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17341. 题目: Transport of cobalt and silver from the ocean to a reef island by seabirds in the South China Sea
文章编号: N19091806
期刊: Journal of Geophysical Research: Biogeosciences
作者: L.Q. Xu, L.B. Wu, Y.H. Zhang, J.J. Zhao
更新时间: 2019-09-18
摘要: Seabirds are typical bio‐vectors, delivering both nutrients and metals across ecosystem boundaries. However, seabird transfer of Ag and Co has not been well documented. Using an ornithogenic sediment core collected from the remote Zhaoshu Island, South China Sea, we investigated potential impacts of seabirds on Ag and Co transportation. These two elements exhibited peak abundance in a guano layer in the sediment profile. Via statistical analyses, Ag, Co and previously identified avian bio‐elements (Cn, Zn, Cd, P, As, Se) had a common source, i.e. guano. Guano input was also partly responsible for the distribution of Y, Ce, La, Sc and U in the bulk sediments. The concentration‐versus‐depth profiles of Mn, Mo, Bi, Rb and W were possibly associated with organic matter.

17342. 题目: From land to the ocean: the interplay between allochthonous and autochthonous contribution to particles in nepheloid layers of the Cariaco Basin, Venezuela
文章编号: N19091805
期刊: Journal of Geophysical Research: Biogeosciences
作者: Laura Lorenzoni, Robert C. Thunell, Claudia R. Benitez‐Nelson, Enrique Montes, Ramón Varela, Yrene Astor, Frank E. Muller‐Karger
更新时间: 2019-09-18
摘要: Lithogenic sediment input to the Cariaco Basin on the eastern Venezuelan shelf is controlled by small mountainous rivers (SMR). The Cariaco Basin is also an area of high phytoplankton productivity as a result of strong Trade Wind‐driven coastal upwelling. Characterizing the sources that supply particulate organic carbon (POC) to the deep Cariaco Basin is important for interpreting the paleoclimate record stored in its sediments. We measured suspended POC in the four main rivers draining into the Caraiaco Basin: the Tuy, Unare, Neveri and Manzanares, between September 2008 and September 2009, and conducted basin‐wide oceanographic cruises in September 2008 (rainy season) and March 2009 (upwelling season). Riverine concentrations of dissolved and particulate organic carbon (DOC and POC, respectively) in the four rivers were comparable to observations made in similar tropical SMR systems (POC was between 0.3‐2 mg C l‐1; DOC was between 100‐300 μM). Within the basin, the geochemical composition of surface particles and bottom nepheloid layers (BNL) changed with season. During the rainy season, the isotopic composition of both surface particles and BNL was characteristic of continentally‐derived material (δ13Corg, ~‐30 ‐ ‐26‰), while during upwelling, the composition shifted to values more typical of marine sources (δ13Corg, ~‐24 ‐ ‐20‰). SMRs represent an important component of the global carbon budget, which are often overlooked in ocean carbon budgets and also in paleoclimate studies of coastal environments.

17343. 题目: Convergence of terrestrial dissolved organic matter composition and the role of microbial buffering in aquatic ecosystems
文章编号: N19091804
期刊: Journal of Geophysical Research: Biogeosciences
作者: Jennifer L. Harfmann, François Guillemette, Karl Kaiser, Robert G.M. Spencer, Chia‐Ying Chuang, Peter J. Hernes
更新时间: 2019-09-18
摘要: Substantial changes in vegetation are expected as global climatic patterns shift, altering terrestrial sources of dissolved organic matter (DOM) entering rivers and streams. Since differences in the chemical composition of plant litters are reflected in the DOM that is leached, changes in riparian vegetation can directly influence the bioavailability of DOM to local aquatic microbial communities. We assessed the degradation dynamics and optical compositional changes of DOM from a variety of vascular plant leachates through microbial and coupled photochemical‐microbial degradation pathways. Initial decay rates ranged from 0.029 ± 0.011 day‐1 (microbial, mixed wetland) to 0.73 ± 0.62 day‐1 (photochemical‐microbial, mixed grasses) and all decay rates decreased to below 0.05 day‐1 after one week, converging below 0.029 day‐1 after two weeks. Overall we found a decrease in leachate optical diversity under microbial and photochemical‐microbial degradation, corresponding to a decrease in degraded leachate sample dispersion using principal component analysis. We show that despite initial variability across DOM leachates, successive degradation promotes kinetic and optical convergence such that, in aquatic environments with long residence times, terrestrial DOM source and composition are much less important on exported DOM composition than historically thought. In these systems, DOM compositional convergence may act as a natural buffer to provide stability of aquatic DOM cycling in the face of future landscape changes.

