1. 题目: Organic matter and nutrient removal in tidal flow-based microbial fuel cell constructed wetlands: Media and flood-dry period ratio
期刊: Chemical Engineering Journal
作者: Tanveer Saeed, Md Jihad Miah
摘要: This study assessed the integrated impact of tidal flow, microbial fuel cell (MFC), flood (F)-dry (D) period ratio, and media on organic matter, nutrient removal pathways in subsurface flow constructed wetlands that received municipal wastewater. The tidal flow-based MFC constructed wetlands were filled with organic (biochar, coal, jute fiber), waste (slag), construction materials (concrete, brick), and planted with Phragmite australis or Chrysopogon zizanioides (i.e., Vetiver). The tidal flow-based MFC wetlands were operated under sequential flood-dry periods; three F:D ratio values (i.e., 8hrs: 16hrs; 16 hrs: 8 hrs; 24 hrs: 0 hrs) were employed within three operational periods. Mean input chemical oxygen demand (COD), nitrogen (N), and phosphorus (P) load across the tidal flow-based MFC wetlands ranged between 45 and 1130, 6–71, and 0.1–25 g/m2d, respectively; removal percentages ranged between 75 and 100, 57–86, and 80–100%, respectively. Nutrient accumulation percentage in wetland plants was <7% with respect to total removal. Electrochemically active-inactive microbial degradation and media-based adsorption supported nutrient, organics removals. Flood-dry period variation influenced N removal kinetics; organics and P removals were stable throughout the experimental run. Maximum power production rates (within the experimental systems) ranged between 63 and 982 mW/m2. Tidal flow-based MFC wetlands filled with organic media achieved high N removal and power production than waste, construction materials based systems.
2. 题目: Soil organic matter stability and microbial community in relation to different plant cover: A focus on forests characterizing Mediterranean area
期刊: Applied Soil Ecology
作者: Enrica Picariello, Daniela Baldantoni, Francesco Izzo, Alessio Langella, Flavia De Nicola
摘要: In this study, soil organic matter (SOM), as well as the structure and function of soil microbial communities in three forest systems (holm oak, black pine and beech) widely distributed in the Mediterranean area, were analyzed to assess the effects of different canopies on microbial community. Fourier transform infrared (FTIR) spectroscopy, combined with Thermal analyses, was used to characterize SOM, in order to obtain information on its quality and stability. Soil microbial communities were analyzed through the phospholipid fatty acid (PLFA) profile, ergosterol, hydrolase, laccase and peroxidase activities, fungal and bacterial growth. Soil under pine and beech contained more recalcitrant SOM, in respect to the soil under holm oak, characterized by more labile SOM. The PLFA analysis showed a different structure of the edaphic microbial community of the three forests. Soils under pine was characterized by the greatest abundance of fungal biomass and high peroxidase activity likely in relation to the presence in this soil of more recalcitrant compounds, mainly decomposed by fungi. Overall, pine and beech forests represent important carbon sinks with larger amounts of recalcitrant organic matter in their soils.
3. 题目: Thermal stability of soil organic carbon after long-term manure application across land uses and tillage systems in an oxisol
作者: Matheus Sampaio C. Barreto, Marlon Ramlogan, Dener Marcio S. Oliveira, Ernst Eduard J. Verburg, Evert J. Elzinga, Ashaki A. Rouff, Martin Jemo, Luís Reynaldo F. Alleoni
摘要: The pool of carbon (C) present in soil systems is larger than the amount of organic C stored in living biomass and the atmosphere. Soil degradation has increased soil C emissions at the expense of C accumulation. Climate-smart management practices may be adapted to increase C sequestration as soil organic carbon (SOC). To avoid the SOC loss, different strategies have been applied, including no-tillage and organic fertilizer. Here, we investigated thermal stability of SOC after long-term manure application across land uses and tillage systems in weathered soils of Brazil. We chose five commercial areas with different land uses: pasture with swine manure (SM) application (PA + SM), conventional tillage (CT) with SM application (CT + SM), natural vegetation (NV), no-tillage with SM application (NT + SM), and no-tillage (NT). Thermal analysis revealed that SOC oxidation and CO2 emission started around 240 °C, close to gibbsite and goethite structural collapse, suggesting preferential adsorption of SOC onto these minerals. Approximately 50% of SOC for all sites was oxidizable at lower temperature (~315 °C) which suggests the prevalence of polysaccharides, decarboxylation of acidic groups and dehydration of hydroxylate aliphatic structures, regardless of land-use. The energy content of SOC for NV (6.5) and PA + SM (10.6) were in average, 46% lower than other treatments which suggest a higher necromass contribution to SOC in these systems. However, the higher energy content in CT + SM (14.9), NT + SM (16.5), and NT (15.8), suggests a higher contribution of plant-derived compounds in SOC. Our results showed that SM application on pastureland reached similar SOC accumulation to NV and increment of ~33% when applied to no-till system. We conclude that SM could a drive higher C accumulation and stabilization if preferentially associated to soil conservative system.
