61. 题目: Behaviors and fate of adsorbed Cr(VI) during Fe(II)-induced transformation of ferrihydrite-humic acid co-precipitates
期刊: Journal of Hazardous Materials
作者: Guangda Yu, Fenglian Fu, Chujia Ye, Bing Tang
摘要: The mobility of Cr(VI) in the environment is affected by the transformation of ferrihydrite (Fh) and ferrihydrite-humic acid co-precipitates (Fh-HA). However, the impacts of Fe(II)-induced transformation of Fh and Fh-HA on the mobility, speciation and partitioning of associated Cr(VI) remain unclear. In this study, the behaviors of adsorbed Cr(VI) during Fh and Fh-HA aging at 70 °C for 9 days (pH0 = 3.0 and 7.0) in the absence and presence of Fe(II) were studied. Results revealed that the main speciation of Cr(VI) after transformation was non-desorbable Cr and its formation involved the following pathways. Firstly, Fe(II) (0.2 and 2.0 mM) induced the transformation of Fh-HA to hematite and goethite, promoting the structural incorporation of adsorbed Cr into hematite and goethite via complexation. Secondly, under neutral condition (pH0 = 7.0), the low concentration of Fe(II) (0.2 mM) could not reduce completely Cr(VI) to Cr(III) and thus residual Cr(VI) was incorporated into the Cr(III)-Fe(III) co-precipitates. Thirdly, coprecipitated humic acid not only reduced Cr(VI) to Cr(III) via polysaccharide, but also formed complexes with incorporated Cr through carboxylic groups to sequester Cr. Our results demonstrate that Fe(II)-induced transformation of Fh-HA exerts major influences on associated Cr(VI) speciation and partitioning.
62. 题目: Optical properties of aerosol brown carbon (BrC) in the eastern Indo-Gangetic Plain
期刊: Science of The Total Environment
作者: Archita Rana, Supriya Dey, Prashant Rawat, Arya Mukherjee, Jingying Mao, Shiguo Jia, Pandit S. Khillare, Amit Kumar Yadav, Sayantan Sarkar
摘要: We report here measurements of aerosol black carbon (BC) and aqueous and methanol-extractable brown carbon (BrCaq and BrCme) from a receptor location in the eastern Indo-Gangetic Plain (IGP) under two aerosol regimes: the photochemistry-dominated summer and biomass burning (BB) dominated post-monsoon. We couple time-resolved measurements of BC and aerosol light absorption coefficients (babs) with time-integrated analysis of BrC UV–Vis and fluorescence characteristics, along with measurements of total and water-soluble organic carbon (OC and WSOC), and ionic species (NH4+, K+, NO3−). In the BB regime, BC and its BB-derived fraction (BCBB) increased by factors of 3–4 over summertime values. In comparison, babs_365_aq and babs_365_me (absorption coefficients of BrCaq and BrCme at 365 nm) increased by a factor of 5 (9.7 ± 7.8 vs 2.1 ± 1.4 Mm−1) and 2.5 (17.2 ± 9.0 vs 6.9 ± 2.9 Mm−1), respectively, in the BB period over summer, and were highly correlated (r = 0.82–0.87; p < 0.01) with the BB-tracer nssK+. The wavelength dependence of babs_BrC (Ångstrom exponent: 5.9–6.2) and the presence of characteristic fluorescence peaks at 420–430 nm suggested presence of humic-like substances (HULIS) in the aged BB aerosol, while significant association between BrCaq and NO3− (r = 0.73; p < 0.01) possibly indicated formation of water-soluble nitroaromatic compounds. BrCaq contributed 55% to total BrC absorption at 300–400 nm while that for the water-insoluble component (WI-BrC) increased from 41% at 340 nm to ~60% at 550 nm, suggesting formation of water-insoluble polycyclic aromatic hydrocarbons (PAHs) and/or N-PAHs. Mass absorption efficiencies at 365 nm (MAE365) of BrCaq and BrCme in the BB regime (0.95 ± 0.45 and 1.17 ± 0.78 m2 g−1, respectively) were in line with values expected from photobleaching of BB source emissions after transport to the eastern IGP. Overall, BrCaq and BrCme were significant components of light absorbing aerosol in the BB regime, with contributions of 9 ± 5% and 16 ± 7%, respectively, to radiative forcing vis-à-vis BC in the 300–400 nm range.
