81. 题目: Enhanced bioavailability of dissolved organic matter (DOM) in human-disturbed streams in Alpine fluvial networks
作者: Thibault Lambert, Pascal Perolo, Nicolas Escoffier, Marie-Elodie Perga
摘要: The influence of human activities on the role of inland waters in the global carbon (C) cycle is poorly constrained. In this study, we investigated the impact of human land use on the sources and biodegradation of dissolved organic matter (DOM) and its potential impact on bacterial respiration in 10 independent catchments of the Lake Geneva basin. Sites were selected along a gradient of human disturbance (agriculture and urbanization) and were visited twice during the winter high-flow period. Bacterial respiration and DOM bioavailability were measured in the laboratory through standardized dark bioassays, and the influence of human land uses on DOM sources, composition and reactivity was assessed from fluorescence spectroscopy. Bacterial respiration was higher in agro-urban streams but was related to a short-term bioreactive pool (0–6 d of incubation) of autochthonous origin, whose relative contribution to the total DOM pool increased with the degree of human disturbance. On the other hand, the degradation of a long-term (6–28 d) bioreactive pool related to terrestrial DOM was independent from the catchment land use and did not contribute substantially to aquatic bacterial respiration. From a greenhouse gas emission perspective, our results suggest that human activities may have a limited impact on the net C exchanges between inland waters and the atmosphere, as most CO2 fixed by aquatic producers in agro-urban streams is cycled back to the atmosphere after biomineralization. Although seasonal and longitudinal changes in DOM sources must be considered, the implications of our results likely apply more widely as a greater proportion of autochthonous-DOM signature is a common feature in human-impacted catchments. Yet, on a global scale, the influence of human activities remains to be determined given the large diversity of effects of agriculture and urbanization on freshwater DOM depending on the local environmental context.
82. 题目: Relations between soil organic carbon content and the pore size distribution for an arable topsoil with large variations in soil properties
期刊: European Journal of Soil Science
作者: Jumpei Fukumasu, Nick Jarvis, John Koestel, Thomas Kätterer, Mats Larsbo
摘要: Soil organic carbon (SOC) in arable topsoil is known to have beneficial effects on soil physical properties that are important for soil fertility. The effects of SOC content on soil aggregate stability have been well documented; however, few studies have investigated its relationship with the soil pore structure, which has a strong influence on water dynamics and biogeochemical cycling. In the present study, we examined the relationships between SOC and clay contents and pore size distributions across an arable field with large spatial variations in topsoil SOC and clay contents by combining X-ray tomography and measurements of soil water retention. Additionally, we investigated the relationships between fractionated SOC, reactive Fe and Al oxide contents and soil pore structure. We found that porosities in the 0.2 – 720 μm diameter class were positively correlated with SOC content. A unit increase of SOC content was associated with a relatively large increase in porosity in the 0.2 – 5 and 480 – 720 μm diameter classes, which indicates that enhanced SOC content would increase plant available water content and unsaturated hydraulic conductivity. On the other hand, macroporosities (1200 – 3120 μm diameter classes) and bioporosity were positively correlated with clay content but not with SOC content. Due to strong correlations between soil texture, carbon to nitrogen ratios and reactive iron contents, we could not separate the relative importance of these soil properties for pore size distributions. Reactive aluminum and particulate organic carbon contents were poorer predictors for pore size distributions compared to clay and SOC contents. This study provide new insights on the relations between SOC in an arable soil and soil pore structure and may lead to improved estimations of the effects of enhanced SOC sequestration on soil water dynamics and soil water supply to crops.
83. 题目: Optimizing residue and tillage management practices to improve soil carbon sequestration in a wheat–peanut rotation system
期刊: Journal of Environmental Management
作者: Jihao Zhao, Zhaoxin Liu, Huajiang Lai, Dongqing Yang, Xiangdong Li
摘要: The sustainable development of agriculture has been challenged by the decline of soil quality and the change of climate. It is well known that soil carbon (C) sequestration plays crucial roles in improving soil structural stability, mitigating greenhouse emissions, and promoting plant nutrient supply. Therefore, a 3-year field experiment was conducted to evaluate the effects of different residue and tillage management practices on soil C sequestration in a wheat–peanut rotation system. Four treatments were studied: moldboard plow tillage with wheat residue returning (PTS), rotary tillage with wheat residue returning (RTS), no tillage with wheat residue mulching (NTS), and no tillage with wheat residue removal (NT). Our results indicated that residue return favored the improvement of soil C sequestration capacity relative to residue removal. In addition, NTS improved soil C sequestration in the surface soil layer (0–5 cm), but markedly reduced soil C sequestration in the deeper soil layers (5–30 cm). NTS thus caused a more obvious soil stratification phenomenon, which was not conducive to improving soil quality. At the 5–30 cm soil depths, the soil labile organic C fractions concentrations, carbon pool management index (CPMI), macroaggregates-associated C storage, intra-aggregate C fractions concentrations, and soil total organic carbon (TOC) storage under PTS were all higher than those under other treatments. Overall, a peanut strategic cultivation management mode that combines moldboard plow tillage and wheat residue return may be used as a reference for optimizing agricultural soil management to achieve the improvement of soil C sequestration capacity in a wheat–peanut rotation system.
