161. 题目: Microwave directional pyrolysis and heat transfer mechanisms based on multiphysics field stimulation: Design porous biochar structure via controlling hotspots formation
期刊: Chemical Engineering Journal
作者: Junhao Lin, Shichang Sun, Donghua Xu, Chongwei Cui, Rui Ma, Juan Luo, Lin Fang, Haowen Li
摘要: The microwave pyrolysis of biomass and the directional design of biochar structure are examined in this study by exploring the internal connection between energy conversion and biochar structure evolution. Through the optimization of process parameters (microwave power and sample volume), the average utilization efficiency of microwave energy increased from 11.96% to 32.84%, and the specific surface area of the biochar increased from 453.89 m2/g to 638.82 m2/g. According to the simulation results of the COMSOL Multiphysics software, the distribution of the temperature field was closely related to the evolution of the microwave electric field intensity. The local high temperature areas (hotspots) were primarily located in the center of the biochar, and the temperature distribution gradually decreased from the inside to the outside. The hotspots contributed to the promotion of the conversion of amorphous carbon to graphite carbon. Meanwhile, the graphite carbon with a stronger microwave absorption capacity formed a local hotspot and promoted the growth of the pore structure. The rich pore structure of the biochar facilitated the multiple reflection of microwave energy and prolonged the microwave residence time. Graphite carbon can absorb microwave energy and convert it into heat energy to improve the utilization efficiency of microwave energy. This paper combined the experimental and simulation results to reveal the heat transfer mechanism in the microwave pyrolysis process, which provided a new perspective for the directional reduction of microwave pyrolysis energy consumption and the optimization of the microstructure of biochar.
162. 题目: Zirconium hydroxide nanoparticle encapsulated magnetic biochar composite derived from rice residue: Application for As(III) and As(V) polluted water purification
期刊: Journal of Hazardous Materials
作者: Yaru Peng, Muhammad Azeem, Ronghua Li, Libin Xing, Yimeng Li, Yichen Zhang, Zhiqiang Guo, Quan Wang, Huu Hao Ngo, Guangzhou Qu, Zengqiang Zhang
摘要: Finding a low-cost and suitable adsorbent is still in urgent need for efficient decontamination of As(III) and As(V) elements from the polluted waters. A novel zirconium hydroxide nanoparticle encapsulated magnetic biochar composite (ZBC) derived from rice residue was synthesized for the adsorptive capture of As(III) and As(V) from aqueous solutions. The results revealed that ZBC showed an acceptable magnet separation ability and its surface was encapsulated with lots of hydrous zirconium oxide nanoparticles. Compared to As(III), the adsorption of As(V) onto ZBC was mainly dependent on the pH of the solution. The intraparticle diffusion model described the adsorption process. ZBC showed satisfactory adsorption performances to As(III) and As(V) with the highest adsorption quantity of 107.6mg/g and 40.8mg/g at pH 6.5 and 8.5, respectively. The adsorption of As(III) and As(V) on ZBC was almost impervious with the ionic strength while the presence of coexisting ions, especially phosphate, significantly affected the adsorption process. The processes of complexation reaction and electrostatic attraction contributed to the adsorption of As(III) and As(V) onto ZBC. ZBC prepared from kitchen rice residue was found to be a low cost environmentally friendly promising adsorbent with high removal capacity for As(III) and As(V) and could be recycled easily from contaminated waters.
163. 题目: Bacterial abundance and community structure in response to nutrients and photodegraded terrestrial humic acids in a eutrophic lake
期刊: Environmental Science and Pollution Research
作者: En Hu, Longgang Hu, Yu Zheng, Yuxin Wu, Xifeng Wang, Changshun Sun, Yaling Su
摘要: The exposure of humic substances to solar radiation can alter their concentration and composition and subsequently influences their bioavailability in aquatic food webs. With eutrophication increasingly prominent in lakes, nutrients, such as inorganic N and P, are a prerequisite for heterotrophic bacteria that use organic matter. Here photodegradation of terrestrial humic acids and nutrient addition were performed to investigate the response of bacterial abundance and community structure to photodegraded humic acids and increased nutrient concentrations in a eutrophic lake. Results showed that the decreasing level of absorption coefficient at 460 nm in the treatment irradiated with 40 W UV lamps was more remarkable than that of the treatment irradiated with 20 W UV lamps and the control. This reduced coefficient corresponds to the greatest decrease in humic acid concentration in the 40 W group. Bacteria showed high abundance after incubation with humic acids which underwent strong irradiation intensity. An increased nutrient concentration significantly affected bacterial abundance. The dominant bacteria were Aquabacterium for the irradiated group, Aquabacterium and Limnobacter for the 20 W group and Flavobacterium and Limnobacter for the 40 W group. Armatimonadetes-gp4 and Sediminibacterium showed evident response to high nutrient concentration. Our results showed that the exposure of terrestrial humic acids to UV light and the increasing concentration of nutrients have obviously changed bacterial community.
