12761. 题目: “Unraveling petroleum mixtures from the South Viking Graben, North Sea: A study based on δ13C of individual hydrocarbons and molecular data”
期刊: Organic Geochemistry
作者: Wendy A. Murillo, Brian Horsfield, Andrea Vieth-Hillebrand
摘要: Mixtures of compositionally different petroleum have been seen in the Norwegian North Sea, one of the world’s major oil-producing regions. The objective of this contribution is to appraise the source, maturity, in-reservoir mixing and alteration processes in a set of condensate and oil samples covering the main producing areas in the South Viking Graben (SVG). Furthermore, this study focuses on unraveling complex mixtures of petroleum and quantifying mixing ratios of hydrocarbons generated from Jurassic source rocks. The present research is based on a multiparameter approach that comprises the molecular composition of light hydrocarbons and heterocyclic and polycyclic aromatic compounds as well as the δ13C of individual hydrocarbons in oils, condensates and Upper and Middle Jurassic source rock extracts from the SVG. According to the relative contribution of oils from Type-III kerogen-rich source rocks, seven populations (A-G) of mixed petroleum are identified by combining source-related ratios of heterocyclic and non-heterocyclic aromatic hydrocarbons and δ13C values of n-alkanes, pristane (Pr) and phytane (Ph). The heterocyclic and polycyclic aromatic hydrocarbons provided a useful means of discriminating mixed hydrocarbons from source rocks of distinct organic matter type, depositional environment and lithology in the SVG. The 13C-enrichment of (C10-C14) n-alkanes and Pr and Ph were good indicators of the scale of the terrigenous source contribution and allowed the quantitative determination of the proportions of Jurassic source contributions enriched in Type-II and Type-III kerogens in complex petroleum mixtures from the southern part of the SVG.
12762. 题目: Physical and chemical processes determining soil organic matter dynamics in a managed vertisol in a tropical dryland area
期刊: Soil and Tillage Research
作者: Claudia Hidalgo, Agustín Merino, Victorino Osorio-Hernández, Jorge D. Etchevers, Benjamín Figueroa, Agustín Limon, Eduardo Aguirre
摘要: Vertisols are soils with a high potential for carbon (C) sequestration. However, these soils undergo swelling and shrinkage cycles, which exert a strong influence on soil organic matter (SOM) dynamics. The long-term effects of agricultural conservation practices on SOM content and stability on a Vertisol located in a tropical dryland area was evaluated.Two tillage systems (conventional tillage [CT], disc ploughing and extraction of 70% harvest residues, and no tillage [NT], incorporating 100% of the harvest residues) in combination with three different crop rotations (sorghum-soyabean [SrSy], maize-maize [MM] or soyabean-maize [SyM]) were tested. All plots were irrigated during dry periods. The effects on soil organic C, N, microbial biomass and aggregate size class distribution were evaluated. Carbon sink capacity were assessed by studying the aggregate-associated SOM content and quality (thermal recalcitrance), as determined by thermo-calorimetry.Relative to the CT system, NT yielded a higher percentage of small macroaggregates (2-0.25 mm). It also promoted the accumulation of aggregate-associated SOM, especially in the small macroaggregates and microaggregates. Thermal analysis revealed that the aggregate-associated SOM was more recalcitrant (higher values of T50 and more energy released at 475 °C) in NT than in CT. Coinciding with these effects, the soil microbial biomass/SOC ratio was lower in NT than in CT. The gain of SOM and the higher recalcitrance of OM in the NT soils may be related to different characteristics of NT Vertisols, such as poor aeration or disruption of the swelling and shrinkage cycles. The findings show that soil conservation practices increase the capacity for long-term C sequestration in Vertisols via organomineral interactions and SOM recalcitrance, which are determined by the formation of large cracks as a result of the swelling and shrinkage cycles that are some of the specific properties and processes of these soils.
12763. 题目: Investigation of (co)-combustion kinetics of biomass, coal and municipal solid wastes
期刊: Waste Management
作者: Imane Boumanchar, Younes Chhiti, Fatima Ezzahrae M'hamdi Alaoui, Mohamed Elkhouakhi, Abdelaziz Sahibed-dine, Fouad Bentiss, Charafeddine Jama, Mohammed Bensitel
摘要: Investigation of thermal behaviors of biomass waste, biochar, coal, municipal solid waste (MSW) and their mixtures were aimed in the present study using both thermogravimetric analysis and differential scanning calorimeter techniques. In fact, this paper intends to interpret the influence of mixtures on activation energy. In this purpose, Coats and Redfern were used. Then, the relative error Δmerror was calculated to quantify the synergism degree. Precisely, it was about 5.34% for biomass/coal, 5.52% for biomass/cardboard, 5.67% for biomass/biochar, 5.93% for biomass/synthetic rubber and 6.05% for biomass/plastic mixtures. This phenomenon was justified by the interaction between C-C bond of biochar, coal and MSW radicals with C-H and C-O bonds of biomass.
