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28741. 题目: Highly efficient nitrate removal in a heterotrophic denitrification system amended with redox-active biochar: a molecular and electrochemical mechanism
文章编号: N18121910
期刊: Bioresource Technology
作者: Zhengsong Wu, Fei Xu, Chun Yan, Xiaoxuan Su, Fucheng Guo, Qinyuan Xu, Guilong Peng, Qiang He, Yi Chen
更新时间: 2018-12-19
摘要: Biochar is widely used in water treatment because of its porous structure, however, the effects of biochars on denitrification remain unclear. Here, we combined molecular biological and electrochemical techniques to investigate effects of biochars (formed at 300 °C, 500 °C and 800 °C) on denitrification. Results showed that biochar at 300 °C increased total nitrogen removal by 415% and decreased N₂O accumulation by 78%. Mechanistic research demonstrated that it achieved the highest electron transfer efficiency and denitrifying enzyme activities. Further study evidenced that biochar at 300 °C increased the abundance of denitrifiers such as Pseudomonas. Correlation analysis indicated that nitrate reductase and nitrite reductase activities were the key factors influenced by biochar during denitrification. Overall, this study suggested that biochar at 300 °C could act as the bio-engineer of electron shuttle and the stimulator of denitrification, achieving high rate nitrogen removal and significant reduction of N₂O accumulation from high-strength wastewater.
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28742. 题目: Assessing arsenic redox state evolution in solution and solid phase during As(III) sorption onto chemically-treated sewage sludge digestate biochars
文章编号: N18121909
期刊: Bioresource Technology
作者: Suchanya Wongrod, Stéphane Simon, Eric D. van Hullebusch, Piet N.L. Lens, Gilles Guibaud
更新时间: 2018-12-19
摘要: This work aimed to determine arsenic redox state distribution during As(III) sorption onto chemically-modified biochars. A solid-liquid extraction protocol using phosphoric (0.3 M) and ascorbic (0.5 M) acids at 80 °C for 20 min was established to ensure a quantitative recovery and stability of As(III) during the extraction. During sorption experiments, the redox conversions of As occurred and As(III) was either stable or partially oxidized in solution. The As distribution strongly varies depending on the biochar chemical treatment performed as well as the selected washing procedures (batch versus column washings). As(III) oxidation was favored with the KOH-modified biochar washed in batch mode. This oxidation was mostly induced by the biochar solid compounds rather than by soluble compounds released in solution. The As redox state distribution of As sorbed onto the biochars was successfully assessed using the extraction procedure. Arsenic was predominantly sorbed as As(III) (76–92%) onto the biochars.
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28743. 题目: The long-term effects of cattle manure application to agricultural soils as a natural-based solution to combat salinization
文章编号: N18121908
期刊: CATENA
作者: Qingfeng Meng, Xianfa Ma, Juan Zhang, Zhitong Yu
更新时间: 2018-12-19
摘要: Excessive exchangeable sodium and high soil pH result in structural destabilization of sodic soil. The long-term application of cattle manure is an important management practice that can affect the physical properties of sodic soil. Experiments were carried out using a randomized complete block design comprising five treatments according to the cattle manure application history: corn (Zea mays L.) fields with annual manure application since 2011 (M2011), 2006 (M2006), 2001 (M2001) and 1995 (M1995) were used as the experimental treatments; manure was applied at a rate of 10,000 kg ha⁻¹ yr⁻¹ on an oven-dry weight basis, and corn without manure application was used as the control. The results indicated that long-term application of manure to sodic soil resulted in significant increases in soil porosity, water-holding capacity, and saturated hydraulic conductivity (K_s) and a decrease in bulk density in comparison to the control treatment. In addition, manure application significantly increased macro-aggregate formation and the mean weight diameter (MWD). Based on stepwise regression analysis, the dominant independent variable that affected aggregate stability was water-stable aggregates (WSAs) of 0.5–1 mm, and the dominant independent variable that affected both capillary porosity (ƒ_c) and non-capillary porosity (ƒ_n) was WSAs of 0.25–0.5 mm. MWD, ƒ_n and especially soil organic matter (SOM) were the dominant attributes that affected K_s. It was concluded that improved soil physical properties are related to soil aggregation, resulting mainly from macro-aggregate formation, particularly WSAs of 0.25–0.5 and 0.5–1 mm. This is due to binding-agent production and increased SOM from annual manure application.

