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23501. 题目: Adsorbable organic halogens formed during treatment of Cl−-containing wastewater by sulfate and hydroxyl radical-based advanced oxidation processes
文章编号: N20022309
期刊: Chemical Engineering Journal
作者: Yawei Xie, Ranyun Xu, Rui Liu, Hongyuan Liu, Jinping Tian, Lujun Chen
更新时间: 2020-02-23
摘要: The formation of adsorbable organic halogens (AOX) in two typical advanced oxidation processes (AOPs), OH-based (UV/H2O2) and SO4−-based (UV/potassium persulfate (PDS)) processes, was investigated during the treatment of Cl−-containing wastewater. Compared with the original AOX concentration (0.08 mg/L), a significant increase in the AOX concentration was observed in both AOPs under the condition that TOC concentration was minimized. Higher concentration of AOX was formed in the UV/PDS process than that in the UV/H2O2 process under all experimental conditions, although the former showed a better performance on TOC removal. An increase of effluent AOX concentration from 0.4 mg/L to 1.1 mg/L in the UV/H2O2 process and from 1.9 mg/L to 3.4 mg/L in the UV/PDS process was observed, respectively, when the Cl− concentration increased from 1800 mg/L to 10000 mg/L. This enhancement of high Cl−concentration on the AOX formation was attributed to the reactive halogen species generated in the AOP treatment. The term AOXMFP was created to determine the AOX formation potential of wastewater and AOPs system. The results showed that organic matters with a molecular weight (MW) between 1 k ∼ 100 k Da tend to form AOX more easily than those with a MW lower than 1 k Da and higher than 100 k Da. In addition, eight and fourteen kinds of formed organic halogens were identified in UV/H2O2 and UV/PDS treated wastewater, respectively. Five kinds of them have been proved to be toxic, which partially contributed to the increase of acute toxicity of effluent. The results of this work provides a new perspective to evaluate, in terms of eco-safety and efficiency, the application of AOPs to wastewater containing high concentration of Cl−.
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23502. 题目: Using wood flour waste to produce biochar as the support to enhance the visible-light photocatalytic performance of BiOBr for organic and inorganic contaminants removal
文章编号: N20022308
期刊: Chemosphere
作者: Aobo Geng, Lijie Xu, Lu Gan, Changtong Mei, Linjie Wang, Xingyu Fang, Meirun Li, Mingzhu Pan, Shuguang Han, Juqing Cui
更新时间: 2020-02-23
摘要: In the present study, industrial wood flour waste was selected for the first time as the precursor to produce biochar (WFB). The WFB was then used to prepare WFB/BiOBr visible-light photocatalysts, in which WFB acted as the carbon support to enhance the photocatalytic performance of BiOBr. Specifically, the impact of WFB pyrolysis temperature on the visible-light photo-removal performance of WFB/BiOBr was studied through degrading rhodamine B and reducing Cr(VI). The results indicated that when the pyrolysis temperature was 600 °C, the prepared WFB (600-WFB) had the highest graphitization degree, which afterwards significantly enhanced the visible-light photocatalysis performance of the BiOBr. Having higher graphitization degree, 600-WFB/BiOBr exhibited the highest photocatalytic capability. With a dosage of 0.5 g/L, the 600-WFB/BiOBr could completely remove to 20 mg/L of RhB and 5 mg/L of Cr(VI) within 90 min. Since wood flour is an abundantly existed industrial bioresource waste and easily pyrolyzed to prepare biochar, WFB is a promising alternative to replace traditional carbonaceous materials for the design of green and high-efficient visible-light photocatalysts for environmental remediation.
