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27721. 题目: Carbon, iron and sulphur cycling in the sediments of a Mediterranean lagoon (Ghar El Melh, Tunisia)
文章编号: N19032117
期刊: Estuarine, Coastal and Shelf Science
作者: Walid Oueslati, Sebastiaan van de Velde, M. Amine Helali, Ayed Added, Lotfi Aleya, Filip J.R. Meysman
更新时间: 2019-03-21
摘要: Coastal lagoon sediments are important for the biogeochemical carbon cycle at the land-ocean transition, as they form hotspots for organic carbon burial, as well as potential sites for authigenic carbonate formation. Here, we employ an early diagenetic model to quantify the coupled redox cycling of carbon, iron and sulphur in the sediments of the shallow Ghar El Melh (GEM) lagoon (Tunisia). The model simulated depth profiles show a good correspondence with available pore water data (dissolved inorganic carbon, NH₄⁺, total alkalinity, Ca²⁺, Fe²⁺ and SO₄²⁻) and solid phase data (organic matter, pyrite, calcium carbonate and iron (oxyhydr)oxides). This indicates that the model is able to capture the dominant processes influencing the sedimentary biogeochemical cycling. Our results show that sediment of the GEM lagoon is an efficient reactor for organic matter breakdown (burial efficiency < 10%), with an important role for aerobic respiration (32%) and sulphate reduction (61%). Despite high rates of sulphate reduction, free sulphide does not accumulate in the pore water, due to a large terrestrial input of reactive iron oxides and the efficient sequestration of free sulphide into iron sulphide phases. High pyrite burial (2.2 mmol FeS₂ m⁻² d⁻¹) prevents the reoxidation of reduced sulphide, thus resulting in a low total oxygen uptake (4.7 mmol m⁻² d⁻¹) of the sediment and a relatively high oxygen penetration depth. The formation of pyrite also generates high amounts of alkalinity in the pore water, which stimulates authigenic carbonate precipitation (2.7 mmol m⁻² d⁻¹) and leads to alkalinity release to the overlying water (3.4 mmol m⁻² d⁻¹). Model simulations with and without an N-cycle reveal a limited influence of nitrification and denitrification on the overall organic matter diagenesis. Overall, our study highlights the potential role of coastal lagoons for the global carbon and sulphur cycle, and their possible contribution to shelf alkalinity, which increases the buffering capacity of the coastal ocean for CO₂ uptake.

27722. 题目: The relative importance of different carbon structures in biochars to carbamazepine and bisphenol A sorption
文章编号: N19032116
期刊: Journal of Hazardous Materials
作者: Gang Chu, Jing Zhao, Yang Liu, Di Lang, Min Wu, Bo Pan, Christian E.W. Steinberg
更新时间: 2019-03-21
摘要: Biochar, a carbon-rich material, has attracted immense attention owing to its applications in soil remediation. However, the mechanisms by which heterogeneous carbon structures of biochars immobilize organic contaminants are not yet fully understood. In this study, the noncondensed aromatic components in biochars were selectively removed through bleaching. Different techniques, such as ¹³C nuclear magnetic resonance, were applied to characterize the biochar compositions, and thus the role of the different carbon structures in organic contaminant sorption was discussed. The aromatic carbon structures in biochars were gradually developed and evolved from noncondensed to condensed structure with increasing pyrolytic temperatures from 300 to 700 °C. Based on elemental analysis, the carbon removed by bleaching decreased from 43.9% to 5.92% with increasing temperatures. After the surface area normalization of the apparent sorption, bleaching increased the sorption of carbamazepine and bisphenol A on biochars produced at 500 °C, but not for those produced at 300 and 700 °C. Bleaching removed noncondensed aromatics and enriched condensed aromatics, which resulted in increased sorption. However, bleaching also resulted in the blockage of micropores in biochars with abundant condensed aromatics, causing decreased sorption. The apparent sorption was determined by the balancing of these two opposite effects.
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27723. 题目: Interactive effects of rice straw biochar and γ-Al₂O₃ on immobilization of Zn
文章编号: N19032115
期刊: Journal of Hazardous Materials
作者: Ping Wu, Peixin Cui, Marcelo E. Alves, Willie J.G.M. Peijnenburg, Cun Liu, Dongmei Zhou, Hailong Wang, Yong Sik Ok, Yujun Wang
更新时间: 2019-03-21
摘要: Biochar system technology has been proved as a sustainable remediation method for metal contaminated soils. However, little attention has been paid to the interaction between biochar and oxide minerals and their influence on metal immobilization in soils. In this study, batch-type Zn sorption experiments were conducted using the mixture of γ-Al₂O₃ and rice straw biochar as a model binary geosorbent systems. In addition, advanced spectroscopic technics such as EXAFS, FTIR and XRD were performed to reveal the mechanism. EXAFS spectroscopy revealed that 62% of Zn existed as Zn-Al layered double hydroxide (LDH) on γ-Al₂O₃ at pH 7.5 (for 2 mM Zn loading) within 24 h, which was 19% in the mixture. The Zn in biochar samples mainly existed as Zn-OM (53%-76%) and Zn₂SiO₄ (21%-47%), while the proportion of Zn₂SiO₄ (0-6%) was negligible compared with Zn-Al silicate (26-48%) in the mixtures. The overall findings confirmed that Al released from γ-Al₂O₃ was sorbed in parallel with Zn on biochar to form Zn-Al silicate, rather than Zn-Al LDH on the γ-Al₂O₃ surface. These results unveiled the dynamic interactions between amended biochar and soil oxide minerals which can significantly affect the immobilization pathways of metals in contaminated soils.