28744. 题目: Optimization of membrane modification using SiO₂ for robust anti-fouling performance with calcium-humic acid feed in membrane distillation
文章编号: N18121907
期刊: Environmental Research
作者: Aftab Ahmad Khan, Imtiaz Afzal Khan, Muhammad Irfan Siyal, Chang-Kyu Lee, Jong-Oh Kim
更新时间: 2018-12-19
摘要: The goal of this study was to prepare a robust anti-wetting and anti-fouling polyethersulfone (PES) membrane for the rejection of a highly saline (NaCl and CaCl₂∙2H₂O) feed solution containing humic acid (HA) in direct contact membrane distillation (DCMD). Response surface methodology (RSM) was used to determine the optimum formulation of the used materials. The variable factors selected were polydimethyl siloxane (PDMS) and silica (SiO₂); liquid entry pressure (LEP) and contact angle (CA) were selected as responses. Scanning electron microscopy (SEM) analysis confirmed the SiO₂ deposition and Fourier-transform infrared spectroscopy (FTIR) test evidenced the new functional groups i.e., Si–OH, siloxane, and C–F bond vibrations at 3446, 1099 cm⁻¹, and 1150–1240 cm⁻¹ respectively on the membrane surface. The average roughness (Ra) was increased four times for the coated membranes (0.202–0.242 µm) as compared to that for pristine PES membrane (0.053 µm). The optimum PES-13 membrane exhibited consistent flux of 12 LMH and salt rejection (>99%) with anti-fouling characteristic in DCMD using the feed solution of 3.5 wt% NaCl + 10 mM CaCl₂∙2H₂O + 10 mg L⁻¹ HA. The PES-13 membrane may therefore be a key membrane for application in DCMD against CaCl₂∙2H₂O-containing salty solutions with HA.

28745. 题目: The effects of ecological construction and topography on soil organic carbon and total nitrogen in the Loess Plateau of China
文章编号: N18121906
期刊: Environmental Earth Sciences
作者: Peng Shi, Jinxiao Duan, Yan Zhang, Peng Li, Xiukang Wang, Zhanbin Li, Lie Xiao, Guoce Xu, Kexin Lu, Shengdong Cheng, Zongping Ren, Yi Zhang, Wengang Yang
更新时间: 2018-12-19
摘要: The construction of terraces and vegetation restoration in the hillslope are major soil and water conservation measures on the Chinese Loess Plateau and contributed to the distribution patterns of soil organic carbon (SOC) and soil total nitrogen (STN). Topography influences soil erosion and changes SOC and STN contents. However, little information is available regarding the effects of ecological construction and topography on SOC and STN. A study was undertaken in the Loess Plateau, to evaluate the effects of land use conversion and topographic factors on the topsoil SOC and STN content at three hillslope positions (upper, middle, and foot slopes) under four land uses types: artificial forest, grassland, terraced fields, and sloping cropland. The results showed that land use conversion from sloping cropland to artificial forest and grassland improved the SOC and STN content. Slope position was an important topographic factor governing the SOC and STN distribution at the slope scale in artificial forest, grassland, and sloping cropland, with the foot slope having the highest SOC and STN content, followed by the upper slope, while the middle slope had the lowest values. SOC and STN showed positive correlation with Caesium-137 (¹³⁷Cs) content. Land use types, slope position, and soil erosion had significant relationships with SON and STN. The results suggested that vegetation restoration of sloping cropland will contribute to soil carbon (C) and nitrogen (N) sequestration in the loess hilly region. The quantitative estimation of land use change and topography effects on SOC and STN could improve the accuracy of SOC and STN predictions in the region with a complex topography.

28746. 题目: Composition and cycling of dissolved organic matter from tropicalpeatlands of coastal Sarawak, Borneo, revealed by fluorescencespectroscopy and PARAFAC analysis
文章编号: N18121905
期刊: Biogeosciences
作者: Yongli Zhou, Patrick Martin, and Moritz Müller
更新时间: 2018-12-19
摘要: Southeast Asian peatlands supply ~10% of the global flux of dissolved organic carbon (DOC) from land to the ocean, but the biogeochemical cycling of this peat-derived DOC in coastal environments is still poorly understood. Here, we use fluorescence spectroscopy and parallel factor (PARAFAC) analysis to distinguish different fractions of dissolved organic matter (DOM) in peat-draining rivers, estuaries, and coastal waters of Sarawak, Borneo. The terrigenous fractions showed high concentrations at freshwater stations within the rivers, and conservative mixing with seawater across the estuaries. The autochthonous DOM fraction, in contrast, showed low concentrations throughout our study area at all salinities. The DOM pool was also characterized by a high degree of humification in all rivers and estuaries up to salinity 25. These results indicate a predominantly terrestrial origin of the riverine DOM pool. Only at salinities >25 did we observe an increase in the proportion of autochthonous relative to terrestrial DOM. Natural sunlight exposure experiments with river water and seawater showed high photolability of the terrigenous DOM fractions, suggesting that photodegradation may account for the observed changes in DOM composition in coastal waters. Nevertheless, we estimate based on our fluorescence data that at least 20%–25% of the DOC at even our most marine stations (salinity>31) was terrestrial in origin, indicating that peatlands likely play an important role in the carbon biogeochemistry of Southeast Asian shelf seas.

