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28921. 题目: High‐frequency variability of small‐particle carbon export flux in the Northeast Atlantic
文章编号: N18120909
期刊: Global Biogeochemical Cycles
作者: Roséanne Bol, Stephanie, Anne Henson, Anna Rumyantseva, Nathan Briggs
更新时间: 2018-12-09
摘要: The biological carbon pump exports carbon fixed by photosynthesis out of the surface ocean and transfers it to the deep, mostly in the form of sinking particles. Despite the importance of the pump in regulating the air‐sea CO₂ balance, the magnitude of global carbon export remains unclear, as do its controlling mechanisms. A possible sinking flux of carbon to the mesopelagic zone may be via the mixed‐layer pump: a seasonal net detrainment of POC‐rich surface waters, caused by sequential deepening and shoaling of the mixed layer. In this study, we present a full year of daily small‐particle particulate organic carbon (POC) concentrations derived from glider optical backscatter data, to study export variability at the Porcupine Abyssal Plain (PAP) sustained observatory in the Northeast Atlantic. We observe a strong seasonality in small particle transfer efficiency, with a maximum in winter and early spring. By calculating daily POC export driven by mixed‐layer variations, we find that the mixed‐layer pump supplies an annual flux of at least 3.0 ± 0.9 g POC m⁻² yr⁻¹ to the mesopelagic zone, contributing between5 and 25% of the total annual export flux and likely contributing to closing a gap in the mesopelagic carbon budget found by other studies. These are, to our best knowledge, the first high‐frequency observations of export variability over the course of a full year. Our results support the deployment of bio‐optical sensors on gliders to improve our understanding of the ocean carbon cycle on temporal scales from daily to annual.

28922. 题目: The Spatial Variability of Organic Matter and Decomposition Processes at the Marsh Scale
文章编号: N18120908
期刊: Journal of Geophysical Research: Biogeosciences
作者: F. Yousefi Lalimi, S. Silvestri, A. D’Alpaos, M. Roner, M. Marani
更新时间: 2018-12-09
摘要: Accretion rate in salt marshes is governed by inorganic soil deposition and soil organic matter (SOM) accumulation. Existing (limited) observations and modelling results suggest SOM amounts, biomass production and decomposition processes should vary widely, and systematically, at the marsh scale. However, we lack observations aimed at understanding how SOM production is modulated spatially within a marsh, and at elucidating the relative importance of the controlling processes. The little existing data suggest that competing effects between biomass production and decomposition processes determine an approximately spatially constant contribution of SOM to total accretion. Here we investigate this idea using concurrent observations of SOM and decomposition rates from marshes in North Carolina. Our results indicate that systematic spatial variations in SOM are small, possibly as a result of an at least partial compensation of opposing trends in biomass production and decomposed organic matter. Our analyses show that deeper soil layers are, on average, characterized by lower decomposition rates and higher stabilization factors than shallower layers, likely because of differences in the persistence of water‐logged conditions. Overall, decomposition processes are sufficiently rapid that the labile material in the fresh biomass is completely decomposed before it can be sufficiently buried and stabilized. Our findings point to the importance of the fraction of initially refractory material and of stabilization processes in determining the final distribution of SOM within the soil column.

28923. 题目: Comparison of soil organic matter transformation processes in different alpine ecosystems in the Qinghai‐Tibet Plateau
文章编号: N18120907
期刊: Journal of Geophysical Research: Biogeosciences
作者: Qiuyu Chen, Tianzhu Lei, Yingqin Wu, Guicai Si, Chuanwu Xi, Gengxin Zhang
更新时间: 2018-12-09
摘要: Soils in the Qinghai‐Tibet Plateau (QTP) are young in terms of development and form a thin, skeletal soil layer because the gravel parent materials are glaciofluvial deposit, eluvium and fluvial sediment, which are extremely sensitive to global climate change. The lack of understanding of soil organic matter (SOM) transformation processes in this region hinders the prediction of SOM stocks under future climate conditions. In this study, SOM transformation processes were investigated by density groupings and pyrolysis‐gas chromatography/tandem‐mass spectrometry (Py‐GC‐MS/MS) in five alpine ecosystems: alpine desert (AD), alpine grassland (AG), alpine meadow (AM), alpine wetland (AW) and alpine forest (AF). The roles of microbial community in different density fractions were elucidated. Soil samples were separated into three fractions with NaI solution: labile fraction (F_L, ρ≤1.6 g cm^‐3), moderate fraction (F_M, 1.6<ρ<2.25 g cm^‐3) and recalcitrant fraction (F_R, ρ≥2.25 g cm^‐3). The following results were obtained. (1) The ratios of different fractions (F_M/F_L, F_R/F_M and F_R/F_L) indicated the transformation processes of SOM, and ratios less than one represented degradation. The transformation processes were similar in AG and AM and in AD, AW and AF but differed from each other. (2) Fungi preferred to degrade plant detritus, which mainly affected F_L, whereas bacteria chiefly affected F_M. (3) Precipitation altered vegetation type and soil pH, thus affecting communities and microorganism activities and resulting in the above differences. These findings highlight the importance of understanding the limited transformation processes of SOM in ecosystems to predict the impact of climate change on SOM preservation.