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27724. 题目: Biochar-Supported nZVI (nZVI/BC) for Contaminant Removal from Soil and Water: A Critical Review
文章编号: N19032114
期刊: Journal of Hazardous Materials
作者: Shengsen Wang, Mingyue Zhao, Min Zhou, Yuncong C. Li, Jun Wang, Bin Gao, Shinjiro Sato, Ke Feng, Weiqin Yin, Avanthi Deshani Igalavithana, Patryk Oleszczuk, Xiaozhi Wang, Yong Sik Ok
更新时间: 2019-03-21
摘要: The promising characteristics of nanoscale zero-valent iron (nZVI) have not been fully exploited owing to intrinsic limitations. Carbon-enriched biochar (BC) has been widely used to overcome the limitations of nZVI and improve its reaction with environmental pollutants. This work reviews the preparation of nZVI/BC nanocomposites; the effects of BC as a supporting matrix on the nZVI crystallite size, dispersion, and oxidation and electron transfer capacity; and its interaction mechanisms with contaminants. The literature review suggests that the properties and preparation conditions of BC (e.g., pore structure, functional groups, feedstock composition, and pyrogenic temperature) play important roles in the manipulation of nZVI properties. This review discusses the interactions of nZVI/BC composites with heavy metals, nitrates, and organic compounds in soil and water. Overall, BC contributes to the removal of contaminants because it can attenuate contaminants on the surface of nZVI/BC; it also enhances electron transfer from nZVI to target contaminants owing to its good electrical conductivity and improves the crystallite size and dispersion of nZVI. This review is intended to provide insights into methods of optimizing nZVI/BC synthesis and maximizing the efficiency of nZVI in environmental cleanup.

27725. 题目: Particulate organic matter distributions in surface waters of the Pacific Arctic shelf during the late summer and fall season
文章编号: N19032113
期刊: Marine Chemistry
作者: Miguel A. Goñi, Elizabeth R. Corvi, Kylie A. Welch, Maggie Buktenica, Kaitlin Lebon, Yvan Alleau, Laurie W. Juranek
更新时间: 2019-03-21
摘要: Climate change is leading to marked decreases in the extent, thickness and persistence of sea ice in Polar Regions, especially during the later summer and fall seasons. The expanded open water domain during this period has the potential to drastically affect the hydrography, biogeochemistry and ecology of Arctic seas. In view of these rapid changes, the distributions of particulate organic matter in surface waters from the Pacific Arctic shelf were determined during the late summer and early fall months (August–October) over four different years (2012, 2015, 2016, and 2017). Utilizing surface underway systems of research vessels in combination with a semi-automated filtration system, over a thousand individual samples from surface waters were collected along the northern Bering Sea and Chukchi Sea shelves. Particulate organic carbon (POC) concentrations and molar carbon:nitrogen ratios ([C:N])were determined to investigate the distribution and provenance of organic matter in surface waters at a high spatial resolution along the research vessels' navigational paths. Corrections for sorption of dissolved carbon and nitrogen were possible at high frequency because of our sampling techniques. The resulting blank-corrected POC concentrations in surface waters ranged from <2 to 35 μM, with several samples collected earlier (August) in the open water season displaying much higher concentrations (>60 μM). Large spatial and temporal variability characterized measurements throughout the study area, with maxima in POC concentration often measured in association with physical features (e.g., straits, capes, fronts, shoals) and strong wind events. Hydrographically, POC distributions displayed significant variability among water masses in the region. Alaska Coastal Water, which was predominant along the southern section of the study area (between Bering Strait and Pt. Hope), displayed the highest POC concentrations whereas Bering-Chukchi Shelf Water and especially Melt Water, which occupied the northern section of the study area (Pt. Hope to Utquiagvik) were characterized by the lowest POC concentrations. Earlier periods (August–September) also were characterized by higher average POC concentrations than later periods (September–October). Overall, most of the samples collected exhibited [C:N] ratios that ranged from 6 to 8 mol:mol, and were consistent with a predominant marine provenance. Our findings indicate POC distributions reflect patterns of wind forcing and physical circulation and identify regions of localized high standing stocks that suggest spatially and temporarily variable production in this area during the late open-water season.

