7001. 题目: Advanced Molecular Techniques Provide New Rigorous Tools for Characterizing Organic Matter Quality in Complex Systems
期刊: Journal of Geophysical Research: Biogeosciences
作者: Rachel M.Wilson, Malak M.Tfaily
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.
7002. 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
期刊: Organic Geochemistry
作者: Andrea Jaeschke, Janet Rethemeyer, Michael Lappé, Stefan Schouten, Pascal Boeckx, Enno Schefu?
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.
7003. 题目: Reactions of Ferrate(VI) with Iodide and Hypoiodous Acid: Kinetics, Pathways, and Implications for the Fate of Iodine during Water Treatment
期刊: Environmental Science & Technology
作者: Jaedon Shin, Urs von Gunten, David A. Reckhow, Sebastien Allard, and Yunho Lee
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.
7004. 题目: Sorption of lead ions onto oxidized bagasse-biochar mitigates Pb-induced oxidative stress on hydroponically grown chicory: Experimental observations and mechanisms
作者: Mostafa F. El-Banna, Ahmed Mosa, Bin Gao, Xianqiang Yin, Zahoor Ahmad, Hongyu Wang
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.
7005. 题目: Microbial decomposition processes and vulnerable Arctic soil organic carbon in the 21st century
作者: Junrong Zha and Qianlai Zhuang
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.
7006. 题目: Role of drinking water biofilms on residual chlorine decay and trihalomethane formation: An experimental and modeling study
期刊: Science of The Total Environment
作者: Jianeng Xu, Conghui Huang, Xiaoyang Shi, Shengkun Dong, Baoling Yuan, Thanh H. Nguyen
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.
7007. 题目: Stabilization of Ag–Au Bimetallic Nanocrystals in Aquatic Environments Mediated by Dissolved Organic Matter: A Mechanistic Perspective
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
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.
7008. 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
期刊: Environmental Science and Pollution Research
作者: Jianan Yu, Zhiliang Zhu, Hua Zhang, Yanling Qiu, Daqiang Yin
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.
7009. 题目: Biotic responses buffer warming‐induced soil organic carbon loss in Arctic tundra
期刊: Global Change Biology
作者: Junyi Liang, Jiangyang Xia, Zheng Shi, Lifen Jiang, Shuang Ma, Xingjie Lu, Marguerite Mauritz, Susan M. Natali, Elaine Pegoraro, Christopher Ryan Penton, César Plaza, Verity G. Salmon, Gerardo Celis, James R. Cole, Konstantinos T. Konstantinidis, James M. Tiedje, Jizhong Zhou, Edward A. G. Schuur, Yiqi Luo
摘要: Climate warming can result in both abiotic (e.g., permafrost thaw) and biotic (e.g., microbial functional genes) changes in Arctic tundra. Recent research has incorporated dynamic permafrost thaw in Earth system models (ESMs) and indicates that Arctic tundra could be a significant future carbon (C) source due to the enhanced decomposition of thawed deep soil C. However, warming‐induced biotic changes may influence biologically related parameters and the consequent projections in ESMs. How model parameters associated with biotic responses will change under warming and to what extent these changes affect projected C budgets have not been carefully examined. In this study, we synthesized six data sets over 5 years from a soil warming experiment at the Eight Mile Lake, Alaska, into the Terrestrial ECOsystem (TECO) model with a probabilistic inversion approach. The TECO model used multiple soil layers to track dynamics of thawed soil under different treatments. Our results show that warming increased light use efficiency of vegetation photosynthesis but decreased baseline (i.e., environment‐corrected) turnover rates of SOC in both the fast and slow pools in comparison with those under control. Moreover, the parameter changes generally amplified over time, suggesting processes of gradual physiological acclimation and functional gene shifts of both plants and microbes. The TECO model predicted that field warming from 2009 to 2013 resulted in cumulative C losses of 224 or 87 g/m2, respectively, without or with changes in those parameters. Thus, warming‐induced parameter changes reduced predicted soil C loss by 61%. Our study suggests that it is critical to incorporate biotic changes in ESMs to improve the model performance in predicting C dynamics in permafrost regions.