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23503. 题目: Arsenic adsorption by innovative iron/calcium in-situ-impregnated mesoporous activated carbons from low-temperature water and effects of the presence of humic acids
文章编号: N20022307
期刊: Chemosphere
作者: Xu-Jin Gong, Yu-Shu Li, Yu-Qi Dong, Wei-Guang Li
更新时间: 2020-02-23
摘要: Innovative iron/calcium in-situ-impregnated mesoporous activated carbons (GL100 and GL200) have been prepared by iron/calcium in-situ-impregnation and Multistage Depth-Activation. Arsenic adsorption kinetics, isotherms, thermodynamics, and re-usability were investigated. Effects of surface-absorbed (ST-HA) and dissolved states humic acid (DHA) on the arsenic adsorption were also determined. Results suggested in-situ iron/calcium impregnation caused the well-development of mesoporous structures during ranges of 2.0–5.0 nm in GL100 and 5.0–50 nm in GL200, respectively. The increase of iron/calcium ensured surface basicity and high ash contents on GL100/GL200, and As(III)/As(V) can be better adsorbed in neutral conditions with higher kinetics in comparison with regular mesoporous carbon XHIT. Maximum adsorption capacities of As(III)/As(V) by GL100 and GL200 were 2.985/3.385 mg/g and 2.516/2.807 mg/g, respectively. Arsenic desorption and carbon re-usability of GL100/200 was improved. As(III)(As (V)) adsorption capacities by GL100 and GL200 were 2.437(1.672) mg/g and 1.740(1.308) mg/g, respectively, after eight cycles. Arsenic adsorption capacities on GL100 were proved to be promoted with the presence of low-level of ST-HA or DHA, and be inhibited at a high-level. As(V) was bound more strongly than As(III) in the presence of ST-HA. As(III)/As(V) uptakes increased slightly and decrease gradually to 1.75/1.86 mg/g in the presence of DHA (0–10 mg DOC/L). Physisorption and chemisorption mechanisms dominant in arsenic adsorption on GL100 in presence of humic acid, forming inner-sphere complexation with metallic oxide, functional groups on carbon surface and humic acid structure, or ternary surface complexation via cationic metal ions as cation bridge.
23504. 题目: Soil organic carbon turnover following forest restoration in south China: Evidence from stable carbon isotopes
文章编号: N20022306
期刊: Forest Ecology and Management
作者: Xin Xiong, Huiling Zhang, Qi Deng, Dafeng Hui, Guowei Chu, Ze Meng, Guoyi Zhou, Deqiang Zhang
更新时间: 2020-02-23
摘要: As over half of the world’s tropical forests are reforested or afforested, understanding the resilience of carbon (C) pool in these forests is critical for global C balance. While most previous studies on the reforested lands have focused on C stock recovery, soil C turnover has largely been overlooked. We evaluated soil C turnover rate by calculating the isotopic enrichment factors of α (defined as the slope of the regression between the δ13C difference and ln-transferred C concentrations in mineral soil samples relative to the surface litter) and β (defined as the slope of the regression between δ13C and log-transferred C concentrations) along 0–30 cm soil profiles in a 400-year-old monsoon evergreen broad-leaved forest (MEBF), a 51-year-old mixed-native plantation (NP1), a 31-year-old mixed-native plantation (NP2), a 31-year-old Acacia mangium plantation (AP), a 31-year-old mixed-conifer plantation (CP), and a 31-year-old secondary forest with natural restoration (SF). Results showed that soil C stocks did not differ among the six forests. The estimated α values ranged from 1.0023 to 1.0086 and increased in the order of MEBF = NP1 < NP2 = AP = CP < SF. The estimated β values ranged from −19.70 to −5.22 but showed an opposite trend to α values. Additionally, changes of the α and β values among these forests were mainly regulated by soil water content and bulk density. Our findings demonstrate that forest restoration could enhance soil C stock equivalent to the undisturbed old-growth forests within a few decades, but the rate of soil C turnover in these restored forests were still higher.
23505. 题目: Interspecific plant competition increases soil labile organic carbon and nitrogen contents
文章编号: N20022305
期刊: Forest Ecology and Management
作者: Miaoying Wang, Jing Yang, Hailun Gao, Wenshi Xu, Mingqiu Dong, Guochun Shen, Juan Xu, Xingliang Xu, Jianming Xue, Cheng-Yuan Xu, Xiaoqi Zhou
更新时间: 2020-02-23
摘要: Plant competition can impose species-specific effects on the dynamics of soil carbon (C) and nitrogen (N) through rhizosphere processes and litter input. Therefore, it is crucial to quantify these effects in various terrestrial ecosystems for a better understanding of the mechanisms. Here, we collected subsoils containing low N from a subtropical forest and planted eight dominant tree species (two deciduous and six evergreens) in these soils in a greenhouse to explore the effects of interspecific plant competition on plant growth, soil C and N contents, and soil C and N mineralization rates after the plants had grown for 12 months. Soil labile organic C and N contents were represented by soil extractable organic C (EOC) and extractable organic N (EON) contents. We assessed the magnitude of the interspecific plant competition via the relative interaction intensity (RII) index, which was calculated from the biomass of seedlings in the mixed treatments compared with the single treatments. Our results showed that interspecific plant competition had species-specific effects on plant biomass and soil total C and N contents as well as soil C mineralization rates, whereas it tended to decrease soil N mineralization rates. However, interspecific plant competition significantly decreased plant C and N contents, and significantly increased soil EOC and EON contents with increasing RII. After classifying the communities into two functional types (i.e., deciduous–evergreen versus evergreen–evergreen), similar relationships were observed. These findings address the importance of quantifying interspecific plant competition on soil labile organic C and N contents, which is helpful for understanding soil C and N cycling in forest ecosystems.