17344. 题目: Links between microbial processing of organic matter and the thermohaline and productivity features of a temperate river-influenced mediterranean coastal area
文章编号: N19091803
期刊: Estuarine, Coastal and Shelf Science
作者: Mauro Celussi, Luca Zoccarato, Fabrizio Bernardi Aubry, Mauro Bastianini, Raffaella Casotti, Cecilia Balestra, Michele Giani, Paola Del Negro
更新时间: 2019-09-18
摘要: Regions of freshwater influence are affected by a constant interplay of different environmental factors that rule their seasonal and interannual highly variable dynamics. Riverine freshwater discharges alter the buoyancy of the local water masses, generating dynamic fronts and increasing water column stratification and nutrient availability. In such a heterogeneous context the paradigms for biological-physical interactions driving biogeochemical dynamics in the open seas do not always apply. We present here data from 12 surveys spanning 12 years (from 2004 to 2016) in the Po River prodelta area, which is highly representative of the above-described complexity, as it conveys the second largest freshwater discharge to the Mediterranean Sea. In particular, we focused on the microbially-mediated organic matter processing by estimating the numerical abundances of non-pigmented (‘heterotrophic’) and photoautotrophic (Synechococcus) prokaryotes, heterotrophic production and the activity of the exoenzymes beta-glucosidase, alkaline phosphatase and leucine aminopeptidase. The abundance of Synechococcus and heterotrophic prokaryotes as well as microbial activities were positively correlated to temperature and chlorophyll a concentration. Concomitantly, each variable was negatively correlated to salinity. In high-temperature, high salinity and low chlorophyll a samples, the heterotrophic production was limited and deviated from the typical linearity of the Arrhenius' law, suggesting resource limitation rather than temperature control. A multivariate analysis performed to analyze the pattern of organic matter degradation/utilization highlighted 11 distinct clusters of functional diversity. Temperature, salinity and chlorophyll a concentration data alone were able to explain most of the functional cluster separation as evidenced by a regression tree analysis. For freshwater-influenced samples, salinity was the only variable affecting metabolic patterns, whereas in typically marine waters, at salinity ≥37, metabolic profiles were determined by specific combinations of all 3 parameters.

17345. 题目: Recalcitrant carbon for composting of fibrous aquatic waste: Degradation kinetics, spectroscopic study and effect on physico-chemical and nutritional properties
文章编号: N19091802
期刊: Journal of Environmental Management
作者: Mayur Shirish Jain, Siddhartha Paul, Ajay S. Kalamdhad
更新时间: 2019-09-18
摘要: Biochar, a recalcitrant carbon, is known to enhance organic matter degradation and improve physical properties. The objective of the study is to examine the probable effect of biochar addition during composting of a fibrous aquatic waste, i.e., water hyacinth though degradation kinetics and spectroscopic (FTIR and PXRD) analysis. Four dosages of biochar (0, 2.5, 5, and 10% w/w) were mixed to a mixture of water hyacinth, cow-dung and saw-dust comprising a total weight of 150 kg and composted using rotary drum composter for 20 days in batch mode. The study outcomes indicated that the amendment of biochar prolonged the duration of the thermophilic temperatures, reduced salinity, and promoted nutritional quality of compost. Moreover, biochar amendment enhanced the organic matter degradation with a rate constant of 0.029 day−1 and increased the total Kjeldahl nitrogen content up to 1.75% from an initial value of 1.10% in the reactor with 2.5% biochar amendment. Concurrently, biochar amendment aided in reducing Cu and Cr in the final product inferring 2.5% biochar is best suited for composting of water hyacinth. However, future studies are encouraged to decipher the microbial shifts and bioavailability of metals due to biochar dosage during composting for mitigating and managing the menace of such fibrous waste like water hyacinth by converting it to a soil conditioner.