28924. 题目: Biological transformation of Arctic dissolved organic matter in a NE Greenland fjord
文章编号: N18120906
期刊: Limnology and Oceanography
作者: Maria Lund Paulsen, Oliver Müller, Aud Larsen, Eva Friis Møller, Mathias Middelboe, Mikael K. Sejr, Colin Stedmon
更新时间: 2018-12-09
摘要: Arctic waters are often enriched with terrestrial dissolved organic matter (DOM) characterized by having elevated visible wavelength fluorescence (commonly termed humic‐like). Here, we have identified the sources of fluorescent DOM (FDOM) in a high Arctic fjord (Young Sound, NE Greenland) influenced by glacial meltwater. The biological transformation of FDOM was further investigated using plankton community size‐fractionation experiments. The intensity of ultraviolet fluorescence (commonly termed amino acid‐like) was highly variable and positively correlated to bacterial production and mesozooplankton grazing. The overall distribution of visible FDOM in the fjord was hydrographically driven by the high‐signal intrusion of Arctic terrestrial DOM from shelf waters and dilution with glacial runoff in the surface waters. However, the high‐intensity visible FDOM that accumulated in subsurface waters in summer was not solely linked to allochthonous sources. Our data indicate that microbial activity, in particular, protist bacterivory, to be a source. A decrease in visible FDOM in subsurface waters was concurrent with an increase in bacterial abundance, indicating an active bacterial uptake or modification of this DOM fraction. This was confirmed by net‐loss of visible FDOM in experiments during summer when bacterial activity was high. The degradation of visible FDOM appeared to be associated with bacteria belonging to the order Alteromonadales mainly the genus Glaciecola and the SAR92 clade. The findings provide new insight into the character of Arctic terrestrial DOM and the biological production and degradation of both visible and UV wavelength organic matter in the coastal Arctic.

28925. 题目: Long‐term mineral fertilization in paddy soil alters the chemical structures and decreases the fungistatic activities of humic acids
文章编号: N18120905
期刊: European Journal of Soil Science
作者: M. Wu, S.P Wei, J. Liu, M. Liu, C.Y. Jiang, Z.P. Li
更新时间: 2018-12-09
摘要: Fungistatic activity is a newly identified ecological function for soil humic acids. However, the relation between fungistatic activities of soil humic acids and their chemical structures is still unclear. In addition, how fertilizer application affects fungistatic activity is still unknown. We sampled paddy soils with different long‐term fertilizer schemes, namely: unfertilized control (CK), mineral fertilizer applied (NPK) and mineral fertilizer applied plus straw return (NPKRS). Soil humic acids were extracted and their fungistatic activities against fourteen phytopathogenic fungi were investigated to evaluate their ecological functions. The humic acids from NPK and NPKRS treatments showed much smaller fungistatic effects than those from CK treatments. The chemical structures of humic acids were investigated by ¹³C nuclear magnetic resonance (¹³C NMR) spectroscopy. Long‐term fertilization significantly changed the chemical structure of soil humic acid, and the variation in chemical structure affected the fungistatic activities. The relative content of alkoyl C and alkyl C, the ratio alkoyl C/alkyl C and aliphaticity all had positive correlations with the fungistatic effects of humic acids. That indicated humic acids with more aliphatic and decomposable structures showed more fungistatic activity. From the results, we believe that long‐term application of mineral fertilizer in paddy fields makes the soil humic acids less aliphatic and more recalcitrant, and concomitantly weakens their ability to inhibit phytopathogenic fungi.