23506. 题目: Waste timber pyrolysis in a medium-scale unit: Emission budgets and biochar quality
文章编号: N20022304
期刊: Science of The Total Environment
作者: Erlend Sørmo, Ludovica Silvani, Gorm Thune, Helmut Gerber, Hans Peter Schmidt, Andreas Botnen Smebye, Gerard Cornelissen
更新时间: 2020-02-23
摘要: Pyrolysis of organic waste or woody materials yields a stable carbonaceous product that can be mixed into soil and is often termed “biochar”. During pyrolysis carbon-containing gases are emitted, mainly volatile organic carbon species, carbon monoxide and aerosols. In modern pyrolysis units, gases are after-combusted, which reduces emissions substantially. However, emission data for medium- to large-scale pyrolysis units are scant, both regarding gases, aerosols, heavy metals and polycyclic aromatic hydrocarbons (PAH).Making biochar from lightly contaminated waste timber (WT) is a promising waste handling option as it results in the potential valorization of such residues into e.g. sorbents for contaminant stabilization. For this process to be environmentally sustainable, emissions during the process need to be low and the resulting biochar of sufficient quality. To investigate both issues, we pyrolyzed three batches of WT and one reference batch of clean wood/leaves in a representative medium-scale pyrolysis unit (Pyreg-500, 750 t/year) with after-combustion of the pyrolysis gases, and measured the gas, aerosol, metal and PAH emissions, as well as the characteristics and contamination levels of the resulting biochar, including contaminant leaching.Mean emission factors for the WT were (g/kg biochar); CO = 7 ± 2, non-methane volatile organic compounds (NMVOC) = 0.86 ± 0.14, CH4 = 0, aerosols (PM10) = 0.6 ± 0.3, total products of incomplete combustion (PIC) = 9 ± 3, PAH-16 = (2.0 ± 0.2) · 10−5, As (most abundant metal) = (2.3 ± 1.9) · 10−3 and NOX = 0.65 ± 0.10. There were no significant differences in emission factors between the pyrolysis of WT and the reference respectively, except for PM10, NMVOC, and PAH-16, which were significantly lower for WT than for the clean wood/leaves. The WT biochar did not satisfy premium or basic European Biochar Certificate criteria due to high levels of zinc and PAH. However, leachable metal contents were <0.1% of total contents. Still, use of the WT-biochar without further improvement or investigation would be limited to ex situ use, not improving soil fertility or in situ remediation.
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23507. 题目: Determination of the response characteristics of anaerobic ammonium oxidation bioreactor disturbed by temperature change with the spectral fingerprint
文章编号: N20022303
期刊: Science of The Total Environment
作者: Gui-Feng Li, Bao-Cheng Huang, Ya-Fei Cheng, Wen-Jie Ma, Shu-Ting Li, Bo Gong, Yan-Fang Guan, Nian-Si Fan, Ren-Cun Jin
更新时间: 2020-02-23
摘要: Anaerobic ammonium oxidation (anammox) bacteria are sensitive and susceptible to operating condition fluctuations that can lead to the instability of a bioreactor. Through multivariate spectral analysis, the dynamic changes of intracellular and extracellular metabolites of anammox sludge under the declined temperature stress were characterized. It was found that effluent fluorescence components were positively related to the bacterial activity, and the response of the protein-like substances to the temperature change was more sensitive than that of humic substances. Under the transient disturbance during temperature change from 35 to 15 °C, anammox system tended to considerably excrete extracellular polymeric substances to resist the low temperature inhibition. However, the long-term exposure of the sludge at 10 °C resulted in the considerably inhibition of sludge activity, granular disintegration and heterotrophic denitrification bacteria increase. The two-dimensional correlation analysis further revealed that the humic acid in extracellular polymeric substances was preferentially responded to the temperature change than protein. Anammox bacteria tended to increase the intracellular protein and electron transfer-related reactive substance excretion to counteract the low temperature inhibition. Herein, both the intra- and extra-cellular response characteristics of anammox sludge to temperature variation were successfully resolved via the combined spectra. This work provides a comprehensive understanding on the mechanism of anammox sludge to temperature variation and may be valuable for the development of bioreactor monitoring techniques.