12764. 题目: Molecular change of dissolved organic matter and patterns of bacterial activity in a stream along a land-use gradient
期刊: Water Research
作者: Norbert Kamjunke, Norbert Hertkorn, Mourad Harir, Philippe Schmitt-Kopplin, Christian Griebler, Mario Brauns, Wolf von Tümpling, Markus Weitere, Peter Herzsprung
摘要: Fluvial networks are globally relevant for the processing of dissolved organic matter (DOM). To investigate the change in molecular DOM diversity along the river course, high-field FTICR mass spectrometry and NMR spectroscopy of riverine DOM as well as bacterial abundance and activity were measured in a third order stream along a land-use gradient from pristine, agricultural to urban landscapes. DOM composition showed a clear evolution along the river course with an initial decrease of average oxidation and unsaturation followed by an increased relative abundance of CHNO and CHOS compounds introduced by agriculture and waste water, respectively. DOM composition was dominated by rather unsaturated CHO compounds (H/C ≤ 1) in headwaters and by more aliphatic molecules at downstream sites. Oxygenated functional groups shifted from aromatic ethers and hydroxyl groups to aliphatic carboxylic acids and aliphatic hydroxyl groups. This massive dislocation of oxygen significantly increased the diversity of atomic environments in branched aliphatic groups from headwater to downstream DOM. Mass spectra of DOM enabled the detection of compositional relationships to bacterial abundance and activity which was positively related to more aliphatic components (H/C > 1) and negatively related to unsaturated components. FTICR mass and NMR spectra corroborated the initial decline in DOM molecular diversity predicted by the River Continuum Concept (RCC) but demonstrated an anthropogenic increase in the molecular diversity of DOM further downstream. While the high DOM molecular diversity in first order headwater streams was the result of small scale ecosystem plurality, agriculture and waste water treatment introduced many components in the lower reaches. These anthropogenic influences together with massive bacterial oxidation of DOM contributed to a growth of molecular diversity of downstream DOM whose composition and structure differed entirely from those found in pristine headwaters.
12765. 题目: Solar Irradiation Induced Transformation of Ferrihydrite in the Presence of Aqueous Fe 2+
期刊: Environmental Science & Technology
作者: Zhipeng Shu, Lihu Liu, Wen-Feng Tan, Steven L. Suib, Guohong Qiu, Xiong Yang, Lirong Zheng, Fan Liu
摘要: Ferrihydrite commonly occurs in soils and sediments, especially in acid mine drainage (AMD). Solar irradiation may affect Fe(II)-catalyzed transformation of metastable ferrihydrite to more stable iron oxides on AMD surface. We investigated the Fe(II)-catalyzed transformation process and mechanism of ferrihydrite under light irradiation. In nitrogen atmosphere, Fe2+aq could be oxidized to goethite and lepidocrocite by hydroxyl radical (OH•), superoxide radical (O2•–) and hole (hvb+) generated from ferrihydrite under ultraviolet (UV) irradiation (300–400 nm) at pH 6.0, and O2•– and hvb+ were mainly responsible for Fe2+aq oxidation. In addition, the ligand-to-metal charge-transfer (LMCT) process between Fe(II) and ferrihydrite could be promoted by UV irradiation. Goethite proportion increased with increasing Fe2+aq concentration. Both visible (vis) and solar irradiation could also lead to the oxidation of Fe2+aq to goethite and lepidocrocite, and the proportion of lepidocrocite increased with increasing light intensity. Fe2+aq was photochemically oxidized to schwertmannite at pH 3.0 and 4.5, and the oxidation rate was higher than that under dark conditions in air. The photochemical oxidation rate of Fe2+aq decreased in the presence of humic acid. This study facilitates a better understanding of the formation and transformation of iron oxides in natural environments and ancient Earth.
