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24501. 题目: Analysis of ¹²⁹I and ¹²⁷I in soils of the Chernobyl Exclusion Zone, 29 years after the deposition of ¹²⁹I
文章编号: N19072104
期刊: Science of The Total Environment
作者: George Shaw, Elizabeth Bailey, Neil Crout, Lorraine Field, Stewart Freeman, Sergey Gaschak, Xiaolin Hou, Maria Izquierdo, Claire Wells, Sheng Xu, Scott Young
更新时间: 2019-07-21
摘要: The Chernobyl Exclusion Zone (CEZ) represents a unique natural laboratory that received significant ¹²⁹I contamination across a range of soils and land-use types in a short time period in 1986. Data are presented on ¹²⁹I and ¹²⁷I in soil samples collected from highly contaminated areas in the CEZ in 2015. The geometric mean (GM) total concentration of stable iodine (¹²⁷I) was 6.7 × 10⁻⁷ g g⁻¹ and the (GM) total concentration of ¹²⁹I was 2.39 × 10⁻¹³ g g⁻¹, equivalent to 1.56 mBq kg⁻¹. GM total ¹²⁷I concentration is below the European average soil concentration of 3.94 × 10⁻⁶ g g⁻¹, while ¹²⁹I is significantly higher than the pre-Chernobyl activity concentration for ¹²⁹I of 0.094 mBq kg⁻¹. Significant differences were found in the extractability of native, stable ¹²⁷I and ¹²⁹I almost 30 years after the introduction of ¹²⁹I to the soils. Both ¹²⁷I and ¹²⁹I were predominantly associated with alkaline-extractable soil organic matter, established using a three-step sequential extraction procedure. Whereas ¹²⁷I was significantly correlated with gross soil organic matter (measured by loss on ignition), however, ¹²⁹I was not. The ratio of ¹²⁹I/¹²⁷I was significantly lower in extracts of soil organic matter than in more labile (soluble and adsorbed) fractions, indicating incomplete equilibration of ¹²⁹I with native ¹²⁷I in soil humic substances after 29 years residence time in the CEZ soils. The initial physico-chemical form of ¹²⁹I in the CEZ soils is unknown, but the widespread presence of uranium oxide fuel particles is unlikely to have influenced the environmental behaviour of ¹²⁹I. Our findings have implications for long-term radiation dose from ¹²⁹I in contaminated soils and the use of native, stable ¹²⁷I as a proxy for the long-term fate of ¹²⁹I.
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24502. 题目: Hyperthermophilic composting reduces nitrogen loss via inhibiting ammonifiers and enhancing nitrogenous humic substance formation
文章编号: N19072103
期刊: Science of The Total Environment
作者: Peng Cui, Hanpeng Liao, Yudan Bai, Xi Li, Qian Zhao, Zhi Chen, Zhen Yu, Zhigang Yi, Shungui Zhou
更新时间: 2019-07-21
摘要: Composting is an efficient and economic approach used to convert organic waste into organic fertilizers. However, the substantial nitrogen loss during the composting process is one of the major disadvantages of conventional thermophilic composting (cTC). Here, we demonstrated for the first time that hyperthermophilic composting (hTC) was able to mitigate nitrogen loss by 40.9% compared to cTC after 44 days of composting in a full-scale plant. Results demonstrate a decrease in NH₃ volatilization (52.4%), together with an inhibitory effect on protease (19.4–87.5%) and urease (9.1–75.2%) enzyme activities and the ammonification rate (5.2–80.1%) for hTC. Additionally, this study found that hTC could accelerate the humification process, thereby enhancing the formation of the recalcitrant nitrogen reservoir (mainly in the form of nitrogenous humic substances) and reducing the substrate for ammonification reactions. These findings suggest that hTC can significantly reduce nitrogen loss and provide insights into the role of humic substances in nitrogen retention in composting systems.
