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30661. 题目: Influence of earthworm bioturbation on metals phytoavailability and human gastric bioaccessibility
文章编号: N18082508
期刊: Environmental Science and Pollution Research
作者: Thibaut Lévêque, Camille Dumat, Laura Lagier, Eva Schreck, Jenny Ruales, Yvan Capowiez
更新时间: 2018-08-25
摘要: At the global scale, urban agriculture is increasingly developing in cities due to demographic growth and sustainable food concerns. But, urban soils are frequently polluted with metals. In urban gardens, organic matter is also commonly added both to valorize organic household waste and to promote biophysicochemical fertility. As earthworms promote the decomposition and the recycling of soil organic matter, they can also influence the biogeochemical cycle of metals in urban polluted soils. In order to produce safe vegetables in urban areas, it is crucial to highlight the mechanisms involved in complex soil-earthworm-plant ecosystems. An experiment was set up to examine these relationships using lettuce cultivated in controlled conditions with RHIZOtest® devices. Thanks to the RHIZOtest® devices, metal transfer and bioaccessibility were for the first time compared for urban polluted soil without (1—urban soil polluted with Pb, Cd, Cu, and Zn: essential or toxic metals currently found in environment, SNB) and with bioturbation (2—this metal-polluted soil subjected to earthworm bioturbation, SB) and earthworm casts (3—earthworm casts produced in this polluted soil and naturally enriched in organic matter and microorganisms, T). Metal concentration, phytoavailability, and human gastric bioaccessibility were determined in the different samples. Results showed that earthworm bioturbation increased the phytoavailability of all the metals. For the experimental condition SB, the phytoavailability of metals was increased up to 75% compared to SNB. In addition, surprisingly, metal phytoavailability was always superior in SB compared to earthworm casts (T). Moreover, earthworms led to an increase in Zn gastric bioaccessibility up to 10% in the soils in the same way as for phytoavailability, meaning Zn bioaccessibility in SB > T > SNB, whereas it remained unchanged in the lettuces. These data are important to promote sustainable agriculture activities in urban areas; actually, databases concerning different experimental conditions are needed to develop decision support tools.

30662. 题目: Effects of multiple stressors on cyanobacteria abundance vary with lake type
文章编号: N18082507
期刊: Global Change Biology
作者: Jessica Richardson, Claire Miller, Stephen C. Maberly, Philip Taylor, Lidija Globevnik, Peter Hunter, Erik Jeppesen, Ute Mischke, S. Jannicke Moe, Agnieszka Pasztaleniec, Martin Søndergaard, Laurence Carvalho
更新时间: 2018-08-25
摘要: Blooms of cyanobacteria are a current threat to global water security that is expected to increase in the future because of increasing nutrient enrichment, increasing temperature and extreme precipitation in combination with prolonged drought. However, the responses to multiple stressors, such as those above, are often complex and there is contradictory evidence as to how they may interact. Here we used broad scale data from 494 lakes in central and northern Europe, to assess how cyanobacteria respond to nutrients (phosphorus), temperature and water retention time in different types of lakes. Eight lake types were examined based on factorial combinations of major factors that determine phytoplankton composition and sensitivity to nutrients: alkalinity (low and medium‐high), colour (clear and humic) and mixing intensity (polymictic and stratified). In line with expectations, cyanobacteria increased with temperature and retention time in five of the eight lake types. Temperature effects were greatest in lake types situated at higher latitudes, suggesting that lakes currently not at risk could be affected by warming in the future. However, the sensitivity of cyanobacteria to temperature, retention time and phosphorus varied among lake types highlighting the complex responses of lakes to multiple stressors. For example, in polymictic, medium‐high alkalinity, humic lakes cyanobacteria biovolume was positively explained by retention time and a synergy between TP and temperature, while in polymictic, medium‐high alkalinity, clear lakes only retention time was identified as an explanatory variable. These results show that, although climate change will need to be accounted for when managing the risk of cyanobacteria in lakes, a “one‐size fits‐all” approach is not appropriate. When forecasting the response of cyanobacteria to future environmental change, including changes caused by climate and local management, it will be important to take this differential sensitivity of lakes into account.