28747. 题目: Influence of water hydrogen on the hydrogen stable isotope ratio of methane at low versus high temperatures of methanogenesis
文章编号: N18121904
期刊: Organic Geochemistry
作者: Lin Wei, Zhiye Gao, Maria Mastalerz, Arndt Schimmelmann, Ling Gao, Xin Wang, Xiaoxue Liu, Ye Wang, Zhen Qiu
更新时间: 2018-12-19
摘要: Our laboratory experiments simulated hydrocarbon gas generation from source rocks by using low-temperature (≤200 °C) and long-term (1 month and 5 years) heating of pre-evacuated and sterilized immature shales and coals (vitrinite reflectance (VR) values of 0.21–0.47%Ro). Source rock powders and chips were sealed in gold and Pyrex^® glass tubes in the presence of waters with variable hydrogen isotopic compositions (i.e., δ²H_water values of –137‰ and +1246‰) to assess the influence of water-derived hydrogen on generated gaseous hydrocarbons. In addition, hydrous pyrolysis (HP) experiments using pre-extracted shales at 330 °C and H-isotopically distinct waters were performed for comparison. The isotopic transfer of water-hydrogen to hydrocarbons generated at both low and high temperatures was quantified. Isotopic mass-balances indicate that the methane to butane (C_CH4–C_C4H10) hydrocarbon gases from high-temperature HP experiments received an average of 53% of their hydrogen from water, whereas at low-temperatures the hydrogen transfer from water to methane ranged only from ∼1% to ∼13% of organic hydrogen.A possible explanation for differences in the extent of hydrogen transfer is that during lower-temperature hydrocarbon gas generation carbon-carbon bond breaking occurs close to the interface between minerals and organic matter, where hydrophobic organic microdomains limit the access of water. This would explain why methane generated at low temperatures mostly inherits its hydrogen from preexisting organic hydrogen and not from water, in contrast to methane generated at higher temperatures. At higher temperatures, the physico-chemical properties of water are altered compared to those at lower temperatures. Experiments at 330 °C enhance water solubility in organic phases and facilitate stronger isotopic interactions between water and organic hydrogen. Therefore, by comparing the results obtained at low-temperature and high-temperature conditions, our laboratory experiments offer insights into the mechanisms controlling the contribution of water hydrogen to hydrocarbon gas generation in sedimentary basins.

28748. 题目: Shift of millet rhizosphere bacterial community during the maturation of parent soil revealed by 16S rDNA high-throughput sequencing
文章编号: N18121903
期刊: Applied Soil Ecology
作者: Lixia Xu, Yansha Han, Min Yi, Huilan Yi, Erhu Guo, Aiying Zhang
更新时间: 2018-12-19
摘要: Microorganisms, particularly bacteria, are important components of mature soil capable of high crop yields. However, changes in the diversity and abundance of bacteria during the maturation of parent soil have not been thoroughly elucidated to date. In this study, we determined the diversity of the bacterial community in millet rhizospheres from mellow soil (MS), immature soil (IS), and a mixture of MS and IS (MS-IS mixture) using high-throughput Illumina sequencing. We also analysed soil chemical properties, microbial carbon, microbial nitrogen and enzyme activities, and we correlated them with bacterial taxa. In different rhizosphere soil samples, higher bacterial diversity was found in MS than in IS or the MS-IS mixture. The same trends were observed for soil organic carbon (SOC), available nitrogen (AN), available phosphorus (AP), carbon to nitrogen ratio (C/N), soil microbial carbon, soil microbial nitrogen and soil enzyme activities. Compared to IS, MS harboured a higher abundance of two phyla (Proteobacteria and Actinobacteria) but a lower abundance of five phyla (Chloroflexi, Acidobacteria, Bacteroidetes, Nitrospirae and Firmicutes) and a higher abundance of 22 genera but a lower abundance of 13 genera. A redundancy analysis indicated that the higher abundance of seven genera (Caenimonas, Gemmatimonas, Lysobacter, Ramlibacter, Devosia, Mycobacterium and Streptomyces) was correlated with higher levels of SOC, AN and C/N. Phosphatase, invertase and urease were correlated with higher levels of SOC, AN and C/N. These findings suggest that higher abundance of some specific bacteria accelerates soil maturation by increasing soil chemical properties and soil enzyme activities, thereby leading to higher crop yields.