63. 题目: Soil organic carbon pool and chemical composition under different types of land use in wetland: Implication for carbon sequestration in wetlands
期刊: Science of The Total Environment
作者: Huai Ji, Jiangang Han, Jianming Xue, Jeff A. Hatten, Minhuang Wang, Yanhui Guo, Pingping Li
摘要: This study was conducted to understand how different wetland vegetation-land use types influenced the storage and stability of soil organic carbon (SOC) in surface soils. We determined the concentration and chemical composition of SOC in both density (including light fraction organic carbon (LFOC) and heavy fraction organic carbon (HFOC)) and particle size fractions (including <2 μm, 2–63 μm, 63–200 μm and 200–2000 μm) in four wetland land use types covered with different vegetation: lake-sedge, reed, willow and poplar wetlands. Results showed that the concentrations and stock of SOC and LFOC in willow and poplar wetlands were significantly higher than those in lake-sedge and reed. However, a higher proportion of alkyl-C and a lower proportion of O-alkyl-C were observed in lake-sedge and reed wetlands than in willow and poplar, suggesting that accumulated C in willow and poplar wetlands was less stable than that in lake-sedge and reed. For all particle-size fractions except the silt (2–63 μm), the SOC concentrations were highest in willow and lowest in reed wetland surface soils, while their alkyl-C/O-alkyl-C (A/O-A) and hydrophobic-C/hydrophilic-C ratios progressively decreased from lake-sedge and reed wetland surface soils to poplar and willow surface soils. Moreover, the ratios of A/O-A and hydrophobic-C/hydrophilic-C in surface soils generally decreased with increasing concentrations of SOC in particle-size fractions, with these stability indexes being lowest in the largest particle-size fraction. These results indicate that the wetland vegetation-land use types that could incorporate more C into finer particle-size fractions had a greater potential for sequestering more stable C in such wetland ecosystems. Different wetland vegetation-land use types resulted in significant changes in the concentration and chemical structure of SOC, which could affect soil C sequestration and dynamics, C cycling in wetland ecosystems. Although both willow and poplar forests could increase SOC stock, the stability of SOC in willow wetland was higher. Therefore, on balance (stock and stability) the land use of wetland for willow forest could be a more promising way for enhancing soil C sequestration in wetlands.
64. 题目: Modeling the formation of microorganism-derived dissolved organic nitrogen (mDON) in the activated sludge system
期刊: Water Research
作者: Haidong Hu, Kewei Liao, Wenming Xie, Jinfeng Wang, Bing Wu, Hongqiang Ren
摘要: Microorganism-derived dissolved organic nitrogen (mDON) represents a significant and inevitable portion of dissolved organic nitrogen (DON) in the wastewater biotreatment processes. In the existing method, mDON concentrations are indirectly measured by the values of DON concentrations from the reactors with DON-free influent. However, this becomes problematic when influent contains DON. Especially when the real wastewater is involved, the paucity of the direct methods to quantitatively measure mDON is a major barrier to further research. This limitation is due to the difficulty of segregating mDON from the other nitrogenous organics, e.g., influent DON. In this study, we propose the ASM-mDON model based on ASM #1, which incorporates the production and consumption of mDON in the activated sludge processes to predict the mDON concentrations. In four independent lab-scale tests, our model was established and calibrated to obtain the accurate values of mDON (R2 = 0.929, p < 0.05), and the validity and applicability of the model were successfully examined by comparing the simulated and measured data. Moreover, the universality of the ASM-mDON model was further confirmed by simulating mDON production in a full-scale wastewater treatment plant. A reasonable prediction of mDON formation was shown in a full-scale test (1.98 ± 0.71 mg/L in June and 1.51 ± 0.54 mg/L in July) and is indirectly supported by an algal bioassay (p < 0.05, t-test). This study provides a useful approach to the efficient and accurate evaluation of mDON formation, which will improve current strategies designed to minimize the effluent mDON in wastewater bioprocesses.
65. 题目: Element composition of soils to assess the success of wetland restoration
期刊: Land Degradation & Development
作者: Guodong Wang, Ming Jiang, Ming Wang, Zhenshan Xue
摘要: The main purpose of this study is to assess if wetland restoration is associated with a directional shift in soil element concentration toward their original pre‐farming status in the peatlands of northeastern China. The concentrations of 55 soil elements and related environmental factors including organic matter content, electrical conductivity and pH were investigated in natural, restored and farmed wetlands in the Xingkai Lake Watershed of northeastern China. All but four of the soil element concentrations varied by wetland type (natural, restored, and farmed wetlands), and the soil concentrations of 41 elements increased from natural to restored to farmed wetlands. Soil organic matter and electrical conductivity explained 87.8% and 3.3% of the variation in element concentration based on ordination analysis using RDA. Both non‐metric multidimensional scaling analysis (NMDS) and cluster analysis indicated that the restored wetlands had a higher similarity with the farmed wetlands than the natural wetlands. Our findings suggest that restoration led to an increase in soil organic matter content and shifts in level of element concentration that was more similar to natural wetlands. However, differences remained so that the biogeochemistry of restored wetlands was not the same as the original pre‐farming level. This information is very important for wetland restoration, because to be successful, not only biodiversity and hydrology, but also the soil element composition and biogeochemistry need to be restored. Our approach can be used to assess the success of wetland restoration.
