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12581. 题目: δ13C records from fish fossils as paleo-indicators of ecosystem response to lake levels in the Plio-Pleistocene lakes of Tugen Hills, Kenya
文章编号: N19081703
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Anne L. Billingsley, Peter Reinthal, David L. Dettman, John D. Kingston, Alan L. Deino, Kevin Ortiz, Benjamin Mohler, Andrew S. Cohen
更新时间: 2019-08-17
摘要: The carbon isotopic ratios of organic matter in fish fossils from diatomites and other lake beds in the HSPDP drill core from Tugen Hills, Kenya (2.56–3.29 Ma) reflect trophic resource uses, and can indicate the dietary habitats of fish in the paleolake. This information offers insight into how fish communities responded to lake-level fluctuations during the Plio-Pleistocene in the East African Rift Valley. We have compared this record with fish fossil isotopes from both a previously published study of a Lake Malawi drill core (139 ka–present) and core top (modern ca 1978) samples collected at the water/sediment boundary from Lake Turkana (Kenya) of known environmental provenance. Both the Lake Malawi drill core fossils (−7.2‰ to −27.5‰ VPDB) and modern Lake Turkana samples (−16‰ to −24.6‰ VPDB) have δ13C values indicating a mix of near-shore and deep-water pelagic species. In contrast, the δ13C values for the Tugen Hills core fossils vary only between −20‰ and −27‰ VPDB. The absence of δ13C values greater than −19‰, suggests none of these fossils are derived from near-shore benthic habitats. The lack of shallow water, benthic lacustrine fish fossils through the Tugen Hills lake cycles may indicate that the rate of change from low-lake stands to deeper lake phases was very rapid, and shallow water communities were not established for long enough to leave a fish fossil record at the core site. These results strongly suggest that lake level responses to climate variability in the Baringo basin of the East African Rift were very abrupt during the Plio-Pleistocene transition.

12582. 题目: Can biochar and oxalic acid alleviate the toxicity stress caused by polycyclic aromatic hydrocarbons in soil microbial communities?
文章编号: N19081702
期刊: Science of The Total Environment
作者: Xiaona Li, Yang Song, Shi Yao, Yongrong Bian, Chenggang Gu, Xinglun Yang, Fang Wang, Xin Jiang
更新时间: 2019-08-17
摘要: It remains unclear whether biochar amendment can mediate changes in soil microbial communities caused by organic contaminants in the rhizosphere. In this study, phenanthrene-contaminated soil was amended with biochar and oxalic acid (OA) alone or in combination and incubated for 21 days. Phospholipid fatty acids (PLFAs) and high-throughput sequencing were used to evaluate shifts in bacterial and fungal community structure. Phenanthrene stress led to significant shifts in both soil bacterial and fungal community structure, in particularly, 82% of microbial phyla decreased in abundance. Biochar and/or OA improved the phenanthrene-polluted soil by positively mediating shifts in soil microbial communities stressed by phenanthrene. Specifically, biochar and/or OA led to the survival of certain microbial taxa that were inhibited by phenanthrene stress. In addition, many functional microbial individuals and genes participating in polycyclic aromatic hydrocarbon (PAH) degradation were positively stimulated by high phenanthrene stress and further stimulated by the simultaneous application of biochar and OA. Based on these findings, tandem biochar and rhizoremediation may be a feasible strategy for relieving PAH toxicity to soil microbial communities.
图文摘要:

12583. 题目: Advanced redox zonation of the San Pedro Sula alluvial aquifer (Honduras) using data fusion and multivariate geostatistics
文章编号: N19081701
期刊: Science of The Total Environment
作者: Diego Di Curzio, Sergio Rusi, Patrizio Signanini
更新时间: 2019-08-17
摘要: The incorrect wastewater management and the land use distribution lead to severe environmental problems, creating heavy eutrophication condition in surface-water; when surface-water/groundwater relationships exist, the organic matter transferred to the aquifer oxidizes and triggers redox processes (i.e. Terminal Electron Accepting Processes, TEAPs), that provoke severe groundwater quality modifications and complicate its exploitation and management. For this reason, the definition of the redox zonation within an aquifer is an effective tool for the identification of the contamination sources and for the conceptual model refinement, when remediation strategies need to be planned. Although the redox processes are dynamic reactions, the aquifer redox zonation is generally aimed to identify homogenous zones, characterized by a predominant TEAP. To overcome this methodological approach, the Multi-Collocated Factorial Kriging (MCFK) was applied to redox-related physico-chemical parameters, which allowed identifying their spatial relationships at different scales, transferring this method from precision agriculture and soil science to hydrogeochemistry.The selected study area is the San Pedro Sula aquifer (Honduras), a multi-layer alluvial aquifer characterized by well-known surface-water/groundwater interactions and heavy eutrophicated streams. Here, high concentrations of Mn and Fe were found in the aquifer.The MCFK results identified a short-range (2300 m) factor, highlighting a strong relation between Mn concentrations and anoxic conditions, due to the organic matter transfer from eutrophicated surface-water into the aquifer. Simultaneously, the relationship between Fe and turbidity is related to a fine Fe(III) oxi-hydroxide colloidal phase, developed when different redox conditions of groundwater mix up in the wells. The long-range (6000 m) factor points out that Fe is related to redox processes at a wider scale, especially in the northern San Pedro Sula alluvial plain. These results are supported by both the Principal Component Analysis and the hydrogeochemical numerical modeling. As a result, different TEAPs occur simultaneously in contaminated areas, acting at multiple scales.
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12584. 题目: Nutrient Behavior in Hydrothermal Carbonization Aqueous Phase Following Recirculation and Reuse
文章编号: N19081608
期刊: Environmental Science & Technology
作者: Vivian Mau, Juliana Neumann, Bernhard Wehrli, Amit Gross
更新时间: 2019-08-16
摘要: Hydrothermal carbonization (HTC) has received much attention in recent years as a process to convert wet organic waste into carbon-rich hydrochar. The process also generates an aqueous phase that is still largely considered a burden. The success of HTC is dependent on finding solutions for the aqueous phase. In the present study, we provide the first investigation of recirculation of the aqueous phase from HTC of poultry litter as a means to concentrate nutrients and its subsequent application to agriculture as a fertilizer. Aqueous-phase recirculation generally resulted in an increase in nitrogen, phosphorus, and potassium concentrations up to cycle 3 with maximum concentrations reaching up to 5400, 397, and 23300 mg L–1 for N, P, and K, respectively. Recirculation did not adversely affect hydrochar composition or calorific value. The recirculated and nonrecirculated aqueous phases were able to support lettuce growth similar to a commercial fertilizer. Results from this study indicate that the combination of aqueous-phase recirculation and use as a fertilizer could be a suitable method to reutilize the aqueous phase and recycle nutrients back into agriculture, thus increasing HTC efficiency and economic feasibility.

12585. 题目: Floating duckweed mitigated ammonia volatilization and increased grain yield and nitrogen use efficiency of rice in biochar amended paddy soils
文章编号: N19081607
期刊: Chemosphere
作者: Haijun Sun, Dan A, Yanfang Feng, Meththika Vithanage, Sanchita Mandal, Sabry M. Shaheen, Jörg Rinklebe, Weiming Shi, Hailong Wang
更新时间: 2019-08-16
摘要: Biochar (BC) potentially accelerates ammonia (NH3) volatilization from rice paddy soils. In this regard, however, application the floating duckweed (FDW) to biochar-amended soil to control the NH3 volatilization is not studied up-to-date. Therefore, the impacts of BC application with and without FDW on the NH3 and nitrous oxide (N2O) emissions, NUE and rice grain yield were evaluated in a soil columns experiment. We repacked soil columns with Hydragric Anthrosol and Haplic Acrisol treated in triplicates with Urea, Urea + BC and Urea + BC + FDW. Total NH3 losses from Hydragric Anthrosol and Haplic Acrisol were 15.2–33.2 kg N ha−1 and 19.6–39.7 kg N ha−1, respectively. Urea + BC treatment recorded 25.6–43.7% higher (p < 0.05) NH3 losses than Urea treatment, attributing to higher pH value of floodwater. Floating duckweed decreased soil pH and therefore significantly reduced (p < 0.05) the NH3 volatilizations from the two soils by 50.6–54.2% over Urea + BC and by 34.2–38.0% over Urea treatment. Total N2O emissions from Hydragric Anthrosol and Haplic Acrisol were 1.19–3.42 kg N ha−1 and 0.67–2.08 kg N ha−1, respectively. Urea + BC treatment increased N2O emissions by 58.8–68.7% and Urea + BC + FDW treatment further increased N2O emission by 187.4–210.4% over Urea treatment. Higher ammonium content of the topsoil, explained the N2O increases in the Urea + BC and Urea + BC + FDW treatments. Urea + BC slightly reduced the rice grain yield and NUE, while the Urea + BC + FDW promoted both rice yield and NUE. Our data indicate that co-application of FDW along with BC in paddy soil could mitigate the NH3 volatilization and enhance the rice grain yield and NUE.

