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12421. 题目: Increased soil respiration in response to experimentally reduced snow cover and increased soil freezing in a temperate deciduous forest
文章编号: N18091115
期刊: Biogeochemistry
作者: Andrew B. Reinmann, Pamela H. Templer
更新时间: 2018-09-11
摘要: Winter snowpack in seasonally snow-covered regions plays an important role in moderating ecosystem processes by insulating soil from freezing air temperatures. However, climate models project a decline in snowpack at mid and high latitudes over the next century. We conducted a snow removal experiment in a temperate deciduous forest at Harvard Forest in Massachusetts, USA to quantify the effects of a reduced winter snowpack and increased soil freezing on total soil respiration and its bulk (i.e. heterotrophic) and root-rhizosphere components. Snow removal increased soil freezing severity by more than three-fold, which resulted in a 27.6% increase in annual total soil respiration (p = 0.058). Across our plots and years of this study, we found that the severity, rather than simply the presence of soil freezing, was the primary driver of the soil respiration response to reduced winter snowpack. Bulk soil respiration made the largest contribution to total soil respiration with root-rhizosphere respiration contributing up to 26.1 ± 6.5% of total soil respiration across plot types and years. Snow removal significantly increased fine root mortality (p = 0.03), which was positively correlated with soil frost depth and duration (p = 0.068, R2LMM(m) = 0.46), rates of total soil respiration (p = 0.075; R2LMM(m) = 0.27) and the contribution of root-rhizosphere respiration to total soil respiration (p = 0.004; R2LMM(m) = 0.58). We conclude that increased rates of soil respiration in response to soil freezing are driven by plant-mediated processes, whereby soil frost-induced root mortality stimulates respiration through decomposition of root necromass with additional enhancements possibly related to priming of soil organic matter decomposition and elevated rates of root respiration associated with growth.

12422. 题目: Detection and assessment of the phytotoxicity of residual organic pollutants in sediment contaminated with pulp and paper mill effluent
文章编号: N18091114
期刊: Environmental Monitoring and Assessment
作者: Sangeeta Yadav, Ram Chandra
更新时间: 2018-09-11
摘要: The safe disposal of pulp and paper mill effluent is still a threat to the environment due to the presence of several unknown organic pollutants. The comparative physico-chemical analysis of pulp and paper mill effluent-contaminated sediment (PPECS) of site 1 and site 2 showed that the sediment had an alkaline nature and was loaded with several organic pollutants and heavy metals. SEM-EDX examination showed a porous structure with a heterogeneous distribution of particles, allowing the adsorption of metal and other complex organic ions. FTIR analysis depicted the presence of a variety of functional groups, i.e., alkyl halides, phenolics, and lignin, in the contaminated sediment. GC-MS analysis showed the major presence of organic pollutants, i.e., 2-methyl-4-keto-2-pentan-2-ol and 3,7-dioxa-2,8-disilanonane,2,2,8,8-tetramethyl-5-[(trimethylsilyl)oxy], in the site 1 sediment contaminated with pulp and paper mill waste, while 2-methyl-4-keto-2-trimethylsiloxypentane, 4-ethyl-2-methoxyphenol, ethyl-2-octynoate, cis-9-hexadecenoic acid, and octadecenoic acid were detected in the site 2 sediment contaminated with pulp and paper mill waste. The genotoxicity of PPECS determined by examining Allium cepa root cell division showed chromosomal aberration. In this study, several compounds that have not been reported before were identified.

12423. 题目: Significant reduction in air pollutant emissions from household cooking stoves by replacing raw solid fuels with their carbonized products
文章编号: N18091113
期刊: Science of The Total Environment
作者: Qing Li, Juan Qi, Jingkun Jiang, Jianjun Wu, Lei Duan, Shuxiao Wang, Jiming Hao
更新时间: 2018-09-11
摘要: Residential solid fuel combustion contributes significantly to ambient and indoor air pollutions. An appropriate clean solid fuel to reduce residential emissions is urgently needed. This study evaluates the reduction in pollutant emissions achieved by carbonized solid fuels in residential cooking practice. Four biochar samples, three semi-coke briquette samples and their raw materials were tested in a typical cooking stove. These carbonized samples showed higher thermal efficiencies and lower particulate matter (PM) emission factors (EFs) than their raw material samples. Owing to distilled volatile matter during carbonization treatment, average energy delivered-based PM2.5 EFs were 10 ± 5 mg/kJ (carbonized) and 50 ± 28 mg/kJ (raw) for the biomass and 0.33 ± 0.04 mg/kJ (carbonized) and 3.0 ± 1.3 mg/kJ (raw) for the coal samples. The energy delivered-based EFs of organic carbon, elemental carbon, and 16 priority polycyclic aromatic hydrocarbons extracted from PM2.5 samples from carbonized fuels were reduced by 97 ± 1%, 93 ± 3%, and 97 ± 2%, respectively, for the tested biomass samples, and those for the tested coal samples were 96 ± 1%, 90 ± 6%, and 98 ± 2%, respectively. Average EFs of benzo[a]pyrene equivalent carcinogenic potency for individual polycyclic aromatic hydrocarbons were reduced 95 ± 3% to ~0.51 μg/kJ (carbonized) from ~19.6 μg/kJ (raw). Furthermore, the average ratio of volatile organic compounds contained in PM2.5 samples was also reduced from 38.8 ± 5.4% to 7.1 ± 3.9%. These results suggest that carbonized solid fuels exhibit better performance in reducing carcinogenic potency and pollutants, most of which are highly correlated with the volatile matter content of the fuel. Switching from raw solid fuel to carbonized solid fuel will help to reduce pollutant emissions from household combustion and achieve both environmental benefits and health benefits for household residents.
图文摘要:

12424. 题目: Thermochemical conversion of cobalt-loaded spent coffee grounds for production of energy resource and environmental catalyst
文章编号: N18091112
期刊: Bioresource Technology
作者: Dong-Wan Cho, Daniel C.W. Tsang, Sohyun Kim, Eilhann E. Kwon, Gihoon Kwon, Hocheol Song
更新时间: 2018-09-11
摘要: Thermochemical conversion of cobalt (Co)-loaded lignin-rich spent coffee grounds (COSCG) was carried out to find the appropriate pyrolytic conditions (atmospheric gas and pyrolytic time) for syngas production (H2 and CO) and fabricate Co-biochar catalyst (CBC) in one step. The use of CO2 as atmospheric gas and 110-min pyrolytic time was optimal for generation of H2 (∼1.6 mole% in non-isothermal pyrolysis for 50 min) and CO (∼4.7 mole% in isothermal pyrolysis for 60 min) during thermochemical process of COSCG. The physicochemical properties of CBC fabricated using optimized pyrolytic conditions for syngas production were scrutinized using various analytical instruments (FE-SEM, TEM, XRD, and XPS). The characterizations exhibited that the catalyst consisted of metallic Co and surface wrinkled carbon layers. As a case study, the catalytic capability of CBC was tested by reducing p-nitrophenol (PNP), and the reaction kinetics of PNP in the presence of CBC was measured from 0.04 to 0.12 s-1.
图文摘要:

12425. 题目: Stability of aerobic granular sludge under condition of low influent C/N ratio: correlation of sludge property and functional microorganism
文章编号: N18091111
期刊: Bioresource Technology
作者: Zhiming Zhang, Zhuodong Yu, Jingjing Dong, Zihao Wang, Ke Ma, Xiangyang Xu, Pedro J.J. Alvarezc, Liang Zhu
更新时间: 2018-09-11
摘要: Aerobic granular sludge process treating domestic wastewater with low C/N ratio is necessary to be studied for rapid urbanization in China and other countries. In this study, two parallel reactors with different influent C/N ratio (15 in R1, 5 in R2) were established. Compared to the disintegrated granule in R1 with high influent C/N ratio, granules with large size (650μm) and compact structure (integrity coefficient<0.1) were stable in R2 along with influent C/N ratio decreased to 5. High-through sequencing illustrated the functional microbes like Thauera and Paracoccus enriched under low influent C/N ratio, and principal component analysis further showed these microbes were positive correlation with tryptophan and protein-like substances in extracellular polymeric substances (EPS) and granular strength. It was indicated that under low influent C/N ratio, several resistant microbes like Thauera (19.5%) enriched and then secreted tryptophan and protein-like substances, and stable granules with multi-functional microbes could be formed finally.
图文摘要:

12426. 题目: Aqueous removal of inorganic and organic contaminants by graphene-based nanoadsorbents: A review
文章编号: N18091110
期刊: Chemosphere
作者: Sewoon Kim, Chang Min Park, Min Jang, Ahjeong Son, Nauguk Her, Miao Yu, Shane Snyder, Do-Hyung Kim, Yeomin Yoon
更新时间: 2018-09-11
摘要: Various graphene-based nanoadsorbents, including graphenes, graphene oxides, reduced graphene oxides, and their nanocomposites, have been widely studied as potential adsorbents due to their unique physicochemical properties, such as structural variability, chemical strength, low density, and the possibility of large scale fabrication. Adsorption mechanisms are governed largely by the physicochemical properties of contaminants, the characteristics of nanoadsorbents, and background water quality conditions. This review summarizes recent comprehensive studies on the removal of various inorganic (mainly heavy metals) and organic contaminants by graphene-based nanoadsorbents, and also discusses valuable information for applications of these nanoadsorbents in water and wastewater treatment. In particular, the aqueous removal of various contaminants was reviewed to (i) summarize the general adsorption capacities of various graphene-based nanoadsorbents for the removal of different inorganic and organic contaminants, (ii) evaluate the effects of key water quality parameters such as pH, temperature, background major ions/ionic strength, and natural organic matter on adsorption, (iii) provide a comprehensive discussion of the mechanisms that influence adsorption on these nanoadsorbents, and (iv) discuss the potential regeneration and reusability of nanoadsorbents. In addition, current challenges and future research needs for the removal of contaminants by graphene-based nanoadsorbents in water treatment processes are discussed briefly.
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12427. 题目: Application of biochar to soils may result in plant contamination and human cancer risk due to exposure of polycyclic aromatic hydrocarbons
文章编号: N18091109
期刊: Environment International
作者: Jian Wang, Kang Xia, Michael Gatheru Waigi, Yanzheng Gao, Emmanuel Stephen Odinga, Wanting Ling, Juan Liu
更新时间: 2018-09-11
摘要: Biochars are added to soil to improve agronomic yield. This greenhouse- and field-scale study evaluated polycyclic aromatic hydrocarbon (PAH) contamination in 35 commercial and laboratory-produced biochars, and assessed the effects of biochar amendment of soils on PAH accumulation in vegetables and the risk for cancer. The total and bioavailable PAH concentrations in biochars varied from 638 to 12,347 μg/kg and from below the detection limit (BDL) to 2792 μg/kg, respectively. PAH formation in biochars decreased with increasing production temperature (350–650 °C). Root exudates enhanced PAH release from biochars. The total PAH concentrations in eight edible vegetables growing in biochar-amended soil varied according to biochar and vegetables type from BDL to 565 μg/kg. A health risk assessment framework was integrated with the benzo[a]pyrene toxic equivalency quotient and the incremental lifetime cancer risk (ILCR) to estimate the exposure risk for human beings via ingestion of PAH-contaminated vegetables. The total ILCR for adults was above 10−6, which suggests a risk to human health from direct exposure to PAHs in vegetables grown in biochar-amended soil. These results demonstrate that biochar application may lead to contamination of plants with PAHs, which represents a risk to human health. The PAH levels in biochars produced using different conditions and/or feedstocks need to be evaluated and biochars should be pretreated to remove PAHs before their large-scale agronomic application.
图文摘要:

12428. 题目: Distribution and cycling of terrigenous dissolved organic carbon in peatland-draining rivers and coastal waters of Sarawak, Borneo
文章编号: N18091108
期刊: Biogeosciences
作者: Patrick Martin, Nagur Cherukuru, Ashleen S. Y. Tan, Nivedita Sanwlani, Aazani Mujahid, and Moritz Müller
更新时间: 2018-09-11
摘要: South-East Asia is home to one of the world's largest stores of tropical peatland, and accounts for roughly 10% of the global land-to-sea dissolved organic carbon (DOC) flux. We present the first-ever seasonally-resolved measurements of DOC concentration and chromophoric dissolved organic matter (CDOM) spectra for six peatland-draining rivers and coastal waters in Sarawak, north-western Borneo. The rivers differed substantially in DOC concentration, ranging from 120–250µmolL−1 (Rajang river) to 3,100–4,400µmolL−1 (Maludam river). All rivers carried high CDOM concentrations, with a350 in the four blackwater rivers between 70–210m−1, and 4–12m−1 in the other two rivers. DOC and CDOM showed conservative mixing with seawater except in the largest river (the Rajang), where DOC concentrations in the estuary were elevated, most likely due to inputs from the extensive peatlands within the Rajang delta. Seasonal variation was moderate and inconsistent between rivers. However, during the rainier north-east monsoon, all marine stations in the western part of our study area had higher DOC concentrations and lower CDOM spectral slopes, indicating a greater proportion of terrigenous DOM in coastal waters. Photo-degradation experiments revealed that riverine DOC and CDOM in Sarawak are photo-labile: up to 25% of riverine DOC was lost within five days of exposure to natural sunlight, and the spectral slopes of photo-bleached CDOM resembled those of our marine samples. We conclude that coastal waters of Sarawak receive large inputs of terrigenous DOC that is only minimally altered during estuarine transport, and that any biogeochemical processing must therefore occur mostly at sea. It is likely that photo-degradation plays an important role in the degradation of terrigenous DOC in these waters.