66. 题目: Determinants of Soil Organic Carbon Sequestration and Its Contribution to Ecosystem Carbon Sinks of Planted Forests
期刊: Global Change Biology
作者: Shiqiang Wang, Yao Huang
摘要: The area of forest established through afforestation/reforestation has been increasing on a global scale, which is particularly important as these planted forests attenuate climate change by sequestering carbon. However, the determinants of soil organic carbon sequestration and their contribution to the ecosystem carbon sink of planted forests remains uncertain. By using globally distributed data extracted from 154 peer‐reviewed publications and a total of 355 sampling points, we investigated above‐ground biomass carbon (ABC) sequestration and soil organic carbon (SOC) sequestration across three different climatic zones (tropical, warm temperate, and cold temperate) through correlation analysis, regression models, and structural equation modeling (SEM). We found that the proportion of SOC sequestration in the ecosystem C sequestration averaged 14.1% globally, being the highest (27.0%) in the warm temperate and the lowest (10.7%) in the tropical climatic zones. The proportion was mainly affected by latitude. The sink rate of ABC (RABC) in tropical climates (2.48 Mg C ha−1 yr−1) and the sink rate of SOC (RSOC) in warm temperate climates (0.96 Mg C ha−1 yr−1) were higher than other climatic zones. The main determinants of RSOC were the number of frost‐free days, latitude, mean annual precipitation (MAP), and soil organic carbon density (SOCD) at the initial observation; however, these variables depended on the climatic zone. According to the SEM, frost‐free period MAT, and MAP are the dominant driving factors affecting RSOC in Chinese plantations. MAT has an positive effect on RSOC, and global warming may increase RSOC of temperate plantations in China. Our findings highlight the determinants of SOC sequestration and quantitatively reveal the substantial global contribution of SOC sequestration to ecosystem carbon sink provided by planted forests. Our results help managers identify and control key factors to increase carbon sequestration in forest ecosystems.
67. 题目: Comparative study on Pb2+ removal from aqueous solutions using biochars derived from cow manure and its vermicompost
期刊: Science of The Total Environment
作者: Weiwen Zhang, Wenhui Du, Feng Wang, Huiting Xu, Tonghe Zhao, Hangjun Zhang, Ying Ding, Weiqin Zhu
摘要: Waste emissions have increased the amount of water and soil contaminated with heavy metals such as Pb. To broaden the methods for the recycling and environmental usage of cow manure (CM) and its vermicompost (CV), CM, CV, and their derived biochars produced by the pyrolysis of CM or CV at 350 and 700 °C were used as adsorbents for Pb2+ removal in this batch adsorption experiment to reveal their different Pb2+ removal efficiencies and the underlying mechanisms. The batch experiment results revealed that all adsorbents rapidly removed Pb2+ within 30 min. A pH between 2.0 and 6.0 positively affected Pb2+ removal by CM and its biochar, whereas that by CV and its biochar was only positively affected by pH between 2.0 and 3.0. CV-derived biochar was more effective in the removal of Pb2+ than the other absorbents, with the maximum adsorption capacities (Qm) fitted from the Langmuir model reaching approximately 230.0 mg·g−1 and the desorption rate (DR) being approximately 0.00–0.02%. Material physiochemical characterization, including X-ray diffraction analysis, showed that high pH, high ash content, rich mineral content, and high mineral contents might have been the main reasons for more effective removal of Pb2+ from aqueous solutions by CV-derived biochar. Fourier-transform infrared analysis indicated that surface functional groups such as –OH, CO, –COO–, and C–O; original and newly produced carbonate; and phosphate in CV also led to more effective Pb2+ removal efficiency from aqueous solution via surface functional group binding. Thus, pyrolyzing CVs may be used to produce biochar as a cost-effective adsorbent for heavy metal remediation in soil and water in the future.
68. 题目: Dissolved organic matter controls of arsenic bioavailability to bacteria
期刊: Science of The Total Environment
作者: Martin P. Pothier, Véronique Lenoble, Cédric Garnier, Benjamin Misson, Charlotte Rentmeister, Alexandre J. Poulain
摘要: The presence of arsenic in irrigation and drinking waters is a threat to worldwide human health. Dissolved organic matter (DOM) is a ubiquitous and photoreactive sorbent of arsenic, capable of both suppressing and enhancing its mobility. Microbes can control the mobilization of mineral-bound arsenic, through redox processes thought to occur intracellularly. The role that DOM plays on the bioavailability of arsenic to microbes is often invoked but remains untested experimentally. Here, using a whole-cell biosensor, we tested the role of DOM on As(III) and As(V) bioavailability. Using cation amendments, we explored the nature of As-DOM interactions. We found As bioavailability to be dependent on [As]/[DOM] ratio and on the strength of As binding to DOM which varied as a function of time. We further tested the role of DOM on As(III) photooxidation and showed that As(III) photooxidation rate is limited by the strength of its interactions with DOM and sensitive to ionic competitive desorption. Our study demonstrates the dynamic control that photoreactive DOM poses on the bioavailability and reactivity of As in the environment and highlights the kinetic controls that DOM can possibly exert on As toxicity at various levels in foodwebs.
