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1.
Determination of hydrophobicity on bacterial surfaces by nonionic surfactants. 总被引:2,自引:0,他引:2
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The hydrophobicity of the bacterial cell surface was determined by using nonionic surfactants. The method is based on the adsorption of nonionic surfactants at the hydrophobic sites of the cell surface. Among many nonionic surfactants, C18H37O(CH2CH2O)13H was preferred. The surfactant was added in excess to a bacterial suspension, and the suspension was mixed by sonication or mechanical stirring. The amount of surfactant remaining in the supernatant after centrifugation was determined spectrophotometrically by measuring the absorbance of tetrabromophenolphthalein ethylester. Effective dispersion of bacterial cells such as Staphylococcus aureus and Mycobacterium smegmatis was achieved by sonication in the presence of the nonionic surfactant. Adsorption measurements coincided with Langmuir's equation, indicative of monolayer adsorption. The method is useful for the determination of the hydrophobicity of various bacterial cell surfaces. 相似文献
2.
Using atomic force microscopy (AFM) we investigated the interaction of amyloid beta (Aβ) (1–42) peptide with chemically modified surfaces in order to better understand the mechanism of amyloid toxicity, which involves interaction of amyloid with cell membrane surfaces. We compared the structure and density of Aβ fibrils on positively and negatively charged as well as hydrophobic chemically-modified surfaces at physiologically relevant conditions. We report that due to the complex distribution of charge and hydrophobicity amyloid oligomers bind to all types of surfaces investigated (CH3, COOH, and NH2) although the charge and hydrophobicity of surfaces affected the structure and size of amyloid deposits as well as surface coverage. Hydrophobic surfaces promote formation of spherical amorphous clusters, while charged surfaces promote protofibril formation. We used the nonlinear Poisson-Boltzmann equation (PBE) approach to analyze the electrostatic interactions of amyloid monomers and oligomers with modified surfaces to complement our AFM data. 相似文献
3.
Jing Zhang Li Li Yueting Peng Yu Chen Xiaoying Lv Shun Li Xiang Qin Hong Yang Chunhui Wu Yiyao Liu 《Biochimica et Biophysica Acta (BBA)/Molecular Cell Research》2018,1865(1):172-185
Tumor cell can be significantly influenced by various chemical groups of the extracellular matrix proteins. However, the underlying molecular mechanisms involved in the interaction between cancer cells and functional groups in the extracellular matrix remain unknown. Using chemically modified surfaces with biological functional groups (CH3, NH2, OH), it was found that hydrophobic surfaces modified with CH3 and NH2 suppressed cell proliferation and induced the number of apoptotic cells. Mitochondrial dysfunction, cytochrome c release, Bax upregulation, cleaved caspase-3 and PARP, and Bcl-2 downregulation indicated that hydrophobic surfaces with CH3 and NH2 triggered the activation of intrinsic apoptotic signaling pathway. Cells on the CH3- and NH2-modified hydrophobic surfaces showed downregulated expression and activation of integrin β1, with a subsequent decrease of focal adhesion kinase (FAK) activity. The RhoA/ROCK/PTEN signaling was then activated to inhibit the phosphorylation of PI3K and AKT, which are essential for cell proliferation. However, pretreatment of MDA-MB-231 cells with SF1670, a PTEN inhibitor, abolished the hydrophobic surface-induced activation of the intrinsic pathway. Taken together, the present results indicate that CH3- and NH2-modified hydrophobic surfaces induce mitochondria-mediated apoptosis by suppressing the PTEN/PI3K/AKT pathway, but not OH surfaces. These findings are helpful to understand the interaction between extracellular matrix and cancer cells, which might provide new insights into the mechanism potential intervention strategies for tumor prognosis. 相似文献
4.
Escherichia coli O157 are an important group of foodborne pathogens with the ability to attach to materials commonly used in food processing environments such as slightly hydrophilic stainless steel. The aim of this study was to characterise six E. coli isolates, including five E. coli O157, for curli production, autoaggregation, hydrophobicity and attachment to highly hydrophilic glass and hydrophobic Teflon®. Curli production and autoaggregation were determined using absorbance assays; hydrophobicity by bacterial adherence to hydrocarbons, hydrophobic interaction chromatography and contact angle measurements; and attachment using epifluorescence microscopy. Curli production varied between strains and for some strains correlated with autoaggregation. Curli production correlated with decreased hydrophobicity for two strains. Four of the six isolates increased attachment to glass, but decreased attachment to Teflon® with increased curli production. In contrast, one of the six isolates decreased attachment to glass, but increased attachment to Teflon® with increasing curli production. Curli production by the remaining isolate did not correlate with hydrophobicity or attachment. Attachment of some E. coli, including E. coli O157, to abiotic surfaces may be influenced by curli production, autoaggregation and hydrophobicity. However, for other strains, a variety of factors may be of greater influence on these properties and ability to attach to abiotic surfaces. This study highlights the complexity of bacterial surface properties and their relationship with bacterial attachment. 相似文献
5.
