论文检索

总访问量：5926560次

总访客量：428866人

所有论文

26081. 题目: ZnCl₂ modified biochar derived from aerobic granular sludge for developed microporosity and enhanced adsorption to tetracycline
文章编号: N19111001
期刊: Bioresource Technology
作者: Lilong Yan, Yue Liu, Yudan Zhang, Shuang Liu, Caixu Wang, Wanting Chen, Cong Liu, Zhonglin Chen, Ying Zhang
更新时间: 2019-11-10
摘要: In this study, biochar derived from aerobic granular sludge was modified by ZnCl₂ (Zn-BC) to improve the adsorption performance of tetracycline (TC). The surface area, pores, and functional groups of Zn-BC were characterized by scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) surface area, Fourier transform infrared (FTIR) spectroscopy and X-ray diffraction (XRD) and the effects of initial pH, TC concentration, and temperature on TC adsorption performance were analyzed. At the same time, the adsorption kinetics, isotherms, thermodynamics and diffusion models were studied. The results showed that the BET surface area and micropore volume of Zn-BC were 852.41 m²·g^-1 and 0.086 cm³·g^-1, respectively. The maximum adsorption performance of TC was 93.44 mg·g^-1, and it was less influenced by pH. The adsorption of TC on Zn-BC agreed well with the pseudo-second-order model and the Langmuir isotherm. The thermodynamic parameters indicated that the adsorption process was a spontaneously endothermic reaction.
图文摘要:

26082. 题目: Humic Acid Can Enhance the Mineralization of Phenanthrene Sorbed on Biochars
文章编号: N19110920
期刊: Environmental Science & Technology
作者: Meng Zhang, Xiaofang Shen, Haiyun Zhang, David Werner, Bin Wang, Yu Yang, Shu Tao, Xilong Wang
更新时间: 2019-11-09
摘要: Biodegradation of hydrophobic organic contaminants by bacteria has been widely studied, but how dissolved organic matter (DOM) may affect their removal if accumulated on biochars is poorly understood. To address this knowledge gap, microbial mineralization of phenanthrene (PHE) spiked on various biochars by Mycobacterium vanbaalenii PYR-1 in the presence of humic acid (HA, a model DOM) at two concentrations was investigated. Our findings showed that HA greatly increased the rate and extent of PHE mineralization. This could be attributed to enhanced PHE desorption by HA, which facilitated access to it by bacteria in the aqueous phase. Furthermore, the high HA affinity for PHE facilitated PHE flow toward the bacterial cells with HA acting as a carrier in the aqueous phase. The mineralization enhancement of PHE by HA within 480 h was negatively influenced by the aromatic carbon contents and micropore volumes in biochars. This shows the importance of the physicochemical properties of biochars in altering the HA effect. Results of this study provide novel information on how to achieve complete removal of PHE accumulated on biochars with a strong sorption affinity for it, using a microbial technique and natural DOM.

26083. 题目: Is Superoxide-Mediated Fe(III) Reduction Important in Sunlit Surface Waters?
文章编号: N19110919
期刊: Environmental Science & Technology
作者: Guowei Xing, Shikha Garg, T. David Waite
更新时间: 2019-11-09
摘要: Two major pathways are reported to account for photochemical reduction of Fe(III) in sunlit surface waters, namely, ligand-to-metal charge transfer (LMCT) and superoxide-mediated iron reduction (SMIR). In this study, we investigate the impact of Fe(III) speciation (organically complexed (Fe(III)L versus iron oxyhydroxide (AFO)) on Fe(III) reducibility by photogenerated superoxide (O2•–) and LMCT. To simulate conditions typical of fresh, estuarine, and coastal waters, we have used Suwannee River Fulvic Acid (SRFA) as a representative of the natural organic matter likely to associate with Fe(III). Our results show that the photolabile Fe(III)SRFA complex is reduced rapidly by LMCT, while O2•– does not play a role in reduction of these entities. In contrast, the relatively less photolabile AFO is reduced by both O2•– and LMCT. The reduction of AFO by O2•– occurs following the dissolution of AFO, and hence, the contribution of O2•– to reductive dissolution of AFO is dependent on conditions such as the age of the AFO and initial AFO concentration affecting the rate of dissolution of AFO. Our results further show that while colloidal Fe(III) (in this work, particles >0.025 μm) is reduced by O2•–, there is no involvement of O2•– in dissolved Fe(III) reduction. Overall, our results show that superoxide-mediated iron reduction will be important only in natural waters containing limited concentrations of Fe binding ligands.