69. 题目: Accumulation of metals and changes in composition of freshwater lake organic sediments during the Holocene
期刊: Chemical Geology
作者: Karina Stankevica, Zane Vincevica-Gaile, Maris Klavins, Laimdota Kalnina, Normunds Stivrins, Ieva Grudzinska, Enn Kaup
摘要: The distribution of metals in the strata of sediments deposited in the freshwater environment formed during the Holocene in the territory of Latvia has been studied rather insufficiently. Considering the large volume of accumulated organic matter in sediments, studies on the content of metallic elements in sediments can help to determine the peculiarities of the metal accumulation process in limnic systems and the biogeochemical cycling of metals. Lake Pilvelis, which is located in the eastern part of Latvia (the northern part of Europe), was selected as the main study site. Lake Pilvelis is a small lake of a glacial origin, and >90% of its depression is filled with organic-rich sediments. The development stages of Lake Pilvelis since circa 10,000 cal BP are described in detail via reconstruction of the Holocene palaeoenvironmental conditions using multi-proxy sedimentary records. The elemental composition and content of metallic elements in sapropel are analysed with the main objectives of characterising the accumulation rate of metals in the full profile of sapropel and determining the anthropogenic impact depending on the evolution of the lake and the genesis of sediment organic matter. The correlation among the components characterising sediments such as sapropel and metallic elements revealed that the elemental distribution could be divided into three main groups according to the content of the elements associated with organic compounds (e.g., for Zn and Mn) and mineral compounds (for Ni, Co, Cr, K, Fe, Mg, and Cu). Ni and Co are partly associated with mineral compounds and partly associated with carbonates. A principal component analysis revealed the main factors indicating the origin of metallic elements and the accumulation tendencies of metals in sediment layers: the input of the mineral matter, the characteristics of organic matter, and human impact. The content of metallic elements in sapropel from Lake Pilvelis is mainly affected by the composition of mineral matter, not by the size of the particles.
70. 题目: Assessing the prevalence, products, and pathways of dissolved organic matter partial photo-oxidation in arctic surface waters
期刊: Environmental Science: Processes Impacts
作者: Collin P
Ward, Rose M.
摘要: In sunlit waters, photodegradation of dissolved organic matter (DOM) yields completely oxidized carbon (i.e., CO2) as well as a suite of partially oxidized compounds formed from oxygen incorporation (i.e., partial photo-oxidation). Of these two groups of DOM photo-products, most studies focus on CO2 (a greenhouse gas) than on partially oxidized DOM, which is likely a diverse group of compounds with poorly constrained roles in aquatic carbon cycling or biogeochemistry. The objective of this study is to address knowledge gaps on the prevalence, products, and pathways of DOM partial photo-oxidation. Here we traced the photochemical incorporation of isotopically labelled 18O2 into DOM isolated from Alaskan Arctic surface waters using high-resolution mass spectrometry. Complete and partial photo-oxidation oxidation of DOM was also quantified as CO2 production and O2 consumption. The majority of 18O-containing partial oxidation photo-products were classified as carboxylic rich alicyclic molecules (CRAM) and overlapped in composition with previously reported photo-products known to result from the oxidation of DOM by singlet oxygen. These results support a previously proposed hypothesis that photo-oxidation by singlet oxygen may contribute to the formation of CRAM, a compound class of DOM ubiquitously observed in surface waters. The novel application of an isotopic tracer for oxygen incorporation with a mass balance approach to quantify complete and partial photo-oxidation of DOM revealed that less than one mol of O2 is required to produce one mol of CO2. A sensitivity analysis based on this new knowledge demonstrated that the magnitude of DOM partial photo-oxidation may be underestimated by up to four-fold. Consequently, partial photo-oxidation likely plays a more prominent role in shaping DOM composition in sunlit waters of the Arctic than previously understood. Therefore, partial photo-oxidation should be increasingly incorporated into the experimental framework of studies focused on DOM composition in surface waters.