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23508. 题目: Kinetics of pollutants removal in vertical and horizontal flow constructed wetlands in temperate climate
文章编号: N20022302
期刊: Science of The Total Environment
作者: Magdalena Gajewska, Katarzyna Skrzypiec, Krzysztof Jóźwiakowski, Zbigniew Mucha, Włodzimierz Wójcik, Agnieszka Karczmarczyk, Piotr Bugajski
更新时间: 2020-02-23
摘要: This paper reports a comparative study on kinetics of organic matter expressed as BOD5 and nitrogen removal in constructed wetlands operated in Poland. Analyzed data were collected at eight wetland systems, composed of subsurface flow beds: horizontal flow (HF) and vertical flow (VF), in different number and sequences. The analysis involved particularly mass removal rates (MRR) and first-order removal rate coefficients of BOD5 and total nitrogen (kA and kv for VF and HF filters, respectively, and k20 as a parameter averaged for a temperature of 20 °C). It was found that the higher the load of pollutants applied to the beds, the higher MRR values were obtained. The average k-rates in analyzed systems were mostly lower than those reported in the literature, especially in the case of total nitrogen. Its removal obtained in horizontal flow beds was kv = 0.002–0.042 d−1, while in vertical flow systems kA varied from 0.007 m d−1 to 0.0037 m d−1. According to data given by previous studies, first-order reaction rates for nitrogen removal varied in range from kv = 0.048 d−1 to kv = 0.19 d−1 and kA from 0.007 to 0.1 m d−1 in HF and VF beds, respectively. Regarding BOD5 shown in literature, removal rate kv for HF beds varied from 0.071 to 6.11 d−1, and kA for VF beds varied from 0.019 to 1.0 m d−1, while in this study lower k-rates were obtained: kv = 0.005–0.085 d−1 and kA = 0.015–0.130 m d−1. Relatively long monitoring period, for some of constructed wetland up to 16 years, resulted in good data set and enables creation of the graphs, which could be helpful in evaluation and designing of constructed wetlands for PE bigger than 50, in moderate climate conditions.
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23509. 题目: Hydro-climate and biogeochemical processes control watershed organic carbon inflows: Development of an in-stream organic carbon module coupled with a process-based hydrologic model
文章编号: N20022301
期刊: Science of The Total Environment
作者: Xinzhong Du, Danielle Loiselle, Daniel S. Alessi, Monireh Faramarzi
更新时间: 2020-02-23
摘要: Dissolved organic carbon (DOC) in surface waters directly influences the speciation, transport, and fate of heavy metals, as well as the partitioning of organic contaminants. However, the lack of process-based watershed-scale models for simulating carbon cycling and transport has limited the effective watershed management to control organic carbon fluxes to source waters and throughout the river systems. Here, a process-based in-stream organic carbon (OC) module was developed, coupled with the physically process-based Soil and Water Assessment Tool (SWAT), and linked with its existing soil carbon module to simulate dynamics of both particulate organic carbon (POC) and DOC. The advanced model simulates a large spectrum of OC processes from landscapes to stream networks throughout the watersheds. In-stream organic carbon processes related to POC and DOC as state variables are modeled in the water column, and the transformations between different carbon species and interactions between OC with algae are considered. The module's ability to simulate total organic carbon (TOC) loads was assessed, and the monthly and seasonal variations were captured over 14 years. Simulations for TOC loads suggested that spring snowmelt and summer rainfall runoff events are the main driving forces behind TOC export in the watershed. The parameter sensitivity analysis and dynamic reaction rate simulated in the streams suggested that TOC dynamics in the study area are controlled by both landscape and in-stream processes. The spatiotemporal analysis of the simulated TOC load showed that 55.8% of total terrestrial OC exports into the streams are removed due to in-stream POC settling and DOC mineralization, confirming the necessity of integrating terrestrial and aquatic OC processes for process understanding and for modelling and management of water quality at the watershed scale. The developed OC module is a potentially effective tool for simulating the OC cycle at the watershed scale and can be applied further to water treatment plans and watershed management.
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23510. 题目: Soil Amendments with Lignocellulosic Residues of Biorefinery Processes Affect Soil Organic Matter Accumulation and Microbial Growth
文章编号: N20022208
期刊: ACS Sustainable Chemistry & Engineering
作者: Davide Savy, Filip Mercl, Vincenza Cozzolino, Riccardo Spaccini, Silvana Cangemi, Alessandro Piccolo
更新时间: 2020-02-22
摘要: The development of soil microbiota and the chemical composition of soil organic matter (SOM) were studied in a 180 day incubation experiment upon addition of a characterized lignocellulosic biorefinery residue (BYP) at two different rates. The microbial growth was studied by PLFA analysis after 30, 60, and 180 days, while SOM molecular composition was assessed by thermochemolysis at the end of the trial. Soil amendments with BYP induced a well differentiated microbial community. However, the overall microbial development significantly decreased over the experimental time due to a lesser availability of decomposable C to microorganisms. The reduced C accessibility was related to the progressively higher SOM recalcitrance with increasing BYP rates and was attributed to selective accumulation into the stable SOM fraction of hydrophobic compounds which prevented further BYP mineralization by protecting BYP from microbial activity. Our findings indicate that amendments with lignin-rich residues from biorefinery processes may promote the stabilization of humified molecules in soils, thus leading to a net C accumulation in soils.