4. 题目: Changes of carbon to nitrogen ratio in particulate organic matter in the marine mesopelagic zone: A case from the South China Sea
期刊: Marine Chemistry
作者: Zhongsheng Xu, Bin Wang, Yiming Luo, Hongliang Li, Jingjing Zhang, Haiyan Jin, Jianfang Chen
摘要: In this study, a model of remineralization patterns was developed to explore the particulate organic matters (POM) decomposition process among marine mesopelagic zone (200 to 1000 m) using data from the South China Sea. The results suggest that three high C/N remineralization patterns are identified at 200 to 400 m, 600 to 700 m and 900 to 1000 m, and two low C/N remineralization patterns are found at 400 to 600 m and 700 to 900 m. These findings indicate three increasing trends and two decreasing trends of C/N ratios in POM, which are further confirmed by measured C/N data in POM from the global ocean. Only the exposed POM has the chance to experience the selective remineralization process, thus the C/N ratios in POM of the remained particles are closely related to selective preservation of specific bio-macromolecules, aggregates, zooplankton community structure at different depths and the microbial loop.
5. 题目: Role of Extracellular Polymeric Substances and Enhanced Performance for Biological Removal of Carbonaceous Organic Matters and Ammonia from Wastewater with High Salinity and Low Nutrient Concentrations
期刊: Bioresource Technology
作者: Wenchang Tang, Mengjie Wu, Wei Lou, Chunping Yang
摘要: The role of EPS in the removal of carbonaceous organic matters and NH4+-N in simulated mariculture wastewater was examined at salinity of 0-3.5% in a multi-soil-layering bioreactor. Results showed that at 3.5% of salinity, the total activity of dehydrogenases (which were used to decompose carbonaceous organic matters) could be promoted by 13.2%-33.8% by EPS, increasing the removal rates of COD and NH4+-N by 13.2%-33.8% and 27.8%-42.1%, respectively. Besides, the activity of amylase in EPS was enhanced by 79.8%. However, reactions of some key enzymes such as acetate kinase and Na+K+-ATPase would not be accelerated by EPS, resulting in an inhibition of 44.3%-57.7% on energy gaining from ATP, and further inducing cytotoxicity. It was found that the glycolysis efficiency was promoted by 4.12%-59.3% in the presence of EPS, and glycolysis could also occur in EPS. Additionally, tyrosine was the main component in EPS to balance osmotic pressure.
