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14061. 题目: Changes in soil microbial biomass C, ATP and microbial ATP concentrations due to increasing soil Cd levels in Chinese paddy soils growing rice ( Oryza sativa )
文章编号: N18121705
期刊: Plant and Soil
作者: Gaoyang Qiu, Min Zhu, Jun Meng, Yu Luo, Hongjie Di, Jianming Xu, Philip C. Brookes
更新时间: 2018-12-17
摘要: Aims: The mean biomass ATP concentration in aerobic soils is around 10–11 μmol ATP g−1 biomass C, within a fairly narrow range. It is much lower in short-term incubated laboratory waterlogged soils. However, the biomass ATP concentration in waterlogged paddy soils under field conditions remains unknown. This is investigated. Methods: Soil microbial biomass C (biomass C), ATP, biomass ATP and heavy metal (Cd, Zn, and Cu) concentrations in soil and rice were measured in a Chinese paddy soil growing rice. Soils and plants were analyzed at day 0, 30, 75 and 90, over the 90 day growing period with inputs of inorganic fertilizer, or biochar and manure singly or in combination. Results: Both biomass C and ATP concentrations increased, range from 14.9–30.5% for microbial biomass C and 115.8–160.1% for ATP, from initial values until the end of the experiment following manure or biochar addition. An important result was that the biomass ATP concentration increased throughout the growth period. There were also significant negative correlations (p < 0.05) between total and available Cd and these three microbial parameters, despite the low levels of Cd. Over the same period, total plant Cd concentrations increased, and soil Cd decreased. This suggests that the rice acted as a bioaccumulator. The microbial biomass was then in a continually decreasingly toxic environment and responded rapidly by increasing its size. Conclusions: These results demonstrate clear differences in microbial energy dynamics between aerobic and anaerobic microbial populations. Both ATP and biomass C are useful bioindicators of the effects of cadmium contamination on microbial processes in waterlogged soil.

14062. 题目: Sensitivity of atmospheric CO2 to regional variability in particulate organic matter remineralization depths
文章编号: N18121704
期刊: Biogeosciences
作者: Jamie D. Wilson, Stephen Barker, Neil R. Edwards, Philip B. Holden, and Andy Ridgwell
更新时间: 2018-12-17
摘要: The concentration of CO2 in the atmosphere is sensitive to changes in the depth at which sinking particulate organic matter is remineralised: often described as a change in the exponent "b" of the Martin curve. Sediment trap observations from deep and intermediate depths suggest there is a spatially heterogeneous pattern of b, particularly varying with latitude, but disagree over the exact spatial patterns. Here we use a biogeochemical model of the phosphorus cycle coupled with a steady-state representation of ocean circulation to explore the sensitivity of preformed phosphate and atmospheric CO2 to spatial variability in remineralisation depths. A Latin hypercube sampling method is used to simultaneously vary the Martin curve indepedently within 15 different regions, as a basis for a regression-based analysis used to derive a quantitative measure of sensitivity. Approximately 30% of the sensitivity of atmospheric CO2 to changes in remineralisation depths is driven by changes in the Subantarctic region (36°S to 60°S), simliar in magnitude to the Pacific basin despite the much smaller area and lower productivity. Overall, the absolute magnitude of sensitivity is controlled by export production but the relative spatial patterns in sensitivity are predominantly constrained by ocean circulation pathways. The high sensitivity in the Subantarctic regions is driven by a combination of high export production and the high connectivity of these regions to regions important for the export of preformed nutrients such as the Southern Ocean and North Atlantic. Overall, regionally varying remineralisation depths contribute to variability in CO2 of between ±5–15 ppm relative to a global mean change in remineralisation depth. Future changes in the environmental and ecological drivers of remineralisation, such as temperature and ocean acidification, are expected to be most significant in the high latitudes where CO2 sensitivity to remineralisation is also highest. The importance of ocean circulation pathways to the high sensitivity in Subantarctic regions also has significance for past climates given the importance of circulation changes in the Southern Ocean.

