论文检索

总访问量：2736030次

总访客量：122959人

所有论文

26021. 题目: Human and veterinary antibiotics during composting of sludge or manure: Global perspectives on persistence, degradation, and resistance genes
文章编号: N18072503
期刊: Journal of Hazardous Materials
作者: Amine Ezzariai, Mohamed Hafidi, Ahmed Khadra, Quentin Aemig, Loubna El Fels, Maialen Barret, Georges Merlina, Dominique Patureau, Eric Pinelli
更新时间: 2018-07-25
摘要: Wastewater treatment plant effluent, sludge and manure are the main sources of contamination by antibiotics in the whole environment compartments (soil, sediment, surface and underground water). One of the major consequences of the antibiotics discharge into the environment could be the prevalence of a bacterial resistance to antibiotic. In this review, four groups of antibiotics (Tetracyclines, Fluoroquinolones, Macrolides and Sulfonamides) were focused for the background on their wide spread occurrence in sludge and manure and for their effects on several target and non-target species. The antibiotics concentrations range between 1 and 136,000 μg kg^-1 of dry matter in sludge and manure, representing a potential risk for the human health and the environment. Composting of sludge or manure is a well-known and used organic matter stabilization technology, which could be effective in reducing the antibiotics levels as well as the antibiotic resistance genes. During sludge or manure composting, the antibiotics removals range between 17-100%. The deduced calculated half-lives range between 1 to 105 days for most of the studied antibiotics. Nevertheless, these removals are often based on the measurement of concentration without considering the matter removal (lack of matter balance) and very few studies are emphasized on the removal mechanisms (biotic/abiotic, bound residues formation) and the potential presence of more or less hazardous transformation products.
图文摘要:

26022. 题目: Seasonality alters drivers of soil enzyme activity in subalpine grassland soil undergoing climate change
文章编号: N18072502
期刊: Soil Biology and Biochemistry
作者: Jérémy Puissant, Vincent E.J. Jassey, Robert T.E. Mills, Bjorn J.M. Robroek, Konstantin Gavazov, Sebastien De Danieli, Thomas Spiegelberger, Robert Griffiths, Alexandre Buttler, Jean-Jacques Brun, Lauric Cécillon
更新时间: 2018-07-25
摘要: In mountain ecosystems with marked seasonality, climate change can affect various processes in soils, potentially modifying long-term key soil services via change in soil organic carbon (C) storage. Based on a four-year soil transplantation experiment in Swiss subalpine grasslands, we investigated how imposed climate warming and reduced precipitation modified the drivers of soil carbon enzyme potential activities across winter and summer seasons. Specifically, we used structural equation models (SEMs) to identify biotic (microbial community structure, abundance and activity) and abiotic (quantity and quality of organic matter resources) drivers of soil C-enzymes (hydrolase and oxidase) in two seasons under two different climate scenarios. We found contrasting impacts of the climate manipulation on the drivers of C-enzymes between winter and summer. In winter, no direct effect of climate manipulation (reduced rainfall and warming) on enzyme activity was observed. Yet, climate indirectly down-regulated enzyme activity through a decrease in the availability of water extractable organic carbon (WEOC) labile resources. During summer, reduced soil moisture –induced by the climate manipulation– directly reduced soil microbial biomass, which led to a decrease in C-enzyme activity. In general, across both seasons, neither microbial community structure, nor organic matter quality were strong determinants of enzymatic activity. In particular organic matter recalcitrance (aromaticity) was not found as a general driver of either hydrolase or oxidase C-enzyme potential activities, though we did observe higher C-enzyme activities led to an increase of particulate organic matter recalcitrance in the summer season. Overall, our results highlight the seasonality of climate change effects on soil organic matter enzymatic decomposition, providing a comprehensive picture of seasonal potential cause and effect relationships governing C mineralization in subalpine grasslands.