6. 题目: The effect of organic solvent washing on the structure of hydrochar-based dissolved organic matters and its potential environmental toxicity
期刊: Environmental Science and Pollution Research
作者: Guangping Fan, Fei Tong, Weiguo Zhang, Gaoling Shi, Wei Chen, Lizhu Liu, Jiangye Li, Zhenhua Zhang, Yan Gao
摘要: With the increased interest in the practical use of hydrochar, concerns about the possible environmental biotoxicity of hydrochar and its released dissolved organic matters (DOM) have grown. As a common method for removing bio-oil on the surface of hydrochar, the effect of organic solvent washing on the properties of hydrochar released DOM remains unclear. In this study, we made a comprehensive comparison of hydrochar properties and molecule structure as well as biotoxicity of DOM released from HC (raw hydrochar) and THC (hydrochar washed by tetrahydrofuran). The results indicated that the mass loss of hydrochar was obvious after tetrahydrofuran (THF) washing, and a decline of H/C atomic ratio and increase of N/C and O/C atomic ratios was observed based on Van Krevelen (VK) diagram. This result was further confirmed by FTIR, 13C NMR, and XPS results. Meanwhile, the molecule structure of DOM was shifted to lower molecule weight with higher O-contain compounds after THF extraction due to the demethanation process. However, the biotoxicity experiments indicated that both extracted DOM had no significant impact on germination rate of wheat, and HC-treated sample even exhibited growth superiority. Nevertheless, potential toxicity was observed with the increase of the activity of antioxidant enzymes, and THF washing aggravated the potential oxidative damage through increasing the aromaticity of DOM. Such understanding highlights the importance of evaluating hydrochar and its released DOM before applications, so as to reduce the potential environment biotoxicity.
7. 题目: Fluorescence moieties as a surrogate for residual chlorine in three drinking water networks
期刊: Chemical Engineering Journal
作者: Tahir Maqbool, Jiaxing Zhang, Yanling Qin, Muhammad Bilal Asif, Quang Viet Ly, Zhenghua Zhang
摘要: Several factors play a role in chlorine consumption in drinking water networks such as microbial contamination and dissolved organic matter (DOM). This study investigated the simultaneous impacts of seasonal variations on chlorine consumption and DOM composition for a year-long period in three different full-scale water distribution networks in a southern city of China. Efforts were made to determine the association between different fluorescence moieties in DOM of finished water and chlorine consumption through excitation-emission matrix coupled with parallel factor analysis (EEM-PARAFAC). The chlorine consumption was also found to be directly related to N-Nitrosodimethylamine (NDMA) and NDMA-formation potential (NDMA-FP), presenting consequence of excess residual chlorine. The wet season with high rainfall showed elevated consumption of chlorine on the opposite of dry season. During wet season, humic-like component in finished water was dominant than protein-like features and its abundance decreased in dry season. Results proved that chlorine consumption was season dependent and highly influenced by DOM composition in the finished water. Unlike the bulk quality parameters and protein-like component, fluorescence moieties related to humic substances acted as a surrogate for the chlorine consumption. Based on humic-like component, a single excitation based fluorescence peak, I245/410 or I335/410, was also extracted from EEMs of finished water samples and validated on different water distribution networks. These two single peaks well-explained the trends of residual chlorine and have the potential for on-line monitoring and portable purposes. This field-based study demonstrated application of fluorescence spectroscopy in designing chlorine dose to obtain optimal residual chlorine at consumer's tap.
8. 题目: Preparation of graphite-like biochars derived from straw and newspaper based on ball-milling and TEMPO-mediated oxidation and their supersorption performances to imidacloprid and sulfadiazine
期刊: Chemical Engineering Journal
作者: Peng Zhang, Xinhua Wang, Bing Xue, Peng Huang, Yueli Hao, Jingchun Tang, Snežana P. Maletić, Srđan D. Rončević, Hongwen Sun
摘要: In this study, graphite-like biochars were successively prepared by pyrolyzing modified newspaper and maize straw with ball-milling and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)- mediated oxidation at a pyrolysis temperature of 900 °C and their physico-chemical properties and adsorption performances towards imidacloprid (IMI) and sulfadiazine (SUL) in aqueous solution were all explored. The results showed that the successive modification by ball-milling and TEMPO-mediated oxidation completely open the fibers of the newspaper and porous stereoscopic structures of the maize straw. The obtained graphite-like biochars contained planar structures and abundant O-containing functional groups, and exhibited a great degree of graphitization and specific surface areas reaching up to 871.5 and 1065 m2/g, making them super adsorbents. Furthermore, hydrophobic partitioning provided a limited contribution to the sorption on biochars for IMI and SUL as revealed by dual-mode model fitting. The graphite-like biochars adsorbed IMI and SUL, mainly through pore-filling, H-bonding, cation/p/π-π EDA interactions, and electrostatic interactions and cation-π EDA interactions further enhanced the sorption of cationic IMI. Additionally, the adsorption efficiency of biochars pretreated with ball-milling and TEMPO-mediated oxidation for IMI and SUL was>85%, even after five consecutive recycling process. Thus, this study provides excellent graphite-like biochar adsorbents pretreated with a combined ball-milling and oxidation modification method, making them efficient for removing hydrophilic pesticides and antibiotics from polluted water.
