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12661. 题目: Chemical modification of tannins from Acacia mearnsii to produce formaldehyde free flocculant
文章编号: N20080206
期刊: Science of the Total Environment
作者: Grazielle Machado, Cláudia A.B. dos Santos, Júlia Gomes, Douglas Faria, Fernando Santos, Rogerio Lourega
更新时间: 2020-08-02
摘要:

Flocculants and coagulants market is expected to grow in a Compound Annual Growth Rate (CAGR) of 5.9% between 2017 and 2022. The development of non-pollutant coagulants/flocculants aiming to replace conventional ones, usually toxic, has been extensively studied and one alternative is the possibility of obtaining tannin-based flocculants, compounds present in many plants and easily extracted. However, in order to use tannins as flocculants, their cationization is necessary, which is normally accomplished by Mannich reaction that requires formaldehyde addition, a toxic compound. In order to fill a gap in the literature, regarding coagulants/flocculants synthesis through green procedures, this paper aims to synthesize a flocculant from tannins with no use of formaldehyde, and optimize this synthesis through a Central Composite Rotatable Design (CCRD). The optimization variables were ammonium hydroxide (NH4OH) to tannin ratio, in the range of 1:1 to 5:1, and reaction time, in the range of 1 to 4 h The evaluation of the synthesized flocculant samples was accomplished by jar tests using a simulated effluent containing humic acid and the effect of reactant ratio and reaction time used in the synthesis was assessed. The flocculant synthesis methodology proposed on this study showed excellent results regarding turbidity and color removal, since 100% of turbidity removal and 89.9% of color removal were achieved. This novel tannin-based flocculant synthesis methodology is a promising technology to replace conventional coagulants/flocculants, once it is environmentally friendly.

12662. 题目: Disturbance mechanisms of lacustrine organic carbon burial: Case study of Cuopu Lake, Southwest China
文章编号: N20080205
期刊: Science of the Total Environment
作者: Quanliang Jiang, Shuaidong Li, Zhili Chen, Changchun Huang, Wenxin Wu, Hongbin Wan, Zhujun Hu, Cheng Han, Zhigang Zhang, Hao Yang, Tao Huang
更新时间: 2020-08-02
摘要:

Lakes are important organic carbon (OC) traps in the global carbon cycle. Recent studies have shown that the rate of OC burial in lacustrine sediments is influenced by factors such as climate change, land-use change, and eutrophication. In this study, we use multiproxy methods to reveal the mechanisms of lacustrine sediment OC burial in an alpine lake (Cuopu Lake), in southwest China. Combined with the dating from 210Pbex and n-alkanes distribution analysis using the Positive Matrix Factorization model, the sedimentary history was divided into five stages: religious activity (the 1840s–1880s), earthquake (the 1880s–1910s), garrison (the 1910s–1960s), transition (the 1960s–1990s), and ecotourism (the 1990s–2010s). During the earthquake stage, OC burial was dominated by terrestrial solids (>40%) and co-precipitated algae (>30%), with a rapid deposition rate (>4 mm a−1) and low OC concentration (<4 mg g−1). During the other stages, when the level of disturbance was relatively low, a change in nutrient conditions either promoted or inhibited plant growth, which influenced the type of buried OC. The contribution of OC derived from combustion sources varied from stage to stage. Severe anthropogenic disturbances have led to a significant increase in nutritional levels in the lake water, leading to an increase in the OC burial rate. Climate change, which leads to changes in temperature and rainfall, did not significantly influence OC burial, whereas nitrogen deposition (and associated ecological changes) was a significant determinant. When the general mechanism is dominant, the total nitrogen to inorganic phosphorus ratio is an effective indicator of OC burial due to its selective promotion of different plant types. In conclusion, our results suggest that lacustrine sediment OC burial is closely linked to physical and anthropogenic factors in Cuopu Lake, as well as similar montane lakes.

12663. 题目: Proton uptake behaviors of organic and inorganic matters in biochars prepared under different pyrolytic temperatures
文章编号: N20080204
期刊: Science of the Total Environment
作者: Xin Xiao, Zaiming Chen, Baoliang Chen
更新时间: 2020-08-02
摘要:

As an important part of biochar, surface functional group is the key interface between biochars and other phases, as well as an essential source of biochar's alkalinity and buffer abilities. However, due to the intricate organic and inorganic structures within biochars, the contribution from organic and inorganic matters to the functional groups remains unknown. In this work, the proton uptake curves were applied to study the functional groups of biochars via titration. Pine needle (PN) derived biochars with low inorganic content was selected for analyzing the organic functional groups variation under different pyrolysis temperatures. While rice straw (RS) derived biochars and the double-acid treated rice straw (DRS) derived biochars were compared for understanding the contributions from inorganic matters. The results indicate that the sorption behavior of proton onto biochars is surface adsorption, and the functional groups variation within PN biochars keeps consistent with reactions happened during pyrolysis. The inorganic matters within RS biochars contributed significantly to the buffering ability of biochars, and it is noteworthy to find that the contribution of inorganic matters of RS350, RS500, and RS700 on the total proton uptake stabilized at 67%, 84%, and 84% in the pH range of 2–8, respectively. As far as we know, this is the first report on separating the proton uptake ability of the organic and inorganic matters for biochars. The study on the interaction between biochars and proton will improve the estimation of the fate of ionizable pollutants, and the differentiation on the organic and inorganic matter contributions would benefit the understanding of biochar organic structures and inorganic structures.

12664. 题目: Chemical characteristics and brown carbon chromophores of atmospheric organic aerosols over the Yangtze River channel: a cruise campaign
文章编号: N20080203
期刊: Journal of Geophysical Research: Atmospheres
作者: Xinke Wang, Nathalie Hayeck, Martin Brüggemann, Letizia Abis, Matthieu Riva, Yiqun Lu, Buwei Wang, Jianmin Chen, Christian George, Lin Wang
更新时间: 2020-08-02
摘要:

Organic aerosols (OAs) have important influences on the climatic implications and health effects of atmospheric aerosols. Among the complex OA constituents, brown carbon (BrC) accounts for a substantial mass fraction and is of special interest because of its light‐absorbing properties. In this study, the chemical composition of atmospheric OAs over the middle‐lower Yangtze River (MLYR) channel, as well as the BrC, was investigated during a ship cruise campaign in winter 2015. In total, more than one thousand molecular formulas were determined using a combination of ultra‐high performance liquid chromatography (UHPLC), a diode array detector (DAD), and Orbitrap high‐resolution mass spectrometry (HRMS). Large numbers and enhanced signal abundances for known tracers as well as monocyclic and polycyclic aromatics indicate that biomass burning and fossil combustion are important sources of OAs over the MLYR channel. In addition, thirteen chromophores with strong light absorption, mostly representing established biomass burning tracers, were unambiguously determined by UHPLC/DAD/HRMS and contributed to 35‐37% of the total light absorption of OAs at 290 nm and 58‐70% at 350 nm. Sixty‐three previously identified biomass burning chromophores were also positively identified in the mass spectrometric analysis here but embedded in the humped signal during the spectroscopic analysis. These BrC chromophores exhibit high degrees of unsaturation, suggesting these compounds to be aromatic, nitro‐aromatic, and polycyclic aromatic type of species. Our results highlight the significant influence of biomass burning and fossil combustion on atmospheric OAs over the MLYR channel in the winter, strongly enhancing light‐absorbing properties and decreasing air quality.

12665. 题目: Molecular-Level Transformation of Dissolved Organic Matter during Oxidation by Ozone and Hydroxyl Radical
文章编号: N20080202
期刊: Environmental Science & Technology
作者: Christina K. Remucal, Elisabeth Salhi, Nicolas Walpen, Urs von Gunten
更新时间: 2020-08-02
摘要: Ozonation of drinking and wastewater relies on ozone (O3) and hydroxyl radical (•OH) as oxidants. Both oxidants react with dissolved organic matter (DOM) and alter its composition, but the selectivity of the two oxidants and mechanisms of reactivity with DOM moieties are largely unknown. The reactions of O3 and •OH with two DOM isolates were studied by varying specific ozone doses (0.1–1.3 mg-O3/mg-C) at pH 7. Additionally, conditions that favor O3 (i.e., addition of an •OH scavenger) or •OH (i.e., pH 11) were investigated. Ozonation decreases aromaticity, apparent molecular weight, and electron donating capacity (EDC) of DOM with large changes observed when O3 is the main oxidant (e.g., EDC decreases 63–77% for 1.3 mg-O3/mg-C). Both O3 and •OH react with highly aromatic, reduced formulas detected using high-resolution mass spectrometry (O:C = 0.48 ± 0.12; H:C = 1.06 ± 0.23), while •OH also oxidizes more saturated formulas (H:C = 1.64 ± 0.26). Established reactions between model compounds and O3 (e.g., addition of one to two oxygen atoms) or •OH (e.g., addition of one oxygen atom and decarboxylation) are observed and produce highly oxidized DOM (O:C > 1.0). This study provides molecular-level evidence for the selectivity of O3 as an oxidant within DOM. The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.0c03052. Details including the materials, scavenging calculations, known transformation products, bulk measurements, and Orbitrap MS analysis, as well as additional data found in Figures S1–S23 and Tables S1–S6 (PDF) This article has not yet been cited by other publications.

12666. 题目: Four-year continuous residual effects of biochar application to a sandy loam soil on crop yield and N2O and NO emissions under maize-wheat rotation
文章编号: N20080201
期刊: Agriculture, Ecosystems and Environment
作者: Xia Liao, Yuhui Niu, Deyan Liu, Zengming Chen, Tiehu He, Jiafa Luo, Stuart Lindsey, Weixin Ding
更新时间: 2020-08-02
摘要:

Biochar application has been reported to effectively mitigate N2O emissions and increase crop yield; however, its long-term residual effects remain largely unknown. A four-year field experiment was designed in the North China Plain (NCP) to evaluate the residual effect of biochar on N2O and NO emissions and crop yield under maize-wheat rotation. The study included five treatments: no N fertilization (Control), N fertilizer application (CN), and N fertilizer plus maize-straw biochar application at 3 (NB3), 6 (NB6) and 12 t ha−1 (NB12). Biochar amendment had no effect on maize yield during the four-year rotation, but increased maize grain N uptake by 12.9 − 14.1 % and fertilizer N use efficiency by 13.8 % in the fourth year. Meanwhile, NB12 treatment decreased wheat yield by 11.7 − 15.5 % in each year, except the second, while decreased average wheat yield. Biochar application significantly reduced N2O emissions by 31.5 − 42.4 % during the first maize season, and by 6.9 − 21.3 % in the third and fourth years primarily due to reduction in NH4+ availability for nitrification. Furthermore, this mitigation effect was positively related to soil moisture content and decreased with time after biochar application. Cumulative N2O emissions during the four wheat seasons were 0.25 − 0.85 kg N2O-N ha−1, and only decreased by 8.9 − 9.9 % under biochar amendment in the third and fourth years probably because low soil temperature suppressed N2O production. Biochar addition in the third and fourth years significantly reduced NO emissions by 9.0 − 20.1 % during the maize growing seasons and 10.5 − 19.1 % during the wheat growing seasons, especially under NB6 treatment. The average yield-scaled N2O and NO emissions were lowest in the NB6 treatment during the maize and wheat season. Overall, these findings suggest that 6 t ha−1 is the optimal biochar application rate for reducing N2O/NO emissions and yield-scaled N2O/NO emission under four-year maize-wheat rotation in the NCP.

12667. 题目: Organic biogeochemistry in the oxygen-deficient ocean: A review
文章编号: N20080113
期刊: Organic Geochemistry
作者: Stuart G. Wakeham
更新时间: 2020-08-01
摘要:

Oceanic oxygen-deficient zones (ODZs) encompass open ocean and coastal oxygen minimum zones and euxinic marine basins. A primary goal of this review is to demonstrate how new approaches involving lipidomics and genomics are informing how we think about ODZs. There are five parts to the review. First, a brief overview of early investigations of organic geochemistry in ODZs sets the stage for follow-on work. Second, linkages between organic biomarkers and microbial and geochemical processes are described for three key biogeochemical processes that are characteristic of ODZs: (i) oxidation of ammonium by archaea and anammox bacteria; (ii) redox cycles of metals and sulfur; (iii) the methane cycle. Third, three different approaches are presented that make possible comprehensive, integrated views of the biogeochemistry of the Black Sea, as a case study. Fourth, examples of organic biogeochemical results for ODZs in the modern ocean are projected back into the geological past to show that the same processes have been in play for eons. The final section summarizes how chemistry and biology have been combined in investigations in ODZs and concludes with some challenges for future research.

12668. 题目: Development of Fluorescence Surrogates to Predict the Ferrate(VI) Oxidation of Pharmaceuticals in Wastewater Effluents
文章编号: N20080112
期刊: Water Research
作者: Jianxin Nie, Shuwen Yan, Lushi Lian, Virender K. Sharma, Weihua Song
更新时间: 2020-08-01
摘要:

The removal of pharmaceuticals from wastewater effluents is an emerging concern for environmental scientists and engineers. Ferrate(VI) (FeVIO42−, FeVI) is a promising oxidant and the removal of pharmaceuticals from wastewater effluents has been investigated in this study. Firstly, FeVI oxidation of selected pharmaceuticals was examined by determining the apparent second-order rate constants (kapp) in buffer solutions as a function of pH (5.0-9.5). At pH 8.0, kapp of cimetidine, famotidine, nalidixic acid, ronidazole, dimetridazole, tinidazole, and caffeine are (1.6±0.2)×103, (7.8±0.3)×102, 2.6±0.4, 1.7±0.1, 0.9±0.3, 0.2±0.1, and < 0.1 M−1 s−1, respectively. However, kapp could not be directly employed to predict the removal of pharmaceuticals in the effluents due to the inhibited or enhanced effects of effluent organic matters (EfOM). Therefore, an alternative approach of spectroscopic surrogates was investigated since fluorophore was co-degraded with pharmaceuticals in the wastewater effluents. Particularly, the humic-like fluorescent peak correlated well with the pharmaceutical attenuation. The relationship of the reduction of fluorescence and the removal of pharmaceuticals could be described through a universal equation: y=A1xk1kw+A2xk2kw+A3. The practical utility of the fluorescence surrogate was validated by applying to field samples. Monitoring the changes of the fluorescence surrogate provides a promising, rapid, and inexpensive method for estimating the degradation of pharmaceuticals during FeVI treatment of wastewater effluents.

12669. 题目: Impacts induced by the combination of earthworms, residue and tillage on soil organic carbon dynamics using 13C labelling technique and X-ray computed tomography
文章编号: N20080111
期刊: Soil and Tillage Research
作者: Yafei Guo, Ruqin Fan, Neil McLaughlin, Yan Zhang, Xuewen Chen, Donghui Wu, Xiaoping Zhang, Aizhen Liang
更新时间: 2020-08-01
摘要:

Soil organic carbon (SOC) plays a key role in soil fertility and atmospheric CO2 concentration. Our previous work found that tillage induced changes in aggregate stability and pore structure were major factors contributing to the effect of tillage system on SOC. Effects of earthworms and residue on SOC vary among tillage practices, but we don't clearly know how earthworms, residue and tillage interact to affect SOC. A further study was carried out by adding 13C labeled maize residue and earthworms to undisturbed soil mesocosms from conventional tillage (CT) and no tillage (NT) plots and then incubating for 180 days at 18 °C. SOC, 13C, and soil aggregate were measured prior to and after incubation and pore structure was measured after incubation. Newly added residue had the same decomposition rate in CT and NT. Earthworms reduced the SOC content in CT, and the newly added residue reduced the SOC in NT. The earthworms increased average pore diameter of >500 μm, and decreased the pore number of 100−500 μm in NT. The newly added residue improved the SOC by increasing the MWD in CT. The earthworms could change the SOC by increasing the volume fraction in NT. This result is helpful in understanding how the earthworms and residue affect the SOC under different tillage practices and provides direction for developing strategies to increase soil fertility and mitigate emission of CO2 to the atmosphere.

12670. 题目: De-ashed biochar enhances nitrogen retention in manured soil and changes soil microbial dynamics
文章编号: N20080110
期刊: Geoderma
作者: Muhammed Mustapha Ibrahim, Kun Hu, Chenxiao Tong, Shihe Xing, Shuangquan Zou, Yanling Mao
更新时间: 2020-08-01
摘要:

Enhancing soil N retention is important to mitigate the negative environmental impacts caused by the loss of applied N fertilizers. Therefore, the use of modified biochar in the soil is a novel approach to enhance the sorption of N ions. Biochars derived from bamboo, cow, and pig manures were de-ashed and their properties were characterized. The de-ashed biochars were comparatively assessed with raw biochars on N-retention, and how this process is regulated by microbial activities, diversity, and abundance in a manured soil. De-ashing increased the intensity of biochar functional groups and their surface structure. In manured soils, the application of de-ashed bamboo biochar (PDBB) and de-ashed cow manure biochar (PDCB) led to an increase in NH4+-N retention of 34.5% and 6.8% relative to the amendment with raw biochars. Similarly, increased retention of 20.9%, 14.8%, and 19.1% of NO3-N, and an increase of 21.1%, 11.1% and 11.5% in total N were observed in PDBB, PDCB and de-ashed pig manure biochar (PDPB) respectively, compared to their raw biochars after 8 weeks. The modified surface properties of de-ashed biochars led to higher bacterial colonization, with an increase in the diversity and relative abundance of bacterial 16S rRNA genes, compared to the raw biochar treatments. This spike in microbial groups stimulated protease activities and hence, an increased abundance of N-cycling organisms. The increased microbial abundance was associated with a reduction in the release of urease by these microbial groups for the hydrolysis of urea, thereby ensuring soil N retention. De-ashing increased the intensity of biochar functional groups and improved its surface properties, which resulted in increased N-sorption, and immobilization by stimulating microbial activities and diversity in soil.

12671. 题目: Application of a new HMW framework derived ANN model for optimization of aquatic dissolved organic matter removal by coagulation
文章编号: N20080109
期刊: Chemosphere
作者: Guocheng Zhu, Nana Xiong, Chuang Wang, Zhongwu Li, Andrew S. Hursthouse
更新时间: 2020-08-01
摘要:

Removing dissolved organic matter (DOM) with polyaluminium chloride is one of the primary goals of drinking water treatment. In this study, a new HMW framework was proposed, which divided the factors affecting coagulation into three parts consisting of hydraulic condition (H), metal salt (M), and background water matrix (W). In this framework, H, M and W were assumed to be interacted with each other and combined to determine coagulation efficiency. We investigated the feasibility of the framework to determine the treatment efficiency through mathematical models. Results showed that non-linear artificial neural network (ANN) model was a better fit to the experimental data than the linear partial least squares (PLS) model: the ANN model could explain 76% of the total variations while the PLS could only explain 71%. The PLS did not follow the variations of observed values adequately. These experiments showed that the interaction between the HMW framework components were not simple linear relationships. The ANN model was able to optimize the composition of the HMW framework improving the efficiency of DOM removal through the components of HMW such as velocity gradient (G value), coagulant dosage, solution pH, and background water matrix. Overall, HMW framework is a new classification of factors affecting coagulation, leading to a better understanding of the coagulation process and sensitivity to influencing variables.

12672. 题目: Alkaline-thermal pretreatment of spectinomycin mycelial residues: Insights on anaerobic biodegradability and the fate of antibiotic resistance genes
文章编号: N20080108
期刊: Chemosphere
作者: Siqi Song, Mingye Jiang, Jie Yao, Huiling Liu, Xiaohu Dai, Gang Wang
更新时间: 2020-08-01
摘要:

Alkaline-thermal (AT) pretreatment is an economical and efficient pretreatment method to improve anaerobic biodegradability of biowaste. This study investigated the effect of AT pretreatment of spectinomycin mycelial residues (SMRs) for promoting anaerobic biodegradability along with the reduction of antibiotic resistance genes (ARGs), and thus obtained the optimal conditions of AT pretreatment. Biomethane potential (BMP) test was conducted to evaluate the anaerobic biodegradability of untreated and pretreated SMRs, and the fate of ARGs was tracked by quantitative polymerase chain reaction. Results showed that the modified Gompertz model fitted the results of BMP tests satisfactorily. Furthermore, AT pretreatment promoted BMP (B0) and reduced lag phase (λ) effectively. These were attributed to the solubilization of SMRs. The analyses of the changes in dissolved organic matter indicated that AT pretreatment could facilitate the solubilization of both biodegradable (e.g. protein) and recalcitrant matter (e.g. humic-like, analyzing by EEMs-PARAFAC), which had a significant corresponding positive (Person correlation, p < 0.01) and negative (Partial correlation, p < 0.01) influences on anaerobic biodegradability. However, the positive effects surpassed the negative effects, promoting the overall anaerobic biodegradability of SMRs. In addition, a considerable reduction of ARGs (by 0.62∼1.36 log units) was observed at pH ≥ 12, attributed to the hydrolysis of phosphodiester bond of DNA in strong alkaline solution. Considering both anaerobic biodegradability and ARGs, the optimal AT condition was concluded as pH 12, temperature 90 oC and time 120 min.

12673. 题目: Fe-doped biochar derived from waste sludge for degradation of rhodamine B via enhancing activation of peroxymonosulfate
文章编号: N20080107
期刊: Chemosphere
作者: Tianchan Zang, Hao Wang, Yinghao Liu, Li Dai, Shuang Zhou, Shiyun Ai
更新时间: 2020-08-01
摘要:

The disposal and management of waste sludge is a considerable challenge for environmental protection and resource utilization. Herein, sludge-based biochar material loaded with nano-Fe3O4 () was fabricated via hydrothermal carbonization process and employed as catalyst to activate peroxymonosulfate (PMS) for degrading organic dyes in wastewater. Benefiting from the proper iron content, porous structure and the good dispersibility of iron on the catalyst surface, the proposed catalyst not only exhibited excellent catalytic activity and durability in the activation of PMS to degrade Rhodamine B (RhB), which was almost completely removed in 10 min (50 mL 50 mg L−1), but also performed broad application prospects in pollutant degradation. More importantly, the free radical quenching test and electron spin-resonance spectroscopy (ESR) detection demonstrated that O2-, SO4-, OH and 1O2 were generated during the process of catalyst activation of PMS. Based on this, a possible reaction pathway for degrading RhB with the aid of was put forward. It is believed that this work offers a promising reuse method of converting the waste sludge to a high efficiency and low-cost nano magnetic catalyst to activate PMS for degrading refractory organic pollutants in aquatic surroundings.

12674. 题目: Electron donating capacities of DOM model compounds and their relationships with chlorine demand, byproduct formation, and other properties in chlorination
文章编号: N20080106
期刊: Chemosphere
作者: Rumeng Wang, Min Ji, Hongyan Zhai, Yinxiu Liang
更新时间: 2020-08-01
摘要:

Electron donating capacity (EDC) is a promising parameter to characterize the antioxidant properties and oxidant consumption of dissolved organic matter (DOM). To assess the potential of EDC in rapidly predicting the chlorine demand during chlorination, the EDC values were measured for ten DOM model compounds, including phenol, quinol, resorcinol, vanillin, tannic acid, l-phenylalanine, l-tryptophan, l-tyrosine, l-cysteine, and reduced glutathione. The EDC values varied according to the functional moieties present in the model compounds and the pH. At pH 7.0, the order of EDC values of the ten model compounds was (mol e/mol C): 0.843 (cysteine) > 0.538 (tyrosine) > 0.522 (tannic acid) > 0.516 (resorcinol) > 0.452 (phenol) ≈ 0.450 (tryptophan) > 0.257 (vanillin) > 0.226 (reduced glutathione) > 0.160 (quinol) > 0.00035 (phenylalanine). The EDC values correlated well (R2 = 0.93) with the 24 h Cl2 demand of the model compounds (except for phenol and tannic acid). By contrast, there was poor correlation between the EDC values and the 24 h formation potentials of chlorination byproducts (trihalomethanes, haloacetic acids and haloacetonitriles). The levels and variation of the EDC values were not significantly correlated with the total organic carbon, specific UV absorbance at 254 nm, or assimilable organic carbon of the model compounds.

12675. 题目: Effects of non‐native fish on lacustrine food web structure and mercury biomagnification along a dissolved organic carbon gradient
文章编号: N20080105
期刊: Environmental Toxicology and Chemistry
作者: Benjamin D. Barst, Karista Hudelson, Gretchen L. Lescord, Andrea Santa‐Rios, Niladri Basu, Anne Crémazy, Paul E. Drevnick
更新时间: 2020-08-01
摘要:

Though the introduction of non‐native fish species has been shown to alter trophic ecology in aquatic ecosystems, there has been limited research on how invasive species alter methylmercury (MeHg) biomagnification in lacustrine food webs. We sampled surface water and biota from eight lakes in Quebec, Canada, spanning a range of dissolved organic carbon (DOC) concentrations (2.9 to 8.4 mg/L); four lakes were inhabited by native brook trout (Salvelinus fontinalis ) and the remaining lakes contained brook trout and a non‐native fish, Allegheny pearl dace (Margariscus margarita ). Periphyton, zooplankton, macroinvertebrates, and fish were analyzed for: 1) stable carbon (δ13C) and nitrogen (δ15N) isotope ratios to delineate food webs, and 2) total Hg (THg) or MeHg. Compared to the brook trout from reference lakes, fish from invaded lakes had higher length‐standardized THg concentrations as well as a narrower dietary range and elevated trophic level, inferred from unadjusted δ13C and δ15N values, respectively. The rate of Hg biomagnification was similar across invaded and reference lakes, implying little effect of the invasive fish on the trophic transfer of MeHg. Despite differences in food web structure due to pearl dace invasion, DOC was the strongest predictor of brook trout THg levels for all lakes, suggesting that underlying environmental factors exerted a stronger influence on brook trout THg concentrations than the presence of a non‐native forage fish.

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12676. 题目: Estimation of carbon stocks in boreal cropland soils ‐ methodological considerations
文章编号: N20080104
期刊: European Journal of Soil Science
作者: Jaakko Heikkinen, Riikka Keskinen, Kristiina Regina, Henri Honkanen, Visa Nuutinen
更新时间: 2020-08-01
摘要: High expectations to harness agricultural soils as sinks for atmospheric carbon (C) necessitate methods for verifying changes in soil organic C (SOC) stocks and improving the accuracy of regional SOC stock estimates specific to various land‐use and management types. In this study we used a sample set included in the Finnish national soil monitoring network (n=125) to determine the SOC stock and its vertical distribution in Finnish agricultural mineral soils using fixed depth (FD) and equivalent soil mass (ESM) methods. Further, we explored the within‐field variation in SOC stock and minimum sample size in the context of SOC sequestration. Boreal agricultural mineral soils were found to be rich in SOC. The average SOC stock ranged between 8.4 and 9.8 kg m‐2 in the top 30 cm depending on cropping system and soil type. Cultivation of perennial crops tended to enrich the C in the soil surface in comparison to dominantly annual crops, which exhibited a less steep C gradient with depth. The commonly used van Bemmelen factor of 1.724 to convert results of loss on ignition to SOC was found to be appropriate as such for coarse textured Finnish agricultural soils. However, the results showed that in clay‐rich soils, it is critical to take into account the structural water bound in clay particles to avoid overestimation of the SOC content. The study also demonstrated that the minimum sample size required to detect the change of 0.1 kg C m‐2 in field level is typically several hundreds. Therefore empirical soil sampling is not at all cost‐effective enough for verifying the changes in SOC stocks in regard of C sequestration compensation to farmers. Thus, alternative verification methods, such as SOC modelling in combination with field level data collected e.g. using remote sensing should be developed further.

12677. 题目: Fouling mitigation and carbon recovery in nanofiltration processing of hydrothermal liquefaction aqueous waste stream
文章编号: N20080103
期刊: Journal of Membrane Science
作者: Xuesong Zhang, John Scott, Brajendra K. Sharma, Nandakishore Rajagopalan
更新时间: 2020-08-01
摘要:

A significant fraction of the embedded energy, carbon, and nutrients in biomass is lost to the aqueous phase during the hydrothermal liquefaction of biomass to bio-oil. The feasibility of concentrating the aqueous phase to recover and recycle the organics back to the hydrothermal liquefaction reactor using nanofiltration was investigated. The dissolved organic carbon content (∼ 1 wt%) of the hydrothermal liquefaction aqueous phase was mostly comprised of carboxylic acids, phenolics, and ketones. Several pretreatments, including pH adjustment, thermal treatment, ultrafiltration, and adsorption, were conducted prior to the nanofiltration process to mitigate membrane fouling. Adjustment of pH to 8 and higher was observed to improve the permeate flux. Minor amounts of humic-like organic materials were determined to be the major contributor to membrane fouling. Adsorption using coal was especially effective at selectively removing organic foulants and enabled the volume reduction of the hydrothermal liquefaction aqueous phase by a factor of ∼8. The dissolved organic carbon concentration in the retentate increased fourfold and an organic carbon mass recovery of ∼50% was achieved. The results show promise as a cost-effective way to the recovery of dissolved organic carbon in the hydrothermal liquefaction aqueous phase. Further integrated process development is needed to maximize valorization.

12678. 题目: Carbonate Radical Oxidation of Cylindrospermopsin (Cyanotoxin): Kinetic Studies and Mechanistic Consideration
文章编号: N20080102
期刊: Environmental Science & Technology
作者: Zhenyu Hao, Jianzhong Ma, Chenyong Miao, Yue Song, Lushi Lian, Shuwen Yan, Weihua Song
更新时间: 2020-08-01
摘要: Cylindrospermopsin (CYN) is one of the most important cyanobacterial toxins frequently found in surface waters. We reported the detailed kinetics and pathways for the reaction of CYN with carbonate radicals (CO3•–). The rate constants of neutral and deprotonated CYN with CO3•– were found to be (1.2 ± 0.7) × 107 M–1 s–1 and (3.0 ± 0.4) × 108 M–1 s–1, respectively. The transformation products for the oxidation of CYN by CO3•– were identified by high-resolution mass spectrometry, illustrating that the guanidine and bridged hydroxyl portions were the primary moieties attacked by CO3•–. Thus, three transformation pathways, including cleavage of the hydroxymethyluracil moiety, hydroxylation, and oxidation of the bridged hydroxyl group, are proposed for the CO3•– oxidation of CYN. Moreover, this study reported that dissolved organic matter (DOM) reduced the transformation rate of CYN by inhibiting the transformation of oxidation intermediates. Finally, the role of CO3•– in CYN degradation was estimated in both sunlit surface waters and advanced oxidation processes (AOPs), demonstrating that CO3•– played an important role in CYN attenuation under nonacidic environmentally relevant conditions. The kinetic parameters and product information obtained in this study will be of considerable interest for the application of AOPs and predicting the environmental fate of CYN.

12679. 题目: Long term combined fertilization and soil aggregate size on the denitrification and community of denitrifiers
文章编号: N20080101
期刊: Applied Soil Ecology
作者: Pei-Pei Li, Shui-Qing Zhang, Fang Li, Yu-Ting Zhang, Yan-Lai Han
更新时间: 2020-08-01
摘要:

Balanced fertilization strategies that combine the use of organic and inorganic fertilizers have been adopted to increase soil fertility and crop yield and to safeguard environment. However, knowledge on the influence of these fertilization strategies on microbe-mediated nitrogen cycling in the agricultural ecosystems remains limited. We analyzed the denitrifiers with nitrite reductase genes (nirK and nirS) in three soil aggregate classes (large macroaggregates, >2 mm; small macroaggregates, 0.25–2 mm; and microaggregates, <0.25 mm) in response to long-term application of inorganic fertilizers (NPK), NPK plus straw (NPKS), and NPK plus manure (NPKM) in the fluvo-aquic soil of North China Plain. Both fertilization and aggregate size had significant effects on the nirK and nirS gene abundances and soil potential denitrification activity (PDA). PDA in the combined fertilizer-treated soils (NPKS and NPKM treatments) was two times more than that in inorganic NPK-treated soil. PDA dramatically increased in small macroaggregates and microaggregates of NPKS treatment. The nirS gene abundance was significantly higher than that of the nirK gene abundance, and NPKS and NPKM treatments increased the nirS to nirK ratio in bulk soils and in microaggregates compared with NPK treatment and control. Correlation analysis and automatic linear modeling revealed a primary correlation between PDA and abundance of nirS-type denitrifiers. Soil properties, such as SOC, pH and TN, significantly affected the community structure of nirK- and nirS-type denitrifiers while only aggregate size significantly influenced the composition of nirK-type denitrifiers. Taken together, our results suggest that long-term combined fertilization increased the denitrification potential in small macroaggregate and microaggregate classes, and the increased gene abundance and the shift community structures of nirS- and nirK-type denitrifiers were potentially responsible for an increase in the promoted denitrification.

12680. 题目: Impact of humic acid on degradation of benzo(a)pyrene polluted Haplic Chernozem triggered by modified Fenton-like process
文章编号: N20073110
期刊: Environmental Research
作者: Mahmoud Mazarji, Tatiana Minkina, Svetlana Sushkova, Elena Antonenko, Saglara Mandzhieva, Tamara Dudnikova
更新时间: 2020-07-31
摘要:

In this study, the applicability of a modified Fenton reaction for remediation of polycyclic aromatic hydrocarbons (PAHs) was demonstrated in chernozem soil. The main aim was to investigate the impact of variation of humic acid (HA) on the modified Fenton capabilities to degrade of benzo(a)pyrene (BaP). Experimental was designed with two independent variables, including hydrogen peroxide (H2O2) and hematite (α-Fe2O3), to determine the most effective BaP treatment conditions with exploring natural and an extra added amount of HA. For modified Fenton reaction at Haplic Chernozem, the best BaP degradation conditions resulted in an overall degradation of 68 % with the following conditions: 0.95 M H2O2; 17.54 mg/g hematite; pH 7.8 without adjustment; 24 h; unsaturated (soil: water ratio 1:0.5). In the soil supplemented with 1% HA, Fenton-like reaction was found to perform better and resulted in 76 % BaP degradation with less amount of hematite dosage (16.71 mg). The fact that HA, a significant class of naturally occurring compounds in soil, supports the Fenton reaction has strong relevance in the field of enhancing PAHs degradation field to obtain a more economical route.

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