164. 题目: Contrasting sources and fate of nitrogen compounds in different groundwater systems in the Central Yangtze River Basin
期刊: Environmental Pollution
作者: Yaojin Xiong, Yao Du, Yamin Deng, Teng Ma, Dian Li, Xiaoliang Sun, Guangning Liu, Yanxin Wang
摘要: Although groundwater nitrogen pollution has been widely studied, the control of hydrogeological conditions on behavior of nitrogen compounds has been poorly understood. In this study, multiple stable isotopes (N/C/H/O), spectral characteristics of DOM coupled with water chemistry were used to reveal the sources and fate of nitrate and ammonium in three subareas with different hydrogeological conditions in the Central Yangtze River Basin. We identified three contrasting patterns of nitrogen sources and fate in groundwater controlled by different aquifer features. In a reducing porous aquifer mainly composed of carbonate minerals overlain by a thick low-permeability layer, the NH4–N concentration is high (mean 4.12 mg/L) but with quite low NO3–N concentration (mean 0.28 mg/L). The high ammonium is mainly from intense degradation of organic matter (OM), while denitrification at a higher rate results in nitrate removal. Feammox may be favored owing to abundant humics acting as the electron shuttle. In a weakly reducing to oxidizing porous aquifer mainly composed of aluminosilicate minerals overlain by a varying thickness of low-permeability layer, high ammonium occurs in a weakly reducing condition and is affected by both anthropogenic input and OM degradation, while high nitrate occurs in a more oxidizing condition and could be mainly from soil nitrogen, manure or sewage. Feammox may be also favored due to more acidic environment formed by weathering of aluminosilicate minerals, fluctuating redox condition and low abundance of labile organic carbon, while denitrification occurs at a slower rate coupled with concurrent re-oxidation of nitrite to nitrate. In an oxidizing porous - fissured aquifer system overlain by a thin low-permeability layer, the concentrations of ammonium and nitrate are both low, possibly due to strong hydrodynamic and flushing condition, although slightly higher concentration of nitrate exhibit similar sources and fate with the weakly reducing to oxidizing porous aquifer mentioned above.
165. 题目: Reconstruction of palaeoenvironment and ancient human activities at Obrovac-type settlements (Serbia) using a geochemical approach
期刊: Quaternary International
作者: Gorica Veselinović, Boban Tripković, Nevena Antić, Aleksandra Šajnović, Milica Kašanin-Grubin, Tomislav Tosti, Kristina Penezić
摘要: This study aims to determine the palaeoenvironmental characteristics and activity patterns of Obrovac-type archaeological sites in Western Serbia, dated to the Late Neolithic/Early Eneolithic period, ∼5th millennium BC. These mound-like sites, enclosed by a wide ditch, that are not known in other parts of the central Balkan area, have long intrigued archaeologists investigating their origin and function over the last few decades. In this study, for the first time, organic-geochemical analysis of paleosol samples from the Obrovac-type sites was applied with the aim of palaeoenvironmental reconstruction. Additionally, organic carbon content and anion analysis of 58 subsoil samples from these settlements were performed to determine the use of space and activity zones. The analysis of biomarkers from selected sites suggests significant plant biodiversity in the Mačva region during the Late Neolithic/Early Eneolithic. Distribution of n-alkanes with the maximum at n-C25 and predominance of C30 hop-22(29)-ene among hopanoids in samples from Obrovac type-sites indisputably indicates that macrophytes are a dominant source of organic matter, implying a marshy and floodplain depositional environment. On the other side, a strong signal of long-chain n-alkanes indicates the input of terrestrial plants into the precursor biomass, confirming that this environment was habitable for the first settlers in this region. Anion-based analysis delineates certain activity zones, demonstrating that Obrovac type-sites manifest rather complex spatial behavior despite their relatively small size and available space.