30663. 题目: Particle size dependence of the physicochemical properties of biochar
文章编号: N18082506
期刊: Chemosphere
作者: Pinjing He, Yuhao Liu, Liming Shao, Hua Zhang, Fan Lü
更新时间: 2018-08-25
摘要: The inadequate definition of different particle sizes of biochar impedes the establishment of guidelines concerning the selection of suitable particle sizes. In this study, various properties of a series of ten biochar samples of varying particle size (5–5000 μm) from the same origin have been investigated and compared. Cluster analysis and principal component analysis based on all of the parameters were executed to evaluate the dissimilarity of different particle sizes of biochar, and to classify the size ranges determining the relevant properties. The results showed that the series of ten biochar samples with different particle sizes could be separated into four groups, indicating that there were significant characteristic differences between different particle sizes of biochar. The greater the difference in particle size, the more disparate the properties. Moreover, 75–150 μm has been identified as a turning point along the continuous particle size range. A deviation in the properties of biochar particles smaller than 5 μm confirmed that different preparation methods would lead to highly significant differences between different particle sizes of biochar, even if the pristine materials were the same. The need for definition of the characteristics of biochar required for a specific environmental application should be emphasized.
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30664. 题目: Partitioning biochar properties to elucidate their contributions to bacterial and fungal community composition of purple soil
文章编号: N18082505
期刊: Science of The Total Environment
作者: Yang Li, Yanqi Yang, Fei Shen, Dong Tian, Yongmei Zeng, Gang Yang, Yanzong Zhang, Shihuai Deng
更新时间: 2018-08-25
摘要: Although effects of biochar application on soil microorganism have been increasingly reported, the direct evidences for demonstrating the contributions of biochar chemical and physical properties to soil microorganisms are still lacking. Herein, we partitioned corn-straw biochar (BC) into three fractions, including aqueous extractable substances (AE), organic extractable substances (OE) and the remaining solid (EBC) after these two extractions. These fractions and BC were added to purple soil for a 30-day incubation. Soil properties, microbial α-diversity indices and microbial community compositions were analysed after the incubation. The results showed the obvious changes in soil properties, along with higher available P, available K and total organic C, as well as, lower pH and available N than those of soil without biochar, were observed in the BC-treated soil. Illumina Miseq sequencing displayed a distinct difference between responses of bacteria and fungi to biochar application, in which fungal richness and diversity were increased, and no significant changes happened in bacterial richness. Furthermore, biochar had apparent effects on bacterial and fungal community compositions at phylum level, which were most close to the influences of AE and EBC, respectively. These results suggested that AE, improving soil nutrients (e.g., total N), played a pivotal role in changing bacterial phylum community composition. The EBC, regarded as physical structure and relatively recalcitrant compounds of BC, had a dominant contribution to the influence of biochar on the fungal community composition.
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30665. 题目: Determining the sources of nutrient flux to water in headwater catchments: Examining the speciation balance to inform the targeting of mitigation measures
文章编号: N18082504
期刊: Science of The Total Environment
作者: C.E.M. Lloyd, P.J. Johnes, J.E. Freer, A.M. Carswell, J.I. Jones, M.W. Stirling, R.A. Hodgkinson, C. Richmond, A.L. Collins
更新时间: 2018-08-25
摘要: Diffuse water pollution from agriculture (DWPA) is a major environmental concern, with significant adverse impacts on both human and ecosystem health. However, without an appropriate understanding of the multiple factors impacting on water, mitigation measures cannot be targeted. Therefore, this paper addresses this gap in understanding, reporting the hydrochemical monitoring evidence collected from the UK Government's Demonstration Test Catchments (DTC) programme including contrasting chalk and clay/mudstone catchments. We use data collected at daily and sub-daily frequency over multiple sites to address: (1) How does the behaviour of the full range of nitrogen (N) species and phosphorus (P) fractions vary (2) How do N species and P fractions vary inter- and intra-annually (3) What do these data indicate about the primary pollution sources And (4) which diffuse pollution mitigation measures are appropriate in our study landscapes Key differences in the rates of flux of nutrients were identified, dependent on catchment characteristics. Full N speciation and P fractionation, together with dissolved organic carbon (DOC) enabled identification of the most likely contributing sources in each catchment. Nitrate (NO₃-N) was the dominant N fraction in the chalk whereas organic and particulate N comprised the majority of the load in the clay/mudstone catchments. Despite current legislation, orthophosphate (PO₄-P) was not found to be the dominant form of P in any of the catchments monitored. The chalk sub-catchments had the largest proportion of inorganic/dissolved organic P (DOP), accompanied by episodic delivery of particulate P (PP). Contrastingly, the clay/mudstone sub-catchments loads were dominated by PP and DOP. Thus, our results show that by monitoring both the inorganic and organic fractions a more complete picture of catchment nutrient fluxes can be determined, and sources of pollution pin-pointed. Ultimately, policy and management to bring nutrient impacts under control will only be successful if a multi-stressor approach is adopted.