84. 题目: Pool complexity and molecular diversity shaped topsoil organic matter accumulation following decadal forest restoration in a karst terrain
期刊: Soil Biology and Biochemistry
作者: Shuotong Chen, Xiao Feng, Qingmei Lin, Chun Liu, Kun Cheng, Xuhui Zhang, Rongjun Bian, Xiaoyu Liu, Yan Wang, Marios Drosos, Jufeng Zheng, Lianqing Li, Genxing Pan
摘要: Fast accumulation of soil organic matter (SOM) following forest restoration shifted from cropland has been widely reported, but how the pools and molecular composition changed across soil aggregate fractions remains unclear. In this study, undisturbed topsoil (0–10 cm) samples were collected across a decadal chronosequence of forest stands (RL10, RL20 and RL40) restored for 10, 20 and 40 years following maize cropland (CL) abandonment in a karst terrain of Guizhou, Southwest China. SOM changes were explored using the size and density fractionation of water-stable aggregates, 13C isotopic signalling and biomarker analyses as well as 13C solid-state NMR assays. Compared to that of CL, SOM content was increased by 24%, 79% and 181%, mass proportion of macroaggregates increased by 136%, 179% and 250%, and particulate organic matter (POM) increased by 13%, 108% and 382%, respectively at RL10, RL20 and RL40. With biomarker analyses, the relative abundances of plant-derived organics (lignin, cutin, suberin, wax and phytosterols), mostly protected in aggregates, increased, while those of microbe-derived OC, predominantly mineral bound, decreased in response to prolonged forest restoration. Calculated as per the Shannon diversity index (H’), changes in SOM pool complexity and molecular diversity were parallel to the SOM accumulation trend. The pool size ratio of POM to MAOM (mineral-associated organic matter) and the molecular abundance ratio of PL (plant-derived lipids) to ML (microbe-derived lipids) appeared to be indicative of SOM accumulation following forest restoration. With prolonged forest restoration, the topsoil OM shifted from microbial MAOM dominance to plant-derived POM dominance. Furthermore, the great topsoil OM enhancement in restored forest stands was shaped by pool complexity and molecular diversity changes with the complex interactions among plant-microbial-mineral assemblages in the karst topsoil. Both the pool complexity and molecular diversity of SOM should be considered in addressing carbon sequestration with forest restoration concerning the functioning of soil ecosystems and services under global change pressures.
85. 题目: Algae-derived metal-free boron-doped biochar as an efficient bioremediation pretreatment for persistent organic pollutants in marine sediments
期刊: Journal of Cleaner Production
作者: Chang-Mao Hung, Chiu-Wen Chen, Chin-Pao Huang, Jia-Wei Cheng, Cheng-Di Dong
摘要: Aquatic systems are important sinks of persistent organic pollutants (POPs), such as polycyclic aromatic hydrocarbons (PAHs). In this study, boron-doped biochar (B-BAB) was prepared from pristine brown algae (Sargassum duplicatum) and boric acid using a facile pyrolysis method. The B-BAB was then used as catalyst for the activation of peroxymonosulfate (PMS) for bioremediation-based sediment decontamination. The effect of catalyst dosage and initial pH of the B-BAB/PMS system on PAH removal were studied. At an initial pH of 3.0, 93% of the PAH was degraded within 12 h in the presence of 1.0 g/L of B-BAB and 1 × 10−4 M of PMS, while the removal of 2-, 3-, 4-, 5-, and 6-ring PAHs was 53, 86, 81, 83, and 91%, respectively. Results demonstrated that B-BAB has superior catalytic capacity for PMS activation and significantly improved the efficacy of PAH removal. Interaction between boric and nitrogen species on the graphitized carbon framework, through the primary radical (SO4•– and HO•) and nonradical (1O2) reactions in the B-BAB/PMS system was key to efficient PAHs removal. High PAH removal capability and favorable changes in benthic bacterial communities of the B-BAB/PMS process suggested that PMS-advanced oxidation process (AOP) treatment enhanced the biological richness and microbiota diversity of the sediments, which were initially dominated by Proteobacteria and Epsilonbacteraeota, including genera related to Woeseia and Sulfurovum. Overall, the present study significantly expanded knowledge on the metal-free nature of carbocatalysis-boosting B-BAB/PMS removal of POPs. The B-BAB/PMS system may be useful to realizing the application of green technologies for future water environment bioremediation campaigns.