23511. 题目: Temporally-resolved mechanisms of deep-ocean particle flux and impact on the seafloor carbon cycle in the northeast Pacific
文章编号: N20022207
期刊: Deep Sea Research Part II: Topical Studies in Oceanography
作者: Christine L. Huffard, Colleen A. Durkin, Stephanie E. Wilson, Paul R. McGill, Rich Henthorn, Kenneth L. Smith
更新时间: 2020-02-22
摘要: High-temporal-resolution views of particle flux to the abyssal benthic boundary layer are provided for an eight-month period (October 2014–June 2015) at the long-term monitoring site Station M within the California Current ecosystem. Contributions of fecal pellets and aggregates to particulate organic carbon (POC) flux at 3900 m depth were estimated based on optical sediment trap (Sedimentation Event Sensor) images captured after 2 h collections. POC flux estimated from Sedimentation Event Sensor (SES) images explained variation in carbon consumption and the carbon budget balance (supply – demand) with finer resolution than POC flux measurements from bulk collections by a concurrently deployed conventional sediment trap. Indicators of particle transport by benthic boundary layer currents and active transport by zooplankton were evaluated by comparing SES-estimated POC flux to measured current speed and direction, hours since solar noon, and modeled lunar illumination at the surface. Influence of particles (fecal pellets and aggregates) on the carbon budget was evaluated by comparing particle-specific contributions to POC flux with sediment community oxygen consumption (SCOC) measured by the Benthic Rover at 4000 m depth. During the eight-month sampling period, salp fecal pellets delivered an estimated 45% of the total POC flux to the benthic boundary layer and were responsible for an estimated 74% of a temporary carbon surplus in May and June 2015. Salp fecal pellets also appeared to be the primary source of chlorophyll to the site. By contrast, most aggregates appeared to be lower-quality particles possibly sourced from lateral advection and local rebound of recently-settled detritus, which settled according to spring-neap tidal oscillations. Some aggregates may have been fresher, as suggested by non-linear relationships with SCOC and the carbon budget balance. Results suggest sinking particles packaged in surface waters and reaching abyssal depths in fresh condition (e.g. salp fecal pellets) had a greater influence on carbon consumption (e.g. SCOC) and the carbon budget balance than more refractory particles.
23512. 题目: Synergistic removal of cadmium and organic matter by a microalgae-endophyte symbiotic system (MESS): An approach to improve the application potential of plant-derived biosorbents
文章编号: N20022206
期刊: Environmental Pollution
作者: Mingming Li, Xiao Xiao, Shipei Wang, Xujing Zhang, Junjie Li, Spyros G. Pavlostathis, Xubiao Luo, Shenglian Luo, Guisheng Zeng
更新时间: 2020-02-22
摘要: Plant-derived materials as environmentally friendly biosorbents to remove heavy metals from wastewater have been extensively studied. However, the chemical oxygen demand (COD) increase caused by the plant-derived biosorbent has not been considered previously. In this study, water hyacinth was used as biosorbent to remove Cd(II) from wastewater. About 66% of Cd(II) was removed by the biosorbent with a maximum biosorption capacity (qmax) of 21.6 mg g−1. However, the COD of the filtrate increased from 0 to 292 mg L−1 during this process. Subsequently, endophytes, microalgae and the microalgae-endophyte symbiotic system (MESS) were assessed for the simultaneous Cd(II) and COD removal. Among these three systems, the MESS achieved the best performance. After 3 d of inoculation, the extent of total Cd(II) removal increased to 99.2% while COD decreased to 77 mg L−1. This study provides a new insight into the application of a plant-derived biosorbent in combination with microalgae and endophytes for the effective treatment of heavy metal-bearing wastewater.