12766. 题目: Arctic Primary Aerosol Production Strongly Influenced by Riverine Organic Matter
期刊: Environmental Science & Technology
作者: Jiyeon Park, Manuel Dall’Osto, Kihong Park, Jung-Hyun Kim, Jongkwan Park, Ki-Tae Park, Chung Yeon Hwang, Gwang Il Jang, Yeontae Gim, Sujin Kang, Sanghun Park, Yong Keun Jin, Seong Soo Yum, Rafel Simó, Young Jun Yoon
摘要: The sources of primary and secondary aerosols in the Arctic are still poorly known. A number of surface seawater samples—with varying degrees of Arctic riverine and sea ice influences—were used in a sea spray generation chamber to test them for their potential to produce sea spray aerosols (SSA) and cloud condensation nuclei (CCN). Our interdisciplinary data showed that both sea salt and organic matter (OM) significantly influenced the SSA production. The number concentration of SSA in the coastal samples was negatively correlated with salinity and positively correlated with a number of OM tracers, including dissolved and chromophoric organic carbon (DOC, CDOM), marine microgels and chlorophyll a (Chl-a) but not for viral and bacterial abundances; indicating that OM of riverine origin enhances primary aerosol production. When all samples were considered, transparent exopolymer particles (TEP) were found to be the best indicator correlating positively with the ratio number concentration of SSA/salinity. CCN efficiency was not observed to differ between the SSA from the various samples, despite differences in organic characteristics. It is suggested that the large amount of freshwater from river runoff have a substantial impact on primary aerosols production mechanisms, possibly affecting the cloud radiative forcing.
12767. 题目: Recent advancement in lignin biorefinery: with special focus on enzymatic degradation and valorization
期刊: Bioresource Technology
作者: Chong Li, Chao Chen, Xiaofen Wu, Chi-Wing Tsang, Jinhua Mou, Jianbin Yan, Yun Liu, Carol Sze Ki Lin
摘要: With the intensive development of lignocellulosic biorefineries to produce fuels and chemicals from biomass-derived carbohydrates, lignin was generated at a large quantity every year. Therefore, lignin has received increasing attention as an abundant aromatics resource in terms of research and development efforts for value-added chemicals production. In this review, studies about lignin degradation especially the crucial enzymes involved and the reaction mechanism were substantially discussed, which provided the molecular basis of lignin biodegradation. Then, the latest improvements in lignin valorization by biological methods were summarized and case studies about value-added compounds from lignin were introduced. Afterwards, challenges, opportunities and prospects regarding biorefinery of lignin were presented.
12768. 题目: Microstructure, bacterial community and metabolic prediction of multi-species biofilms following exposure to di-(2-ethylhexyl) phthalate (DEHP)
作者: Yi Li, Peisheng Zhang, Longfei Wang, Chao Wang, Wenlong Zhang, Huanjun Zhang, Lihua Niu, Peifang Wang, Minhui Cai, Wentao Li
摘要: The occurrence and transportation of phthalate esters in biofilms from natural and engineered sources have attracted considerable research interest. However, little information is available highlighting the responses of multi-species biofilms in terms of their physicochemical structure and bacterial community induced by phthalate esters. Di-(2-ethylhexyl) phthalate (DEHP), a model phthalate eater, was selected to treat multi-species biofilm aggregates, including an attached biofilm from a moving bed bioreactor (MBBR), a periphytic biofilm from a natural source and activated sludge in short-term exposure experiments (120 h). The production of extracellular polymeric substances (EPS) from the three biofilms initially decreased and then slightly increased after exposure to DEHP, consistent with the variation of the most dominant fluorescent compounds consisting of humic-acid–like organic substances. The MBBR and periphytic biofilms secreted more fluorescence compounds than the activated sludge during the exposure period. The organic matter in the EPS was converted into smaller molecules, while limited variation was observed in the functional groups and secondary protein structures. Acinetobacter and Bacillus demonstrated significant increases and were likely the key genera responsible for DEHP degradation. The combined use of spectral, chromatographic and sequencing analyses indicated that the periphytic biofilm was more resistant to DEHP, possibly owing to the presence of more mature assemblages, including cells with higher metabolic activity and a higher diversity within the bacterial community. This study provides insights into the microstructural and bacterial responses of multi-species biofilms following exposure to phthalate esters, and provides important guidance for bioremediation of phthalate esters using periphytic biofilms.