14063. 题目: Shifts in organic sulfur cycling and microbiome composition in the red-tide causing dinoflagellate Alexandrium minutum during a simulated marine heat wave
文章编号: N18121703
期刊: Biogeosciences
作者: Elisabeth Deschaseaux, James O'Brien, Nachshon Siboni, Katherina Petrou, and Justin R. Seymour
更新时间: 2018-12-17
摘要: The biogenic sulfur compounds dimethylsulfide (DMS), dimethylsulfoniopropionate (DMSP) and dimethylsulfoxide (DMSO) are produced and transformed by diverse populations of marine microorganisms and have substantial physiological, ecological and biogeochemical importance spanning organism to global scales. Understanding the production and transformation dynamics of these compounds under shifting environmental conditions is important for predicting their roles in a changing ocean. Here, we report the physiological and biochemical response of Alexandrium minutum, a dinoflagellate with the highest reported intracellular DMSP content, exposed to a 6 day increase in temperature mimicking coastal marine heatwave conditions (+4°C and +12°C). Under mild temperature increases (+4°C), A. minutum growth was enhanced, with no measurable physiological stress response. However, under an acute increase in temperature (+12°C), A. minutum growth declined, photosynthetic efficiency (FV/FM) was impaired, and enhanced oxidative stress was observed. These physiological responses were accompanied by increased DMS and DMSO concentrations followed by decreased DMSP concentrations. At this higher temperature, we observed a cascading stress response in A. minutum, which was initiated 6h after the start of the experiment by a spike in DMS and DMSO concentrations and a rapid decrease in FV/FM. This was followed by an increase in reactive oxygen species (ROS) and an abrupt decline in DMS and DMSO on day 2 of the experiment. A subsequent decrease in DMSP coupled with a decline in the growth rate of both A. minutum and its associated total bacterial assemblage coincided with a shift in the composition of the A. minutum microbiome. Specifically, an increase in the relative abundance of OTUs matching the genus Oceanicaulis (17.0%), Phycisphaeraceae SM1A02 (8.8%) and Balneola (4.9%) as well as a decreased relative abundance of Maribacter (24.4%), Marinoscillum (4.7%) and Seohaeicola (2.7%), were primarily responsible for differences in microbiome structure observed between temperature treatments. These shifts in microbiome structure are likely to have been driven by either the changing physiological state of A. minutum cells, shifts in biogenic sulfur concentrations, or a combination of both. We suggest that these results point to the significant effect of heatwaves on the physiology, growth and microbiome composition of the red-tide causing dinoflagellate A. minutum, as well as potential implications for biogenic sulfur cycling processes and marine DMS emissions.

14064. 题目: The influence of natural organic matter on the adsorption of microcystin-LR by powdered activated carbon
文章编号: N18121702
期刊: Environmental Science: Water Research & Technology
作者: Asnika Bajracharya, Yen-Ling Liu, John J. Lenhart
更新时间: 2018-12-17
摘要: In this study, microcystin-LR (MC-LR) adsorption to four different types of powdered activated carbon (PAC) was evaluated to provide insight into the use of PAC to treat water containing MC-LR. MC-LR adsorption to the four PAC types (wood, coal blend, bituminous coal, and coconut shell) was studied in equilibrium and kinetic batch experiments utilizing a model water with different natural organic matter (NOM) concentrations (0, 5 and 10 mg L−1) and pH (5.2, 8.5 and 9.5). The effect of NOM type was evaluated by comparing MC-LR uptake in model water amended with Suwannee river fulvic acid or a NOM extracted from a natural water experiencing an algal bloom. The results demonstrated that the wood-based PAC removed MC-LR at the highest rate and to the greatest extent, which likely reflects that wood-based PAC typically contains a greater proportion of mesopores than the other types of PAC in this study. MC-LR removal was significantly reduced in the presence of NOM, with the impact being slightly higher for the algal-derived NOM compared to Suwannee river fulvic acid. MC-LR removal decreased with decreasing pH in the presence of NOM, but increased with decreasing pH in the absence of NOM. This suggests competition with NOM not only varies depending upon the source of NOM, but also on the solution pH as NOM interactions with PAC will vary with pH. Thus, properly determining PAC doses to treat MC-LR must account for the presence of NOM as well as the pH-dependent interactions of NOM with PAC as these interactions strongly influence MC-LR adsorption.
图文摘要:

14065. 题目: Soil dissolved organic matter affects mercury immobilization by biogenic selenium nanoparticles
文章编号: N18121701
期刊: Science of The Total Environment
作者: Xiaonan Wang, Xiangliang Pan, Geoffrey Michael Gadd
更新时间: 2018-12-17
摘要: Molecular weight (MW) heterogeneity is a fundamental property of dissolved organic matter (DOM) in soil, which has been demonstrated to influence the binding behaviour between DOM and engineered nanoparticles. In the present study, DOM, extracted from black soil, was dialyzed into four fractions: above 10,000 Da, 3500–10,000 Da, 1000–3500 Da and 100–1000 Da. Homoaggregation and fluorescence quenching titration of selenium nanoparticles (SeNPs) was examined in the presence of the different DOM fractions, as well as the consequences for immobilization of elemental mercury. It was found that the intermediate MW fraction (3500–10,000 Da) rather than the high MW DOM fraction was likely to adsorb to SeNPs. Generally, low MW DOM was expected to adsorb initially due to faster diffusion and these compounds would be displaced by high MW DOM over longer time period. However, the electrostatic barrier imparted by adsorbed DOM limited such displacement, leading to preferential adsorption of the intermediate MW fraction over the high MW fraction. Adsorbed DOM fractions, especially that of intermediate MW, enhanced the stability of SeNPs which favoured immobilization of elemental mercury. These findings show that MW exerts an important impact on DOM binding with SeNPs which, in consequence, governs the fate of SeNPs and mercury bioremediation performance.
图文摘要:

14066. 题目: Humic Acids Limit the Precipitation of Cadmium and Arsenate at the Brushite–Fluid Interface
文章编号: N18121606
期刊: Environmental Science & Technology
作者: Hang Zhai, Lijun Wang, Jörn Hövelmann, Lihong Qin, Wenjun Zhang, Christine V. Putnis
更新时间: 2018-12-16
摘要: Bioavailability and mobility of cadmium (Cd2+) and arsenate (As5+) in soils can be effectively lowered through the dissolution of brushite (dicalcium phosphate dihydrate, CaHPO4·2H2O) coupled with the precipitation of a more stable mineral phase containing both Cd and As. Due to the ubiquitous presence of humic acid (HA) in soil environments, it is more complex to predict the fate of dissolved Cd and As during such sequestration. Here, we used in situ atomic force microscopy (AFM) to image the kinetics of simultaneous precipitation of Cd and As at the brushite–fluid interface in the presence of HA. Results show that HA inhibits the formation of both amorphous and crystalline Cd(5–x)Cax(PO4)(3–y)(AsO4)y(OH) on the (010) face of brushite. A combination of X-ray photoelectron spectroscopy (XPS) and real-time surface-enhanced Raman spectroscopy (SERS) reveals that part of As5+ reduction into As3+ with HA and [HA-Cd] complexation occurs, modulating the concentrations of free Cd2+ and As5+ ions to inhibit subsequent precipitation of a Cd(5–x)Cax(PO4)(3–y)(AsO4)y(OH) phase on the dissolving brushite surface. A combination of AFM imaging, SERS analyses, and PhreeqC simulations suggests that environmentally relevant humic substances can limit the precipitation of Cd and As at mineral surfaces through a mechanism of oxidation/reduction and aqueous/surface complexation. This may exacerbate the transportation of these contaminants into waters by subsurface fluid flow, and research attempts to weaken the negative effect of HA are needed.
图文摘要:

14067. 题目: Unraveling the sources and fluorescence compositions of dissolved and particulate organic matter (DOM and POM) in Lake Taihu, China
文章编号: N18121605
期刊: Environmental Science and Pollution Research
作者: Lü Weiwei, Yao Xin, Shao Keqiang, Zhang Baohua, Gao Guang
更新时间: 2018-12-16
摘要: Organic matter (OM), a complex entity with diverse functional groups and molecular sizes, has important effects on aquatic systems. We studied the optical compositions and sources of dissolved organic matter (DOM) and particulate organic matter (POM) in Lake Taihu, a large, shallow and eutrophic lake in China. Significant differences in optical compositions and sources occurred between the POM and DOM. The temporal–spatial distribution of the fluorescence indices suggested that the POM in Lake Taihu was mainly from autochthonous sources, but more exogenous characteristics were shown in POM in the river mouths compared with other regions. The chromophoric DOM in Lake Taihu mainly displayed autochthonous characteristics. The POM–DOM PARAFAC model was used to examine OM optical composition and five components were identified, which contained three protein-like components (C1, C2, and C5), a microbial humic-like component (C3), and a terrestrial humic-like component (C4). The POM was dominated by C5 in summer and autumn and C3 in winter and spring, and the DOM was dominated by protein-like components (C1, C2, and C5) through the entire year. The algae-dominated region had a relative higher contribution of tryptophan-like components of POM compared with the macrophyte-dominated region. A conceptual model based on the theory of “four phases of cyanobacteria bloom development” was proposed to fully describe the relationship between POM–DOM exchanges and cyanobacteria bloom development.

14068. 题目: Effects of biochar and dicyandiamide combination on nitrous oxide emissions from Camellia oleifera field soil
文章编号: N18121604
期刊: Environmental Science and Pollution Research
作者: Bang-Liang Deng, Shu-Li Wang, Xin-Tong Xu, Hua Wang, Dong-Nan Hu, Xiao-Min Guo, Qing-Hua Shi, Evan Siemann, Ling Zhang
更新时间: 2018-12-16
摘要: Greenhouse gas emissions from agricultural soils contribute substantially to global atmospheric composition. Nitrous oxide (N2O) is one important greenhouse gas induces global warming. Nitrification inhibitors (NI) or biochar can be effective soil N2O emission mitigation strategies for agricultural soils. However, due to differences in crop physiological traits or agricultural management, the effectiveness of mitigation strategies varies among agricultural systems. Camellia oleifera is a woody oil plant widely grown and requires intensive N input, which will potentially increase N2O emissions. Thereby, mitigation of N2O emissions from C. oleifera field soil is vital for sustainable C. oleifera development. Besides NI, incorporation of C. oleifera fruit shell-derived biochar into its soil will benefit waste management and simultaneous mitigation of N2O emissions but this has not been investigated. Here, we conducted two studies to examine effects of biochar addition and NI (dicyandiamide, DCD) application on N2O emissions from C. oleifera field soil with different N (urea or NH4NO3) and incubation temperatures. Biochar effects on nitrification rates varied among N treatments. Biochar applied in combination with DCD further reduced nitrification rates (for urea treatment, decreased from 1.1 to 0.3 mg kg−1 day−1). Biochar addition consistently increased soil N2O emissions (for urea treatment, increased from 0.03 to 0.08 ng g−1 h−1) and their temperature sensitivity. DCD application reduced soil N2O emissions with greater reductions with urea application. In future cultivation of intensively managed C. oleifera gardens, NI should be applied to mitigate N2O emissions if biochar is added, especially when urea is used.