9. 题目: Climatic and anthropogenic driving forces of the nitrogen cycling in a subtropical river basin
期刊: Environmental Research
作者: Hao Jiang, Qianqian Zhang, Wenjing Liu, Jiangyi Zhang, Tong Zhao, Zhifang Xu
摘要: To date, basin-scale understanding of nitrogen (N) cycling is lacking, which undermines riverine N pollution control efforts. Applying a multiple-isotopic approach, this study provided insights into the impacts of climate and anthropogenic activities on the N cycling at a basin scale. The isotopic compositions of the river water were regulated by a simple mixing process in winter, while unconservative processes (nitrification and denitrification) occurred in warm seasons. Denitrification dominated the N transformations in summer, while coupled nitrification-denitrification in soils after fertilization was responsible for the isotopic fractionations in spring and autumn. While at least 58.7% of the nitrate (NO3−) was removed from the basin, the NO3− loadings in the river remained high, suggesting that the ecosystem services could not balance the anthropogenic pollution. After correcting the isotopic fractionations, the sources of the riverine NO3− were quantified by a Markov chain Monte Carlo isotope mixing model. The contributions of point sources versus non-point sources changed dynamically with the precipitation and fertilization patterns. In summer and autumn, the soil organic N and chemical fertilizer dominated the riverine NO3−, with total contributions of 75.9% and 74.6%, respectively. The contributions from sewage and manure significantly increased during spring (47.9%) and winter (50.2%). Overall, the annual NO3− fluxes were from SON (28.7%), CF (28.1%), DS (18.2%), MA (23.9%), and AP (1.1%). In addition, we presented the large uncertainties in source apportionment that arose from the ignorance of isotope fractionations, highlighting the importance of considering the effect of isotopic fractionations in N source apportionment studies.
10. 题目: Effect of sodium persulfate treatment on the physicochemical properties and catalytic activity of biochar prepared from spent malt rootlets
期刊: Journal of Environmental Chemical Engineering
作者: Paraskevi Ntzoufra, John Vakros, Zacharias Frontistis, Sotirios Tsatsos, Georgios Kyriakou, Stella Kennou, Ioannis D. Manariotis, Dionissios Mantzavinos
摘要: Biochar catalysts exhibit significant activity and stability, for the activation of sodium persulfate (SPS) and consequently the oxidation of organic contaminants. In this study, the influence of SPS on the physicochemical characteristics and catalytic activity of biochar was determined. Following intense treatment with high SPS concentration at high temperature the biochar samples were characterized and tested for the degradation of sulfamethoxazole (SMX) in water matrices. The SPS treatment was found to alter significantly the biochar's surface by dissolving the inorganic deposits and part of the organic phase. SPS was also found to increase the specific surface area and to change the acidity / basicity of the biochar. Lengthy treatments reduce the catalytic activity, an effect attributed to the oxidation of surface carbon groups, while shorter treatments result in higher activity due to the high specific surface area, enrichment of the surface with carbon groups and limited oxidation of the biochar.