71. 题目: Impacts of redox conditions on dissolved organic matter (DOM) quality in marine sediments off the River Rhône, Western Mediterranean Sea
期刊: Geochimica et Cosmochimica Acta
作者: Shuchai Gan, Frauke Schmidt, Verena B. Heuer, Tobias Goldhammer, Matthias Witt, Kai-Uwe Hinrichs
摘要: Sedimentary dissolved organic matter (DOM) is an important pool of intermediates produced and consumed during early diagenesis of organic matter in the anoxic subseafloor. Rapid degradation of organic matter in the coastal sediment results in stratification of redox zones. However, to date little is known about the selectivity with respect to organic matter of the initial microbially mediated anaerobic degradation processes under contrasting redox conditions and how these affect the composition of DOM. In order to study the effect of sulfate reducing vs. methanogenic conditions on DOM quality and degradation, sediments (0-18 cm) from the Rhône River Delta were incubated, with redox conditions being controlled by sulfate amendment. The progress of incubation was monitored by H2, CH4, sulfate, DIC, DOC and acetate production. DOM composition was determined by 3D Fluorescence Spectroscopy, i.e., Excitation Emission Matrix Spectroscopy (EEMs), and ultra-high-resolution Fourier Transform Ion Cyclotron Resonance Mass Spectrometry (FT-ICR-MS). Parallel factor analysis (PARAFAC) of EEMs was used to distinguish different groups of DOM (humic-like and protein-like compounds) to evaluate composition, conjugation and size of DOM. Prior to incubation, humic-like sedimentary DOM predominated; nearly half of the molecular formulae (>5000) identified by FT-ICR-MS were CHO and one third were CHNO compounds. During incubation, protein-like DOM and CHNO formulae with 3 and 4 N atoms formulae were rare under both sulfate reducing and methanogenic conditions. Incubation under sulfate reducing conditions resulted in rapid release and net accumulation of dissolved organic carbon (DOC). Protein-like DOM was rapidly cycled and humic-like DOM accumulated. Consistently, CHNO formulae with 3 and 4 N atoms decreased faster, whereas formulae with one N and oxygen-rich unsaturated compounds became more concentrated. In contrast, during incubation under methanogenic conditions, there was no net accumulation of DOC; blue-shift of humic-like peaks suggest the transformation possibly associated with loss of oxygen-bearing functional groups in conjugated structures of humic substances. This interpretation is consistent with the relative decrease of oxygenation and carbon number in the pool of aromatic and highly unsaturated compounds observed by FT-ICR-MS analysis. Approximately 90% of molecular formulae that were lost under methanogenic conditions were accumulated under sulfate reducing conditions. Our results suggest that under sulfate reducing conditions degradation of organic matter results in the accumulation of highly oxidized DOM, while protein-like compounds are selectively consumed. When the redox regime changes to methanogenic conditions, microbes apparently utilize the humic-like and oxygen-rich compounds of the oxidized DOM pool that accumulated under sulfate reducing conditions. Consequently, redox regimes and the associated biogeochemical processes influence rate and fractions of DOM released by and consumed in the deep biosphere, which could ultimately shape the composition of the preserved sedimentary organic matter and the DOM released to the ocean.
72. 题目: Soil physico-chemical properties are more important than microbial diversity and enzyme activity in controlling carbon and nitrogen stocks near Sydney, Australia
作者: Jinquan Li, Ming Nie, Elise Pendall
摘要: Soil organic carbon (SOC) and available nitrogen (N) stocks are controlled by the complex interplay of soil physical, chemical, and biological conditions. However, the interrelations of SOC or available N with these drivers as well as their relative importance are rarely evaluated quantitatively. Using investigations of SOC density (SOCD) and available N density (ND) with other detailed soil properties of topsoil (0–10 cm) and subsoil (20–30 cm) from 33 sites under different ecosystems in the vicinity of an eddy flux tower near Sydney, Australia, we investigated the controls of soil physical, chemical, and biological properties (a total of 19 variables) on SOCD and available ND. Structural equation models showed that only physical and chemical properties significantly and directly affected SOCD and available ND. Among these variables, physical and chemical properties were the most influential factors, while the relative influences of microbial biodiversity and enzyme activity were small based on boosted regression tree analysis. In addition, the effects of variables on SOCD and available ND differed between the topsoil and subsoil. In the topsoil, soil physical properties had the highest relative influence followed by chemical properties, enzyme activities, and microbial biodiversity; in the subsoil, however, soil chemical properties had the highest relative importance followed by physical properties, enzyme activities, and microbial biodiversity. This comprehensive soil characterization provides the biogeochemical context for ecosystem carbon cycling being monitored at a nearby eddy flux tower, and demonstrates the importance of including accurate measurements of soil physical and chemical properties to reduce uncertainty in soil C and N predictions in process-based models. However, this is a local-scale study, and large-scale studies are warranted to gain further understanding on this issue.