166. 题目: Performance and microbial community dynamics during rice straw composting using urea or protein hydrolysate as a nitrogen source: A comparative study
期刊: Waste Management
作者: Xiao-Xing Li, Shi-Peng Wang, Zhao-Yong Sun, Song-Tao Wang, Wen-Liang Shuai, Cai-Hong Shen, Yue-Qin Tang
摘要: Aerobic composting is a promising alternative for the recycling of rice straw (RS), and an applicable nitrogen source is necessary to improve the process. The aim of this study was to compare the performance and microbial community dynamics of RS composting using urea or protein hydrolysate from leather waste (PHL) as a nitrogen source. Results showed that PHL addition achieved a faster temperature increase rate at start-up (1.85 ℃·h−1 vs 1.07 ℃·h−1), higher volatile solid degradation efficiency (48.04% vs 46.98%), and greater germination indices (111.72% vs 89.87%) in the end products, as compared to urea. The major bacterial phyla included Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria in both composting processes. Although the bacterial communities in both processes succeeded in a similar pattern according to different composting phases, PHL addition accelerated the succession rate of the microbial community. Co-occurrence network analysis revealed that bacterial community composition was strongly correlated with physicochemical properties such as dissolved organic carbon (DOC), NH4+, pH, temperature, and total nitrogen (TN) content. These results proved the potential of using PHL as a nitrogen source to improve the RS composting process.
167. 题目: Size-Dependent Response of the Reductive Reactivity of Zerovalent Iron toward the Coexistence of Natural Organic Matter
期刊: ACS ES&T Engineering
作者: Jia-Qi Chen, Guannan Zhou, Chuan-Shu He, Qi Li, Yi-Ran Wang, Yang Mu
摘要: Although the existence of ubiquitous natural organic matter (NOM) exerts significant effects on the performance of zerovalent iron (ZVI), size-dependent response of the reactivity of ZVI toward NOM under both aerobic and anaerobic conditions has not been considered. In this study, the oxic removal and anoxic removal of the pollutant diatrizoate (DTA) by mechanochemically prepared ZVI of varying sizes in the presence of humic acid (HA), a typical NOM, were investigated comparatively. When oxygen was present, the effect of HA on DTA degradation transformed from promotion to inhibition as the particle size of ZVI decreased from microscale (mZVI) to nanoscale (nZVI). By contrast, in the absence of oxygen, HA always suppressed DTA removal regardless of ZVI size. Under aerobic conditions, HA complexed with Fe(III) (hydr)oxides and then detached from the mZVI surface, leading to the depassivation effect and promotion of atomic hydrogen (H*), while HA and HA–Fe(III) complexes coated the surface of nZVI with a relatively smaller size and suppressed the formation of H*. Under anaerobic conditions, adsorbed HA and associated HA–Fe(II) complexes covered the surfaces of mZVI and nZVI to different extents, resulting in the occupation of active sites and inhibiting generation of H*. This study provides an in-depth insight into the interaction between ZVI and NOM and may serve as theoretical guidance for the application of ZVI-based technologies.
168. 题目: Culture-dependent study of arsenic-reducing bacteria in deep aquatic sediments of Bengal Delta
期刊: Environmental Science and Pollution Research
作者: Chinmay Bandopadhyay, Sanjib Kumar Manna, Srikanta Samanta, Atalanta Narayan Chowdhury, Nilanjan Maitra, Bimal Prasanna Mohanty, Keka Sarkar, Samir Kumar Mukherjee
摘要: Biogeochemical release of soil-bound arsenic (As) governs mobilization of the toxic metalloid into the groundwater. The present study has examined AsV-reduction ability of bacteria from anoxic aquatic sediments that might contribute to arsenic mobilization in the Bengal Delta. Arsenic-reducing bacteria from deep layers of pond sediment were enriched and isolated in anaerobic environments and AsV reduction was assessed in culture medium. The pond sediment enrichments harboured AsV-reducing bacteria belonging to the phyla Firmicutes and Proteobacteria with dominance of Paraclostridium benzoelyticum and P. bifermentans. Among total 17 isolates, the respiratory reductase genes were not detected by the most common primers and only 3 strains had arsenic reductase ArsC gene suggesting involvement of resistance and some unknown mechanisms in AsV reduction. Presence of high levels of organic matter, As, and As-reducing bacteria might make deep aquatic sediments a hot spot of As mobilization and aquifer contamination.