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30666. 题目: The contribution of atmospheric particulate matter to the formation of CX₃R-type disinfection by-products in rainwater during chlorination
文章编号: N18082503
期刊: Water Research
作者: Mengtian Hou, Wenhai Chu, Feifei Wang, Yang Deng, Naiyun Gao, Di Zhang
更新时间: 2018-08-25
摘要: Atmospheric particulate matter (PM) can be scavenged by rainfall and contribute dissolved organic matter (DOM) to rainwater. Rainwater may serve as a part or the whole of drinking water sources, leading to the introduction of PM-derived DOM into drinking water. However, little information is available on the role of PM-derived DOM as a remarkable precursor of CX₃R-type disinfection by-products (DBPs) in rainwater. In this study, samples were collected from ten occurrences of rainfall in Shanghai and batch experiments were executed to explore the contribution of PM-derived DOM to CX₃R-type DBP formation in rainwater and to further understand some of unknowns regarding its characteristics. Results revealed that a part of PM was scavenged by rainfall and the scavenge performance was better for smaller PM. The formation potential (FP) of individual CX₃R-type DBP was similar among size-isolated PM. TCM was predominant (around 0.5–4.5 μg-C/mg-C) and TCAA was the secondary (around 0.6–3.2 μg-C/mg-C) among all detectable CX₃R-type DBPs. Based on the PM removal data and DBP FP results, the contribution of PM-derived DOM to CX₃R-type DBP formation in rainwater was modeled. Furthermore, aromatic proteins and soluble microbial product-like compounds were found to be significant compositions, which were reported to be DBP precursors. And low molecular weight (<10 kDa) DOM derived from total PM and rainwater exhibited higher CX₃R-type DBP FPs. DOM fractions with higher SUVA₂₅₄ and SUVA₂₈₅ values gave relatively higher yields of CX₃R-type DBPs, indicating that aromatic compounds played an important role in DBP formation.
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30667. 题目: Comparison of black carbon chemical oxidation and macroscopic charcoal counts for quantification of fire by-products in sediments
文章编号: N18082502
期刊: Organic Geochemistry
作者: Richard S. Vachula, Ewerton Santos, Marcelo R. Alexandre, Yongsong Huang
更新时间: 2018-08-25
摘要: Black carbon (BC) ranges in size from submicron to millimeter scales and represents incompletely combusted or pyrolysed organic fuels (e.g., coal, petroleum, biomass etc). The content of BC in sediments or in the atmosphere has been widely used to infer fossil fuel combustion from local to regional sources. However, the assessment of natural fires (biomass burning) in the past has been conventionally performed by counting charcoal particles in different size fractions (greater than ca. 10 and 100 microns for microscopic and macroscopic charcoal, respectively) using a microscope. Because similarly sized charcoal particles can have large differences in mass, counting using microscopes may induce significant error for quantifying fire-produced BC in sediments. A popular method oxidizes BC with nitric acid to produce benzene polycarboxyclic acids (BPCAs), which can be subsequently quantified using a gas chromatograph and mass spectrometer (GC-FID and GC–MS). In this paper, we provide the first parallel comparison of charcoal and BPCA analyses to assess their ability to quantitatively record BC content in experimental sediments. We find that while qualitatively comparable, the BPCA method more accurately quantifies changes in BC content than does charcoal microscopy. Additionally, we use metadata analyses of the Global Charcoal Database to contextualize our results. Further, we explore possible applications of these two methods in tandem which could provide novel insight into paleofire characteristics.

30668. 题目: Sulfurization as a preservation mechanism for the δ¹³C of biomarkers
文章编号: N18082501
期刊: Organic Geochemistry
作者: Yoav O. Rosenberg, Ilya Kutuzov, Alon Amrani
更新时间: 2018-08-25
摘要: We compiled data from studies that examined pairs of compound specific δ¹³C in both the free- and S-bound fractions. The studies compiled span a wide range of biomarker type, rock age (∼235Ma to 3Kyr) and paleo-environments in which the sedimentary organic matter was deposited. Despite this variability, majority of data shows that the S-bound fraction is heavier on average by 2‰ compared with the free HC. The hypotheses of different biological sources and fractionation during sulfurization or maturation of the organic matter are reexamined in light of this result. We conclude that the δ¹³C fractionation between these two fractions should be a result of a more generalizing mechanism, operating at an early diagenetic stage. Fractionation during biodegradation of the free biomarker fraction can offer such a mechanism. Thus, the S-bound fraction may better represent the original δ¹³C values of biomarkers used in paleoenvironmental studies. Future studies should confirm this suggested mechanism.