86. 题目: Discovery of Polar Ozonation Byproducts via Direct Injection of Effluent Organic Matter with Online LC-FT-ICR-MS
期刊: Environmental Science & Technology
作者: Elaine Jennings, Arina Kremser, Limei Han, Thorsten Reemtsma, Oliver J. Lechtenfeld
摘要: Effluent organic matter (EfOM), a major ozone consumer during wastewater ozonation, is a complex mixture of natural and anthropogenic organic molecules. Ozonation of EfOM adds to molecular complexity by introducing polar and potentially mobile ozonation byproducts (OBPs). Currently, nontargeted direct infusion (DI) ultrahigh resolution mass spectrometry (e.g. FT-ICR-MS) is used to study OBPs but requires sample extraction, limiting the accessible polarity range of OBPs. To better understand the impact of ozonation on EfOM and the formation of polar OBPs, nonextracted effluent was analyzed by direct injection onto a reversed-phase liquid chromatography system (RP-LC) online hyphenated with an FT-ICR-MS. Over four times more OBPs were detected in nonextracted EfOM compared to effluent extracted with solid phase extraction and measured with DI-FT-ICR-MS (13817 vs 3075). Over 1500 highly oxygenated OBPs were detected exclusively in early eluting fractions of nonextracted EfOM, indicating polar OBPs. Oxygenation of these newly discovered OBPs is higher than previously found, with an average molecular DBE-O value of −3.3 and O/C ratio of 0.84 in the earliest eluting OBP fractions. These polar OBPs are consistently lost during extraction but may play an important role in understanding the environmental impact of ozonated EfOM. Moreover, 316 molecular formulas classified as nonreactive to ozone in DI-FT-ICR-MS can be identified with LC-FT-ICR-MS as isomers with varying degrees of reactivity, providing for the first time experimental evidence of differential reactivity of complex organic matter isomers with ozone.
87. 题目: Legacy Effects of Sorption Determine the Formation Efficiency of Mineral-Associated Soil Organic Matter
期刊: Environmental Science & Technology
作者: Shuling Chen, Thimo Klotzbücher, Oliver J. Lechtenfeld, Hanlie Hong, Chongxuan Liu, Klaus Kaiser, Christian Mikutta, Robert Mikutta
摘要: Sorption of dissolved organic matter (DOM) is one major pathway in the formation of mineral-associated organic matter (MOM), but there is little information on how previous sorption events feedback to later ones by leaving their imprint on mineral surfaces and solutions (“legacy effect”). In order to conceptualize the role of legacy effects in MOM formation, we conducted sequential sorption experiments with kaolinite and gibbsite as minerals and DOM derived from forest floor materials. The MOM formation efficiency leveled off upon repeated addition of identical DOM solutions to minerals due to the retention of highly sorptive organic molecules (primarily aromatic, nitrogen-poor, hydrogen-poor, and oxygen-rich molecules), which decreased the sorption site availability and simultaneously modified the mineral surface charge. Organic–organic interactions as postulated in multilayer models played a negligible role in MOM formation. Continued exchange between DOM and MOM molecules upon repeated sorption altered the DOM composition but not the MOM formation efficiencies. Sorption-induced depletion of high-affinity compounds from solutions further decreased the MOM formation efficiencies to pristine minerals. Overall, the interplay between the differential sorptivities of DOM components and the mineral surface chemistry explains the legacy effects that contribute to the regulation of fluxes and the distribution of organic matter in the soil.