28926. 题目: Enhanced nitrogen removal in biochar-added surface flow constructed wetlands: dealing with seasonal variation in the north China
文章编号: N18120904
期刊: Environmental Science and Pollution Research
作者: Jing Li, Jinlin Fan, Daoxing Liu, Zhen Hu, Jian Zhang
更新时间: 2018-12-09
摘要: In the present study, the performance of surface flow constructed wetlands (SFCWs) added with different dosage of biochar (group A 0%, group B 10%, group C 20%; v/v) was investigated, to evaluate the effect of biochar on nitrogen removal of a constructed wetland. No significant difference was observed in NH₄⁺-N removal among three groups even during different seasons. Labile organic carbon released from biochar distinctly enhanced denitrification process, which improved NO₃⁻-N removal efficiency by 4.58% in group B and 10.33% in group C. More importantly, compared with group A, biochar addition increased plant N removal by 82.24% and 192.11% in groups B and C, respectively. This result indicated that biochar could increase the accumulation of plant net biomass. In addition, TN removal of group A was much lower at low temperature (4.9 °C). However, no obvious influence of temperature on TN removal was observed in groups B and C with biochar addition. Microbial community analysis showed that, compared with that in group A, the total relative abundance of the main denitrification bacteria (Proteobacteria, Firmicutes, and Bacteroidetes) increased by 0.81% in group B and 13.63% in group C. These results provide a reasonable strategy for improving the performance of SFCWs under cold climate.

28927. 题目: Composts as alternative to inorganic fertilization for cereal crops
文章编号: N18120903
期刊: Environmental Science and Pollution Research
作者: Teresa Hernandez, Carmen Chocano, Maria Dolores Coll, Carlos Garcia
更新时间: 2018-12-09
摘要: The use of treated organic products as fertilizers and soil amendments not only results in economic benefits for the small-scale farmer, but it also reduces pollution due to reduced nutrient run-off and N leaching. In this work, the feasibility of using composts as fertilizers and soil improvers has been evaluated at the field level, in barley and soft wheat crops (two successive cultivations of each crop). The applied treatments consisted of two commercial composts (compost manure and sewage sludge compost) added to the soil either alone (T1 and T3) or in combination with inorganic fertilizers (T2 and T4) and a conventional mineral fertilization (T5). Physical, physical-chemical, chemical, microbiological, and biochemical parameters were determined in the soil after each harvest. In both barley and wheat crops, soils treated with composts showed higher organic C, humic substances, and humic acid contents than the inorganically fertilized soil, as well as higher contents of water-soluble P, K, Ca, Mg, and S. In both successive crops, all treatments led to similar yields of total barley and wheat vegetal material (straw + ears) and grain, differences between treatments being not statistically significant (p ≤ 0.05). Organically treated soils showed higher microbial size and activity than inorganically treated soils as well as higher water-holding capacity. It can be concluded that quality organic composts can be used, at suitable rates, alone or in combination with inorganic fertilizers, as a good alternative to inorganic fertilization for cereal cultivation, improving soil characteristics while giving similar yield and crop quality than conventional inorganic fertilization.

28928. 题目: Altered soil microbial community composition and function in two shrub-encroached marshes with different physicochemical gradients
文章编号: N18120902
期刊: Soil Biology and Biochemistry
作者: Janet Ho, Lisa G. Chambers
更新时间: 2018-12-09
摘要: Important wetland functions, including regulating soil carbon (C) storage and water quality, are linked to biogeochemical processes mediated by soil microbes. Vegetation shifts such as shrub encroachment may alter the soil microbial community and result in changes in important biogeochemical processes, although few studies have examined this in subtropical marshes. Here, we used in-situ litter decomposition experiments, quantitative polymerase chain reaction, and laboratory assays on soil respiration, extracellular enzyme activity, and denitrification potential to determine differences in C storage and nitrogen (N) cycling between willow-encroached and non-encroached plots in two subtropical marshes (Moccasin Island and Lake Apopka, FL, USA). In both regions, encroached (willow or adjacent marsh) and non-encroached plots had distinctively different microbial communities, which were correlated with soil temperature and nutrient content. Greater enzyme activity, denitrification, and CO₂ production were observed in willow and/or adjacent marsh plots compared to control marsh plots at Moccasin Island. Conversely, lower enzyme activity, denitrification, and CO₂ production were detected in willow and/or adjacent marsh plots compared to control marsh plots at Lake Apopka. Despite differences in the response of biogeochemical processes and microbial community structure in the two study regions, in-situ decomposition rates were halved in willow litter compared to herbaceous litter in both regions, which was correlated with greater recalcitrant lignin content in willow litter. Ultimately, greater short-term litter C storage was observed in both study regions, but soil N cycling changes differed by region, potentially due to unique site characteristics such as hydroperiod and nutrient availability.