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24503. 题目: The impact of cell morphology and algal organic matter on algal floc properties
文章编号: N19072102
期刊: Water Research
作者: A. Gonzalez-Torres, M. Pivokonsky, R.K. Henderson
更新时间: 2019-07-21
摘要: Physical floc properties were systematically investigated by analysing the structure of algal and cyanobacterial flocs produced by five species (green algae (Chlorella vulgaris) and cyanobacteria (Microcystis aeruginosa (strain CS-564), Microcystis aeruginosa (strain CS-555/01), Dolichospermum circinale and Cylindrospermopsis raciborskii) using aluminium sulphate (alum) at different doses and pH values. The properties of spherical, compact flocs were determined using a laser diffraction instrument and a new in situ image analysis technique was validated to analyse the structure of more complex flocs. The incorporation of algal-derived organic matter (AOM) into the flocs was inferred by evaluating the dissolved organic matter concentration character before and after flocculation using liquid chromatography with organic carbon detection (LC-OCD). D. circinale, C. raciborskii, and M. aeruginosa (CS-564) produced large flocs (2–9 mm), while M. aeruginosa (CS-555) and C. vulgaris produced smaller flocs (<2 mm). While differences in physical floc properties were observed to result from changes in coagulation mechanism, the cell morphology and the AOM composition were the most influential factors. Examination of floc properties can give a rapid insight at the plant for trouble shooting, particularly through the use of the in situ techniques and provide a mechanism by which floc properties can be tailored to downstream processes.
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24504. 题目: Biochar from Acai agroindustry waste: Study of pyrolysis conditions
文章编号: N19072101
期刊: Waste Management
作者: Michel Keisuke Sato, Herdjania Veras de Lima, Aline Noronha Costa, Sueli Rodrigues, Augusto José Silva Pedroso, Claudia Maria Branco de Freitas Maia
更新时间: 2019-07-21
摘要: The production chain of Acai (Euterpe oleracea Mart) has a high economic representativeness in the Brazilian Amazon. However, wastes generated from the processing of the fruit has been deliberately discarded in the environment, causing health risks to the population due to environmental contamination or the proliferation of disease agents. Thus, the production of biochar arises as an alternative to the irregular disposal of these residues. The objective of this work was to evaluate the conditions (temperature and residence time) to produce biochar from Acai processing residues and its potential for use as soil conditioner in the Amazon region. Acai seeds were carbonized using the process of muffle pyrolysis at different temperatures and residence times. Biochars were evaluated for their physical and chemical properties and hydrophobicity. The temperature had a greater influence than the residence time for most parameters. Higher values of pH, higher recalcitance and greater potential for water retention were observed for the biochar produced at temperatures of 600 and 700 °C. At lower temperatures (300 and 400 °C), a greater yield was observed, however, in this condition, the material presented an extremely hydrophobic character. By considering the favorable agronomic characteristics of biochar, the temperature of 600 °C and residence time of 60 min are the most suitable conditions for the production of biochar from Acai seeds.

24505. 题目: Interactive effects of microplastics and glyphosate on the dynamics of soil dissolved organic matter in a Chinese loess soil
文章编号: N19072014
期刊: CATENA
作者: Hongfei Liu, Xiaomei Yang, Chutao Liang, Yuanze Li, Leilei Qiao, Zemin Ai, Sha Xue, Guobin Liu
更新时间: 2019-07-20
摘要: The increased use of plastic films and pesticides on agricultural soil leads to the accumulation of plastic debris and pesticide residues in soil. This accumulation has become a serious environmental issue, as it threatens life of earthworms, inhibits the enzyme activities and microbial diversity, and contributes to the loss of soil microbial carbon and nitrogen. However, little information is available regarding the effects of pesticides on soil dissolved organic matter (DOM). It is also unknown how plastic debris, especially small-sized particles called microplastics, influences the effects of pesticides on soil DOM. In this study, we performed a 30-day soil incubation experiment. Three levels of the common herbicide glyphosate were applied to soil: 0 (control, CK), 3.6 kg ha⁻¹ (G1) and 7.2 kg ha⁻¹ (G2). We also tested four levels of glyphosate and microplastics (homopolymer polypropylene powder) co-addition: 3.6 kg ha⁻¹ + 7% (w/w) (M1G1), 3.6 kg ha⁻¹ + 28% (w/w) (M2G1), 7.2 kg ha⁻¹ + 7% (w/w) (M1G2), and 7.2 kg ha⁻¹ + 28% (w/w) (M2G2). Glyphosate addition slightly increased soil fluorescein diacetate hydrolase (FDAse) and phenol oxidase (PO) activities. Although the glyphosate addition significantly promoted the accumulation of dissolved organic phosphorus (DOP) within the first 14 days, the M2 treatment decreased DOP at day 30. M2G1 and M2G2 increased soil FDAse activity and promoted the accumulation of DOC and DOP relative to G1 and G2 respectively while M1G1 and M1G2 benefited DON accumulation. Our results highlighted that the interaction between glyphosate and low microplastics content negatively affected DOC and DOP dynamics, leading to the loss of bioavailable C and P loss. The interaction between glyphosate and high content microplastics negatively affected DON compared with glyphosate addition, possibly decreasing DON.