88. 题目: Microplastic effects on soil system parameters: a meta-analysis study
期刊: Environmental Science and Pollution Research
作者: Haixiao Li, Le Liu, Yan Xu, Junyang Zhang
摘要: Microplastics are generally considered as an emerging contaminant in the environment due to their toxic additives and transport of other contaminants. However, the potential threats of microplastics in soil should be concerned due to inconsistent research results. In this study, a meta-analysis based on 32 recent relevant studies was conducted to compare the response of soil system parameters including microbial community, aggregate structure, soil nutrient contents, and crop growth to the presence of microplastics. The results showed that microplastics presented no significant effects on soil dissolved organic carbon contents and the amounts of available phosphate, nitrate, and ammonium. Although microplastics would not significantly influence the diversity of soil microorganisms, they could significantly increase soil microorganism amounts with a standard mean difference at 19.32. We also found that microplastics tended to significantly decrease soil water stable macro-aggregate (> 0.25 mm) contents with a significantly negative standard mean difference (− 0.90) in meta-analysis. Moreover, soil microplastics seemed not to affect crop growth by having non-significant effects on both crop under-ground and above-ground biomasses. These results indicate that up to date, the main negative impacts caused by microplastics on soil systems could be their negative functions on soil aggregation.
89. 题目: Effect of humic and calcareous substance amendments on the availability of cadmium in paddy soil and its accumulation in rice
期刊: Ecotoxicology and Environmental Safety
作者: Hao Liu, Tuo Zhang, Yan’an Tong, Qihong Zhu, Daoyou Huang, Xibai Zeng
摘要: Humic substances (HS) are widely known as important components in soil and significantly affect the mobility of metals due to their large surface area and abundant organic functional groups. Calcareous substances (CSs) are also commonly used as robust and cost-effective amendments for increasing the pH of acidic soils and decreasing the mobility of metals in soils. In this study, we developed a new remediation scheme for cadmium (Cd)-contaminated soil remediation by coupling HS and CS. The results showed that regardless of the addition of fulvic acid (FA), all the CS-containing treatments significantly increased the soil pH by 0.32–0.60, and the concentration of bioavailable Cd decreased in the moderately (field experiment soil, maximum 62%) and highly (pot experiment soil, maximum 57%) Cd-contaminated soils. The Cd content in rice (Oryza sativa L.) tissues significantly decreased after all the treatments. The bioaccumulation factors (BAFs) decreased by over 50% in the roots, stems, leaves and husks in all treatments, while the translocation factors (TFs) only significantly decreased in the highly contaminated soil. Among all treatments, the two HS+CS treatments (FA+CaCO3 and FA+CaO) had the greatest effect on decreasing the concentration of bioavailable Cd in soil and Cd in brown rice grains. The suggested mechanism for the effectiveness of coupled HS and CS was that CS first mitigated the pH and precipitated Cd, followed by a complexation effect between HS and Cd. Although the Cd in rice grains in both cases was higher than the standard limit, HS+CS remediation can be advocated as a robust, simple and cost-effective scheme for Cd remediation if the additive dose is slightly increased, as this approach can simultaneously improve the pH of acidic soil and adsorb Cd in soil.
90. 题目: Bioremoval of PVP-coated silver nanoparticles using Aspergillus niger: the role of exopolysaccharides
期刊: Environmental Science and Pollution Research
作者: Ola M. Gomaa, Amar Yasser Jassim, Anindya Chanda
摘要: Extensive use of engineered nanoparticles has led to their eventual release in the environment. The present work aims to study the removal of Polyvinylpyrrolidone-coated silver nanoparticles (PVP-Ag-NPs) using Aspergillus niger and depict the role of exopolysaccharides in the removal process. Our results show that the majority of PVP-Ag-NPs were attached to fungal pellets. About 74% and 88% of the PVP-Ag-NPs were removed when incubated with A. niger pellets and exopolysaccharide-induced A. niger pellets, respectively. Ionized Ag decreased by 553 and 1290-fold under the same conditions as compared to stock PVP-Ag-NP. PVP-Ag-PVP resulted in an increase in reactive oxygen species (ROS) in 24 h. Results show an increase in PVP-Ag-NPs size from 28.4 to 115.9 nm for A. niger pellets and 160.3 nm after removal by stress-induced A. niger pellets and further increased to 650.1 nm for in vitro EPS removal. The obtained findings show that EPS can be used for nanoparticle removal, by increasing the net size of nanoparticles in aqueous media. This will, in turn, facilitate its removal through conventional filtration techniques commonly used at wastewater treatment plants.