26023. 题目: Long-term performance of biological ion exchange for the removal of natural organic matter and ammonia from surface waters
文章编号: N18072501
期刊: Water Research
作者: Nargess Amini, Isabelle Papineau, Veronika Storck, Pierre R. Bérubé, Madjid Mohseni, Benoit Barbeau
更新时间: 2018-07-25
摘要: Anionic exchange is an effective treatment option for the removal of natural organic matter from surface waters. However, the management of the spent brine regenerant often limits the adoption of this process. The current study reports one year of operation of ion exchange resins under biological mode (BIEX, i.e. without regeneration to promote biofilm growth on the media) compared to the performance of (i) ion exchange with weekly regeneration (IEX), (ii) granular activated carbon under biological mode (BAC) and (ii) granular activated carbon under adsorption mode (GAC). Four parallel pilot filters (GAC, BAC, IEX and BIEX) were fed with a colored and turbid river water without pretreatment. Although IEX provided the best performance (80% DOC removal) throughout the study, BIEX achieved a similar performance to IEX prior to DOC breakthrough (92 days) and subsequently achieved a mean DOC removal of 62% in warm water conditions. The GAC filter was rapidly exhausted (2 weeks) while the BAC filter only provided a 5% DOC reduction. Full nitrification was observed on both the BIEX and BAC filters under warm water conditions (>15 °C). After one year of operation, BIEX was successfully regenerated with brine. According to a mass balance, 69% of DOC removal in BIEX was due to ion exchange while we assume the remainder was biodegraded. Operation of ion exchange in biological mode is a promising option to reduce spent brine production while still achieving high DOC removal.
图文摘要:

26024. 题目: Effects of short- and long-term exposures of humic acid on the Anammox activity and microbial community
文章编号: N18072437
期刊: Environmental Science and Pollution Research
作者: Khadija Kraiem, Mohamed Ali Wahab, Hamadi Kallali, Andrea Fra-vazquez, Alba Pedrouso, Anuska Mosquera-Corral, Naceur Jedidi
更新时间: 2018-07-24
摘要: Humic acid has a controversial effect on the biological treatment processes. Here, we have investigated humic acid effects on the Anammox activity by studying the nitrogen removal efficiencies in batch and continuous conditions and analyzing the microbial community using Fluorescence in situ hybridization (FISH) technique. The results showed that the Anammox activity was affected by the presence of humic acid at a concentration higher than 70 mg/L. In fact, in the presence of humic acid concentration of 200 mg/L, the Anammox activity decreased to 57% in batch and under continuous condition, the ammonium removal efficiencies of the reactor decreased from 78 to 41%. This reduction of Anammox activity after humic acid addition was highlighted by FISH analysis which revealed a considerable reduction of the abundance of Anammox bacteria and the bacteria living in symbiosis with them. Furthermore, a total inhibition of Candidatus Brocadia fulgida was observed. However, humic acid has promoted heterotrophic denitrifying bacteria which became dominant in the reactor. In fact, the evolution of the organic matter in the reactor showed that the added humic acid was used as carbon source by heterotrophic bacteria which explained the shift of metabolism to the favor of heterotrophic denitrifying bacteria. Accordingly, humic acid should be controlled in the influent to avoid Anammox activity inhibition.

26025. 题目: Molecular insights into reversible redox sites in solid-phase humic substances as examined by electrochemical in situ FTIR and two-dimensional correlation spectroscopy
文章编号: N18072436
期刊: Chemical Geology
作者: Yong Yuan, Xixi Cai, Bin Tan, Shungui Zhou, Baoshan Xing
更新时间: 2018-07-24
摘要: Solid-phase humic substances (also termed humins, HMs) are the largest fraction of humic substances (HSs) in soils and sediments, which are recently shown to be capable of mediating electron transfer in many key biogeochemical processes. However, the redox properties of HMs remains poorly investigated, likely due to their structural complexity and the lack of efficient methodology. Herein, an electrochemical in situ FITR spectroscopic (EC-FTIRS) technique coupled with two-dimensional correlation spectroscopy (2D-COS) was employed for the first time to study the redox process of complex HMs at a molecular level. In situ FTIR identified that the IR bands of quinone and phenolic moieties in the HMs were potential dependent, suggesting that they were the main redox sites in response to the redox transformation of the HMs. Meanwhile, In situ FTIR characterizations showed that the significant variations in IR bands positioned at ~1500 and ~1470 cm^-1 in response to the applied potentials, providing evidence for the presence of quinone radical and dianion intermediates during the redox process. The 2D-COS analysis was used to further explore variations in infrared intensities as a function of the potentials applied to reduce or oxidize the HMs, which indicated the occurrence of the typical redox reactions of quinone in the HMs. These results improve our understanding on the redox mechanism of HMs at the molecular level and have significant implication for in-depth understanding of biogeochemical processes.
图文摘要:

26026. 题目: EPS adsorption to goethite: Molecular level adsorption mechanisms using 2D correlation spectroscopy
文章编号: N18072435
期刊: Chemical Geology
作者: Peng Cai, Di Lin, Caroline L. Peacock, Wanxi Peng, Qiaoyun Huang
更新时间: 2018-07-24
摘要: The adsorption of extracellular polymeric substances (EPS) onto soil minerals is an important process for understanding bacterial adhesion to mineral surfaces and environmental cycling of nutrients and contaminants. To clarify the molecular level mechanisms and processes of EPS adsorption, the interaction mechanisms between EPS and goethite was explored using two-dimensional (2D) Fourier transformation infrared (FTIR) correlation spectroscopy (CoS) assisted by C 1s near edge X-ray absorption fine structure spectroscopy (NEXAFS). Results show that the amide functional groups of EPS play an important role in its adsorption on goethite, and the adsorption of EPS-proteins on goethite is a function of electrolyte concentration, with increasing adsorption at a higher electrolyte concentration. Results also show that the order in which the EPS functional groups interact and bind with goethite is dependent on electrolyte concentration, where carboxyl and phosphoryl functional groups are the first to adsorb at low electrolyte concentration, while amide groups are the first to adsorb at higher electrolyte concentration. Deconvolution and curve fitting of the amide I band at the end of the adsorption process (~300 min) shows that the secondary structure of proteins is converted from a random coil conformation to aggregated strands, α-helices and turns. This conversion leads to increased adsorption of EPS-proteins and explains the overall adsorption increase of EPS on goethite surfaces with an increasing concentration of electrolyte. Furthermore, the adsorption of the carboxyl functional groups of EPS decreases with increasing electrolyte concentration, likely due to more effective screening of the goethite surface charge with increasing concentration of electrolyte. The integrated results from ATR-FTIR and 2D-CoS allow us to construct a comprehensive overview of EPS-goethite interaction processes at the molecular level, which can be used to improve our understanding of EPS-mineral interactions in the natural environment. These results also provide fundamental information for a better understanding of bacterial biofilm formation on soil and sediment minerals, and facilitate research on the subsequent interaction of nutrients and contaminants with the reactive constituents of biofilms in natural and contaminated environments.
图文摘要:

26027. 题目: Soil organic carbon storage as a key function of soils - A review of drivers and indicators at various scales
文章编号: N18072434
期刊: Geoderma
作者: Martin Wiesmeier, Livia Urbanski, Eleanor Hobley, Birgit Lang, Margit von Lützow, Erika Marin-Spiotta, Bas van Wesemael, Eva Rabot, Mareike Lie?, Noelia Garcia-Franco, Ute Wollschl?ger, Hans-J?rg Vogel, Ingrid K?gel-Knabner
更新时间: 2018-07-24
摘要: The capacity of soils to store organic carbon represents a key function of soils that is not only decisive for climate regulation but also affects other soil functions. Recent efforts to assess the impact of land management on soil functionality proposed that an indicator- or proxy-based approach is a promising alternative to quantify soil functions compared to time- and cost-intensive measurements, particularly when larger regions are targeted. The objective of this review is to identify measurable biotic or abiotic properties that control soil organic carbon (SOC) storage at different spatial scales and could serve as indicators for an efficient quantification of SOC. These indicators should enable both an estimation of actual SOC storage as well as a prediction of the SOC storage potential, which is an important aspect in land use and management planning. There are many environmental conditions that affect SOC storage at different spatial scales. We provide a thorough overview of factors from micro-scales (particles to pedons) to the global scale and discuss their suitability as indicators for SOC storage: clay mineralogy, specific surface area, metal oxides, Ca and Mg cations, microorganisms, soil fauna, aggregation, texture, soil type, natural vegetation, land use and management, topography, parent material and climate. As a result, we propose a set of indicators that allow for time- and cost-efficient estimates of actual and potential SOC storage from the local to the regional and subcontinental scale. As a key element, the fine mineral fraction was identified to determine SOC stabilization in most soils. The quantification of SOC can be further refined by including climatic proxies, particularly elevation, as well as information on land use, soil management and vegetation characteristics. To enhance its indicative power towards land management effects, further “functional soil characteristics”, particularly soil structural properties and changes in the soil microbial biomass pool should be included in this indicator system. The proposed system offers the potential to efficiently estimate the SOC storage capacity by means of simplified measures, such as soil fractionation procedures or infrared spectroscopic approaches.