12429. 题目: The chemical evolution of brine and Mg-K-salts along the course of extreme evaporation of seawater – An experimental study
文章编号: N18091107
期刊: Geochimica et Cosmochimica Acta
作者: Netta Shalev, Boaz Lazar, Michael Köbberich, Ludwik Halicz, Ittai Gavrieli
更新时间: 2018-09-11
摘要: Extreme evaporation experiments of modern seawater, up to a degree of evaporation (DE) of 870 on Li scale and brine density of 1.40 g∙ml-1 were conducted under controlled semi-natural conditions. This DE is well within the bischofite facies and, to the best of our knowledge, is the highest experimental DE ever reported. During the experiments, brine temperature varied between ∼20°C and ∼40°C with few excursions to higher temperatures, thereby demonstrating the effect of temperature on the precipitating mineral assemblages. Results were compared to a thermodynamic simulation of the evaporation experiment at 25°C, based on the Harvie-Møller-Weare activity coefficients correction.The relative amounts of the precipitated minerals were evaluated from the bulk chemical composition of the collected precipitates, applying a Li based methodology for subtracting the contribution of the brine adsorbed on the precipitated salts. The following minerals were identified during the evaporation experiments: halite (NaCl), epsomite (MgSO4∙7H2O), kainite (KMgClSO4∙3H2O), carnallite (MgKCl3∙6H2O), kieserite (MgSO4∙H2O) and bischofite (MgCl2∙6H2O). The precipitation of the Mg-salts was accompanied by continuous halite precipitation up to DE of ∼170. The experimental results are in good agreement with literature experimental data, available up to DE = 98, and generally follow the thermodynamic calculations, thereby supporting both the established methodology of the experiments and the simulation parameters and assumptions. Minor differences between the experiments and the thermodynamic calculation are mainly due to temperature variations. The experiments suggest that, at warmer temperatures (∼50°C), kainite and bischofite precipitate instead of kieserite, which precipitates to a greater extent at lower temperatures (25-30°C). The presence of organic matter (OM) in the brine was found to reduce the evaporation rate and the final DE at which evaporation ceased, but not to significantly affect the chemical evolution of the brine.The detailed systematic data-set presented here is useful for both geochemical and applied purposes. For example, it can be used as a reference for reconstructing the evolution of ancient marine derived brines, using evaporitic sequences far beyond the halite facies. Hence, this study provides new insights on the formation of such evaporitic minerals and opens the way for further studies on these highly soluble evaporitic sequences as clues to the chemical composition of the ancient oceans.

12430. 题目: Response of soil alkaline phosphatase to biochar amendments: Changes in kinetic and thermodynamic characteristics
文章编号: N18091106
期刊: Geoderma
作者: A. Khadem, F. Raiesi
更新时间: 2018-09-11
摘要: Biochar addition to soil often increases the activity of alkaline phosphatase (ALP) involved in phosphorus (P) cycling, but the underlying mechanisms of its effect is poorly understood. This study investigated the response of kinetic parameters including maximal velocity (Vmax) and Michaelis–Menten constant (Km), and thermodynamic parameters including activation energy (Ea), enthalpy (ΔHa) and temperature coefficient (Q10) of ALP to addition of two maize biochars (400 and 600 °C) in two calcareous (Typic Haplocalcid) soils with clayey and sandy loam texture. The biochars were added to the soils at 1% (w/w) and the mixtures were incubated for 90 days under laboratory conditions (25 ± 1 °C and 70% of water holding capacity). Soils with addition of raw residue were used as positive controls and soils without biochar and raw residue were included as negative controls. The potential activity of ALP was assayed at the end of incubation period. The kinetic parameters of ALP were estimated using non-linear regression techniques and the thermodynamic characteristics were determined at different incubation temperatures (17, 27, 37, 47 and 57 °C) using the Arrhenius equation. Compared with the negative control, the addition of raw residue and biochars increased ALP activity (3.1- to 4.4-fold) after the 90-day incubation, depending upon the pyrolysis temperature and soil texture. The positive effect of biochar addition on soil ALP was greater with low than high temperature biochars and in sandy loam than clayey soils. Biochar addition increased the Km and Vmax values of ALP in the clayey soil but decreased these parameters in the sandy loam soil compared with the corresponding negative controls. Generally, application of maize raw residue and biochars increased the Ea, ΔHa and Q10 values of ALP compared with the negative controls, and the increases were similar for the two pyrolysis temperatures. Soil ALP can be strongly adsorbed by biochar particles; increasing its thermal stability and decreasing its sensitivity to elevated temperatures. In conclusion, application of maize biochar to arid-soils has a high potential to improve the ALP activity, with implications for organic P mineralization and availability. Biochar would change ALP kinetic and thermodynamic characteristics differently, depending mainly on soil texture, through the surface adsorption of this enzyme on biochar particles. These changes will be useful for modeling P mineralization and biochemical processes in biochar-amended calcareous soils.

