged, and the <3 kDa fractions of gas produced water. In the <0.45 μm fraction of groundwater, U is up to 8% greater than U in the 3 kDa fraction, possibly due to complexation of U with natural organic matter. The formation of Fe oxyhydroxides during sample collection was observed in all three types of waters, however does not significantly affect the measured 87Sr/86Sr between three fractions of the study waters. On the other hand, Al, Si, and Ti are enriched in the <0.45 μm fraction relative to the <3 kDa fraction of gas produced water, likely due to aluminosilicate minerals (e.g., clays and quartz). However, interactions of Sr and Li with these minerals do not result in statistically significant differences (p > 0.05) in 87Sr/86Sr among three fractions of groundwater and both oil and gas produced waters. Similarly, no difference in δ7Li in <0.45 μm and <0.2 μm-centrifuged fractions of gas produced water was observed. Ultimately, overestimated concentration data of Al, Si, and Ti in water filtered through a 0.45 μm membrane due to the presence of colloidal clays can create misinterpretations of chemical water-rock interactions in hydraulically fractured shale in the subsurface.

22983. 题目: Coagulation of low temperature and low turbidity water: Adjusting basicity of polyaluminum chloride (PAC) and using chitosan as coagulant aid
文章编号: N180625G3
期刊: Separation and Purification Technology
作者: Zhen Zhang, Ran Jing, Shuran He, Jin Qian, Kun Zhang, Guilin Ma, Xing Chang, Mingkuan Zhang, Yongtao Li
更新时间: 2018-06-25
摘要: This study evaluated the feasibility of integrating high-basicity polyaluminum chloride (PAC) and high-viscosity chitosan for the coagulation of low-temperature and low-turbidity water. The effects of PAC basicity on coagulation performance and residual Al control were also investigated. It was found that higher-basicity PAC with a larger proportion of Alc (colloidal Al species in PAC) and smaller proportion of Ala (monomeric Al species in PAC) was beneficial for removing turbidity and natural organic matter (NOM), as well as controlling the residual Al content. Further, the integration of PAC with a high basicity (90.3%) and chitosan with a high viscosity (500 mPa·s) realized the efficient removal of turbidity and NOM, with removal efficiencies of approximately 87%, 63%, and 82% for turbidity, dissolved organic matter (DOC) and UV254, respectively. It was speculated that larger and more settleable flocs tended to form via the synergistic effect of charge neutralization by Alb (polymeric Al species in PAC) and interparticle bridging by both the Alc species and chitosan, consequently leading to excellent coagulation performance. This study may provide a useful option to drinking water treatment operators for dealing with low-temperature and low-turbidity water in practice.

22984. 题目: Study of solar photocatalytic degradation of Acesulfame K to limit the outpouring of artificial sweeteners
文章编号: N180625G2
期刊: Separation and Purification Technology
作者: Malini Ghosh, Pankaj Chowdhury, Ajay K. Ray
更新时间: 2018-06-25
摘要: In this study, the photocatalytic degradation of an artificial sweetener, Acesulfame K (ACK), has been investigated with TiO2 photocatalyst using a solar simulator. Adsorption of ACK on TiO2 surface follows Freundlich adsorption isotherm in the pH range of 6–8 and shows an adsorption coefficient of 0.002 L/mg. Parametric studies for solar photocatalytic degradation are performed varying initial concentrations of ACK, photocatalyst dosage, and solar light intensity. Photocatalytic degradation rate of ACK gradually decreases with increasing initial concentration of ACK, and the rate follows pseudo first-order kinetics. The degradation rate of ACK gradually increases as the TiO2 dosage is increased and reaches maximum at 0.8–1.0 g/L. The rate constant for ACK degradation has been found to be directly proportional to light intensity, obeying a power law model. Complete degradation of ACK for 10–20 mg/L initial concentration is observed within the first 30 min of solar light irradiation of 100 mW/cm2 at pH 6. Complete mineralization of ACK can be achieved in 6 h with dissolved organic carbon (DOC) less than 1 mg/L. Complete mineralization of ACK and its by-products is successfully achieved with an apparent quantum yield of 0.02% at 1 sun thus making the process sustainable. This study manifests the efficacy of the solar photocatalytic process on degrading emerging pollutants like ACK where the use of artificial UV lamp has successfully been substituted by solar light, the most abundantly found sustainable source of energy in nature. Moreover, the process followed in this study is devoid of the use of any hazardous chemicals.