28749. 题目: Addition of inorganic phosphorus to soil leads to desorption of organic compounds and thus to increased soil respiration
文章编号: N18121902
期刊: Soil Biology and Biochemistry
作者: Marie Spohn, Per-Marten Schleuss
更新时间: 2018-12-19
摘要: Addition of inorganic phosphorus (P) to soil has often been reported to cause increases in soil respiration, and this has been attributed to an alleviation of microbial P limitation. As an alternative explanation for this phenomenon, we tested the hypothesis that addition of inorganic P increases microbial respiration because added inorganic P exchanges with sorbed organic compounds in soil, and thus renders these organic compounds available for microbial decomposition. We conducted an experiment with ¹⁴C-labeled adenosine-monophosphate (AMP), and we determined the effect of inorganic P addition on dissolved organic carbon (DOC), dissolved DNA and soil respiration in the organic horizon and the A horizon of two beech forest soils with contrasting P stocks. We added inorganic P to the four soil horizons that contained trace amounts of ¹⁴C-AMP, and found that the emission of ¹⁴C-CO₂ increased significantly due to P addition in all soil horizons by a factor of 1.4 to 4.0. Respiration rates increased significantly in all soil horizons by a factor 1.1 to 1.9 due to inorganic P addition. One hour after the addition of inorganic P, DOC concentrations were increased by a factor of 1.6 to 3.5 compared to the controls, and they were still similarly high seven days after the addition of inorganic P. Furthermore, concentrations of dissolved, extracellular DNA were also significantly increased in response to P addition. The ¹⁴C experiment shows that the addition of inorganic P led to increased microbial metabolization of a compound that strongly sorbs to the soil solid phase and suggests that the source of the additionally respired C is dead organic matter that desorbs upon inorganic P addition. The extraction experiments show that addition of inorganic P led to elevated DOC concentrations. In conclusion, our study supports the hypothesis that the addition of inorganic P increases microbial respiration because added inorganic P exchanges with sorbed organic compounds in soil, and thus turns these compounds available for microbial decomposition. The results indicate that microbial respiration was increased in response to P addition not because microbial P limitation was alleviated but because microbial C limitation was alleviated by desorbed organic C.
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28750. 题目: Slope exposure and forest stand type as crucial factors determining the decomposition rate of herbaceous litter on a reclaimed spoil heap
文章编号: N18121901
期刊: CATENA
作者: Mateusz Rawlik, Marek Kasprowicz, Andrzej M. Jagodziński, Katarzyna Rawlik, Cezary Kaźmierowski
更新时间: 2018-12-19
摘要: Chemical composition of plant litter, properties of the soil, and climatic conditions are the major factors determining rate of organic matter decomposition. Although the process of decomposition in degraded areas plays a significant role in accumulation of soil organic carbon (SOC), this issue is poorly studied. SOC content is a crucial factor determining the success of land restoration. We measured rates of decomposition of the grass Calamagrostis epigejos, the dicotyledonous N-fixer Medicago sativa, the dicotyledonous non-N-fixing Cirsium arvense and cellulose paper as a standard carrier in forest stands on a reclaimed spoil heap of the opencast lignite mine in Bełchatów (central Poland). We considered the 10 cm topsoil particle size distribution and pH as factors that can affect the rate of organic matter decomposition and soil organic carbon content. Rate of litter decomposition was slowest for the grass (mean half decay time 2.6 years), while the N-fixing litter was not decomposed faster than the dicotyledonous non-N-fixing litter (mean half decay time of both species 0.9 years). Cellulose was decomposed most quickly (mean half decay time 0.8 years). Decomposition rate was faster under the canopy of Robinia pseudoacacia (deciduous N-fixing tree species, mean half decay time 0.9 years), whereas the rate of decomposition under Pinus sylvestris (coniferous canopy) was not slower than under Betula pendula (deciduous non-N-fixing tree species, mean half decay time under both species 1.5 years). Irrespective of litter type, decomposition was faster on the northern slope (mean half decay time 0.9 years) than on the southern slope (1.6 years). The plots where decomposition was faster (under R. pseudoacacia and on the northern slope) were characterized by higher SOC content (1.95% and 1.96%, respectively) than the plots under B. pendula (1.15%), P. sylvestris (1.29%), and those located on the southern slope (0.97%).