27726. 题目: Nitrate sorption to biochar following chemical oxidation
文章编号: N19032112
期刊: Science of The Total Environment
作者: J.R. Sanford, R.A. Larson, T. Runge
更新时间: 2019-03-21
摘要: Biochar amendments can reduce nitrate (NO₃) leaching in agricultural soil. It has been hypothesized that functional groups on the biochar surface from oxidation can increase NO₃ sorption. This study evaluates the effect of chemical oxidation of biochar on NO₃ sorption characteristics. Eight biochars, made from wood and corn cobs, underwent sodium hypochlorite (NaClO) and hydrogen peroxide (H₂O₂) oxidation and then assessed for NO₃ sorption capacity using batch isotherm methods. The unoxidized and oxidized biochar produced at low temperatures (400 °C) had no significant NO₃ sorption. Oxidized biochars produced at higher temperatures (600 °C and 700 °C) had calculated maximum NO₃ sorption capacities (S_max) ranging from 0.50 to 3.97 mg NO₃-N g^-1. Biochar oxidations with 50 mmol NaClO g^-1 (N50) in combination with an acid wash (AW) had the largest estimated sorption capacities of 3.68, 3.97, and 1.46 mg NO₃-N g^-1 for CT_N50,AW, BW3_N50,AW, and CC3_N50,AW, respectively. Sorption capacity of wood-based biochars was higher than corn cob biochars due to increased oxidation as measured by total acid group content (TAGC). Wood biochar Smax values were correlated with ΔTAGC (R² = 0.86), with a slope of 1.2 μmol NO₃-N μmol TAGC^-1 suggesting that cationic bridging of NO₃ to oxidized sites is the primary mechanism for NO₃ sorption.
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27727. 题目: Microscopic comparison of aerosol particles collected at an urban site in North China and a coastal site in Japan
文章编号: N19032111
期刊: Science of The Total Environment
作者: Liang Xu, Daizhou Zhang, Weijun Li
更新时间: 2019-03-21
摘要: In order to understand the physicochemical properties of aerosol particles in Japan and China, transmission electron microscopy was used to analyze individual aerosol particles collected at two very different environmental sites, i.e., a continental site (T1) in North China and a coastal site (T2) in Japan in springtime. The average PM_2.5 concentration (52 μg/m³) at T1 was much higher than T2 (20 μg/m³) from 20 to 23 March 2014. Our study shows that sulfur-organic matter (S-OM) particles were the most abundant at both T1 and T2, and individual spherical primary organic matter (POM) particles were only observed at T1. More anthropogenic fly ash and metal particles were observed at T1, consistent with the heavier air pollution at T1 than T2, and the overall complexity of aerosol composition at T1 exceeded that at T2, due to the influence of regional industrial emissions. Further examination of S-OM particles suggest that S-OM coated particles accounted for 29.6% of total observed particles at T2 but only 8.6% at T1. However, the average thickness of OM coating was larger at T2 than at T1, indicating that the particles at T2 had aged longer than those at T1. These comparisons suggest that the OM coating thickness on sulfate depends on the transport distance of the air mass and on the concentration of atmospheric oxidants but should not be used to represent pollution levels. Compared with the coastal air in Japan, we know that urban aerosol particles in North China not only attain high concentrations but also have more complex aerosol components.
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27728. 题目: Enhancing the hydrolysis of saline waste sludge with thermophilic bacteria pretreatment: New insights through the evolution of extracellular polymeric substances and dissolved organic matters transformation
文章编号: N19032110
期刊: Science of The Total Environment
作者: Pengtao Gao, Liang Guo, Jian Sun, Yi Wang, Zonglian She, Mengchun Gao, Yangguo Zhao
更新时间: 2019-03-21
摘要: Recently, the treatment and utilization of saline waste sludge has drawn growing attention because large amounts of saline waste sludge were generated with the increase of saline wastewater discharge. In this study, thermophilic bacteria (TB) pretreatment was applied to accelerate the hydrolysis of saline waste sludge and the efficiency of hydrolysis at different salinities was evaluated. Compared with the group without salinity, the releasing of carbohydrate (up to a 67.0% decrease) in extracellular polymeric substances (EPS) was inhibited at the salinity ranging from 1.0% to 2.5%, and the releasing of protein (up to a 17.6% decrease) was inhibited under salinity conditions. Excess salinity (4.0%) caused the cell lysis, and the content of soluble chemical oxygen demand (SCOD), soluble carbohydrate and protein in dissolved organic matter (DOM) increased by 44.9%, 38.8% and 20.8% than that obtained without salinity, respectively. According to the excitation-emission matrix (EEM) fluorescence spectroscopy, the biodegradability of sludge was improved at 2.0% salinity. At 2.0% salinity, the maximum fluorescence intensity of soluble microbial byproduct substances (76,358.9 (au)) and the minimum fluorescence intensity of humic acid-like substances (173,424 (au)) were obtained. The increased salinity was beneficial for the sludge stabilization and was disadvantageous for the sludge reduction.