11. 题目: Comparative study on characteristics and mechanism of phosphate adsorption on Mg/Al modified biochar
期刊: Journal of Environmental Chemical Engineering
作者: Yu Deng, Min Li, Zhan Zhang, Qiao Liu, Kele Jiang, Jingjie Tian, Ying Zhang, Fuquan Ni
摘要: Biochar-based adsorption process, for its environmental and economic benefits, has recently become a new method of pollution control. Nevertheless, biochar generally has a negatively charged surface that limits its binding affinity toward phosphate anions. In order to address this problem, Mg/Al-modified biochars derived from corn-cob (based on the Mg (Al): biomass = 5, 10, 15 and 20 wt%) are synthesized to remove phosphate from water. The physicochemical properties of biochars such as elemental composition, surface area, morphology, crystalline structure and surface functional groups are characterized. Batch adsorption experiments are performed to determine the adsorption performance and optimal adsorption conditions of phosphate on biochar. It is found that the structural properties and surface morphology of biochar modified by Mg/Al are greatly improved, and its phosphate adsorption capacity also significantly increases, so the optimal Mg/Al content is determined to be 20%. The theoretical maximum phosphate adsorption capacities of 20%Mg-BC and 20%Al-BC are 56.12 mg/g and 44.79 mg/g, respectively. Compared with 20%Al-BC, 20%Mg-BC has more stable removal efficiency as well as a wider pH range for phosphate removal. Spectroscopic solid-phase analyses demonstrate that the adsorption mechanisms mainly include electrostatic attraction, the formation of complexes, cationic bridging and chemical co-precipitation. The adsorption mechanisms, however, are different between Mg-BC and Al-BC. The results indicate that Mg/Al-modified biochar is an environmental friendly material for the recovery of eutrophic water.
12. 题目: Dynamics of methane emission and archaeal microbial community in paddy soil amended with different types of biochar
期刊: Applied Soil Ecology
作者: Leiling Fu, Yue Lu, Lin Tang, Yingju Hu, Qingqing Xie, Linrui Zhong, Changzheng Fan, Qian Liu, Shoujuan Zhang
摘要: Biochar, as a valuable and eco-friendly material generated from greenwaste, has a potential to mitigate CH4 emission in rice paddy soil. However, the response of methanogenesis and associated archaeal community in paddy soil to biochar amendment remains controversial. In this study, we explored the effect of three different biochars (derived from rice straw, orange peel or bamboo powder, respectively) on CH4 emission and associated archaeal microbial community in paddy soil of southern China within 90 days of anaerobic incubation. Results showed that biochar amendment overall inhibited CH4 emission in paddy soil. Significant decrease of α-diversity of archaeal community was observed in all samples in the end of incubation as revealed by 16S rRNA gene sequencing, and the addition of biochars mitigated the loss of archaeal biodiversity in paddy soil. Incubation time was found to be the major driver for the succession of archaeal community. Besides, Methanosaeta, Methanocella, Methanobacterium and Methanosarcina were mainly responsible for CH4 production. In addition, biochars had no significant effect on altering relative abundance of methanogens. Overall, our study demonstrated that the addition of three different types of biochar reduced methane emission and total archaeal diversity, while caused no significant change in methanogenic communities in paddy soil.
13. 题目: Manure-based biochar decreases heterotrophic respiration and increases gross nitrification rates in rhizosphere soil
期刊: Soil Biology and Biochemistry
作者: Prem Pokharel, Le Qi, Scott X. Chang
摘要: This study hypothesized that pyrolyzed manure pellet (biochar) reduces heterotrophic respiration and N2O emissions from wheat (Triticum aestivum L.) rhizosphere soil by affecting net and gross nitrogen (N) transformation rates and the effects differ between rhizosphere and bulk soils. The biochar significantly decreased heterotrophic respiration but not N2O emissions, while unpyrolyzed manure pellets (feedstock) increased both of them, in both the rhizosphere and bulk soils. The biochar increased gross nitrification rate by 32.9% in the rhizosphere but decreased it by 19.4% in the bulk soil while the feedstock increased gross N transformation (mineralization and nitrification) rates in both soil zones. The biochar decreased the % recovery of 15NH4+ in the NH4+-N pool in the rhizosphere but increased it in the bulk soil, as a result of biochar's contrasting effects on gross nitrification rates in the respective soil zones. It can be concluded that biochar had similar effects on heterotrophic respiration and N2O emissions but had contrasting effects on gross nitrification rates between rhizosphere and bulk soils, highlighting the importance of gross N transformation processes in understanding the rhizosphere-biochar interactions.
14. 题目: What are the products of enzymatic cleavage of organic N?