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24506. 题目: Structural changes of soil organic matter and the linkage to rhizosphere bacterial communities with biochar amendment in manure fertilized soils
文章编号: N19072013
期刊: Science of The Total Environment
作者: Ruilin Huang, Zhenyi Zhang, Xian Xiao, Na Zhang, Xiaoyue Wang, Zeping Yang, Kaiqin Xu, Yuting Liang
更新时间: 2019-07-20
摘要: The molecular structure of soil organic matter (SOM) is closely related to the structure and functions of the rhizosphere community. In this study, a microcosm experiment was conducted to investigate the effect of straw-derived biochar on the structural differentiation of SOM and rhizosphere bacterial communities. ¹³C NMR spectra showed that the relative abundance of carboxyl, alkyl, N-alkyl, O-alkyl and methoxyl groups decreased by 22%, 31%, 27%, 27% and 27%, respectively, and the relatively stable structure of aryl and O-aryl groups increased by 213% and 41%, respectively. In addition, network-based analysis showed that biochar amendment not only improved the network connectivity of the rhizosphere bacteria, but also enhanced the linkage between bacteria and the molecular structure of SOM. The topological properties of the network, including the number of edges, network density, and average clustering coefficient, were increased by 79%, 15% and 22%, respectively. Moreover, modularization analysis and structural equation model indicated that rhizosphere bacterial network was the important bio-factor affecting the content of labile carbon.
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24507. 题目: Mineral vs. organic matter supply as a limiting factor for the formation of mineral-associated organic matter in forest and agricultural soils
文章编号: N19072012
期刊: Science of The Total Environment
作者: Xiang Wang, Brandy M. Toner, Kyungsoo Yoo
更新时间: 2019-07-20
摘要: Physical and chemical interactions between soil organic matter (OM) and minerals is one of the primary mechanisms for stabilizing OM in terrestrial ecosystems. Focusing on OM association with mineral surfaces, this study sought to examine mineral-associated OM from the perspectives of both mineral surface characteristics and organic matter chemistry. The research was conducted at paired-sites under North American Mid-Atlantic Coastal forest and crop production with shared environmental factors. Using carbon (C) and nitrogen (N) 1s micro- X-ray absorption near-edge fine structure (XANES) spectroscopy, we investigated the amounts and types of mineral-associated OM. Mineral specific surface area (SSA) of bulk soil was determined for three conditions: untreated, post OM removal and post iron (Fe) (oxyhydr)oxides removal. Amounts of mineral-associated OM were smaller in the agricultural soil, where greater SSA sourced from clay-sized phyllosilicates and Fe (oxyhydr)oxide minerals did not result in greater OM coverage of the mineral surface area. Although agricultural surface soil showed less abundance of phenolic C, speciation of mineral-associated OM did not differ between comparable horizons. Our results suggest that despite the plow-derived mixing of soil, which increased SSA and secondary minerals available to interact physically and chemically with OM in the plowed layer, the formation of mineral-associated OM in agricultural soil is ultimately limited by available OM.
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24508. 题目: Sharp contrasts between freshwater and marine microbial enzymatic capabilities, community composition, and DOM pools in a NE Greenland fjord
文章编号: N19072011
期刊: Limnology and Oceanography
作者: John Paul Balmonte, Harald Hasler‐Sheetal, Ronnie N. Glud, Thorbjørn J. Andersen, Mikael K. Sejr, Mathias Middelboe, Andreas Teske, Carol Arnosti
更新时间: 2019-07-20
摘要: Increasing glacial discharge can lower salinity and alter organic matter (OM) supply in fjords, but assessing the biogeochemical effects of enhanced freshwater fluxes requires understanding of microbial interactions with OM across salinity gradients. Here, we examined microbial enzymatic capabilities—in bulk waters (nonsize‐fractionated) and on particles (≥ 1.6 μm)—to hydrolyze common OM constituents (peptides, glucose, polysaccharides) along a freshwater–marine continuum within Tyrolerfjord‐Young Sound. Bulk peptidase activities were up to 15‐fold higher in the fjord than in glacial rivers, whereas bulk glucosidase activities in rivers were twofold greater, despite fourfold lower cell counts. Particle‐associated glucosidase activities showed similar trends by salinity, but particle‐associated peptidase activities were up to fivefold higher—or, for several peptidases, only detectable—in the fjord. Bulk polysaccharide hydrolase activities also exhibited freshwater–marine contrasts: xylan hydrolysis rates were fivefold higher in rivers, while chondroitin hydrolysis rates were 30‐fold greater in the fjord. Contrasting enzymatic patterns paralleled variations in bacterial community structure, with most robust compositional shifts in river‐to‐fjord transitions, signifying a taxonomic and genetic basis for functional differences in freshwater and marine waters. However, distinct dissolved organic matter (DOM) pools across the salinity gradient, as well as a positive relationship between several enzymatic activities and DOM compounds, indicate that DOM supply exerts a more proximate control on microbial activities. Thus, differing microbial enzymatic capabilities, community structure, and DOM composition—interwoven with salinity and water mass origins—suggest that increased meltwater may alter OM retention and processing in fjords, changing the pool of OM supplied to coastal Arctic microbial communities.