7010. 题目: Production Temperature Effects on the Structure of Hydrochar-Derived Dissolved Organic Matter and Associated Toxicity
期刊: Environmental Science & Technology
作者: Shilai Hao, Xiangdong Zhu, Yuchen Liu, Feng Qian, Zhi Fang, Quan Shi , Shicheng Zhang, Jianmin Chen, Zhiyong Jason Ren
摘要: Hydrochar is a carbonaceous material derived from hydrothermal liquefaction, and it carries good potential as a new material for environmental applications. However, little is known about the dissolved organic matter (DOM) associated with hydrochar and the consequences of its release. The relationship between the production temperature and the characteristics of DOM released from hydrochar as well as the associated biotoxicity was investigated using a suite of advanced molecular and spectroscopic tools. With the increase in production temperature, the resulted hydrochar-based DOM contained a higher content of phenols and organic acids but less sugars and furans. Meanwhile, the molecular structure of DOM shifted to lower molecular weight with higher organic contents containing <6 O atoms per compound, aromatics, and N-containing substances. While low-temperature hydrochar-derived DOM showed minimal biotoxicity, increase in production temperature to 330 °C led to a great rise in toxicity. This might be attributed to the increased contents of phenols, organic acids, and organics containing <6 O atoms and 1 N atom per compound. These results suggest that hydrochar-derived DOM have more negative impacts on the environment than the organics associated with biochar production. Such understanding highlights the importance of controlling the hydrochar production process.
7011. 题目: Relationships between waste physicochemical properties, microbial activity and vegetation at coal ash and sludge disposal sites
期刊: Science of The Total Environment
作者: Marcin W. Woch, Magdalena Radwańska, Ma?gorzata Stanek, Barbara ?opata, Anna M. Stefanowicz
摘要: The aim of the study was to assess the relationships between vegetation, physicochemical and microbial properties of substrate at coal ash and sludge disposal sites. The study was performed on 32 plots classified into 7 categories: dried ash sedimentation ponds, dominated by a grass Calamagrostis epigejos (AH-Ce), with the admixture of Pinus sylvestris (AH-CePs) or Robinia pseudoacacia (AH-CeRp), dry ash landfill dominated by Betula pendula and Pinus sylvestris (AD-BpPs) or Salix viminalis (AD-Sv) and coal sludge pond with drier parts dominated by Tussilago farfara (CS-Tf) and the wetter ones by Cyperus flavescens (CS-Cf). Ash sites were covered with soil layer imported as a part of technical reclamation. Ash had relatively high concentrations of some alkali and alkaline earth metals, Mn and pH, while coal sludge had high water and C, S, P and K contents. Concentrations of heavy metals were lower than allowable limits in all substrate types. Microbial biomass and, particularly, enzymatic activity in ash and sludge were generally low. The only exception were CS-Tf plots characterized by the highest microbial biomass, presumably due to large deposits of organic matter that became available for aerobic microbial biomass when water level fell. The properties of ash and sludge adversely affected microbial biomass and enzymatic activity as indicated by significant negative correlations between the content of alkali/alkaline earth metals, heavy metals, and macronutrients with enzymatic activity and/or microbial biomass, as well as positive correlations of these parameters with metabolic quotient (qCO2). Plant species richness and cover were relatively high, which may be partly associated with alleviating influence of soil covering the ash. The effect of the admixture of R. pseudoacacia or P. sylvestris to stands dominated by C. epigejos was smaller than expected. The former species increased NNH4, NNO3 and arylsulfatase activity, while the latter reduced activity of the enzyme.