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17346. 题目: Potential application of chicken manure biochar towards toxic phenol and 2,4-dinitrophenol in wastewaters
文章编号: N19091801
期刊: Journal of Environmental Management
作者: Phan Quang Thang, Kim Jitae, Bach Long Giang, N.M. Viet, Pham Thi Huong
更新时间: 2019-09-18
摘要: In this study, chicken manure biochar (CBC) was prepared and applied as adsorbent for the removal of phenolic pollutants including phenol (Ph) and 2,4-Dinitrophenol (DNP) from wastewaters. The feasibility analysis was focused on the adsorption effects of various factors, such as initial concentration, adsorbent dosage and reaction time. The results showed that BC could efficiently remove the Ph and DNP within 90 min of reaction time. Increasing of CBC dosage up to 0.3 g results in the maximum removal efficiency of Ph and DNP and lowers initial concentration which is beneficial for the adsorption of phenolic compounds. The second-order kinetic model and the Langmuir isotherm provided the best correlation with the adsorption data. Based on the Langmuir isotherm, maximum adsorption capacities (qmax) of Ph and DNP were found at 106.2 and 148.1 mg g−1, respectively. The obtained qmax values for CB were higher than those reported in literature on the adsorption of Ph and DNP using different biochar. Analyzing the regeneration characteristics, BC displayed high reusability with less than 20% loss in adsorption capacities of Ph and DNP, even after five repeated cycles. Investigation of the adsorption equilibrium under various conditions suggested several possible interaction mechanisms, including hydrogen bonding, electrostatic interaction and π- π bonding, which were attributed to the binding affinity of the adsorbent-adsorbate interaction.In the field application, the CBC showed an excellent removal efficiencies of Ph and DNP from industrial wastewaters (around 80% phenolic pollutants were removed). These findings support the potential use of CBC as effective adsorbent for treatment of wastewater containing Ph and DNP.
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17347. 题目: Dynamics of dissolved greenhouse gas response to seasonal water mixing in subtropical reservoirs
文章编号: N19091712
期刊: Environmental Monitoring and Assessment
作者: Zhenglun Yang, Changyuan Tang, Xing Li, Han Zhang, Yangyang Cai
更新时间: 2019-09-17
摘要: Although indispensable, significant uncertainty still exists in the underlying processes of the formation, dynamics, and emission of greenhouse gases (GHGs), the critical elements needed for the accurate estimation of greenhouse gas fluxes in inland lakes and reservoirs. Seasonal changes in water thermal stratification and turbulence strongly influence the concentration and emission of dissolved GHGs in water columns. Here, we studied the stratification and overturn processes of water column in the subtropical Lianhe Reservoir during different seasons and determined the dynamics of dissolved CO2, CH4, and N2O in the reservoir. Observation of temperature and analysis of chlorofluorocarbons (CFCs) clearly suggested that stratification of water column occurred in summer, but not in winter. The results showed that while dissolved oxygen (DO) was high in the top 5-m layer (the upper epilimnion layer), it dropped considerably especially below 10 m, resulting in an increase in concentration of CO2 and CH4. The high concentrations of dissolved N2O and CH4 were related to the decomposition of organic matter in the hypolimnion layer under anaerobic conditions after stratification. In winter overturn period, vertical circulants of water not only homogenized the concentration of DO in the water column, but also potentially moved CO2, CH4, and N2O from the bottom to the surface of the reservoir. The estimated GHG flux from the reservoir was − 7.13 mmol m−2 day−1 in summer and 2.14 mmol m−2 day−1 in winter. There was the potential that CO2 fluxes from subtropical lakes and reservoirs are overestimated by traditional geochemical models.

17348. 题目: Functionalized Biochar/Clay Composites for Reducing the Bioavailable Fraction of Arsenic and Cadmium in River Sediment
文章编号: N19091711
期刊: Environmental Toxicology and Chemistry
作者: Xiaohua Wang, Yanling Gu, Xiaofei Tan, Yunguo Liu, Yahui Zhou, Xinjiang Hu, XiaoXi Cai, Weihua Xu, Chen Zhang, Shaoheng Liu
更新时间: 2019-09-17
摘要: Biochar has frequently been used for the treatment of heavy metal pollution in water and soil; its effect on contaminated sediments requires further research. To improve the ability of biochar to immobilize heavy metals in sediment, we prepared a functionalized biochar/attapulgite composite by pyrolysis of the clay attapulgite and zinc chloride–pretreated rice straw biomass. Compared with the original biochar, the biochar/attapulgite composite had a large increase in specific surface area, pore volume, oxygen‐containing functional groups, and cation exchange capacity. Biochar effectively improved the dispersibility of attapulgite as a matrix. The results showed that the biochar/attapulgite composite effectively reduced the bioavailable fraction of arsenic (As) and cadmium (Cd) in river sediment, which was a great improvement compared with the raw biochar. After the sediment was treated with different biochar/attapulgite composites, the concentrations of As and Cd in the overlying water and the porewater, and the content of acid‐extractable and toxicity characteristic leaching procedure (TCLP)‐extractable As and Cd in the solid phase of the sediment decreased significantly. Both zinc chloride activation and attapulgite improved As and Cd immobilization in sediment when we used the biochar/attapulgite composite. The results suggest that biochar/attapulgite composite can be used as an efficient in situ sorbent amendment to improve the heavy metal immobilization ability of the sediment. Environ Toxicol Chem 2019;00:1–11. © 2019 SETAC