91. 题目: Exploring the influence of concentration fluctuation and matrix effects on a passive sampler of triolein-embedded cellulose acetate membrane measuring polychlorinated biphenyls in water
期刊: Environmental Science and Pollution Research
作者: Peng Zhang, Linke Ge, Yiping Xu, Ting Yao, Ying Bian, Dongxing Zhou, Xiaozhong Gao
摘要: A membrane of triolein-embedded cellulose acetate membrane (TECAM), as an integrative passive sampler, was applied to adsorb 28 polychlorinated biphenyls (PCBs) from pure water and sea water in order to probe into the influence of concentration fluctuation and water matrix. The results demonstrated the temporal variations of PCBs concentrations in TECAM followed the first-order kinetics model. The periodic refreshment of solution and matrix effects of sea water significantly prolonged the time that PCBs reached equilibrium stage. The refreshment facilitated the uptake mass in TECAM. On the contrary, the matrix effects of sea water and dissolved organic matter (DOM) declined the PCBs absorption to TECAM. The average logKP values of PCBs in pure water were about 1.2 log unit higher than those in sea water in the experiments that the solution was not refreshed, while the difference of average logKP values narrowed to 0.3 log unit if the PCBs solutions were periodically refreshed. The correlation between logKP and logKOW values fitted the quadratic curve well, which was similar to semi-permeable membrane device (SPMD). The appropriate sampling times (t94%) ranged from 98.8 to 819 h (mean 500 h) for pure water with refreshment, much longer than those in sea water with refreshment (80.1~410 h, mean 189 h). The t94% values in the solution with high DOM content increased significantly, up to 409 h. Furthermore, comparing the two experiments that the spiked pure water and sea water solution were refreshed frequently, the estimated sampling rates (Rs) in pure water (0.154~2.06 L/day with a mean value of 0.605 L/day) were slightly lower than those in sea water (0.292~3.84 L/day with a mean value of 1.69 L/day). However, the Rs values in sea water with DOM declined sharply to 0.042 L/day. Therefore, concentration fluctuation, matrix effect, and DOM contents of sea water evidently posed significant influence on dynamic parameters of TECAM absorption, which would be screened and probed detailed in future.
92. 题目: Vertically divergent responses of SOC decomposition to soil moisture in a changing climate
期刊: Journal of Geophysical Research: Biogeosciences
作者: Marleen Pallandt, Bernhard Ahrens, Sujan Koirala, Holger Lange, Markus Reichstein, Marion Schrumpf, Sönke Zaehle
摘要: The role of soil moisture for organic matter decomposition rates remains poorly understood and underrepresented in Earth System Models (ESMs). We apply the Dual Arrhenius Michaelis-Menten (DAMM) model to a selection of ESM soil temperature and moisture outputs to investigate their effects on decomposition rates, at different soil depths, for a historical period and a future climate period. Our key finding is that the inclusion of soil moisture controls has diverging effects on both the speed and direction of projected decomposition rates (up to ± 20%), compared to a temperature-only approach. In the top soil, the majority of these changes is driven by substrate availability. In deeper soil layers, oxygen availability plays a relatively stronger role. Owing to these different moisture controls along the soil depth, our study highlights the need for depth-resolved inclusion of soil moisture effects on decomposition rates within ESMs. This is particularly important for C-rich soils in regions which may be subject to strong future warming and vertically opposing moisture changes, such as the peat soils at northern high latitudes.
93. 题目: Pyrite-mediated advanced oxidation processes: applications, mechanisms, and enhancing strategies
期刊: Water Research
作者: Biao Song, Zhuotong Zeng, Eydhah Almatrafi, Maocai Shen, Weiping Xiong, Chengyun Zhou, Wenjun Wang, Guangming Zeng, Jilai Gong
摘要: Proper treatment of wastewater is one of the key issues to the sustainable development of human society, and people have been searching for high-efficiency and low-cost methods for wastewater treatment. This article reviews recent studies about pyrite-mediated advanced oxidation processes (AOPs) in removing refractory organics from wastewater. The basic information of pyrite and its characteristics for AOPs are first introduced. Then, the performance and mechanisms of pyrite-mediated Fenton oxidation, electro-Fenton oxidation, and persulfate oxidation processes are carefully reviewed and presented. Natural pyrite is an abundant low-cost heterogeneous catalyst for AOPs, and the slow release of Fe2+ and the self-regulation of solution pH are highlighted characteristics of pyrite-mediated AOPs. In AOPs, the interaction between Fe3+ and pyrite facilitates the Fe2+ regeneration and the Fe2+/Fe3+ cycle. Making pyrite into nanoparticles, assisting by ultrasound and light irradiation, and adding exogenous Fe3+, organic chelating agents, or biochar is effective to enhance the performance of pyrite-mediated AOPs. Based on the analyses of those pyrite-mediated AOPs and their enhancing strategies, the future development directions are proposed in the aspects of toxicity research, mechanism research, and technological coupling.