Use of Self-Assembled Monolayers of Different Wettabilities To Study Surface Selection and Primary Adhesion Processes of Green Algal (Enteromorpha) Zoospores 总被引:1,自引:0,他引:1
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Maureen E. Callow J. A. Callow Linnea K. Ista Sarah E. Coleman Aleece C. Nolasco Gabriel P. Lpez 《Applied microbiology》2000,66(8):3249-3254
We investigated surface selection and adhesion of motile zoospores of a green, macrofouling alga (Enteromorpha) to self-assembled monolayers (SAMs) having a range of wettabilities. The SAMs were formed from alkyl thiols terminated with methyl (CH3) or hydroxyl (OH) groups or mixtures of CH3- and OH-terminated alkyl thiols and were characterized by measuring the advancing contact angles and by X-ray photoelectron spectroscopy. There was a positive correlation between the number of spores that attached to the SAMs and increasing contact angle (hydrophobicity). Moreover, the sizes of the spore groups (adjacent spores touching) were larger on the hydrophobic SAMs. Video microscopy of a patterned arrangement of SAMs showed that more zoospores were engaged in swimming and “searching” above the hydrophobic sectors than above the hydrophilic sectors, suggesting that the cells were able to “sense” that the hydrophobic surfaces were more favorable for settlement. The results are discussed in relation to the attachment of microorganisms to substrata having different wettabilities. 相似文献
6.
Kuan Chun Chaw 《Biofouling》2013,29(7):611-619
The behavioural response of cypris larvae from A. amphitrite (=Balanus amphitrite) exploring three model glass surfaces is quantified by close-range microscopy. Step length and step duration measurements reveal a response to both surface properties and flow. Without flow, 2-day-old cyprids took larger steps with shorter step duration on hydrophilic glass surfaces (bare and NH2-treated) vs hydrophobic glass (CH3-treated). These parameters suggest a more detailed, local inspection of hydrophobic surfaces and a more extensive exploration for hydrophilic surfaces. Cyprids under flow took longer steps and exhibited shorter probing times on hydrophobic glass. On hydrophilic glass, cyprids increased their step duration under flow. This active response is attributed to drag and lift forces challenging the cyprids' temporary anchoring to the substratum. Seven-day-old cyprids showed almost no discrimination between the model surfaces. Microscopic-scale observation of cyprid exploration is expected to provide new insights into interactions between cyprids and surfaces. 相似文献
7.
Warming of subarctic tundra increases emissions of all three important greenhouse gases – carbon dioxide,methane, and nitrous oxide
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Carolina Voigt Richard E. Lamprecht Maija E. Marushchak Saara E. Lind Alexander Novakovskiy Mika Aurela Pertti J. Martikainen Christina Biasi 《Global Change Biology》2017,23(8):3121-3138
Rapidly rising temperatures in the Arctic might cause a greater release of greenhouse gases (GHGs) to the atmosphere. To study the effect of warming on GHG dynamics, we deployed open‐top chambers in a subarctic tundra site in Northeast European Russia. We determined carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) fluxes as well as the concentration of those gases, inorganic nitrogen (N) and dissolved organic carbon (DOC) along the soil profile. Studied tundra surfaces ranged from mineral to organic soils and from vegetated to unvegetated areas. As a result of air warming, the seasonal GHG budget of the vegetated tundra surfaces shifted from a GHG sink of ?300 to ?198 g CO2–eq m?2 to a source of 105 to 144 g CO2–eq m?2. At bare peat surfaces, we observed increased release of all three GHGs. While the positive warming response was dominated by CO2, we provide here the first in situ evidence of increasing N2O emissions from tundra soils with warming. Warming promoted N2O release not only from bare peat, previously identified as a strong N2O source, but also from the abundant, vegetated peat surfaces that do not emit N2O under present climate. At these surfaces, elevated temperatures had an adverse effect on plant growth, resulting in lower plant N uptake and, consequently, better N availability for soil microbes. Although the warming was limited to the soil surface and did not alter thaw depth, it increased concentrations of DOC, CO2, and CH4 in the soil down to the permafrost table. This can be attributed to downward DOC leaching, fueling microbial activity at depth. Taken together, our results emphasize the tight linkages between plant and soil processes, and different soil layers, which need to be taken into account when predicting the climate change feedback of the Arctic. 相似文献
8.
In the initial stage of the crystallization of egg-white lysozyme, monomeric lysozyme aggregated rapidly to form a nucleus in the presence of high salt concentrations. In the present studies, we examined the initial aggregation process of lysozyme (initial crystallization process of lysozyme) in D2O/H2O with sodium ions or potassium ions, and investigated the relationship between the surface hydrophobicity and the aggregation rate of lysozyme. The effect of sodium ions or potassium ions on the initial aggregation process of lysozyme in D2O was clearly different from H2O. The initial aggregation rate of lysozyme in H2O was slower than in D2O. In the case of H2O, the initial aggregation rate was about the same in both ions. But in the case of D2O, the initial aggregation rate was affected by the ion species and the value was lower in potassium ions than in sodium ions. These results suggest that the interaction between lysozyme molecules is stronger in D2O than in H2O. Furthermore, sodium ions have a stronger effect on the interaction than potassium ions in the case of D2O. There was a good correlation among the initial aggregation rate, surface hydrophobicity, and ζ-potential of lysozyme. The hydrophobic interaction may be an important active force in the initial aggregation process of lysozyme. 相似文献
9.
《Biochimica et Biophysica Acta (BBA) - Gene Structure and Expression》1997,1354(3):252-260
A series of meso-5,10,15-tris(N-methyl-4-pyridiniumyl)-20-(4-alkylamidophenyl) porphyrins were synthesized by derivatizing the amino group on the phenyl ring with the following hydrophobic groups: –C(O)C7F15, –C(O)CHCH2, C(O)CH3, –C(O)C7H15, and –C(O)C15H31. The cationic tris-pyridiumyl porphyrin core serves as a DNA binding motif and a photosensitizer to photomodify DNA molecules. The changes of the UV–Vis absorption spectra during the titration of these porphyrins with calf thymus DNA revealed a large bathochromic shift (up to 14 nm) and a hypochromicity (up to 55%) of the porphyrins Soret bands, usually considered as proof of porphyrin intercalation into DNA. Association constants (K) calculated according to the McGhee and von Hippel model, were in the range of 106–107 M−1. An increase in hydrophobicity of the substituents at the 20−meso-position produced higher binding affinity. These porphyrins caused photomodification of the supercoiled plasmid DNA when a green laser beam at 532 nm was applied. Those with higher surface activity acted more efficiently as DNA photomodifiers. The porphyrin with a perfluorinated alkyl chain (–COC7F15) at the meso-20-position inhibited the growth of gram-positive bacteria (S. aureus, or S. epidermidis). Other porphyrins exhibited moderate activity against both gram-negative and gram-positive organisms. 相似文献
10.
In the initial stage of the crystallization of egg-white lysozyme, monomeric lysozyme aggregated rapidly to form a nucleus in the presence of high salt concentrations. In the present studies, we examined the initial aggregation process of lysozyme (initial crystallization process of lysozyme) in D2O/H2O with sodium ions or potassium ions, and investigated the relationship between the surface hydrophobicity and the aggregation rate of lysozyme. The effect of sodium ions or potassium ions on the initial aggregation process of lysozyme in D2O was clearly different from H2O. The initial aggregation rate of lysozyme in H2O was slower than in D2O. In the case of H2O, the initial aggregation rate was about the same in both ions. But in the case of D2O, the initial aggregation rate was affected by the ion species and the value was lower in potassium ions than in sodium ions. These results suggest that the interaction between lysozyme molecules is stronger in D2O than in H2O. Furthermore, sodium ions have a stronger effect on the interaction than potassium ions in the case of D2O. There was a good correlation among the initial aggregation rate, surface hydrophobicity, and -potential of lysozyme. The hydrophobic interaction may be an important active force in the initial aggregation process of lysozyme. 相似文献
11.
Feike A. Dijkstra Jack A. Morgan Daniel R. LeCain Ronald F. Follett 《Plant and Soil》2010,329(1-2):269-281
Elevated CO2 affects plant productivity, but also water availability and plant species composition in semi-arid grasslands, thereby potentially causing complex effects on CH4 consumption and N2O emission. We studied the effects of atmospheric CO2 concentration (400 vs 780 μL L?1), water content (15 vs 20% gravimetric soil moisture), and composition of semi-arid grassland species (perennial grasses Bouteloua gracilis, Hesperostipa comata, and Pascopyrum smithii; sub-shrub Artemisia frigida; invasive forb Linaria dalmatica grown in monoculture and all five species together) on CH4 consumption and N2O emission in a full factorial greenhouse experiment. We used a unique method where we measured microbial effects on CH4 consumption and N2O emission in isolation from effects of gas diffusivity. Microbially mediated CH4 consumption was significantly higher under elevated CO2 (by 20%), but was not affected by soil water content or plant species composition. Microbially mediated N2O emission was not significantly affected by elevated CO2, but was significantly higher with high water content (by 67%) and differed significantly among species. Treatment effects on CH4 consumption and N2O emission often could not be explained simply by differences in soil moisture, suggesting that treatment-induced changes in other soil and microbial properties played a role in causing these effects. 相似文献
12.
