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25661. 题目: Rapid prediction of the activated carbon adsorption ratio by a regression model
文章编号: N19122519
期刊: Chemosphere
作者: Xin Huang, Jianwei Yu, Baoyou Shi, Haotian Hao, Chunmiao Wang, Zeyu Jia, Qi Wang
更新时间: 2019-12-25
摘要: Regression analysis of micropore volume and particle size of powdered activated carbon (PAC) is applied to develop a model to predict the adsorption ratio of a non-polar compound, 2-methylisorneol (2-MIB), onto PACs. This model likewise predicts the adsorption ratio of the same PACs and other PACs in background water containing similar natural organic matter (NOM). When this model is used to predict the same PACs adsorption ratios at 30 and 50 mg L⁻¹, the respective percent sample deviations standard error (SDEV) is of 30% SDEV and 12% were obtained. Further, the model is also employed for the prediction of 2-MIB adsorption capacities for 12 different PACs in water with similar NOM at the same dosages, with average SDEV values of 44% and 28%, respectively. Results indicate that 2-MIB adsorption occurrs mainly through the micropore filling mechanism. Nevertheless, when this model is expanded to predict PAC adsorption of NOM with different properties in water, the results exhibited rather large errors. Though this model cannot be applied to waters containing NOM with different properties, it provides information for water utilities themselves or the ones using similar source water to predict the PAC dosage without any adsorption experiment when change of PAC is needed.
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25662. 题目: Fluorescence characteristics and biodegradability of dissolved organic matter (DOM) leached from non-point sources in southeastern China
文章编号: N19122518
期刊: Environmental Pollution
作者: Nitao Gu, Qingbin Song, Xueling Yang, Xubiao Yu, XiaoMing Li, Gang Li
更新时间: 2019-12-25
摘要: Under the increasingly intensive measures for surface water restoration in China, point source discharge has been strictly regulated; however, for non-point sources, which constitute a large part of surface water pollutants, effective control has been difficult to reach. A comprehensive understanding of the characteristics of non-point source pollutants is essential for surface water improvement programs of cities such as Ningbo, on the southeast coast of China. Ningbo has made tremendous efforts in the past few years to control point source pollutants, but available data and management strategies on the non-point source pollutants are still limited. To this end, leachates of representative non-point source samples from the territory of Ningbo, including cropland and wetland soil, urban channel sediment, and poultry manure, were examined and compared focusing on the fluorescence characteristics and biodegradability of the dissolved organic matter (DOM). Results indicated that biodegradable dissolved organic carbon (BDOC) accounting for the total DOC was 46.7 ± 0.7% for cropland, wetland (56.3 ± 6.8%), non-sewage channel (60.1 ± 0.4%), sewage channel (74.5 ± 1.1%), and poultry manure (62.7 ± 4.5%). The leachates of the studied samples showed significant differences in both the amount and composition of DOM. However, a fluorescence component representing tryptophan-like substances identified by the excitation-emission matrix (EEM) combined with parallel factor (PARAFAC) analysis effectively predicted the BDOC variations among the studied samples. Moreover, under the studied nutrient concentrations, which were equivalent to Grade III water quality in China, nutrient limitation of microbial degradation was not observed. Threats to water quality, especially excessive consumption of dissolved oxygen, could be posed by the non-point source leachates due to their high bioavailability, large distribution, and weak nutrient restraint. Further investigations, including a quantitative evaluation of the non-point source pollution contribution, and pollutant blocking techniques are required.
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25663. 题目: Interaction and coexistence characteristics of dissolved organic matter with toxic metals and pesticides in shallow groundwater
文章编号: N19122517
期刊: Environmental Pollution
作者: Xiao-Song He, Ya-Li Zhang, Zhen-Hai Liu, Dan Wei, Gang Liang, Hong-Tao Liu, Bei-Dou Xi, Zhan-Bin Huang, Yan Ma, Bao-Shan Xing
更新时间: 2019-12-25
摘要: The long-term and large-scale utilization of fertilizers and pesticides in facility agriculture leads to groundwater pollution. However, the coexistence and interactions between organic fertilizers (i.e., organic matter), toxic metals, and pesticides in shallow groundwater have seldom been studied. Thus, the study sought to characterize said interactions via fluorescence, ultraviolet–visible spectroscopy (UV–Vis), and Fourier-transform infrared spectroscopy coupled with two-dimensional correlation spectroscopy and chemometric techniques. The results indicated that groundwater DOM was comprised of protein-, polysaccharide-, and lignin-like substances derived from organic fertilizers. Protein-like substances accounted for the binding of Co, Ni, and Fe, while polysaccharide- and lignin-like substances were mainly responsible for Cr and Mo complexation. Moreover, lignin- and polysaccharide-like substances played a key role in the binding of pesticides (i.e., dichlorodiphenyltrichloroethane [DDT], endosulfan, γ-hexachlorocyclohexane [γ-HCH], monocrotophos, chlorpyrifos, and chlorfenvinphos), rendering the conversion of γ-HCH to β-hexachlorocyclohexane (β-HCH) and the degradation of DDT to dichlorobenzene dichloroethylene (DDE) ineffective. However, the presence of protein-like substances in groundwater benefited the degradation and conversion of γ-HCH and α-endosulfan. Redundancy analyses showed that lignin- and polysaccharide-like matter had the most impacts on the coexistence of DOM with toxic metals and pesticides.
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25664. 题目: Cultivation substrata differentiate the properties of river biofilm EPS and their binding of heavy metals: A spectroscopic insight
文章编号: N19122516
期刊: Environmental Research
作者: Longfei Wang, Wei Chen, Xiaochong Song, Yi Li, Wenlong Zhang, Huanjun Zhang, Lihua Niu
更新时间: 2019-12-25
摘要: River biofilms inevitably serve as recipients of heavy metals including copper (Cu) and cadmium (Cd) following their introduction in fluvial systems. Nevertheless, the effects of cultivation substrata on the characteristics of river biofilm extracellular polymeric substances (EPS) and the binding behaviors of heavy metals on biofilms remain unclear. Integrating spectroscopic methods with chemometric analyses, we explored the binding behaviors of Cu(II) and Cd(II) onto biofilm EPS cultivated from two representative substrata at the molecular level. Chemical analysis revealed that biofilm cultivated on polyethylene (PE) pieces contained more non-fluorescent protein fractions, whereas EPS from periphyton grown on mineral, i.e., cobblestones was richer in aromatic fractions and polysaccharides. Excitation-emmision matrix combined with parallel factor analysis suggested a stronger interaction between fluorophores in periphytic EPS with Cu(II) compared to fluorophores in plastic biofilm EPS. Integrated use of infrared spectroscopy and two-dimensional correlation analyses revealed that, during the heavy metal binding processes, the amines and phenolics in plastic biofilm EPS gave the fastest responses to metal binding. While the amides and the aliphatic fractions in periphytic EPS showed a preferential binding to heavy metals. This study differentiates the effects of cultivation substrata on structuring the biofilm EPS characteristics and offers new insights into the environmental behaviors of heavy metal discharge into fluvial systems in river biofilm matrix.
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25665. 题目: A combined first principles and classical molecular dynamics study of clay-soil organic matters (SOMs) interactions
文章编号: N19122515
期刊: Geochimica et Cosmochimica Acta
作者: Yingchun Zhang, Xiandong Liu, Chi Zhang, Xiancai Lu
更新时间: 2019-12-25
摘要: In this study, clay-soil organic matters (SOMs) interactions were investigated by combining first principles molecular dynamics (FPMD) and classical molecular dynamics (CMD) techniques. FPMD was employed to quantify the binding mechanisms of reactive SOMs groups on clay surfaces and to derive parameters for the bonding of the reactive groups on edge surfaces. By integrating the derived parameters with CVFF–CLAYFF force fields, CMD simulations were carried out to investigate the structures of large models of clay-SOMs associations. All possible reactive SOMs groups, including carboxylate, phosphate, quinone species and ammonium groups were taken into account. FPMD results showed that all these groups are important to the complexation of SOMs on clay surfaces under dry conditions but only chemical bonding of carboxylate and phosphate and cation bridging are of significance under wet conditions. pH dependence of carboxylate and phosphate and Eh-pH dependence of quinone species are presented. CMD simulations showed that SOMs bound on clay surfaces via direct bonding of carboxylate and Ca²⁺ bridging and revealed the effect of water on structures of the clay-SOMs association. Based on the computational results, a procedure was proposed for constructing realistic molecular models for soils. Possible applications and further improvements of these models are discussed.

25666. 题目: Long-term spatial and temporal patterns of polycyclic aromatic hydrocarbons (PAHs) in Scottish soils over 20 years (1990–2009): A national picture
文章编号: N19122514
期刊: Geoderma
作者: Song Cui, Zulin Zhang, Qiang Fu, Rupert Hough, Kyari Yates, Mark Osprey, Godiya Yakowa, Malcolm Coull
更新时间: 2019-12-25
摘要: Long-term spatial and temporal concentrations of polycyclic aromatic hydrocarbons (PAHs) in Scottish soils from four transects were measured in three national-scale surveys conducted between 1990 and 2009. Measured concentrations of 16 priority PAHs ranged from 15,690 to 83.7 ng g⁻¹, with an average of 3659 ± 3131 to 727 ± 654 ng g⁻¹, of which the high molecular weight (HMW) PAHs (4–6 rings) accounted for 73.9 to 89.6%. Overall, concentrations of PAHs in the soil have decreased over time, but the proportion of carcinogenic ∑PAH₇ has increased. Concentrations of total PAHs correlated significantly with latitude (R = −0.345, p = 0.001). A significant correlation was found between concentrations of PAHs and soil organic carbon (SOC, R = 0.439, p = 0.000), which is an important factor, influencing the levels of PAHs in soils. Source apportionment analysis indicated that the emission sources of PAHs have evolved from coal and biomass combustion to more diverse sources during the two decades covered by the surveys. It is likely that this reflects societal development towards a lower carbon economy and less use of biomass buring for domestic space heating.

25667. 题目: Evaluation of ferrihydrite-humic acid coprecipitate as amendment to remediate a Cd- and Pb-contaminated soil
文章编号: N19122513
期刊: Geoderma
作者: Miaomiao Xu, Zhuanjun Zhao, Yiran Song, Jing Li, Yang You, Jie Li
更新时间: 2019-12-25
摘要: Heavy metals will accumulate continuously after entering the soil environment, which will adversely affect soil quality and harm to human health through the food chain. Among many soil remediation methods, stabilization methods for applying amendments to soil are widely used because of their higher cost-effectiveness and lower environmental impact. In order to evaluate the actual remediation effect of soil amendments, more means are needed to confirm. In this paper, the effects of Fh-HA (Ferrihydrite-Humic acid) coprecipitate as amendment on soil environmental quality of Cd- and Pb-contaminated soil was evaluated by combining the changes of heavy metals fractionation, TCLP-leachable concentration and soil enzyme activity. The experimental data showed that the Fh-HA coprecipitate could greatly enhance the stabilization of Cd and Pb, and promote its transformation from labile fractions to stable fractions. And coprecipitate could also reduce both the TCLP-leachable Cd and Pb, with the maximum reduction efficiencies of 50.7% and 74.8%, respectively. The activities of urease, catalase and alkaline phosphatase increased up to 62.7%, 50.8% and 38.5%, respectively, at a coprecipitate addition of 10%. At the same time, the soil pH was almost unchanged. The results indicated that the application of Fh-HA coprecipitate amendment has a positive effect on improving the quality of terrestrial environment, and no effect on soil physical and chemical properties. The Fh-HA coprecipitate can be further investigated as an economical and environmentally friendly amendment.

25668. 题目: Responses of enzymatic activity and microbial communities to biochar/compost amendment in sulfamethoxazole polluted wetland soil
文章编号: N19122512
期刊: Journal of Hazardous Materials
作者: Jie Liang, Siqun Tang, Jilai Gong, Guangming Zeng, Wangwang Tang, Biao Song, Peng Zhang, Zhaoxue Yang, Yuan Luo
更新时间: 2019-12-25
摘要: Biochar and compost, two common amendments, were rarely conducted to investigate their combined influence on enzymatic activities and microbial communities in organic-polluted wetlands. This article described the effects of biochar/compost on degradation efficiency of sulfamethoxazole (SMX) and ecosystem responses in polluted wetland soil during the whole remediation process. 1% biochar (SB1) increased degradation efficiency of SMX by 0.067% ascribed to the increase of dehydrogenase and urease. 5% biochar (SB5) decreased degradation efficiency by 0.206% due to the decrease of enzymes especially for dehydrogenase. 2% compost (SC2), 1% biochar & 2% compost (SBC3), both 10% compost (SC10) and 5% biochar & 10% compost (SBC15) enhanced degradation efficiency by 0.033%, 0.015% and 0.222%, respectively, due to the increase of enzymes and biomass. The degradation efficiency was positively related to biomass and enzymatic activities. High-throughput sequencing demonstrated that HCGs (SB5, SC10, SBC15) improved the bacterial diversities but reduced richness through introducing more exogenous predominance strains and annihilated several inferior strains, while LCGs (SB1, SC2, SBC3) exhibited lower diversities but higher richness through enhanced the RAs of autochthonal preponderant species and maintained some inferior species. Additionally, HCGs raised the RAs of amino and lipid metabolism gene but lowered those of carbohydrate compared with LCGs.
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25669. 题目: Stabilization and solidification of arsenic and iron contaminated canola meal biochar using chemically modified phosphate binders
文章编号: N19122511
期刊: Journal of Hazardous Materials
作者: Parmila Devi, Prachi Kothari, Ajay K. Dalai
更新时间: 2019-12-25
摘要: Adsorption is a widely used process for removal of heavy metals, but the management of spent adsorbent containing concentrated amounts of heavy metals is a problem due to potential risk of groundwater contamination from leaching of heavy metals. Generally, cementitious binder and additives are used for stabilization and solidification treatment, however heavy metals tend to leach from such matrices. Therefore, this research investigated the effectiveness of chemically modified phosphate biochar (CMPB) composite for the simultaneous solidification and stabilization of arsenic (As) and iron (Fe) contaminated canola meal biochar. Results showed that the performance of spent biochar added CMPB composites was significantly better than the pure composites (without biochar) due to filling of inter-aggregate pores using biochar and availability of sufficient amount of MgKPO₄ for binding of biochar particles. Moreover, leaching test and risk assessment studies indicated that there is no potential adverse effect as the concentrations of As and Fe in TCLP leachate were well below the Universal Treatment Standard (UTS) in optimized CMPB composites. In conclusion, chemically modified phosphate binders were found effective in stabilization and solidification of As and Fe contaminated biochar into thermodynamically stable material with high immobilization capacity and low leachability.
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25670. 题目: New insights into aniline toxicity: Aniline exposure triggers envelope stress and extracellular polymeric substance formation in Rubrivivax benzoatilyticus JA2
文章编号: N19122510
期刊: Journal of Hazardous Materials
作者: Mujahid Mohammed, Lakshmi Prasuna Mekala, Sasikala Chintalapati, Venkata Ramana Chintalapati
更新时间: 2019-12-25
摘要: Aniline is a major environmental pollutant of serious concern due to its toxicity. Although microbial metabolism of aniline is well-studied, its toxic effects and physiological responses of microorganisms to aniline are largely unexplored. Rubrivivax benzoatilyticus JA2, an aniline non-degrading bacterium, tolerates high concentrations of aniline and produces extracellular polymeric substance(EPS). Surprisingly, strain JA2 forms EPS only when exposed to aniline and other toxic compounds like organic solvents and heavy metals indicating that EPS formation is coupled to cell toxicity. Further, extensive reanalysis of the previous proteomic data of aniline exposed cells revealed up-regulation of envelope stress response(ESR) proteins such as periplasmic protein folding, envelope integrity, transmembrane complex, and cell-wall remodelling proteins. In silico analysis and molecular modeling of three highly up-regulated proteins revealed that these proteins were homologous to CpxARP proteins of ESR signalling pathway. Furthermore, EPS formation to known ESR activators(Triton-X-100, EDTA) suggests that envelope stress possibly regulating the EPS production. The present study suggests that aniline triggers envelope stress; to counter this strain JA2 activates ESR pathway and EPS production. Our study revealed the hitherto unknown toxic effects of aniline as an acute envelope stressor thus toxicity of aniline may be more profound to life-forms than previously thought.
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25671. 题目: Effects of biochar and organic substrates on biodegradation of polycyclic aromatic hydrocarbons and microbial community structure in PAHs-contaminated soils
文章编号: N19122509
期刊: Journal of Hazardous Materials
作者: Huanyu Bao, Jinfeng Wang, He Zhang, Jiao Li, Hui Li, Fuyong Wu
更新时间: 2019-12-25
摘要: A incubation experiment was conducted to investigate whether combined amendment of biochar (B) and compost (CP), mushroom residue (M) and corn straw (Y) could enhance biodegradation of polycyclic aromatic hydrocarbons (PAHs) in contaminated soils. After 77 days of incubation, both B + M and B + Y significantly (p < 0.01) increased removal rate of PAHs compared with amendment of biochar alone. However, B+CP resulted in a significant (p < 0.01) decreasing of PAHs removal. Compared with no biochar and no organic substrates addition (CK) and B, both B+M and B+Y significantly (p < 0.01) enhanced concentrations of dissolved organic carbon (DOC) and were favorable for the microbial growth reflected by microbial biomass carbons (MBC) and emission of carbon dioxide. Redundancy analysis (RDA) indicated that B + CP, B + M and B + Y separated the bacterial community compared with CK and B. However, the community composition structure in B + CP was different from that of B + M and B + Y. Moreover, the abundance of some PAHs degraders and PAH degradation genes predicted by PICRUSt software was promoted by B + M or B + Y, whereas that was inhibited under B + CP. The present study suggested that both B + M and B + Y could accelerate biodegradation of PAHs mainly through increasing the concentration of DOC and the abundances of microbial PAH degraders in soils.

25672. 题目: Photodegradation of metoprolol in the presence of aquatic fulvic acids. Kinetic studies, degradation pathways and role of singlet oxygen, OH radicals and fulvic acids triplet states
文章编号: N19122508
期刊: Journal of Hazardous Materials
作者: Olga M.S. Filipe, Eduarda B.H. Santos, Marta Otero, Elsa A.C. Gonçalves, M. Graça P.M.S. Neves
更新时间: 2019-12-25
摘要: Metoprolol is a pharmaceutical used for the treatment of cardiovascular diseases and disorders, whose frequent detection in surface waters raises concern. Indirect photodegradation is an important degradation pathway in waters and dissolved organic matter has a major role as photosensitizer. In this study, metoprolol photodegradation, in the absence and in the presence of fulvic acids extracted from the Vouga River (Portugal) (VRFA), was assessed under simulated sunlight. While metoprolol direct photodegradation was deniable, indirect photolysis occurred under the presence of VRFA. It followed a pseudo-first order kinetics and after 72 h of irradiation there was a decrease of metoprolol concentration of ∼80 %. The OH radical (OH) was verified to be the main reactive species (RS) responsible for the photosensitized degradation of metoprolol, but other RS are also involved, probably triplet excited states of FA (³FA*) and singlet oxygen (¹O₂), as demonstrated by the higher inhibition of the photodegradation in presence of sodium azide than in presence of 2-propanol. Based on a previous identification of photoproducts, tentative degradation mechanisms were here proposed. Photoproducts analysis after 24 h irradiation in the absence and presence of scavengers, shown that different RS are involved in the formation of different products/intermediates.
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25673. 题目: Sorption and desorption behaviors of triphenyl phosphate (TPhP) and its degradation intermediates on aquatic sediments
文章编号: N19122507
期刊: Journal of Hazardous Materials
作者: Peifang Wang, Dandan Li, Xiulei Fan, Bin Hu, Xun Wang
更新时间: 2019-12-25
摘要: As triphenyl phosphate (TPhP) can biodegrade extensively in sediments, researches should further the understanding of the fate and transport of TPhP and its degradation intermediates in the environment. Therefore, the sorption/desorption behaviors of TPhP, diphenyl phosphate (DPhP) and phenyl phosphate (PhP) on sediments were investigated. The kinetic process was well-fitted by pseudo-second-order model, suggesting that chemisorption was involved. And the Langmuir model could describe the sorption isotherms of TPhP and DPhP well except for PhP. The redundancy analysis revealed that the sorption amount had a positive correlation with sediment organic matter, zeta potential and C/H of sediments. Besides the sorption/desorption behaviors were greatly influenced by the physicochemical properties of the sorbates. PhP with high molecular electrostatic potential (0.132 e⁰) was prone to protonation and formed hydrogen bonds, leading to higher sorption. Furthermore, hydrophobicity, π-π interactions, Lewis acid-base interaction and hydrogen bonding were involved in the sorption process and resulted in nonlinear sorption isotherms. TPhP, DPhP and PhP exhibited apparent desorption hysteresis on the sediments. Sediments with organic matter removed, which have complex pore distributions, exhibited more hysteresis. These results may contribute to the risk assessment and fate modeling of TPhP and its degradation products in sediments.
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25674. 题目: A DNA-based biosensor for aqueous Hg(II): Performance under variable pH, temperature and competing ligand composition
文章编号: N19122506
期刊: Journal of Hazardous Materials
作者: Kunfu Pi, Juewen Liu, Philippe Van Cappellen
更新时间: 2019-12-25
摘要: Mercury (Hg) is a toxic metal posing major health risks to human beings and wildlife. The characterization of Hg fate and transport in aquatic environments is hindered by a lack of sensitive, selective and easily field-deployable analytical techniques. Here we assess the reliability and performance of a Hg²⁺ sensor based on the selective binding of Hg²⁺ to a thymine-rich DNA under environmentally-relevant conditions. Experimental results indicate that the interactions between the DNA and SYBR Green I, which produce the detection fluorescence signal, are significantly impacted by pH, metal ligands and natural dissolved organic matter (NDOM). These interferences are largely eliminated by immobilizing the DNA in a polyacrylamide hydrogel, although high concentrations of NDOM, such as fulvic acids, still affect the sensor’s performance due to competitive binding of Hg²⁺. The binding of Hg²⁺ to NDOM, however, can be accounted for via equilibrium speciation calculations, which also yield the complexation constant for Hg²⁺ binding to the DNA in the hydrogel. The equilibrium calculations reproduce the results for the entire set of experimental conditions, from simple electrolyte solutions to complex aqueous compositions mimicking natural lake waters, and across large ranges of pH (3-10) and temperature (5-50 °C).
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25675. 题目: Effects of reduced graphene oxide on humic acid-mediated transformation and environmental risks of silver ions
文章编号: N19122505
期刊: Journal of Hazardous Materials
作者: Bin Dong, Guangfei Liu, Jiti Zhou, Jing Wang, Ruofei Jin, Ying Zhang
更新时间: 2019-12-25
摘要: The reduction of Ag⁺ mediated by natural organic matters has been demonstrated to be an important process of Ag⁺ transformation and would influence the risks of Ag⁺ and Ag-containing materials in aquatic environment. Considering the large production of carbon nanomaterials (CNMs) and their inevitable release into the environment, the effects of CNMs on Ag transformation are of considerable interest. This study demonstrated that the humic acid-mediated reduction of Ag⁺ to free Ag nanoparticles (AgNPs) in aqueous phase was suppressed by coexisting reduced graphene oxide (rGO). A large amount of Ag⁺ was reduced on rGO surface, resulting in the generation of AgNPs-rGO composites. rGO at concentrations of 1–2 orders of magnitude lower than those of Ag⁺ would exhibit significant effects. The X-ray absorption fine structure spectroscopy study showed that Ag⁺ was first adsorbed on rGO surface cooperatively with humic acid and then rapidly reduced to AgNPs. The hydroxylic-OH on rGO could participate in the AgNPs formation and was oxidized to carbonyl during the reduction of Ag⁺. Additionally, the formed AgNPs-rGO had a relatively lower environmental risk compared to AgNPs or rGO alone. Overall, these results improve our understanding of the interaction between CNMs and Ag⁺ in aquatic systems.
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25676. 题目: Optical properties as tracers of riverine dissolved organic matter biodegradation in a headwater tributary of the Yangtze
文章编号: N19122504
期刊: Journal of Hydrology
作者: Maofei Ni, Siyue Li
更新时间: 2019-12-25
摘要: The optical properties can characterize the chemical composition, bioavailability and origins of dissolved organic matter (DOM), and thus indicate its biodegradability in natural waters. However, there remains a large gap in how DOM optical properties (UV-visible and fluorescence spectra) trace and predict the dissolved organic carbon biodegradation (%BDOC) in river systems. Over a 56-day laboratory incubation experiment, we examined the variations of %BDOC and DOM optical properties in a headwater tributary of the upper Yangtze River. We found that DOC biodegradability was significantly higher in the tributaries (20°C: 38.9 ± 19.8%; 30°C: 58.6 ± 19.5%) than that in the main stem (20°C: 26.1 ± 18.2%: 30°C: 41.8 ± 16.3%) (p < 0.001). The %BDOC, exhibiting coincident peaks in the agricultural regions and troughs in the ecologically fragile regions, increased by a factor of two-fold with a temperature gradient of 10℃. The optical properties SUVA₂₅₄ and S_275-295 decreased, while the S_350-400, FI and BIX increased after the incubations, implying the synchronous biodegradation and production of young DOMs via microbial respiration. The %BDOC:DOC tightly linked to a₂₅₄, S_275-295, S_350-400 and BIX, illustrating that optical properties could predict the riverine %BDOC. The findings demonstrated that optical properties could be regarded as the useful tracers of DOM biodegradation in river systems.
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25677. 题目: Rhizobial exopolysaccharides as supplement for enhancing nodulation and growth attributes of Cajanus cajan under multi-stress conditions: A study from lab to field
文章编号: N19122503
期刊: Soil and Tillage Research
作者: Sakshi Tewari, Shilpi Sharma
更新时间: 2019-12-25
摘要: The present study aimed to enhance nodulation and productivity of Cajanus cajan (pigeon pea) by using rhizobia, and its metabolite, in stressed soil of Northern India where conditions of high alkalinity (pH 8.9), temperature (45 °C) and mineral N [33 ppm NO₃–N (nitrate) and 48 ppm NH₄–N (ammonium)] occur in combination. Farmers in the region excessively use NP fertilizers that disturbs soil ecology, and inhibits nodule formation in pigeon pea. Initial experiments were conducted in laboratory for shortlisting potent rhizobial strains. Initially survivability of different rhizobial strains was monitored under mono-stress conditions (one stress applied on bacterial strain at a time (temperature, pH or fertilizer) on yeast extract mannitol agar medium. Shortlisted strain IC3123 displayed survivability under diverse temperature and pH conditions, and fertilizer doses ranging from 30 °C to 45 °C, 4 to 12 pH and 25 % to 100 % diammonium phosphate concentrations, respectively. Dual-stress condition of pH 9 at 45 °C resulted in 1.2-fold increase in EPS production by the strain as compared to non-stressed conditions. Strain IC3123 showed much better growth profile in EPS amended medium in comparison to EPS excluded medium under multi-stress conditions, suggesting the protective role of EPS in stress tolerance. Plant growth promoting traits of IC3123 were also monitored in presence and absence of EPS supplementation that further confirmed the effectiveness of EPS in mitigating stress and enhancing plant growth promoting traits. Diverse sets of bioformulations were prepared using purified EPS alone (metabolite-based bioformulation), blend of IC3123 and EPS (blended formulation), and rhizobia cells (IC3123) alone (cell-based formulation). Field experiment was conducted with pigeon pea in naturally stressed farmer’s field in Northern India where all these stress conditions (pH 8.9, 45 °C, 33 ppm NO₃–N) were found to act simultaneously in combination. The experiment was conducted in set of two: with and without 100 % recommended dose of fertilizer in the form of di-ammonium phosphate. Amongst the strategically developed bioformulations, the blend of cell plus metabolite significantly enhanced germination, pod number, seed yield, and protein content by 1.14, 1.38, 1.31 and 1.37-fold, respectively in comparison to untreated set (control). No nodulation was observed in the control set, whereas nodule number per plant increased when seeds received treatment with blend. Thus, the present study propagates the application of blended formulations developed from rhizobia and EPS for augmenting nodulation and growth of pigeon pea crop in stressed habitat in comparison to pure cell alone, with results validated in field.

25678. 题目: Mitigation of organophosphate pesticide pollution in agricultural watersheds
文章编号: N19122502
期刊: Science of The Total Environment
作者: Cagri Sahin, M. Ekrem Karpuzcu
更新时间: 2019-12-25
摘要: Adsorption and biodegradation processes for four organophosphate pesticides (chlorpyrifos, diazinon, fenthion, dichlorvos) in wetlands and agricultural drains in Meric-Ergene Basin, Turkey have been investigated. K_oc (organic carbon normalized partition coefficient) values for all pesticides except Diazinon were higher in more aromatic Pamuklu Drain sediments, indicating the possible influence of aromaticity on the extent of adsorption. The average half-lives of pesticides in Gala Lake sediments and Pamuklu agricultural drain sediments ranged from 2.25 to 69.31 days with chlorpyrifos exhibiting the slowest biotransformation rate and dichlorvos having the fastest biotransformation rate. The presence of humic substances and hydroperiod of wetlands have been identified as possible factors that affected the behavior of organophosphate pesticides in this study. The results from this study provide insight into the constructed wetland design offered for the mitigation of organophosphate pesticides in the basin.
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25679. 题目: Membrane fouling by alginate in polyaluminum chloride (PACl) coagulation/microfiltration process: Molecular insights
文章编号: N19122501
期刊: Separation and Purification Technology
作者: Jiaheng Teng, Yifeng Chen, Guangcai Ma, Huachang Hong, Tianyu Sun, Bao-Qiang Liao, Hongjun Lin
更新时间: 2019-12-25
摘要: While polyaluminum chloride (PACl) coagulation- microfiltration (MF) process is one of the most popular methods for surface water treatment, the fouling mechanism underlying this process has not well explored. In this study, sodium alginate (SA) was used as the model organic matter. It was interestingly found that, specific filtration resistance (SFR) of alginate-aluminum complexes initially increased to an ultra-high value of 1.40 × 10¹⁵ m⁻¹ kg⁻¹, and then sharply declined to rather low level of 3.85 × 10¹² m⁻¹ kg⁻¹ with the increase in PACl dosage from 0 to 500 mg/L. A series of characterizations of the foulant samples showed that the alginate-aluminum complexes suffered a morphology transition from gel form to floc/cake form with the PACl dosage increase. Density functional theory (DFT) calculation indicated the preferential coordination of aluminum ions with the terminal carboxyl groups of the alginate chains at low PACl level, facilitating homogeneous gel formation. The ultra-high SFR of gel was interpreted by the Flory-Huggins lattice theory. High PACl level resulted in the coordination of aluminum ions with the non-terminal carboxyl groups and reduced the surface charge, and thus, caused gel collapse and floc formation, corresponding to rather low SFR values. Preferential coordination combined with the Flory-Huggins lattice theory revealed in this study offered a molecular level fouling mechanism in the coagulation- microfiltration (MF) process for water treatment.
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25680. 题目: Groundwater carbon within a boreal catchment – spatiotemporal variability of a hidden aquatic carbon pool
文章编号: N19122405
期刊: Journal of Geophysical Research: Biogeosciences
作者: Anna C. Nydahl, Marcus B. Wallin, Hjalmar Laudon, Gesa A. Weyhenmeyer
更新时间: 2019-12-24
摘要: Groundwater is an essential resource providing water for societies and sustaining surface waters. Although groundwater at intermediate depth could be highly influential at regulating lake and river surface water chemistry, studies quantifying organic and inorganic carbon (C) species in intermediate depth groundwater are still rare. Here, we quantified dissolved and gaseous C species in the groundwater of a boreal catchment at 3 to 20 m depth. We found that the partial pressure of carbon dioxide (pCO₂), the stable carbon isotopic composition of dissolved inorganic carbon (δ¹³C‐DIC) and pH showed a dependency with depth. Along the depth profile, a negative relationship was observed between pCO₂ and δ¹³C‐DIC, and between pCO₂ and pH. We attribute the negative pCO₂‐pH relationship along the depth gradient to increased silicate weathering and decreased soil respiration. Silicate weathering consumes carbon dioxide (CO₂) and release base cations, leading to increased pH and decreased pCO₂. We observed a positive relationship between δ¹³C‐DIC and depth, potentially due to diffusion‐related fractionation in addition to isotopic discrimination during soil respiration. Soil CO₂ may diffuse downward, resulting in a fractionation of the δ¹³C‐DIC. Additionally, the dissolved organic carbon (DOC) at greater depth may be recalcitrant consisting of old degraded material with a greater fraction of the heavier C isotope. Our study provides increased knowledge about the C biogeochemistry of groundwater at intermediate depth, which is important since these waters likely contribute to the widespread CO₂ oversaturation in boreal surface waters.