论文检索

总访问量：3952300次

总访客量：152836人

所有论文

28621. 题目: Modeling soil organic carbon dynamics in temperate forests using Yasso07
文章编号: N18061901
期刊: Biogeosciences
作者: Zhun Mao, Delphine Derrien, Markus Didion, Jari Liski, Thomas Eglin, Manuel Nicolas, Mathieu Jonard, and Laurent Saint-André
更新时间: 2018-06-19
摘要: Facing global changes, modeling and predicting the dynamics of soil carbon stock of forest ecosystems is vital but challenging work. Yasso07 is considered as one of the most promising models for such a purpose. We aim at examining the prediction accuracy of Yasso07 on soil carbon dynamics over the whole French metropolitan territory at a decennial time scale. We used the dataset from 101 RENECOFOR sites network, which encompass most of the French temperate forests. The data include (i) measured yearly litter quantity from aboveground organs part from 1994 to 2008, and soil carbon stocks twice at an interval of ca. 15 years (early 1990s versus around 2010). Using Yasso07, we simulated the stock changes (tCha-1yr-1) per site and compared them with the measured ones. We carried out meta-analyses to reveal the variability in litter biochemistry between different tree organs for conifers and broadleaves. We also performed sensitivity analyses to explore Yasso07’s sensitivity to inputs, including litter carbon quality and initial carbon stocks. At the national level, the simulated annual carbon stock changes (ACC, +0.45±0.09tCha-1year-1, mean±standard error) stayed in the same order of magnitude with the observed ones (+0.34±0.06tCha-1year-1). The correlation between predicted and measured ACC remained weak (R <0.1). There was significant overestimation for broadleaves sites and underestimation for conifers sites. Sensitivity analyses showed that the final carbon stock was weakly affected by litter carbon quality, but a strongly affected by simulation length to investigate and initial soil carbon quality. We revealed both interest and challenges of applying Yasso07 for temperate forests, which reflected the whole state-of-the-art of soil carbon modelling due to lacking knowledge or data on soil and litter carbon quality and fine root litter quantity, rendering high uncertainties for model inputs.

28622. 题目: Temporal response of soil organic carbon after grassland‐related land‐use change
文章编号: N18061801
期刊: Global Change Biology
作者: Wei Li, Philippe Ciais, Bertrand Guenet, Shushi Peng, Jinfeng Chang, Vincent Chaplot, Sergey Khudyaev, Anna Peregon, Shilong Piao, Yilong Wang, Chao Yue
更新时间: 2018-06-18
摘要: The net flux of CO2 exchanged with the atmosphere following grassland‐related land‐use change (LUC) depends on the subsequent temporal dynamics of soil organic carbon (SOC). Yet, the magnitude and timing of these dynamics are still unclear. We compiled a global data set of 836 paired‐sites to quantify temporal SOC changes after grassland‐related LUC. In order to discriminate between SOC losses from the initial ecosystem and gains from the secondary one, the post‐LUC time series of SOC data was combined with satellite‐based net primary production observations as a proxy of carbon input to the soil. Globally, land conversion from either cropland or forest into grassland leads to SOC accumulation; the reverse shows net SOC loss. The SOC response curves vary between different regions. Conversion of cropland to managed grassland results in more SOC accumulation than natural grassland recovery from abandoned cropland. We did not consider the biophysical variables (e.g., climate conditions and soil properties) when fitting the SOC turnover rate into the observation data but analyzed the relationships between the fitted turnover rate and these variables. The SOC turnover rate is significantly correlated with temperature and precipitation (p < 0.05), but not with the clay fraction of soils (p > 0.05). Comparing our results with predictions from bookkeeping models, we found that bookkeeping models overestimate by 56% of the long‐term (100 years horizon) cumulative SOC emissions for grassland‐related LUC types in tropical and temperate regions since 2000. We also tested the spatial representativeness of our data set and calculated SOC response curves using the representative subset of sites in each region. Our study provides new insight into the impact grassland‐related LUC on the global carbon budget and sheds light on the potential of grassland conservation for climate mitigation.