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23513. 题目: Dynamics of residual phosphorus forms under different tillage systems in a Brazilian Oxisol
文章编号: N20022205
期刊: Geoderma
作者: Luiz Eduardo Zancanaro de Oliveira, Rafael de Souza Nunes, Djalma Martinhão Gomes de Sousa, Cícero Célio de Figueiredo
更新时间: 2020-02-22
摘要: Phosphorus (P) accumulation in soil, mainly from decades of agricultural use with frequent additions of phosphate fertilizers, results in a large reserve of this nutrient that can be exploited by farmers. However, the dynamics of soil P forms under the residual effect of phosphate fertilization is still little known. In an experiment located at Embrapa Cerrados, in Planaltina, DF, Brazil, corn or soybeans were grown during the summer for 17 years, receiving 35 kg of P ha−1 year−1. The same area was then cultivated with corn for 4 more years without the supply of this nutrient, in order to characterize the behavior of P fractions accumulated in the soil and identify those that contribute most to crop nutrition when phosphate fertilization is interrupted. Changes in total P (Pt), organic P (Po), inorganic P (Pi), and labile P extracted by the Bray-1, Mehlich-1 and Olsen methods (organic and inorganic) and organic carbon (C) were evaluated by means of samples obtained before and after cultivation without P fertilization in different soil layers subject to no-till (NT) or conventional tillage (CT), previously fertilized with reactive rock phosphate (RRP) or triple superphosphate (TSP) which were applied by broadcast spreading or band-applied to the planting row. The superficial layers were most responsible for crop nutrition in NT, especially in the mode of broadcast application, while in CT the relative contribution of each layer was less stratified. There was a drastic reduction in the stock of almost all P fractions, except for Po which showed an increase, notably in soil cultivated under CT (22% in the 0–10 cm layer), although the C content was reduced. This suggests that the little available inorganic fractions, partially replacing the labile fractions, were responsible for the supply of P to crops. This replacement was more effective in NT, since it could sustain greater P offtake by crops, despite the similar reductions in labile P fractions observed in both systems.
23514. 题目: Carbon nanotube supported sludge biochar as an efficient adsorbent for low concentrations of sulfamethoxazole removal
文章编号: N20022204
期刊: Science of The Total Environment
作者: Yongfei Ma, Lie Yang, Li Wu, Ping Li, Xuebin Qi, Liuyang He, Song Cui, Yongzhen Ding, Zulin Zhang
更新时间: 2020-02-22
摘要: A novel adsorbent of sludge biochar (SBC) and multi-walled carbon nanotube (CNT) composite was synthesized (CNT-SBC) to remove low concentrations of sulfamethoxazole (SMX) from water. The key factors of dose, contact time, pH and temperature were investigated. Higher dose of adsorbents provided more active sites for SMX adsorption. The effect of pH was due to the electrostatic interaction. Increasing the temperature was beneficial to SMX adsorption, which was a spontaneous endothermic process and the strength of the spontaneous increased with CNT supporting. As pseudo-second-order, Elovich, Langmuir and Freundlich models fitted the experimental data better, this suggested that both physisorption and chemisorption played vital roles during the adsorption process. In addition, liquid film diffusion was the main rate-limiting step of adsorption. Compared with SBC (5.43 × 103 μg g−1), CNT-SBC-1 (CNT:SBC = 1:2), CNT-SBC-2 (CNT:SBC = 1:4) and CNT-SBC-3 (CNT:SBC = 1:6) exhibited better adsorption performance with up to 2.35 × 104, 1.49 × 104 and 1.22 × 104 μg g−1 at 25 °C, respectively. The characterization analysis demonstrated that the stronger adsorption capacity of CNT-SBC was mainly attributed to the pore filling, functional groups complexation and π-π interaction. In summary, as an efficient and environment-friendly adsorbent, CNT-SBC has promising potential for low concentrations of SMX and other emerging contaminants removal from water.
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23515. 题目: Beef cattle production impacts soil organic carbon storage
文章编号: N20022203
期刊: Science of The Total Environment
作者: Chang Liang, J. Douglas MacDonald, Raymond L. Desjardins, Brian G. McConkey, Karen A. Beauchemin, Corey Flemming, Darrel Cerkowniak, Ana Blondel
更新时间: 2020-02-22
摘要: Grazing of natural rangeland and seeded pasture is an important feeding strategy for the Canadian beef cattle industry. As a consequence, beef cattle population has a direct influence on the proportion of land base maintained as perennial forage, which in turn changes soil organic carbon (SOC) stocks. We examined historical relationships between the net change in SOC resulting from perennial/annual crop conversion and beef cattle populations. We observed strong negative linear relationships, both regionally and nationally, between the population of beef cattle and the estimated change in SOC (negative sign indicating soil C sink) resulting from the conversion of annual crops and vice versa. These relationships indicate that as beef cattle population declines there is a corresponding loss of SOC resulting from a reduction in the relative proportion of perennial to annual crops on the landscape. The annual C loss resulting from land use conversion was roughly equivalent to 62% (±13%) of the combined enteric and manure annual emissions of CH4 and N2O [(1400 (±440) kg CO2 eq head−1 yr−1] resulting in net greenhouse gas emissions of 850 (±360) kg CO2 eq head−1 yr−1. These results highlight the importance of an integrated analysis that considers land use conversion and its impact on SOC when assessing the environmental footprint associated with beef cattle production.