17349. 题目: Molecular biomarkers reveal co-metabolism effect of organic detritus in eutrophic lacustrine sediments
文章编号: N19091710
期刊: Science of The Total Environment
作者: Jie Ma, Xiaoguang Xu, Cencen Yu, Huichao Liu, Guoxiang Wang, Zhichun Li, Bin Xu, Ruijie Shi
更新时间: 2019-09-17
摘要: In eutrophic lacustrine ecosystems, drifting algal blooms are easily trapped by emergent macrophytes in downwind littoral zones, potentially altering carbon cycling processes; yet, knowledge remains limited about the mechanisms driving these changes. In this study, Microcystis and Phragmites, two dominant photosynthetic organisms in a hypereutrophic (Lake Taihu, China), were collected to simulate their co-decomposition processes. We demonstrate how molecular-level biomarkers could be used to elucidate the degradation dynamics of these two distinct organic forms in mixtures. Microcystis-derived carbon accelerated the decomposition rate of mixed systems (positive co-metabolism effect), rather than retarding it. The decomposition rate of TOC (total organic carbon) directly measured in the mixed treatments was 14% higher than when the two substrates were incubated alone. The use of specific fatty acid biomarkers facilitated more accurate tracking, demonstrating 1.09 times higher decomposition rates for Phragmites detritus in mixed treatments than in single Phragmites treatments. Furthermore, Microcystis showed 0.98 times higher decomposition rates in mixed treatments than in single treatments. The addition of Microcystis detritus to Phragmites detritus might meet microbial stoichiometric requirements, increasing the abundance of decomposing bacteria in Phragmites detritus, and accelerating decomposition rates, resulting in the co-metabolism of Microcystis and Phragmites carbon. Given the increasing occurrence of algal blooms in eutrophic lakes, the processes documented here might enhance greenhouse gas emissions from lakes with continued global climate warming.
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17350. 题目: Impact of wildfires on subsurface volcanic environments: New insights into speleothem chemistry
文章编号: N19091709
期刊: Science of The Total Environment
作者: Ana Z. Miller, José M. De la Rosa, Nicasio T. Jiménez-Morillo, Manuel F.C. Pereira, José A. Gonzalez-Perez, Heike Knicker, Cesareo Saiz-Jimenez
更新时间: 2019-09-17
摘要: Siliceous speleothems frequently reported in volcanic caves have been traditionally interpreted as resulting from basalt weathering combined with the activity of microbial communities. A characteristic feature in lava tubes from Hawaii, Azores and Canary Islands is the occurrence of black jelly-like speleothems. Here we describe the formation process of siliceous black speleothems found in a lava tube from La Palma, Canary Islands, Spain, based on mineralogy, microscopy, light stable isotopes, analytical pyrolysis, NMR spectroscopy and chemometric analyses. The data indicate that the black speleothems are composed of a hydrated gel matrix of amorphous aluminum silicate materials containing charred vegetation and thermally degraded resins from pines or triterpenoids from Erica arborea, characteristic of the overlying laurel forest. This is the first observation of a connection between fire and speleothem chemistry from volcanic caves. We conclude that wildfires and organic matter from the surface area overlying caves may play an important role in the formation of speleothems found in La Palma and demonstrate that siliceous speleothems are potential archives for past fires.
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17351. 题目: A comprehensive comparison between non-bulking and bulking aerobic granular sludge in microbial communities
文章编号: N19091708
期刊: Bioresource Technology
作者: Qiulai He, Jing Zhang, Shuxian Gao, Li Chen, Wanlin Lyu, Wei Zhang, Jianyang Song, Xiaoling Hu, Rongfan Chen, Hongyu Wang, Jian Yu
更新时间: 2019-09-17
摘要: Filamentous sludge bulking poses great threats to operational stability of aerobic granular sludge. Exploration of the microbial community aids knowledge of the causative factors to sludge bulking and guides directions for corresponding actions for prevention and controlling. Detailed changes of bacterial community within the non-bulking and bulking were performed and compared with a non-specific method through 1‰ (v/v) hydrogen peroxide (H2O2) addition. Results revealed that non-bulking/bulking granules maintained effective carbon and nitrogen removal, while bulking completely deteriorated enhanced biological phosphorus removal (EBPR). Excess extracellular polymeric substances (EPS) especially polysaccharide (PS) were directly linked with sludge bulking and abundant PS contributed to subsequent granular re-stability. Filamentous bulking dramatically altered the bacterial populations and 1‰ H2O2 effectively controlled bulking by eliminating causative filaments Singulisphaera and Thiothrix. Together, this study provides new insights into the non-bulking/bulking granules and could direct the prevention and control of filamentous bulking in aerobic granules.