12769. 题目: Investigating the effect of biochar on the potential of increasing cotton yield, potassium efficiency and soil environment
期刊: Ecotoxicology and Environmental Safety
作者: Xiuwen Wu, Dian Wang, Muhammad Riaz, Lin Zhang, Cuncang Jiang
摘要: Potassium (K) is an essential macronutrient for plant growth and development. However, in China, available K is relatively low in the soil, and with the extensive use of chemical fertilizer, K use efficiency is constantly reducing, and consequently increasing the potential risk of environmental pollution and economic loss. Therefore, it is essential to reduce the negative impact of over-fertilization on the environment to obtain optimal crop yield. Biochar as a soil amendment has been applied to improve soil fertility and increase crop yield. However, the effects of successive biochar application on cotton yield, agronomy efficiencies and potash fertilizer reduction are not well documented. Our results of a pot experiment showed that the application of 1% biochar to soil under different K levels significantly improved dry mass accumulation and K content of different plant parts, and increased the number of buds, bolls and effective branches of cotton. Particularly, plants treated with 150 mg/kg K2O and 1% biochar had the highest growth parameters. The most important characteristics including the harvest index, K fertilizer contribution index, partial factor productivity, agronomic efficiency and apparent recovery efficiency of K under C1 (1% biochar) were generally greater than those under C0 (without biochar). The 75 mg/kg K2O application was optimal to produce the highest yield with 1% biochar, demonstrating that biochar can increase cotton yield and therefore, reduces chemical K fertilizer application and alleviates agricultural environment risks of chemical fertilizer.
12770. 题目: Modification of forward osmosis membrane with naturally-available humic acid: Towards simultaneously improved filtration performance and antifouling properties
期刊: Environment International
作者: Yan-Fang Guan, Bao-Cheng Huang, Yun-Jie Wang, Bo Gong, Xinglin Lu, Han-Qing Yu
摘要: In this work, a thin-film composite forward osmosis (FO) membrane was fabricated on polyethersulfone substrate by interfacial polymerization with naturally-available humic acid (HA) as a stable membrane additive in the support layer. Compared with the pristine polyethersulfone substrate, the incorporation of HA significantly altered the cross-section structure, increased average pore size and porosity of the substrate, leading to a thinner polyamide layer, further increasing the water flux (permeability). Specifically, the FO membrane showed a higher water flux (~20 L m−2 h−1) with the introduction of HA than the membrane synthesized without HA (~15 L m−2 h−1) in the FO mode with 2 M NaCl as draw solution. Moreover, the selectivity of the membrane was improved ~45% by dosing 0.8 wt% HA into the substrate, in comparation to the pristine membrane without HA doped. Besides, the average roughness of the polyamide layer was reduced by up to 68% when HA was present in the substrate, which mitigated the fouling potential. Thus, a slower flux decline ratio (~60%) was observed for the membrane modified with 0.8 wt% HA than the pristine membrane (~80%). Taken together, our findings shed light on using natural-available HA for effectively and efficiently modifying membrane substrate to simultaneously enhance the permeate-selectivity performance and the anti-fouling behavior in FO membrane process. The fundamental causes of these differences in membrane separation performance and fouling behavior are considered and related to the physical and chemical characteristics of support layer (i.e., porosity and pore size) and polyamide layer (i.e., active layer thickness and roughness) of membranes.
12771. 题目: Significant nitrate attenuation in a mangrove-fringed estuary during a flood-chase experiment
期刊: Environmental Pollution
作者: Praktan D. Wadnerkar, Isaac R. Santos, Arun Looman, Christian J. Sanders, Shane White, James P. Tucker, Ceylena Holloway
摘要: Intertidal wetlands can sequester pollutants along estuarine conduits. Here we test the effectiveness of a mangrove-dominated estuary in removing dissolved nitrogen during a rain event. We intensively and simultaneously sampled surface water nutrients upstream and downstream of an estuary before, during and after a 63 mm rain event in Coffs Creek (Australia). NOx was the main form of dissolved nitrogen upstream of the estuary (∼60%), while dissolved organic nitrogen (DON) was an important form at the downstream station (∼46%) during observations. High NOx attenuation (71%) occurred during the rain event when the loads reached 31 μmol m−2 catchment area day−1. In contrast, the estuary was found to be a source of NH4+ (∼5 μmol m−2 catchment area day−1). This implies a moderate conversion of upstream NOx into NH4+ and DON along the transport pathway, likely due to tidally-driven pore water exchange within the anoxic estuarine mangrove sediments. Overall, the mangrove-lined estuary attenuated upstream total dissolved nitrogen loads, maintaining water quality and minimizing exports to the coastal ocean even during high flow conditions.