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23516. 题目: A quantitative assessment of amino sugars in soil profiles
文章编号: N20022202
期刊: Soil Biology and Biochemistry
作者: Xiangyin Ni, Shu Liao, Siyi Tan, Dingyi Wang, Yan Peng, Kai Yue, Fuzhong Wu, Yusheng Yang
更新时间: 2020-02-22
摘要: Recent evidence suggests that a significant proportion of stable soil organic matter is derived from microbial necromass, which can be evaluated by measuring biomarker amino sugars. However, our understanding of the vertical distribution and control of amino sugars in soil profiles at the global scale is still limited. Here, we synthesized the concentrations of amino sugars relative to soil mass (mg/g soil) and to soil organic carbon (C) concentration (mg/g C) in various soil horizons (litter layer, O horizon soil and mineral soil at 0–20, 20–50, 50–100 and > 100 cm depths) from 131 forest, grassland and cropland sites. We found that the concentration of soil amino sugars declined with soil depth, ranging from 5.90 mg/g soil in O horizon soil and 1.56 mg/g soil at 0–20 cm depth to 0.24 mg/g soil at >100 cm depth. However, the proportion of amino sugars in soil organic C significantly increased from 18.1 mg/g C in O horizon soil to 61.9–83.3 mg/g C in mineral soil. The concentration of amino sugars was positively correlated with soil organic C and microbial biomass C concentrations. The proportion of amino sugars in soil organic C was significantly higher in microaggregates (<2 μm) and in soil with low carbon to nitrogen ratios. Microbial biomass carbon and soil pH had positive and negative effects, respectively, on the concentration of amino sugars in topsoil, and together explained 58.8% of the total variation in the concentration of amino sugars. These results suggest that soil biogeochemical properties are more important than climatic variables and latitude in determining the long-term persistence of microbial residues in soils.
23517. 题目: Carbon doped Fe3O4 peroxidase-like nanozyme for mitigating the membrane fouling by NOM at neutral pH
文章编号: N20022201
期刊: Water Research
作者: Hankun Yang, Wu Xue, Mengjie Liu, Kai Yu, Wenzheng Yu
更新时间: 2020-02-22
摘要: Oxidation is a widely used method in drinking water treatment to mitigate the membrane fouling caused by the natural organic matters (NOM) from the surface water during ultra-filtration (UF) and nano-filtration (NF) processes, and H2O2 is one of the common oxidants for it. However, the oxidation capability of H2O2 at neutral pH is lower, compared to the acidic and alkaline conditions. In order to improve the efficiency of NOM oxidation at neutral pH, a carbon-doped Fe3O4 peroxidase-like nanozyme (CFPN) was synthesized in this study and used as a high-performance catalyst for H2O2 to generate hydroxyl radical. The oxygen-containing groups on the carbon structure of CFPN can form an acidic microenvironment, allowing H2O2 to produce hydroxyl radical by catalysis in neutral conditions. The results of hydrophilicity analysis, zeta potential, high-performance liquid size exclusion chromatography (HPSEC), Fourier transform infrared spectrum (FTIR) and flux indicated that the hydroxyl radical can oxidize the hydrophobic matters of humic acid (HA) into hydrophilic matters by Fenton reaction or electrophilic addition reaction, which can mitigate the fouling of NF membranes. The results of the same test for the bovine serum albumin (BSA) indicated that the hydroxyl radical can mitigate the fouling of UF membranes by degrading the tertiary and secondary structures of BSA and partly oxidizing the side chain groups. In addition, two types of surface water samples were used to verify the above mechanism, and the results indicated that the hydroxyl radical treatment at neutral pH is a new viable and effective strategy to significantly mitigate the NOM fouling of UF and NF membranes.