12586. 题目: Impacts of mono/divalent cations on the lamellar structure of cross-linked GO layers and membrane filtration performance for different DOM fractions
文章编号: N19081606
期刊: Chemosphere
作者: Jingjing Zhao, Yu Yang, Chen Li, Jing Liang, Li-an Hou
更新时间: 2019-08-16
摘要: This study evaluated the effects of co-existing cations (Na+ or Ca2+) on the lamellar structure of cross-linked graphene oxide (GO) layers and GO modified membrane performance in terms of their fouling behaviours and retention for single-model organic matter, namely, bull serum albumin (BSA), sodium alginate (SA), humic acid (HA) and tannic acid (TA). In the absence of co-existing cations, the GO layers mitigated membrane fouling for large molecules (SA, BSA, and HA) but led to severer pore blocking for small molecules (TA) compared with pristine membrane. Na+ and Ca2+ altered the performance impacts of the GO modified membrane due to different interactions with the cross-linked GO layers. Low concentrations of Na+ (<0.4 mM) enlarged interlayer spacing of the GO layers and caused a decrease in flux after physical cleaning, but the GO layers maintained the uniform lamellar structure. High concentrations of Na+ (>0.4 mM) promoted the aggregation of cross-linked GO layers through charge shielding and reduced the uniformity of lamellar structure, which weakened the antifouling performance for large molecules and promoted the passage of small molecules through the membrane. However, Ca2+ complexed with GO sheets and reinforced the uniform lamellar structure of the GO layers, leading to a better antifouling performance for the filtration of large molecules than the pristine membrane but aggravated TA fouling.
图文摘要:

12587. 题目: Estimation of K d (PAR) in inland waters across China in relation to the light absorption of optically active components
文章编号: N19081605
期刊: Environmental Science and Pollution Research
作者: Zhidan Wen, Kaishan Song, Chong Fang, Qian Yang, Ge Liu, Yingxin Shang, Xiaodi Wang
更新时间: 2019-08-16
摘要: The comprehensive analysis of the relationships between the attenuation of photosynthetic active radiation (Kd(PAR)) and light absorption is an imperative requirement to retrieve Kd(PAR) from remote sensing data for aquatic environments. The spatial distributions of the Kd(PAR) and light absorption of optically active components (aOACs) were routinely estimated in China lakes and reservoirs. Spatial Kd(PAR) was relatively dependent on the inorganic particles (average relative contribution of 57.95%). The aOACs could explain 70–87% of Kd(PAR) variations. A linear model is used to predict Kd(PAR), as a function of light absorption coefficient of phytoplankton (aphy), colored dissolved organic matter (aCDOM), and inorganic particles (aNAP): Kd(PAR) = 0.41 + 0.57 × aCDOM + 0.96 × aNAP + 0.57 × aphy (R2 = 0.87, n = 741, p < 0.001). In the lakes with low TSM concentration and non-eutrophic lakes with high TSM, aCDOM was the most powerful predicting factor on Kd(PAR). In eutrophic lakes with high TSM, aNAP had the most significant impact on Kd(PAR). This study allowed Kd(PAR) to be predicted from aOACs values in the inland waters.

12588. 题目: One-pot solvothermal synthesis of magnetic biochar from waste biomass: Formation mechanism and efficient adsorption of Cr(VI) in an aqueous solution
文章编号: N19081604
期刊: Science of The Total Environment
作者: Sha Liang, Shunquan Shi, Haohao Zhang, Jingjing Qiu, Wenhao Yu, Mingyang Li, Quan Gan, Wenbo Yu, Keke Xiao, Bingchuan Liu, Jingping Hu, Huijie Hou, Jiakuan Yang
更新时间: 2019-08-16
摘要: A facile one-pot solvothermal method was applied to synthesize a magnetic biochar composite (MB) using phoenix tree leaves-derived biochar as the carbon matrix. The structure of MB was optimized by varying the load ratio and particle size of Fe3O4 nanoparticles on biochar. Time-dependent structure and composition evolution of solid and liquid phases during heterogeneous solvothermal process were investigated to understand the formation mechanism of MB. Firstly, Fe2+/Fe3+ ions were coordinated by oxygen-containing groups on biochar and part of them were hydrolyzed to form iron hydroxides. Then, those iron-containing precursors were thermally decomposed and reduced to iron oxides; and finally Fe3O4 nanoparticles were generated. The MB had an adsorption capacity for Cr(VI) of 55.0 mg/g in an aqueous solution, which exceeds those of biochar (39.8 mg/g) and Fe3O4 nanoparticles (26.5 mg/g). The adsorption mechanism study reveals that biochar as a carbon skeleton mainly provided binding sites for Cr(VI) and electron-donor groups for reduction of Cr(VI), while Fe3O4 nanoparticles mainly involved in the immobilization of newly formed Cr(III) through formation of Fe(III)-Cr(III) hydroxide. MB exhibited a stable structure with a lower Fe leakage at pH 2.0 than that of a comparable magnetic biochar sample prepared by conventional co-precipitation method. Recycling experiments suggested that MB could keep 84% of its initial removal capability for Cr(VI) even after seven cycles. The results indicate that solvothermal method is a promising alternative to prepare magnetic biochar for adsorption of heavy metal-containing wastewater.
图文摘要:

12589. 题目: Efficient removal of oxytetracycline from aqueous solution using magnetic montmorillonite-biochar composite prepared by one step pyrolysis
文章编号: N19081603
期刊: Science of The Total Environment
作者: Guiwei Liang, Zhaowei Wang, Xing Yang, Tingting Qin, Xiaoyun Xie, Jing Zhao, Shan Li
更新时间: 2019-08-16
摘要: Three adsorbents, namely, original biochar (CLB), montmorillonite (MMT)-biochar composite (MBC), and magnetic MMT-biochar composite (MMBC) were successfully fabricated by one step pyrolysis of original cauliflower (Brassica oleracea L.) leaves, mixture of cauliflower leaves and MMT, and FeCl3-laden mixture of cauliflower leaves and MMT under limited oxygen atmosphere, respectively. The characterizations of samples indicated that substantial MMT mineral particles and Fe3O4 nanoparticle were dispersed on the surface of MMBC. Due to the introduction of Fe3O4, MMBC performed excellent magnetization property. The adsorption experiments of oxytetracycline (OTC) indicated that the maximum adsorption ability of MMBC was 58.85 mg·g−1, which was 2.63 times as large as CLB, also, larger than that of MBC. Meanwhile, pH, ionic strength, and humic acid (HA) performed slight effects for adsorption of OTC on MMBC. In addition, MMBC still removed 92% OTC after five regeneration cycles. Finally, primary mechanisms of OTC adsorption onto MMBC were attributed to hydrogen bonding and π-π reaction, and ion exchange reaction was considered to exist. Meanwhile, functional groups including Si-O-Al, Si-O-Si, Si-O, and Fe3O4 nanoparticles would provide extra binding sites for OTC adsorption. Therefore, MMBC had an obvious potential to apply into water purification as a reliable, low-cost, and environmentally friendly adsorbent.
图文摘要:

12590. 题目: Estimation of regional soil organic carbon stocks merging classified land-use information with detailed soil data
文章编号: N19081602
期刊: Science of The Total Environment
作者: Patrick Illiger, Gerd Schmidt, Irene Walde, Sören Hese, Andrej E. Kudrjavzev, Nadeshda Kurepina, Alexander Mizgirev, Eckart Stephan, Andrej Bondarovich, Manfred Frühauf
更新时间: 2019-08-16
摘要: The Kulunda Steppe in southwestern Siberia is one of the most intensely used agricultural landscapes in the world. Today it is characterized by depletive soil management practices and intensities that are unadapted to the local site conditions. Severe soil degradation and a loss of soil organic carbon (SOC) occurs at agriculturally used areas. So far, only few studies analyzed the spatial extent of these degradation effects and came to inconsistent assessments. We consider that different results arise from different definitions of SOC changes and from different spatial scales. Thus, local soils under different land-uses were sampled to a depth of 30 cm to determine land use dependent changes in topsoil SOC. Site specific soil data was merged with appropriate land-use classifications and soil maps from the mid-1970s and up-to-date data from 2013/2014 to balance land use corrected SOC pools. Here, we use a hierarchical approach to extrapolate local findings to regional and biome scale for typical and dry steppe. At the test area, land-use changed only moderately after the Soviet period. The steppe biomes are also characterized by large areas that are not affected by land-use change and ensuing SOC loss. Agricultural use led to a mean carbon loss of 23.3% for Chernozem soils and 13.9% for Kastanozems. Natural heterogeneities, such as small scale changes in relief or soil type, are missing in small scale maps due to generalization that leads to varying results. The calculated regionwide SOC loss is maximally 15.2% using the small scale map. Following different calculation approaches, according to different map scales, detailed or coarse resolution SOC-stocks differ by up to 59.7%. Consequently, subsequent calculations or modellings may include this uncertainty into consideration.
图文摘要:

12591. 题目: Alnus sibirica encroachment promotes dissolved organic carbon biodegradation in a boreal peatland
文章编号: N19081601
期刊: Science of The Total Environment
作者: Yang Zhang, Fu-Xi Shi, Rong Mao
更新时间: 2019-08-16
摘要: Symbiotic dinitrogen (N2)-fixing trees have been expanding to boreal peatlands, yet its influence on dissolved organic carbon (DOC) biodegradation is unclear. Here, we measured DOC, ammonium‑nitrogen (NH4+-N), nitrate‑nitrogen (NO3-N), dissolved inorganic nitrogen (DIN), and dissolved total nitrogen (DTN) concentrations, specific ultraviolet absorbance at 254 nm (SUVA254), and humification index in the extracts obtained from peats in the 0–10 cm, 10–20 cm, and 20–40 cm depths in the open peatlands and Alnus sibirica islands in a boreal peatland, Northeast China. Afterwards, the peat extracts were used to assess the effect of N2-fixing woody plant expansion on DOC biodegradation with a 42-day incubation experiment. The expansion of A. sibirica significantly increased NH4+-N, NO3-N, DIN, and DTN concentrations, but did not produce a significant effect on SUVA254 and humification index in the extracts in each depth. Following A. sibirica expansion, DOC biodegradation was enhanced by 24.5%, 15.4%, and 38.3% at 0–10 cm, 10–20 cm, and 20–40 cm depths, respectively. Furthermore, DOC biodegradation was significantly and negatively correlated with DOC:DIN and DOC:DTN ratios, but exhibited no significant relationship with SUVA254 and humification index. This implied that improved N availability and associated shifts in C:N stoichiometry determined the increase in DOC biodegradation following A. sibirica expansion. Our findings suggest that N2-fixing tree encroachment promotes microbial decomposition of DOC through improved N availability in boreal peatlands, which may cause organic C loss from soils in these C-enriched ecosystems.
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12592. 题目: A Significant Portion of Water-Soluble Organic Matter in Fresh Biomass Burning Particles Does Not Contribute to Hygroscopic Growth: An Application of Polarity Segregation by 1-Octanol–Water Partitioning Method
文章编号: N19081516
期刊: Environmental Science & Technology
作者: Jing Chen, Wen-Chien Lee, Masayuki Itoh, Mikinori Kuwata
更新时间: 2019-08-15
摘要: The importance of water-soluble organic matter (WSOM) on the hygroscopic growth of particles is recognized, yet roles of different categories of WSOM are under debate. We segregated WSOM from Indonesian biomass burning particles by the 1-octanol–water partitioning method. The method is based on the 1-octanol–water partition coefficient (KOW), which correlates with water solubility. The segregated WSOM was analyzed using the humidified tandem differential mobility analyzer (HTDMA) and time-of-flight aerosol chemical speciation monitor (ToF-ACSM). Both the hygroscopicity parameter κ and the fractional contribution of m/z 44 (f44), which serves as a metric for degree of oxygenation, increased with polarity. This result experimentally evidenced that highly polar/water-soluble OM is highly hygroscopic/oxygenated. Positive matrix factorization (PMF) identified three factors from the ToF-ACSM data. Deconvolution of κ by PMF factors demonstrated that the less polar fractions, which occupy approximately 20–60% of WSOM dependent on the biomass type, almost do not contribute to water uptake under subsaturated conditions. This result highlights that categorization of WSOM will be needed to understand how hygroscopic growth of aerosol particles is regulated.

12593. 题目: Adsorption and desorption of chromium with humic acid coated iron oxide nanoparticles
文章编号: N19081515
期刊: Environmental Science and Pollution Research
作者: Shilpa Gnanamuthu Singaraj, Biswanath Mahanty, Darshan Balachandran, Anamika Padmaprabha
更新时间: 2019-08-15
摘要: Presence of carcinogenic chromium, i.e., Cr(VI), in different industrial effluents necessitates design and development of effective abatement technologies. Nanosorbent consisting of iron oxide nanoparticles functionalized with soil-derived humic acid was employed for removal of Cr(VI). The point of zero charge for both humic acid and nanoparticles as estimated from pH shift experiments was between pH 8 and 9. Adsorption isotherm from batch experiments at neutral pH followed Langmuir model with projected maximum adsorption capacities for humic acid coated nanoparticles (24.13 mg/g) much higher than its uncoated counterpart (2.82 mg/g). Adsorption was process very fast and kinetics could be described with pseudo-second-order model (R2 > 0.98), for both nanoparticles. High E4/E6 ratio of extracted humic acid and Fourier transform infrared spectroscopy of coated nanoparticles (20–100 nm) indicated enrichment of hydroxyl, carboxylic, and aliphatic groups on surface leading for the better adsorption. Humic acid coated and uncoated nanoparticles regenerated with EDTA, NaOH, urea, Na2CO3, and NaCl treatments retained 35.90–59.67 and 26.37–36.28% of their initial adsorption capacities, respectively, in 2nd cycle. Experimental controls (virgin nanoparticles subjected to an identical regenerating environment) revealed irreversible surface modification as the cause for loss of their adsorption capacities.