期刊: Soil Biology and Biochemistry
作者: Charles Warren
摘要: Nitrogen commonly limits productivity, yet most soils contain a substantial pool of N in organic forms that are too large for rapid direct uptake. These larger forms of organic N generally become available only after they have been cleaved into smaller units by extracellular enzymes. Enzymatic cleavage of organic N is often equated with complete depolymerisation of protein to amino acids, yet it is likely that small peptides are also products of depolymerisation and there is a suite of other N-containing compounds that could be produced by enzymatic cleavage. The aims of this study were to a) characterize in a range of soils the pools of organic N that represent the substrates and products of enzymatic cleavage, viz., hydrolysable N and dissolved organic nitrogen (DON); b) develop a workflow for the untargeted identification and quantification of the products of enzymatic cleavage of organic N, and c) build a picture of the quantitative significance of different compounds for N cycling by determining their rates of production by enzymatic cleavage. Among a range of soils the pool of < 3 kDa DON was quantitatively dominated by protein amino acids (69% of < 3 kDa DON in H2O and K2SO4 extracts) and small peptides (15% of DON in H2O extracts and 26% in K2SO4 extracts). Only a small fraction of total hydrolysable N and DON was accounted for by compounds that originate from microbial cell walls (viz. hexosamines, muramic acid, diaminopimelic acid). To determine the products of enzymatic cleavage, soils were vacuum infiltrated with chloroform gas for five days to halt microbial metabolism, then enzymatic cleavage was assessed by incubating with water + casein (potential protein depolymerisation) or water alone (enzymatic cleavage of endogenous organic matter). Reaction products were identified and quantified using mass spectrometry, with rates of production determined from the increase between 30 minutes and 24 hours of incubation. When extra substrate was added in the form of casein, small peptides were the primary products of depolymerisation, suggesting that assays of potential protease should be interpreted in terms of partial depolymerisation to peptides. Enzymatic cleavage of endogenous organic matter resulted in production of small peptides (generally < 500 Da) and amino acids in approximately equal amounts. Hexosamines, muramic acid, and diaminopimelic acid accounted for less than 1% of the products of enzymatic cleavage, while at least 2% was accounted for by nucleobases + nucleosides and headgroups of membrane lipids. We conclude that the workflow described here coupling chloroform gas infiltration with untargeted mass spectrometry of reaction products can reveal the diversity of compounds produced during enzymatic cleavage of organic matter. Our analysis confirmed that amino acids and peptides quantitatively dominate depolymerisation, and that decomposition of nucleic acids and lipids may supply significant amounts of N and ought to be the subject of further study.
15. 题目: Is soil organic carbon underestimated in the largest mangrove forest ecosystems? Evidence from the Bangladesh Sundarbans
作者: Md. Saidur Rahman, Daniel N.M. Donoghue, Louise J. Bracken
摘要: Globally, mangroves sequester a large amount of carbon into the sediments, although spatial heterogeneity exists owing to a wide variety of local, regional, and global controls. Rapid environmental and climate change, including increasing sea-level rise, global warming, reduced upstream discharge and anthropogenic activities, are predicted to increase salinity in the mangroves, especially in the Bangladesh Sundarbans, thereby disrupting this blue carbon reservoir. Nevertheless, it remains unclear how salinity affects the belowground soil carbon despite the recognised effect on above ground productivity. To address this gap, research was undertaken in the Bangladesh Sundarbans to compare total soil organic carbon (SOC) across three salinity zones and to explore any potential predictive relationships with other physical, chemical properties and vegetation characteristics. Total SOC was significantly higher in the oligohaline zone (74.8 ± 14.9 Mg ha−1), followed by the mesohaline (59.3 ± 15.8 Mg ha−1), and polyhaline zone (48.3 ± 10.3 Mg ha−1) (ANOVA, F2, 500 = 118.9, p < 0.001). At all sites, the topmost 10 cm of soil contained higher SOC density than the bottom depths (ANOVA, F3, 500 = 30.1, p < 0.001). On average, Bruguiera sp. stand holds the maximum SOC measured, followed by two pioneer species Sonneratia apetala and Avicennia sp. Multiple regression results indicated that soil salinity, organic C:N and tree diameter were the best predictor for the variability of the SOC in the Sundarbans (R2 = 0.62). Despite lower carbon in the soil, the study highlights that the conservation priorities and low deforestation rate have led to less CO2 emissions than most sediment carbon-rich mangroves in the world. The study also emphasised the importance of spatial conservation planning to safeguard the soil carbon-rich zones in the Bangladesh Sundarbans from anthropogenic tourism and development activities to support climate change adaptation and mitigation strategies.