12431. 题目: Prediction of soil organic carbon stock by laboratory spectral data and airborne hyperspectral images
文章编号: N18091105
期刊: Geoderma
作者: Long Guo, Haitao Zhang, Tiezhu Shi, Yiyun Chen, Qinghu Jiang, M. Linderman
更新时间: 2018-09-11
摘要: Soil organic carbon (SOC) plays an important role in controlling the function and quality of soil and offsetting the emissions of greenhouse gases. However, the dynamic monitoring and estimation of SOC are very difficult due to the complex traditional methods and the changing environmental variables. For instance, the calculation of SOC stock requires measurement of a few relevant soil attributes, such as soil organic matter (SOM), soil bulk density (SBD), soil moisture, and soil weight, in the laboratory. Many studies have suggested that visible and near-infrared (vis–NIR) spectra are a practical and affordable alternative to accurately and rapidly estimate the soil attributes relevant to SOC stock, and airborne hyperspectral images can be used as a valuable data source to perform digital soil mapping with high spatial resolution. The objective of this research was to check the predicted capability of SOC stock through laboratory and airborne vis–NIR spectral data. A total of 50 topsoil samples (0–15 cm) from the farmland of Iowa City were used as the study object. The partial least squares regression model was used to predict SOC stock through the direct and indirect methods. In the direct method, the SOC stock was predicted using the spectral data. In the indirect method, the relevant soil properties (SOM and SBD) of the SOC stock were predicted using the spectral data, and then the SOC stock was calculated. The mechanism of the prediction methods and the potential influencing factors of the model performance were discussed from the aspect of electromagnetic theory and empirical statistics. Results showed the following: (i) SOC stock can be successfully predicted using the laboratory spectra and the airborne hyperspectral image through the direct and indirect methods; (ii) the SOC stock and its relevant soil properties (SOM and SBD) showed evident spectral absorption characteristics in the vis–NIR spectral band; (iii) the atmospheric environment and soil surface conditions were the main influencing factors of the prediction accuracy between the airborne and laboratory spectra. This research might be useful for the dynamic monitoring and modeling of SOC in agricultural and environmental fields.

12432. 题目: Terrestrial humic-like fluorescence peak of chromophoric dissolved organic matter as a new potential indicator tracing the antibiotics in typical polluted watershed
文章编号: N18091104
期刊: Journal of Environmental Management
作者: Sijia Li, Hanyu Ju, Meichen Ji, Jiquan Zhang, Kaishan Song, Peng Chen, Guangyi Mu
更新时间: 2018-09-11
摘要: Natural surface waters are threatened globally by antibiotics pollution. In this study, we analyzed antibiotics and CDOM (Chromophoric dissolved organic matter) fluorescence in different water bodies using HPLC method and Excitation Emission Matrix- Parallel factor analysis, respectively. A combination of field studies in the Yinma River Watershed were conducted in rivers, reservoirs and urban rivers, and 65 CDOM and antibiotic samples were taken in April, May, July, and August 2016. EEM-PARAFAC analysis identified two components; a humic-like (C1) component and a tryptophan-like (C2) component. The redundancy analysis (RDA) demonstrated that CDOM could explain 38.2% (two axes) of the five antibiotics in reservoirs (N = 31), and 26.0% (two axes) of those in rivers and urban water (N = 30). Furthermore, the Pearson correlation coefficient between Sulfamethoxazole and C1 in reservoir water was 0.91 (t-test, 2-tailed, p < 0.01), and that between Sulfamethoxazole and C2 was 0.68 (t-test, 2-tailed, p < 0.01). This indicated that the humic-like component of CDOM PARAFAC fluorescence could detect Sulfamethoxazole contamination levels in the homogenized reservoir waters. Our results identified Sulfamethoxazole and Quinolones (Norfloxacin, 16.5 ng L−1; Enrofloxacin, 0.3 ng L−1; Ciprofloxacin, 30.9 ng L−1) at mean concentrations of 369.5 ng L−1 and 15.9 ng L−1, respectively, which were the higher levels in natural surface waters. The FTIR spectroscopy of the mixture of humic acid and sulfamethoxazole showed that the absorbance at 3415 cm−1 linked to OH stretching of OH groups and at 1386 cm−1 because of OH bending and vibration of COOH groups became weaker, indicating that COOH groups of humic acid can adsorb and react with –NH2 of sulfamethoxazole. The CDOM PARAFAC components can be adapted for online or in situ fluorescence measurements as an early warning of Sulfamethoxazole distribution and contamination in similar aquatic environments.
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12433. 题目: Comparison of mesozooplankton mortality impacted by the cooling systems of two nuclear power plants at the northern Taiwan coast, southern East China Sea
文章编号: N18091103
期刊: Marine Pollution Bulletin
作者: Pei-Wen Lee, Li-Chun Tseng, Jiang-Shiou Hwang
更新时间: 2018-09-11
摘要: The environmental impact caused by thermal discharge waters of power plants is of global concern since thermal discharge directly affects the environmental situation near power plants. The present study used the vital stain neutral red to identify live and dead zooplankton collected from stations at the intake and the outlet of two nuclear power plants (NPPs). Significantly higher mortalities occurred at the outlet station than at the intake station (p < 0.01) at both NPPs. The mortalities of most zooplankton taxa and all zooplankton assemblages were significantly positive correlated to differences of water temperature (ΔT) at NPP I (p < 0.05), whereas it was not significantly positive correlated with ΔT at NPP II (p > 0.05). The weight of organic matter of zooplankton fragments was higher at the outlet station than at the intake station at both NPPs, indicating the physical damage of zooplankton when passing the cooling system.