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28751. 题目: Temperature sensitivity of different soil carbon pools under biochar addition
文章编号: N18121821
期刊: Environmental Science and Pollution Research
作者: Xiaojie Wang, Guanhong Chen, Shuyan Wang, Leiyi Zhang, Renduo Zhang
更新时间: 2018-12-18
摘要: The objective of this study was to investigate the temperature sensitivity of labile and relatively recalcitrant forest soil carbon (C) pools amended with biochar during short-term incubation. Biochars were prepared using sugar cane residue under pyrolysis temperatures of 300 and 700 °C (i.e., BC300 and BC700), respectively. Coarse particulate organic matter and acid hydrolysis residue were separated from a forest soil and treated as the labile and recalcitrant C pools of the soil, respectively. Temperature sensitivity of the soil C pools was characterized using the Q₁₀ values (i.e., the proportional increase in respiration per 10 °C rise). The increased Q₁₀ values of treatments in the earlier stage were attributable to instantaneously increased aromatic C content. The following decreased Q₁₀ values were related to the consumption of labile C. However, the two types of biochars led to similar Q₁₀ values in the same C pools at the later stage of incubation, which was closely related to the nearly humic-like component content in the dissolved organic matter. The different temporal distributions of Q₁₀ values were attributable to changes of aromatic C content and continuous consumption of labile components.

28752. 题目: Soil organic matter composition as a factor affecting the accumulation of polycyclic aromatic hydrocarbons
文章编号: N18121820
期刊: Journal of Soils and Sediments
作者: Aleksandra Ukalska-Jaruga, Bożena Smreczak, Agnieszka Klimkowicz-Pawlas
更新时间: 2018-12-18
摘要: Purpose: The objective of this study was to evaluate the mutual relations between the soil organic matter (SOM) fractions: fulvic acids (FA), humic acids (HA), humins (HN), black carbon (BC) and the polycyclic aromatic hydrocarbons (PAH) accumulation level in agricultural soils influenced by historical and actual anthropopressure. The research allowed to indicate which fractions of SOM are the major sequestration sinks for PAHs after they are naturally introduced into the soil. Materials and methods: Soil samples were collected from the upper layer of agricultural soils (n = 41), and basic physicochemical properties (pH_KCl, total carbon, total nitrogen and clay content) were determined. The SOM was characterised by the total organic carbon content and humic substances, including HA, FA and HN, determined by an adapted method recommended by the International Humic Substances Society. The extracts of HA and FA were analysed for carbon content using a liquid CN analyser, while HN constituted the soil carbon in the residue after FA and HA extraction. The content of BC was analysed by dry combustion at 375 °C for 24 h (CTO375); the remaining carbon was determined via combustion in an elemental analyser. Results and discussion: In all soils, significant positive relations between PAH concentrations and TOC content (r = 0.73, p < 0.001) as well as HN (r = 0.71, p < 0.001) and BC (r = 0.86, p < 0.001) were noted. Relations among PAHs, HN and BC were statistically significant only in soils with TOC content ≥ 12 g kg⁻¹, while they were not observed for soils with TOC content < 12 g kg⁻¹. The links between HN and PAHs were stronger for low-molecular (two and three rings)-weight PAHs (r = 0.77, p < 0.05) than for high-molecular (≥ four rings) PAHs (r = 0.68, p < 0.05). Contrary to HN, the BC faction showed higher correlations with high-molecular-weight PAHs (r = 0.92, p < 0.001). FA and HA showed no significant relationship with hydrocarbons. Conclusions: Different SOM fractions might possess divergent binding capabilities and dissimilar binding strengths to PAHs. The different proportions and sorption capacities of BC and HN in relation to PAHs of different molecular weight are the result of varying structure, i.e. polar and non-polar functionalities in sorption domains and pore-size structures of these fractions. The high correlation between BC and higher-molecular PAHs may be a result of their co-emission, while the stronger relationships between HN and lower-molecular PAHs are directly related to their higher mobility and easier diffusion to stable SOM fractions.

28753. 题目: Abiotic reduction of Cr(VI) by humic acids derived from peat and lignite: kinetics and removal mechanism
文章编号: N18121819
期刊: Environmental Science and Pollution Research
作者: Suha T. Aldmour, Ian T. Burke, Andrew W. Bray, Daniel L. Baker, Andrew B. Ross, Fiona L. Gill, Giannantonio Cibin, Michael E. Ries, Douglas I. Stewart
更新时间: 2018-12-18
摘要: Hexavalent chromium contamination of groundwater is a worldwide problem caused by anthropogenic and natural processes. We report the rate of Cr(VI) removal by two humic acids (extracted from Miocene age lignite and younger peat soil) in aqueous suspensions across a pH range likely to be encountered in terrestrial environments. Cr(VI) was reduced to Cr(III) in a first-order reaction with respect Cr(VI) concentration, but exhibited a partial order (~ 0.5) with respect to [H+]. This reaction was more rapid with the peat humic acid, where Cr(VI) reduction was observed at all pH values investigated (3.7 ≤ pH ≤ 10.5). ¹³C NMR and pyrolysis GC-MS spectroscopy indicate that the reaction results in loss of substituted phenolic moieties and hydroxyl groups from the humic acids. X-ray absorption spectroscopy indicated that at all pH values the resulting Cr(III) was associated with the partially degraded humic acid in an inner-sphere adsorption complex. The reaction mechanism is likely to be controlled by ester formation between Cr(VI) and phenolic/hydroxyl moieties, as this initial step is rapid in acidic systems but far less favourable in alkaline conditions. Our findings highlight the potential of humic acid to reduce and remove Cr(VI) from solution in a range of environmental conditions.