26028. 题目: Applications and factors influencing of the persulfate-based advanced oxidation processes for the remediation of groundwater and soil contaminated with organic compounds
文章编号: N18072433
期刊: Journal of Hazardous Materials
作者: Yaoyu Zhou, Xiang Yujia, He Yangzhuo, Yang Yuan, Zhang Jiachao, Luo Lin, Peng Hui, Dai Chunhao, Zhu Feng, Tang Lin
更新时间: 2018-07-24
摘要: Persulfate is the latest oxidant which is being used increasingly for the remediation of groundwater and soil contaminated with organic compounds. It is of great significant to offer readers a general summary about different methods of activating persulfate, mainly including heat-activated, metal ions-activated, UV-activated, and alkaline-activated. Meanwhile, in addition to persulfate concentration as an influencing factor for persulfate oxidation process, selected information like temperature, anions, cations, pH, and humic acid are presented and discussed. The last section focuses on the advantages of different activated persulfate processes, and the suggestions and research needs for persulfate-based advanced oxidation in the remediation of polluted groundwater and soil.
图文摘要:

26029. 题目: Response of treatment performance and microbial community structure to the temporary suspension of an industrial anaerobic bioreactor
文章编号: N18072432
期刊: Science of The Total Environment
作者: Xianchao Qin, Mengmeng Ji, Xiaogang Wu, Chunjie Li, Yueshu Gao, Ji Li, Qiaoyu Wu, Xiaojun Zhang, Zhenjia Zhang
更新时间: 2018-07-24
摘要: In this study, a novel type of mesophilic anaerobic bioreactor—an expanded granular sludge bed (EGSB)—was utilized to explore the effect of suspending reactor operation on the treatment performance and the microbial community structure. The parameters of performance and bacterial community before and after a four-week suspension were compared for the starch processing wastewater treatment bioreactor. The results indicate that the removal rate of the organic matter remained higher than 90%, although the biomass significantly decreased after restarting the reactor. However, the relatively stable microbial community structure before the suspension was altered significantly during the restart and post-running stages. This change was primarily due to variability in satellite species and the substitution effect of different dominant bacteria. For example, some non-major carbohydrate-degrading bacteria that were sensitive to nutrition deficiency, such as Desulfovibrio and Geobacter, were dramatically reduced after the suspension. In contrast, the stress of starvation stimulated the reproduction of hydrolytic bacteria, such as Macellibacteroides. However, the high bacterial diversity index (6.12–6.65) and the longstanding core species, including Chloroflexi, Cloacimonetes, Ignavibacteriae, Thermotogae and Euryarchaeota, maintained the functional stability of the reactor. Consequently, although the total bacteria decreased significantly after reactor operation was suspended, sufficient functional bacteria supported by the high diversity, as well as the longstanding core species, guaranteed the effective degradation after suspension.
图文摘要:

26030. 题目: Recent changes in chironomid communities and hypolimnetic oxygen conditions relate to organic carbon in subarctic ecotonal lakes
文章编号: N18072431
期刊: Science of The Total Environment
作者: Tomi P. Luoto, Marttiina V. Rantala, E. Henriikka Kivil?, Liisa Nevalainen
更新时间: 2018-07-24
摘要: A key question in aquatic elemental cycling is related to the influence of bottom water oxygen conditions in regulating the burial and release of carbon under climate warming. In this study, we used head capsules of Chironomidae larvae to assess community and diversity change between the past (estimated as Pre-Industrial Period) and present and to reconstruct changes in hypolimnetic oxygen conditions from 30 subarctic ecotonal lakes (northeastern Lapland) using the top-bottom paleolimnological approach applying surface sediment (topmost 0–2 cm) and reference (4–5 cm) samples. Subsequently, we tested the findings against dissolved organic carbon (DOC) concentration of the sites. We found that the benthic communities were statistically dissimilar between the past and the present with largest changes occurring in the more transparent oligo-mesohumic lakes. However, murky polyhumic lakes displayed uniformly a decrease in diversity. The chironomid-inferred oxygen values showed a general decrease toward the present with largest shifts in low-DOC lakes, whereas no significant changes were found in the hypolimnetic oxygen conditions of high-DOC lakes, which were often located in wetland areas. These finding suggest that lakes associated with constant organic carbon inputs are more resilient toward climate-induced reductions in hypolimnetic oxygen.
图文摘要:

26031. 题目: Degradation of petroleum hydrocarbons in seawater by simulated surface-level atmospheric ozone: Reaction kinetics and effect of oil dispersant
文章编号: N18072430
期刊: Marine Pollution Bulletin
作者: Haodong Ji, Yanyan Gong, Jun Duan, Dongye Zhao, Wen Liu
更新时间: 2018-07-24
摘要: Oil degradation by surface-level atmospheric ozone has been largely ignored in the field. To address this knowledge gap, this study investigated the ozonation rate and extent of typical petroleum compounds by simulated surface-level ozone, including total petroleum hydrocarbons (TPHs), n-alkanes, and polycyclic aromatic hydrocarbons (PAHs). Moreover, the work explored the effect of a prototype oil dispersant, Corexit EC9500A, on the ozonation rate. Rapid oxidation of TPHs, n-alkanes and PAHs was observed at various gaseous ozone concentrations (i.e. 86, 200 and 300 ppbv). Generally, the presence of the oil dispersant enhanced ozonation of the oil compounds. The addition of humic acid inhibited the reaction, while increasing salinity accelerated the degradation. Both direct ozonation by molecular ozone and indirect oxidation by ozone-induced radicals play important roles in the degradation process. The findings indicate that ozonation should be taken into account in assessing environmental fate and weathering of spilled oil.
图文摘要:

26032. 题目: Monocyclic aromatic hydrocarbons (phthalates and BTEX) and aliphatic components in the SE Mediterranean costal Sea-surface microlayer (SML): Origins and phase distribution analysis
文章编号: N18072429
期刊: Marine Chemistry
作者: Peleg Astrahan
更新时间: 2018-07-24
摘要: Coastal waters are subject to many sources of organic matter, such as land runoff, industrial and urban waste, rivers and atmospheric depositions. Semi-volatile organic compounds (SVOC) are frequently found next to coastal and urban areas. Depending on the specific physical properties of each compound in the SVOC group, these compounds may be adsorbed to particulate matter, evaporate to the atmosphere or accumulate in the sea's uppermost layer - the Sea surface microlayer (SML). Since many of these compounds present health risks, understanding the mechanisms that control the SVOC environmental concentration is crucial, especially in coastal waters.

26033. 题目: Litter crusts promote herb species formation by improving surface microhabitats in a desert ecosystem
文章编号: N18072428
期刊: CATENA
作者: Chao Jia, Ze Huang, Hai-Tao Miao, Rong Lu, Jianjun Li, Yu Liu, Weibo Shen, Honghua He, Gao-Lin Wu
更新时间: 2018-07-24
摘要: The degradation of soil and vegetation substantially damages ecosystem functions. Litter crusts play an active role in the vegetation restoration and management in desert ecosystems. In this study, the effects of litter crusts on surface microhabitats and species formation on sandy land were studied in the wind-water erosion crisscross region in the Mu Us Desert, northwest China. Soil microhabitat features including moisture, temperature, and organic matter content were measured in different positions of litter crusts and bare sand, seedling species richness, and total seedling number of all species were recorded in litter crusts on the sand's surface. The results showed that there were significant differences between litter crusts and bare sand in terms of soil moisture, temperature, organic matter content, and light intensity. Compared with that of bare sand, soil moisture below litter crusts was increased by an average of 17.0% overall, soil organic matter content was increased by 77.5% at the 0–5 cm depth and by 80.8% at the 5–10 cm depth. Litter crusts decreased soil temperature and light intensity by an average of 16.6% and 31.6%, respectively. Seedling species richness and total seedling number of all species were significantly higher in litter crusts than those in bare sand. Our findings revealed that litter crusts modify the surface microhabitats of sand by maintaining soil moisture, regulating soil temperature, increasing soil nutrients, and reducing light intensity, thus promoting species establishment in the wind-water erosion crisscross region.