169. 题目: Development of food-origin biochars for the adsorption of selected volatile organic compounds (VOCs) for environmental matrices
期刊: Bioresource Technology
作者: Kyriaki Kaikiti, Marinos Stylianou, Agapios Agapiou
摘要: Four novel fruit-derived biochars were developed: pomegranate peels (PB), prickly pear peels (PPB), carob (CB), and locust bean gum (LBGB). The feedstocks were pyrolyzed at 350 and 550 ℃ (under N2), respectively, and characterized using Scanning Electron Microscopy (SEM), Elemental Analysis (EA), Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), Brunauer–Emmett–Teller (B.E.T) analysis, and Thermogravimetric analysis (TGA). A systematic and comprehensive comparison for the adsorption of selected volatile organic compounds (VOCs) by biochar was established. Cresol, dimethyl trisulfide (DMTS), hexane, and benzene were examined as a function of contact time (30-480 min), mass (0.1-1 g), concentration levels (50-1000 ppbv), efficiency, and reusability using the headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS) method. PB 550 ℃ revealed a specific surface area of 8.3 m2 g-1, the fastest complete removal, an ideal mass of 1 g, 3-times repeatability, and ∼99% removal of 500 ppbv benzene, cresol, DMTS, and 100 ppbv hexane.
170. 题目: Bimetallic oxides with package structure for enhanced degradation of bisphenol A through peroxymonosulfate activation
期刊: Chemical Engineering Journal
作者: Jiabin Dan, Qiongfang Wang, Pinhua Rao, Lei Dong, Min Zhang, Xin Zhang, Zedi He, Naiyun Gao, Jing Deng
摘要: Cobalt oxide (CoO) could activate peroxymonosulfate (PMS) to remove pollutants but the catalytic performance was restricted by limited active sites and it was with risk of harmful cobalt ion leaching. In order to solve these problems, bimetallic oxides with package structure were researched by dispersing CoO nanoparticles on a stable support (magnesium oxide, MgO) via simple one-step coprecipitation method. Co-Mg bimetallic oxides with minute quantities of CoO and highly dispersed structure could efficiently activate PMS for degradation of bisphenol A (BPA). The catalytic properties of catalysts with different molar ratios of Co and Mg were evaluated. The optimal molar ratio (0.075:15) of Co and Mg was found in the Co-Mg bimetallic oxides, which could maximize its catalytic performance for PMS in a wide pH range. Influences of different systems, catalyst dosages, PMS concentrations, temperatures, initial pH values and mineralization rates were researched for BPA degradation. And the oxidation capacities to remove BPA in the different aqueous matrices were evaluated for the catalyst/PMS system. The addition of anions and nature organic matter (NOM) showed that there existed positive (Cl- and H2PO4-) and negative (NO3-, HCO3-, HPO42- and NOM) effects for BPA degradation. Additionally, main reactive radicals were certified by quenching experiments. Four successive experiments and evaluation of concentration of cobalt ion leaching illustrated good stability of the catalyst, which was related with its package structure. Finally, activation mechanism of PMS, proposed degradation pathways of BPA and acute toxicity of degradation intermediates of BPA were analyzed.