14069. 题目: On the separation between inorganic and organic fractions of suspended matter in a marine coastal environment
文章编号: N18121603
期刊: Progress in Oceanography
作者: M. Schartau, R. Riethmüller, G. Flöser, J.E.E. van Beusekom, H. Krasemann, R. Hofmeister, K. Wirtz
更新时间: 2018-12-16
摘要: A central aspect of coastal biogeochemistry is to determine how nutrients, lithogenic- and organic matter are distributed and transformed within coastal and estuarine environments. Analyses of the spatio-temporal changes of total suspended matter (TSM) concentration indicate strong and variable linkages between intertidal fringes and pelagic regions. In particular, knowledge about the organic fraction of TSM provides insight to how biogenic and lithogenic particulate matter are distributed in suspension. In our study we take advantage of a set of over 3000 in situ Loss on Ignition (LoI) data from the Southern North Sea that represent fractions of particulate organic matter (POM) relative to TSM (LoI POM:TSM). We introduce a parameterization (POM-TSM model) that distinguishes between two POM fractions incorporated in TSM. One fraction is described in association with mineral particles. The other represents a seasonally varying fresh pool of POM. The performance of the POM-TSM model is tested against data derived from MERIS/ENVISAT-TSM products of the German Bight. Our analysis of remote sensing data exhibits specific qualitative features of TSM that can be attributed to distinct coastal zones. Most interestingly, a transition zone between the Wadden Sea and seasonally stratified regions of the Southern North Sea is identified where mineral associated POM appears in concentrations comparable to those of freshly produced POM. We will discuss how this transition is indicative for a zone of effective particle interaction and sedimentation.The dimension of this transition zone varies between seasons and with location. Our proposed POM-TSM model is generic and can be calibrated against in situ data of other coastal regions.

14070. 题目: Effect of inorganic fertilisers and organic amendments on soil aggregation and biochemical characteristics in a weathered tropical soil
文章编号: N18121602
期刊: Soil and Tillage Research
作者: S. Mangalassery, D. Kalaivanan, Prabha S. Philip
更新时间: 2018-12-16
摘要: Highly weathered laterite soils are a characteristic feature of humid tropics with undulating topography and high rainfall. The crop of cashew (Anacardium occidentale L.) has been cultivated in such landscapes, mainly to prevent further degradation due to the drought hardiness of cashew and requirement of very limited soil disturbances for its cultivation. Providing proper nutrient management is important for balancing the nutrient removal by tree crops especially in poor fertile soils. A study was initiated, after 5 years of application of inorganic fertilisers and organic amendments to cashew in a weathered tropical soil, to evaluate the effects of organic and inorganic sources of nutrients on soil aggregation and biochemical characteristics. The experiment consisted of 11 treatments as Farm Yard Manure (FYM) alone; FYM + biofertiliser consortia; FYM, rock phosphate and wood ash; poultry manure; In situ composting using recyclable cashew biomass and weeds; In situ composting using recyclable cashew biomass and weeds + green manuring; vermicomposting of recyclable cashew biomass; FYM + organic cakes + recyclable cashew biomass + biofertiliser consortia; recommended dose of nitrogen, phosphorus and potassium fertiliser (NPK fertiliser); recommended NPK fertiliser + FYM; and control without nutrient application. Soil samples were collected from surface 0–30 cm layer. The soil samples were fractionated into three aggregate sizes, i.e., >2 mm (large macroaggregates), 0.25–2 mm (small macroaggregates), 0.053 to 0.25 mm (microaggregates) and <0.053 mm (silt + clay size fraction) using wet sieving. The results indicated that the organic sources of nutrient application increased the proportion of large and small macroaggregates. The treatments receiving only inorganic nutrients and no nutrients contained significantly higher silt + clay fractions (47.7 and 45.5% respectively). A higher percentage of water stable aggregates (47.4–70.7%) and increased aggregate stability (mean weight diameter) (0.78–1.26 mm) was recorded with the application of organic sources of nutrients. Aggregates in the silt + clay size faction and microaggregates recorded significantly higher carbon compared to small and large macroaggregates. Compared to control, the application of different organic amendments increased the soil organic matter (SOM) by 2.2–12.7% in silt + clay size fraction; 14.6–37.0% in microaggregates; 18.4–51.7% in small macroaggregates and 17.7–50.9% in large macroaggregates. Our findings reinforce that the annual application of manures and amendments to weathered tropical soil is important to improve biological properties of soil in terms of soil enzyme activities, microbial carbon and nitrogen, and to prevent further degradation of soil under such fragile environment.