12594. 题目: Characterization of the extracellular polymeric substances (EPS) of Virgibacillus strains capable of mediating the formation of high Mg-calcite and protodolomite
文章编号: N19081514
期刊: Marine Chemistry
作者: Zulfa Ali Al Disi, Nabil Zouari, Maria Dittrich, Samir Jaoua, Hamad Al Saad Al-Kuwari, Tomaso R.R. Bontognali
更新时间: 2019-08-15
摘要: The origin of dolomite a common mineral in the geological record is the subject of an ongoing debate. Among different hypotheses, it has been proposed that extracellular polymeric substances (EPS) excreted by microbes include organic molecules that catalyze the incorporation of Mg in the carbonate mineral. However, limited information exists on the composition of the EPS produced by CaMg carbonate- forming microbes, which in turn hampers a precise understanding of their role in the mineralization mechanism. Here, we present the results of laboratory experiments in which we cultured different strains of microbes, characterized their EPS, and identified components associated with carbonate minerals with high mol% Mg. Two Virgibacillus strains known to mediate the formation of Mg-rich carbonates, as well as a strain of Bacillus licheniformis a negative control that does not mediate mineral formation but produces EPS, were grown under different salinities and temperatures, which caused them to produce EPS with different compositions. The EPS were subsequently characterized by measuring total carbohydrate (TCHO) and total protein (TP) contents, as well as by Fourier-transform infrared spectroscopy (FTIR). At the tested conditions, we found that Mg-carbonates with a mol% Mg higher than 40% (i.e., potential dolomite precursor phases) formed exclusively in association with EPS rich in carbohydrates (TCHO > than 75% of the total mass). FTIR spectra of CaMg carbonate-forming strains were distinct from those of the non-mineral-forming strain in areas associated with the protein structures responsible for the formation of hydrogels, which contribute to hydration or dehydration of ionic clusters; further differences have been observed in the regions of phosphoryl functional groups. These results provide insight on which fraction of organic molecules and specific functional groups are, among the many constituents of EPS, important for mineral nucleation and incorporation of Mg into carbonate minerals, a crucial step for the formation of dolomite in natural environments.

12595. 题目: Interacting effects of plant invasion, climate, and soils on soil organic carbon storage in coastal wetlands
文章编号: N19081513
期刊: Journal of Geophysical Research: Biogeosciences
作者: Ren‐Min Yang
更新时间: 2019-08-15
摘要: Coastal wetland soils store large amounts of organic carbon, which is becoming vulnerable to environmental changes such as exotic species invasion and climate change. Soil organic carbon (SOC) is also related to soil biogeochemical factors. To understand the mechanisms of these changes in regulating SOC, it is necessary to characterize the direct and indirect effects of exotic species invasion, climate, and soil variables on SOC. We used a structural equation model to identify the key driving mechanisms of SOC storage to a depth of 1 m at 15 sites on the East China coast, where Spartina alterniflora Loisel. (S. alterniflora) invasion has significantly influenced SOC storage. The model revealed several patterns that are expected to explain the enhanced SOC storage. S. alterniflora invasion had a direct effect on SOC storage mainly due to its impacts on biomass production. Temperature had an important influence on SOC storage and the sub‐surface SOC content. SOC storage was also related to the interacting effects of S. alterniflora invasion and soil biogeochemical properties such as soil salinity, fine soil fraction, and bulk density. The relative contribution of SOC in the topsoil to SOC storage at a depth of 1 m decreased over time, while the contribution increased for the SOC below the surface. These results highlight the interactions among S. alterniflora invasion, climate, and soil properties in regulating SOC dynamics. Our results imply that the relative importance of vertical patterns to SOC storage associated with S. alterniflora invasion and temperature fluctuations will change over time.