73. 题目: Composition and source apportionment of saccharides in aerosol particles from an agro-industrial zone in the Indo-Gangetic Plain
期刊: Environmental Science and Pollution Research
作者: Muhammad Usman Alvi, Magdalena Kistler, Imran Shahid, Khan Alam, Farrukh Chishtie, Tariq Mahmud, Anne Kasper-Giebl
摘要: The characterization of saccharidic compounds in atmospheric aerosols is important in order to retrieve information about organic carbon sources and their transport pathways through the atmosphere. In this study, composition and sources of saccharides in PM10 were determined in a South Asian megacity (Faisalabad) during the year 2015 – 2016. PM10 sampled on quartz filters was analyzed by anion exchange chromatography for the selected saccharidic compounds. The average PM10 concentration was found to be 744 ± 392 μg m−3, exceeding the daily limits proposed by Pak-EPA (150 μg m−3), US-EPA (150 μg m−3), and WHO (50 μg m−3). The average total saccharidic concentration was found to be 2820 ± 2247 ng m−3. Among the different saccharidic categories, anhydrosugars were the most abundant in concentration followed by primary sugars and sugar alcohols. The correlation and principal component analysis indicated emissions from biomass combustion, soil suspensions from areas such as farmlands having high microorganism activity, and biogenic emissions such as airborne fungal spores and vegetation detritus as major sources of saccharides in the aerosol samples.
74. 题目: Sorption and molecular fractionation of biochar-derived dissolved organic matter on ferrihydrite
期刊: Journal of Hazardous Materials
作者: Peng Zhang, Aiju Liu, Peng Huang, Lujuan Min, Hongwen Sun
摘要: Molecular fractionation of dissolved organic matter (DOM) induced by the sorption on soil minerals is a common geochemical process in soil, which has been well documented on natural DOM. Biochar is an emerging soil amendment and can continuously release DOM into the soil. However, reports regarding the interactions of soil minerals and biochar-derived DOM are limited. Herein, the molecular fractionation of DOMs derived from biochar samples obtained by pyrolyzing maize straw (MS) at 300 and 500 °C (M3 and M5) and MS (selected as the control) after sorption on ferrihydrite, a common soil mineral, was investigated for the first time. Results showed that biochar-derived DOMs contained greater aromatic and less aliphatic and O-containing structure compared to MSDOM. The sorption affinities of ferrihydrite for the three DOMs were in the order of M5DOM > M3DOM > MSDOM. A greater decrease in zeta potential and more external C-O species were observed in ferrihydrite after sorption of M5DOM than after sorption of MSDOM or M3DOM. DOM components with high molecular weights and high contents of unsaturated oxidized or aromatic structures were preferentially sorbed by ferrihydrite via hydrophobic partition, H-bonding and electrostatic interactions. Polycyclic aromatics and polyphenols in MSDOM and M3DOM were the primary components sorbed by ferrihydrite, while the highly unsaturated and phenolic compounds in M5DOM showed stronger affinity to ferrihydrite. The oxygen-containing functional groups and unsaturation level are the primary parameters controlling the molecular fractionation of biochar-derived DOM on ferrihydrite. The results of this study help to get deep insight on the environmental behavior of straw- and biochar-derived DOMs in soil.
75. 题目: The evolution of respiratory systems in Theropoda and Paracrocodylomorpha, the end-Triassic extinction, and the role of Late Triassic atmospheric O2 and CO2
期刊: Palaeogeography, Palaeoclimatology, Palaeoecology
作者: Michael Naylor Hudgins, Mark D. Uhen, Linda A. Hinnov
摘要: During the Late Triassic Period (235–201.3 Ma), Paracrocodylomorpha and Theropoda switched predatory roles, with the former filling the subsidiary predator niche and the latter filling the top predator niche at the end-Triassic extinction. Reasons for the transition in predator guilds remain unknown, but atmospheric conditions during this time, which involved high CO2 and low O2 concentration levels, may be associated with the event. Evidence of bird-like pneumatic post-crania, present in both groups as foramina and fossae, correlates with an avian-like respiratory system. This may have allowed organisms to cope with declining atmospheric O2 environments of the Late Triassic. This study estimated pO2 throughout the late Triassic using organic carbon isotope measurements from Newark-Hartford basin paleosols and examined the morphological change in skeletal remains of Theropoda, focusing on pneumatic bones, compared with Paracrocodylomorpha during the Late Triassic and across the Triassic-Jurassic boundary. With data compiled from the Paleobiology Database and published anatomical literature, the change of pneumaticity in taxa is quantified by a Pneumatic Index (PI), in which the number of pneumatized units is divided by the total number of bones examined. Patterns of pneumaticity are individually scored for the presence or absence of pneumatic bones. Morphological data are compared to corresponding femur length, estimated atmospheric O2 and CO2 level reconstructions, and an ancestral state reconstruction depicting how PI values change throughout various clades. Our results suggest that PI values in Theropoda and Paracrocodylomorpha correspond with the vacillating pO2 and pCO2 throughout the Late Triassic and into the Jurassic. High PI values are prevalent in advanced theropod taxa, while Paracrocodylomorpha PI values vary by clade with a generally negative trend throughout the Triassic. Ancestral state reconstruction analysis highlights the increasing PI values within Theropoda and clade dependent trends in Paracrocodylomorpha. This study is instrumental in reconstructing how Theropoda became evolutionarily successful and perhaps how and why the avian-like respiratory system originated.