171. 题目: Highly efficient removal of Cr(VI) from aqueous solution by pinecone biochar supported nanoscale zero-valent iron coupling with Shewanella oneidensis MR-1
作者: Liying Ma, Yaguang Du, Shaohua Chen, Dongyun Du, Hengpeng Ye, Tian C. Zhang
摘要: Nanoscale zero-valent iron (nZVI) has been extensively used to remove various pollutants. However, the rapid deactivation due to aggregation and surface passivation severely limits its practical application. In this study, a novel composite with nZVI supported by pinecone biochar (nZVI-PBC) was successfully synthesized and used for the removal of high concentration Cr(VI) from aqueous solution in the presence of Shewanella oneidensis MR-1 (MR-1). The results showed that the nZVI-PBC coupling with MR-1 (nZVI-PBC/MR-1) exhibited an excellent removal performance for high concentration Cr(VI) compared to the nZVI-PBC alone. Under optimal conditions, 100 mg/L Cr(VI) could be removed completely by nZVI-PBC/MR-1 within 48 h, while only 39.50% of Cr(VI) was removed by nZVI-PBC alone. The improvement of Cr(VI) removal is due to the dissolution of the surface passivation layer of nZVI-PBC, formation of sorbed Fe(II) in the presence of MR-1, and an important role of extracellular polymeric substance (EPS) derived from MR-1. X-ray photoelectron spectroscopy (XPS) and Cr K-edge X-ray absorption near-edge structure spectra (XANES) confirmed that most Cr(VI) was reduced to insoluble Cr(III) and formed Cr2O3, CrxFe1-x(OH)3 and FeCr2O4 precipitates, and a small amount of unreduced Cr(VI) was immobilized through adsorption and complexation. The results suggest that nZVI-PBC/MR-1 can effectively overcome the limitations of nZVI and achieve highly efficient removal of high concentration Cr(VI).
172. 题目: Adsorption mechanism of two pesticides on polyethylene and polypropylene microplastics: DFT calculations and particle size effects
期刊: Environmental Pollution
作者: Qiming Mo, Xingjian Yang, Jinjin Wang, Huijuan Xu, Wenyan Li, Qi Fan, Shuang Gao, Wenyi Yang, Chengzhen Gao, Dehua Liao, Yongtao Li, Yulong Zhang
摘要: Polyethylene (PE) and polypropylene (PP) microplastics (MPs), as carriers, can bind with pesticides, which propose harmful impacts to aqueous ecosystems. Meanwhile, carbofuran and carbendazim (CBD), two widely used carbamate pesticides, are toxic to humans because of the inhibition of acetylcholinesterase activity. The interaction between two MPs and two pesticides could start in farmland and be maintained during transportation to the ocean. Herein, the adsorption behavior and mechanism of carbofuran and carbendazim (CBD) by PE and PP MPs were investigated via characterization and density functional theory (DFT) simulation. The adsorption kinetic and thermodynamic data were best described by pseudo-second-order kinetics and the Freundlich models. The adsorption behaviors of individual carbofuran/CBD on both MPs were very similar. The CBD adsorption rate and capacity of PE and PP MPs were higher than those of carbofuran. This phenomenon explained the lower negative effects of DOM (oxalic acid, glycine (Gly)) on CBD adsorption relative to those of carbofuran. The presence of oxalic acid and Gly decreased the PE adsorption by 20.40–48.02% and the PP adsorption by 19.27–42.11%, respectively. It indicated the significance of DOM in carbofuran cycling. The adsorption capacities were negatively correlated with MPs size, indicating the importance of specific surficial area. Fourier transformation infrared spectroscopy before and after adsorption suggested that the adsorption process did not produce any new covalent bond. Instead, intermolecular van der Waals forces were one of the primary adsorption mechanisms of carbofuran and CBD by MPs, as evidenced by DFT calculations. Based on the zeta potential, the electrostatic interaction explained the higher adsorption CBD by MPs than carbofuran.
173. 题目: Diel dynamics of dissolved organic matter and heterotrophic prokaryotes reveal enhanced growth at the ocean's mesopelagic fish layer during daytime
期刊: Science of The Total Environment
作者: Xosé Anxelu G. Morán, Francisca C. García, Anders Røstad, Luis Silva, Najwa Al-Otaibi, Xabier Irigoien, Maria L. Calleja
摘要: Contrary to epipelagic waters, where biogeochemical processes closely follow the light and dark periods, little is known about diel cycles in the ocean's mesopelagic realm. Here, we monitored the dynamics of dissolved organic matter (DOM) and planktonic heterotrophic prokaryotes every 2 h for one day at 0 and 550 m (a depth occupied by vertically migrating fishes during light hours) in oligotrophic waters of the central Red Sea. We additionally performed predator-free seawater incubations of samples collected from the same site both at midnight and at noon. Comparable in situ variability in microbial biomass and dissolved organic carbon concentration suggests a diel supply of fresh DOM in both layers. The presence of fishes in the mesopelagic zone during daytime likely promoted a sustained, longer growth of larger prokaryotic cells. The specific growth rates were consistently higher in the noon experiments from both depths (surface: 0.34 vs. 0.18 d-1, mesopelagic: 0.16 vs. 0.09 d-1). Heterotrophic prokaryotes in the mesopelagic layer were also more efficient at converting extant DOM into new biomass. These results suggest that the ocean's twilight zone receives a consistent diurnal supply of labile DOM from diel vertical migrating fishes, enabling an unexpectedly active community of heterotrophic prokaryotes.
174. 题目: How water connectivity and substrate supply shape the turnover of organic matter – Insights from simulations at the scale of microaggregates
作者: Simon Zech, Thomas Ritschel, Nadja Ray, Kai Uwe Totsche, Alexander Prechtel
摘要: Microaggregates are hot spots of microbial activity at a scale that frequently poses a severe experimental challenge or defies a direct observation. Mathematical models that combine the mechanisms of spatially resolved organic matter transport with the processes of organic matter turnover can facilitate the understanding of soil microbial dynamics and the function of soils at these scales. In this study, we investigate microbial population dynamics and the turnover of particulate organic matter (POM) in soil microaggregates. CT images of microaggregates obtained from samples of natural soils serve as basis for selecting the simulation domain. For different levels of water saturation, the fluid (liquid and gas) distribution within the pore space is calculated according to a morphological model. We consider bacteria and POM, which are heterogeneously distributed within the liquid phase. Dissolved organic carbon (DOC) is released by hydrolyzing POM, assuming a reaction following first-order kinetics. DOC spreads by diffusion and can subsequently be consumed by bacteria and turned into CO2. The growth of bacteria is realized by a cellular automaton framework (CAM) and based on Michaelis–Menten kinetics due to the uptake of DOC. Our simulations show that the heterogeneous distribution of substrate and bacteria results in an overall biodegradation kinetics and CO2 output that strongly depends on the microaggregate scale (<250μm). Only very specific cases can be distinguished globally, e.g., when the substrates are isolated from bacteria due to a disconnected liquid phase. Locally, however, heterogeneities in substrate distribution impact the development of bacteria populations, e.g., a smaller geodesic distance of bacteria to the substrate promotes bacterial growth locally.
175. 题目: Effect of biochar aging on the adsorption and stabilization of Pb in soil
期刊: Journal of Soils and Sediments
作者: Dandan Chen, Wenhui Liu, Yuxuan Wang, Ping Lu
摘要: Purpose Biochar is used for the stabilization of Pb in soil because of its abundant surface functional groups and excellent pore structure. However, little is known about the long-term performance of biochars. This study aims to evaluate the effect of biochar aging on the adsorption and stabilization of Pb in soil and to provide theoretical guidance for long-term utilization of biochar. Materials and methods A modified BCR continuous extraction procedure was performed to analyze the effects of three aging methods (natural, freeze–thaw, and high-temperature aging), four biochar species (wheat straw, corn straw, peanut shell, and pine chips chars), and aging time (7, 60, and 150 days) on the chemical fractions of Pb in soil. FTIR, XRD, and BET were used to analyze surface functional groups, composition, and pore structure of biochars, respectively. Results and discussion The effects of three aging methods on the stabilization of Pb in soil were ordered as high-temperature aging (HT) ≈ freeze–thaw aging (FT) > natural aging (NA). The effects of biochar species were ordered as CSC > WSC ≈ PSC > PCC. The stabilization performance of Pb in soil was enhanced with increasing aging time. The mechanism of Pb stabilization in soil by biochar involves surface complexation, co-precipitation, ion exchange, physical adsorption, and electrostatic attraction. Conclusions The adsorption and stabilization of Pb in soil were enhanced by biochar aging through decreasing acid extractable Pb and increasing residual Pb. Surface complexation, co-precipitation, and physical adsorption were the main reasons for the enhancement.