22985. 题目: Characterization of bacterial community and iron corrosion in drinking water distribution systems with O3-biological activated carbon treatment
文章编号: N180625G1
期刊: Journal of Environmental Sciences
作者: Xueci Xing, Haibo Wang, Chun Hu, Lizhong Liu
更新时间: 2018-06-25
摘要: Bacterial community structure and iron corrosion were investigated for simulated drinking water distribution systems (DWDSs) composed of annular reactors incorporating three different treatments: ozone, biologically activated carbon and chlorination (O3-BAC-Cl2); ozone and chlorination (O3-Cl2); or chlorination alone (Cl2). The lowest corrosion rate and iron release, along with more Fe3O4 formation, occurred in DWDSs with O3-BAC-Cl2 compared to those without a BAC filter. It was verified that O3-BAC influenced the bacterial community greatly to promote the relative advantage of nitrate-reducing bacteria (NRB) in DWDSs. Moreover, the advantaged NRB induced active Fe(III) reduction coupled to Fe(II) oxidation, enhancing Fe3O4 formation and inhibiting corrosion. In addition, O3-BAC pretreatment could reduce high-molecular-weight fractions of dissolved organic carbon effectively to promote iron particle aggregation and inhibit further iron release. Our findings indicated that the O3-BAC treatment, besides removing organic pollutants in water, was also a good approach for controlling cast iron corrosion and iron release in DWDSs.

22986. 题目: Effects of turbulence on carbon emission in shallow lakes
文章编号: N180625G0
期刊: Journal of Environmental Sciences
作者: Lin Zhu, Boqiang Qin, Jian Zhou, Bryce Van Dam, Wenqing Shi
更新时间: 2018-06-25
摘要: Turbulent mixing is enhanced in shallow lakes. As a result, exchanges across the air–water and sediment–water interfaces are increased, causing these systems to be large sources of greenhouse gases. This study investigated the effects of turbulence on carbon dioxide (CO2) and methane (CH4) emissions in shallow lakes using simulated mesocosm experiments. Results demonstrated that turbulence increased CO2 emissions, while simultaneously decreasing CH4 emissions by altering microbial processes. Under turbulent conditions, a greater fraction of organic carbon was recycled as CO2 instead of CH4, potentially reducing the net global warming effect because of the lower global warming potential of CO2 relative to CH4. The CH4/CO2 flux ratio was approximately 0.006 under turbulent conditions, but reached 0.078 in the control. The real-time quantitative PCR analysis indicated that methanogen abundance decreased and methanotroph abundance increased under turbulent conditions, inhibiting CH4 production and favoring the oxidation of CH4 to CO2. These findings suggest that turbulence may play an important role in the global carbon cycle by limiting CH4 emissions, thereby reducing the net global warming effect of shallow lakes.

22987. 题目: Formation process and mechanism of humic acid-kaolin complex determined by carbamazepine sorption experiments and various characterization methods
文章编号: N180625F9
期刊: Journal of Environmental Sciences
作者: Fei Wang, Jiangtao He, Baonan He, Xiaojing Zhu, Xiaocui Qiao, Liuyue Peng
更新时间: 2018-06-25
摘要: To explore the formation process and mechanism of organic matter and organic-mineral complex under humification and mineralization conditions, a series of samples including humic acid, kaolin, and humic acid-kaolin complex were prepared using a subcritical water treatment method (SWT) under specific temperature, pressure and reaction time conditions. HA was used as a surrogate for natural organic matter because it has a similar abundant pore structure, variety of carbon types, and chemical components. These samples were used in carbamazepine (CBZ) sorption experiments and characterized by a variety of techniques. The polymerization of humic acid under the conditions of increased temperature and pressure resulted in an increase in specific surface area and molecular quantity. In addition, the degree of aromaticity rose from 59.52% to 70.90%. These changes were consistent with the transformation from ‘soft carbon’ to ‘hard carbon’ that occurs in nature. The results of sorption experiments confirmed the interaction between humic acid and kaolin from the difference between the predicted and actual Q e values. The conceptual model of humic acid-kaolin complex could be deduced and described as follows. Firstly, the aromatic components of humic acid preferentially combine with kaolin through the intercalation effect, which protects them from the treatment effects. Next, the free carboxyl groups and small aliphatic components of humic acid interact on the surface of kaolin, and these soft species transform into dense carbon through cyclization and polymerization. As a result, humic acid-kaolin complex with a mineral core and dense outer carbonaceous patches were formed.