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27729. 题目: Soil organic carbon in semiarid alpine regions: the spatial distribution, stock estimation, and environmental controls
文章编号: N19032109
期刊: Journal of Soils and Sediments
作者: Meng Zhu, Qi Feng, Mengxu Zhang, Wei Liu, Ravinesh C. Deo, Chengqi Zhang, Linshan Yang
更新时间: 2019-03-21
摘要: Purpose: Soil organic carbon (SOC) in alpine regions is characterized by a strong local heterogeneity, which may contribute to relatively large uncertainties in regional SOC stock estimation. However, the patterns, stock, and environmental controls of SOC in semiarid alpine regions are still less understood. Therefore, the purpose of this study is to comprehensively quantify the stock and controls of SOC in semiarid alpine regions. Materials and methods: Soils from 138 study sites across a typical semiarid alpine basin (1755–5051 m, ~1 × 10⁴ km²) are sampled at 0–10, 10–20, 20–40, and 40–60 cm. SOC content, bulk density, soil texture, and soil pH are determined. Both a classical statistical model (i.e., a multiple linear regression, MLR) and a machine learning technique (i.e., a random forest, RF) are applied to estimate the SOC stock at a basin scale. The study further quantifies the environmental controls of SOC based on a general linear model (GLM) coupled with the structural equation modeling (SEM). Results and discussion: SOC density varies significantly with topographic factors, with the highest values occurring at an elevation zone of ~3400 m. The results show that the SOC is more accurately estimated by the RF compared to the MLR model, with a total stock of 219.33 Tg C and an average density of 21.25 kg C m⁻² at 0–60 cm across the study basin. The GLM approach reveals that the topography is seen to explain about 58.11% of the total variation in SOC density at 0–10 cm, of which the largest two proportions are attributable to the elevation (44.32%) and the aspect factor (11.25%). The SEM approach further indicates that, of the climatic, vegetative, and edaphic factors examined, the mean annual temperature, which is mainly shaped by topography, exerts the most significant control on SOC, mainly through its direct effect, and also, through indirect effect as delivered by vegetation type. Conclusions: The results of this study highlight the presence of high stocks of organic carbon in soils of semiarid alpine regions, indicating a fundamental role played by topography in affecting the overall SOC, which is mainly attained through its effects on the mean annual temperature.

27730. 题目: The role of biochar-microbe interaction in alleviating heavy metal toxicity in Hordeum vulgare L. grown in highly polluted soils
文章编号: N19032108
期刊: Applied Geochemistry
作者: Gorovtsov Andrey, Vishnu Rajput, Minkina Tatyana, Mandzhieva Saglara, Sushkova Svetlana, Kornienko Igor, Tatyana V. Grigoryeva, Chokheli Vasily, Aleshukina Iraida, Zinchenko Vladislav, Fedorenko Elena, Movsesyan Hasmik
更新时间: 2019-03-21
摘要: The influence of heavy metal-tolerant bacteria, biochar, and their joint application on Hordeum vulgare L., grown in highly polluted soils was analysed for the first time. The high concentrations of heavy metals (HMs) (Zn, Mn, Cr, Cu, Pb, Ni, Cd) were determined in the polluted soil (Spolic Technosol) obtained from the Lake Atamanskoe. The effects of these HMs led to marked differences in H. vulgare L. growth. HMs toxicity slows down the development of the plant by changing morphometric parameters. Application of biochar and microbes reduced the HMs accumulation and enhanced H. vulgare L. growth compared with plants grown in polluted soil without amendments. However, all treatments showed high accumulation of HMs in above- and underground tissues as compared with plants grown in unpolluted soil. The application of biochar and HM-tolerant bacteria decreased the HM content 1.78–9.23 fold and 1.79–5.30 fold, respectively, while the addition of both bacteria and biochar has led to a 3.11–17 fold decrease in HMs content and was the most effective to decrease the translocation of all the studied metals. The metal-tolerant bacteria influenced the plant growth to a large extent. The most prominent impact of biochar + bacteria application was observed for leaves length and dry weight of plants: the parameters were significantly higher and reached those of unpolluted control. However, all of the tested amendments improved the growth performance of plants in polluted soil. The alleviation of metal toxicity by the addition of biochar may be beneficial for the introduced bacteria and increase their activity.