176. 题目: Molecular characterization and spatial distribution of dicarboxylic acids and related compounds in fresh snow in China
期刊: Environmental Pollution
作者: Zhimin Zhang, Wanyu Zhao, Wei Hu, Junjun Deng, Lujie Ren, Libin Wu, Shuang Chen, Jingjing Meng, Chandra Mouli Pavuluri, Yele Sun, Zifa Wang, Kimitaka Kawamura, Pingqing Fu
摘要: Low molecular weight organic compounds are ubiquitous in the atmosphere. However, knowledge on their concentrations and molecular distribution in fresh snow remains limited. Here, twelve fresh snow samples collected at eight sites in China were investigated for dicarboxylic acids and related compounds (DCRCs) including oxocarboxylic acids and α-dicarbonyls. Dissolved organic carbon (DOC) concentrations in the snow samples ranged from 0.99 to 14.6 mg C L−1. Concentrations of total dicarboxylic acids are from 225 to 1970 μg L−1 (av. 650 μg L−1), while oxoacids (28.3–173, av. 68.1 μg L−1) and dicarbonyls (12.6–69.2, av. 31.3 μg L−1) were less abundant, accounting for 4.6–8.5% (6.2%), 0.45–1.4% (0.73%), and 0.12–0.88% (0.46%) of DOC, respectively. Molecular patterns of dicarboxylic acids are characterized by a predominance of oxalic acid (C2) (95.0–1030, av. 310 μg L−1), followed by phthalic (Ph) (9.69–244, av. 69.9 μg L−1) or succinic (C4) (23.8–163, av. 63.7 μg L−1) acid. Higher concentrations of Ph in snow from Beijing and Tianjin than other urban and rural regions suggest significant emissions from vehicular exhausts and other fossil fuel combustion sources in megacities. C2 constituted 40–54% of total diacids, corresponding to 1.5–2.6% of snow DOC. The total measured DCRCs represent 5.5–10% of snow DOC, which suggests that there are large amounts of unknown organics requiring further investigations. The spatial distributions of diacids exhibited higher loadings in megacities than rural and island sites. Molecular distributions of diacids indicated that the photochemical modification was restrained under the weak solar radiation during the snow events, while anthropogenic primary sources had a more significant influence in megacities than rural areas and islands.
177. 题目: Role of 15N in tracing biologically driven nitrogen dynamics in soils amended with biochar: A review
期刊: Soil Biology and Biochemistry
作者: Eric T. Craswell, Phillip M. Chalk, Bhawana Bhatta Kaudal
摘要: Extensive reports on research into the effects of biochar additions on soil-plant systems show many inconsistencies in the response of various parameters including nitrogen (N) transformations. This review focusses on the use of the stable isotope 15N to provide unique information about the N dynamics in biochar-amended systems. The properties of biochars and their impacts on N cycling depends on the feedstock and pyrolysis parameters, as well as the soil type, plant species and form of 15N fertilizer. A review of the results of 15N tracer studies of the effects of biochar addition on a variety of N transformations shows the following: depending on the soil type, biochar addition can reduce N leaching; ammonia volatilization may be increased but more research is needed on this loss mechanism; biochar may catalyse the reduction of N2O to N2, thus reducing greenhouse gas emissions; biochar effects on biological N2 fixation are inconsistent and especially depend on the biochar feedstock as well as soil type; the mechanisms for the variability in the effects of biochar on N mineralization-immobilization remain obscure; pot studies show that plant recovery of 15N-labelled urea is generally less than 50% and inconsistently affected by biochar addition. The lack of consistency evident when studies are compared reflects the diversity of biochar properties and frustrates efforts to synthesise overarching hypotheses that could confidently predict the effects of biochar addition on any specified soil N transformation.
178. 题目: Enhancement of the Cd phytoremediation efficiency of Festuca arundinacea by sonic seed treatment
作者: Xiaowen Gu, Qinghua Zhang, Yifan Jia, Min Cao, Wei Zhang, Jie Luo
摘要: It has been reported that both naturally occurring and artificially created sounds can alter the physiological parameters of various plants. A series of experiments were designed in the present study to estimate the physiological responses and the variation in the Cd decontamination capacity of Festuca arundinacea under sonic wave treatments. Plant seeds were treated by sound waves of frequency 200, 300, 400, 500, and 1000 Hz, and the germinated seedlings were transplanted to Cd-polluted soil. The results showed that all the sonic treatments increased the whole plant dry weight of F. arundinacea compared with that of the control, and the highest value was observed in the 200 Hz treatment. The Cd content in below-ground and aerial tissues of the species increased with increasing frequency till 400 Hz, after which they became constant. A higher proportion of senescent and dead leaf tissues was observed in the high-frequency treatment (1000 Hz), and more Cd was transferred to these failing tissues. Therefore, in the 1000 Hz treatment, a significantly greater amount of Cd could be eliminated by harvesting the senescent and dead leaf tissues of the species compared with that of the other treatments. The concentrations of dissolved organic matter (DOM) and the proportions of hydrophilic fractions which have a strong Cd affinity, in the rhizosphere soil of F. arundinacea increased with the increase in sound frequency. Cd extraction ability of DOM also increased with increasing frequency. This study indicated that a suitable sonic treatment can improve the phytoextraction efficiency of F. arundinacea, and also explained the mechanism from the perspective of the variations in soil DOM.