22988. 题目: Insight into removal of dissolved organic matter in post pharmaceutical wastewater by coagulation-UV/H2O2
文章编号: N180625F8
期刊: Journal of Environmental Sciences
作者: Feng Qian, Mengchang He, Jieyun Wu, Huibing Yu, Liang Duan
更新时间: 2018-06-25
摘要: The removal of four dissolved organic matter (DOM) fractions, non-acid hydrophobics, hydrophobic acids, hydrophilics and transphilics, was achieved by coagulation-UV/H2O2 oxidation in post-pharmaceutical wastewater (PhWW). Coagulation with Polyferric chloride (PFC), Polymeric ferric sulfate (PFS) and Polymeric aluminum ferric chloride (PAFC) was studied separately to evaluate the effects of the initial pH and coagulant dosage. The coagulation-UV/H2O2 oxidation method resulted in much higher reduction rates for dissolved organic carbon (DOC) (by 75%) and UV254 (by 92%) than coagulation or UV/H2O2 oxidation alone. The proportion of non-acid hydrophobics, hydrophobic acids, transphilics and hydrophilics removed by coagulation was 54%, 49%, 27% and 12 %, while the combined treatment removed 92%, 87%, 70% and 39%, respectively. Parallel factor analysis (PARAFAC) of fluorescence measurements revealed that the humic-like fluorescent component C4 showed the highest removal (by 44%) during the coagulation stage. After coagulation-UV/H2O2 treatment, the humic-like fluorescent component C3 had the highest removal (by 72%), whereas xenobiotic organic fluorescent components C1 and C4 remained recalcitrant to decomposition. Significant correlations (R 2 > 0.8) between C1 and the hydrophobic acids and non-acid hydrophobics suggested the possibility of using fluorescence spectroscopy as an effective tool to assess variations in DOM fraction treatment efficacy in coagulation-UV/H2O2 systems. After the combined treatment, toxic inhibition of cellular activity by post PhWW decreased from 88% to 47% and biodegradability increased from 0.1 to 0.52.

22989. 题目: Role of the floodplain lakes in the methylmercury distribution and exchanges with the Amazon River, Brazil
文章编号: N180625F7
期刊: Journal of Environmental Sciences
作者: Poliana Dutra Maia, Laurence Maurice, Emmanuel Tessier, David Amouroux, Daniel Cossa, Patricia Moreira-Turcq, Henri Etcheber
更新时间: 2018-06-25
摘要: Seasonal variability of dissolved and particulate methylmercury (F-MeHg, P-MeHg) concentrations was studied in the waters of the Amazon River and its associated Curuai floodplain during hydrological year 2005–2006, to understand the MeHg exchanges between these aquatic systems. In the oxic white water lakes, with neutral pH, high F-MeHg and P-MeHg concentrations were measured during the rising water stage (0.70±0.37pmol/L, n =26) and flood peak (14.19±9.32pmol/g, n =7) respectively, when the Amazon River water discharge into the lakes was at its maximum. The lowest mean values were reported during the dry season (0.18±0.07pmol/L F-MeHg, n =10 and 1.35±1.24pmol/g P-MeHg, n =8), when water and suspended sediments were outflowing from the lakes into the River. In these lakes, the MeHg concentrations were associated to the aluminium and organic carbon/nitrogen changes. In the black water lakes, with acidic pH and reducing conditions, elevated MeHg concentrations were recorded (0.58±0.32pmol/L F-MeHg, n =16 and 19.82±15.13pmol/g P-MeHg, n =6), and correlated with the organic carbon and manganese concentrations. Elevated values of MeHg partition coefficient (4.87< K d <5.08log (L/kg) indicate that MeHg is mainly transported associated with the particulate phase. The P-MeHg enrichment detected in all lakes suggests autochthonous MeHg inputs from the sediments into the water column. The MeHg mass balance showed that the Curuai floodplain is not the source of P-MeHg for the Amazon River.