28929. 题目: Seasonal and spatial variability of sea ice and phytoplankton biomarker flux in the Chukchi Sea (western Arctic Ocean)
文章编号: N18120901
期刊: Progress in Oceanography
作者: Youcheng Bai, Marie-Alexandrine Sicre, Jianfang Chen, Vincent Klein, Haiyan Jin, Jian Ren, Hongliang Li, Bin Xue, Zhongqiang Ji, Yanpei Zhuang, Meixun Zhao
更新时间: 2018-12-09
摘要: Sediment traps were deployed at 870 m water-depth from August 2008 to September 2009 at station DM in the Chukchi Sea (western Arctic Ocean) in an area covered by sea ice in winter to determine seasonal fluxes of HBIs and phytoplankton sterols in order to improve our understanding of sea ice proxies. HBI-III fluxes and P_IIIIP₂₅ are for the first time documented in the Arctic Ocean to evaluate their significance for paleoclimate reconstructions. Highest mass fluxes were found from mid-July 2009 to September 2009 contrasting with low values during all other months (i.e., December 2008 to early July 2009). Indeed, during the winter months IP₂₅ was not detected but increased by a factor of nine over summer 2009 reflecting sea ice algae and pelagic phytoplankton production at the sea ice edge. High HBIs and low sterol fluxes at the end of summer 2008 are consistent with the complete melting of sea ice and post-bloom conditions. We found that HBI-III was more abundant in the early stage of sea ice retreat that characterizes the marginal ice zone. These sea ice biomarkers were also measured in surface sediments across a wide range of sea ice cover in the western Arctic region. Higher IP₂₅ values were found in the southeastern Chukchi Sea and decreased westwards where sea ice conditions are less severe. Stronger positive linear relationship were found between the sea ice proxy indexes P_BIP₂₅ and P_IIIIP₂₅ and spring sea ice concentrations than with IP₂₅ in agreement with earlier findings from other Arctic and sub-Arctic regions.

28930. 题目: Redox Fluctuations Control the Coupled Cycling of Iron and Carbon in Tropical Forest Soils
文章编号: N18120810
期刊: Environmental Science & Technology
作者: Amrita Bhattacharyya, Ashley N. Campbell, Malak M. Tfaily, Yang Lin, Ravi K. Kukkadapu, Whendee L. Silver, Peter S. Nico, Jennifer Pett-Ridge
更新时间: 2018-12-08
摘要: Oscillating redox conditions are a common feature of humid tropical forest soils, driven by an ample supply and dynamics of reductants, high moisture, microbial oxygen consumption, and finely textured clays that limit diffusion. However, the net result of variable soil redox regimes on iron (Fe) mineral dynamics and associated carbon (C) forms and fluxes is poorly understood in tropical soils. Using a 44-day redox incubation experiment with humid tropical forest soils from Puerto Rico, we examined patterns in Fe and C transformations under four redox regimes: static anoxic, “flux 4-day” (4d oxic, 4d anoxic), “flux 8-day” (8d oxic, 4d anoxic) and static oxic. Prolonged anoxia promoted reductive dissolution of Fe-oxides, and led to an increase in soluble Fe(II) and amorphous Fe oxide pools. Preferential dissolution of the less-crystalline Fe pool was evident immediately following a shift in bulk redox status (oxic to anoxic), and coincided with increased dissolved organic C, presumably due to acidification or direct release of organic matter (OM) from dissolving Fe(III) mineral phases. The average nominal oxidation state of water-soluble C was lowest under persistent anoxic conditions, suggesting that more reduced organic compounds were metabolically unavailable for microbial consumption under reducing conditions. Anoxic soil compounds had high H/C values (and were similar to lignin-like compounds) whereas oxic soil compounds had higher O/C values, akin to tannin- and cellulose-like components. Cumulative respiration derived from native soil organic C was highest in static oxic soils. These results show how Fe minerals and Fe–OM interactions in tropical soils are highly sensitive to variable redox effects. Shifting soil oxygen availability rapidly impacted exchanges between mineral-sorbed and aqueous C pools, increased the dissolved organic C pool under anoxic conditions implying that the periodicity of low-redox events may control the fate of C in wet tropical soils.