12434. 题目: Assessing the impact of long-term changes in climate and atmospheric deposition on a shallow alpine lake from southeast Tibet
文章编号: N18091102
期刊: Science of The Total Environment
作者: Wengang Kang, Guangjie Chen, Jiaoyuan Wang, Linpei Huang, Lei Wang, Rui Li, Kui Hu, Yuanyuan Liu, Jianshuang Tao, Jules M. Blais, John P. Smol
更新时间: 2018-09-11
摘要: Regional warming and atmospheric nitrogen deposition have been widely recorded to impact remote catchments and alpine lakes; however, their independent roles and interactions have rarely been identified. Here, we combined down-core analyses of sedimentary mercury (Hg) and aluminum (Al) with multiple proxies (i.e. nitrogen stable isotope, chlorophyll a pigments, diatoms) for a radiometrically-dated sediment core of an alpine lake in southeast Tibet to track the atmospheric deposition of pollutants, and to examine possible effects of climate and catchment forcing over the past three centuries. The sediment data revealed that airborne deposition of Hg was recorded from the ~1860s, with an accelerating increase in anthropogenic Hg flux since the ~1960s. A synchronous decrease in reconstructed lake-water TOC indicated that acid deposition may have affected lake-water carbon concentrations and impaired catchment export of decomposed organic matter (OM). A moderate depletion of bulk sediment δ15N started from the ~1820s, but was followed by an enriching trend after the ~1970s. This positive shift of δ15N was associated with elevated sediment OM and decreased catchment runoff of clastic materials (as inferred by Al). Sediment OM content displayed an accelerating increase from the ~1960s, with an increased input of autochthonous sources (i.e. lower bulk sediment C:N ratios), such as algae (as inferred by sedimentary chlorophyll a pigments). Meanwhile, climate warming and decreased lake-water TOC enhanced the production of algae, which was characterized by a more enriched δ15N signal than that of allochthonous OM. Furthermore, atmospheric acid deposition was significantly related to diatom assemblage changes, with an increase in acidophilous taxa. Our sediment evidence revealed the dominating impact of climate and catchment processes on lake-water chemistry and algal shifts in the context of atmospheric nitrogen deposition, and highlighted an increasing link of external forcing with in-lake processes in enriching sediment δ15N signal over the last few decades.
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12435. 题目: Warming increased feeding of a root-chewing insect at the soil surface and enhanced its damage on a grass
文章编号: N18091101
期刊: Soil Biology and Biochemistry
作者: Tomonori Tsunoda, Kobayashi Makoto, Jun-Ichirou Suzuki, Nobuhiro Kaneko
更新时间: 2018-09-11
摘要: Air and soil warming influences both plants and root herbivorous insects, but how warming alters their interactions is largely unknown. Because both the intensity of herbivory and plant susceptibility to the herbivory depend on temperature, it is difficult to predict the effects of insect herbivory on plant growth under warming. To analyse changes in belowground plant-insect interaction due to warming, we conducted a pot experiment using one grass species, Lolium perrene, and one beetle grub Anomala cuprea. Temperature (17 °C or 20.3 °C), presence or absence of a grub, and presence or absence of organic matter (OM) on the surface of the potted soil were manipulated. OM at the soil surface is an important resource for grubs, and contains neutral lipid fatty acids (NLFA) that can serve as a bacterial marker. NLFAs can be used as a tracer to determine whether grubs had fed upon OM, so we evaluated the consumption and vertical movement of a grub in response to warming. In the absence of grubs, plant biomass increased with warming, but was not affected by the OM treatment. In the presence of grubs, plant biomass was significantly decreased. Moreover, the interaction term between the temperature and grub treatments was significant, demonstrating that grub damage was more severe under warmer conditions. Grub mortality was not affected by any treatment. The bacterial NLFAs in a grub were significantly more detectable when OM was added relative to those without OM, and the amount increased with warming treatments. This suggests that the grub fed near the soil surface under both temperature conditions, but increased consumption rates under the warmer condition. The mean relative soil moisture content in the warmer conditions was significantly lower than that in the control conditions. OM additionally increased soil moisture, but it had no effect on herbivory damage, suggesting that plant susceptibility to herbivory was not attributable to soil moisture. These results show the importance of biological-context dependency of warming on a plant. Temperature changes will alter the root-herbivore interactions not by changing the plant susceptibility to herbivory but by increasing the consumption of the grub.