26084. 题目: Response of humic acids and soil organic matter to vegetation replacement in subtropical high mountain forests
文章编号: N19110918
期刊: Journal of Geophysical Research: Biogeosciences
作者: Hsueh‐Ching Wang, Guanglong Tian, Chiou‐Pin Chen, Ed‐Haun Chang, Chiao‐Ying Chou, Chyi‐Rong Chiou, Chih‐Yu Chiu
更新时间: 2019-11-09
摘要: Reforestation can alter the chemical composition of soil organic matter (SOM) and humification; however, information on how specific plant types impact SOM lability and humification is not well documented. In this study, we used solid‐state ¹³C NMR spectroscopy, photometric analysis, and chemical fractionation to examine carbon (C) components and lability of SOM in a Japanese cedar (Cryptomeria japonica) forest and bamboo (Phyllostachys edulis) plantation that reforested a cutover primary broadleaf forest. The ∆logK value of soil humic acids, the inverse index of SOM humification, was lowest in the bamboo plantation, suggesting a higher SOM humification stage in the bamboo plantation. The soil labile C/Total C ratio was highest in the bamboo plantation, and this can be attributed to low aromaticity and alkyl‐C/O‐alkyl‐C ratio (A/O‐A) in the bamboo litter. Intensive cultivation of the bamboo plantation accelerated litter breakdown in the strongly acidic soil, resulting in the depletion of SOM. Cedar coniferous leaves, with their high recalcitrant substances and slow decomposition, only slightly lowered SOM humification due to the substantial broadleaf understory. Our results suggest that the type of plants involved in reforestation and understory reestablishment is critical to how SOM humification and lability change during the reforestation through the control of litter C components. Further research into the interaction between microclimate change and forest type in forest conversion will be useful for increasing understanding on the impact of forest conversion on SOM lability and humification in subtropical high mountain forest ecosystems.

26085. 题目: Microbial processing of sediment‐derived dissolved organic matter: Implications for its subsequent biogeochemical cycling in overlying seawater
文章编号: N19110917
期刊: Journal of Geophysical Research: Biogeosciences
作者: Ruanhong Cai, Wenchu Zhou, Chen He, Kai Tang, Weidong Guo, Quan Shi, Michael Gonsior, Nianzhi Jiao
更新时间: 2019-11-09
摘要: Coastal sediments contain a large amount of dissolved organic matter (DOM), which can be mobilized into the overlying water by natural and anthropogenic activities. The bioavailability and subsequent biogeochemical effects of this sediment‐derived DOM are unclear. To investigate those, we collected a sediment pore‐water DOM (SDOM) sample and its overlying seawater to conduct a bioassay experiment, which allowed tracking of both short‐term and long‐term microbial processes in the context of DOM transformations. Short‐term incubation results show that the SDOM extract supported the growth of specific taxa. The microbial community composition changed dramatically and an approximately 50% of SDOM‐derived carbon was consumed within the first 2 days. Viruses likely played a role in promoting bacterial community succession, further enhancing transformation of this SDOM. Long‐term incubation results show that labile DOM was gradually consumed, while approximately 16% of the initial SDOM appeared to be recalcitrant to microbial utilization and remained at the end (after 110 days) of the incubation experiment. Despite the short‐term drastic changes in microbial community composition, a highly diverse microbial community is similar to the control at the end of the incubation. It is suggested here that re‐suspension of coastal sediments weakens their role as a net sink of carbon, with most of the mobilized SDOM transformed by successive microbial communities in the overlying seawater and the remaining recalcitrant organic material becoming part of the long‐lived DOM pool. Thus the bioavailability of the coastal SDOM might influence the carbon budget in coastal oceans.