76. 题目: Use of optical properties for evaluating the presence of pyrogenic organic matter in thermally altered soil leachates
期刊: Environmental Science: Processes Impacts
McKay, Amanda K
摘要: The increased frequency and severity of wildfires in forested watersheds has the potential to significantly impact the quantity and quality of water extractable organic matter (WEOM) exported from these ecosystems. This study examined the optical properties of WEOM from laboratory heated soil in order to understand physicochemical changes occurring in the organic matter as a result of heating, as well as test the usefulness of optical parameters for assessing the presence of pyrogenic organic matter. WEOM absorbance and fluorescence spectral shape and intensity varied systematically as a function of soil heating temperature. Notably, absorbance and fluorescence intensity, specific ultraviolet absorbance, apparent fluorescence quantum yield, specific fluorescence emission intensity, and maximum fluorescence emission wavelength exhibited consistent changes with heating temperature and indicated that WEOM in heated soil leachates was lower in molecular weight and more aromatic than in unheated samples. The lower molecular weight in heated soil WEOM was corroborated with size-exclusion chromatography measurements. This work increases the understanding of the molecular changes occurring in WEOM as a result of wildfire and indicates that optical measurements (i.e., absorbance and fluorescence) could be used for watershed monitoring of post-fire pyrogenic organic matter.
77. 题目: Could cryoturbic diapirs be key for understanding ecological feedbacks to climate change in High Arctic polar deserts?
期刊: Journal of Geophysical Research: Biogeosciences
作者: Mitsuaki Ota, Steven D. Mamet, Amanda L. Muller, Eric G. Lamb, Gurbir Dhillon, Derek Peak, Steven D. Siciliano
摘要: High Arctic polar deserts cover 26% of the Arctic. Increasing temperatures are predicted to significantly alter polar desert freeze‐thaw and biogeochemical cycles, with important implications for greenhouse gas emissions. However, the mechanisms underlying these changing cycles are still highly uncertain. Cryoturbic, carbon‐rich Bhy horizons (diapirs) in frost boils are key nutrient sources for Salix arctica. We hypothesized that diapirism leads to organic carbon characteristics that alter microbial pathways, which then control root foraging and greenhouse gas production. During July–August 2013, we characterized soil properties and examined gross nitrogen transformation rates in frost boils both with and without diapirs in two High Arctic polar deserts (dolomite and granite) near Alexandra Fjord (78°51′N 75°54′W), Ellesmere Island, Nunavut, Canada. Diapiric frost boils had 18% higher soil organic carbon in the dolomitic and 9% higher in the granitic deserts, and 29% higher total dissolved nitrogen in the dolomitic desert. However, diapirs decreased gross nitrogen mineralization rates by 30% in the dolomitic and by 48% in the granitic deserts. Attenuated total reflectance Fourier transformed mid‐infrared spectroscopy revealed greater concentrations of polysaccharides and recalcitrant carbon in diapiric versus non‐diapiric frost boils. These increased polysaccharide concentrations likely facilitate diapirism as soil viscosity increases with polysaccharides. Lower microbial activity or ectomycorrhizae that are known to colonize S. arctica may accumulate total dissolved nitrogen in diapirs. Our results suggest geomorphologic‐plant‐microbe interactions may underlie important patterns of geochemical cycling in arctic systems. Thus, polar desert frost boils should represent a key focus of future investigations of climate change in arctic systems.