94. 题目: Characteristics and chlorine reactivity of biochar-derived dissolved organic matter: Effects of feedstock types and pyrolysis temperatures
期刊: Water Research
作者: Li-Ping Li, Yu-Hui Liu, Dong Ren, Jun-Jian Wang
摘要: Increasing biochar application worldwide may release more biochar-derived dissolved organic matter (BDOM) to the source water for drinking water supply. However, it is unclear how feedstock types and pyrolysis temperatures for biochar production would affect the characteristics and chlorine reactivity of BDOM. Here, we studied the spectroscopic characteristics of BDOM pyrolyzed from pine needle, wheat straw, walnut shells, alfalfa, pig manure, and sludge derived biochars at 300, 500, and 700°C, as well as the formation potential of disinfection byproducts (DBPs) and their bulk toxicity after BDOM chlorination. The N/C ratio of biochar was higher for N-rich than C-rich feedstocks. Optical analyses indicated that BDOM aromaticity was highest at 700°C, while the impact of pyrolysis temperature on the molecular weight of BDOM varied greatly among feedstocks. Increasing pyrolysis temperature caused consistently decreased BDOM reactivity toward haloketone formation but did not show consistent impacts on the other DBPs. Among feedstocks, the N-rich sludge showed the highest specific haloacetonitrile formation potential of BDOM at any given pyrolysis temperature. The DBP formation potential from biochar was consistently highest at 300 °C and was higher for N-rich than C-rich feedstocks. The microtoxicity of DBP mixture was highest for the BDOM derived from sludge produced at 300°C. This study highlights the high variations in characteristics and chlorination reactivity of BDOM with varying feedstocks and pyrolysis temperatures, which implies that more attention should be paid to the environmental impacts of the intensive application of low-temperature biochar from nitrogen-rich feedstock such as sludge.
95. 题目: Enhanced anaerobic digestion of tar solution from rice husk thermal gasification with hybrid upflow anaerobic sludge-biochar bed reactor
期刊: Bioresource Technology
作者: Haiyuan Ma, Yong Hu, Jiang Wu, Takuro Kobayashi, Kai-Qin Xu, Hidetoshi Kuramochi
摘要: Tar generated as a by-product during biomass gasification contains a high concentration of refractory organic matters. In this study, a hybrid upflow anaerobic sludge-biochar bed reactor was established for tar treatment, and the methane yield was 120-154 NmL-CH4/g-CODinf, 20-30% higher than the control reactor. COD removal and methane production significantly decreased in both reactors when the influent tar concentration was doubled from 4954 mg-COD/L to 9964 mg-COD/L. When the influent concentration was reduced, the biochar packed reactor showed a faster recovery. Batch tests confirmed that higher tar concentration inhibited methane production and induced longer lagphase. Biochar addition effectively relieved the inhibition and prolonged the retention of organic matters. SEM observation and 16S rRNA analysis suggested that biochar also acted as the microbe’s carrier, and promoted the growth of some microbes. The results of this study provide new ideas for tar treatment.
96. 题目: Lignin preservation and microbial carbohydrate metabolism in permafrost soils
期刊: Journal of Geophysical Research: Biogeosciences
作者: Thao Thi Dao, Robert Mikutta, Leopold Sauheitl, Norman Gentsch, Olga Shibistova, Birgit Wild, Jörg Schnecker, Jiří Bárta, Petr Čapek, Antje Gittel, Nikolay Lashchinskiy, Tim Urich, Hana Šantrůčková, Andreas Richter, Georg Guggenberger
摘要: Permafrost-affected soils in the northern circumpolar region store more than 1,000 Pg soil organic carbon (OC), and are strongly vulnerable to climatic warming. However, the extent to which changing soil environmental conditions with permafrost thaw affects different compounds of soil organic matter (OM) is poorly understood. Here, we assessed the fate of lignin and non-cellulosic carbohydrates in density fractionated soils (light fraction, LF vs. heavy fraction, HF) from three permafrost regions with decreasing continentality, expanding from east to west of northern Siberia (Cherskiy, Logata, Tazovskiy, respectively). In soils at the Tazovskiy site with thicker active layers, the LF showed smaller OC-normalized contents of lignin-derived phenols and plant-derived sugars and a decrease of these compounds with soil depth, while a constant or even increasing trend was observed in soils with shallower active layers (Cherskiy and Logata). Also in the HF, soils at the Tazovskiy site had smaller contents of OC-normalized lignin-derived phenols and plant-derived sugars along with more pronounced indicators of oxidative lignin decomposition and production of microbial-derived sugars. Active layer deepening, thus, likely favors the decomposition of lignin and plant-derived sugars, i.e. lignocelluloses, by increasing water drainage and aeration. Our study suggests that climate-induced degradation of permafrost soils may promote carbon losses from lignin and associated polysaccharides by abolishing context-specific preservation mechanisms. However, relations of OC-based lignin-derived phenols and sugars in the HF with mineralogical properties suggest that future OM transformation and carbon losses will be modulated in addition by reactive soil minerals.