14071. 题目: Effect of Humic Acids on Batch Anaerobic Digestion of Excess Sludge
文章编号: N18121601
期刊: Water Research
作者: Ji Li, Xiaodi Hao, Mark C.M. van Loosdrecht, Yuqi Luo
更新时间: 2018-12-16
摘要: Anaerobic digestion (AD) is a sustainable pathway towards recovering chemical energy from excess sludge, and humic substances (HSs) contained in sludge can inhibit energy (methane/CH4) conversion efficiency. This study aims to investigate the impact of humic acids (HA) on the various processes in a batch anaerobic digestion process. For this purpose, “clean” sludge was cultivated in a laboratory to avoid HSs presence. The cultivated sludge was used in a series of batch experiments, with humic acids added at different levels. A complete AD test, as well as three sub-phase tests (hydrolytic phase; acidogenic phase; methanogenic phase) was performed and analyzed with and without HA dosing. In the single-phase AD system, dosing with HA inhibited the methanogenic efficiency by 35.1% at HA:VSS=15%. However, the effects of HA on the three sub-phases revealed something very different. HA inhibited hydrolytic efficiency by 38.2%, promoted acidogenic efficiency by 101.5%, and finally inhibited methanogenic efficiency by 52.2%. The combined efficiency of the three sub-phases without HA dosing is calculated at 15.7%; and with HA dosing (HA:VSS=15%) at 10.2%. Overall, the combined inhibition efficiency of the three sub-phases is equal to 35.0%, which is almost identical (35.1%) to the result observed in the single-phase AD process. The possible mechanisms behind the phenomena were analyzed and summarized in the context.
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14072. 题目: Biochar improved rice yield and mitigated CH4 and N2O emissions from paddy field under controlled irrigation in the Taihu Lake Region of China
文章编号: N18121514
期刊: Atmospheric Environment
作者: Yang shihong, Xiao Yanan, Sun Xiao, , Jiang Zewei, Xu Junzeng
更新时间: 2018-12-15
摘要: Biochar application is proposed having a potential of inhibiting greenhouse gases emissions from paddy fields, which is considered to be a main source of atmospheric greenhouse gases. However, the impacts of biochar on greenhouse gases from paddy field have not been investigated under controlled irrigation (CI). Field experiments were conducted during 2016-2017 to determine the effect of biochar application combined with controlled irrigation on rice yield and methane (CH4) and nitrous oxide (N2O) emission from paddy fields in the Taihu Lake Region of China. Four treatments (0 t ha-1 biochar + CI, 20 t ha-1 biochar + CI, 40 t ha-1 biochar + CI, and 40 t ha-1 biochar + flooding irrigation (FI), named CA, CB, CC and FC, respectively) were designed in this study. The results showed that the effect of biochar application on greenhouse gases emissions from paddy fields under controlled irrigation had significant interannual differences. In the first season, CC decreased the global warming potential(GWP) of CH4 and N2O emission, and the CB increased the GWP of CH4 and N2O emission compared to CA, but these differences were not significant. For the second season, CB and CC decreased the GWP of CH4 and N2O emission by 35.7% and 21.5% significantly compared to CA due to the significant mitigation of CH4 and N2O emission. Biochar application significantly increased CH4 emission and decreased N2O emission from paddy fields under flooding irrigation compared to controlled irrigation (CC), which led to the FC’s GWP was 1.70 and 5.47 times higher than CC’s in the first and second season. In addition, biochar application increased soil organic carbon, dissolved organic carbon and total nitrogen contents of paddy fields under controlled irrigation. And CB and CC increased rice yield by 16.7% and 24.3% and irrigation water productivity by 26.1% and 30.8% compared with CA (mean of two seasons). These results suggest that 20 and 40 t ha-1 biochar can be utilized under controlled irrigation not only for mitigation of CH4 and N2O emission but also to increase rice yield, soil fertility and irrigation water productivity. Therefore, the combination of biochar amendment and controlled irrigation might be a good option for mitigating greenhouse gases emission and realizing the sustainable utilization of soil and water resources of paddy fields in the Taihu Lake Region of China.