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27731. 题目: Study of copper, lead, and zinc speciation in the Haplic Chernozem surrounding coal-fired power plant
文章编号: N19032107
期刊: Applied Geochemistry
作者: Marina Burachevskaya, Tatiana Minkina, Saglara Mandzhieva, Tatiana Bauer, Victor Chaplygin, Inna Zamulina, Svetlana Sushkova, Alexey Fedorenko, Karen Ghazaryan, Hasmik Movsesyan, Denis Makhinya
更新时间: 2019-03-21
摘要: The speciation of Cu, Pb, and Zn compounds in Haplic Chernozem under the anthropogenic impact of a power plant mainly operating on coal was studied. General tendencies in the distributions of Cu, Pb, and Zn among the compound forms were revealed using selective sequential extractions (Miller method modified by Berti and Jacobs (1996)), which is based on the nature of metals and the participation of soil components. In an uncontaminated soil occurring far from the emission source, 55–85% of total Cu, Zn, and Pb fractions are concentrated in the residual fraction characterizing the metal bond with silicates. In uncontaminated soils, the contents of Cu, Pb, and Zn in crystallized Fe compounds are largely higher than in its amorphous forms. Metals accumulate in the soil occurring near the power plant, which increases the total contents of Cu, Pb, and Zn in 1.3–2.5 times and their mobile (water-soluble, exchangeable, and carbonate-bound) compounds in 2–12 times. The largest contributions to the adsorption and retention of metals are made by silicates, as well as soil organic matter for Cu and Pb and nonsilicate Fe compounds for Zn. A significant increase in the exchangeable Zn fraction is observed in studied soils. The estimation of the degree of metal fixation in the soil was calculated Partition index of element, which reflects the degree of metal-soil bonding. It showed that the highest parameter value for the studied metals was found for the soils located at 15 km from the NPP, where the Index values approach 1; the lowest Index value is noted for contaminated soils nearby from the enterprise. Thus, sequential extraction is an effective tool to check the affinity of the soil components for Cu, Pb and Zn.
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27732. 题目: Influence of pyrolysis temperature on polycyclic aromatic hydrocarbons production and tetracycline adsorption behavior of biochar derived from spent coffee ground
文章编号: N19032106
期刊: Bioresource Technology
作者: Van-Truc Nguyen, Thanh-Binh Nguyen, Chiu-Wen Chen, Chang-Mao Hung, Thi-Dieu-Hien Vo, Jih-Hsing Chang, Cheng-Di Dong
更新时间: 2019-03-21
摘要: The main objective of this study was to evaluate the effect of different pyrolysis temperatures on the formation of polycyclic aromatic hydrocarbons (PAHs) in biochar originated spent coffee ground (SCG) and the tetracycline (TC) adsorption behavior of biochar in water. The results showed that biochar synthesized at 500 ^oC (SCG 500) contained low PAHs (600 µg kg^-1) and the highest TC adsorption efficiency. In addition, the characteristics, influencing factors on TC adsorption, and the related mechanisms of SCG 500 were comprehensively investigated. The results showed that the highest efficiency was observed at pH of 7 and the presence of ions in salinity solution reduced the adsorption capacity of SCG 500. The electrostatic interaction, hydrogen bonding, and π-EDA were the major adsorption mechanisms. Safety PAHs level, low-cost, widely material sources and high TC removal capacity suggested that SCG 500 was a promising environmentally friendly effective absorbent.
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27733. 题目: Surface functionalization determines behavior of nanoplastic solutions in model aquatic environments
文章编号: N19032105
期刊: Chemosphere
作者: Kevin Tallec, Océane Blard, Carmen González-Fernández, Guillaume Brotons, Mathieu Berchel, Philippe Soudant, Arnaud Huvet, Ika Paul-Pont
更新时间: 2019-03-21
摘要: Plastic debris are classified as a function of their size and recently a new class was proposed, the nanoplastics. Nano-sized plastics have a much greater surface area to volume ratio than larger particles, which increases their reactivity in aquatic environment, making them potentially more toxic. Only little information is available about their behavior whereas it crucially influences their toxicity. Here, we used dynamic light scattering (DLS) to explore the influence of environmental factors (fresh- and saltwater, dissolved organic matter) on the behavior (surface charge and aggregation state) of three different nano-polystyrene beads (50 nm), with (i) no surface functionalization (plain), (ii) a carboxylic or (iii) an amine functionalization. Overall, the positive amine particles were very mildly affected by changes in environmental factors with no effect of the salinity gradient (from 0 to 653 mM) and of a range 1–30 μg.L⁻¹ and 1–10 μg.L⁻¹ of organic matter in artificial seawater and ultrapure water, respectively. These observations are supposedly linked to a coating specificity leading to repulsive mechanisms. In contrast, the stability of the negatively charged carboxylic and plain nanobeads was lost under an increasing ionic strength, resulting in homo-aggregation (up to 10 μm). The increase in organic matter content had negligible effect on these two nanobeads. Analysis performed over several days demonstrated that nanoplastics formed evolving dynamic structures detected mainly with an increase of the homo-aggregation level. Thus, surface properties of given polymers/particles are expected to influence their fate in complex and dynamic aquatic environments.