28754. 题目: Differences in photochemistry between seawater and freshwater for two natural organic matter samples
文章编号: N18121818
期刊: Environmental Science: Processes Impacts
作者: Laura Stirchak, Kyle Moor, Kristopher McNeill, D James Donaldson
更新时间: 2018-12-18
摘要: We report changes in the excitation and resolved fluorescence spectra, inferred triplet formation and singlet oxygen formation abilities of two different Natural Organic Matter samples (NOM) in seawater vs freshwater or NaCl solution. In artificial seawater solution (but not in NaCl solution), the natural water-derived NOM samples Suwannee River Natural Organic Matter (SRNOM) and Nordic Reservoir Natural Organic Matter (NRNOM) display large enhancements in fluorescence intensity. Nearly identical spectra are seen when seawater is replaced by solutions of Mg2+ at its seawater concentration, consistent with magnesium binding to ligand sites of the natural organic matter giving rise to different photophysics. Fluorescence anisotropy measurements show a decrease in anisotropy of SRNOM and NRNOM in seawater, also consistent with Mg2+ binding. Different effects of Mg2+ are seen when the different NOM samples are illuminated: NRNOM exhibits increased formation of its triplet state and also quenching of its triplet by oxygen, compared to its photochemistry in the absence of Mg2+, while SRNOM exhibits a reduction in triplet formation in the presence of Mg2+. These observations imply that the photochemistry of NOM in seawater may be very different from what is expected based on freshwater or NaCl solution measurements.

28755. 题目: Combined effects of dissolved organic matter, pH, ionic strength and halides on photodegradation of oxytetracycline in simulated estuarine waters
文章编号: N18121817
期刊: Environmental Science: Processes Impacts
作者: Yanan Zhang, Jianchen Zhao, Yangjian Zhou, Jiao Qu, Jingwen Chen, Chao Li, Weichao Qin, Yahui Zhao, Willie Peijnenburg
更新时间: 2018-12-18
摘要: Estuarine waters of variable composition are sinks of many micropollutants. The varying water properties can impact the photodegradation of organic pollutants. In this study, the combined effects of dissolved organic matter (DOM), pH, ionic strength, and halides on the photodegradation of the model organic pollutant oxytetracycline (OTC) were investigated. Suwannee River natural organic matter (SRNOM) was used as a representative of DOM. Results showed that the observed photolysis rate constant (kobs) of OTC increased rapidly upon increase of pH. SRNOM induced a 11.0 ~ 17.9% decrease of the kobs for OTC. In the presence of SRNOM, the ionic strength and specific halide effects promote OTC photodegradation with a 39.2 ~ 84.2% and 7.1 ~ 28.8% increase of the kobs, respectively. The effects of SRNOM, ionic strength and halides on OTC photodegradation are pH-dependent. Direct photolysis half-lives (t1/2) of OTC were estimated in view of the more important role of direct photolysis compared to indirect photolysis. The estimated t1/2 values decreased from 187.4 ~ 206.6 d to 34.4 ~ 36.6 d as the pH increases in the Yellow River estuarine region. The results of this research demonstrate that the photodegradation rate of OTC increases rapidly in the gradient from river water to marine water in estuarine regions.

28756. 题目: A review on the interactions between engineered nanoparticles with extracellular and intracellular polymeric substances from wastewater treatment aggregates
文章编号: N18121816
期刊: Chemosphere
作者: Xiaoliu Huangfu, Yanghui Xu, Caihong Liu, Qiang He, Jun Ma, Chengxue Ma, Ruixing Huang
更新时间: 2018-12-18
摘要: Engineered nanoparticles (ENPs) will inevitably enter wastewater treatment plants (WWTPs) due to their widespread application; thus, it is necessary to study the migration and transformation of nanoparticles in sewage treatment systems. Extracellular polymeric substances (EPSs) such as polysaccharides, proteins, nucleic acids, humic acids and other polymers are polymers released by microorganisms under certain conditions. Intracellular polymeric substances (IPSs) are microbial substances contained in the body with compositions similar to those of extracellular polymers. In this review, we summarize the characteristics of EPSs and IPSs from sewage-collecting microbial aggregates containing pure bacteria, activated sludge, granular sludge and biofilms. We also further investigate the dissolution, adsorption, aggregation, deposition, oxidation and other chemical transformation processes of nanoparticles, such as metals, metal oxides, and nonmetallic oxides. In particular, the review deeply analyzes the migration and transformation mechanisms of nanoparticles in EPS and IPS matrices, including physical, chemical, biological interactions mechanisms. Moreover, various factors, such as ionic strength, ionic valence, pH, light, oxidation-reduction potential and dissolved oxygen, influencing the interaction mechanisms are discussed. In recent years, studies on the interactions between EPSs/IPSs and nanoparticles have gradually increased, but the mechanisms of these interactions are seldom explored. Therefore, developing a systematic understanding of the migration and transformation mechanisms of ENPs is significant.