12772. 题目: Organic matter input determines structure development and aggregate formation in artificial soils
作者: Franziska B. Bucka, Angelika Kölbl, Daniel Uteau, Stephan Peth, Ingrid Kögel-Knabner
摘要: The formation of aggregates is considered to happen by clustering and cohesion of mineral particles and organic matter. Up to now, little is known about the role of different organic matter types within this process. We developed an experimental set-up to study the influence of organic carbon (OC) derived from particulate organic matter (POM-C) and from dissolved organic matter (DOM-C) for aggregate formation under controlled laboratory conditions. We designed artificial soil microcosms with loamy texture, mimicking an arable Cambisol, and performed an incubation for 30 days under constant water tension. The microcosms received either POM-C as milled hay litter, DOM-C as solution derived from hay or no additional OC input. We characterized the developed soil matrix by analysing aggregate size distribution and composition as well as the associated pore system.After incubation, we observed the formation of mostly large, water-stable macroaggregates (630–3000 μm) in all treatments with OC addition. POM-C input led to an increase in mass contribution of the large macroaggregates from 6% to 88 ± 6%, when compared to the original particle size distribution, while DOM-C input led to an increase to 59 ± 9%. The size fractions of the small microaggregates and primary particles (<63 μm) were present in a mass contribution of 11 ± 5% for the POM-C addition and 35 ± 7% for the DOM-C addition. The small microaggregates had a predominant size of 2–20 μm. The OC distribution was closely linked to the aggregate size distribution, indicating a functional link concerning the aggregate forming process. In POM-C microcosms, 95% of the OC present after incubation was stored in large macroaggregates. In DOM-C microcosms, the OC was bimodally distributed between large macroaggregates (59 ± 0.8%) and small microaggregates (33 ± 0.4%). CO2 release was highest with DOM-C input, indicating that approximately 41% of the organic matter input was mineralized. High-resolution μCT scanning was used on subsample cores to investigate 3D pore structure differences. POM-C microcosms had a decreased macroporosity (>50 μm pore size) and highly connected pores (Euler number change from −1519 to −5767) after incubation. This indicates a reorganization of the pore space towards a fine, connected pore system with improved gas, water and nutrient exchange and thus implications for the microbial microenvironment. DOM-C microcosms also had an increased pore connectivity (Euler number change from −122 to −665) after incubation, but overall values were smaller than in the POM-C microcosms, indicating that changes in pore structure depend on OM type initiating aggregation.We demonstrate that aggregate formation in a loamy textured artificial soil is possible within 30 days and can take place in the absence of physical interference like stirring or repeated wet-dry cycles. Different organic matter types induce specific formation of aggregates and associated pore system as the effect of microbial decomposition of the OC input and the interaction of OC compounds with mineral surfaces.
12773. 题目: An investigation of changes in water quality throughout the drinking water production/distribution chain using toxicological and fluorescence analyses
期刊: Journal of Environmental Sciences
作者: Xue Han, Xin Ji, Xuan Ma, Jun-Ling Liu, Zhen-Yu He, Wei Chang, Fei Tang, Ai-Lin Liu
摘要: Changes in water quality from source water to finished water and tap water at two conventional drinking water treatment plants (DWTPs) were monitored. Beside the routine water quality testing, Caenorhabditis elegans-based toxicity assays and the fluorescence excitation–emission matrices technique were also applied. Both DWTPs supplied drinking water that met government standards. Under current test conditions, both the investigated finished water and tap water samples exhibited stronger lethal, genotoxic and reprotoxic potential than the relative source water sample, and the tap water sample was more lethal but tended to be less genotoxic than the corresponding finished water sample. Meanwhile, the nearly complete removal of tryptophan-like substances and newly generated tyrosine-like substances were observed after the treatment of drinking water, and humic-like substances were identified in the tap water. Based on these findings, toxic pollutants, including genotoxic/reproductive toxicants, are produced in the drinking water treatment and/or distribution processes. Moreover, further studies are needed to clarify the potentially important roles of tyrosine-like and humic-like substances in mediating drinking water toxicity and to identify the potential sources of these contaminants. Additionally, tryptophan-like fluorescence may be adopted as a useful parameter to monitor the treatment performance of DWTPs. Our observations provided insights into the importance of utilizing biotoxicity assays and fluorescence spectroscopy as tools to complement the routine evaluation of drinking water.
12774. 题目: Weakened adhesion force between extracellular polymeric substances of waste activated sludge caused by rhamnolipid leading to more efficient carbon release
期刊: Science of The Total Environment
作者: Jiaqi Li, Wenzong Liu, Ruiyun Ren, Dechun Xu, Chengyan Liu, Bo Wang, Aijie Wang
摘要: Rhamnolipid (RL), a biosurfactant produced by bacteria, is investigated to alter the physical characteristics of extracellular polymeric substance (EPS) of waste-activated sludge (WAS), and subsequently promotes hydrolysis and acidogenesis during anaerobic digestion for short chain fatty acids (SCFAs) production. The results revealed that RL could decrease the adhesion force of EPS from 13.46 nN to 1.08 nN, resulting in EPS disintegration layer by layer, decreasing the median particle size by 31.57 μm and releasing abundant soluble organic matter. The cell number of living bacteria remained stable after RL pretreatment (2.59 × 109 vs. 2.66 × 109), indicating that RL has a minimal impact on microbial cells (only ~2% bacterial lysis was observed). The kinetic studies of ammonia nitrogen release and SCFA production suggested that, in the RL-pretreated WAS, the reaction rate constants for hydrolysis and acidogenesis were respectively 2-fold and 1.5-fold higher than those of the control group.
12775. 题目: Meso/micropore-controlled hierarchical porous carbon derived from activated biochar as a high-performance adsorbent for copper removal
期刊: Science of The Total Environment
作者: Dinh Viet Cuong, Nei-Ling Liu, Viet Anh Nguyen, Chia-Hung Hou
摘要: High-quality meso/micropore-controlled hierarchical porous carbon (HPC) was synthesized by a hard template method utilizing rice husk biochar and then used to adsorb copper ions from an aqueous solution. The preparation procedure included two main steps: base leaching and physicochemical activation. During the activation process, the porosity characteristics (i.e., specific surface area and meso/micropore ratio) were controlled by altering the KOH impregnation ratio, activation time, and temperature under the CO2 atmosphere. In addition, a copper adsorption study was performed using three HPC samples with different pore structures and characteristics. The results of this study indicate that the adsorption capacity of HPC material derived from rice husk biochar is strongly influenced by its meso/micropore ratio. As evidenced, HPC 3-0.5-800, which was impregnated by a KOH:biochar ratio of 3 and activated at 800 °C for 0.5 h under a CO2 atmosphere, has a very high specific surface area of 2330 m2 g−1 with an 81% mesopore to total specific surface area. Importantly, it exhibited a superior adsorption capacity of 265 mg g−1 and rapid adsorption kinetics for copper ions. The improvement is ascribed to the high specific surface area and favorable hierarchical structure. The findings demonstrate the feasibility of controlling the hierarchical pore structure of rice husk biochar-derived carbons as high-performance adsorbents for copper ion removal from water.
12776. 题目: Spatial differentiation of cultivated soils using compound-specific stable isotopes (CSSIs) in a temperate agricultural watershed in Manitoba, Canada
期刊: Journal of Soils and Sediments
作者: Dominic G. Reiffarth, Ellen L. Petticrew, Philip N. Owens, David A. Lobb
摘要: Purpose: Compound-specific stable isotopes (CSSIs) of very long-chain fatty acids (VLCFAs) of plant origin were investigated in a soil and sediment tracing context in a watershed in Manitoba, Canada. Spatial and temporal variability in δ13CFA values and concentrations was examined at the point, transect, and field scales to determine the (1) ability to differentiate sediment sources in C3-cropped fields, (2) impact of subsampling on source tracer fingerprints, and (3) major sediment source for a downstream mixture using the Bayesian unmixing model MixSIAR. Materials and methods: Analysis was performed for five agricultural fields over six sampling periods. Soil and sediment samples (320) were processed for VLCFA analyses (C20:0–C30:0, C32:0). Quantification was performed by gas chromatography–flame ionization detection (GC-FID) and 13C determination by GC combustion–isotope ratio mass spectrometry (GCC-IRMS). Data were analyzed using weighted t tests to differentiate fields by δ13CFA values. The major sediment source was determined using the following steps: (1) a point-in-polygon approach to identify VLCFA tracers; (2) unmixing using MixSIAR; (3) source apportioning using VLCFA concentrations and %C. Results and discussion: VLCFA δ13CFA values vary spatially within a cropped field due to environmental factors. Sediment source fingerprints are dependent on the variability in δ13CFA values and the quantitative combining of subsamples. Cropped fields that appeared homogeneous exhibited a large range in δ13CFA values, with variability greatest for fall and spring samples; concentrations were lowest at these times. Historical field boundaries played a role. A downstream sediment mixture (June 2013) was analyzed and found to correspond with source data from August 2012. Sediment mixture data (δ13CFA) for several VLCFAs were found to fall within the source mixing polygons produced by using two cultivated fields and a riparian zone sample as sources. Conclusions: Variability in δ13CFA values increased in fall and spring, which could affect the number of subsamples required per source. Most fields could be spatially differentiated using a weighted t test, but not necessarily using the same VLCFA chain lengths. Two spatially separated fields with similar cropping histories were difficult to differentiate, but one of the fields was more prone to VLCFA losses. Only one of several source sampling periods led to successful unmixing, suggesting multiple sampling periods for source and/or mixture are necessary. Understanding the spatial and temporal variability affecting δ13CFA values in source sediments is particularly important for tracing studies using biomarkers in producing a representative fingerprint.
12777. 题目: Increased microbial growth, biomass and turnover drive soil organic carbon accumulation at higher plant diversity
期刊: Global Change Biology
作者: Judith Prommer, Tom W. N. Walker, Wolfgang Wanek, Judith Braun, David Zezula, Yuntao Hu, Florian Hofhansl, Andreas Richter
摘要: Species‐rich plant communities have been shown to be more productive and to exhibit increased long‐term soil organic carbon (SOC) storage. Soil microorganisms are central to the conversion of plant organic matter into SOC, yet the relationship between plant diversity, soil microbial growth, turnover as well as carbon use efficiency (CUE) and SOC accumulation is unknown. As heterotrophic soil microbes are primarily carbon limited, it is important to understand how they respond to increased plant‐derived carbon inputs at higher plant species richness (PSR). We used the long‐term grassland biodiversity experiment in Jena, Germany, to examine how microbial physiology responds to changes in plant diversity and how this affects SOC content. The Jena Experiment considers different numbers of species (1‐60), functional groups (1‐4) as well as functional identity (small herbs, tall herbs, grasses and legumes). We found that plant species richness (PSR) accelerated microbial growth and turnover and increased microbial biomass and necromass. Plant species richness also accelerated microbial respiration, but this effect was less strong than for microbial growth. In contrast, PSR did not affect microbial CUE or biomass‐specific respiration. Structural equation models (SEMs) revealed that PSR had direct positive effects on root biomass, and thereby on microbial growth and microbial biomass carbon. Finally, PSR increased SOC content via its positive influence on microbial biomass carbon.
12778. 题目: Functionalized biochar/clay composites for reducing the bioavailable fraction of arsenic and cadmium in river sediment
期刊: Environmental Toxicology and Chemistry
作者: Xiaohua Wang, Yanling Gu, Xiaofei Tan, Yunguo Liu, Yahui Zhou, Xinjiang Hu, XiaoXi Cai, Weihua Xu, Chen Zhang, Shaoheng Liu
摘要: Biochar has been frequently applied for the treatment of heavy metals pollution in water and soil, its effect in contaminated sediments needs further research. In order to improve the ability of biochar for heavy metals immobilization in sediment, this study prepared functionalized biochar/attapulgite composite by pyrolysis of the clay attapulgite and zinc chloride pretreated rice straw biomass. Compared with the original biochar, biochar/attapulgite composite had a large increase in specific surface area, pore volume, oxygen‐containing functional groups and cation exchange capacity. Biochar could effectively improve the dispersibility of attapulgite as a matrix. The results showed that the biochar/attapulgite composite could effectively reduce the bioavailable fraction of As and Cd in the river sediment, which had a great improvement compared with the raw biochar. After the sediment was treated by different biochar/attapulgite composites, the concentrations of As and Cd in the overlying water and pore water, and the content of acid extractable and TCLP extractable As and Cd in solid phase of sediment decreased significantly. Both zinc chloride activation and attapulgite were benefit for As and Cd immobilization in sediment by biochar/attapulgite composite. The results suggested that biochar/attapulgite composite can be used as an efficient in‐situ sorbent amendments to improve the immobilization ability of the sediment to heavy metals.