26034. 题目: Novel insights into variation of fluorescent dissolved organic matters during antibiotic wastewater treatment by excitation emission matrix coupled with parallel factor analysis and cosine similarity assessment
文章编号: N18072427
期刊: Chemosphere
作者: Jiukai Tang, Jing Wu, Zhonghua Li, Cheng Cheng, Bo Liu, Yidi Chai, Yongjun Wang
更新时间: 2018-07-24
摘要: In this work, the variation of fluorescent dissolved organic matters (FDOM) of antibiotic wastewater in a full-scale treatment plant was studied. Fluorescent components of anaerobic, aerobic, Fenton stages were separately figured out by parallel factor analysis (PARAFAC) based on excitation emission matrix (EEM) dataset. Then, these components were pairwise quantitatively compared according to cosine similarity (CS). It was found that, after the anaerobic treatment, the major components showed remarkable similarity (CS > 0.97) to those of raw wastewater, although their maximum fluorescence intensity (F_max) decreased slightly or moderately (7% 54%). However, the aerobic treatment dramatically changed both the composition and content of fluorescent components, as all the protein-like components completely disappeared and only the humic-like components with much lower intensity were observed. After Fenton oxidation, all these humic-like components were remained (CS > 0.97) with fairly reduced F_max (51% 61%). For both aerobically treated and Fenton-oxidized wastewater, F_max correlated well with dissolved organic carbon (DOC). This suggested a dominant proportion of humic-like substances. The combination of PARAFAC based on separate EEM dataset of each treatment stage and CS assessment is a good approach to better understand FDOM variation and can be of much practical significance to monitor wastewater quality.

26035. 题目: Sources and fate of organic matter in constructed versus natural coastal waterways
文章编号: N18072426
期刊: Marine Pollution Bulletin
作者: Kylie A. Pitt, Shin Yip Lee, Rod M. Connolly, Thi Hong Hanh Bui, Nic Doriean
更新时间: 2018-07-24
摘要: Coastal wetlands are increasingly being converted into canal estates with potential consequences for ecosystem functioning. We compared the sources and fate of organic matter and water quality at four types of canal habitats (entrances and ends of canals, canal lakes and lake edges) and shallow and deep natural habitats (four replicates of each habitat). The fate of labile organic matter was assessed by measuring rates of scavenging of carrion. Surface sediments were analysed for organic carbon content and stable carbon isotopes, fatty acid biomarkers and compound specific stable isotope analysis of selected fatty acids were used to elucidate sources of sedimentary organic matter. Canal lakes differed from other habitats and were characterised by negligible scavenging, larger quantities of organic matter comprised of higher contributions from diatoms, and hypoxia. Despite some trends, natural habitats were statistically indistinguishable from canal entrances and ends. Variation among replicate habitats was large.

26036. 题目: Global and regional variations in tropical marine environments of Gondwana as revealed by a multi-stable isotope study, Middle Triassic (Anisian), Israel, Levant Basin
文章编号: N18072425
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: A. Schneider-Mor, T. Zilberman, D. Korngreen
更新时间: 2018-07-24
摘要: The world during the early Middle Triassic (Anisian) was characterized by a distinct recovery of the carbonate factory after the Permian–Triassic crisis. This recovery seems to have passed over the Anisian environment on the tropical northern margin of Gondwana (Israel, Levant Basin) and to have resulted in the low diversity of barren horizons of carbonate-secreting organisms. Four Anisian successions (the Ramon 1, Hameishar 1, Nafha 1, and David 1 boreholes) were studied to decode the factors preventing regional recovery. A multi-proxy analysis was performed on these boreholes, including the carbonate/siliciclastic ratio, total organic carbon (TOC), carbon/nitrogen (C/N) ratio and inorganic carbon (δ¹³C_carb), oxygen (δ¹⁸O_carb), and nitrogen (δ¹⁵N) isotopic compositions. The aim of assessing the combination of these proxies was to characterize the geochemical conditions in the regional basins. These successions record two C-cycle perturbation events, characterized by negative shifts in δ¹³C_carb values and recognized in most successions, indicating the land-marine teleconnection effect on the C-cycle perturbation. The δ¹⁸O_carb excursions revealed similar oscillation trends, with global warming evidenced by increasing circumtropical precipitation and terrestrial influxes, whereas global cooling was reflected by increased carbonate factory production. The low δ¹⁵N values in all of the studied successions indicated the presence and flourishing of N-fixers. The absence or scarcity of carbonate-secreting organisms suggests that these N-fixers were the source of the carbonate fraction in the sediments. Episodic events with high δ¹⁵N values suggest an accumulation of terrestrial organic matter (OM) or oxygenation events, allowing short-term colonization by benthic fauna at the marine sites.