24509. 题目: Efficient microalgae removal from aqueous medium through auto-flocculation: investigating growth-dependent role of organic matter
文章编号: N19072010
期刊: Environmental Science and Pollution Research
作者: Naim Rashid, Manoranjan Nayak, William I. Suh, Bongsoo Lee, Yong-Keun Chang
更新时间: 2019-07-20
摘要: This study investigated the growth-dependent role of algal organic matters (AOMs) to achieve high removal efficiency (R.E) of microalgae. The results showed that the microalgae cells produced 96 ± 2% of total AOMs as loose bound AOMSS (LB-AOMs) and 4 ± 1% as cell-bound (CB-AOMs) in exponential phase. In stationary phase, LB-AOMs and CB-AOMs were 46 ± 0.7percentage and 54 ± 0.2 percentage, respectively. The R.Es in exponential and stationary phase were 83 ± 2.6% and 66 ± 1.2%, respectively. It is found that the difference of biomass concentration (between exponential and stationary phase) had no significant impact on the R.E (P > 0.01). Further investigations revealed that LB-AOMs inhibit flocculation in exponential and CB-AOMs in stationary phase; however, CB-AOMs showed stronger inhibition than the LB-AOMs (P < 0.01). The provision of calcium (17 ± 0.9 mg/L) to the culture reduced the AOMs inhibition and improved the R.E from 66 ± 1.2% (in control) to 90 ± 4.2%. An increase in R.E was attributed to the interaction of calcium with AOMs and subsequently acting as a flocculant. The findings of this study can be valuable to improve the performance of auto-flocculation technology, which is mainly limited by the presence of AOMs.

24510. 题目: Photochemical consequences of prolonged hydrological drought: A model assessment of the Lower Lakes of the Murray-Darling Basin (Southern Australia)
文章编号: N19072009
期刊: Chemosphere
作者: Luca Carena, Dario Terrenzio, Luke M. Mosley, Marco Toldo, Marco Minella, Davide Vione
更新时间: 2019-07-20
摘要: The prolonged “Millennium” drought affecting Australia in the 2000s had important consequences on surface-water bodies, including the Lower Lakes (Lake Alexandrina and Lake Albert) located at the terminal end of the River Murray system. Shallower water depths, limited solute dilution and altered geochemical processes ensured that the concentration values of several water constituents increased considerably during drought, including the water parameters of photochemical significance (nitrate, bicarbonate, carbonate and the dissolved organic carbon, DOC). The aim of this study was to model the photochemical processes in the Lower Lakes during the drought and post-drought periods, to provide insight into the changes that photoinduced reactions can undergo in periods of water scarcity. Among the photochemical processes involved in the light-assisted transformation of dissolved compounds, an important role is played by indirect photochemistry where degradation is triggered by photogenerated transient species such as hydroxyl (OH) and carbonate (CO₃⁻) radicals, and the triplet states of chromophoric dissolved organic matter (³CDOM*). Results of photochemical modelling suggest that the reactions induced by ³CDOM* would be enhanced during drought, while the processes triggered by OH and CO₃⁻ would be less modified. For compounds undergoing efficient degradation with ³CDOM*, enhanced photochemistry during drought could offset the higher concentration values resulting from lower dilution. In contrast, for compounds mainly degraded by OH or CO₃⁻ the drought period could produce a concentration increase not balanced by an increment in the photochemical reactivity of the water body.