27734. 题目: Inhalation bioaccessibility of Cd, Cu, Pb and Zn and speciation of Pb in particulate matter fractions from areas with different pollution characteristics in Henan Province, China
文章编号: N19032104
期刊: Ecotoxicology and Environmental Safety
作者: Weiqin Xing, Qiang Zhao, Kirk G. Scheckel, Lirong Zheng, Liping Li
更新时间: 2019-03-21
摘要: Windowsill particulate matter (PM) samples were collected from an area near large lead-smelting facilities in Jiyuan (JP), the urban area of Jiyuan (JU) and the peri-urban area of Mianchi (MC) in Henan, China to investigate the concentration and inhalation bioaccessibility of Cd, Cu, Pb and Zn. The <10 μm portions of the samples were extracted with simulated lung fluid to assess the in vitro inhalation bioaccessibility. Lower concentrations of heavy metals were found in the MC samples than in the JP and the JU samples. The average concentrations of Pb, Cd and Cu in the portions of the same size are in the order of JP samples > JU samples > MC samples. For Pb, Cd and Zn, the maximum inhalation bioaccessibility fraction values are all found in the MC samples, which ranged 3.87–8.79%, while those of the JP and the JU samples are <2%. The Pb speciation analysis with X-ray absorption spectrometry indicate mineral bound Pb, PbS and Pb₃(PO₄)₂ are the predominant Pb species in the JP samples; for the JU sample, organic bound Pb is the predominant Pb species in the 45–125 μm portion, while mineral bound Pb is the predominant Pb species in the 10–45 μm portion; for the MC samples, organic bound Pb is the predominant Pb species, followed by PbS. The results indicate that there is significant accumulation of Pb, Cd, Cu and Zn associated with PM in the area near the lead smelter and in the urban area of Jiyuan, especially Pb and Cd, however, the inhalation bioaccessibility of these metals in samples from the lead smelting impacted area is low, this may be due to the higher proportion of less soluble species of the metals in the samples from this area. However, organic matter bound Pb found in some samples has higher bioaccessibility than other Pb species.
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27735. 题目: Dynamics of available and enzymatically hydrolysable soil phosphorus fractions during repeated freeze-thaw cycles
文章编号: N19032103
期刊: Geoderma
作者: Dasheng Sun, Xinbing Yang, Chunling Wang, Xianjun Hao, Jianping Hong, Xianyong Lin
更新时间: 2019-03-21
摘要: Freeze-thaw cycles strongly affect the transformation of soil phosphorus (P) and shape the composition of P pools. This study aimed to investigate the effects of successive freeze-thaw cycles on the transformation of soil labile P and enzymatically hydrolysable organic P (Po) fractions. Accordingly, five physico-chemically distinct soils were subjected to two, five, and ten freeze-thaw cycles, with each cycle including incubation at −10 °C (freeze) for 12 h and 5 °C (thaw) for 12 h. Control soils were maintained at 5 °C, and the bicarbonate-extractable P and hydrolysable P_o fractions were analysed at the end of the incubation period (10 d). Freeze-thaw cycles increased the levels of bicarbonate-extractable inorganic P, bicarbonate-extractable P_o, labile monoester P, and phytate-like P, but had no effect on the diester P and unknown P_o contents. The interaction between soil type and freeze-thaw cycles significantly affected the NaHCO₃-extractable P_i, and phytate-like P fractions, but did not affect the bicarbonate-extractable P_o, and labile monoester P fractions. The extent of increase in NaHCO₃-extractable P_i largely depended on the amount of organic matter in the soil. In most cases, bicarbonate-extractable P and hydrolysable P_o fractions reached their maximum levels after two freeze-thaw cycles and declined or remained constant thereafter. Our results suggest that freeze-thaw cycles exacerbated the transformation of soil labile P fractions, including enzymatically hydrolysable P_o species, especially in the earlier stages.