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28757. 题目: The isotope effect of nitrate assimilation in the Antarctic Zone: Improved estimates and paleoceanographic implications
文章编号: N18121815
期刊: Geochimica et Cosmochimica Acta
作者: François Fripiat, Alfredo Martínez-García, Sarah E. Fawcett, Preston C. Kemeny, Anja S. Studer, Sandi M. Smart, Florian Rubach, Sergey Oleynik, Daniel M. Sigman, Gerald H. Haug
更新时间: 2018-12-18
摘要: Both the nitrogen (N) isotopic composition (δ¹⁵N) of the nitrate source and the magnitude of isotope discrimination associated with nitrate assimilation are required to estimate the degree of past nitrate consumption from the δ¹⁵N of organic matter in Southern Ocean sediments (e.g., preserved within diatom microfossils). It has been suggested that the amplitude of isotope discrimination (i.e. the isotope effect) correlates with mixed layer depth, driven by a physiological response of phytoplankton to light availability, which introduces complexity to the interpretation of sedimentary records. However, most of the isotope effect estimates that underpin this hypothesis derive from acid-preserved water samples, from which nitrite would have been volatilized and lost during storage. Nitrite δ¹⁵N in Antarctic Zone surface waters is extremely low (-61 ± 20‰), consistent with the expression of an equilibrium isotope effect associated with nitrate–nitrite interconversion. Its loss from the combined nitrate+nitrite pool would act to raise the δ¹⁵N of nitrate, potentially yielding overestimation of the isotope effect. Here, we revisit the nitrate assimilation isotope effect in the Antarctic Zone with measurements of the δ¹⁵N and concentration of nitrate with and without nitrite, using frozen sea water samples from 5 different cruises that collectively cover all sectors of the Southern Ocean. The N isotope effect estimated using nitrate+nitrite δ¹⁵N is relatively constant (5.5 ± 0.6‰) across the Antarctic Zone, shows no relationship with mixed layer depth, and is in agreement with sediment trap δ¹⁵N measurements. Estimates of the N isotope effect derived from nitrate-only δ¹⁵N are higher and more variable (7.9 ± 1.5‰), consistent with an artifact from nitrate-nitrite isotope exchange. In the case of the Southern Ocean, we conclude that the δ¹⁵N of nitrate+nitrite better reflects the isotope effect of nitrate assimilation. The stability of this isotope effect across the Antarctic Zone simplifies the effort to reconstruct past degree of nitrate consumption.

28758. 题目: Circulation patterns in the Late Pennsylvanian North American Midcontinent Sea inferred from spatial gradients in sediment chemistry and mineralogy
文章编号: N18121814
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Adam C.E. Turner, Thomas J. Algeo, Yongbo Peng, Achim D. Herrmann
更新时间: 2018-12-18
摘要: The North American Midcontinent Sea (NAMS) reached its maximum extent during glacio-eustatic highstands of the Late Paleozoic Ice Age, during which organic-rich “core shales” accumulated under a stratified water column with anoxic deep waters. The core shales of cyclothems are composed of a lower organic-rich laminated black shale and an upper bioturbated gray shale. The present study investigates circulation patterns within the NAMS by examining secular variations and spatial gradients in the concentrations and ratios of major elements, trace elements, and organic carbon, as well as carbon and nitrogen isotopes, within one cyclothemic core shale: the Heebner Shale. The Heebner Shale represents the core shale member of the Upper Pennsylvanian (lowermost Gzhelian; Virgilian) Oread Limestone Formation in Kansas and Iowa, and it is correlative with the Teutopolis Shale of the Mattoon Formation in Illinois. The Heebner was sampled at high stratigraphic resolution at five sites on the northern Midcontinent Shelf and two sites in the Illinois Basin. Clay and silt fraction proxies show influences from multiple distinct terrestrial sources. The paleosalinity proxy Sr/Ba in combination with spatial patterns of clay and silt proxies implies large-scale counterclockwise (cyclonic) rotation of the NAMS watermass, which was possibly driven by the hydrodynamics of upwelling on the southern Midcontinent Shelf margin and/or riverine discharge into the eastern NAMS. Spatial patterns of δ¹³C and δ¹⁵N are consistent with regionally variable productivity and redox conditions. Differences in the magnitude of a positive δ¹⁵N excursion among the study sites record spatially variable water-column denitrification rates. Enrichment of trace metals on the northern Midcontinent Shelf was a product of intensified water-column recycling within an estuarine saltwater wedge. Trace-metal enrichments and Fe/Al ratios are consistent with moderate watermass restriction throughout the NAMS. The results of the present study permit major refinement of the existing superestuarine circulation model for the NAMS [Algeo, T.J., et al., 2008, Modern and ancient epeiric seas and the super-estuarine circulation model of marine anoxia. In: B. Pratt and C. Holmden (eds.), Dynamics of Epeiric Seas, Geol. Assoc. Canada Spec. Publ. 48, pp. 7–38].