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24511. 题目: Heavy metal behaviour at mineral-organo interfaces: Mechanisms, modelling and influence factors
文章编号: N19072008
期刊: Environment International
作者: Chenchen Qu, Wenli Chen, Xiping Hu, Peng Cai, Chengrong Chen, Xiao-Ying Yu, Qiaoyun Huang
更新时间: 2019-07-20
摘要: The mineral-organo composites control the speciation, mobility and bioavailability of heavy metals in soils and sediments by surface adsorption and precipitation. The dynamic changes of soil mineral, organic matter and their associations under redox, aging and microbial activities further complicate the fate of heavy metals. Over the past decades, the wide application of advanced instrumental techniques and modelling has largely extended our understanding on heavy metal behavior within mineral-organo assemblages. In this review, we provide a comprehensive summary of recent progress on heavy metal immobilization by mineral-humic and mineral-microbial composites, with a special focus on the interfacial reaction mechanisms of heavy metal adsorption. The impacts of redox and aging conditions on heavy metal speciations and associations with mineral-organo complexes are discussed. The modelling of heavy metals adsorption and desorption onto synthetic mineral-organo composites and natural soils and sediments are also critically reviewed. Future challenges and prospects in the mineral-organo interface are outlined. More in-depth investigations are warranted, especially on the function and contribution of microorganisms in the immobilization of heavy metals at the complex mineral-organo interface. It has become imperative to use the state-of-the-art methodologies to characterize the interface and develop in situ analytical techniques in future studies.

24512. 题目: Redox properties and dechlorination capacities of landfill-derived humic-like acids
文章编号: N19072007
期刊: Environmental Pollution
作者: Xiao Xiao, Bei-Dou Xi, Xiao-Song He, Hui Zhang, Yan-Hong Li, Shengyan Pu, Si-Jia Liu, Min-Da Yu, Chao Yang
更新时间: 2019-07-20
摘要: Electron transfer capacities (ETC) of humic-like acids (HLA) and their effects on dechlorination are dependent on their redox-active properties. Aging and minerals can affect the chemical compositions and structures of HLA. However, the underlying mechanism and the impacts on the dechlorination capacities of HLA are poorly understood. We investigated how redox properties change in association with the intrinsic chemical natures and exterior minerals of the HLA extracted from landfilled solid wastes. Furthermore, the ETC of the landfill-derived HLA could be strengthened by increasing landfill age and demineralization, thereby facilitating the dechlorination of pentachlorophenol (PCP). The HLA molecules started to polymerize aromatic macromolecules during landfilling, leading to an increase in ETC and dechlorination capacities. Macromolecular HLA were dissociated to smaller molecules and exposed more aromatic and carboxyl groups when separated from minerals, which enhanced the ETC and the dechlorination abilities of the HLA. Microbial-mediated dechlorination was an effective way to degrade PCP, and almost 80% of the PCP was transformed after 40 days of demineralized HLA and Shewanella oneidensis MR-1 incubation. The demineralization and aging further facilitated the microbial-mediated PCP dechlorination. The findings provide a scientific base for improving in-situ bioremediation of chlorinated compound-contaminated soils using freshly synthesized HLA.
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24513. 题目: Deep soil carbon storage in tree-dominated land use systems in tropical lowlands of Kalimantan
文章编号: N19072006
期刊: Geoderma
作者: Nils Borchard, Medha Bulusu, Nele Meyer, Andrei Rodionov, Hety Herawati, Sergey Blagodatsky, Georg Cadisch, Gerd Welp, Wulf Amelung, Christopher Martius
更新时间: 2019-07-20
摘要: Although carbon (C) stored deep in soils of tree-dominated land use systems in the tropics represents a large reservoir of organic matter its vulnerability to land use change has been hardly assessed. To fill this gap, we sampled Acrisols down to 3 m under three different land use systems; namely, recent cacao agroforestry (<2 years old; not deeper than 1 m), young and old rubber gardens (<10 years and >50 years), and secondary forest (>50 years) all located in Kapuas Hulu regency, West Kalimantan, Indonesia. We then assessed soil organic carbon (SOC) stocks as well as C accumulated in above- and belowground biomass, litter and dead wood debris at the soil surface. The amount of C stored in soils to a depth of 1 m exceeded the amount stored in living biomass (Σ C stored in roots, understorey and overstorey) strongly in the cacao agroforestry systems (69 Mg SOC vs. 12 Mg biomass-C ha⁻¹), slightly in young rubber gardens (85 Mg SOC vs. 69 Mg C ha⁻¹), but not in old rubber gardens (87 Mg SOC vs. 200 Mg C ha⁻¹) and secondary forests (65 Mg SOC vs. 138 Mg C ha⁻¹). Additionally in the older systems, up to 140 Mg C ha⁻¹ (old rubber gardens) and 116 Mg C ha⁻¹ (secondary forest) were found in soils to a depth of 3 m, thus raising soil C stocks by 60 to 80% relative to C stored in upper soil (0 to 1 m). We conclude that (1) the form of land use and land use change can substantially affect C stocks in living biomass, with aboveground biomass in old rubber gardens comparable to that of secondary forests; and (2) that land use change can reduce SOC in topsoil, but that substantial C stocks found in deep (down to 3 m) subsoil remain stable.