12436. 题目: Desert leaf litter decay: coupling of microbial respiration, water-soluble fractions and photodegradation
文章编号: N18091008
期刊: Global Change Biology
作者: Thomas A. Day, Michael S. Bliss, Alexander R. Tomes, Christopher T. Ruhland, René Guénon
更新时间: 2018-09-10
摘要: The mechanisms of plant litter decay in drylands are poorly understood, limiting the accuracy of nutrient‐cycling models for these systems. We monitored the decay of 12 leaf litter types on the soil surface of the Sonoran Desert for 34 months and assessed what traits predicted mass loss and how exposure to different wavebands of sunlight influenced mass loss. Mass loss varied considerably among litter types, ranging from 42‐96% after 34 months in full sunlight. Traditional indices of litter quality (e.g. initial C:N or lignin:N ratios) failed to predict differences in mass loss among litter types. The strongest predictor of mass loss was the microbial respiration rate of initial litter, which explained 45‐54% of the variation in loss among litter types. Microbial respiration rates were not correlated with traditional indices of litter quality, but were positively correlated with the water‐soluble fraction in litter and concentrations of dissolved organic C in this fraction. Traditional indices of litter quality failed to predict decay likely because they did a poor job of predicting microbial degradability of litter, not because microbial degradation was a minor driver of decay. In all radiation‐exposure treatments, water‐soluble fractions and respiration rates increased through decay and were several times higher after 34 months than initially. Hence, labile pools and microbial degradability of litter increased through decay in contrast to traditional views that labile pools decline and constrain microbes. Litter exposed to UV or UV through blue radiation wavelengths, lost on average 1.3 times or 1.5 times more mass, respectively, than litter not exposed to these wavebands. The magnitude of this photodegradation was greater in litter types that had higher initial concentrations of hemicellulose and cellulose per unit surface area. Litter exposed to full sun had higher water‐soluble fractions and usually had higher respiration rates, illustrating that sunlight accelerated microbial degradation by increasing labile pools. The processes driving litter decay appeared to differ appreciably from mesic systems and involved strong couplings between abiotic and biotic drivers.

12437. 题目: Molecular and isotopic evaluation of the maturation history of the organic matter in an Ordovician aquiclude (Michigan Basin): Evidence for late diagenetic biodegradation
文章编号: N18091007
期刊: Organic Geochemistry
作者: Josué J. Jautzy, Jason M.E. Ahad, Mark Jensen, Ian D. Clark
更新时间: 2018-09-10
摘要: Previous characterization of a low permeability (10–16 ≤ Kh ≤ 10–12 m.s–1) and high salinity (> 5 M of Cl, > 10× seawater salinity) aquiclude, in Upper Ordovician-aged sediments situated on the eastern flank of the Michigan Basin, where a deep geological repository for low and intermediate level nuclear waste is proposed, suggested a microbial origin for CH4 and CO2 based on their stable isotope values. CH4 is believed to have been produced and trapped during the Paleozoic in a relatively discrete and high organic matter (OM) horizon at the shale/carbonate transition. To further investigate the efficiency of confinement of this aquiclude, here we present detailed isotopic and geochemical stratigraphic profiles of OM and biomarkers, with the objective of understanding the origin of CH4 and its relative timing of confinement. Classical diagnostic ratios of polycyclic aromatic hydrocarbons, relative abundances of hopanes and degraded hopanes coupled to dual compound-specific isotopic analysis of n-alkanes, as well as δ13C analysis on different fractions of OM were measured. A partitioning of the Ordovician sedimentary succession into two systems is observed with an upper system that is self-sourced and confined, hosting the microbially derived CH4 with evidence of late diagenetic OM biodegradation and a lower system that reveals later secondary oil migration which has overprinted the organic geochemical record. We propose a conceptual model that would explain the generation and preservation of this paleo-bioreactor over time using the maturation history reconstruction derived from this dataset. This work not only provides essential field empirical evidence of a relationship between methanogenesis and late diagenetic biodegradation, but also shows the power of dual-compound-specific isotope analyses in deciphering between different maturation processes affecting OM in natural subsurface settings.

12438. 题目: Potential of guava leaves for mitigating methane emissions and modulating ruminal fermentation characteristics and nutrient degradability
文章编号: N18091006
期刊: Environmental Science and Pollution Research
作者: Adham A. Al-Sagheer, Eman A. Elwakeel, Mariam G. Ahmed, Sobhy M. A. Sallam
更新时间: 2018-09-10
摘要: Guava leaves (Psidium guajava, GL), a high-phenolic- and flavonoid-containing plant resource capable of substituting the high-quality forage, may help in mitigating ruminal methane (CH4) emission without adverse impact on nutrient degradability if supplemented at an appropriate level. In order to test this hypothesis, rumen fermentation, CH4 production, and nutrient degradability of GL either solely or as a substitute of berseem hay (Trifolium alexandrinum, BH) were evaluated in a diet containing 50:50 concentrate to roughage. Five different levels of GL (0, 12.5, 25, 37.5, and 50%) were tested in vitro after 24 h incubation using a semi-automated gas production (GP) system. The current findings indicated that merely the presence of GL resulted in significantly lower values for cumulative GP (P < 0.001), CH4 emission (P < 0.05), truly degraded dry matter (TDDM; P < 0.001), truly degraded organic matter (TDOM; P < 0.001), and ammonia nitrogen (NH3-N) concentration (P < 0.001); however, pH (P < 0.001) and partitioning factor (P < 0.001) were higher. The total and individual volatile fatty acid (VFA) concentrations were drastically declined with GL as compared to BH (P < 0.05). A negative linear correlation was recorded between the levels of GL and GP including CH4 production (P < 0.05). The addition of GL up to 25% did not pose any negative effect on both TDDM and TDOM values along with NH3-N concentration. In addition, the inclusion of GL up to 25% did not affect the total or individual VFA concentration. Conclusively, in a medium concentrate diet, use of 25% GL and 25% BH in animal diet could be a promising alternative for mitigating the CH4 production without any deleterious effect on nutrient degradability.