图文摘要:

17352. 题目: Effect of biochar addition to sewage sludge on cadmium, copper and lead speciation in sewage sludge-amended soil
文章编号: N19091707
期刊: Chemosphere
作者: Aleksandra Bogusz, Patryk Oleszczuk
更新时间: 2019-09-17
摘要: The goal of the present work was to evaluate the speciation of cadmium (Cd), copper (Cu) and lead (Pb) in sewage sludge (SL) amended soil and SL-biochar (BC) amended soil in a long-term field experiment. SL or SL with biochar (at the dose of 2.5%, 5.0% or 10%) were applied to the soil. The dose of SL in the soil was 11 tdw/ha. At the beginning of the study, after 12 and 18 months the distribution of Cd, Cu and Pb was determined between the following fractions: (1) water soluble, exchangeable and bound to carbonates (F1), (2) bound to Fe–Mn oxides (F2), (3) bound to organic matter (F3) and (4) bound to quartz, feldspars, etc. (F4). The soil, SL and biochar were characterized by different distribution of Pb, Cu and Cd. The highest mobility of Cd and Cu was observed in the control soil, while Pb in SL. Addition of SL to the soil caused the increased of the mobility index of Cu and Pb, increasing the risk associated with the presence of these metals in the mobile soil fraction (F1). However, the addition of biochar to SL before application to the soil modified the distribution of studied elements. The most mobile and bioavailable fractions (F1) were transferred to less bioavailable (F2, F3) and potentially immobile fractions (F4).
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17353. 题目: Integrating metabolomics and physiological analysis to investigate the toxicological mechanisms of sewage sludge-derived biochars to wheat
文章编号: N19091706
期刊: Ecotoxicology and Environmental Safety
作者: Lulu Kong, Jingze Liu, Qian Han, Qixing Zhou, Junliang He
更新时间: 2019-09-17
摘要: Effects of sewage sludge biochars (SSBCs) on the growth of wheat and the specific toxicological mechanisms were investigated from a metabolic perspective for better ecological risk assessment. We observed that conversion of sludge to biochar remarkably changed the properties, and also caused a significant (p < 0.05) reduction of the toxicity towards wheat. Wheat growth under exposure to SSBCs was influenced by the pyrolysis temperature (300 °C, 500 °C and 700 °C), with root length being promoted by SSBCs prepared at higher temperatures (500 °C and 700 °C). In addition to the contaminants, including polycyclic aromatic hydrocarbons (PAHs) and potentially toxic elements (PTEs) detected in SSBCs, the morphological characteristics of biochars contributed substantially to the wheat growth. Metabolomics analysis revealed the remarkable differences in the metabolic profiles among the control (CK), SS300- and SS700-treated samples. The toxicological mechanisms involved were found to be associated with the regulation of metabolisms pathways of protein, fatty acids and carbohydrates, among which protein metabolism was most affected by SSBCs. This work presents an innovative concept that SSBCs produced at a proper temperature may minimize the toxic effects on plant growth by regulating the metabolic fluxes in vivo.