78. 题目: Carbon cycling in the world's deepest blue hole
期刊: Journal of Geophysical Research: Biogeosciences
作者: P. Yao, X.C. Wang, T.S. Bianchi, Z.S. Yang, L. Fu, X.H. Zhang, L. Chen, B. Zhao, E.S. Morrison, M.R. Shields, Y.N. Liu, N.S. Bi, Y.Z. Qi, S. Zhou, J.W. Liu, H.H. Zhang, C.J. Zhu, Z.G. Yu
摘要: Blue holes are unique geomorphological features with steep biogeochemical gradients and distinctive microbial communities. Carbon cycling in blue holes, however, remains poorly understood. Here we describe potential mechanisms of dissolved carbon cycling in the world's deepest blue hole, the Yongle Blue Hole (YBH), which was recently discovered in the South China Sea. In the YBH, we found some of the lowest concentrations (e.g., 22 μM) and oldest ages (e.g., 6,810 years BP) of dissolved organic carbon, as well as the highest concentrations (e.g., 3,090 μM) and the oldest ages (e.g., 8270 years BP) of dissolved inorganic carbon observed in oceanic waters. Sharp gradients of dissolved oxygen, H2S and CH4 and changes in bacterially‐mediated sulfur‐cycling with depth indicated that sulfur‐ and/or methane‐based metabolisms are closely linked to carbon cycling in the YBH. Our results showed that the YBH is a unique and easily accessible natural laboratory for examining carbon cycling in anoxic systems, which has potential for understanding carbon dynamics in both paleo‐ and modern oceans – particularly in the context of global change.
79. 题目: Influence of pre-ozonation of DOM on micropollutant abatement by UV-based advanced oxidation processes
期刊: Journal of Hazardous Materials
作者: Bo Sun, Yu Wang, Yingying Xiang, Chii Shang
摘要: Dissolved organic matter (DOM), ubiquitously co-present in micropollutant-impaired water, significantly decreases micropollutant removal in UV-based AOPs through consuming radicals and filtering UV light. In this study, pre-ozonation was proposed to alleviate the negative effects of DOM on UV-based AOPs. After ozone treatment of DOM-containing water at ozone dosages of 0.1–1 mg O3/mg DOC, the degradation rate of benzoic acid (BA) in UV/H2O2 process increased by 7–34% mainly due to the enhanced transmission of UV light. The degradation rate of BA in UV/S2O82− process varied from -11% to 25% at ozone dosages of 0.1–1 mg O3/mg DOC because of the increased photolysis rate of S2O82− and the altered reactivity of DOM towards SO4−. Pre-ozonation of DOM at ozone dosage of 1 mg O3/mg DOC enhanced the oxidation rate of BA in UV/chlorine process by 35% due to the increased rate of chlorine photolysis and the decreased reactivity of DOM towards Cl. The influence of pre-ozonation on the formation potential of disinfection by-products (DBPs) depends on the kind of AOPs and the species of DBPs. The energy cost analysis suggests that pre-ozonation of DOM is an economic process for enhancing pollutant abatement by UV-based AOPs.
80. 题目: Hydrological fluxes of dissolved organic carbon and total dissolved nitrogen in subtropical forests at three restoration stages in southern China
期刊: Journal of Hydrology
作者: Yuyu You, Wenhua Xiang, Shuai Ouyang, Zhonghui Zhao, Liang Chen, Yelin Zeng, Pifeng Lei, Xiangwen Deng, Jiurong Wang, Keling Wang
摘要: In the restoration of subtropical forests, the hydrological fluxes of dissolved organic carbon (DOC) and total dissolved nitrogen (TDN) have not been fully investigated in different stages dominated by different tree species. The concentrations of DOC and TDN in rainfall, throughfall, stemflow, and surface runoff were measured for two years in each of the three forests at different restoration stages: early coniferous forest (Pinus massoniana - Lithocarpus glaber), intermediate deciduous broadleaved forest (Choerospondias axillaris), and late evergreen broadleaved forest (L. glaber - Cyclobalanopsis glauca). Input and output fluxes as well as leaching and migration coefficients of DOC and TDN were calculated to examine the nutrient cycling status in the processes of forest restoration. In stemflow, DOC concentrations in the evergreen broadleaved forest differed significantly from those in the coniferous and deciduous broadleaved forests, whereas TDN concentrations differed significantly between the coniferous forest and other two forests. In throughfall, DOC and TDN concentrations were not significantly different among the three forests. The amount of DOC leached was primarily influenced by rainfall and was significantly related to fluxes in throughfall, with the highest value in the deciduous broadleaved forest (57.78 kg C ha−1). However, the amount of TDN leached was affected by rainfall and the absorption of vegetation and was not significantly related to fluxes in throughfall, except for the deciduous broadleaved forest. The highest value of TDN leached was in the coniferous forest (11.90 kg N ha−1). Mean TDN concentration in surface runoff tended to increase but annual TDN output fluxes decreased with forest restoration. However, both mean concentration and annual output fluxes of DOC in surface runoff were the highest in the deciduous broadleaved forest at the intermediate restoration stage. The concentrations were closely related to surface runoff, decomposition rate of litterfall, and soil organic matter content. The annual output fluxes of DOC and TDN in surface runoff were less than 30% of the input in throughfall, indicating nutrient accumulation in subtropical secondary forests.