30669. 题目: Bioavailability of Pyrene Associated with Different Types of Protein Compounds: Direct Evidence for Its Uptake by Daphnia magna
文章编号: N18082420
期刊: Environmental Science & Technology
作者: Hui Lin, Xinghui Xia, Xiaoman Jiang, Siqi Bi, Haotian Wang, Yawei Zhai, Wu Wen, Xuejun Guo
更新时间: 2018-08-24
摘要: The protein-like dissolved organic matter (DOM) is ubiquitous in aquatic environments. However, the bioavailability of protein-like DOM-associated hydrophobic organic compounds (HOCs) is not well-understood, and in particular, the direct evidence of their uptake by organisms is scarce. In the present work, tryptone (2000 Da), bovine serum albumin (BSA; 66 000 Da), and phycocyanin (120 000 Da) were chosen as model protein-like DOM, which were labeled by commercial fluorescein (cy5) to investigate the uptake mechanisms of protein compound-associated pyrene (a typical HOC) by Daphnia magna. The pyrene concentration in the tissues except the gut and immobilization of D. magna were detected to calculate the bioavailable fraction of protein compound-associated pyrene when the freely dissolved pyrene concentration was controlled through passive dosing devices. The results demonstrated that the tryptone could permeate cellular membrane and directly enter the tissues of D. magna from the exposure solutions, whereas BSA and phycocyanin might indirectly enter the tissues from the gut. A part of pyrene associated with protein compounds was bioavailable to D. magna; the order of their bioavailable fractions was trypone (54.6–58.1%) > phycocyanin (21.6–32.8%) > BSA (17.7–26.8%). The difference was principally related to the uptake mechanisms of pyrene associated with different types of protein. This work suggests that the protein compound-associated HOCs should be considered to evaluate the bioavailability and eco-environmental hazard of HOCs in natural waters.
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30670. 题目: Experimental evidence reveals impact of drought periods on dissolved organic matter quality and ecosystem metabolism in subalpine streams
文章编号: N18082419
期刊: Limnology and Oceanography
作者: Astrid Harjung, Elisabet Ejarque, Tom Battin, Andrea Butturini, Francesc Sabater, Masumi Stadler, Jakob Schelker
更新时间: 2018-08-24
摘要: Subalpine streams are predicted to experience lower summer discharge following climate change and water extractions. In this study, we aimed to understand how drought periods impact dissolved organic matter (DOM) processing and ecosystem metabolism of subalpine streams. We mimicked a gradient of drought conditions in stream‐side flumes and evaluated implications of drought on DOM composition, gross primary production, and ecosystem respiration. Our experiment demonstrated a production and release of DOM from biofilms and leaf litter decomposition at low discharges, increasing dissolved organic carbon concentrations in stream water by up to 50%. Absorbance and fluorescence properties suggested that the released DOM was labile for microbial degradation. Dissolved organic carbon mass balances revealed a high contribution of internal processes to the carbon budget during low flow conditions. The flumes with low discharge were transient sinks of atmospheric CO₂ during the first 2 weeks of drought. After this autotrophic phase, the metabolic balance of these flumes turned heterotrophic, suggesting a nutrient limitation for primary production, while respiration remained high. Overall our experimental findings suggest that droughts in subalpine streams will enhance internal carbon cycling by transiently increasing primary production and more permanently respiration as the drought persists. We propose that the duration of a drought period combined with inorganic nutrient availability are key variables that determine if more carbon is respired in situ or exported downstream.