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28931. 题目: Study on the influence of soil microbial community on the long-term heavy metal pollution of different land use types and depth layers in mine
文章编号: N18120809
期刊: Ecotoxicology and Environmental Safety
作者: Xingqing Zhao, Jian Huang, Jin Lu, Yu Sun
更新时间: 2018-12-08
摘要: To understand the importance of the response of soil microbial communities to the stress of heavy metals around mining areas by assessing the feedback of soil ecosystems in different soil habitats, this article selected different land use types (Mining area, Dressing area, Heap mine area, Tailings area and Vegetable field) and surface soil samples of different depths (0–10 cm, 10–20 cm, 20–30 cm) as the variables related to the mining activities in the Shizishan mining area in Tongling, Anhui Province, China. Soil physicochemical properties and heavy metal concentrations of the different land use types and soil depths were compared. Illumina MiSeq. 2500 Sequencing Technology was used to analyze the abundance and structural diversity of the microbial community in soil samples. The relationship between mine soil pollution characteristics and microbial community were investigated. The results showed that soil physicochemical properties and heavy metals significantly affected the microbial community. The microbial community structure was significantly variable in vertical soil depth-layer habitats. The relative abundance (1%) of the soil microbial community at the phylum level was represented by a total of 14 phyla, where the two most dominant phyla were Proteobacteria (41.71%) and Firmicutes (20.44%). The two bacteria were positively related with Cu, Zn, Pb, and pH but negatively associated with soil organic matter (SOM), available potassium (AK), and moisture content (MC). Therefore, Proteobacteria and Firmicutes were highly resistant to heavy metals. These results increased our understanding of microbial variation and assembly pattern under different land use types in heavy metals contaminated mining soils.
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28932. 题目: Impact of biochar application on yield-scaled greenhouse gas intensity: A meta-analysis
文章编号: N18120808
期刊: Science of The Total Environment
作者: Xiang Liu, Peini Mao, Lanhai Li, Jie Ma
更新时间: 2018-12-08
摘要: The application of biochar to agricultural ecosystems is a potential solution to mitigate climate change and guarantee food security. However, the impacts of biochar on greenhouse gas emissions and crop yield are usually evaluated separately and the results are contradictory in individual studies. In this study, a meta-analysis was conducted based on data from 28 peer-reviewed studies to quantify the impacts of biochar application on greenhouse gas emissions and crop yield using yield-scaled greenhouse gas intensity (GHGI). Potential factors (experimental conditions and properties of soil and biochar) influencing the effect of biochar on yield-scaled GHGI were explored. The results showed that overall, biochar significantly reduced yield-scaled GHGI by 29%. The reductions in yield-scaled GHGI induced by biochar varied with different experimental conditions and properties of soil and biochar. However, the difference was only significant between the two cropping systems, with significantly greater reduction being observed in dry lands (−41%) than in paddy fields (−17%). Therefore, it is suggested that biochar amendment in dry lands may bring more environmental and agronomic benefits than that in paddy fields. The response of crop yield to biochar application further implied that biochar made from crop residue, biochar produced at low pyrolysis temperatures (≤400 °C), and biochar with high pH (>9.0) might contribute to save the production cost of biochar while promoting crop yield in agricultural ecosystems. Long-term field trials are required to elucidate the persistence of the impact of biochar on reducing yield-scaled GHGI and to clarify the underlying mechanisms. The balance between the price of biochar production and the benefits brought by biochar should also be focused in further studies.
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28933. 题目: Natural iron fertilization of the coastal ocean by “blackwater rivers”
文章编号: N18120807
期刊: Science of The Total Environment
作者: Regina Krachler, Rudolf Krachler, Alexander Valda, Bernhard K. Keppler
更新时间: 2018-12-08
摘要: The present study elucidates the role of natural iron fertilization of the coastal ocean by so-called “blackwater rivers”. Areas of marsh, fen, peatland, boreal forest etc. are characterized by organic-rich soils. From those soils, humic substances (humic and fulvic acids) are leached to the aquatic system resulting in river water that is low in pH and dark-brown in color. The point is that “blackwater rivers” tend to be rich in dissolved iron due to the unique chelating properties of humic and fulvic acids which bind Fe(III) and keep it in solution. We performed algal physiological (growth rate) experiments under conditions of iron deficiency with the marine unicellular phytoplankton algae Chlorella salina and Diacronema lutheri in 0.2 μm cut-off filtered mixtures of natural “blackwater river” water and synthetic seawater. Our results demonstrate that the iron naturally present in “blackwater rivers” is readily bioavailable to both marine algal species. Furthermore, the humic and fulvic acids exert an additional stimulatory effect on the marine algae. Both algae thrive much better in the presence of natural humic and fulvic acids as compared to a medium where EDTA is used as an iron-chelating agent. Our results indicate that “blackwater rivers”, in sharp contrast to other types of rivers, are excellent sources of bioavailable iron to marine phytoplankton. This natural iron fertilization may give rise to photosynthesis-driven sequestration of CO₂ from the atmosphere to the sea, as can be seen from the visualization of CO₂ surface concentrations by NASA (NASA GEOS-5 model) which shows the global sources and sinks of CO₂ localized in time and space. The results by NASA suggest that strong marine CO₂ sinks in coastal waters tend to occur close to “blackwater river” estuaries. It is thus evident that “blackwater rivers” act as important sources of a limiting nutrient (iron) to the ocean.