14073. 题目: Remobilization of old permafrost carbon to Chukchi Sea sediments during the end of the last deglaciation
文章编号: N18121513
期刊: Global Biogeochemical Cycles
作者: Jannik Martens, Birgit Wild, Christof Pearce, Tommaso Tesi, August Andersson, Lisa Bröder, Matt O’Regan, Martin Jakobsson, Martin Sköld, Laura Gemery, Thomas M. Cronin, Igor Semiletov, Oleg V. Dudarev, Örjan Gustafsson
更新时间: 2018-12-15
摘要: Climate warming is expected to destabilize permafrost carbon (PF‐C) by thaw‐erosion and deepening of the seasonally‐thawed active layer, and thereby promote PF‐C mineralization to CO2 and CH4. A similar PF‐C remobilization might have contributed to the increase in atmospheric CO2 during deglacial warming after the last glacial maximum. Using carbon isotopes and terrestrial biomarkers (Δ14C, δ13C, lignin phenols), this study quantifies deposition of terrestrial carbon originating from permafrost in sediments from the Chukchi Sea (core SWERUS‐L2‐4‐PC1) during the late Allerød warm period starting at 13,000 cal yr BP, the Younger Dryas and the early Holocene warming until 11,000 cal yr BP, and compares this period with the late Holocene, from 3,650 yr BP until present. Dual‐carbon‐isotope‐based source apportionment demonstrates that Ice Complex Deposit (ICD) – ice and carbon rich permafrost from the late Pleistocene (also referred to as Yedoma) – was the dominant source of organic carbon (66 ± 8%; mean ± s.d.) to sediments during the end of the deglaciation, with fluxes more than twice as high (8.0 ± 4.6 g m‐2 yr‐1) as in the late Holocene (3.1 ± 1.0 g m‐2 yr‐1). These results are consistent with late deglacial PF‐C remobilization observed in a Laptev Sea record, yet in contrast with PF‐C sources, which at that location were dominated by active layer material from the Lena River watershed. Release of dormant PF‐C from erosion of coastal permafrost during the end of the last deglaciation indicates vulnerability of ICD in response to future warming and sea level changes.

14074. 题目: Large‐scale ecosystem engineering by flamingos and fiddler crabs on West‐African intertidal flats promote joint food availability
文章编号: N18121512
期刊: Oikos
作者: El‐Hacen M. El‐Hacen, Tjeerd J. Bouma, Puck Oomen, Theunis Piersma, Han Olff
更新时间: 2018-12-15
摘要: Although the ecosystem engineering concept is well established in ecology, cases of joint engineering by multiple species at large scales remain rare. Here, we combine observational studies and exclosure experiments to investigate how co‐occurring greater flamingos Phoenicopterus roseus and fiddler crabs Uca tangeri promote their own and each other's food availability by creating a spatially complex mosaic of depressions (bowls, gullies) and hummocks (plateaus, mounds) in the intertidal zone. This results in a mosaic of microhabitats with different tidal inundation regimes. These microhabitats are spatially organized with labyrinth‐like patterns in the high intertidal zone and spotted patterns in the lower intertidal, both of which likely arise from biophysical interactions between these organisms and hydrodynamic forces. We show that the resulting spatial complexity is vital for biofilm production. The depression microhabitats were wetter and richer in organic matter and biofilms compared with hummocks. Excluding flamingos and crabs resulted in an increase in biofilm biomass over the shorter term (six months), but a decrease over the longer term (after one year). Moreover, our results strongly suggest that these biogeomorphological microhabitats in the mosaics were maintained by the feeding activities of flamingos and to a lesser extent crabs. During a period of flamingo exclusion, all the spotted patterns filled up with sediment, while the exclusion of crabs led to gradual sediment accumulation in the labyrinth‐like patterns. Collectively, these findings provide empirical evidence for large‐scale joint promotion of food availability by multiple species in a marine ecosystem.

14075. 题目: Nitrate Removal via a Formate Radical-Induced Photochemical Process
文章编号: N18121511
期刊: Environmental Science & Technology
作者: Gongde Chen, Sergei Hanukovich, Michelle Chebeir, Phillip Christopher, Haizhou Liu
更新时间: 2018-12-15
摘要: Removal of excess nitrate is critical to balance the nitrogen cycle in aquatic systems. This study investigated a novel denitrification process by tailoring photochemistry of nitrate with formate. Under UV light irradiation, short-lived radicals (i.e., HO, NO2, and CO3) generated from nitrate photolysis partially oxidized formate to highly reductive formate radical (CO2). CO2 further reduced nitrogen intermediates generated during photochemical denitrification (mainly NO, HNO, and N2O) to gas-phase nitrogen (i.e., N2O and N2). The degradation kinetics of total dissolved nitrogen was mainly controlled by the photolysis rates of nitrate and nitrite. The distribution of final products was controlled by the reaction between CO2 and N2O. To achieve a simultaneous and complete removal of dissolved nitrogen (i.e., nitrate, nitrite, and ammonia) and organic carbon, the formate-to-nitrate stoichiometry was determined as 3.1 ± 0.2 at neutral pH in deionized water. Solution pH impacted the removal rates of nitrate and nitrite but not that of total dissolved nitrogen or formate. The presence of dissolved organic matter at levels similar to those in groundwater had a negligible impact on the photochemical denitrification process. A high denitrification efficiency was also achieved in a synthetic groundwater matrix. Outcome from this study provides a potential denitrification technology for decentralized water treatment and reuse facilities to abate nitrate in local water resources.
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14076. 题目: Elevated Manganese Concentrations in United States Groundwater, Role of Land Surface–Soil–Aquifer Connections
文章编号: N18121510
期刊: Environmental Science & Technology
作者: Peter B. McMahon, Kenneth Belitz, James E. Reddy, Tyler D. Johnson
更新时间: 2018-12-15
摘要: Chemical data from 43 334 wells were used to examine the role of land surface–soil–aquifer connections in producing elevated manganese concentrations (>300 μg/L) in United States (U.S.) groundwater. Elevated concentrations of manganese and dissolved organic carbon (DOC) in groundwater are associated with shallow, anoxic water tables and soils enriched in organic carbon, suggesting soil-derived DOC supports manganese reduction and mobilization in shallow groundwater. Manganese and DOC concentrations are higher near rivers than farther from rivers, suggesting river-derived DOC also supports manganese mobilization. Anthropogenic nitrogen may also affect manganese concentrations in groundwater. In parts of the northeastern U.S. containing poorly buffered soils, ∼40% of the samples with elevated manganese concentrations have pH values < 6 and elevated concentrations of nitrate relative to samples with pH ≥ 6, suggesting acidic recharge produced by the oxidation of ammonium in fertilizer helps mobilize manganese. An estimated 2.6 million people potentially consume groundwater with elevated manganese concentrations, the highest densities of which occur near rivers and in areas with organic carbon rich soil. Results from this study indicate land surface–soil–aquifer connections play an important role in producing elevated manganese concentrations in groundwater used for human consumption.
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14077. 题目: Environmental Conditions Affecting Re‐release from Particulate Matter of 4‐Nonylphenol into an Aqueous Medium
文章编号: N18121509
期刊: Environmental Toxicology and Chemistry
作者: Rebecca Lyons, Trevor Togashi, Chad Bowyer
更新时间: 2018-12-15
摘要: 4‐Nonylphenol (4‐NP) is a persistent organic pollutant with endocrine disrupting properties. This non‐polar product of microbial degradation derived from the surfactant nonylphenol polyethoxylate (NPE), 4‐NP is capable of long range transport attached to particulates. Bioactive concentrations of 4‐NP have been found in the surface water, soils, snow and particulate matter of the Eastern Sierra Nevada Mountains (SNM), hundreds of miles from its origins. As a result of particulate deposition, seasonal and glacial snow pack concentrations measured 20‐100 times higher than in surface waters. Batch desorption assays were run on particulate matter dosed with 4‐NP. Desorption was measured in 63‐500 μm particles under two different temperature conditions with varying fractions of organic carbon (OC) in turbulent or undisturbed states. Lower temperatures (4°C) decreased the mean percentage of 4‐NP released from particulates in disturbed and undisturbed conditions, while the mean percentage of 4‐NP released at 20°C was reduced by agitation; the effect of agitation at 4°C was neither practically nor statistically significant. Particulates with higher percent OC (75%) released very little of the bound 4‐NP (0.53%) compared to particulates containing 4‐5% OC, which released up to 13%. Larger particles release the least amount of 4‐NP, while smaller particles released the most. Water and sediment samples taken from below the Palisades Glacier in the SNM showed the greatest 4‐NP concentrations directly below the glacier, implying that glacial particulates will release adsorbed 4‐NP. This article is protected by copyright. All rights reserved