26037. 题目: Separated pathways for biochar to affect soil N₂O emission under different moisture contents
文章编号: N18072424
期刊: Science of The Total Environment
作者: Zhengjun Feng, Yaqi Sheng, Fei Cai, Wei Wang, Lizhong Zhu
更新时间: 2018-07-24
摘要: Dry land is a massive contributor to global nitrous oxide (N₂O) production and biochar is a potential material for soil amendment that can impact soil N₂O emission. Considering that the moisture content of dry land is usually changeable, it is essential to investigate the effect of biochar on soil N₂O emission under different moisture contents. Therefore, column experiments were conducted with two biochars (B300 and B500, biochars pyrolyzed at 300 and 500 °C, respectively) under five moisture contents (18%, 21%, 24%, 27% and 30%, w/w). The results showed that B300 promoted N₂O emission under the moisture contents of 18%, 21% and 24% by increasing the content of dissolved organic carbon and thus enhancing the microbial processes related to N₂O production. However, when the moisture contents were 27% and 30%, the promotion of N₂O production was overwhelmed by the improvement in N₂O reduction due to the B300 induced increase in the abundance ratio of nosZ to nirS, leading to the decrease in N₂O emission. Moreover, B500 did not alter the content of dissolved organic matter significantly and thus caused no significant change in N₂O emission when the moisture contents were 18%, 21% and 24%. But it was able to increase the abundance ratio of nosZ to nirS and thus decrease N₂O emission when the moisture contents were 27% and 30%. The results further clarified the effect of biochar on soil N₂O emission and helped to evaluate the N₂O-suppressing-potential of biochar.
图文摘要:

26038. 题目: How good are the predictions of mobility of aged polychlorinated biphenyls (PCBs) in soil? Insights from a soil column experiment
文章编号: N18072423
期刊: Science of The Total Environment
作者: Chiara Maria Vitale, Elisa Terzaghi, Dario Zati, Antonio Di Guardo
更新时间: 2018-07-24
摘要: A column leaching experiment was performed to evaluate the influence of some relevant environmental factors (soil/water contact time, temperature, saturation) on mobility of aged polychlorinated biphenyls (PCBs) in soil together with transport mediated by dissolved organic carbon (DOC) and mobile organic carbon (OC) coated fine particles/colloids. Consecutive fractions of leachates were collected after a variable pre-equilibration time (2, 5, 7, 48 days), using leaching solutions with different DOC content (tap water vs. Aldrich humic acid), in saturated vs. field capacity conditions and at different temperatures (25 °C vs. 15 °C). The data obtained were compared to the predicted values using a multimedia model (SoilPlusVeg) to evaluate model behaviour. Contact time and temperature determined a relevant effect on DOC and particle/colloid availability, with significant variations in leachate concentrations (up to 1 order of magnitude), typically overlooked by most environmental fate models. Results obtained at different temperatures show a modulation of the DOC/particles production with temperature and therefore the role of temperature changes in the environmental scenarios (e.g. seasonal variations). Transport of PCBs enhanced by Aldrich DOC was not linearly correlated to chemical hydrophobicity but revealed a threshold to ~Log K_OW 6.5, likely because of the slow sorption kinetics of more hydrophobic chemicals. Additionally, variation of the saturation conditions (e.g. drying-wetting cycles) can determine contamination peaks at the beginning of an irrigation/rainfall event because of the soil/water equilibration. Model simulations, even when including DOC in the water phase, but not accounting for the particle/colloidal transport and sorption/desorption kinetics, mismatched the ratio of dissolved vs. DOC-associated and particle-associated PCBs and substantially underpredicted concentrations, especially for the high chlorinated congeners. The results indicated that some of the common assumptions and paradigms in fate modelling of such hydrophobic compounds should be revisited and models updated.
图文摘要:

26039. 题目: Spatiotemporal variability of hydrocarbons in surface sediments from an intensively human-impacted Xiaoqing River-Laizhou Bay system in the eastern China: Occurrence, compositional profile and source apportionment
文章编号: N18072422
期刊: Science of The Total Environment
作者: Ding He, Kai Zhang, Xingqian Cui, Jianhui Tang, Yongge Sun
更新时间: 2018-07-24
摘要: Hydrocarbons in coastal sediments record organic matter sources, and thus are widely used to elucidate both natural and anthropogenic inputs and for the estimation of pollution levels. Surface sediments were taken from Xiaoqing River and Laizhou Bay of eastern China in spring and summer of 2014, and were analyzed to determine the characteristics of aliphatic and aromatic hydrocarbons. Various hydrocarbons were identified, including n-alkanes, monomethylated alkanes (MMAs), isoprenoid alkanes, linear alkylbenzenes (LABs), hopanes, steranes and polycyclic aromatic hydrocarbons (PAHs). They were used to track both biogenic (terrestrial plant and microbial inputs) and anthropogenic inputs (petroleum and fossil fuel or biomass burning) in this ecosystem. The major part of hydrocarbons identified came from anthropogenic inputs including petroleum residues and synthetic detergents related hydrocarbons (16.2–90.3%), followed by higher plant (4.5–80.5%) and microbial inputs (0.8–57.5%). Interestingly, significant differences in hydrocarbon concentrations and distributions were observed between spring and summer. In particular, significant higher percentages of microbially derived hydrocarbons, but lower percentages of anthropogenic and vascular plant derived hydrocarbons were observed in summer than spring. Further principal component analyses suggested that the overall distribution of aliphatic hydrocarbons was mainly controlled by seasonality instead of spatiality. In contrast, the distribution of PAHs showed insignificant spatial and seasonal differences. Physical processes such as atmospheric transportation and further deposition, may be factors influencing the distribution of PAHs in the study area with widely biomass and fossil fuel burning. The decoupled distributions of aliphatic and aromatic hydrocarbons warrant further study for a comprehensive understanding of long term sedimentary hydrocarbon sources and input dynamics with increasing human activities.
图文摘要:

26040. 题目: Controls on high and low groundwater arsenic on the opposite banks of the lower reaches of River Ganges, Bengal basin, India
文章编号: N18072421
期刊: Science of The Total Environment
作者: Abhijit Mukherjee, Alan E. Fryar, Emily M. Eastridge, Rachel S. Nally, Madhumita Chakraborty, Bridget R. Scanlon
更新时间: 2018-07-24
摘要: Understanding the controls on spatial variability of groundwater arsenic (As) is critical for mitigating As contamination. The objective of this study is to determine controls on previously unexplained differences in groundwater As concentrations, which are high along the east bank and low along the west bank of the River Bhagirathi-Hoogly (B-H), the primary Indian distributary of the River Ganges, on the western margin of the Bengal basin. A total of 54 wells were sampled after the monsoon season at four sites (two each east and west of the B-H) in Murshidabad district, West Bengal, for field parameters, major and minor solutes, and stable isotopes of water. An additional four boreholes were drilled for analyses of sediment texture, mineralogy, total organic and inorganic carbon, and total As and other metal(loid)s. Results show that higher As in east-bank groundwater (median 0.031 mg/L) is associated with generally more anoxic conditions (higher median total Fe and lower median E_H and NO₃ ) relative to west-bank groundwater (median As < 0.001 mg/L), consistent with previous studies. In contrast, concentrations of Mn in the study area are highest in west-bank wells near the B-H. Carbonate and silicate weathering appear to be more important in east- and west-bank groundwater, respectively, which may reflect differences in sediment sources. Ranges of total As are similar in east- and west-bank sediments. Relatively depleted values of δ¹⁸O and δ²H in the east-bank aquifer and streams appear to reflect focused recharge through paleochannels, while relatively enriched west-bank values suggest diffuse recharge to upland aquifers. We speculate that water infiltrating through erosional, stratigraphic “windows” carries organic matter capable of mobilizing As in east-bank groundwater. This comprehensive evaluation of groundwater chemistry provides a more detailed understanding of controls on As variability within the basin.
图文摘要: