论文检索 |
|||||
|
总访问量：6124319次 总访客量：491968人 | |||||
| 关键词:... | |||||
| 期刊：... | |||||
所有论文 |
|||||
24201. 题目: What is the impact of pasture reform on organic carbon compartments and CO2 emissions in the Brazilian Cerrado? The emission of CO2 from the soil in agricultural areas is the result of the interaction of several factors, including soil and crop management practices and local edaphoclimatic conditions. The dynamics of organic carbon (OC), in the midst of reform processes in agricultural areas, can be used as an indicator of chemical soil quality because carbon loss is directly related to its lability, quality, or decomposition capacity. This study aimed to evaluate the impact of the reform of degraded pastures in the soil organic matter compartment and its effect on mitigating CO2 emissions. The study was carried out in the municipality of Selvíria, Mato Grosso do Sul, Brazil, in two areas destined for extensive beef cattle grazing, subsidized by the forage plant Urochloa brizantha cv. Marandu. Geostatistical meshes were installed in the areas, and soil samples of deformed and undeformed structures were taken to evaluate the physical and chemical attributes of the soil. The results indicated that soil management practices, followed by the cultivation of sorghum intercropped with U. brizantha, increased the total OC (TOC) stocks through the stable fraction (OC associated with the mineral fraction) and consequent reduction in CO2 emissions from the soil. This highlights the spatial variability in CO2 emissions and how soil attributes affect the flow of CO2 into the atmosphere. The use of multivariate geostatistics has made it possible to forecast CO2 emissions from the soil. This small-scale study provides a theoretical basis for the large-scale spatial monitoring of biogeochemical processes that control CO2 emissions in agricultural ecosystems, particularly in degraded pasture areas. | |||||
24202. 题目: Contrasting impacts of manure and inorganic fertilizer applications for nine years on soil organic carbon and its labile fractions in bulk soil and soil aggregates Careful nutrient management to increase soil organic carbon (SOC) content is important in increasing agricultural productivity and maintaining ecosystem health. A field experiment was conducted for nine years to investigate the effects of manure (M) and inorganic fertilizer (NPK) on SOC and its labile fractions within the bulk soil and in soil aggregates in a wheat-maize rotation on the North China Plain. Nine treatments were included: control (CK) with no fertilization, cattle manure (M, applied at rates of 3000, 6000, 9000, and 12,000 kg ha−1 crop−1), and inorganic NPK fertilizer applied to give equivalent rates of N, P and K. Straw was returned to all plots. Results showed that fertilization significantly increased SOC sequestration and the concentrations of SOC and labile SOC fractions (cold water - extractable SOC, hot water-extractable SOC, microbial biomass C, and dissolved organic C within the bulk soil and soil aggregates). The values increased with increasing application rate of manure but not with increasing NPK fertilizer rate. The differences between manure and NPK fertilizer were apparent at rates equivalent to 9000 and 12,000 kg manure ha−1. Labile SOC fractions were linearly correlated with SOC within the bulk soil and aggregates and hot water-extractable C was the labile C fraction most sensitive to changes in SOC content. Aggregate stability was significantly positively correlated with SOC content and its labile fractions in both bulk soil and aggregates. The results indicate that straw return and/or combined application of fertilizers and manures may be feasible in achieving the '4 per 1000' initiative, with manure application particularly effective. Manure application at a rate of 9000 kg ha−1 crop−1 may be the optimum strategy to sequester C and maintain high crop productivity. Periodic high application rates of manures should be integrated with appropriate inorganic fertilizer application rates to optimize nutrient management strategies on calcareous soils. | |||||
24203. 题目: Effects of Biochar on Microalgal Growth: Difference between Dissolved and Undissolved Fractions | |||||
24204. 题目: Organo-mineral interactions and soil carbon mineralizability with variable saturation cycle frequency The response of mineral-stabilized soil organic carbon (SOC) to environmental change is a source of uncertainty in the understanding of SOC cycling. Fluctuating wet-dry cycles and associated redox changes in otherwise well-drained soils may drive mineral dissolution, organic carbon (OC) mobilization, and subsequent OC mineralization. However, the extent to which rapid fluctuations between water-saturated and unsaturated conditions (i.e., flashy conditions) result in long-term changes in mineral composition and organo-mineral interactions is not well understood. In this study, the effect of variable saturation frequency on soil mineral composition, mineral-associated OC, and OC mineralizability was tested using selective dissolution, bulk spectroscopy, microscale imaging, and aerobic-anaerobic incubation experiments. Previous water table fluctuation measurements and diagnostic profile characteristics at Hubbard Brook Experimental Forest (NH) were used to identify soils with high, medium, and low saturation frequency regimes (defined by historical water table cycling frequency; i.e., water table presence and recession in the upper B horizon). We found the amount of OC released during extractions targeting non-crystalline minerals was of similar magnitude as extracted iron (Fe) in lower saturation frequency soils. However, the magnitude of extracted OC was 2.5 times greater than Fe but more similar to extractable aluminum (Al) in higher saturation frequency soils. Bulk soil Fe was spatially more strongly correlated to soil organic matter (SOM) in lower saturation frequency soils (Spearman Rank rs = 0.62, p < 0.005), whereas strong correlations between Al and SOM were observed in higher saturation frequency soils (rs = 0.88, p < 0.005) using nanoscale secondary ion mass spectrometry (NanoSIMS) imaging. Characterization of bulk soil Fe with X-ray absorption spectroscopy showed 1.2-fold greater Fe(II) and 1-fold lower contribution of Fe-organic bonding in soils with high saturation frequency. Fe(III) interactions with carboxylic and aromatic C were identified with 13C nuclear magnetic resonance (NMR) spectroscopy Fe(III) interference experiments. Additionally, carboxylic acid enrichment in high saturation frequency soils quantified by C K-edge X-ray absorption spectroscopy point towards the role of carboxylic functional groups in Al-organic in addition to Fe-organic interactions. In our incubation experiments, a doubling in short-term CO2 evolution (per unit total soil C) was detected for high relative to low saturation frequency soils. Further, an order of magnitude increase in CO2 evolution (per unit water-extractable OC) following anaerobic incubation was only detected in high saturation frequency soils. The observed shift towards Al-dominated SOC interactions and higher OC mineralizability highlights the need to describe C stabilization in soils with flashy wet-dry cycling separately from soils with low saturation frequency or persistent saturation. | |||||
24205. 题目: Mechanistic study on laccase-mediated formation of Fe-OM associations in peatlands Peatlands represent one of the largest terrestrial carbon pools. Phenol oxidase is widely considered to play a critical role in the decomposition of organic matter in peatlands, which is known as the enzymatic latch. However, our recent studies have indicated that the formation of iron-organic matter (Fe-OM) associations is more likely to occur in the presence of laccase, the largest class of phenol oxidases in soils. As the formation of Fe-OM associations is recognized as an important stabilization mechanism for soil organic matter, further clarification of the potential mechanisms contributes to a better understanding of the role of laccase in peatland carbon sequestration. In this study, a series of experiments using different phenolic compounds and peat-derived dissolved organic matter (DOM) were performed. The results from liquid chromatography–high-resolution mass spectrometry (LC-HRMS) and gel permeation chromatography (GPC) analyses indicated that laccase catalyzed the polymerization of phenolics and peat-derived DOM by coupling of the C-O bond, the C–C bond and the C–C/C-O bonds. The polymerized products can combine more effectively with Fe to form Fe-OM associations. FTIR spectral analysis indicated that organic matter associated with Fe under laccase catalysis contained more oxygen-containing functional groups but fewer aromatic CC bonds. Although laccase catalysis can change the chemical structure of organic matter, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analyses showed minimal influence of laccase on the Fe chemical species in the Fe-OM associations. Thus, we propose that laccase mediated the formation of Fe-OM associations by polymerizing organic matter and by increasing the O/C ratio of organic matter. In addition, laccase can improve the sequestration of organic carbon by increasing the C/Fe molar ratio of the formed Fe-OM associations. This mechanism may provide further insight into the role of laccase in the carbon cycling in peatlands. | |||||
24206. 题目: Direct radiative forcing induced by light‐absorbing aerosols in different climate regions over East Asia Light‐absorbing aerosols (LAAs), mainly composed of black carbon (BC) and dust aerosols, are responsible for significant climate forcing through their strong absorption of solar radiation. A fully coupled meteorology‐chemistry model (WRF‐Chem) associated with satellite retrievals and in situ measurements is used to investigate the direct radiative forcing (DRF) induced by LAAs in different climate regions over East Asia. Results show that the annual all‐sky dust and BC DRF are ‐0.84 and 1.06 W m‐2 at the top of atmosphere (TOA), ‐1.23 and ‐1.55 W m‐2 at the surface (SUR) and 0.39 and 2.61 W m‐2 within the atmosphere (ATM) over East Asia. Large LAAs DRF can be found in hyper‐arid, subhumid and humid regions at the SUR and ATM where dust DRF dominates the surface cooling effect, while BC DRF is predominant the eminent warming effect on ATM in most climate regions. The meteorological conditions in hyper‐arid region are associated with enhanced surface wind and weakened atmospheric wind, which is in favor of the emission and accumulation of dust supporting the positive LAAs DRF anomalies higher than 10 W m−2 in hyper‐arid region. The positive geopotential height anomalies over the Northeast China weakens the westerly winds, which is beneficial to the accumulation of LAAs, and results in the positive LAAs DRF anomalies of 3 W m‐2 in semi‐arid regions. The large LAAs mass loading, strong aerosol absorptive ability and decreased cloudiness caused by northerly anomalies are responsible for the high LAAs DRF in humid region. | |||||
24207. 题目: Synthesis and characterization of magnetic biochar adsorbents for the removal of Cr(VI) and Acid orange 7 dye from aqueous solution | |||||
24208. 题目: A novel porous biochar-supported Fe-Mn composite as a persulfate activator for the removal of acid red 88 In this study, a novel porous biochar-supported Fe-Mn composite () was prepared as an effective persulfate (PS) activator for the removal of acid red 88 (AR88). Bimetallic Fe-Mn oxides was supported by biochar to prevent agglomeration of metal oxides nanoparticles and provide more active sites for PS activation. The results showed that bimetallic Fe-Mn oxides were evenly dispersed on the surface of biochar (BC), due to its high specific surface area (1570 m2/g) and hierarchical porous structure. +PS showed a high removal rate of 98.84% for AR88, compared with that of Fe-Mn+PS (80.4%) and BC+PS (78.6%). The synergistic mechanism in for the enhanced PS activation was studied. Moreover, the reaction rate constant of +PS for the removal of AR88 was 0.03814 min−1, indicating a fast reaction rate for AR88 removal. The optimal dosages of and PS were 1 g/L and 2 g/L, respectively. The possible degradation pathways of AR88 were also proposed under the optimal conditions in the +PS system. The results demonstrate that is a promising catalyst for PS activation to remove AR88 with high stability and reusability. | |||||
24209. 题目: Freezing-accelerated removal of chromate by biochar synthesized from waste rice husk The application of biochar has been considered a promising method for remediating contaminated water, as biochar exhibits a redox activity for environmentally relevant redox reactions. Although the mechanisms of various redox reactions by biochar in water have been widely investigated, investigations of reaction in ice have not been attempted. In this study, the freezing-accelerated removal of chromate (Cr(VI)) by biochar synthesized from waste rice husks (RH-BC) was investigated in water (25 °C) and ice (-20 °C). The reduction of Cr(VI) with RH-BC was insignificant in water, whereas an enhanced reduction efficiency of Cr(VI) was observed in ice due to the freeze concentration phenomenon. The enhanced redox reaction between Cr(VI) and dissolved organic matter (DOM) is primarily responsible for the accelerated Cr(VI) reduction in ice, wherein DOM is a primary component of RH-BC. Experiments on various conditions of pH and RH-BC concentrations reveal that Cr(VI) is heavily reduced at low pH values and an aggregation of RH-BC in ice can inhibit the reduction efficiency of Cr(VI) due to a decrease in active sites. The removal of Cr(VI) by RH-BC was successfully achieved with real Cr(VI)-contaminated wastewater in ice; this elucidated the environmental relevance of freezing-assisted Cr(VI) removal in cold regions. | |||||
24210. 题目: Biochar-fertilizer interaction modifies N-sorption, enzyme activities and microbial functional abundance regulating nitrogen retention in rhizosphere soil The impact of the excessive use of N fertilizer remains an environmental problem of global concern. The effect of biochar on soil N retention is still unclear, and knowledge on how a mixture of biochar and fertilizer (B-F) influence N-sorption, N-cycling enzymes activities, diversity and functional abundance of organisms regulating N-retention in rhizosphere soil is poorly understood. Therefore, biochars derived from bamboo, rice straw, cow and pig manure were characterized, and their interactions with NPK fertilizer were evaluated. Results showed that while the effect of biochar on N retention varied among biochar types, such variations increased after B-F. Unlike NH4+ retention, NO3− retention by biochar in fertilized soil was poor (<8 weeks), but were however enhanced after longer periods (15 weeks) in B-F due to plant uptake, sorption and stimulation of N-cycling enzymes activities. This stimulation proved that N-fertilizer provided substrates for N-cycling organisms which was confirmed by the dominance of Proteobacteria, Chloroflexi, Actinobacteria, and Gemmatimonadetes which are important in soil N-cycling, despite the reductions in total diversity, class, phyla and genera abundance of bacterial 16SrRNA genes by B-F. This suggested that B-F induced specific organisms involved in N-cycling, which out-competed other organisms not involved in N-cycling. The provision of substrates by N-fertilizer in B-F for bacterial groups involved in N-cycling modified the rhizosphere microbial structure. The abundance of N-cycling organisms was regulated by the persistence among dominant groups, soil pH, total N, and microbial colonization induced by different biochars interacting with fertilizer which led to enhanced N-retention. | |||||
24211. 题目: Understanding the role of biochar in mitigating soil water stress in simulated urban roadside soil Biochar has been proposed as a promising amendment that may improve soil structure. However, our understanding how it mitigates extreme soil water stress in roadside soils is limited. In this study, we investigated the effects of biochar on soil properties and plant growth under extreme water stress conditions. A greenhouse experiment was conducted on two-year-old Gingko biloba saplings planted in pots with sandy soil only (CON) and with sandy soil mixed with biochar (BC). To simulate excessive water stress conditions, we increased the soil water-filled pore space up to the saturation level throughout the experimental period. We also simulated the switching water conditions by maintaining the saturation condition for 30 days, followed by no addition of water. The BC treatment significantly influenced the aggregate distribution and enhanced the proportion of macroaggregates (>250 μm). The biochar itself also functioned as a macroaggregate and contributed to increased aeration under the excessive water condition. Under the switching water condition, the micropores within the biochar might have helped maintain the available water for plant roots and soil microbes. Plant growth was significantly higher in the BC than CON soils for both the excessive and switching water sets. In the BC soils, plant growth was higher in the excessive than in the switching water sets, indicating that the soil water status in our BC treatment for the excessive water set was not stressful enough to inhibit plant growth. The % optimal water condition, which is defined as the proportion of days when the soil water status is within the least limiting water range, had a very high explanatory power to explain the plant growth (r = 0.7172, p < 0.0001). Our results indicate that biochar can alleviate water stresses in urban roadside soils by retaining plant available water under the wet and dry conditions. | |||||
24212. 题目: Mechanistic exploration of the catalytic modification by co-dissolved organic molecules for micropollutant degradation during fenton process This study aimed to explore the catalytic effect of co-dissolved organic compounds on the tetracycline degradation by Fenton process both in the acidic and neutral environment. The experiments were carried out at [Fe2+]/[H2O2] of 50 μM/50 μM and 50 μM/100 μM. The humic acid, citrate and α-cyclodextrin were selected as the co-dissolved organic compounds. The best removal efficiency of 71% was observed at [Fe2+]/[H2O2] of 50 μM/100 μM without the presence of co-dissolved organic compounds. In the presence of co-dissolved organic compounds, the competition effect occurred and tetracycline removal efficiency was reduced to different extents depending on the H2O2 concentrations and chemical properties of the co-dissolved organic substances. The mechanistic exploration confirmed that the complex-forming interactions among Fe2+, tetracycline and organic co-dissolved molecules kept the catalytic ferrous/ferric redox cycle operating to generate hydroxyl radicals for tetracycline degradation at neutral condition, and this phenomenon was more obvious when the H2O2 concentration was higher. Complex formation also contributed to the overall tetracycline removal in addition to oxidation reactions. By comparing to the mass spectra of citrate, the α-cyclodextrin having a larger molecular structure might react with hydroxyl radicals at a higher probability, resulting in an apparent difference in degradation efficiency despite of the equality of their existing amount in the beginning of the experiment. | |||||
24213. 题目: Simultaneous production of mesoporous biochar and palmitic acid by pyrolysis of brewing industry wastes Pyrolysis of malt bagasse was carried out to obtain simultaneously a mesoporous biochar and an oil fraction rich in palmitic acid. The best result for biochar production was at 500 °C with holding time of 10 min. The yields of biochar and pyrolytic oil in this condition were, 29.7 and 33.9 wt%, respectively. The pyrolysis temperature and holding time influenced the yields of the products. An increase in pyrolysis temperature (from 500 to 700 °C) and holding time (from 10 to 50 min) caused a decrease in biochar yield, a reduction in the volatile matter content and an increase in the amount of ash. Additionally, in the range studied in this work, the increase of the pyrolysis temperature caused a decrease in the specific surface area and total pore volume of the biochar. Meanwhile, the biochar presented interesting functional groups and a mesoporous character, which can be a precursor to obtain adsorbents, or even, be used as adsorbent. The pyrolytic oil was composed of oxygenated aromatic compounds, the main fraction being palmitic acid (27.3%), which can be used in a number of applications, including biodiesel production. This work demonstrated that an available and problematic waste, malt bagasse, can be converted simultaneously into a mesoporous biochar and, into a pyrolytic oil rich in palmitic acid. Biochar and pyrolytic oil, in turn, are products of great value and can be applied in several fields. | |||||
24214. 题目: Characterization of dissolved organic matter in reclaimed wastewater supplying urban rivers with a special focus on dissolved organic nitrogen: A seasonal study This study investigated the seasonal characterization of dissolved organic matter (DOM) in reclaimed wastewater (RW) with a special focus on dissolved organic nitrogen (DON) from two full-scale municipal wastewater reclamation plants (WRPs) where the produced RW was used to augment urban rivers. Results showed that the concentrations of DON in RW ranged from 0.32 mg/L to 1.21 mg/L. A higher seasonal mean value of DON in RW from both of the WRPs was observed in winter (p < 0.05, ANOVA). DON chemical characteristics analysis, including ultrahigh-resolution mass spectrometry and ultrafiltration fractionation, showed that DON in RW exhibits more lability during winter than during the other three seasons. This finding was also supported by the results of an algal bioassay experiment, in which DON bioavailabilities were 63.7 ± 3.0%, 53.0 ± 5.3%, 49.5 ± 0.5%, and 49.8 ± 0.2% for WRP-A and were 60.8 ± 2.4%, 43.7 ± 2.2%, 41.2 ± 1.7%, and 43.1 ± 1.1% for WRP-B in winter, spring, summer, and autumn, respectively. Accordingly, DON in RW during winter is more prone to stimulate natural algae and microorganisms, which gives rise to eutrophication in urban rivers. At the molecular level, the seasonal changes in DON are not coupled with those of DOC, which highlights the necessity of DON measurement to obtain a comprehensive understanding of the seasonal characteristics of DOM in RW and its effect on wastewater reuse in urban rivers. | |||||
24215. 题目: Intra‐ and inter‐cores fungal diversity suggests interconnection of different habitats in an Antarctic frozen lake (Boulder Clay, Northern Victoria Land) A perennially frozen lake at Boulder Clay site (Victoria Land, Antarctica), characterized by the presence of frost mounds, have been selected as an in‐situ model for ecological studies. Different samples of permafrost, glacier ice and brines have been studied as a unique habitat system. An additional sample of brines (collected in another frozen lake close to the previous one) was also considered. Alpha‐ and beta‐diversity of fungal communities showed both intra‐ and inter‐cores significant (p < 0.05) differences, which suggest the presence of interconnection among the habitats. Therefore, the layers of frost mound and the deep glacier could be interconnected while the brines could probably be considered as an open habitat system not interconnected with each other. Moreover the absence of similarity between the lake ice and the underlying permafrost suggested that the lake is perennially frozen based. The predominance of positive significant (p < 0.05) co‐occurrences among some fungal taxa allowed to postulate the existence of an ecological equilibrium in the habitats systems. The positive significant (p < 0.05) correlation between salt concentration, total organic carbon and pH, and some fungal taxa suggests that a few abiotic parameters could drive fungal diversity inside these ecological niches. | |||||
24216. 题目: Eutrophication as a driver of microbial community structure in lake sediments | |||||
24217. 题目: Experimental metatranscriptomics reveals the costs and benefits of dissolved organic matter photo‐alteration for freshwater microbes | |||||
24218. 题目: Effect of salinity on removal performance in hydrolysis acidification reactors treating textile wastewater Hydrolysis acidification (HA) is a classical method for synthetic textile wastewater treatment. However, the salinity effect on the functional mechanism of the microorganisms carrying out HA has rarely been researched. In the present study, the salinity effect on the dye removal efficiency was investigated, and the soluble microbial products (SMP), extracellular polymeric substances (EPS), and microbial community were analyzed at different salinities. The dye and COD removal rates in the HA reactor decreased with increasing salinity. Volatile fatty acids (VFAs) accumulated. The remarkable increases in SMP and EPS were found at high salinity, mainly because more polysaccharides were synthesized than protein. In addition, sequencing analysis showed that high salinity altered the microbial community structure, and Lactococcus, Raoultella and Enterococcus were the decolorizing bacteria at high salinity. This work will improve the understanding of the influence of salinity on the removal efficiency and microbial community during HA. | |||||
24219. 题目: Lignin lags, leads, or limits the decomposition of litter and soil organic carbon | |||||
24220. 题目: Nitrogen input weakens the control of inundation frequency on soil organic carbon loss in a tidal salt marsh The soil carbon (C) sequestration capacity of salt marshes is of considerable importance with respect to the mitigatiing the potentially detrimental consequences of global climate change. Given that tidal salt marshes are subjected to periodic cycles of inundation, it is assumed that soil C cycle in these marshes is expected to be controlled to varing extent by changes in soil moisture and salinity induced by the alternating patterns of drying and rewetting. In addition, with increases in the extent and severity of nitrogen (N) eutrophication becomes serious, we predicted that soil organic carbon (SOC) loss in tidal salt marshes is likely to be highly responsive to increased N loading. In this study, we conducted a two-factor mesocosm experiment (simulated inundation and N input in a tidal salt marsh) to determine the interactive effects of N eutrophication and inundation frequency on CO2 and CH4 emissions and dissolved organic carbon (DOC) contents. Our results showed that increased inundation frequency led to lower levels of CO2 emission but greater CH4 emission, whereas N input weakened the effects of changes in inundation frequency on CO2 and CH4 emissions. Moreover, N input was found to modify CO2 and CH4 emission in response to variations in soil moisture. We also observed an enhancement of soil DOC loss in response to increasing inundation frequency, and that DOC loss in the surface soil was considerably greater than that in subsurface soil. Further, as inundation frequency increased, we detected changes in the relationship between soil DOC and CO2 and CH4. Our findings highlighted that vertical variation in soil moisture induced by inundation is a key factor controlling SOC loss in tidal salt marshes, although N input can weaken this control. | |||||