14078. 题目: Changes in the pattern of polycyclic aromatic hydrocarbons in soil treated with biochar from a multiyear field experiment
文章编号: N18121508
期刊: Chemosphere
作者: Alessandro G. Rombolà, Daniele Fabbri, Silvia Baronti, Francesco Primo Vaccari, Lorenzo Genesio, Franco Miglietta
更新时间: 2018-12-15
摘要: The influence of biochar added to an agricultural soil on polycyclic aromatic hydrocarbon (PAH) levels, PAH diagnostic ratios and soil properties was investigated in a five-year field experiment. The experiment was carried out in an Italian vineyard and included two biochar treatments: 16.5 t ha−1 of biochar applied in 2009 (soil B); 16.5 t ha−1 in 2009 and further 16.5 t ha−1 in 2010 (soil BB). A set of 75 samples that included five replicates and a control soil (untreated) was characterized in terms of organic carbon, pH, cation exchange capacity (CEC), bulk density and concentration of PAHs. Biochar addition to soil caused an increase in organic carbon, pH and CEC, and a decrease of bulk density. After almost two years the first application of biochar, PAH concentrations were higher in soil B (56 ng g−1) and BB (153 ng g−1) in comparison to control soil (24 ng g−1). Thereafter, PAH concentrations decreased significantly, but the original PAHs levels were reached only in soil B after five years. The naphthalene/(naphthalene + phenanthrene) ratios were higher in the treated soils in accordance to the dominance of naphthalene in the original biochar. The cross plots naphthalene/(naphthalene + phenanthrene) vs. fluoranthene/(fluoranthene + pyrene) enabled to trace the signature of biochar PAHs up to five years after its first application. Diagnostic ratios can be a useful tool to study the persistence of PAHs introduced in soil by biochar when the pattern of these contaminants in biochar and original soil are different.

14079. 题目: Vertical profiles and distributions of aqueous endocrine-disrupting chemicals in different matrices from the Pearl River Delta and the influence of environmental factors
文章编号: N18121507
期刊: Environmental Pollution
作者: Jian Gong, Yong Ran, Dainan Zhang, Diyun Chen, Haiyan Li, Youda Huang
更新时间: 2018-12-15
摘要: The occurrence and distributions of selected endocrine-disrupting chemicals (EDCs), along with related environmental factors, were investigated in two rivers and six reservoirs in the Pearl River Delta. The vertical profiles of aqueous 4-tert-octylphenol (OP), 4-nonylphenol (NP), and estrone (E1) were constant, with little change in concentration between the surface and the river bottom, while higher aqueous concentrations of bisphenol A (BPA) were found in the bottom layers of the rivers. OP and NP in suspended particulate matter (SPM) were transferred from the surface to the bed layer, ultimately accumulating in the sediment. However, the particulate profiles of BPA and E1 both featured increases from the surface to the bottom layers and attenuation in the river bed. Dissolved oxygen (DO), water temperature, and pH were negatively correlated with the EDC concentrations, and negative relationships between DO and distribution coefficient (Kd) values for OP and NP were found as well. This indicated that these environmental parameters were primarily responsible for the EDC vertical distribution and SPM-water partitioning in the rivers. Positive relationships were observed between chlorophyll a and EDCs in the particulate phase, and the algae/water Kd values for EDCs in reservoirs were comparable to the SPM/water and sediment/water Kd values from the rivers. These results suggest that algae played an important role in regulating the distribution of EDCs in surface waters. Moreover, relationships between UV absorbance and EDCs revealed that π-π interactions were among the dissolved organic carbon (DOC)-EDC binding mechanisms and that DOC fractions with higher degrees of aromaticity and humification possessed higher affinities towards EDCs.
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14080. 题目: Assessment of forest fire impacts on carbonaceous aerosols using complementary molecular marker receptor models at two urban locations in California's San Joaquin Valley
文章编号: N18121506
期刊: Environmental Pollution
作者: Min-Suk Bae, Matthew J. Skiles, Alexandra M. Lai, Michael R. Olson, Benjamin de Foy, James J. Schauer
更新时间: 2018-12-15
摘要: Two hundred sixty-three fine particulate matter (PM2.5) samples were collected over fourteen months in Fresno and Bakersfield, California. Samples were analyzed for organic carbon (OC), elemental carbon (EC), water soluble organic carbon (WSOC), and 160 organic molecular markers. Chemical Mass Balance (CMB) and Positive Matrix Factorization (PMF) source apportionment models were applied to the results in order to understand monthly and seasonal source contributions to PM2.5 OC. Similar source categories were found from the results of the CMB and PMF models to PM2.5 OC across the sites. Six source categories with reasonably stable profiles, including biomass burning, mobile, food cooking, two different secondary organic aerosols (SOAs) (i.e., winter and summer), and forest fires were investigated. Both the CMB and the PMF models showed a strong seasonality in contributions of some sources, as well as dependence on wind transport for both sites. The overall relative source contributions to OC were 24% CMB wood smoke, 19% CMB mobile sources, 5% PMF food cooking, 2% CMB vegetative detritus, 17% PMF SOA summer, 22% PMF SOA winter, and 12% PMF forest fire. Back-trajectories using the Weather Research and Forecasting model combined with the FLEXible PARTicle dispersion model (WRF-FLEXPART) were used to further characterize wind transport. Clustering of the trajectories revealed dominant wind patterns associated with varying concentrations of the different source categories. The Comprehensive Air Quality Model with eXtensions (CAMx) was used to simulate aerosol transport from forest fires and thus confirm the impacts of individual fires, such as the Rough Fire, at the measurement sites.
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