7012. 题目: Interaction between copper and extracellular nucleic acids in the EPS of unsaturated Pseudomonas putida CZ1 biofilm
期刊: Environmental Science and Pollution Research
作者: Huirong Lin, Chengyun Wang, Hongmei Zhao, Guangcun Chen, Xincai Chen
摘要: The role of extracellular DNA (eDNA) in biofilm in heavy metal complexation has been little reported. In this study, the interaction between the extracellular fraction of unsaturated biofilms and Cu2+ was studied using random amplified polymorphic DNA (RAPD) and synchrotron-based X-ray absorption spectroscopy (XAS) analyses. Under Cu2+ stress, the amount of eDNA was about 10-fold higher than the treatment without Cu2+ stress, which was substantially more than the amount of intracellular DNA (iDNA) present in the biofilm. The eDNA content increased significantly under Cu2+ stress and higher eDNA contents were found in colloidal extracellular polymeric substances (EPS) than in capsular EPS in Luria-Bertani medium. It was found that the composition of eDNA was distinctly changed under conditions of Cu2+ stress compared with the treatments without Cu2+ treatments, with specific eDNA bands appearing under Cu2+ treatments as revealed by RAPD analyses. X-ray absorption fine structure (XAFS) analysis assessing the molecular speciation of copper showed that copper in the secreted eDNA mainly existed as species resembling Cu3(PO4)2, followed by Cu-citrate species. This study investigated the interaction between copper and eDNA in unsaturated Pseudomonas putida CZ1 biofilms. Potential function of eDNA in biofilms under Cu2+ stress was found.
7013. 题目: Phytoavailability, bioaccumulation, and human health risks of metal(loid) elements in an agroecosystem near a lead-zinc mine
期刊: Environmental Science and Pollution Research
作者: Liqiang Luo, Yating Shen, Xiaofang Wang, Binbin Chu, Tao Xu, Ying Liu, Yuan Zeng, Jian Liu
摘要: Soil near a Pb-Zn-Mn mine was polluted by mining, which may have an impact on human health via the food chain. To evaluate the pollution effects, arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), manganese (Mn), lead (Pb), and zinc (Zn) in vegetables were determined by inductively coupled plasma atomic emission and mass spectrometry. Lead species were analyzed by X-ray absorption near-edge structure (XANES). Phytoavailability of the elements was evaluated by bioaccumulation of the elements, the sequential extraction procedure, Pb species, and plant uptakes. The target health quotient (THQ) was calculated to evaluate the human health risks. It was found that (1) high concentrations of As, Cd, Cr, and Pb were detectable in vegetables, and bioaccumulation was in the order of Mn > Zn > Cr > Pb > Cu > As > Cd; (2) phytoavailability of the elements was controlled mainly by the soluble fraction, and a linear relationship observed between the soluble fraction and bioaccumulation; (3) a new Pb-fulvic acid complex (Pb-FA) was identified by XANES in rhizosphere soil, and high content of Pb organic matter (60%) and soluble Pb (18%) were found; (4) both Cd and Zn accumulated in both of the Amaranthaceae and the Apiaceae families, indicating that the plants in the same family have the same bioaccumulation trend for the elements in the same group; (5) agricultural activities and plant growing increased phytoavailability of As, Cd, Cu, Pb, and Zn by decreasing the residual and raising the soluble and extractable fractions; (6) arsenic is top of the high health risks, followed by Pb, Cd, and Mn. Coriander, celery, and spinach were the top three highest health risks in the area.