12439. 题目: Forest harvest legacies control dissolved organic carbon export in small watersheds, western Oregon
文章编号: N18091005
期刊: Biogeochemistry
作者: Kate Lajtha, Julia Jones
更新时间: 2018-09-10
摘要: This study examined physical and biological controls on dissolved organic carbon (DOC) fluxes from conifer-forest watersheds in the H.J. Andrews Experimental Forest of Oregon. We tested how DOC export was related to streamflow and legacies of wood on the forest floor three to five decades after harvest of old-growth forest in seven watersheds spanning the rain to snow elevation gradient. Three watersheds had old-growth forest and four had 30 to 50-year-old forest established after clearcutting of old-growth forest. Mean annual DOC flux in the watersheds was related to the biomass of forest floor wood, which was two or three times higher in watersheds with old-growth forest compared to young forest, and was inversely related to elevation, a measure of snowpack depth and duration. In contrast, fluxes of inorganic elements such as Si and Ca did not vary with harvest history or forest floor characteristics. Annual fluxes of DOC, Si, and Ca were linearly related to annual runoff, and annual volume-weighted concentrations of these ions declined by < 0.6% with several-fold increases in annual runoff. Across all years, DOC concentrations peaked before the peak of the hydrograph in all watersheds, which we interpret as representing movement, likely via preferential and surficial flow, of organic materials mineralized and solubilized during the long dry summers in this ecosystem. DOC concentrations relative to stream flow exhibited clockwise hysteresis loops in each water year, also suggesting that soluble DOC produced in the dry summer is exported in the fall. DOC concentration differences between reference and harvested watersheds also peaked in late summer or early fall, suggesting that the source of the additional DOC from reference watersheds came from coarse woody debris that remains moist during the dry summers and that was significantly greater in watersheds with elevated DOC. Taken together, our results suggest that forest floor wood is a previously unappreciated control on the supply of DOC that can be exported, and runoff is a secondary control on total DOC flux to streams. The legacy of forest harvest on DOC flux can be observed for decades, as total ecosystem carbon stocks, especially coarse woody debris, may require centuries to develop after old-growth forest harvest.

12440. 题目: Biological activity of carbonic nano-structures—comparison via enzymatic bioassay
文章编号: N18091004
期刊: Journal of Soils and Sediments
作者: Anna S. Sachkova, Ekaterina S. Kovel, Grigoriy N. Churilov, Devard I. Stom, Nadezhda S. Kudryasheva
更新时间: 2018-09-10
摘要: Purpose: The aim of the work is to compare the biological activity of carbonic nano-structures of natural and artificial origination, namely, humic substances (HS) and fullerenols. Materials and methods: The representative of the fullerenol group, С60Оy(OH)x where у + x = 20–22, was chosen. Enzyme-based luminescent bioassay was applied to evaluate toxicity and antioxidant properties of HS and fullerenol (F); chemiluminescent luminol method was used to study a content of reactive oxygen species (ROS) in the solutions. Toxicity of the bioactive compounds was evaluated using effective concentrations ЕС50; detoxification coefficients DOxT were applied to study and compare antioxidant activity of the compounds. Antioxidant activity and ranges of active concentrations of the bioactive compounds were determined in model solutions of organic and inorganic oxidizers—1,4-benzoquinone and potassium ferricianide. Results and discussion: Values of ЕС50 revealed higher toxicity of HS than F (0.005 and 0.108 g L−1, respectively); detoxifying concentrations of F were found to be lower. Antioxidant ability of HS was demonstrated to be time-dependent; the 50-min preliminary incubation in oxidizer solutions was suggested as optimal for the detoxification procedure. On the contrary, F’ antioxidant effect demonstrated independency on time. Antioxidant effect of HS did not depend on amphiphilic characteristics of the media (values of DOxT were 1.3 in the solutions of organic and inorganic oxidizers), while this of F was found to depend: it was maximal (DOxT = 2.0) in solutions of organic oxidizer, 1,4-benzoquinone. Conclusions: Both HS and F demonstrated toxicity and low-concentration antioxidant ability; however, quantitative characteristics of their effects were different. The differences were explained with HS polyfunctionality, higher ability to decrease ROS content, non-rigidity, and diffusion restrictions in their solutions. Antioxidant effect of the bioactive compounds was presumably attributed to catalytic redox activity of their π-fragments. The paper demonstrates a high potential of luminescent enzymatic bioassay to study biological activity of nano-structures of natural and artificial origination.

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