22990. 题目: 234Th as a tracer of particulate export and remineralization in the southeastern tropical Pacific
文章编号: N180625F6
期刊: Marine Chemistry
作者: Erin E. Black, Ken O. Buesseler, Steven M. Pike, Phoebe J. Lam
更新时间: 2018-06-25
摘要: Oxygen minimum zones (OMZs) are thought to be regions of decreased carbon attenuation in the upper ocean with a biological pump that could deliver a greater percentage of exported carbon to the mesopelagic relative to surrounding waters. However, much is still unknown about carbon cycling through these zones and the areas of extreme oxygen minima (nM O2) or oxygen deficient zones (ODZs) within the OMZs. Paired sampling for 234Th (t ~24.1days) and particulate organic carbon (POC) was performed along a zonal transect between 77 and 152°W during the U.S. GEOTRACES Southeastern Tropical Pacific campaign in 2013 in order to constrain the magnitude of carbon export and remineralization through the Peruvian OMZ. POC export varied by an order of magnitude from the coast to 152°W, reflecting a decrease in POC:234Th ratios (>51μm) with distance offshore and the influence of upwelling at the coast. Modeling indicated that 234Th fluxes could be underestimated at coastal stations by up to 4-fold without adjustment for the impact of upwelling, which in turn would produce much lower carbon export estimates. Low carbon Export:NPP ratios (<0.15) at the base of the euphotic zone (Ez) in the gyre support previous findings of inefficient surface export via the biological pump in the southeastern tropical Pacific. A broad remineralization feature beginning at the Ez was observed across >7500km that resulted in, on average, 3% of the POC exported from the euphotic zone reaching 100m below the Ez. Although the highest percentages (>10%) of total exported POC at 100m below the Ez were observed in the coastal ODZ region, the observed remineralization was also most pronounced these stations. While an average of 75% of the carbon export from the euphotic zone remained at Ez+100m in the gyre, a range of 10 to 50% was observed at ODZ stations, reflecting increased attenuation. Local subsurface minima in light transmission and maxima in fluorescence were observed in the regions of greatest remineralization at the upper ODZ boundary, suggesting that complex bacterial community dynamics play a role in increased attenuation through these zones. With ODZs and OMZs predicted to grow worldwide with climate change, these areas require further large-scale and seasonal studies to assess the permanency of these attenuation features and the impact of high Gyre and lower ODZ transfer of POC on the overall efficiency of carbon export in the Pacific.

22991. 题目: A potential formation route for CHOS compounds in dissolved organic matter
文章编号: N180625F5
期刊: Marine Chemistry
作者: Jose J. Melendez-Perez, Mónica J. Martínez-Mejía, Roberto L. Barcellos, Ant?nio F.H. Fetter-Filho, Marcos Nogueira Eberlin
更新时间: 2018-06-25
摘要: Sulfur polyoxygenated organic compounds (CHOS compounds) had been detected in dissolved organic matter (DOM) from several aquatic systems around the world but the knowledge of its origin and geochemical behavior is still scarce. Previous studies have reported correlations between the content of CHOS compounds in DOM and the sulfide concentration in aquatic systems. We therefore performed a set of laboratorial experiments aiming to better understand the role of DOM in the sulfur cycle and we found that CHOS compounds can be formed in aquatic systems by the addition of sulfide/bisulfide ions to lignin-like CHO compounds. We also show that sediments act as heterogeneous catalysts that facilitate the formation of CHOS compounds.

22992. 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.

22993. 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.

22994. 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.

22995. 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.

22996. 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.

22997. 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.

22998. 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.

22999. 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.

23000. 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.

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