97. 题目: Effects of biochar and N-stabilizers on greenhouse gas emissions from a subtropical pasture field applied with organic and inorganic nitrogen fertilizers
期刊: Journal of Environmental Management
作者: Joseph Elias Rodrigues Mikhael, Jim J. Wang, Syam Dodla, Guillermo Scaglia, Sanku Dattamudi
摘要: Pasturelands contribute significantly to the global CO2, CH4 and N2O emissions. These gas emissions are influenced by the amount and type of N-fertilizers applied and local climate. Recent studies showed potential of biochar and N-stabilizer compounds in minimizing CO2, CH4 and N2O emissions by regulating N-release from N-fertilizers. The present study was aimed at determining and comparing the effects of biochar and N-(n-butyl) thiophosphoric triamide + dicyandiamide (N-stabilizer) on CO2, N2O and CH4 emissions from a pasture fertilized with cattle manure or urea. The study was conducted during 2015 and 2016 in an established bermudagrass (Cynodon dactylon L. Pers.). Treatments consisted of combination of N-sources (manure, and urea) and two mitigation technologies [pine hardwood biochar (BC) and N-stabilizer] along with control. Emissions of GHGs were measured from each plot using static chamber systems. Both BC and N-stabilizer applications with manure applied to the hay field significantly decreased N2O emissions by 42% and 45%, respectively, in the year-2, and emission factors compared to manure only treatment. Addition of N-stabilizer to urea had significantly decreased N2O emissions compared to urea alone, while BC had statistically insignificant effect although numerically lowered N2O emissions in both the years. Application of manure to the soil resulted in significantly higher CO2 emissions in both years and CH4 emissions in 2016 compared to unfertilized soil. Urea application had significant effect on CO2 emissions in 2016, while no effect on CH4 emissions compared to control. Application of either biochar or N-stabilizer did not significantly affect CO2 and CH4 emissions.
98. 题目: Molecular and stable isotope analysis (δ13C, δ2H) of sedimentary n-alkanes in the St. Lawrence Estuary and Gulf, Quebec, Canada: importance of even numbered n-alkanes in coastal systems
期刊: Organic Geochemistry
作者: Anic Imfeld, Alexandre Ouellet, Peter Douglas, Gregor Kos, Yves Gélinas
摘要: Sediments comprise a multitude of inorganic and organic components, with much of the composition of the organics still not fully characterized. Our research targeted n-alkanes, to determine whether compound specific carbon and hydrogen isotope analysis allows for their source identification in coastal sediments. Here, we map the current abundances and sources of straight chain n-alkanes in sediments of the St. Lawrence Estuary and Gulf using molecular (diagnostic ratios) and isotopic fingerprinting (δ13C, δ2H). n-Alkane abundances (117.11 ± 1.61 to 418.64 ± 70.20 µg/g OC), carbon preference index (CPI; 1.95 ± 0.05 to 5.09 ± 0.10), average chain length (ACL; 28.36 ± 0.02 to 28.97 ± 0.01), proportion of aquatic submerged plants and terrestrial plant inputs (Paq; 0.295 ± 0.003 to 0.377 ± 0.002), terrigenous aquatic ratio (TAR; 3.43 ± 0.16 to 7.99 ± 0.05), and n-alkane ratio (NAR; 0.169 ± 0.011 to 0.584 ± 0.011) values varied along the terrestrial-marine continuum. Large differences in the concentration weighted average (WA) δ13C and δ2H for odd and even n-alkanes were found, with WA δ13C ranging from -30.9 ± 0.3 to -33.4 ± 0.09 ‰ and -28.8 ± 0.01 to -32.3 ± 0.2 ‰, respectively, and 165.6 ± 3.6 to -200.8 ± 2.4 ‰ and -96.0 ± 2.8 to -158.7 ± 2.1 ‰ for δ2H. The diagnostic ratios were shown to misrepresent the input sources of organic matter (OM) and were inaccurate as source indicators when more than one OM source was present. With the addition of compound specific δ13C and δ2H analysis of n-alkanes, it was determined that the n-alkanes were predominantly derived from natural, rather than anthropogenic sources, with variations being driven by geographic changes in vegetation type and differing ratios of terrestrial and marine OM inputs. Importantly, compound specific isotope analysis of the even numbered n-alkanes would permit identification and tracking of petroleum-derived contaminants. Molecular data alone are ineffective for this, owing to the similarity in CPI values for petroleum-derived contaminants and highly degraded OM which is discharged by the St. Lawrence River into the estuary.