17354. 题目: Spectroscopic measurements and imaging of soil colour for field scale estimation of soil organic carbon
文章编号: N19091705
期刊: Geoderma
作者: Asa Gholizadeh, Mohammadmehdi Saberioon, Raphael A. Viscarra Rossel, Lubos Boruvka, Ales Klement
更新时间: 2019-09-17
摘要: Effective measurement and management of soil organic carbon (SOC) are essential for ecosystem function and food production. SOC has an important influence on soil properties and soil quality. Conventional SOC analysis is expensive and time-consuming. The development of spectral imaging sensors enables the acquisition of larger amounts of data using cheaper and faster methods. In addition, satellite remote sensing offers the potential to perform surveys more frequently and over larger areas. This research aimed to measure SOC content with colour as an indirect proxy. The measurements of soil colour were made at an agricultural site of the Czech Republic with an inexpensive digital camera and the Sentinel-2 remote sensor. Various soil colour spaces and colour indices derived from the (i) reflectance spectroscopy in the selected wavelengths of the visible (VIS) range (400–700 nm), (ii) RGB digital camera, and (iii) Sentinel-2 visible bands were used to train models for prediction of SOC. For modelling, we used the machine learning method, random forest (RF), and the models were validated with repeated 5-fold cross-validation. For prediction of SOC, the digital camera produced R2 = 0.85 and RMSEp = 0.11%, which had higher R2 and similar RMSEp compared to those obtained from the spectroscopy (R2 = 0.78 and RMSEp = 0.09%). Sentinel-2 predicted SOC with lower accuracy than other techniques; however, the results were still fair (R2 = 0.67 and RMSEp = 0.12%) and comparable with other methods. Using a digital camera with simple colour features was efficient. It enabled cheaper and accurate predictions of SOC compared to spectroscopic measurement and Sentinel-2 data.

17355. 题目: The chemical fingerprint of solubilized organic matter from eroded soils and sediments
文章编号: N19091704
期刊: Geochimica et Cosmochimica Acta
作者: Sandrine J. Matiasek, Peter J. Hernes
更新时间: 2019-09-17
摘要: Organic matter (OM) transfers between solid and water phases are critical components of OM cycling in surface waters as they contribute to compositional differences between dissolved OM (DOM) and particulate OM (POM). However, fractionation effects during such phase changes are not well-characterized, especially during the release of soluble OM from sediments and eroded soils. Agricultural practices alter the magnitude and timing of OM export and constitute a major source of sediment through soil erosion. This study assessed the elemental, biomolecular, and optical characteristics of DOM solubilized from sediments and soils in an agricultural watershed of northern California to trace compositional changes during OM flow from mobilized soils in streams. Relative to mineral-bound OM, solubilized DOM was nitrogen-poor (more than doubled C:N ratios) and depleted in amino acids and lignin (three- to six-fold decrease in carbon-normalized yields). Distinct fractionation patterns of individual amino acids and lignin phenols led to a more acidic pool of solubilized DOM that appeared substantially more degraded than its source POM, with decreased degradation index (DI) values and more than doubled molar contributions of non-protein amino acids and processing ratio (PR) values. Lignin composition also greatly differed in solubilized DOM compared to mineral-bound OM, with cinnamyl:vanillyl phenol ratios up to six-fold lower in solubilized lignin than in particulate lignin. Solubilized DOM generally resembled stream DOM more than its source POM and was chemically distinguishable from DOM leached from plants. Absorption coefficients and fluorescence peak intensities were strongly correlated with solubilized DOM concentrations and composition, while optical parameters established to characterize DOM origin and reactivity such as spectral slope, fluorescence index, and carbon-specific fluorescence intensities suggested unique compositional traits for solubilized DOM compared to stream DOM. This study therefore documented strong fractionation patterns during solubilization, linking eroded soil OM and stream DOM and highlighting a pathway that can account for compositional differences between DOM and POM in surface waters. A new amino acid parameter, the Solubilization Index (SI), was defined to capture the effects of solubilization processes on OM composition. SI values in solubilized DOM were up to an order of magnitude higher than in its source POM and were similar to SI values in stream DOM. Because the SI is based on empirical behaviors of individual amino acids, each tied to mechanistic interpretations, the SI is demonstrating a strong potential for mechanistic-driven research on the extent of phase changes in streamwater DOM.