30671. 题目: Arsenic immobilization through regulated ferrolysis in paddy field amendment with bismuth impregnated biochar
文章编号: N18082418
期刊: Science of The Total Environment
作者: Ningyuan Zhu, Jun Qiao, Tingmei Yan
更新时间: 2018-08-24
摘要: Iron minerals are important for arsenic immobilization in paddy fields; however, intensive ferrolysis causes arsenic (As) release. Bismuth-impregnated biochar derived from wheat straw (BiBC) was synthesized to immobilize arsenic by regulating the ferrolysis process in a paddy field. Further X-ray based analysis (XRD and XPS) results demonstrated that crystal particles of bismuth oxide and bismuth oxychloride were loaded on the biochar surface, helped create additional micropores and improved its specific surface area. The bioavailability of As, as determined via (non)specifically adsorbed As, decreased as the amended dosage of BiBC increased, while wheat straw biochar (WBC) resulted in arsenic release. The presence of biochar caused a faster reduction rate of iron oxides; however, BiBC promoted the sequential co-precipitation of iron and arsenic ions. Adsorption kinetic experiments indicated that ferrous ions facilitated precipitation of As on the surface of BiBC. The XRD analysis of soil samples showed BiBC facilitated the formation/stability of FeOOH. Thus, amendment with BiBC regulated ferrolysis to buffer iron leaching, which contributed to arsenic immobilization under flooding conditions. This study demonstrated the feasibility of As immobilization by metal-impregnated biochar in paddy soils.
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30672. 题目: Comparative study of electrochemical hybrid systems for the treatment of real wastewaters from agri-food activities
文章编号: N18082417
期刊: Science of The Total Environment
作者: Mouna Ghazouani, Hanene Akrout, Salah Jellali, Latifa Bousselmi
更新时间: 2018-08-24
摘要: Agri-food wastewaters are characterized by high contents of hardly biodegradable organics and large amounts of inorganics especially nitrogen and phosphorus. The present work investigates the efficiency of two electrochemical treatment processes, namely electrochemical oxidation/reduction (EOR), electrocoagulation (EC) and their combination for the treatment of two types of effluents collected from poultry slaughterhouse (SHWW) and dairy (DWW) industries. The optimization of these treatment systems in terms of pollutant performance removal and energy cost were carried out. The EOR treatment was assessed on a bipolar cell with Boron-Doped Diamond (BDD) supported on silicon electrodes. While, the EC treatment was performed on a reactor containing mild steel electrodes with parallel configuration. The simultaneous removal efficiencies of the organic matter in term of the chemical oxygen demand (COD), nitrates, ammonium/ammonia and phosphates, as well as the electric energy consumption (EEC), were evaluated for the different electrochemical scenarios. Results indicated that the EOR treatment shows the highest removal efficiencies of COD, nitrates and ammonia from the two studied wastewaters. While, the phosphates were removed only by the EC process. On the other hand, the EC process shows a relatively low cost in term of EEC (0.01 kWh/g COD⁻¹), which is about 13 times lower than the one consumed during the EOR process. The combination of the two processes leads to the improvement of the removal rate of all coexistent pollutants when the EC technology was used as a pre-treatment step. While, this coupling mode has the highest EEC. However, when the EOR process was used before the EC one, the removal rates of COD and nitrates were globally similar to the EOR process alone with a relatively low EEC.
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30673. 题目: Dissolved organic matter processing and photoreactivity in a wastewater treatment constructed wetland
文章编号: N18082416
期刊: Science of The Total Environment
作者: Arpit Sardana, Barbara Cottrell, David Soulsby, Tarek N. Aziz
更新时间: 2018-08-24
摘要: Constructed wetlands have the capacity to degrade a host of contaminants of emerging concern through photodegradation via sunlight produced reactive oxygen species. Dissolved organic matter (DOM) is a critical intermediary in photodegradation as it influences the production of reactive oxygen species. In this study, the photochemical behavior of DOM of wastewater treated in constructed wetlands was characterized. Whole water samples and fractionated DOM were characterized using SUVA₂₅₄, spectral slope ratios, excitation emission matrix fluorescence spectroscopy (EEMs), and proton nuclear magnetic resonance (¹H NMR). Photoreactivity was assessed by measuring formation rates and steady state concentrations of hydroxyl radical (^•OH), singlet oxygen (¹O₂), and the triplet excited states of DOM (³DOM^⁎). The effluent was observed to transition from a microbially sourced protein-like DOM to a terrestrial DOM with higher aromaticity. Size exclusion chromatography revealed an 18% increase in larger molecular weight fractions of vegetated wetland effluent DOM. Additionally, wetland effluent DOM was observed to have a 32% increase in the aromatic region of ¹H NMR spectra as compared to untreated wastewater. ¹H NMR analysis also indicated an increase in the complexity of wetland effluent DOM. Fluorescence intensity fraction of the protein-like Peak T (Ex/Em:278/342 nm) of EEMs decreased by 16% from the untreated wastewater to wetland effluent. A negative correlation between the percent fluorescence of Peak T (Ex/Em:278/342 nm) and Peaks A (Ex/Em:245/460 nm), C (Ex/Em:336/435 nm), and M (Ex/Em:312/400 nm) of the excitation emission spectra confirmed the transition from a spectrum of pure wastewater to a spectrum characteristic of terrestrially derived DOM. Microbial uptake of bio-labile DOM and leaching of humic like substances from vegetated wetland cells were the predominant processes involved in this transition. This transition coincided with an increase in the formation rates of ¹O₂ and ³DOM^⁎ and in the steady state concentration of ¹O₂.