26086. 题目: Organic carbon origin, benthic faunal consumption and burial in sediments of northern Atlantic and Arctic fjords (60‐81 0N)
文章编号: N19110916
期刊: Journal of Geophysical Research: Biogeosciences
作者: Maria Włodarska‐Kowalczuk, Mikołaj Mazurkiewicz, Barbara Górska, Loïc N. Michel, Emilia Jankowska, Agata Zaborska
更新时间: 2019-11-09
摘要: Fjords have been recently recognized as hotspots of organic carbon (C_org) sequestration in marine sediments. This study aims to identify regional and local drivers of variability of C_org burial in north Atlantic and Arctic fjords. We provide a comparative quantification of C_org, δ¹³C, photosynthetic pigments content, benthic biomass, consumption, C_org accumulation and burial rates in sediments in six fjords (60 to 81⁰N). Higher sediment C_org content in southern Norway reflected longer phytoplankton growth season and higher productivity. Higher contributions of terrestrial C_org were noted in temperate/southern Norway (dense land vegetation and high precipitation) and Arctic/Svalbard (glacial erosion) than in subarctic/northern Norway locations. Benthic biomass and carbon consumption were best correlated to δ¹³C and photosynthetic pigments content indicating control by quality rather than quantity of available food. Benthic faunal consumption did not seem to affect the variability in C_org burial. Regional environmental factors (water temperature, latitude) combined with local factors (C_org, grain size, pigment concentration) explained 94 % of C_org burial variability. Based on the present study and literature data on C_org content, origin and burial rates, the fjords were classified into four categories: temperate, subarctic, Arctic with and without glaciers. The variability in marine productivity, terrestrial inflows and carbon sequestration in fjords must be considered for global estimates of their role in blue carbon storage and for building scenarios of future changes in the course of climate warming.

26087. 题目: Organic carbon decomposition rates with depth and contribution of inorganic carbon to CO2 emissions under a Mediterranean agroforestry system
文章编号: N19110915
期刊: European Journal of Soil Science
作者: R. Cardinael, T. Chevallier, B. Guenet, C. Girardin, T. Cozzi, V. Pouteau, C. Chenu
更新时间: 2019-11-09
摘要: Agroforestry systems have been much studied for their potential to store soil organic carbon (SOC). However, few data are available on their specific impact on potential SOC mineralization, especially at depth in subsoils. Moreover, many soils of the world, especially in arid and semi‐arid environments, also contain large stocks of soil inorganic carbon (SIC) as carbonates. Consequently, the organic carbon dynamics has been poorly investigated in these soils due to the complexity of measurements and of the processes involved. To assess mineralization rates of SOC with depth, we incubated soil samples coming from an 18‐year‐old agroforestry system (both tree row and alley) and an adjacent agricultural plot established on a calcareous soil in France. Soil samples were taken at four different depths: 0–10, 10–30, 70–100 and 160–180 cm. Total CO₂ emissions, the isotopic composition (δ¹³C, ‰) of the CO₂ and microbial biomass were measured. The SIC concentrations ranged from 48 to 63 g C kg⁻¹ soil and the SOC concentrations ranged from 4 to 17 g C kg⁻¹ soil. The contribution of SIC‐derived CO₂ represented about 20% in the topsoil and 60% in the subsoil of the total soil CO₂ emissions. The microbial biomass and the SOC‐derived CO₂ emissions were larger in the topsoil, but the decomposition rates (day⁻¹) remained stable with depth, suggesting that only the size of the labile carbon pool was modified with depth. Subsoil organic carbon seems to be as prone to decomposition as surface organic carbon. No difference in CO₂ emissions was found between the agroforestry and the control plot, except in the tree row at 0–10 cm. Our results suggest that the measurement of soil respiration in calcareous soils could be overestimated if the isotopic signature of the CO₂ is not taken into account. It also advocates more in‐depth studies on carbonate dissolution‐precipitation processes and their impact on CO₂ emissions.

26088. 题目: Sorption of ionic and neutral species of pharmaceuticals to loessial soil amended with biochars
文章编号: N19110914
期刊: Environmental Science and Pollution Research
作者: Lin Wu, Erping Bi
更新时间: 2019-11-09
摘要: To clarify the impact of biochar amendment on soil sorption for coexisting pharmaceuticals, wheat straw-derived biochars pyrolyzed at 300 and 700 °C (labeled as WS300 and WS700, respectively) were prepared. Batch experiments on ketoprofen (KTP), atenolol (ATL) and carbamazepine (CBZ) sorption to biochars, loessial soil and biochar-amended soils were conducted. The results indicated that sorption affinity of different species of pharmaceuticals to WS300 and WS700 was in the order of cationic ATL > neutral CBZ > anionic KTP. Cationic ATL had the highest sorption to biochars due to electrostatic attraction. Coexisting ATL, CBZ and KTP competed for the shared adsorption sites on carbonized phase of biochars, and π–π interactions were proposed to be the main sorption mechanism. Sorption coefficients (K_d) and nonlinearity of ATL, CBZ and KTP to soil increased when biochar was added (5% by weight), especially for WS700 with higher specific surface area. K_d values of the three pharmaceuticals to WS700-amended soil in either single solute or bisolute system were one to two orders of magnitude higher than those to soil, indicating the promoting role of WS700 in sorption of coexisting pharmaceuticals in soil. The study demonstrated the enhanced and competitive sorption of ionic and neutral species of pharmaceuticals to soil amended with biochars, which is helpful in designing biochar as effective sorbents for immobilization of pharmaceuticals in soil remediation.