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28934. 题目: Water residence time (age) and flow path exert synchronous effects on annual characteristics of dissolved organic carbon in terrestrial runoff
文章编号: N18120806
期刊: Science of The Total Environment
作者: S.M. Jepsen, T.C. Harmon, S. Sadro, B. Reid, S. Chandra
更新时间: 2018-12-08
摘要: Catchment hydro-physical controls on the interannual variability of dissolved organic carbon (DOC) in terrestrial watershed runoff, important for water quality, ecosystem structure, and foodweb dynamics, are not well understood. To address this, we simulated water residence time (“age”) and flow path of terrestrial runoff and analyzed their mediating effect on relationships between annual runoff volume, DOC concentration, and DOC age. We applied this analysis to a snow-influenced watershed in California's Sierra Nevada (USA) across a range of soil types, elevations (90–4210 m), and years (1950–1999). Simulated increases in annual runoff volume were accompanied by younger ages (r² = 0.53–0.63) of DOC in quickflow, comprised of surface runoff and lateral flow through soil. Increases in annual runoff volume were also accompanied by gentler relationships between intra-annual (weekly) values of DOC concentration and runoff volume, regression-slopes of which followed a power-law relationship to annual runoff (r² = 0.12–0.92) for approximately 70% of the watershed. Simulations including dynamics of water age and soil temperature produced annual ages of quickflow DOC ranging from 1 to 70 days over all soil types and water years. Similarity of this range to an observed, 1–69 day range in half-lives of relatively labile DOC in previous studies suggests substantial interannual and spatial variability in the biodegradability of DOC in terrestrial runoff. Simulations excluding dynamics of water age and soil temperature predicted order-of-magnitude less interannual variability in age of quickflow DOC, demonstrating the important effect of interannual variability in soil-water interaction times. These findings suggest that the distribution of DOC bioprocessing along transitions between terrestrial and aquatic systems may be strongly influenced by year-to-year variability in age of water.
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28935. 题目: New insights into the effect of thermal treatment on sludge dewaterability
文章编号: N18120805
期刊: Science of The Total Environment
作者: Rongzhan Liu, Xiao Yu, Panfen Yu, Xuesong Guo, Bin Zhang, Benyi Xiao
更新时间: 2018-12-08
摘要: The changes of the sludge dewaterability in different thermal treatments and the factors influencing these changes were examined in this study. The experimental results showed that the sludge dewaterability deteriorated by the thermal pretreatment with temperature range from 20 to 170 °C, but the deterioration decreased above a certain temperature threshold (120–150 °C). The factors which affected the dewaterability of thermal-treated sludge in two temperature ranges (20–105 °C and 105–170 °C) were different. The dewaterability of thermal-treated sludge was influenced by the protein, humic acid, and polysaccharide contents of different extracellular polymeric substance fractions and the molecular distribution and fluorescence intensity of tightly bound extracellular polymeric substance in the range from 20 to 105 °C. From 105 to 170 °C, while, the thermal-treated sludge dewaterability was influenced mainly by the α-helix of protein in soluble extracellular polymeric substance. These experimental results provide a new insight into the effect of thermal treatment on sludge dewaterability, which will help guide subsequent research.