12596. 题目: Bacterial Community on a Guyot in the Northwest Pacific Ocean Influenced by Physical Dynamics and Environmental Variables
文章编号: N19081512
期刊: Journal of Geophysical Research: Biogeosciences
作者: Qian Liu, Ying‐Yi Huo, Yue‐Hong Wu, Youcheng Bai, Yeping Yuan, Min Chen, Dongfeng Xu, Jun Wang, Chun‐Sheng Wang, Xue‐Wei Xu
更新时间: 2019-08-15
摘要: Bacterial communities in sediments of the Caiwei Seamount, a typical guyot located in the northwest Pacific Ocean, were investigated. A total of 727,879 16S ribosomal RNA gene sequences were retrieved from 8 sediment samples of the top (mean depth = 1407 m) and the base (mean depth = 5525 m) of the guyot through pyrosequencing of V6 hypervariable region, and clustered into 32,844 Operational Taxonomic Units. Abundant‐weighted UniFrac metric partitioned bacterial assemblies into two categories (the top community and the base community) by principal coordinates analysis, consisting with the grouping of sampling stations by environmental variables. Differences in depth and physicochemical properties of the surrounding environment (e.g. concentrations of dissolved oxygen and geochemical elements) between the top and the base of the guyot may cause this partition of bacterial communities, whereas the typical fluid flow around the guyot may potentially contribute to the bacterial dispersal and environmental homogeneity along the same layer, resulting in the similarity of bacterial community structure within the same region (the top or the base). The surface sediment on the top of the guyot harbored the bacterial communities with greater diversity and evenness, represented by Gamma‐ and Deltaproteobacteria involved in sulfur cycling. At the base of the guyot, Gammaproteobacteria related to sulfur‐oxidizing and Chloroflexi functioning in the decomposition of refractory organic matters dominated, suggesting the redox condition at the interface of the sediment and the water can influence bacteria‐mediated elemental cycling, eventually shaping the physicochemical and geological characteristics of a guyot.

12597. 题目: RECENT CHANGES IN SOIL PROPERTIES AND CARBON STOCKS IN FEN PEATLANDS ADJACENT TO OPEN‐PIT LIGNITE MINES
文章编号: N19081511
期刊: Land Degradation & Development
作者: Bartłomiej Glina, Piotr Gajewski, Mendyk Łukasz, Bogna Zawieja, Zbigniew Kaczmarek
更新时间: 2019-08-15
摘要: The simultaneous impact of climate change and human activities on soil organic carbon content (SOC) in peatlands is insufficiently recognized, especially in relation to peatlands affected by open‐pit mining. Given their importance in climate change feedback loops, long‐term observations of SOC changes in peatlands are essential. The aim of the study was to determine recent changes in the properties and SOC content/stock of agro‐managed fen peatlands located adjacent to open‐pit lignite mines. We studied two soil layers (0–20 and 20–40 cm) within 12 sampling plots in the Grójec Valley (Central Poland). Soil sample collection and field measurements took place in 2005 and again in 2015. The largest negative changes in soil properties (e.g. SOC content drop from 208–318 g kg‐1 in 2005 to 125–263 g kg‐1 in 2015 and SOC stock decrease from 12.1–16.2 kg m‐2 in 2005 to 9.22–14.5 kg m‐2 in 2015), as well as the largest variability of water table level were recorded in the northern part of the study area, affected by long‐term lignite mining (1982–2009). While such a strong changes were not observed in the plots from central and southern part of the valley (230–439 g kg‐1 in 2005 and 228–396 g kg‐1 in 2015; 11.5–29,2 kg m‐2 in 2005 and 13.4–36.1 kg m‐2, respectively). Our results showed that depletion of SOC content in lowland peatlands in the temperate climate zone (due to human activity and changeable weather conditions) will proceed unless we implement sustainable management practices or apply restoration plans at these sites.

12598. 题目: The viscosity behaviors of bacterial suspensions or extracellular polymeric substances and their effects on aerobic granular sludge
文章编号: N19081510
期刊: Environmental Science and Pollution Research
作者: Xilan Yang, Tianguang Xu, Pei Cao, Kai Qiao, Lei Wang, Tingting Zhao, Jianrong Zhu
更新时间: 2019-08-15
摘要: Although the viscosity behavior of bacteria and extracellular polymeric substances (EPS) in flocculent activated sludge (FAS) and aerobic granular sludge (AGS) has been investigated, no studies have explored the role of viscosity in microbial attachment in pure culture. This study investigated the viscosity behavior of bacteria and EPS. The results showed that bacteria and their EPS exhibited non-Newtonian fluid and shear-thinning behavior. The viscosity of bacteria and EPS was 1.55–3.80 cP and 1.10–2.40 cP, respectively, while the attachment of bacteria (optical density at 600 nm) was 0.1426–3.1015. Bacteria with high attachment secreted EPS with a higher viscosity (2.40 cP), whereas those with weak attachment expressed EPS with a lower viscosity (1.10 cP). Viscosity and microbial attachment or extracellular polysaccharide (PS) content were significantly positively correlated. PS content was the source of bacterial viscosity, and β-polysaccharide played a more important role in viscosity and microbial attachment than α-polysaccharide. Thus, viscosity plays a critical role in microbial attachment, and high viscosity and PS content result in high microbial attachment, which is beneficial to the granulation process of AGS.