24514. 题目: Spent mushroom substrate and cattle manure amendments enhance the transformation of garden waste into vermicomposts using the earthworm Eisenia fetida
文章编号: N19072005
期刊: Journal of Environmental Management
作者: Xiaoqiang Gong, Suyan Li, Michael A. Carson, Scott X. Chang, Qian Wu, Li Wang, Zhengfeng An, Xiangyang Sun
更新时间: 2019-07-20
摘要: Garden wastes (GW) having high lignin contents could hinder the growth of earthworms and microorganisms in vermicomposting. This study investigated the Eisenia fetida-based vermicomposting of GW mixed with cattle manure (CM) and/or spent mushroom substrate (SMS) at different ratios of GW alone (control), 3:1 GW:SMS, 1:1 GW:SMS, 3:1 GW:CM, 1:1 GW:CM and 2:1:1 GW:SMS:CM to promote earthworm growth and improve the final vermicompost quality. In general, treatments with the addition of SMS and/or CM increased the survival rate, biomass, cocoon and juvenile numbers of E. fetida compared to the control. The addition of SMS and/or CM also significantly increased the activities of dehydrogenase, cellulase, urease, and alkaline phosphatase compared to the control. Furthermore, the addition of SMS and/or CM facilitated the decomposition of organic matter, cellulose and lignin, increased nutrient (N, P and K) concentrations, and accelerated nitrification compared to the control. The addition of SMS and CM led to greater chemical changes of the substrate compared to control. Heavy metal concentrations were increased in the final vermicomposts comparatively to the initial materials, but none of them exceeded the permissible limits. The highest germination index of Chinese cabbage and tomato seeds were both observed in the treatment of 2:1:1 GW:SMS:CM which reached 146.9 and 148.1. Overall, the 2:1:1 GW:SMS:CM treatment had the highest growth and reproduction rates of E. fetida, higher percentage degradation of organic matter, cellulose and lignin, as well as the best quality of the final vermicompost.
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24515. 题目: Influence of sediment parameters on the distribution and fate of PAHs in an estuarine tropical region located in the Brazilian semi-arid (Jaguaribe River, Ceará coast)
文章编号: N19072004
期刊: Marine Pollution Bulletin
作者: Márcia V.F. Andrade, Felipe R. Santos, André H.B. Oliveira, Ronaldo F. Nascimento, Rivelino M. Cavalcante
更新时间: 2019-07-20
摘要: 18 polycyclic aromatic hydrocarbons (PAHs) were evaluated in the Jaguaribe River to explore the influence of grain size, organic carbon, humic and fulvic acids and black carbon on their adsorption onto sediment. The ∑PAHs concentrations variated from 0.6 to 3752.0 ng g⁻¹ with highest concentrations in the estuarine zone. The PAHs predominant source along the river was from mixed sources, mainly related to biomass combustion, small oil spills related to recreational nautical activities and runoff from cities. Organic and inorganic parameters presented influence on PAHs distribution along the river, with humic acid as a determinant factor. These research findings are of importance to an assessment of the fate and transport of PAHs in estuarine systems.