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28936. 题目: Evolution over years of structural characteristics of humic acids in Black Soil as a function of various fertilization treatments
文章编号: N18120804
期刊: Journal of Soils and Sediments
作者: Jiuming Zhang, Tingting An, Fengqin Chi, Dan Wei, Baoku Zhou, Xiaoyu Hao, Liang Jin, Jingkuan Wang
更新时间: 2018-12-08
摘要: Purpose: Humic substances are the relatively stable and recalcitrant pool of soil organic carbon in the agricultural system. Humic acid (HA) is an active part of soil humic substances. However, little information exists on how structural characteristics of HA evolved with fertilization years in Black Soil. Materials and methods: Soil samples were collected in 1997, 2002, 2008, and 2012 from the Long-term Fertilization Station of Black Soil. The methods of ¹³C-nuclear magnetic resonance spectroscopy, elemental composition analysis, and infrared spectroscopy were employed to analyze the structure of HA. Results and discussion: Long-term fertilization had no significant (P > 0.05) effect on the ratio of O and S to C in HA. The ratio of H to C in HA increased with fertilization years after the application of organic manure (M) single or combined with chemical NPK fertilizers. The ratios of aliphatic C to aromatic C, and alkyl C to O-alkyl C in soil HA increased by 7.72% and 20.3%, respectively, in MNPK and M treatments, whereas NPK treatment declined the ratio of aliphatic C to aromatic C by 2.67% compared with CK treatment. Conclusions: The HA structure tends to become aliphatic and simplified with years of organic manure combined with NPK fertilizers. To save costs, organic manure was only applied once within the period of crop rotation and was combined with NPK every year to satisfy crop demands for soil nutrients.

28937. 题目: Effect of humic acid concentration on pharmaceutically active compounds (PhACs) Rejection by direct contact membrane distillation (DCMD)
文章编号: N18120803
期刊: Separation and Purification Technology
作者: Carolina Fonseca Couto, Míriam Cristina Santos Amaral, Liséte Celina Lange, Lucilaine Valeria de Souza Santos
更新时间: 2018-12-08
摘要: In this study, a direct contact membrane distillation process was used to achieve rejection of 25 pharmaceutically active compounds (PhACs) in water. The influence of natural organic matter (NOM), a common contaminant in waters that are used for water supply, on PhACs removal was investigated. Humic acid was used as an organic model in order to represent major constituents of NOM. Results indicated that flux decline slightly increased from 0 to 8% as HA feed concentration increased from 0 to 80 mg L^-1. Flux decline was mainly associated with membrane fouling which added hydraulic resistance to the transfer of liquid water. Pore wetting was observed when HA concentration increased, which indicated changes in the hydrophobic character of the membrane. MD process showed a rejection of ≥ 99% for the 25 assessed PhACs for all HA concentration evaluated even at high permeate recovery rate (60%), whereas, 24 PhACs presented concentrations below limit detection. The retention of PhACs by MD membrane occurs predominantly by membrane rejection which is mainly governed by volatility and, to a lesser extent, by hydrophobia. The adsorption contribution to PhACs retention was low (<8%) and was significantly associated with positively charged compounds. Although the feed side of the membrane became hydrophilic due to the HA deposit, the PhACs retention by DCMD was not affected, which reinforces the robustness of the process and the ability to produce safe water. Thus, in general, DCMD is less influenced by the feed composition than nanofiltration or reverse osmosis, implicating in higher PhACs rejections.

28938. 题目: The shelf-to-basin iron shuttle in the Black Sea revisited
文章编号: N18120802
期刊: Chemical Geology
作者: W.K. Lenstra, M. Hermans, M.J.M. Séguret, R. Witbaard, T. Behrends, N. Dijkstra, N.A.G.M. van Helmond, P. Kraal, P. Laan, M.J.A. Rijkenberg, S. Severmann, A. Teacǎ, C.P. Slomp
更新时间: 2018-12-08
摘要: Continental shelf sediments are a major source of iron (Fe) for phytoplankton in surface waters. In this study, we investigate the mechanisms that control release of Fe from shelf sediments and its lateral transport (“shuttling”) in oxic and hypoxic waters on the northwestern Black Sea shelf. We find that at two coastal stations near the outflow of the Danube river high input of organic matter drives strong reductive dissolution of Fe(oxyhydr)oxides (henceforth termed Fe oxides) in surface sediments, supporting high rates of Fe release to oxygenated bottom waters (∼0.36 mmol m⁻² d⁻¹). We suggest that bioirrigation plays a key role in the release of Fe from these sediments. At four stations further offshore organic matter deposition is lower resulting in limited mobilization of Fe²⁺ in the sediment and low benthic fluxes of Fe (<0.07 mmol m⁻² d⁻¹). Lateral transport of Fe from the coastal zone towards the deep basin mostly takes place in colloidal and/or particulate form (>0.2 μm) in the lower part of the water column, likely through repeated deposition and resuspension of Fe oxides from surface sediments. Using synchrotron-based X-ray spectroscopy and sequential chemical extractions, we demonstrate that the suspended matter and surface sediments are enriched in easily reducible Fe oxides (mostly ferrihydrite) and Fe associated with clay. The mobilization of Fe in the coastal zone and subsequent lateral transport of these Fe-bearing particles results in higher ratios of Fe/Al in surface sediments at outer shelf stations (ca. 1.2 to 2 wt.% wt.%⁻¹) than at coastal stations (ca. 0.5 to 0.9 wt.% wt.%⁻¹). However, below the sediment surface layer Fe/Al ratios are similar at all stations indicating limited burial of the laterally transported Fe. Our results highlight the critical role of organic matter input, associated biological activity and riverine Fe input as drivers of Fe shuttling on continental shelves. We also show that in shelf areas where sediments receive low inputs of organic matter, physical transport controls the ultimate fate of the shuttled Fe.This article is part of a special issue entitled: “Cycles of trace elements and isotopes in the ocean - GEOTRACES and beyond” - edited by Tim M. Conway, Tristan Horner, Yves Plancherel, and Aridane G. González.