17356. 题目: The pH optimum of soil exoenzymes adapt to long term changes in soil pH
文章编号: N19091703
期刊: Soil Biology and Biochemistry
作者: Jérémy Puissant, Briony Jones, Tim Goodall, Dana Mang, Aimeric Blaud, Hyun Soon Gweon, Ashish Malik, Davey L. Jones, Ian M. Clark, Penny R. Hirsch, Robert Griffiths
更新时间: 2019-09-17
摘要: Soil exoenzymes released by microorganisms break down organic matter and are crucial in regulating C, N and P cycling. Soil pH is known to influence enzyme activity, and is also a strong driver of microbial community composition; but little is known about how alterations in soil pH affect enzymatic activity and how this is mediated by microbial communities. To assess long term enzymatic adaptation to soil pH, we conducted enzyme assays at buffered pH levels on two historically managed soils maintained at either pH 5 or 7 from the Rothamsted Park Grass Long-term experiment. The pH optima for a range of exoenzymes involved in C, N, P cycling, differed between the two soils, the direction of the shift being toward the source soil pH, indicating the production of pH adapted isoenzymes by the soil microbial community. Soil bacterial and fungal communities determined by amplicon sequencing were clearly distinct between pH 5 and soil pH 7 soils, possibly explaining differences in enzymatic responses. Furthermore, β-glucosidase gene sequences extracted from metagenomes revealed an increased abundance of Acidobacterial producers in the pH 5 soils, and Actinobacteria in pH 7 soils. Our findings demonstrate that the pH optimum of soil exoenzymes adapt to long term changes in soil pH, the direction being dependent on the soil pH shift; and we provide further evidence that changes in functional microbial communities may underpin this phenomena, though new research is now needed to directly link change in enzyme activity optima with microbial communities. More generally, our new findings have large implications for modelling the efficiency of different microbial enzymatic processes under changing environmental conditions.

17357. 题目: 15N-amino sugar stable isotope probing (15N-SIP) to trace the assimilation of fertiliser-N by soil bacterial and fungal communities
文章编号: N19091702
期刊: Soil Biology and Biochemistry
作者: Michaela K. Reay, Alice F. Charteris, Davey L. Jones, Richard P. Evershed
更新时间: 2019-09-17
摘要: Although amino sugars represent a major component of soil organic nitrogen (ON), the assimilation of nitrate (NO3 ) and ammonium (NH4+) into amino sugars (AS) by soil bacteria and fungi represents a neglected aspect of the global N cycle. A deeper knowledge of AS responses to N fertiliser addition may help enhance N use efficiency (NUE) within agricultural systems. Our aim was to extend a sensitive compound-specific 15N-stable isotope probing (SIP) approach developed for amino acids to investigate the immobilization of inorganic N into a range of amino sugars (muramic acid, glucosamine, galactosamine, mannosamine). Laboratory incubations using 15N-ammonium and 15N-nitrate applied at agriculturally relevant rates (190 and 100 kg N ha−1 for 15NH4+ and 15NO3, respectively) were carried out to obtain quantitative measures of N-assimilation into the AS pool of a grassland soil over a 32-d period. Using gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) we found that δ15N values for individual AS reflected differences in routing of the applied ammonium and nitrate. The contrasting N-assimilation dynamics of bacterial and fungal communities were demonstrated through determinations of percentage 15N incorporation into diagnostic AS. N-assimilation dynamics of the bacterial community were altered with the applied substrate whilst fungal N-assimilation dynamics were unaffected. Rates and fluxes of the applied N-substrates into the bacterial AS pool reflected known biosynthetic pathways for AS, with fungal glucosamine appearing to be biosynthetically further from the applied substrates than bacterial glucosamine due to different turnover rates. This sensitive and specific compound-specific 15N-SIP approach using AS, building on existing approaches with amino acids (AA), enables differentiation of N-assimilation dynamics within the microbial community and assessment of microbial NUE with agriculturally relevant fertilisation rates.
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17358. 题目: Using UV/H2O2 pre-oxidation combined with an optimised disinfection scenario to control CX3R-type disinfection by-product formation
文章编号: N19091701
期刊: Water Research
作者: Shunke Ding, Feifei Wang, Wenhai Chu, Chao Fang, Yang Pan, Shan Lu, Naiyun Gao
更新时间: 2019-09-17
摘要: The effects of UV/H2O2 pre-oxidation or disinfection methods on the formation of partial disinfection by-products (DBPs) have been studied previously. This study assessed the effect of UV/H2O2 pre-oxidation combined with optimisation of the disinfection method on the formation of six classes of CX3R-type DBPs, including trihalomethanes (THMs), haloacetic acids (HAAs), haloacetaldehydes (HALs), haloacetonitriles (HANs), halonitromethanes (HNMs), and haloacetamides (HAMs). Experimental results showed that a simulated distribution system (SDS) in-situ chloramination or pre-chlorination followed by chloramination effectively decreased total CX3R-type DBP formation by 51.1–63.5% compared to SDS chlorination, but little reduction in DBP-associated toxicity was observed. The dominant contributors to the calculated toxicity were HANs and HALs. UV/H2O2 pre-oxidation was able to destroy the aromatic and dissolved organic nitrogen components of natural organic matter. As a consequence, THM, HAA, and HAL formations increased by 49.5–55.0%, 47.8–61.9%, and 42.0–67.1%, respectively, whereas HAN, HNM, and HAM formations significantly decreased by 52.1–83.6%, 42.9–87.3%, and 74.1–100.0%. UV/H2O2 pre-oxidation increased total CX3R-type DBP formation, during SDS chlorination, whereas SDS in-situ chloramination or pre-chlorination followed by chloramination of UV/H2O2-treated water produced lower total CX3R-type DBPs than water without UV/H2O2 pre-oxidation. Nevertheless, the DBP-associated toxicity of water with UV/H2O2 pre-oxidation was substantially lower than the toxicity for water without UV/H2O2 pre-oxidation, decreased by 24.1–82.7%. HALs followed by HANs contribute to major toxic potencies in UV/H2O2 treated water. The best DBP concentration and DBP-associated toxicity abatement results were achieved for water treated by UV/H2O2 coupled with in-situ chloramination treatment.