7014. 题目: Cation exchange capacity of biochar: An urgent method modification
期刊: Science of The Total Environment
作者: J.L. Munera-Echeverri, V. Martinsen, L.T. Strand, V. Zivanovic, G. Cornelissen, J. Mulder
摘要: Biochar, produced through pyrolysis of organic matter, is negatively charged, thus contributing to electrostatic adsorption of cations. However, due to its porous structure and contents of alkaline ashes, the determination of the cation exchange capacity (CEC) is challenging. Literature values for the CEC of biochar are surprisingly variable and are often poorly reproducible, suggesting methodological problems. Here, we modify and critically assess different steps in the existing ammonium acetate (NH4OAc) method (pH 7), where ammonium (NH4 +) is displaced by potassium chloride (KCl), following removal of excess NH4OAc with isopropanol, in batch mode. We used pigeon pea biochar to develop the method and conducted a test on three additional biochars with different acid neutralizing capacity. A pretreatment step of biochar was introduced, using diluted hydrochloric acid, to decrease biochar pH to near neutral, so that 1 M NH4OAc effectively buffers the biochar suspension pH at 7. This allows the CEC of all biochars to be determined at pH 7, which is crucial for biochar comparison. The dissolution of ashes may cause relatively large weight losses (e.g. for cacao shell biochar), which need to be accounted for when computing the CEC of raw biochar. The sum of NH4OAC-extractable base cations provided a smaller and better estimate of the CEC than KCl-extractable NH4 +. We hypothesize that the overestimation of the CEC based on KCl-extractable NH4 + is due to the ineffectiveness of the relatively large isopropanol molecules to remove excess NH4OAc in biochars rich in micro-pores, due to size exclusion. The amount of base cations removed in the pretreatment was about three (rice husk biochar) to ten times (pigeon pea biochar) greater than the amount of exchangeable cations. The CEC values of biochar increased from 10.8 cmol/Kg carbon to 119.6 cmol/Kg carbon. These values are smaller than reported CEC values of soil organic carbon.
7015. 题目: Temporal effects of post-fire check dam construction on soil functionality in SE Spain
期刊: Science of The Total Environment
作者: J. González-Romero, M.E. Lucas-Borja, P.A. Plaza-?lvarez, J. Sagra, D. Moya, J. De Las Heras
摘要: Wildfire has historically been an alteration factor in Mediterranean basins. Despite Mediterranean ecosystems' high resilience, wildfire accelerates erosion and degradation processes, and also affects soil functionality by affecting nutrient cycles and soil structure. In semi-arid Mediterranean basins, check dams are usually built in gullies and channels after fire as a measure against soil erosion. Although check dams have proven efficient action to reduce erosion rates, studies about how they affect soil functionality are lacking. Our approach focuses on how soil functionality, defined as a combination of physico-chemical and biological indicators, is locally affected by check dam construction and the evolution of this effect over time. Soils were sampled in eight check dams in two semi-arid areas at SE Spain, which were affected by wildfire in 2012 and 2016. The study findings reveal that by altering sediments cycle and transport, check dams influence soil's main physico-chemical and biochemical characteristics. Significant differences were found between check dam-affected zones and the control ones for many indicators such as organic matter content, electrical conductivity or enzymatic activity. According to the ANOVA results, interaction between check dams influence and time after fire, was a crucial factor. PCA results clearly showed check-dams influence on soil functionality.
7016. 题目: Oriented acidification of wasted activated sludge (WAS) focused on odd-carbon volatile fatty acid (VFA): Regulation strategy and microbial community dynamics
期刊: Water Research
作者: Long Huang, Zhiqiang Chen, Dandan Xiong, Qinxue Wen, Ye Ji
摘要: As the main intermediate metabolite in anaerobic digestion of wasted activated sludge (WAS), volatile fatty acids (VFAs) are proper substrate for mixed culture (MC) polyhydroxyalkanoate (PHA) synthesis. To further optimize the performance of MC PHA production process, VFA_odd (i.e., VFA with odd carbon atoms) oriented acidification process was proposed and conducted in this study. Three regulation factors including reaction pH, fraction of added β-cyclodextrin (β-CD) and glycerol were selected and response surface methodology (RSM) was used to enhance and effectively regulate the VFA_odd production while maintaining enough acidification degree in the WAS acidification. High percentage of VFA_odd (larger than 60% and dominated by propionic acid) can be obtained in the operating condition area with glycerol addition ratio (quantified by C/N) ranging from 15 to 20 and reaction pH ranging from 8.0 to 9.5 when β-CD addition was held at zero level (0.2 g/gTSS) according to the RSM. Semi-continuous acidification and MC PHA production assays further verified the reliability and effectiveness of the VFA_odd oriented acidification strategy. Microbial function group related to propionic acid production (Gprop) was defined based on the relationships between system function and microbial community structure, and 13 frequent species were found being involved in the Gprop. Roles of the group members in the oriented acidification were analyzed to understand the mechanisms of the regulation of VFA_odd production at microbial ecological level. A synergistic effect of WAS and glycerol on the VFA_odd production in the acidification process was revealed based on the ecological analysis.