28623. 题目: Degradation of methadone by the sunlight/FC process: Kinetics, radical species participation and influence of the water matrix
文章编号: N18061701
期刊: Chemosphere
作者: Ming-Chi Hsieh, Sri Chandana Panchangam, Webber Wei-Po Lai, Angela Yu-Chen Lin
更新时间: 2018-06-17
摘要: Free chlorine sunlight photolysis (sunlight/FC) markedly enhances the degradation rate of methadone, a synthetic opioid used medically, over that obtained using sunlight alone. The pseudo-first-order rate constants of methadone degradation under acidic conditions ([methadone] = 0.2 μM, [free chlorine] = 4 μM, and pH = 4) for sunlight/FC and sunlight photolysis are 7.0 ± 1.1 × 10-2 min-1 and 1.4 ± 0.2 × 10-2 min-1, respectively. The improved methadone degradation can be attributed to the production of HO and reactive chlorine species (RCS) during sunlight/FC photolysis. HO and RCS predominantly accounted for degradation during sunlight/FC photolysis under acidic and neutral conditions, while direct photolysis was the major contributor towards methadone degradation in alkaline conditions. The initial pH (pH 4–11) and free chlorine concentration (1–6 μM) significantly influenced the overall degradation efficiency of methadone. The presence of HCO3 -, Cl- and dissolved organic matters, which may competitively react with HO and RCS, retard the degradation of methadone in synthetic wastewater. Consequently, a 50% lower methadone degradation rate was observed when deionized (DI) water was replaced with tap water. These results emphasize the need to consider different water matrices when applying sunlight/FC photolysis for water treatment.
图文摘要:

28624. 题目: Removal of precursors of typical nitrogenous disinfection byproducts in ozonation integrated with biological activated carbon (O3/BAC)
文章编号: N18061610
期刊: Chemosphere
作者: Jian Zheng, Tao Lin, Wei Chen, Hui Tao, Yiwen Tan, Baiwen Ma
更新时间: 2018-06-16
摘要: The O3/BAC process has been widely used in drinking water treatment to improve the removal of dissolved organic matters (DOMs), including the precursors of nitrogenous disinfection byproducts (N-DBPs). In this study, the removal of N-DBP precursors by biological activated carbon (BAC) filters with different usage time of granular activated carbon (GAC) was investigated. Results showed that the BAC filter with 6 years of usage time of GAC (old BAC filter) had a poor performance in the removal of precursors of N-DBPs such as dichloroacetonitrile (DCAN; an average of only 4.7%), dichloroacetamide (DCAcAm), and trichloronitromethane (TCNM) when compared with the BAC filter with 1 year of usage time of GAC (new BAC filter). Particularly, the organic fraction >10 kDa and the percentage of autochthonous substances were increased in the effluent of the old BAC filter. The red shift of the fluorescence peaks was evident in the excitation–emission matrix spectrum of the effluent from the old BAC filter. The abiotic adsorption of precursors by the old BAC filter was less. In addition, less amino acids and polysaccharides were removed, but more amino sugars and proteins were produced because of microbial metabolism. The metabolism strength of the attached biofilm decreased with increased operation time of the BAC filter. The relative abundance of Sphingomonas significantly decreased in the biofilm of the old BAC filter. The diversity of microbial community in the old BAC filter was higher, but the equitability was lower than those of the new BAC filter. The less removal of N-DBP precursors by the old BAC filter was attributed to the changes in abiotic adsorption capacity and microbial metabolism properties, in which soluble microbial products played an important role.

28625. 题目: Ultraviolet photosensitized transformation mechanism of microcystin-LR by natural organic matter in raw water
文章编号: N18061609
期刊: Chemosphere
作者: Qiyuan Sun, Tianfang Zhang, Feifeng Wang, Changqing Liu, Chunshan Wu, Rong-rong Xie, Yuyi Zheng
更新时间: 2018-06-16
摘要: Microcystins (MCs), produced by cyanobacterial blooms in eutrophic water, are common toxic metabolites and a potential threat to human health. However, the mechanism of MC photodegradation by photosensitizers in raw water remains unclear. In photodegradation and quenching experiments, this study investigates the photosensitized degradation of microcystin-LR (MC-LR) by fulvic acid (FA, a kind of dissolved organic matter with natural photosensitizing properties) under ultraviolet (UV) light irradiation. The photodegradation mechanisms of FA are also explored. The photodegradation process of MC-LR by FA was consistent with second-order reaction kinetics. The degradation rate of MC-LR in FA decreased from 80% to 55% as the pH increased from 3 to 9, because the binding ability of FA to MC-LR reduces as the pH increases. Given that FA can both inhibit and promote MC-LR degradation depending on its concentration, the optimum initial FA concentration for degrading MC-LR was determined as 9.86 mgC·L-1. The excited triplet state of FA (3FA ) accounted for 50.12% of the MC-LR loss; the remaining loss (49.88%) was contributed by reactive oxygen species and direct photolysis. This implies that the main pathway of MC-LR degradation is reaction with 3FA . The MC-LR degradation rate is 36% higher under UV irradiation than that under simulated sunlight irradiation.

28626. 题目: Formation of regulated and unregulated disinfection byproducts during chlorination of algal organic matter extracted from freshwater and marine algae
文章编号: N18061608
期刊: Water Research
作者: Chao Liu, Mahmut S. Ersan, Michael J. Plewa, Gary Amy, Tanju Karanfil
更新时间: 2018-06-16
摘要: Seasonal algal blooms in freshwater and marine water can increase the input of algal organic matter (AOM) to the pool of dissolved organic matter. The impact of bromide (Br-) and iodide (I-) on the formation of regulated and unregulated disinfection byproducts (DBPs) was studied from chlorination of AOM solutions extracted from three species of cultured isolates of freshwater and marine algae (Microcystis aeruginosa (MA), Synechococcus (SYN), and Alexandrium tamarense (AT)). Comparable concentrations of DBPs were formed from three types of AOM. In the absence of Br-, trihalomethanes (THMs), haloacetic acids (HAAs), and haloacetaldehydes (HALs) were the main groups of DBP formed, and haloacetonitriles (HANs) were formed at lower concentrations. In contrast, the formation of iodinated THMs was <8 nM (1.7 μg/L) since most of initial I was oxidized to iodate. Increasing initial Br concentrations increased the formation of THMs and HANs, while concentrations of total organic halogen and HAA remained stable. On the contrary, total HAL concentrations decreased due to the instability of bromated HALs. Decreasing the specific UV absorbance (SUVA) value of AOM favours bromine substitution since bromine more preferentially reacts with low reactivity organic matter than chlorine. Increasing the pH enhanced the formation of THMs but decreased the formation of HANs. Concentrations of HANs and HALs decreased at high pH (e.g., 9.0), high initial chlorine concentration and long reaction time due to the decomposition. Based on the cytotoxicity calculations, unregulated HANs and HALs were the main contributors for the total toxicity of DBPs measured, even though based on the weight regulated THMs and HAAs predominated.
图文摘要:

28627. 题目: Investigation on extracellular polymeric substances, sludge flocs morphology, bound water release and dewatering performance of sewage sludge under pretreatment with modified phosphogypsum
文章编号: N18061607
期刊: Water Research
作者: Quxiu Dai, Liping Ma, Nanqi Ren, Ping Ning, Zhiying Guo, Longgui Xie, Haijun Gao
更新时间: 2018-06-16
摘要: Modified phosphogypsum (MPG) was developed to improve dewaterability of sewage sludge, and dewatering performance, properties of treated sludge, composition and morphology distribution of EPS, dynamic analysis and multiple regression model on bound water release were investigated. The results showed that addition of MPG caused extracellular polymeric substances (EPS) disintegration through charge neutralization. Destruction of EPS promoted the formation of larger sludge flocs and the release of bound water into supernatant. Simultaneously, content of organics with molecular weight between 1000 and 7000 Da in soluble EPS (SB-EPS) increased with increasing of EPS dissolved into the liquid phase. Besides, about 8.8 kg kg 1DS of bound water was released after pretreatment with 40%DS MPG dosage. Additionally, a multiple linear regression model for bound water release was established, showing that lower loosely bond EPS (LB-EPS) content and specific resistance of filtration (SRF) may improve dehydration performance, and larger sludge flocs may be beneficial for sludge dewatering.
图文摘要:

28628. 题目: Surface properties of activated sludge-derived biochar determine the facilitating effects on Geobacter co-cultures
文章编号: N18061606
期刊: Water Research
作者: Peng Zhang, Shiling Zheng, Jia Liu, Bingchen Wang, Fanghua Liu, Yujie Feng
更新时间: 2018-06-16
摘要: Biochar has been reported to facilitate direct interspecies electron transfer (DIET) in co-cultures between Geobacter metallireducens and Geobacter sulfurreducens, a model defined co-culture system. In this study, the biochar derived from the activated sludge with different pyrolysis temperature was added to the co-cultures, the ethanol metabolism rates (Re) and succinate production rates (Rs) of co-culture with biochar-800 were 1.05- and 1.42-fold higher than that without addition. The results suggested that the conductivity of the biochar did not correlate with the facilitating effect of the biochar on the co-culture metabolism. Furthermore, the surface functional group and surface charge of biochar may also influence the facilitating effect on the interspecies electron transfer between the two Geobacter cells. Based on these results, it supported that the electron transfer depending on the charging and discharging process of the surface functional groups might play a major role in facilitating the direct electron transfer process by the biochar derived from activated sludge here. This study could shed light on the better understanding of the bacteria-biochar electron transfer system and the potential utilization of the biochar in the environmental wastewater treatments.
图文摘要:

28629. 题目: Diapycnal dissolved organic matter supply into the upper Peruvian oxycline
文章编号: N18061605
期刊: Biogeosciences
作者: Alexandra N. Loginova, S?ren Thomsen, Marcus Dengler, Jan Lüdke, and Anja Engel
更新时间: 2018-06-16
摘要: The Eastern Tropical South Pacific (ETSP) hosts the Peruvian upwelling system, which represents one of the most productive areas in the world ocean. High primary production followed by rapid heterotrophic utilization of organic matter supports the formation of one of the most intense oxygen minimum zones (OMZ) in the world ocean where dissolved oxygen (O2) concentrations reach well below 1 molkg 1. The high productivity leads to an accumulation of dissolved organic matter (DOM) in the surface layers that may serve as a substrate for heterotrophic respiration. However, the importance of DOM utilization for O2 respiration within the Peruvian OMZ remains unclear so far. Here, we evaluate the diapycnal fluxes of O2, dissolved organic carbon (DOC), dissolved organic nitrogen, dissolved hydrolysable amino acids (DHAA) and dissolved combined carbohydrates (DCCHO) and the composition of DOM in the ETSP off Peru to learn, whether labile DOM is reaching into the core of the OMZ and how important DOM utilization might be for O2 attenuation. The observed diapycnal 2 flux (50mmolO2m 2day 1 at max) was limited to the upper 80m of the water column, the flux attenuation of ~1 molL 1day 1, was comparable to previously published O2 consumption rates for the North and South Pacific OMZs. The diapycnal DOM flux (31mmolCm 2day 1 at max) was limited to ~30m water depth, suggesting that the labile DOM is already utilized within the upper part of the shallow oxycline off Peru. The analyses of DCCHO and DHAA composition support this finding, suggesting that DOM undergoes comprehensive remineralization already within the upper part of the oxycline, as the DOM within the core of the OMZ was found to be largely altered. Estimated by a simple equation for carbon combustion, aerobic respiration of DCCHO and DHAA, supplied by diapycnal mixing (0.46 molL 1day 1 at max), could account for up to 38% of the diapycnal O2 supply in the upper oxycline, which suggests that DOM utilization may play a significant role for shape of the upper Peruvian oxycline.

28630. 题目: Dimethyl phthalate elimination from micro-polluted source water by surface discharge plasma: Performance, active species roles and mechanisms
文章编号: N18061604
期刊: Journal of Hazardous Materials
作者: Tiecheng Wang, Guangzhou Qu, Xianqiang Yin, Qiuhong Sun, Dongli Liang, Xuetao Guo, Hanzhong Jia
更新时间: 2018-06-16
摘要: Plasticizer pollution brought huge risks to ecological environment and human health. Surface discharge plasma (SDP) was employed to eliminate plasticizer in natural water, with dimethyl phthalate (DMP) as a typical plasticizer. Experimental results showed that DMP degradation efficiency reached 82.8% within 60 min’s SDP treatment, and the elimination process fitted well the first-order kinetic model. Low initial DMP concentration, alkaline condition, and low natural organic matter content were all conducive for DMP degradation. The contributions of OH radical and O2 to DMP elimination were 91.9% and 78.1%, respectively. Total organic carbon (TOC), UV–vis spectroscopy, and atomic force microscopy analysis demonstrated that DMP molecular structure was destroyed after the SDP treatment, and some small molecular fractions were generated. Approximately 47.8% of TOC and 73.5% of COD were eliminated after 60 min’s SDP treatment. Phthalic acid monomethyl ester, phthalic acid, o-phthalic anhydride, acetic acid, formic acid, and oxalic acid were detected as the byproducts. Carbon balance analysis among these intermediates showed that total carbon content was approximately 4.64 × 10-2 mmol before treatment, and it was 4.578 × 10-2 mmol after treatment, suggesting that some C-containing intermediates still existed but not detected. DMP degradation pathways in the SDP system were proposed.

28631. 题目: Effect of surface modification on carbon nanotubes (CNTs) catalyzed nitrobenzene reduction by sulfide
文章编号: N18061603
期刊: Journal of Hazardous Materials
作者: Qi Liu, Han-Qing Zhao, Lei Li, Pan-Pan He, Yi-Xuan Wang, Hou-Yun Yang, Zhen-Hu Hu, Yang Mu
更新时间: 2018-06-16
摘要: Carbon nanotubes (CNTs) could be directly used as metal-free catalysts for the reduction of nitroaromatics by sulfide in water, but their catalytic ability need a further improvement. This study evaluated the feasibility of surface modification through thermal and radiation pretreatments to enhance catalytic activity of CNTs on nitrobenzene reduction by sulfide. The results show that thermal treatment could effectively improve the catalytic behaviors of CNTs for the reduction of nitrobenzene by sulfide, where the optimum annealing temperature was 400 °C. However, plasma radiation pretreatment didn’t result in an obvious improvement of the CNTs catalytic activity. Moreover, the possible reasons have been explored and discussed in the study. Additionally, the impacts of various operational parameters on nitrobenzene reduction catalyzed by the CNTs after an optimized surface modification were also evaluated. It was found that the rate of nitrobenzene removal by sulfide was positively correlated with CNTs doses in a range of 0.3–300 mg L-1; the optimum pH was around 8.0; higher temperature and sulfide concentration facilitated the reaction; and the presence of humic acid exhibited a negative effect on nitrobenzene reduction.
图文摘要:

28632. 题目: Evaluation of fouling in nanofiltration for desalination using a resistance-in-series model and optical coherence tomography
文章编号: N18061602
期刊: Science of The Total Environment
作者: Jongkwan Park, Sungyun Lee, Jeongyeop You, Sanghun Park, Yujin Ahn, Woonggyu Jung, Kyung Hwa Cho
更新时间: 2018-06-16
摘要: Resistance-in-series models have been applied to investigate fouling behavior. However, it is difficult to model the influence of morphology on fouling behavior because resistance is indirectly calculated from the water flux and transmembrane pressure. In this study, optical coherence tomography (OCT) was applied to evaluate the resistance of the fouling layer based on fouling morphology. Sodium alginate, humic acid, and bovine serum albumin (BSA) with high salts concentrations (conductivity: 23 mS/cm) were used as model foulants. At the same total fouling resistance, BSA showed the highest cake layer thickness (BSA (114.5 μm) > humic acid (53.5 μm) > sodium alginate (20.0 μm)). However, a different order was found for the cake layer resistance (BSA > sodium alginate > humic acid). This indicates that fouling thickness is not correlated with cake layer resistance. According to the Carman–Kozeny equation, fouling layer porosity decreased in the following order: humic acid (0.30) > BSA (0.21) > sodium alginate (0.20). In addition, we provided a specific value that was calculated using the ratio between the fouling thickness and cake layer resistance. The results show that alginic acid induced a stronger cake layer resistance, despite its thin fouling layer, whereas BSA showed a relatively low potential for inducing cake layer resistance. The results obtained in this study could be used for estimating and predicting fouling behavior.
图文摘要:

28633. 题目: Advanced Molecular Techniques Provide New Rigorous Tools for Characterizing Organic Matter Quality in Complex Systems
文章编号: N18061601
期刊: Journal of Geophysical Research: Biogeosciences
作者: Rachel M.Wilson, Malak M.Tfaily
更新时间: 2018-06-16
摘要: Carbon flux rates are widely understood to be substrate controlled; however, characterizing substrate quality continues to be a challenge. We suggest that, while optical measurements have their place, they are not the only, or the best, tool for characterizing organic matter quality. Nominal oxidation state of the carbon provides a thermodynamically relevant measure, which could be used as a metric of organic matter quality. Calculating nominal oxidation state of the carbon requires a suite of advanced complementary analysis but is then trivial to calculate from the resulting data sets.

28634. 题目: Influence of land use on distribution of soil n-alkane δD and brGDGTs along an altitudinal transect in Ethiopia: Implications for (paleo)environmental studies
文章编号: N18061502
期刊: Organic Geochemistry
作者: Andrea Jaeschke, Janet Rethemeyer, Michael Lappé, Stefan Schouten, Pascal Boeckx, Enno Schefu?
更新时间: 2018-06-15
摘要: The combined use of plant wax n-alkane δD values and branched glycerol dialkyl glycerol tetraether lipid (brGDGT) distributions provides a novel approach for paleoaltitude reconstruction. Studies from East Africa revealed, however, inconsistent results between the proxy estimates and altitudinal parameters. Here, we explore these proxies in soils of different land use (forest, cropland and pasture) along an altitudinal transect in the Jimma zone of the southwest Ethiopian highlands to better understand environmental and plant-specific factors controlling the isotopic composition and distribution of n-alkanes and brGDGTs. The hydrogen isotope composition of individual n-alkanes does not unambiguously reflect the altitude effect on precipitation δD, but seems largely influenced by the specific land use. Only forest soil-derived n-C27 and n-C29 alkane δD values exhibit a significant linear relationship with altitude (r -0.87, p < 0.05), likely reflecting the most stable ecosystem. The resulting lapse rate of -17‰/1000 m is comparable with that of local precipitation in the southwest Ethiopian highlands. In addition, the linear correlation of the average chain length (ACL) and δ13C values of forest soil n-alkanes suggests a physiological adaptation of the specific plant type waxes to altitude-induced environmental changes in the study area. The distribution of brGDGTs also reveals a significant linear correlation with altitude (r -0.97, p < 0.01), reflecting the decrease in temperature with higher elevation, independent of land use. In addition, brGDGT-based mean annual air temperature (MAT) estimates of 19.5°C to 14.0°C and temperature lapse rate of -6°C/1000 m are in good agreement with direct measurements in the Jimma zone. In contrast to previous studies from East Africa, our results show that both soil n-alkane δD values and brGDGT-based MAT distributions track present day altitude effects on local environmental gradients in the southwest Ethiopian highlands.

28635. 题目: Reactions of Ferrate(VI) with Iodide and Hypoiodous Acid: Kinetics, Pathways, and Implications for the Fate of Iodine during Water Treatment
文章编号: N18061501
期刊: Environmental Science & Technology
作者: Jaedon Shin, Urs von Gunten, David A. Reckhow, Sebastien Allard, and Yunho Lee
更新时间: 2018-06-15
摘要: Oxidative treatment of iodide-containing waters can form toxic iodinated disinfection byproducts (I-DBPs). To better understand the fate of iodine, kinetics, products, and stoichiometries for the reactions of ferrate(VI) with iodide (I–) and hypoiodous acid (HOI) were determined. Ferrate(VI) showed considerable reactivities to both I– and HOI with higher reactivities at lower pH. Interestingly, the reaction of ferrate(VI) with HOI (k = 6.0 × 103 M–1 s–1 at pH 9) was much faster than with I– (k = 5.6 × 102 M–1 s–1 at pH 9). The main reaction pathway during treatment of I–-containing waters was the oxidation of I– to HOI and its further oxidation to IO3– by ferrate(VI). However, for pH > 9, the HOI disproportionation catalyzed by ferrate(VI) became an additional transformation pathway forming I– and IO3–. The reduction of HOI by hydrogen peroxide, the latter being produced from ferrate(VI) decomposition, also contributes to the I– regeneration in the pH range 9–11. A kinetic model was developed that could well simulate the fate of iodine in the ferrate(VI)-I– system. Overall, due to a rapid oxidation of I– to IO3– with short-lifetimes of HOI, ferrate(VI) oxidation appears to be a promising option for I-DBP mitigation during treatment of I–-containing waters.
图文摘要:

28636. 题目: Sorption of lead ions onto oxidized bagasse-biochar mitigates Pb-induced oxidative stress on hydroponically grown chicory: Experimental observations and mechanisms
文章编号: N18061405
期刊: Chemosphere
作者: Mostafa F. El-Banna, Ahmed Mosa, Bin Gao, Xianqiang Yin, Zahoor Ahmad, Hongyu Wang
更新时间: 2018-06-14
摘要: This pilot study investigated the affinity of oxidized biochars to sorb lead ions (Pb2+) in aqueous solutions, and its potentiality to serve as bio-filters to detoxify Pb-induced oxidative stress on hydroponically grown chicory. Raw bagasse was slow-pyrolyzed at 600 °C to produce original biochar (O-B), which was further oxidized by HNO3 and KMnO4 to generate HNO3-B and KMnO4-B, respectively. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM), digital selected-area electron diffraction (SAED) and Fourier transform infrared spectroscopy (FTIR) analyses were performed to study physicochemical properties of pre-and post-sorption samples. Kinetic and isothermal batch sorption experiments proved the high affinity of oxidized biochar to Pb2+ ions. Both physisorption and chemisorption mechanisms participated mutually in sorption process. Leaf histochemistry analysis showed various dysfunctions on plants grown under severe Pb-stress including (i) induction of oxidative stress, (ii) deactivation in antioxidant enzymatic and non-enzymatic defense pathways, (iii) defects in plant water status, (iv) disruption in photosynthetic pigments synthesis, and (v) disturbance in the membrane permeability to solute leakage. Biochar filters (particularly KMnO4-B) exhibited a scavenging effect against these adverse effects by reducing Pb-bioavailability. Furthermore, the chemical characteristics of biochar and its derivatives (biochar-derived humic acids) provided additional stimulating effect to plant scavenging mechanisms. This ameliorative effect of biochar filters minimized the dramatic reductions in vegetative measurements of plants grown under severe Pb-stress. Hence, this study provides insights regarding the potentiality to functionalize biochar and its derivatives for heavy metal detoxification.

28637. 题目: Microbial decomposition processes and vulnerable Arctic soil organic carbon in the 21st century
文章编号: N18061404
期刊: Biogeosciences
作者: Junrong Zha and Qianlai Zhuang
更新时间: 2018-06-14
摘要: Inadequate representation of biogeochemical processes in current biogeochemistry models results in a large uncertainty in carbon budget quantification. Here, detailed microbial mechanisms were incorporated into a process-based biogeochemistry model, the Terrestrial Ecosystem Model (TEM). Ensemble regional simulations with the model estimated the Arctic ecosystem carbon budget is 76.0±114.8PgC during the 20th century, 3.1±61.7PgC under the RCP 2.6 scenario and a sink of 94.7±46PgC under the RCP 8.5 scenario during the 21st century. Compared to the estimates using a simpler soil decomposition algorithm in TEM, the new model estimated that the Arctic terrestrial ecosystems stored 12Pg less carbon over the 20th century, 19PgC and 30PgC less under the RCP 8.5 and RCP 2.6 scenarios, respectively, during the 21st century. When soil carbon within depths 30cm, 100cm and 300cm was considered as initial carbon in the 21st century simulations, the region was estimated to accumulate 65.4, 88.6, and 109.8PgC, respectively, under the RCP 8.5 scenario. In contrast, under the RCP 2.6 scenario, the region lost 0.7, 2.2, and 3PgC, respectively, to the atmosphere. We conclude that the future regional carbon budget evaluation largely depends on whether or not the adequate microbial activities are represented in earth system models and the sizes of soil carbon considered in model simulations.

28638. 题目: Role of drinking water biofilms on residual chlorine decay and trihalomethane formation: An experimental and modeling study
文章编号: N18061403
期刊: Science of The Total Environment
作者: Jianeng Xu, Conghui Huang, Xiaoyang Shi, Shengkun Dong, Baoling Yuan, Thanh H. Nguyen
更新时间: 2018-06-14
摘要: PVC pipe loops were constructed to simulate household premise plumbing. These pipe loops were exposed to water treated by physical processes at three water treatment plants in Xiamen, China from August 2016 to June 2017. After the biofilms were allowed to develop inside the pipes, these pipes were deconstructed and exposed to organic-free chlorine solution buffered at pH 6.8 ± 0.2 for 48 h. The decay of chlorine by these biofilms was higher than by the effluent waters that were used to grow the biofilms. A chlorine consumption mass balance model elucidated the role of both the diffusion of chlorine into the biofilm and the reaction of chlorine with the biofilm matrix. Comparable concentrations of trihalomethanes were quantified from the reaction between chlorine and source water organic matters, and chlorine and the biofilm, further emphasizing the role of biofilms in the safety of disinfected drinking water. These findings imply that when chlorine is used in the drinking water distribution system, the ubiquitous presence of biofilms may cause the depletion of chlorine and the formation of non-negligible levels of toxic disinfection byproducts.
图文摘要:

28639. 题目: Stabilization of Ag–Au Bimetallic Nanocrystals in Aquatic Environments Mediated by Dissolved Organic Matter: A Mechanistic Perspective
文章编号: N18061402
期刊: Environmental Science & Technology
作者: Theodore E. G. Alivio, Nathan A. Fleer, Jashanpreet Singh, Govind Nadadur, Mingbao Feng, Sarbajit Banerjee, Virender K. Sharma
更新时间: 2018-06-14
摘要: Gold and silver nanoparticles can be stabilized endogenously within aquatic environments from dissolved ionic species as a result of mineralization induced by dissolved organic matter. However, the ability of fulvic and humic acids to stabilize bimetallic nanoparticles is entirely unexplored. Elucidating the formation of such particles is imperative given their potential ecological toxicity. Herein, we demonstrate the nucleation, growth, and stabilization of bimetallic Ag–Au nanocrystals from the interactions of Ag+ and Au3+ with Suwannee River fulvic and humic acids. The mechanisms underpinning the stabilization of Ag–Au alloy NPs at different pH (6.0–9.0) values are studied by UV–vis spectrophotometry, X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED). Complexation of free Ag+ and Au3+ ions with the Lewis basic groups (carbonyls, carboxyls, and thiols) of FA and HA, followed by electron-transfer from redox-active moieties present in dissolved organic matter initiates the nucleation of the NPs. Alloy formation and interdiffusion of Au and Ag atoms are further facilitated by a galvanic replacement reaction between AuCl4– and Ag. Charge-transfer from Au to Ag stabilizes the formed bimetallic NPs. A more pronounced agglomeration of the Ag–Au NPs is observed when HA is used compared to FA as the reducing agent. The bimetallic NPs are stable for greater than four months, which suggests the possible persistence and dispersion of these materials in aquatic environments. The mechanistic ideas have broad generalizability to reductive mineralization processes mediated by dissolved organic matter.
图文摘要:

28640. 题目: Mg–Fe layered double hydroxide assembled on biochar derived from rice husk ash: facile synthesis and application in efficient removal of heavy metals
文章编号: N18061401
期刊: Environmental Science and Pollution Research
作者: Jianan Yu, Zhiliang Zhu, Hua Zhang, Yanling Qiu, Daqiang Yin
更新时间: 2018-06-14
摘要: The pollution of toxic and persistent heavy metals commonly exist in water environment; such multi-component pollutants pose a serious threat to human beings and other organisms. Herein, to make full use of the advantages of both layered double hydroxide (LDH) and rice husk ash (RHA), a novel Mg–Fe-LDH-RHA functional material was synthesized by assembling LDH on the biochar derived from RHA and used as an adsorbent for removal of heavy metal ions including Pb2+, Cu2+, Co2+, Ni2+, Zn2+, and Cd2+. The adsorption kinetics and isotherms of heavy metal ions in a mono-component system, the adsorption capacities in mixed multi-metal ion system, and the regeneration of the adsorbent were studied in detail. The results showed that the synthesized Mg–Fe-LDH-RHA might efficiently remove the above six heavy metals in water under optimized experimental conditions. Interestingly, the removal performance toward Pb(II) showed high static distribution coefficients (Kd) of ~ 10^7 mL/g and maximum capacity of ~ 682 mg/g. Besides, further characterizations of the adsorbent have been conducted, and the result suggested the formation of abundant functional groups including hydroxyl, carbonyl, and carboxyl groups. The removal mechanism of the metal ions might be related to ion-exchange, surface precipitation, complexation, and hydrogen binding during the interactions between the LDH-RHA material and pollutants. Such a facile and environmentally friendly approach, efficient removal performance suggests that the LDH-RHA material thus has potential for efficient removal of heavy metals in practical application.