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30674. 题目: Biodegradation of oxytetracycline and enrofloxacin by autochthonous microbial communities from estuarine sediments
文章编号: N18082415
期刊: Science of The Total Environment
作者: Malek Harrabi, Diogo A.M. Alexandrino, Fatma Aloulou, Boubaker Elleuch, Bei Liu, Zhongjun Jia, C. Marisa R. Almeida, Ana P. Mucha, Maria F. Carvalho
更新时间: 2018-08-24
摘要: This work investigated the potential of microbial communities native to an estuarine environment to biodegrade enrofloxacin (ENR) and oxytetracycline (OXY). Sediments collected from two sites in the Douro river estuary (Porto, Portugal) were used as inocula for the biodegradation experiments. Experiments were carried out for one month, during which ENR and OXY (1 mg L⁻¹) were supplemented individually or in mixture to the cultures at 10-day intervals. Acetate (400 mg L⁻¹) was added to the cultures every 3 days to support microbial growth. A series of experimental controls were established in parallel to determine the influence of abiotic breakdown and adsorption in the removal of the antibiotics. Removal of antibiotics was followed by measuring their concentration in the culture medium. Additionally, next-generation sequencing of the 16S rRNA gene amplicon was employed to understand how microbial communities responded to the presence of the antibiotics. At the end of the biodegradation experiments, microbial cultures derived from the two estuarine sediments were able to remove up to 98% of ENR and over 95% of OXY. The mixture of antibiotics did not affect their removal. ENR was removed mainly by biodegradation, while abiotic mechanisms were found to have a higher influence in the removal of OXY. Both antibiotics adsorbed at different extents to the estuarine sediments used as inocula but exhibited a higher affinity to the sediment with finer texture and higher organic matter content. The presence of ENR and OXY in the culture media influenced the dynamics of the microbial communities, resulting in a lower microbial diversity and richness and in the predominance of bacterial species belonging to the phylum Proteobacteria. Therefore, microbial communities native from estuarine environments have potential to respond to the contamination caused by antibiotics and may be considered for the recovering of impacted environments through bioremediation.
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30675. 题目: Influence of parasitic chytrids on the quantity and quality of algal dissolved organic matter (AOM)
文章编号: N18082414
期刊: Water Research
作者: Yukiko Senga, Shiori Yabe, Takaki Nakamura, Maiko Kagami
更新时间: 2018-08-24
摘要: Algae-derived dissolved organic matter (AOM) is an important nutrient source for heterotrophic bacteria, while AOM such as humic substances pose significant challenges during water treatment processing. We hypothesized that the parasitic infection of algae could change the composition and concentration of AOM. This study investigated the quality and quantity of DOM and bacterial abundance in diatom (Synedra) cultures, with and without parasitic fungi (chytrids). The quality of DOM was analyzed using three-dimensional excitation-emission matrices combined with parallel factor analysis (EEM-PARAFAC) and was compared to changes in algal and bacterial cell numbers. Bacterial abundance was higher and dissolved organic carbon concentrations were lower in the diatom cultures infected with parasitic fungi. Among the DOM compounds, the concentrations of tryptophan-like material derived from algae were significantly lower and the concentrations of humic substance-like material were higher in the infected treatment. The parasitic fungi may have consumed tryptophan-like material and stimulated the release of humic substances. These results provide the first evidence that fungal infection may modulate algal–bacterial interactions, which are associated with changes in the nature of AOM.