26089. 题目: Early effects of temperate agroforestry practices on soil organic matter and microbial enzyme activity
文章编号: N19110913
期刊: Plant and Soil
作者: Hugues Clivot, Caroline Petitjean, Nicolas Marron, Erwin Dallé, Julie Genestier, Nicolas Blaszczyk, Philippe Santenoise, Alexandre Laflotte, Séverine Piutti
更新时间: 2019-11-09
摘要: Aims: A field experiment was conducted to evaluate the effects of alley cropping systems on microbial activity and soil organic matter (SOM) pools. We hypothesized that enzyme activity and labile pools of SOM are early and sensitive indicators of changes induced by tree introduction in the cropping systems. Methods: Poplar-alfalfa and alder-gramineous (cereal or ryegrass) associations and their respective control systems (alfalfa and gramineous) were compared in terms of soil carbon (C), nitrogen (N) and water contents, SOM labile pools, NIRS-MIRS spectra and microbial enzyme activity in the topsoil (0–15 cm) for 4 years after tree planting. Results: After 1 year, tree introduction induced a decrease in soil water content, microbial biomass N and some enzyme activities under alfalfa system. After 4 years, tree introduction resulted in higher soil water contents in both systems (alfalfa and gramineous); higher microbial biomass N and lower C:N in alfalfa-poplar plots compared to control plots. MIRS-NIRS analyses showed a greatest differentiation in SOM quality between alfalfa-based systems. Conclusions: The effects of temperate agroforestry systems on SOC in the topsoil are relatively weak in the first years after tree introduction. Observed effects were more pronounced in the alfalfa-poplar system, probably due to higher tree growth. Further studies will provide insights into the longer-term effects of these systems on soil functioning.

26090. 题目: Comparative study for adsorption of methylene blue dye on biochar derived from orange peel and banana biomass in aqueous solutions
文章编号: N19110912
期刊: Environmental Monitoring and Assessment
作者: M. T. Amin, A. A. Alazba, M. Shafiq
更新时间: 2019-11-09
摘要: Biochar pyrolyzed at 800 °C from banana (B_b) and orange peels (OP_b) was applied for sorption of methylene blue (MB) dye in a batch system. OP_b showed better affinity for MB dye than B_b with rapid increase in sorption capacity and percent removal for both biochars attaining equilibrium at 30 min. Chemisorption was suggested as the rate limiting step based on the best fitting of the pseudo-second-order reaction kinetics to the batch adsorption data. Linear increase in sorption capacity was seen as the initial MB dye concentration increased from 50 to 300 mg g⁻¹ with a 40 % decrease in removal efficiency. An increase of 90 mg g⁻¹ in sorption capacity for both biochars with a 15 and 30 % increase in removal efficiency for OP_b and B_b, respectively, was observed after increasing the solution pH from 2 to 6 or 8. An increase in sorption capacity of about 150 mg g⁻¹ was seen by increasing the biochar dose from 0.1 to 0.5 g. Langmuir isotherm model represented the adsorption data well as reflected by the high values of R² (0.99) when using both biochar, while least representation of adsorption data was seen in H-J isotherm as estimated from very low R² (0.6–0.66) for both types of biochar. An endothermic nature of MB dye sorption was suggested based on the linear increase in sorption capacity with an increase in solution temperature from 30 to 60 °C. This was further confirmed by the observed positive changes in standard entropy and standard enthalpy while negative values of Gibbs-free energies proposed the non-spontaneous natures of MB dye sorption on to both biochars. The effective sorption of MB dye demonstrated the potential of plant-based biochar as economically viable adsorbents for MB dye.

26091. 题目: Distributive features of soil carbon and nutrients in permafrost regions affected by forest fires in northern Da Xing’anling (Hinggan) Mountains, NE China
文章编号: N19110911
期刊: CATENA
作者: Xiaoying Li, Huijun Jin, Hongwei Wang, Xiaodong Wu, Yadong Huang, Ruixia He, Dongliang Luo, Xiaoying Jin
更新时间: 2019-11-09
摘要: In permafrost regions, forest fires actively affect physical and chemical properties of soils. Many studies have been conducted on the effects of forest fires on physical and chemical properties of topsoil, while the research on the fire-induced changes in carbon and other nutrients of soils has received much less attention, particularly that of soils in the active layer and near-surface permafrost. Here, using soil samples from two representative areas (Mangui and Alongshan), we investigated the effects of fires on soil nutrients of larch forest soils in the discontinuous permafrost zone in the northern Da Xing’anling (Hinggan) Mountains, Northeast China. The results showed that soil pH increased with fire severity due to the burning of soil organic matter by more severe fires and leaching of base elements in the residual ash into the soil, and; forest fires resulted in a weakly acidic post-fire soil environment. Soil total organic carbon, total nitrogen, and total phosphorus declined with increasing fire severity. A severe burn led to a substantial reduction of soil carbon and nitrogen, which were not recovered seven years after fire. However, there was no substantial change in the C/N ratio. For the two chosen areas, soil C/N ratios decreased with depth. In the first post-fire year, total potassium content increased and were similar at the sites affected by fires of different severity in the area burned seven years ago. There was no significant change in available phosphorus and available potassium. These changes were notable in the active layer and/or organic layers, but not so in the near-surface permafrost layer. Our results suggest that, in permafrost regions, forest fires have important effects on the distribution of soil carbon and other nutrients. This study on the feedback mechanisms between forest fires and nutrients in discontinuous permafrost regions in the northern Da Xing’anling Mountains is of importance for understanding the boreal carbon pool and cycling.

26092. 题目: Tidally resolved observations of organic carbon exchange through Eastern Long Island Sound
文章编号: N19110910
期刊: Estuarine, Coastal and Shelf Science
作者: Allison L. Byrd, Penny Vlahos, Michael M. Whitney, Christina Menniti, Joseph K. Warren
更新时间: 2019-11-09
摘要: Long Island Sound (LIS), is an urban estuary on the US east coast that undergoes seasonal hypoxia in its western and central regions. Approximately 90% of the water exchange between LIS and the adjacent continental shelf, the Mid Atlantic Bight, occurs through its eastern boundary. Recent estimates of organic carbon (OC) export from LIS have shown that this value varies appreciably, both seasonally and inter-annually. In this study, the spatial, tidal, and seasonal variability were resolved by measuring dissolved and particulate organic carbon (DOC and POC) concentrations and currents at a cross-section in eastern LIS near the estuary mouth. Fluxes were extrapolated from these high-resolution observations collected in May, August, and November 2016, and August 2017. In August of 2016 (a low flow year), an OC flux of 41 × 10⁶ kg C month⁻¹ resulted from a net import of DOC and an export of POC. In August of 2017 (an average flow year), there was an OC flux of 30 × 10⁶ kg C month ⁻¹ due to both DOC and POC export, indicating significant seasonal and inter-annual variability. The seasonally weighted-average total OC flux for 2016 was −41 × 10⁶ ± 9 kg C yr⁻¹ (net import). Results show that spot sampling in tidal estuaries can lead to spatial and tidal bias in concentrations of DOC (6–15%) and POC (31–18%) under high and low river flow conditions, respectively. This uncertainty is recommended for spot sampling in future OC studies and flux estimates in LIS.

26093. 题目: The bioavailability of riverine dissolved organic matter in coastal marine waters of southern Texas
文章编号: N19110909
期刊: Estuarine, Coastal and Shelf Science
作者: Kai Wu, Kaijun Lu, Minhan Dai, Zhanfei Liu
更新时间: 2019-11-09
摘要: To examine the bioavailability of dissolved organic carbon (DOC) and nitrogen (DON) in riverine dissolved organic matter (DOM) discharged to the coastal ocean, we conducted a series of month-long (24 days) incubation experiments with filtered samples collected from five southern Texas rivers (Lavaca, San Antonio, Mission, Aransas, and Nueces) inoculated using the same natural coastal microbial assemblages during summer (June) and winter (January) in 2016. The bioavailable fractions of DOC and DON (BDOC% and BDON%) varied substantially in different rivers and seasons, ranging respectively from 6 to 11%, and 15–38% during winter, and 0–6% and 9–15% during summer. Relatively higher BDOC% and BDON% occurred in the San Antonio and Aransas Rivers, which are impacted more by human activities through discharge from wastewater treatment plants. Seasonally, the riverine DOM was more bioavailable in winter than in summer when DOM may have been extensively degraded in situ due to the low base flow (or long residence time) and the elevated temperature in river water in summer. The principal component analysis on amino acid composition further confirmed that DOM was less degraded in winter than in summer. Functional gene abundance data revealed that winter riverine DOM was relatively labile as evidenced by an increase in N-metabolism pathways and functional genes during the winter incubation, whereas the opposite pattern was observed in summer. The findings of the varying bioavailability of DOM among rivers and seasons have important implications about the fate of riverine DOM and their potential contributions to nutrient supplies as southern Texas bays and estuaries are often nitrogen limited.

26094. 题目: The Early Pliocene global expansion of C₄ grasslands: A new organic carbon-isotopic dataset from the north China plain
文章编号: N19110908
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Jiayi Lu, Thomas J. Algeo, Guangsheng Zhuang, Jilong Yang, Guoqiao Xiao, Jiangsi Liu, Junhua Huang, Shucheng Xie
更新时间: 2019-11-09
摘要: C₄-grasslands are known to have first expanded globally in the Late Miocene, and recent research has hinted at a second expansion phase during the Early Pliocene; however, the geographic extent of this second event and its driving force are debated. In this study, we present organic carbon-isotopic evidence from a high-resolution drillcore in North China spanning the interval from ∼8.0 Ma to the present. A prominent positive δ¹³C_org shift at ∼4.1 Ma marks C₄-grassland expansion on the North China Plain, and rapid oscillations of >6‰ from ∼3.2 to 2.2 Ma imply large shifts between C₃- and C₄-dominated floras. Our δ¹³C_org profile mirrors carbon isotope shifts in loess-red clay deposits of the Chinese Loess Plateau, confirming the regional nature of this event. Furthermore, coeval carbon isotope records from Africa, North America, and South America provide evidence that the Early Pliocene C₄-grassland expansion was global in scale and temporally distinct from the Late Miocene event. Whereas the Late Miocene event may have been related to aridification and altered fire regimes, this mechanism cannot account for the Early Pliocene expansion owing to contemporaneous increases in humidity at many Northern Hemisphere sites. We hypothesize that C₄-grassland expansion in the Early Pliocene was triggered by falling atmospheric CO₂ levels, as evidenced by multiple pCO₂ proxy records and supported by quantum photosynthetic efficiency modeling.

26095. 题目: Tillage-induced effects on SOC through changes in aggregate stability and soil pore structure
文章编号: N19110907
期刊: Science of The Total Environment
作者: Yafei Guo, Ruqin Fan, Xiaoping Zhang, Yan Zhang, Donghui Wu, Neil McLaughlin, Shixiu Zhang, Xuewen Chen, Shuxia Jia, Aizhen Liang
更新时间: 2019-11-09
摘要: Soil structure plays a key role in soil organic carbon (SOC) dynamics. To determine how soil structure and aggregate affects SOC, we collected undisturbed soil cores of 0–5 cm layer (Typic Hapludoll) at an experimental site in Northeast China. The site had been under continuous tillage treatments of conventional tillage (CT) and no tillage (NT) for 17 years. We measured SOC by elemental analysis, aggregate size distribution by wet sieving, and soil pore parameters of pore size distribution, pore average diameter, pore numbers, pore connectivity, pore anisotropy, and pore fractal dimension by X-ray computer tomography. SOC content was significantly correlated with aggregate-associated SOC and soil water-stable aggregate content. CT with residue removal and annual plowing and cultivation increased <53 μm and 53–250 μm aggregates. CT decreased total SOC of 0–5 cm soil layer but increased aggregate-associated SOC of <53 μm. NT with greater residue input increased total SOC of 0–5 cm soil layer by 26.0% and aggregate mean weight diameter by 111.8% and increased aggregates of 250–1000 μm and >1000 μm. Soil under NT had a greater total number of micropores and greater connectivity whereas CT had a greater total number of macropores, average macropore diameter, anisotropy, and fractal dimension. Structural equation modeling showed that CT can decrease SOC of 0–5 cm soil layer by different paths, including increased anisotropy and macropore porosity, and NT can increase SOC of 0–5 cm soil layer by different paths, including increased mean weight diameter and connectivity. These results enhance our understanding of the relationship between soil structure and SOC, and could guide tillage management decisions to increase SOC.
图文摘要:

26096. 题目: The distribution, characteristics and ecological risks of microplastics in the mangroves of Southern China
文章编号: N19110906
期刊: Science of The Total Environment
作者: Ruili Li, Lingyun Yu, Minwei Chai, Hailun Wu, Xiaoshan Zhu
更新时间: 2019-11-09
摘要: During the production, use and disposal of plastic products, microplastics (MPs) are dispersed into the surrounding environment and have inevitable impacts on mangrove ecosystems in estuaries and offshore areas. In the mangroves of Southern China, the systematic evaluation of the distribution, characteristics and ecological risks of MPs is lacking. In this study, surface sediments (0-5 cm depth) were collected from six representative mangroves in China to explore MP contamination and its associated ecological risk. Based on the results, MP concentrations of MPs in mangrove sediments were as follows : FT (2249±747 items/kg), ZJ (736±269 items/kg), DF (649±443 items/kg), DZG (431±170 items/kg), YX (424±127 items/kg), and FCG (227±173 items/kg). The higher MP concentration in the Futian mangrove was mainly related to inputs from the Pearl River, the third largest river in China. The predominant shape, colour, and size of MPs were fibrous, white-transparent, and 500 -5,000 μm, respectively. The main MP polymer types were polypropylene, polyethylene, and polystyrene. Degradation artefacts were present on surface of MPs as well as metallic and non-metallic elements. MPs concentration in mangrove sediments increased with increasing social-economic development of surrounding districts, which indicated the clear influence of anthropogenic activity on MP pollution in these mangroves. Furthermore, total organic carbon (TOC) and silt content were positively associated with MPs (P < 0.01), indicating a facilitatory role in deposition of MPs in mangroves. Based on a comprehensive evaluation using the potential ecological risk factor (Ei), potential ecological risk (RI), polymer risk index (H) and pollution load index (PLI), MPs were found to present ecological risks in these mangroves, with the highest risk occurring in the Futian mangrove.
图文摘要:

26097. 题目: PAEs and PAHs in the surface sediments of the East China Sea: Occurrence, distribution and influence factors
文章编号: N19110905
期刊: Science of The Total Environment
作者: Xiangai Zhao, Haiyan Jin, Zhongqiang Ji, Donghao Li, Han Yeong Kaw, Jianfang Chen, Zhiyong Xie, Tianzhen Zhang
更新时间: 2019-11-09
摘要: A total of 29 sediment samples were collected from the East China Sea (ECS), with the Yangtze River estuary and the Zhejiang costal area. These sediment samples were analyzed for 6 phthalate esters (PAEs) and 16 polycyclic aromatic hydrocarbons (PAHs): the ΣPAEs and ΣPAHs concentrations ranged between 1649.5–8451.5 ng g^–1 (mean = 3446.3 ng g^–1) and 57.5–364.5 ng g^–1 (mean = 166.2 ng g^–1), respectively. Overall, the PAEs and PAHs concentrations gradually decreasing in the offshore and southward directions: their compositions and distributions suggest they could have mainly derived from the Yangtze River. In particular, their distribution was influenced by the sources’ proximity, hydrodynamics, and sediment geochemistry (i.e., TOC content and grain size). A classical two-end member model was utilized to estimate the fraction of terrestrial organic carbon in the sediments of the ECS. When the sediment was dominated by terrestrial-derived organic matter (OM), the concentrations of PAEs and PAHs were significantly correlated to the TOC content and gran size of the sediments. In contrast, the poor correlation of TOC content and grain size with PAEs in those sediments dominated by marine-derived OM, implied that the distribution of PAEs in the ECS was mainly related to land-based inputs, (especially to that of the Yangtze River). Regardless of the origin of most of the OM contained in the sediments, we observed positive correlations between the TOC content, and grain size of those containing PAHs. These results suggest that the distribution of PAHs in the ECS was not only related to the Yangtze River input, but also to the geochemical characteristics of the sediments.
图文摘要:

26098. 题目: A comparison of dissolved organic matter transformation in low pressure ultraviolet (LPUV) and ultraviolet light-emitting diode (UV-LED)/chlorine processes
文章编号: N19110904
期刊: Science of The Total Environment
作者: Ze-Chen Gao, Yi-Li Lin, Bin Xu, Ying Xia, Chen-Yan Hu, Tian-Yang Zhang, Tong-Cheng Cao, Yang Pan, Nai-Yun Gao
更新时间: 2019-11-09
摘要: This study compared the degradation of dissolved organic matter (DOM) by UV/chlorine advanced oxidation processes (AOPs) with emerging ultraviolet light-emitting diode (UV-LED, 275 nm) and traditional low pressure UV (LPUV, 254 nm) as UV sources. Excitation emission matrix-parallel factor (EEM-PARAFAC) analysis and two-dimensional (2D) correlation gel permeation chromatograph were applied to explore the evolutions of DOM during oxidation processes. The degradation behaviors of DOM indicated by UV absorbance at 254 nm (UV₂₅₄), dissolved organic carbon (DOC), and fluorophores fitted the pseudo-first-order kinetics well. The removal efficiency of DOM was similar under UV-LED and LPUV irradiation alone. However, UV-LED exhibited much higher degradation rates (increased by 29–160%) than LPUV regardless of the tracking variables during UV/chlorine processes. For three PARAFAC components, humic-like fluorescences were preferentially degraded by UV/chlorine oxidation compared with protein-like fluorescence potentially due to the differences of electronic moieties and molecular weight (MW). The decline in UV₂₅₄, DOC, and fluorophores increased with increasing chlorine dosage; linear correlations between those indicators were observed during the two AOPs. Moreover, UV-LED/chlorine could achieve greater extents of MW change. Our study demonstrated that UV-LED could be a superior alternative for the future selection of UV source in the UV/chlorine process.
图文摘要:

26099. 题目: Microbial growth and enzyme kinetics in rhizosphere hotspots are modulated by soil organics and nutrient availability
文章编号: N19110903
期刊: Soil Biology and Biochemistry
作者: Peng Tian, Bahar S. Razavi, Xuechen Zhang, Qingkui Wang, Evgenia Blagodatskaya
更新时间: 2019-11-09
摘要: The input of labile organics by plant roots stimulates microbial activity and therefore facilitates biochemical process rates in the rhizosphere compared to bulk soil, forming microbial hotspots. However, the extent to which the functional properties of soil microorganisms are different in the hotspots formed in soils with contrasting fertility remains unclear. We identified the hotspots related to different levels of Zea mays L. root architecture by zymography of leucine aminopeptidase in two soils with contrasting fertility. The hotspots localized by tiny wet-needle approach around first- and second-order roots were compared for parameters of microbial growth and enzyme kinetics. The pattern of hotspot distribution was more dispersed and the hotspot area was one order of magnitude smaller around first- versus second-order roots. The specific microbial growth rate (μ_m) and biomass of active microorganisms were soil-specific, with no difference between the hotspots and bulk soil in the fertile soil. In contrast, in the soil poor in organic matter and nutrients, 1.2-fold higher μ_m and greater growing biomass were found in the hotspots versus bulk soil. Lower enzyme affinity (1.3-2.2 times higher K_m value) of β-glucosidase and leucine aminopeptidase to the substrate was detected in the hotspots versus bulk soil, whereas only β-glucosidase showed higher potential enzyme activity (V_max) in the hotspots, being 1.7-2.1 times greater than that in bulk soil. Notably, the activity of C-acquiring enzyme, β-glucosidase positively correlated with the biomass of actively growing microorganisms. The fertile soil, on the whole, showed greater V_max and catalytic efficiency (V_max/K_m) and an approximately 2.5 times shorter substrate turnover time as compared to the poor soil. Therefore, we conclude that i) the differences in microbial growth strategy between rhizosphere hotspots and bulk soil were dependent on soil fertility; ii) affinity of hydrolytic enzyme systems to substrate was mainly modulated by plant, whereas potential enzymatic activity was driven by both plant and soil quality.

26100. 题目: Direct measurement of the in situ decomposition of microbial-derived soil organic matter
文章编号: N19110902
期刊: Soil Biology and Biochemistry
作者: Yuntao Hu, Qing Zheng, Lisa Noll, Shasha Zhang, Wolfgang Wanek
更新时间: 2019-11-09
摘要: Soil organic matter (SOM) is the dominant reservoir of terrestrial organic carbon and nitrogen, and microbial necromass represents a primary input to it. However, knowledge of stabilization mechanisms and direct measurements of the decomposition of microbial-derived SOM are lacking. Here we report a novel ¹⁵N isotope pool dilution approach using labeled amino sugars and muropeptides as tracers to quantify the decomposition of proteins and microbial cell walls, which allows to estimate in situ decomposition rates of microbial-derived SOM. Our results demonstrate that microbial cell walls are as recalcitrant as soil protein, exhibiting comparable turnover times across various ecosystems. The bacterial peptidoglycan in soils was primarily decomposed to muropeptides which can be directly utilized by microbes without being further depolymerized to free amino compounds. Moreover, bacterial peptidoglycan decomposition was correlated with soil microbial biomass while fungal chitin and soil protein decomposition were correlated with high soil pH and fine soil texture. This approach thereby provides new insights into the decomposition pathways and stabilization mechanisms of microbial-derived SOM constituents pertaining to SOM persistence.