7017. 题目: Multiple linear regression models to predict the formation efficiency of triplet excited states of dissolved organic mat...
期刊: Limnology and Oceanography
作者: Andrew J. McCabe, William A. Arnold
摘要: The source and composition of dissolved organic matter (DOM) dictates light absorption in surface waters. Sunlight absorption by chromophoric dissolved organic matter (CDOM) forms reactive intermediates and drives global organic carbon processing. Triplet excited states of CDOM (3CDOM*) are primary reactive intermediates formed by sunlight absorption by CDOM. 3CDOM* also produce secondary reactive intermediates, including radicals and reactive oxygen species, which are active in biogeochemical pathways. The efficiency of 3CDOM* formation (apparent quantum yield, AQYT) depends on DOM composition, especially DOM molecular weight. This dependence may arise from the greater probability of forming intra‐molecular charge‐transfer (CT) complexes in high‐molecular weight DOM that inhibit 3CDOM* formation. There are few examples that demonstrate this in field samples. In this report, vegetation, general hydrology, and watershed characteristics for 39 temperate wetlands, which are critical sources of high‐molecular weight DOM, from the United States were defined and related to DOM composition and AQYT. The DOM bulk composition was assessed using absorbance and fluorescence spectroscopies. AQYT was estimated under simulated sunlight using the probe 2,4,6‐trimethylphenol. Relatively high AQYT values (7%) were observed in wetlands with long hydroperiods and > 50% cropland watershed land cover compared to wetlands with >50% forest watershed land cover (< 1–4%). Low molecular weight DOM (E2/E3 > 7 and SUVA254 < 3 L mg‐C-1m-1) and autochthonous DOM (β/α > 0.7) had relatively high AQYT estimates ( 10%), indicating that allocthonous, high‐molecular weight compounds produce 3CDOM* less efficiently than autochthonous DOM. The CT theory of DOM light absorption and internal light‐screening offer mechanistic explanations for these trends.
7018. 题目: A comparative analysis for the development and recovery processes of different types of clogging in lab-scale vertical flow constructed wetlands
期刊: Environmental Science and Pollution Research
作者: Yongchao Zhou, Shan Luo, Bohai Yu, Tuqiao Zhang, Jin Li, Yiping Zhang
摘要: Clogging is a major operational and maintenance issue associated with the use of constructed wetlands. In this study, four lab-scale vertical flow constructed wetlands (VFCW) were used to fully understand the development mechanisms of various types of clogging and their recovery characteristics. The VFCWs were fed with glucose solution, starch suspension with and without bacteriostat, glucose, and starch mixed solution, respectively, to simulate Bio-clogging, organic particle clogging (Op-clogging), inert particle clogging (Ip-clogging), and the combination of Bio-clogging and Op-clogging (C-clogging). Resting operations with water decline were applied to relieve the clogging in the VFCWs. The results indicate that Op-clogging occurred first, followed by C-clogging and Bio-clogging. Ip-clogging took the longest time to develop and did not occur by the end of this study. The microscope analysis found that the extracellular polymeric substances (EPS) bonded the starch particles together to form a dense membrane-like structure and promoted the clogging process. In addition, surface clogging was observed in all four experimental beds. Op-clogging occurred much closer to the surface than those caused by soluble organic matter and inert particles. Furthermore, the growth of biofilm caused significant decline in hydraulic conductivity, whereas its influence on porosity was relatively slight. Moreover, applying resting operation with water decline was effective for recovery from Bio-clogging, Op-clogging, and C-clogging in VFCWs except for Ip-clogging. The results also implied the recovery rates through applying resting operation with water decline were much higher than that with constant water level.