30676. 题目: Impact of soil properties on soil methane flux response to biochar addition: a meta-analysis
文章编号: N18082413
期刊: Environmental Science: Processes Impacts
作者: Weiwei Cong, Jun Meng, Samantha C Ying
更新时间: 2018-08-24
摘要: In an effort to optimize soil management practices that can help mitigate terrestrial carbon emissions, biochar has been applied to a wide range of soil environments to examine their effect on soil greenhouse gas emissions. Such studies have shown that soil methane (CH4) flux response can vary widely leading to both increase and decrease in CH4 flux upon biochar amendment. To address this discrepancy, multiple meta-analysis studies have been performed in recent years to determine the key factors that may control the direction of CH4 flux upon biochar treatment. However, even comparing across conclusions from meta-analyses reveals disagreement upon which factors ultimately determine the change in direction and magnitude of CH4 flux due to biochar additions. Furthermore, using multiple observations from a single study can lead to misinterpretation of the influence of a factor within a meta-analysis due to non-independence. In this study, we use a multivariate meta-regression approach that allows factor interactions to investigate which biochar, soil, and management practice factors in combination or individually best explain CH4 flux response in past biochar amendment studies. Our results show that the interaction of multiple soil factors (i.e., water saturation, soil texture, soil organic carbon content) best explains soil CH4 flux response to biochar additions (minimum deviance information criterion, DIC, value along with lowest heterogeneity) as compared to all models utilizing individual factors alone. These findings provide insight into the specific soil factors that should be taken into account simultaneously when optimizing CH4 flux response to biochar amendments and building empirical models to quantitatively predict soil CH4 flux.

30677. 题目: Diffusion limitations and Michaelis–Menten kinetics as drivers of combined temperature and moisture effects on carbon fluxes of mineral soils
文章编号: N18082412
期刊: Biogeosciences
作者: Fernando Esteban Moyano, Nadezda Vasilyeva, and Lorenzo Menichetti
更新时间: 2018-08-24
摘要: CO₂ production in soils responds strongly to changes in temperature and moisture, but the magnitude of such responses at different timescales remains difficult to predict. Knowledge of the mechanisms leading to the often observed interactions in the effects of these drivers on soil CO₂ emissions is especially limited. Here we test the ability of different soil carbon models to simulate responses measured in soils incubated at a range of moisture levels and cycled through 5, 20, and 35°C. We applied parameter optimization methods while modifying two structural components of models: (1) the reaction kinetics of decomposition and uptake and (2) the functions relating fluxes to soil moisture. We found that the observed interactive patterns were best simulated by a model using Michaelis–Menten decomposition kinetics combined with diffusion of dissolved carbon (C) and enzymes. In contrast, conventional empirical functions that scale decomposition rates directly were unable to properly simulate the main observed interactions. Our best model was able to explain 87% of the variation in the data. Model simulations revealed a central role of Michaelis–Menten kinetics as a driver of temperature sensitivity variations as well as a decoupling of decomposition and respiration C fluxes in the short and mid-term, with general sensitivities to temperature and moisture being more pronounced for respiration. Sensitivity to different model parameters was highest for those affecting diffusion limitations, followed by activation energies, the Michaelis–Menten constant, and carbon use efficiency. Testing against independent data strongly validated the model (R² = 0.99) and highlighted the importance of initial soil C pool conditions. Our results demonstrate the importance of model structure and the central role of diffusion and reaction kinetics for simulating and understanding complex dynamics in soil C.
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30678. 题目: Soil chemistry and microbial community functional responses to invasive shrub removal in mixed hardwood forests
文章编号: N18082411
期刊: Applied Soil Ecology
作者: Graham S. Frank, Cindy H. Nakatsu, Michael A. Jenkins
更新时间: 2018-08-24
摘要: Invasive woody plant species are a threat to biodiversity and ecosystem function in forests of the eastern U.S., due in part to their effects on soil properties and nutrient cycling. Controlling invasive shrubs can benefit the ecosystem at multiple scales, but these species tend to resprout when cut, and post-cutting flushes of root exudates have been linked to accelerated decomposition of soil organic matter (SOM), a rhizosphere priming effect. We removed the invasive shrub Lonicera maackii (Rupr.) Herder (Amur honeysuckle) from forested sites in central Indiana, USA, using cut-stump and forestry mulching head treatments. For two growing seasons after the initial removal treatments, we compared the soil chemistry and microbial community function of bulk and honeysuckle rhizosphere soils in shrub removal areas to those in invaded reference areas. Microbial activity measured using multiple substrate induced respiration (MSIR) in bulk soils was generally lower in removal areas than reference areas the first year, coinciding with relatively elevated responses in the rhizosphere soils of resprouting shrubs. Elevated SOM and organic C in rhizosphere soils of resprouting shrubs suggested a flush of rhizodeposits from cutting and regrowth. However, bulk soil chemistry responses to shrub removal did not show any evidence of a rhizosphere priming effect, but instead reflected the reduced effects of honeysuckle on throughfall precipitation chemistry—higher ammonium and lower magnesium. Nonetheless, changes in bulk soil chemistry between years were driven by the chemical characteristics of rhizosphere soil associated with resprouting honeysuckle. This study is the first to document the potential for invasive shrub control to affect soil properties through rhizodeposition by the target species.