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17359. 题目: Recent onset of eutrophication in Lake Izabal, the largest water body in Guatemala
文章编号: N19091604
期刊: Journal of Paleolimnology
作者: Jonathan Obrist-Farner, Mark Brenner, Jason H. Curtis, William F. Kenney, Carlo Salvinelli
更新时间: 2019-09-16
摘要: Recent human population growth has contributed to the degradation of environmental resources in Guatemala. Since 1900, the population of the country grew from < 1 to > 17 million inhabitants. The watershed of Lake Izabal, eastern Guatemala, also experienced rapid population growth, and with it, development of intensive agriculture in areas adjacent to the lake. These recent demographic and land-use changes altered anthropogenic nutrient inputs to the water body, through delivery of raw sewage, and agricultural practices that include excessive use of fertilizers. Currently, Lake Izabal is marked by frequent algal blooms and associated fish-kill events. It also hosts a number of invasive, and in some cases, exotic plant and animal species. We used data from a sediment core collected in the western end of the lake to link past anthropogenic activities in the watershed to the deterioration of water quality and shifts in aquatic ecosystem functioning. We measured total organic carbon (TOC), total nitrogen (TN), and δ13C and δ15N of organic matter in a 137Cs- and 14C-dated sediment core from the Polochic Delta in Lake Izabal to infer past limnological changes. The core chronology indicates that 505 cm of sediment accumulated in only the last 370 years (~ 1.4 cm a−1). TOC and TN concentrations increased since about 1950, a time during which the TOC:TN ratio decreased, indicating a relatively greater contribution of phytoplankton to the sediment organic matter. Stratigraphic shifts in δ13C and δ15N indicate recent increasing inputs of raw sewage and fertilizer to the lake during the same time period. Lake Izabal, like many other water bodies in Guatemala, is starting to undergo cultural eutrophication, which probably accounts for the frequent algal blooms, proliferation of invasive species (e.g. Hydrilla verticillata), and decline in fish abundance.

17360. 题目: Soil moisture as a key factor in carbon release from thawing permafrost in a boreal forest
文章编号: N19091603
期刊: Geoderma
作者: Xiaoyan Song, Genxu Wang, Fei Ran, Kewei Huang, Juying Sun, Chunlin Song
更新时间: 2019-09-16
摘要: The feedback between the atmosphere and permafrost soils containing large carbon stocks is currently considered the most important carbon-cycle feedback, but it is missing from climate models due to many uncertainties. Knowledge of how differences in post-thaw hydrological conditions affect carbon (C) release is critical for predicting permafrost feedback, but this knowledge remains limited. In this study, permafrost and active layer soils from the southern margin of the Eurasian boreal permafrost region in Northeast China were collected and incubated under experimentally modified moisture to monitor their CO2 and CH4 productions under simulated natural, drier and flooded conditions. We also characterized soil properties related to soil organic carbon (SOC) quality and microbial activities to determine their relations with measured C productions. We found that permafrost had higher C release per gram of SOC basis (C vulnerability) than the active layer, which suggested that there would be a high risk for C emissions in the permafrost region when permafrost thaws in the warming future. However, hydrological conditions following the permafrost thaw control these emissions. Permafrost C decomposed in relatively aerobic upland systems had higher C emissions than that decomposed in anaerobic wetland environments. Our results suggest a greater climate forcing of C release in aerobic than anaerobic conditions, but there are some uncertainties resulting from the unknown long-term CH4 production rates. Moreover, we found that the aerobic C production in permafrost after thawing could be constrained by water stress, suggesting that previous predictions based on soil incubations at natural soil moisture might overestimate the aerobic permafrost C release.

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