179. 题目: Photodegradation of roxarsone in the aquatic environment: influencing factors, mechanisms, and artificial neural network modeling
期刊: Environmental Science and Pollution Research
作者: Jizhong Meng, , Shoujun Yuan, Wei Wang, Juliang Jin, Xinmin Zhan, Liwen Xiao, Zhen-Hu Hu
摘要: Roxarsone (ROX), an organoarsenic feed additive, can be discharged into aquatic environment and photodegraded into more toxic inorganic arsenics. However, the photodegradation behavior of ROX in aquatic environment is still unclear. To better understand ROX photodegradation behavior, the influencing factors, photodegradation mechanism, and process modelling of ROX photodegradation were investigated in this study. The results showed that ROX in the aquatic environment was degraded to inorganic As(III) and As(V) under light irradiation. The degradation efficiency was enhanced by 25% with the increase of light intensity from 300 to 800 μW/cm2 via indirect photolysis. The photodegradation was temperature dependence, but was only slightly affected by pH. Nitrate ion (NO3-) had an obvious influence, but sulfate, carbonate, and chlorate ions had a negligible effect on ROX degradation. Dissolved organic matter (DOM) in the solution inhibited the photodegradation. ROX photodegradation was mainly mediated by reactive oxygen species (in the form of single oxygen 1O2) generated through ROX self-sensitization under irradiation. Based on the data of factors affecting ROX photodegradation, ROX photodegradation model was built and trained by an artificial neural network (ANN), and the predicted degradation rate was in good agreement with the real values with a root mean square error of 1.008. This study improved the understanding of ROX photodegradation behavior and provided a basis for controlling the pollution from ROX photodegradation.
180. 题目: Temporal dynamics of mixed litter humification in an alpine treeline ecotone
期刊: Science of The Total Environment
作者: Yu Zhou, Lifeng Wang, Yamei Chen, Jian Zhang, Zhenfeng Xu, Li Guo, Lixia Wang, Chengming You, Bo Tan, Li Zhang, LiangHua Chen, JiuJin Xiao, Peng Zhu, Yang Liu
摘要: Loss of plant diversity affects mountain ecosystem properties and processes, yet few studies have focused on the impact of plant function type deficiency on mixed litter humification. To fill this knowledge gap, we conducted a 1279-day litterbag decomposition experiment with six plant functional types of foliar litter to determine the temporal dynamic characteristics of mixed litter humification in a coniferous forest (CF) and an alpine shrubland (AS). The results indicated that the humus concentrations, the net accumulations and their relative mixed effects (RME) of most types were higher in CF than those in AS at 146 days, and humus net accumulations fell to approximately -80% of the initial level within 1279 days. The RME of the total humus and humic acid concentrations exhibited a general change from synergistic to antagonistic effects over time, but the mixing of single plant functional type impeded the formation of fulvic acid due to consistently exhibited antagonistic effects. Ultimately, correlation analysis indicated that environmental factors (temperature, snow depth and freeze-thaw cycles) significantly hindered litter humification in the early stage, while some initial quality factors drove this process at a longer scale. Among these aspects, the concentrations of zinc, copper and iron, as well as acid-unhydrolyzable residue (AUR):nitrogen and AUR:phosphorous, stimulated humus accumulation, while water-soluble extractables, potassium, magnesium and aluminium hampered it. Deficiencies in a single plant functional type and vegetation type variations affected litter humification at the alpine treeline, which will further affect soil carbon sequestration, which is of great significance for understanding the material circulation of alpine ecosystems.