16. 题目: Amino acids and amino sugars as indicators of the source and degradation state of sedimentary organic matter
期刊: Marine Chemistry
作者: Jin-E Wei, Yan Chen, Jian Wang, Shi-Bo Yan, Hong-Hai Zhang, Gui-Peng Yang
摘要: Amino acids (AAs) and amino sugars (ASs), compounds ubiquitous to living organisms, can provide information regarding degradation states and bacterial contributions to sedimentary organic matter (SOM). However, very few studies have utilized the combination of AAs and ASs as a proxy to assess the influence of bacterial degradation on SOM in the Yellow Sea (YS). In this study, surface sediments from the YS were analyzed for AAs, ASs, total organic carbon (TOC), total nitrogen (TN), stable carbon isotope (δ13C), and grain size. The concentrations of AAs and ASs ranged from 3.29 to 26.65 μmol g−1 and from 0.50 to 9.11 μmol g−1, respectively, and together contributed 13.1% to TOC and 27.5% to TN. The concentrations of AAs and ASs were both positively correlated with the relative abundance of clay (<4 μm) (R2 = 0.73 and 0.79, respectively, p < 0.01), suggesting that hydrodynamic sorting influenced the distribution of SOM in the study area. Comparisons of the degradation indices (TOC normalized yields of AAs and ratio of AAs to ASs) indicated that the SOM in the South Yellow Sea (SYS) was more degraded than that in the North Yellow Sea (NYS). Variations in the glycine/serine and glucosamine/galactosamine ratios reflected a transition from fresh phytoplankton sourced OM to bacterial OM. Based on the yields of muramic acid (Mur), the bacterial organic matter (OM) contributed 17 ± 13% and 26 ± 19% to TOC and TN, respectively. High ratios of glucosamine to Mur (GlcN/Mur) indicated that the fraction of bacterial debris in the SYS was larger than that in the NYS. This study demonstrated the importance of bacteria in regulating the source and fate of SOM in the YS.
17. 题目: Adsorption of emerging contaminants from water and wastewater by modified biochar: A review
期刊: Environmental Pollution
作者: Ning Cheng, Bing Wang, Pan Wu, Xinqing Lee, Ying Xing, Miao Chen, Bin Gao
摘要: Emerging contaminants (ECs), a group of relatively low-concentration but high-toxicity pollutants in the environment, have attracted widespread attention in recent years. These trace pollutants can be enriched in organisms and finally transferred to human bodies, posing a potential hazard to public health. Biochar, a low-cost and high-efficiency adsorbent, has been used to treat ECs in water. However, due to certain limitations of pristine biochar, such as poor adsorption capacity, narrow adsorption range, and other shortcomings, it is necessary to modify biochar to improve its applications in water treatment for ECs. Currently, there are a lot of reports on the removal of ECs from water by modified biochar. These studies explored different modification methods to functionalize biochar with various physicochemical properties, which resulted in distinct adsorption effects, behaviors and mechanisms of modified biochar on different ECs. There is a need to systematically review and digest the knowledge on the adsorption of ECs on modified biochar. In this review, recent biochar modification methods used in ECs removal are firstly summarized, and the adsorption performance and mechanisms of modified biochar on typical ECs are then systematically reviewed. Finally, the main research directions and trends, as well as recommendations and suggestions for future development are pointed out.