30679. 题目: What can we learn from ancient fertile anthropic soil (Amazonian Dark Earths, shell mounds, Plaggen soil) for soil carbon sequestration?
文章编号: N18082410
期刊: CATENA
作者: Jürgen Kern, Luise Giani, Wenceslau Teixeira, Giacomo Lanza, Bruno Glaser
更新时间: 2018-08-24
摘要: Historical land use and soil management left behind anthropic soils such as Amazonian Dark Earths (Terras Pretas de Índio - pretic Anthrosols), Anthropic shell mounds (Sambaquis - terric Anthrosols), and Plaggen soils (plaggic Anthrosols), enriched in soil organic matter and soil fertility. The objective of this study was to compare soil organic matter quantity and quality of these tropical and temperate anthropic soils among each other and against their adjacent non-anthropic soils. All anthropic soil horizons had enhanced total contents of C, N, P, K, Ca, Mg and Fe, reflecting a soil organic matter and nutrient enrichment compared to their reference soils, mostly expressed by the Sambaquis. In order to better understand the mechanisms of soil organic matter stability, besides black carbon analysis, topsoils and subsoils were incubated in the laboratory at 10 °C and 30 °C and the emitted CO₂ was recorded for 44-days. The Plaggen soil released the highest amount of CO₂ at 30 °C, being two to three times higher compared to Terra Preta de Índio and Sambaqui anthropic horizons. The highest mean residence times (MRT), between 38 and 63 years, were calculated for the subsoils of the anthropic soils incubated at 10 °C. In the artificial system of this study, the stability of anthropic soil horizons under study was not generally enhanced when compared with their reference soils. However, enhanced stability of total organic carbon (TOC) was indicated by a negative relationship between black carbon portion of TOC and the relative amount of CO₂-C released from TOC of all anthropic soils. During the incubation period of 44 days, the cumulatively mineralized amount of soil organic carbon (SOC) in the top of anthropic soils at 30 °C was three to six times as high as that at 10 °C. Consequently high temperature under tropical conditions should have stimulated the decay of organic matter, which however was not reflected by high TOC contents found in Terra Preta and Sambaqui samples, corroborating their low degradability in the long term. Therefore, we propagate that a high stability of carbon stocks exists in anthropic soil horizons, which may become a promising opportunity for the establishment of a new generation of anthropic soils with improved soil fertility and soil organic matter using the principle of soil-biochar systems.

30680. 题目: Ozone/peroxide advanced oxidation in combination with biofiltration for taste and odour control and organics removal
文章编号: N18082409
期刊: Chemosphere
作者: Divyam Beniwal, Liz Taylor-Edmonds, John Armour, Robert C. Andrews
更新时间: 2018-08-24
摘要: The objective of this pilot-scale study was to investigate the effectiveness of incorporating ozone (O₃) and advanced oxidation (hydrogen peroxide/ozone: H₂O₂/O₃) in combination with biofiltration for taste and odour control, organic carbon removal, and disinfection byproduct (DBP) precursor reduction. Implementation of O₃ and H₂O₂/O₃ with and without biofiltration was investigated at pilot-scale in terms of geosmin, 2-methylisoborneol (MIB), and DBP precursor removal efficiency. Two media types (granular activated carbon and anthracite) were compared in conjunction with investigating the impact of pre-oxidation with O₃ (2 mg/L) and varying H₂O₂/O₃ mass ratios (0.1, 0.2, 0.35, and 0.5 mg/mg). When O₃ preceded biologically active carbon (BAC) or biologically active anthracite, geosmin removals of 80% and 81%, respectively, were observed at 10 °C; this increased to 89% and 90%, respectively, at 16 °C. Optimal MIB removal (67%) was achieved with 0.1 H₂O₂/O₃ (mg/mg) in combination with BAC at 16 °C.In general, geosmin proved to be more amenable to biodegradation than MIB. BAC without pre-oxidation removed 87% geosmin and 85% MIB, at 22 °C. MIB removals decreased to 60% and 46%, respectively at 16 °C and 10 °C. The application of 0.2 H₂O₂/O₃ (mg/mg) prior to BAC provided treatment which effectively removed geosmin and MIB. However, in terms of DBP precursor reduction, there was no beneficial impact of H₂O₂ addition on trihalomethane or haloacetic acid formation potentials.