28939. 题目: Preparation of magnetic polyimide@ Mg-Fe layered double hydroxides core-shell composite for effective removal of various organic contaminants from aqueous solution
文章编号: N18120801
期刊: Chemosphere
作者: Hanjun Wu, Huali Zhang, Weijun Zhang, Xiaofang Yang, Hong Zhou, Zhiquan Pan, Dongsheng Wang
更新时间: 2018-12-08
摘要: In this work, a novel core-shell structured magnetic polyimide@layered double oxides (LDO) composites coating a porous polyimide (PI)-coated Fe₃O₄ magnetic core and layered double hydroxide (LDH) has been successfully synthesized by solve-thermal synthesis and co-precipitation process. The magnetic PI@LDO composites were characterized by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), thermogravimetry analysis (TGA) and magnetic properties analysis. The composite materials displayed core-shell structure with flower-like morphology. The magnetic PI@LDO composites were applied to remove tetracycline (TC), 2,4-dichlorophenol (2,4-DCP) and glyphosate (GP) from aqueous solution. The action pH value was ranged from 5 to 9 for TC and GP and 3 to 7 for 2,4-DCP, respectively. Cl⁻ showed a weak competitive adsorption effect to TC, 2, 4-DCP and GP. In addition, the presence of humic acid (HA) could slightly reduce the adsorption capacity of magnetic PI@LDO composites. The adsorption process could be well described by pseudo-second-order model for TC and GP, while pseudo-first-order model for 2,4-DCP. The experimental data of TC and 2,4-DCP could be fitted better with Freundlich model, while that of GP were fitted better with Langmuir model. The adsorptions of TC, 2,4-DCP and GP were both spontaneous and endothermic. The adsorption capacity decreased slightly after adsorption-desorption cycles repeated five times. This study demonstrated that magnetic PI@LDO exhibited great potential to be a mild and cost-effective adsorbent for the removal of various organic contaminants from wastewater.
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28940. 题目: Importance of a Coastal Artificial Lake in Methylmercury Production: A Case Study of Lake Changpo, Korea
文章编号: N18120709
期刊: Ocean Science Journal
作者: Sampa Rani Kundu, Eunhee Kim, Seunghee Han, Byeong-Gweon Lee
更新时间: 2018-12-07
摘要: Lake Changpo (LC) is an artificial freshwater lake surrounded by wetlands and farmlands, inundated with water during the wet season, on the southwest coast of Korea. To investigate the temporal and spatial distribution of total mercury (THg) and methylmercury (MeHg) in LC and adjacent Cheonggye Bay (CB), water and sediment samples were collected five times from August 2009 to August 2010. In addition, fish samples were collected to examine Hg levels. The THg concentration in the unfiltered water of LC ranged from 1.6 to 5.0 ng/L and had a positive relationship with total suspended solids (TSS). This positive relation indicates that TSS is an important source of THg in LC. The MeHg levels were highest during August and ranged from 0.03 to 0.19 ng/L in unfiltered water and from 0.01 to 0.10 ng/L in filtered water. Both the THg and MeHg levels in the sediments were significantly correlated with the organic matter content of the sediments. Overlapping of the spatial and temporal distribution patterns of MeHg and %MeHg between the water column and sediments suggests that production and diffusion of MeHg from the sediment, particularly during warm summer, was the primary source of MeHg in the water column. In addition, higher THg and MeHg concentrations were found in catfish, a bottom-dweller fish. Thus, the higher THg and MeHg concentrations in LC compared to CB demonstrate that artificial lakes could be a significant site for Hg methylation and an additional source of MeHg to coastal seas.