24516. 题目: Transport and retention of biogenic selenium nanoparticles in biofilm-coated quartz sand porous media and consequence for elemental mercury immobilization
文章编号: N19072003
期刊: Science of The Total Environment
作者: Xiaonan Wang, Bingshen Liu, Xiangliang Pan, Geoffrey Michael Gadd
更新时间: 2019-07-20
摘要: Bacterial biofilms are structured cell communities embedded in a matrix of extracellular polymeric substances (EPS) and a ubiquitous growth form of bacteria in the environment. A wide range of interactions between biofilms and nanoparticles have been reported. In the present study, the influence of a mixed bacterial biofilm on retention of biogenic selenium nanoparticles (BioSeNPs) and consequences for immobilization of elemental mercury (Hg⁰) in a porous quartz sand system were examined. BioSeNPs were significantly retained in the presence of a biofilm through electrical double layer effects, hydrogen bonding, and hydrophobic, steric and bridging interactions. Moreover, enhanced surface roughness, pore clogging, sieving and entrapment effects mediated by the biofilm also contributed to deposition of BioSeNPs. Whereas, thiol groups associated with the biofilm is a little helpful for the capture of Hg⁰. It is proposed that oxidative complexation between Hg⁰ and thiol compounds or S containing organic matter in the biofilm may result in the formation of Hg²⁺-thiolate complexes and HgS during the binding of Hg⁰ with BioSeNPs. The formation of mercury selenide was also involved in Hg⁰ immobilization in the porous quartz sand system.
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24517. 题目: Adsorption, aggregation and sedimentation of titanium dioxide nanoparticles and nanotubes in the presence of different sources of humic acids
文章编号: N19072002
期刊: Science of The Total Environment
作者: Tianhui Zhao, Mengyuan Fang, Zhi Tang, Xiaoli Zhao, Fengchang Wu
更新时间: 2019-07-20
摘要: Environmental behavior, bioavailability and risks posed by TiO₂, nanomaterials (TiO₂ NMs) in surface waters are affected by morphologies of the particles and geochemistry, including pH, inorganic and organic matter. Here, the adsorption, aggregation and sedimentation of TiO₂ nanoparticles (TiO₂ NPs) and nanotubes (TiO₂ NTs) were investigated in the presence of Elliott Soil humic acid (HA_E) and Suwannee River humic acids (HA_S). The adsorption amount of HA on TiO₂ NMs was inversely proportional to pH of solution. Maximum adsorption amount of HA on the surface of TiO₂ NMs follows the order TiO₂ NPs + HA_E (236.05 mg/g) > TiO₂ NTs + HA_E (146.05 mg/g) > TiO₂ NTs + HA_S (70.66 mg/g) > TiO₂ NPs + HA_S (37.48 mg/g). Stability of TiO₂ NPs and TiO₂ NTs largely depended on their isoelectric point, morphology and solution pH in the absence of HA. Dispersion of TiO₂ NMs was enhanced with solution pH deviated from the isoelectric point of nanomaterials due to electrostatic repulsion. Moreover, tubular structures of TiO₂ NTs with higher length-diameter ratio seem to aggregate more easily than dose sphere-like TiO₂ NPs. This might be due to their spherical structure enhancing steric repulsion. Notably, the adsorption of HA led to disagglomeration and significant stability of TiO₂ NPs and TiO₂ NTs due to steric hindrance under varying solution pH. In addition, adsorption time, concentration and sources of HA also influenced suspension/sedimentation behavior of TiO₂ NPs and TiO₂ NTs, and aromatic-rich HA_E stabilized TiO₂ NMs suspension more aggressively than aliphatic-rich HA_S.
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24518. 题目: The effects of various tillage treatments on soil physical properties, earthworm abundance and crop yield in Hungary
文章编号: N19072001
期刊: Soil and Tillage Research
作者: Igor Dekemati, Barbara Simon, Szergej Vinogradov, Márta Birkás
更新时间: 2019-07-20
摘要: Historically, tillage has been essential for seedbed preparation and weed control, but it has also accelerated soil degradation through erosion and loss of soil organic matter (SOM). Our objective was to quantify the changes in soil physical properties and earthworm abundance under six tillage treatments on an Endocalcic Chernozem (Loamic) soil (2016 and 2017). The long-term tillage experiment was set up in 2002 with the following tillage treatments: disking 12 to 14 cm deep (D); shallow tine cultivation (18 to 20 cm) (SC); no-tillage (NT); deep tine cultivation (22 to 25 cm) (DC); loosening to a depth of 40 to 45 cm (L); moldboard ploughing to a depth of 28 to 30 cm, followed by leveling (P). Soil samples were collected in the autumn of 2015 from four depth increments (0–10, 10–20, 20–30, 30–40 cm). Soil moisture content (SMC), soil penetration resistance (SPR), soil texture, pH(H₂O), soil organic carbon (SOC), and earthworm abundance were measured. SMC and SPR were taken at 30-day intervals unless the weather prevented sampling. Earthworms were sampled in situ seven times per year by hand-sorting 25 × 25 x 30 cm soil blocks. No-tillage had a positive effect on crop yield and earthworm abundance. Compared to conventional tillage (P), SMC and SPR were improved by conservation tillage (DC, SC, D or NT). When measured during the summer months, SPR reached 6 MPa for all tillage treatments due to low SMC. Overall, NT had the highest earthworm abundance while conventional tillage (P) had the lowest. Maize (Zea mays L.) yield was highest with SC (9.32 Mg ha⁻¹), lowest with D (7.92 Mg ha⁻¹). For winter oat (Avena fatua L.), L resulted in the highest yield (5.87 Mg ha⁻¹) but required more time and energy. As weather patterns become more erratic, tillage has the potential to make crop production even riskier. Therefore, to improve both physical and biological soil properties, efforts should be made to decrease tillage intensity each year.