12779. 题目: Photovoltaic electrolysis improves nitrogen and phosphorus removals of biochar-amended constructed wetlands
期刊: Ecological Engineering
作者: Yan Gao, Cheng Yan, Ruping Wei, Wen Zhang, Jianing Shen, Mingxuan Wang, Bin Gao, Yicheng Yang, Liuyan Yang
摘要: To deeply remove nitrogen (N) and phosphorus (P) from constructed wetlands (CWs), the authors found that CWs can be combined with the use of photovoltaic energy for best results. Thus, electrolysis-integrated, biochar-amended, horizontal (subsurface)-flow-constructed wetlands (E-BHFCWs) were combined with free-water, surface-constructed wetlands (FWSCWs) to remove N and P from secondary effluent water of a wastewater treatment plant (WWTP). Photovoltaic energy was used for electrolysis to intensify the removal of nitrate nitrogen (NO3−-N), ammonium nitrogen (NH3-N), and phosphate phosphorus (PO43−-P) in E-BHFCWs. In addition, FWSCWs were constructed to further remove NO3−-N, NH3-N, PO43−-P and iron ions in effluent of E-BHFCWs and to enhance DO concentration. For the E-BHFCWs combined with FWSCWs, the removal rates of NO3−-N, NH3-N, and PO43−-P were 73.28%, 53.11% and 67.58% respectively. The removal amounts of NO3−-N, NH3-N, and PO43−-P were about 211.08 kg N/a, 64.81 kg N/a and 10.46 kg P/a by E-BHFCWs. Photovoltaic electrolysis in E-BHFCWs was able to enhance NO3−-N removal through electrochemical reduction by iron cathodes, enriched hydrogenotrophic bacteria in the substrate, and by modified biochar substrate in situ with iron ions. Meanwhile, NH3-N was mainly removed by modified biochar adsorption, nitrifying microbes, and plant uptake. The removal rate of PO43−-P was also enhanced due to the formation of ferric ions by the anodization of sacrificial iron anodes, causing chemical precipitation, physical adsorption, and flocculation of PO43−-P. Thus, E-BHFCWs combined with FWSCWs are capable of effectively promoting removals of NO3−-N, NH3-N, and PO43−–P and provide a new insight into a new energy flow that can enhance N and P removals of CWs.
12780. 题目: Impacts of carbonization temperature on the Pb(II) adsorption by wheat straw-derived biochar and related mechanism
期刊: Science of The Total Environment
作者: Yaoyao Cao, Guanghui Shen, Yang Zhang, Chongfeng Gao, Yanfei Li, Peizhen Zhang, Weihua Xiao, Lujia Han
摘要: To determine the quantitative correlations between physicochemical characteristics and Pb(II) adsorption amounts of biochar fractions, we prepared wheat straw-derived biochar under various carbonization temperatures (300–900 °C). The different fractions of the wheat straw-derived biochar, water-soluble material (WM), acid-soluble material (AM), and organic material (OM), were acquired. The ash content, ultimate analysis, pH, ion strength (IS), cation exchange capacity (CEC), and acidic functional groups (AFG) were characterized. The Pb(II) adsorption amounts of different biochars and their fractions were determined. The results revealed that the proportions of biochar fractions (WM, AM, and OM) varied with various carbonization temperatures. The maximum Pb(II) adsorption amount of wheat straw-derived biochar (qTotal) was 157.95 ± 0.13 mg/g obtained at 800 °C, and the quantitative correlations between Pb(II) adsorption amount (q) and carbonization temperature (T) can be elaborated by qTotal = 170.72–336.62exp(−0.0035T) (R2 = 0.97), qWM = 106.18–390.10exp(−0.0046T) (R2 = 0.98), qAM = 496.16–477.74exp(−0.0001T) (R2 = 0.79), and qOM = 1.80 + 34.69exp(−0.0038T) (R2 = 0.85). For rate of contribution (RC) for Pb(II) adsorption, when T < 400 °C, the order was AM (60.72 ± 7.33%) > OM (23.41 ± 7.33%) > WM (15.87 ± 0.30%); however, when T ≥ 400 °C, the order was WM (52.31 ± 0.85% - 67.65 ± 2.99%) > AM (29.65 ± 0.46% - 35.77 ± 0.12%) > OM (2.30 ± 0.47% - 12.02 ± 2.43%). Moreover, qWM and qAM exhibited significant positive linear correlations with ash (qWM = 9.92Ash - 123.65, and qAM = 2.13Ash - 0.49), qTotal was predominantly affected by ash content (qTotal = 10.97 Ash - 95.49). The EDX, XRD, and FTIR analysis results further clarified that ion exchange and precipitation were the main adsorption mechanisms for Pb(II) adsorption by wheat straw-derived biochar.