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23518. 题目: Optical Properties of Soil Dissolved Organic Matter Are Related to Acidic Functions of Its Components as Revealed by Fractionation, Selective Deuteromethylation, and Ultrahigh Resolution Mass Spectrometry
文章编号: N20022113
期刊: Environmental Science & Technology
作者: Alexander Zherebker, Evgeny Shirshin, Anna Rubekina, Oleg Kharybin, Alexey Kononikhin, Natalia A. Kulikova, Kirill V. Zaitsev, Vitaliy A Roznyatovsky, Yuri K. Grishin, Irina V. Perminova, Evgeny N. Nikolaev
更新时间: 2020-02-21
摘要: The goal of this study was to establish a relationship between the optical properties of soil dissolved organic matter (DOM) and acidic functions carried out by its individual constituents. We obtained 12 fractions of DOM samples using sequential solid phase extraction on nonionic sorbent at steadily lowered pH values: 7, 5, 3, 2, which correspond to low bounds of pKa values of phenols, aliphatic, and aromatic carboxylic acids, and ketoacids. The structural studies were conducted with the use of NMR and selective deuteromethylation of isolated fractions coupled to ultrahigh resolution mass spectrometry. First, a gradual shift of molecular compositions was observed from reduced components to aromatic oxidized compounds isolated at pH 7 and 2, respectively. Changes in molecular compositions were accompanied by a red shift of fluorescence spectra. Further application of deuteromethylation enabled us to distinguish DOM constituents with different amounts of carboxylic groups. Moreover, identification of structural isomers in a single DOM sample was achieved. Statistical analysis revealed that red shift of fluorescence is facilitated by the increase of a contribution of aromatic poly(carboxylic acid)s with high conjugation lengths. Additionally, analysis of the labeled fractionated permafrost thaw DOM directly showed carboxyl-rich alicyclic molecules, while the same components from lower-latitude DOM were assigned to lignin-like species.
23519. 题目: Model study of organic carbon attenuation and oxygen mass transfer in persistent aggregate layers in the deep sea
文章编号: N20022112
期刊: Deep Sea Research Part II: Topical Studies in Oceanography
作者: Timothy J. Shaw, Corrianna Boucher, Christine L. Huffard, Kenneth L. Smith
更新时间: 2020-02-21
摘要: A time series study from 1989 to 2017 indicates that, increasingly, carbon export to abyssal sediments in the California Current Ecosystem (CCE), 220 km west of the central California coast (Sta. M), occurs as rapidly sinking pulses of particulate organic carbon (POC). Nearly continuous sediment trap collections confirm that POC export to 3400 m increased significantly after 2011 with carbon attenuation (as fraction of POC remineralized) ranging from a low of 57% to a high of 77% during periods of pulsed flux. All of the major pulse events for the period resulted in the delivery of detrital aggregates that covered part or all of the sediment surface as an organic carbon rich layer at ∼4000 m depth. However, the magnitude of the measured Sediment Community Oxygen Consumption (SCOC) did not increase proportionally to the organic carbon inventory change. Here, a model of oxygen consumption informed by the time series data at Sta. M in the CCE suggest that aggregate flocs constitute a major source for benthic carbon and a barrier to mass transport of oxygen to surface sediments leading to increased carbon attenuation in surface sediment layers. The correlation of POC delivery with aggregate coverage shows that the majority of POC delivery during pulse events is likely to consume all of the oxygen within the aggregates. Results indicate that an increasing fraction of POC reaching the abyssal sediments at Sta. M under conditions that support increased net burial of carbon. This finding is significant in the context of the fraction of the total POC flux that occurs as pulse events in this important upwelling region. During the period from 2011 to 2017, a third of the total POC flux resulted in aggregate flocs that covered a significant portion of the sediment surface (>47%). Following the 2015–2016 El Nino period the flocs became a dominant feature of the sediment surface. More than 80% of the POC flux to near bottom sediment traps in 2017 occurred coincident with aggregate floc cover of more than 90% of the sediments. The resultant physical barrier to oxygen transport and relatively low consumption of newly delivered carbon indicate conditions that are more typical of environments having low oxygen bottom waters.
23520. 题目: Estimating biogenic silica production of Rhizaria in the global ocean
文章编号: N20022111
期刊: Global Biogeochemical Cycles
作者: Natalia Llopis Monferrer, Demetrio Boltovskoy, Paul Tréguer, Miguel Méndez Sandin, Fabrice Not, Aude Leynaert
更新时间: 2020-02-21
摘要: Siliceous polycystines and phaeodarians are open‐ocean planktonic protists found throughout the water column and characterized by complex siliceous skeletons that are formed, at least partly, through the uptake of silicic acid. These protists contribute to the marine organic carbon (C) and biogenic silica (bSi) pools but little is known about their contribution to the silica (Si) biogeochemical cycle. Here we report the first measurements of the Si uptake rate of polycystine and phaeodarian cells from samples collected in the Mediterranean Sea using the 32Si based method. The elementary composition (bSi, particulate organic carbon and nitrogen) of these organisms was also measured. Combining our results with published data on the distribution and abundance of Polycystina and Phaeodaria in the global ocean, we conclude that these organisms could contribute from 0.2 to 2.2 mmol Si m‐2 of the marine standing stock of bSi and from 2 to 58 Tmol Si yr‐1 (1 to 19%) of the global oceanic biogenic silica production. The implications for the global marine Si cycle are discussed.