24519. 题目: Photodegradation disproportionately impacts biodegradation of semi‐labile DOM in streams
文章编号: N19071914
期刊: Limnology and Oceanography
作者: Jennifer C. Bowen, Louis A. Kaplan, Rose M. Cory
更新时间: 2019-07-19
摘要: Exposure of dissolved organic matter (DOM) to sunlight can increase or decrease the fraction that is biodegradable (BDOM), but conceptual models fail to explain this dichotomy. We investigated the effect of sunlight exposure on BDOM, addressing three knowledge gaps: (1) how fractions of DOM overlap in their susceptibility to degradation by sunlight and microbes, (2) how the net effect of sunlight on BDOM changes with photon dose, and (3) how rates of DOM photodegradation and biodegradation compare in a stream. Stream waters were exposed to sunlight, and then fed through bioreactors designed to separate labile and semi‐labile pools within BDOM. The net effects of photodegradation on DOM biodegradability, while generally positive, represented the balance between photochemical production and removal of BDOM that was mediated by photon dose. By using sunlight exposure times representative of sunlight exposures in a headwater stream and bioreactors colonized with natural communities and scaled to whole‐stream dynamics, we were able to relate our laboratory findings to the stream. The impact of sunlight exposure on rates of DOM biodegradation in streams was calculated using rates of light absorption by chromophoric DOM, apparent quantum yields for photomineralization and photochemical alteration of BDOM, and mass transfer coefficients for labile and semi‐labile DOM. Rates of photochemical alteration of labile DOM were an order of magnitude lower than rates of biodegradation of labile DOM, but for semi‐labile DOM, these rates were similar, suggesting that sunlight plays a substantial role in the fate of semi‐labile DOM in streams.

24520. 题目: Effect of humic acid on the stabilization of cadmium in soil by coprecipitating with ferrihydrite
文章编号: N19071913
期刊: Environmental Science and Pollution Research
作者: Miaomiao Xu, Zhuanjun Zhao, Miao Shi, Liwei Yao, Tianfeng Fan, Zemin Wang
更新时间: 2019-07-19
摘要: Coprecipitation of humic acid (HA) with ferrihydrite (Fh) has been proposed to reduce the activity of heavy metals in aqueous solutions. The effect of the amount of HA added to the coprecipitates on the stabilization of Cd in soil is unclear. In this research, five different Fh-HA coprecipitates were synthesized to study the impact of different HA additions on the fractionation of Cd in the soil and the optimal addition ratio of C/Fe. Characterization technique as Fourier transform infrared spectroscopy (FT–IR), X–ray diffraction (XRD), specific surface area analyzer, and scanning electron microscopy (SEM) was used in order to test and analyze of the microstructure and physicochemical property of the coprecipitates. The results showed that the Fh-HA coprecipitate is mainly combined by the coordination exchange of –OH on the surface of the Fh with the carboxyl group of the HA. Adding HA could stabilize Fh and increase its surface roughness. Changes in the fractionation of the Cd were used to evaluate the stabilization effect of the coprecipitate. Before treatment, Cd in different contaminated soils was existed only a small amount of residual fraction. After the addition of the Fh-HA coprecipitate, the proportion of residual Cd in each contaminated soil increased. When the C/Fe ratio was 1.5, the maximum residual fraction were 62.94%, 55.67%, and 52.99% respectively. Residual Cd could remain relatively stable indicating that the Fh-HA coprecipitate is a promising amendment for repairing Cd-contaminated soil. The addition of HA has strengthened the active role of Fh on stabilizing heavy metals.