27736. 题目: Roots of non-woody perennials accelerated long-term soil organic matter decomposition through biological and physical mechanisms
文章编号: N19032102
期刊: Soil Biology and Biochemistry
作者: Jiayu Lu, Feike A. Dijkstra, Peng Wang, Weixin Cheng
更新时间: 2019-03-21
摘要: The rhizosphere priming effect (RPE) is increasingly recognized as an important factor in mediating soil organic matter (SOM) decomposition, which influences the CO₂ release from terrestrial systems to the atmosphere. However, little is known about the long-term RPE of non-woody perennial species and the physical mechanisms underlying the RPE. Here the RPEs of three non-woody perennials (Stipa grandis, Leymus chinensis, Medicago sativa) differing in root traits and exudation were quantified using a natural ¹³C tracer method (C₃ plant - C₄ soil system) during a 476-day experiment. The results indicated that all plant species showed positive RPEs, with M. sativa showing the largest RPE and S. grandis the smallest RPE. Differences in the RPEs between species are likely associated with differences in root biomass, length, and exudates. Furthermore, the positive RPEs of the three species increased continuously with sampling time, indicating the long-term nature of the RPE. Results from structural equation modeling indicated that plant roots accelerated SOM decomposition via three mechanisms. The first mechanism (biological) was through the positive effect on dissolved organic C and microbial biomass C by the presence of the rhizosphere, consistent with the microbial activation hypothesis. The second mechanism (biological) was where plant roots significantly reduced soil mineral N and in turn promoted SOM decomposition, providing support for the microbial N-mining hypothesis. The third mechanism (physical) was where plant roots caused a net positive effect on SOM decomposition through net destruction of macroaggregates possibly as a result of high root length density and the associated drying-rewetting cycles. Overall, this study provides the first experimental evidence for the aggregate destruction hypothesis as a physical mechanism causing the RPE and highlights the importance of multiple mechanisms of the RPE on long-term SOM decomposition.

27737. 题目: Manure over crop residues increases soil organic matter but decreases microbial necromass relative contribution in upland Ultisols: Results of a 27-year field experiment
文章编号: N19032101
期刊: Soil Biology and Biochemistry
作者: Guiping Ye, Yongxin Lin, Yakov Kuzyakov, Deyan Liu, Jiafa Luo, Stuart Lindsey, Weijin Wang, Jianbo Fan, Weixin Ding
更新时间: 2019-03-21
摘要: Organic fertilizers increase soil organic matter (SOM) stocks, but the underlying processes depend on the fertilizer type and remain largely unknown. To evaluate the predominant C stabilization mechanisms, upland Ultisols subjected to 27 years of mineral and organic fertilization were analyzed for SOM content, aggregate size classes, and amino sugar composition. The long-term field experiment had seven treatments: no fertilization (Control), mineral NPK fertilizers (NPK), NPK plus lime (NPK + Lime), NPK plus peanut straw (NPK + PeanutStraw), NPK plus rice straw (NPK + RiceStraw), NPK plus radish residue (NPK + RadishResidue), and NPK plus pig manure (NPK + PigManure). The 27-year application of mineral fertilizers (NPK and NPK + Lime), NPK + crop residues, and NPK + PigManure increased SOM content by 11.0–13.2%, 16.3–25.3%, and 44.3%, respectively, compared with the Control. The aliphaticity and recalcitrance indices based on ¹³C nuclear magnetic resonance spectra of organic fertilizers were higher for pig manure than for crop residues. Both indices were closely correlated with SOM content after 27 years, so higher proportions of recalcitrant C in manure facilitated SOM accumulation. NPK + PigManure increased the mass proportion of large macroaggregates 2.9-fold compared with the Control, and reduced the effective diffusion coefficient of oxygen in the soil. Consequently, NPK + PigManure limited the activity and abundance of aerobes and the accessibility of SOM to microorganisms, in turn facilitating SOM accumulation. The application of mineral fertilizers, NPK + crop residues, and NPK + PigManure increased microbial necromass to 2.85–3.03, 3.21–3.45, and 3.62 g C kg⁻¹, respectively, from 2.63 g C kg⁻¹ in the Control. Compared with crop residues, pig manure did not affect bacterial necromass but increased fungal necromass from 2.19 to 2.39 g C kg⁻¹ to 2.58 g C kg⁻¹, which might associate with increased SOM stability. However, the relative contribution of microbial necromass to SOM was lower under NPK + PigManure than under NPK + crop residues, since more added C was protected in the NPK + PigManure soil. Our results suggest that manure may contribute to SOM accumulation and stabilization in three ways: directly through the input of recalcitrant organic C, indirectly through the stabilization of aggregates and physical protection of C, and to a lesser extent through increasing fungal necromass.