7019. 题目: A new look at the multi-G model for organic carbon degradation in surface marine sediments for coupled benthic–pelagic s...
作者: Konstantin Stolpovsky, Andrew W. Dale, and Klaus Wallmann
摘要: The kinetics of particulate organic carbon (POC) mineralization in marine surface sediments is not well constrained. This creates considerable uncertainties when benthic processes are considered in global biogeochemical or Earth system circulation models to simulate climate–ocean interactions and biogeochemical tracer distributions in the ocean. In an attempt to improve our understanding of the rate and depth distribution of organic carbon mineralization in bioturbated (0–20 cm) sediments at the global scale, we parameterized a 1-D diagenetic model that simulates the mineralization of three discrete POC pools (a “multi-G” model). The rate constants of the three reactive classes (highly reactive, reactive, refractory) are fixed and determined to be 70, 0.5 and 0.001 yr-1, respectively, based on the Martin curve model for pelagic POC degradation. In contrast to previous approaches, however, the reactivity of the organic material degraded in the seafloor is continuous with, and set by, the apparent reactivity of material sinking through the water column. Despite the simplifications of describing POC remineralization using G-type approaches, the model is able to simulate a global database (185 stations) of benthic oxygen and nitrate fluxes across the sediment–water interface in addition to porewater oxygen and nitrate distributions and organic carbon burial efficiencies. It is further consistent with degradation experiments using fresh phytoplankton reported in a previous study. We propose that an important yet mostly overlooked consideration in upscaling approaches is the proportion of the reactive POC classes reaching the seafloor in addition to their reactivity. The approach presented is applicable to both steady-state and non-steady state scenarios, and links POC degradation kinetics in sedimentary environments to water depth and the POC rain rate to the seafloor.
7020. 题目: A uniform bacterial growth potential assay for different water types
期刊: Water Research
作者: Nadia Farhat, Frederik Hammes, Emmanuelle Prest, Johannes Vrouwenvelder
摘要: The bacterial growth potential is important to understand and manage bacterial regrowth-related water quality concerns. Bacterial growth potential depends on growth promoting/limiting compounds, therefore, nutrient availability is the key factor governing bacterial growth potential. Selecting proper tools for bacterial growth measurement is essential for routine implementation of the growth potential measurement. This study proposes a growth potential assay that is universal and can be used for different water types and soil extract without restrictions of pure culture or cultivability of the bacterial strain. The proposed assay measures the sample bacterial growth potential by using the indigenous community as inocula. Flow cytometry (FCM) and adenosine tri-phosphate (ATP) were used to evaluate the growth potential of six different microbial communities indigenous to the sample being analyzed, with increasing carbon concentrations. Bottled mineral water, non-chlorinated tap water, seawater, river water, wastewater effluent and a soil organic carbon extract were analyzed. Results showed that indigenous bacterial communities followed normal batch growth kinetics when grown on naturally present organic carbon. Indigenous bacterial growth could detect spiked organic carbon concentrations as low as 10 μg/L. The indigenous community in all samples responded proportionally to the increase in acetate-carbon and proportional growth could be measured with both FCM and ATP. Bacterial growth was proportional to the carbon concentration but not the same proportion factor for the different water samples tested. The effect of inoculating the same water with different indigenous microbial communities on the growth potential was also examined. The FCM results showed that the highest increase in total bacterial cell concentration was obtained with bacteria indigenous to the water sample. The growth potential assay using indigenous bacterial community revealed consistent results of bacterial growth in all the different samples tested and therefore providing a fast, more stable, and accurate approach for monitoring the biological stability of waters compared to the previously developed assays. The growth potential assay can be used to aid in detecting growth limitations by compounds other than organic carbon.