28759. 题目: Dose-dependence of growth and ecophysiological responses of plants to biochar
文章编号: N18121813
期刊: Science of The Total Environment
作者: Nigel V. Gale, Sean C. Thomas
更新时间: 2018-12-18
摘要: Charcoal is a ubiquitous legacy of wildfire in terrestrial systems that often contribute to rapid revegetation following disturbance; the use of charcoal soil amendments, or “biochars”, to promote plant growth has received recent research attention and increasing applied use. Despite its widespread use, well-resolved quantitative estimates of dose-response relationships for biochar effects on plant growth are nonexistent, and studies of biochar dosage effects on plant ecophysiology are minimal. We investigated the effects of biochar dosage on plant growth and ecophysiology in a glasshouse experiment involving two common early-successional plants, Abutilon theophrasti and Trifolium repens. Plants were grown in disturbed temperate soils with increasing dosages of wood biochars: 0, 2, 4, 6, 8, 10, 20, 30, 40, 50 t/ha. We measured leaf-level gas-exchange traits (A_max, g_s, WUE), chlorophyll concentration, and leaf area growth throughout the experiment. At the end of the experiment, we measured biomass, foliar nutrition, and soil properties (pH, EC, C and N). Responses of biomass and physiological traits were highly dose-dependent, followed primarily unimodal forms, and differed in some traits between species. Increases in the uptake of K, P, and Mg, were responsible for accelerated growth. Biochars also generally increased the concentration of micronutrients, especially Boron. As a result, nutrient stoichiometry shifted substantially: in A. theophrasti, biochars increased C:N, P:N, and K:N ratios, suggesting nitrogen dilution or induced deficiency at higher dosages. This work supports the general hypothesis that ecophysiological responses to biochar are dose-dependent and driven by changes in nutrient availability. Additional work is necessary to understand the broader ecological impacts of heterogeneity in soil pyrogenic C levels to succession and ecosystem function.
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28760. 题目: Sorption, degradation and bioavailability of oxyfluorfen in biochar-amended soils
文章编号: N18121812
期刊: Science of The Total Environment
作者: Chi Wu, Xingang Liu, Xiaohu Wu, Fengshou Dong, Jun Xu, Yongquan Zheng
更新时间: 2018-12-18
摘要: To investigate the effects of biochar amendment on the environmental fate of oxyfluorfen in soils, we evaluated the sorption, degradation and bioavailability of oxyfluorfen in various amended soils. The results showed that different biochars, i.e., derived from peanuts (BCP), chestnuts (BCC), bamboo (BCB), maize straw (BCM), or rice hull (BCR), exhibited different sorption capacities for oxyfluorfen in following the order: BCR > BCB > BCM > BCC > BCP. The sorption constant (K_f value) of the three soils (loamy clay, sandy loam, and clay loam) ranged from 62 to 116 (μg/g)/(mg/L)ⁿ and increased by 2.0- to 3.2-fold after introduction of 2% BCR. Furthermore, oxyfluorfen degraded faster in BCR-amended soil than in unamended soil, i.e., degradation increased by 1.0- to 1.4-fold with addition of 2% BCR. Introduction of BCR also decreased the oxyfluorfen uptake by soybean plants by 18–63%, and the capacity of soybeans to absorb oxyfluorfen decreased over time. Amendment with 6 months-aged BCR soil increased the uptake of oxyfluorfen by soybean plants by 2.3-fold compared with freshly prepared BCR soil. After the aging process, the observed increase in oxyfluorfen bioavailability was attributed to the reduced adsorption capacity of aged biochar. Nevertheless, BCR was effective for sequestrating oxyfluorfen as demonstrated by the fact that the adsorption capacity of biochar-amended soil after six months of aging was still 1.5- to 2.5-fold greater compared with that of unamended soil. These results demonstrate that amendment with BCR can be an effective method to modify soil and thereby decrease oxyfluorfen contamination in food crops.
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