27738. 题目: Liquid chromatographic isolation of individual carbohydrates from environmental matrices for stable carbon analysis and radiocarbon dating
文章编号: N19032016
期刊: Analytica Chimica Acta
作者: Amel Nouara, Christos Panagiotopoulos, Jérôme Balesdent, Kalliopi Violaki, Edouard Bard, Yoann Fagault, Daniel James Repeta, Richard Sempéré
更新时间: 2019-03-20
摘要: Carbohydrates are among the most abundant organic molecules in both aquatic and terrestrial ecosystems; however, very few studies have addressed their isotopic signature using compound-specific isotope analysis, which provides additional information on their origin (δ13C) and fate (Δ14C). In this study, semi-preparative liquid chromatography with refractive index detection (HPLC-RI) was employed to produce pure carbohydrate targets for subsequent offline δ13C and Δ14C isotopic analysis. δ13C analysis was performed by elemental analyzer-isotope ratio mass spectrometer (EA-IRMS) whereas Δ14C analysis was performed by an innovative measurement procedure based on the direct combustion of the isolated fractions using an elemental analyzer coupled to the gas source of a mini carbon dating system (AixMICADAS). In general, four successive purifications with Na+, Ca2+, Pb2+, and Ca2+ cation-exchange columns were sufficient to produce pure carbohydrates. These carbohydrates were subsequently identified using mass spectrometry by comparing their mass spectra with those of authentic standards. The applicability of the proposed method was tested on two different environmental samples comprising marine particulate organic matter (POM) and total suspended atmospheric particles (TSP). The obtained results revealed that for the marine POM sample, the δ13C values of the individual carbohydrates ranged from −18.5 to −16.8‰, except for levoglucosan and mannosan, which presented values of −27.2 and −26.2‰, respectively. For the TSP sample, the δ13C values ranged from −26.4 to −25.0‰. The galactose and glucose Δ14C values were 19 and 43‰, respectively, for the POM sample. On the other hand, the levoglucosan radiocarbon value was 33‰ for the TSP sample. These results suggest that these carbohydrates exhibit a modern age in both of these samples. Radiocarbon HPLC collection window blanks, measured after the addition of phthalic acid (14C free blank), ranged from −988 to −986‰ for the abovementioned compounds, indicating a very small background isotopic influence from the whole purification procedure. Overall, the proposed method does not require derivatization steps, produces extremely low blanks, and may be applied to different types of environmental samples.

27739. 题目: The deep water of Eastern Mediterranean Sea is a hotspot for bacterial activity
文章编号: N19032015
期刊: Deep Sea Research Part II: Topical Studies in Oceanography
作者: Eyal Rahav, Jacob Silverman, Ofrat Raveh, Or Hazan, Maxim Rubin-Blum, Christina Zeri, Alexandra Gogou, Martina Kralj, Alexandra Pavlidou, Nurit Kress
更新时间: 2019-03-20
摘要: We investigated the abundance and production of mesopelagic (150–650 m) and bathypelagic (>650 m) bacteria from the poorly-studied Levantine basin (Eastern Mediterranean Sea) during the summers of 2014–2017. We show that the mesopelagic and bathypelagic microbial populations have relatively high cell specific activity, amongst the highest worldwide, likely due to the relatively warm temperatures characterizing these depths in comparison to other oceanic regions. Furthermore, in order to investigate if mesopelagic and bathypelagic microbial populations are limited by the scarce organic carbon substrates in the area, we performed microcosm addition assays of pure glucose (Glu) and/or a mixture of dissolved free amino acids (DFAA). Both the mesopelagic and bathypelagic bacterial populations responded positively to the additions, with bacterial production rapidly increasing within a few hours following the Glu or DFAA amendments. Our results demonstrate that deep-water microbes in the Levantine Basin may be important nutrient recyclers, especially when labile organic carbon is introduced. Our observations may have implications on carbon cycling and sequestration in the oligotrophic Eastern Mediterranean Sea.

27740. 题目: Evaluating CENTURY and Yasso soil carbon models for CO2 emissions and organic carbon stocks of boreal forest soil with Bayesian multi‐model inference
文章编号: N19032014
期刊: European Journal of Soil Science
作者: Boris Ťupek, Samuli Launiainen, Mikko Peltoniemi, Risto Sievänen, Jari Perttunen, Liisa Kulmala, Timo Penttilä, Antti‐Jussi Lindroos, Shoji Hashimoto, Aleksi Lehtonen
更新时间: 2019-03-20
摘要: We can curb climate change by improved management decisions for the most important terrestrial carbon pool, soil organic carbon stock (SOC). However, we need to be confident we can obtain the correct representation of the simultanous effect of the input of plant litter, soil temperature and water (that could be altered by climate or management) on the decomposition of soil organic matter. In this research, we used regression and Bayesian statistics for testing process based models (Yasso07, Yasso15 and CENTURY) with soil heterotrophic respiration (Rh) and SOC, measured at four sites in Finland during 2015 and 2016. We extracted climate modifiers for calibration with Rh. The Rh values of Yasso07, Yasso15 and CENTURY models estimated with default parameterization correlated with measured monthly heterotrophic respiration. Despite a significant correlation, models on average underestimated measured soil respiration by 43%. After the Bayesian calibration, the fitted climate modifier of the Yasso07 model outperformed the Yasso15 and CENTURY models. The Yasso07 model had smaller residual mean square errors and temperature and water functions with fewer, thus more efficient, parameters than the other models. After calibration, there was a small overestimate of Rh by the models that used monotonic moisture functions and a small generic underestimate in autumn. The mismatch between measured and modelled Rh indicates that the Yasso and CENTURY models should be improved by adjusting climate modifiers of decomposition or by accounting for missing controls in e.g. microbial growth.