99. 题目: Soil properties and substrate quality determine the priming of soil organic carbon during vegetation succession
期刊: Plant and Soil
作者: Youchao Chen, Weipeng Li, Yong You, Chen Ye, Xiao Shu, Quanfa Zhang, Kerong Zhang
摘要: Purpose There is an increasing recognition that the priming effect (PE) induced by fresh organic matter (FOM) may greatly influence soil organic carbon (SOC) dynamics. However, the patterns of PE induced by substrates with different quality on soils from vegetation succession, as well as the underlying mechanisms, are still unclear. Methods We conducted a field investigation to explore the changes in soil properties and SOC stocks along a secondary vegetation succession (cropland → shrubland → forest); then, we examined the patterns of PE by incubating FOMs with soils from the different succession stages. The added FOMs included 13C-labeled glucose (GLU) as well as labile organic matter (LOM) and recalcitrant organic matter (ROM) extracted from 13C-labeled maize leaves. Results Increases in SOC stock and changes in soil properties were detected during the process of vegetation succession. FOMs with contrasting quality caused PEs in different magnitudes, with a higher PE generated after the GLU and LOM treatments compared with ROM. We also detected a higher soil fungi/bacteria (F/B) with ROM than the GLU and LOM treatment. Under a given substrate treatment, PE was generally higher on cropland soil than shrubland and forest soil. The variations of PE among succession stages were negatively correlated with soil aggregate stability, total inorganic nitrogen, and available phosphorus and positively correlated with pH and F/B ratio. Conclusions Soil properties and substrate quality determine the PE in soils from vegetation succession. The PE might be one of the potential mechanisms underlying soil C dynamics during the vegetation succession.
100. 题目: Atmospheric oxygen abundance, marine nutrient availability, and organic carbon fluxes to the seafloor
期刊: Global Biogeochemical Cycles
作者: Devon B. Cole, Kazumi Ozaki, Christopher T. Reinhard
摘要: The global-scale oxygenation of Earth’s surface represents one of the most fundamental chemical transformations in our planet’s history. There is empirical and theoretical evidence for at least two distinct and stable regimes of Earth surface oxygenation—a ‘low-O2 world’ characterized by pervasively anoxic deep ocean waters, and a ‘high-O2 world’ with dominantly well-oxygenated deep ocean waters represented by our modern surface environment. Numerous biogeochemical processes and feedbacks control the redox state of the marine system, particularly when considered globally and on geologic timescales. It has therefore proven challenging to provide quantitative and internally consistent estimates of the atmospheric oxygen levels (and thereby, productivity, nutrient availability, and reductant consumption) necessary to oxygenate the deep seas. Here, we leverage an Earth-system biogeochemical model that tracks the carbon, nitrogen, oxygen, phosphorus, and sulfur cycles (CANOPS) to provide new quantitative constraints on this relationship. We explore ocean biogeochemistry and fluxes of reduced carbon to the seafloor across a wide range of atmospheric oxygen levels from 0.01 – 100% of the present atmospheric level (PAL), and implement a stochastic approach to provide formal estimates of uncertainty on our results. We find that deep ocean waters remain largely anoxic, and ocean productivity remains significantly muted relative to the modern marine biosphere, until pO2 levels reach ∼40% PAL. These results have major implications for quantitative constraints on atmospheric pO2 levels during the latest Proterozoic and Paleozoic, both in terms of environmental habitability for early animals and with respect to potential energetic constraints on growing and diversifying benthic communities.