18. 题目: Improved simulations of global black carbon distributions by modifying wet scavenging processes in convective and mixed‐phase clouds
期刊: Journal of Geophysical Research: Atmospheres
作者: Mingxu Liu, Hitoshi Matsui
摘要: In‐cloud wet scavenging dominates the wet removal of aerosols in the atmosphere, but is not well represented in climate models. Aircraft measurements of black carbon (BC) concentrations suggest that models commonly overestimate BC concentrations in the upper troposphere of the tropics by more than one order of magnitude but underestimate BC burdens in polar latitudes. In this study, we improved the in‐cloud wet scavenging parameterizations for convective clouds and mixed‐phase clouds to better characterize BC abundances in the remote atmosphere (remote oceans and polar regions) with a global model, CAM5‐ATRAS2. The modified wet scavenging processes in the model achieved a more realistic simulation of BC concentrations over both the tropics and the Arctic. The new, unified scheme for vertical transport and wet removal during deep convection generally reproduced the observed low mixing ratios (about 0.1 ng kg−1) of BC in the middle and upper troposphere over the tropics, and the Wegener–Bergeron–Findeisen process (WBF) lowered the wet removal efficiency of BC from mixed‐phase clouds and consequently increased BC burdens in the Arctic by about a factor of 2. The BC direct radiative forcings increased by 20% globally (from 0.26 to 0.31 W m−2), and more importantly by a factor of 2 in the Arctic (from 0.09 to 0.18 W m−2). Our results indicated that good agreement between modeled and observed BC concentrations could be obtained in the remote atmosphere without requiring the relatively short global BC lifetime (∼4 days) suggested by previous studies. This article is protected by copyright. All rights reserved.
19. 题目: Biological cohesion as the architect of bed movement under wave action
期刊: Geophysical Research Letters
作者: Xindi Chen, Changkuan Zhang, Ian Townend, David M. Paterson, Zheng Gong, Qin Jiang, Qian Feng, Xiping Yu
摘要: Cohesive extracellular polymeric substances (EPS) generated by microorganisms abundant on Earth are regarded as bed stabilizers increasing the erosion threshold in sedimentary systems. However, most observations of this phenomenon have been taken under steady flow conditions. In contrast, we present how EPS affect the bed movement under wave action, showing a destabilization of the system. We demonstrate a complex behavior of the bio‐sedimentary deposits, which encompasses liquefaction, mass motion, varying bed formations and erosion, depending on the amount of EPS present. Small quantities of EPS induce higher mobility of the sediments, liquefying an otherwise stable bed. Bed with larger quantities of EPS undergoes a synchronized mechanical oscillation. Our analysis clarifies how biological cohesion can potentially put coastal wetlands at risk by increasing their vulnerability to waves. These findings lead to a revised understanding of the different roles played by microbial life, and their importance as mediators of seabed mobility.
20. 题目: Sensitivity of 21 st century ocean carbon export flux projections to the choice of export depth horizon
期刊: Global Biogeochemical Cycles
作者: Hilary I. Palevsky, Scott C. Doney
摘要: Global Earth system model simulations of ocean carbon export flux are commonly interpreted only at a fixed depth horizon of 100‐m, despite the fact that the maximum annual mixed layer depth (MLDmax) is a more appropriate depth horizon to evaluate export‐driven carbon sequestration. We compare particulate organic carbon (POC) flux and export efficiency (e‐ratio) evaluated at both the MLDmax and 100‐m depth horizons, simulated for the 21st century (2005‐2100) under the RCP8.5 climate change scenario with the Biogeochemical Elemental Cycle model embedded in the Community Earth System Model (CESM1‐BEC). These two depth horizon choices produce differing baseline global rates and spatial patterns of POC flux and e‐ratio, with the greatest discrepancies found in regions with deep winter mixing. Over the 21st century, enhanced stratification reduces the depth of MLDmax, with the most pronounced reductions in regions that currently experience the deepest winter mixing. Simulated global mean decreases in POC flux and in e‐ratio over the 21st century are similar for both depth horizons (8‐9% for POC flux and 4‐6% for e‐ratio), yet the spatial patterns of change are quite different. The model simulates less pronounced decreases and even increases in POC flux and e‐ratio in deep winter mixing regions when evaluated at MLDmax, since enhanced stratification over the 21st century shoals the depth of this horizon. The differing spatial patterns of change across these two depth horizons demonstrate the importance of including multiple export depth horizons in observational and modeling efforts to monitor and predict potential future changes to export.