12599. 题目: Sewage sludge composting under semi-permeable film at full-scale: Evaluation of odour emissions and relationships between microbiological activities and physico-chemical variables
文章编号: N19081509
期刊: Environmental Research
作者: T. Robledo-Mahón, M.A. Martín, M.C. Gutiérrez, M. Toledo, I. González, E. Aranda, A.F. Chica, C. Calvo
更新时间: 2019-08-15
摘要: In the present study, physico-chemical characteristics, heavy metals content, odour emissions, microbial enumeration and enzymatic activities were analysed during industrial scale composting of sewage sludge partially pre-treated to evaluate the effect of a combined system of semi-permeable film and aeration on these parameters. The results related to physico-chemical parameters showed a decrease in total organic carbon (TOC), organic matter (OM), total carbon (TC) along the process. Volatile solids (VS) were also reduced, reaching 36% at 120 days, which is above the limit according to the current legislation. Similarly, metal content was found to be an important variable in the evolution of enzymatic activity, while lead (Pb), zinc (Zn), and nickel (Ni) were the most influential. Moreover, heavy metals were found below the limit of type B compost quality or European class 2 at the end of the process, which is suitable for agriculture soil. The odorous impact generated during the hydrolytic stage was reduced to an average value of 4 ouE/s. This suggests that, covered stage with the semi-permeable film, could be a viable solution to mitigate odour emissions. The highest temperature was reached at 10 days and it was favoured by semi-permeable film. Temperature promoted the presence of thermophilic bacteria and fungi and indicated an early biodegradation process mediated by microorganisms. Statistical analyses revealed a high correlation of physico-chemical variables with microbial activity. Thus, samples from the first 14 days were highly correlated with enzymatic activities such as β-glucosidase (Ac-βGlu), protease (Ac-Pr), and dehydrogenase (Ac-De), which have usually been involved in the hydrolysis of organic matter.

12600. 题目: Coupling carbon metabolism and dissolved organic carbon fluxes in benthic and pelagic coastal communities
文章编号: N19081508
期刊: Estuarine, Coastal and Shelf Science
作者: Luis G. Egea, Cristina Barrón, Rocío Jiménez–Ramos, Ignacio Hernández, Juan José Vergara, José Lucas Pérez–Lloréns, Fernando G. Brun
更新时间: 2019-08-15
摘要: The knowledge of the production and carbon transference dynamics between adjacent communities is essential to gain a better understanding on the role of coastal areas in the global carbon cycle. Here, we assess the carbon metabolism (through dissolved oxygen –DO– concentration) and the net dissolved organic carbon (DOC) fluxes for benthic (dominated by the seagrass Cymodocea nodosa, the rhizophytic green algae Caulerpa prolifera and unvegetated sediments) and pelagic plankton communities cohabiting the same shallow coastal area in Cadiz Bay, southern Spain. Both the seagrass and macroalgae meadows were highly autotrophic, but the carbon metabolism of C. prolifera community shifted seasonally from net autotrophic to net heterotrophic. Unvegetated benthic communities were slightly heterotrophic throughout the year, while plankton community was net autotrophic. This study reveals how the different components of the ecosystem (i.e. macrophyte, sediment or plankton community) may have a seasonal variability in the contribution to the NCP in shallow coastal areas. Moreover, our results suggest that pelagic communities can be essential to maintain autotrophy of coastal system during periods of low benthic productivity. Regarding DOC, benthic communities were net DOC producers, undergoing a marked seasonality with maximum net DOC production during summer. This indicated an extra carbon assimilation not usually contemplated in productivity studies, which entails an underestimation of gross production in these communities. A strong relationship between net DOC flux and net community production (NCP) was found for the three benthic communities. The plankton community was a net DOC consumer indicating a strong coupling between the benthic and pelagic compartments in the bay. When upscaling our results to the whole bay, the NCP estimated for the benthos was 8800 ± 3770 Tons C y−1, and the net DOC flux was 2465 ± 830 Tons C y−1, which were mainly due to vegetated communities, indicating the importance of coastal vegetated benthic ones in the carbon metabolism and DOC fluxes.
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