Aim: To determine whether assessing the penetration of solutions with different concentrations of ethanol (alcohol percentage test: APT) on fungal surfaces is effective in characterization of hydrophobicity on fungal surfaces. Methods and Results: APT and contact angle (CA) measurements were conducted on nine hydrophobic and two hydrophilic fungal strains from the phyla of Ascomycota, Basidiomycota and Zygomycota. There was a strong positive correlation (R2 = 0·95) between the APT and CA measurements from eight of the nine hydrophobic stains (four pathogenic and mycotoxigenic Fusarium taxa, one melanosporaceous biotrophic taxon, Alternaria sp, Penicillium aurantiogriseum and Cladosporium cladosporioides). Hydrophilic control strains, Mortierella hyalina and Laccaria laccata, had CAs <90° and no measurable degree of hydrophobicity using the APT method. Conclusions: The APT method was effective in measuring the degree of hydrophobicity and can be conducted on different zones of fungal growth. Significance and Impact of the Study: Characterization of fungal surface hydrophobicity is important for understanding of its particular role and function in fungal morphogenesis and pathogenesis. APT is a simple method that can be utilized for fungal hydrophobicity measurements when CA cannot be measured because of obscured view from aerial mycelia growth. 相似文献
13.
采伐对小兴安岭落叶松-泥炭藓沼泽温室气体排放的影响 总被引:4,自引:0,他引:4
利用静态箱-气相色谱法,研究了择伐和皆伐对小兴安岭落叶松-泥炭藓沼泽CH4、CO2、N2O排放的影响.结果表明:采伐改变了落叶松-泥炭藓沼泽CH4和N2O的季节排放规律,其中对照样地的CH4为夏季吸收、秋季排放,N2O夏秋季吸收;择伐样地的CH4和N2O在夏季集中排放;皆伐样地的CH4在夏秋季排放,N2O则在夏季吸收、秋季排放.但采伐对CO2季节排放规律的影响,均为夏季春季秋季.采伐改变了CH4、CO2和N2O的源汇功能,对照样地为CO2的排放源、CH4和N2O的弱吸收汇;采伐地的CO2排放量下降了1/4,并转化为N2O弱排放源,为CH4的弱排放源或强排放源.择伐样地温室效应贡献潜力较对照样地下降了24.5%,皆伐地则提高了3.2%. 相似文献
14.
温带针阔混交林土壤碳氮气体通量的主控因子与耦合关系 总被引:3,自引:0,他引:3
中高纬度森林地区由于气候条件变化剧烈,土壤温室气体排放量的估算存在很大的不确定性,并且不同碳氮气体通量的主控因子与耦合关系尚不明确。以长白山温带针阔混交林为研究对象,采用静态箱-气相色谱法连续4a(2005—2009年)测定土壤二氧化碳(CO2)、甲烷(CH4)和氧化亚氮(N2O)净交换通量以及温度、水分等相关环境因子。研究结果表明:温带针阔混交林土壤整体上表现为CO2和N2O的排放源和CH4的吸收汇。土壤CH4、CO2和N2O通量的年均值分别为-1.3 kg CH4hm-2a-1、15102.2 kg CO2hm-2a-1和6.13 kg N2O hm-2a-1。土壤CO2通量呈现明显的季节性规律,主要受土壤温度的影响,水分次之;土壤CH4通量的季节变化不明显,与土壤水分显著正相关;土壤N2O通量季节变化与土壤CO2通量相似,与土壤水分、温度显著正相关。土壤CO2通量和CH4通量不存在任何类型的耦合关系,与N2O通量也不存在耦合关系;土壤CH4和N2O通量之间表现为消长型耦合关系。这项研究显示温带针阔混交林土壤碳氮气体通量主要受环境因子驱动,不同气体通量产生与消耗之间存在复杂的耦合关系,下一步研究需要深入探讨环境变化对其耦合关系的影响以及内在的生物驱动机制。 相似文献
15.
XULI TANG † SHUGUANG LIU‡ GUOYI ZHOU DEQIANG ZHANG CUNYU ZHOU 《Global Change Biology》2006,12(3):546-560
The magnitude, temporal, and spatial patterns of soil‐atmospheric greenhouse gas (hereafter referred to as GHG) exchanges in forests near the Tropic of Cancer are still highly uncertain. To contribute towards an improvement of actual estimates, soil‐atmospheric CO2, CH4, and N2O fluxes were measured in three successional subtropical forests at the Dinghushan Nature Reserve (hereafter referred to as DNR) in southern China. Soils in DNR forests behaved as N2O sources and CH4 sinks. Annual mean CO2, N2O, and CH4 fluxes (mean±SD) were 7.7±4.6 Mg CO2‐C ha?1 yr?1, 3.2±1.2 kg N2O‐N ha?1 yr?1, and 3.4±0.9 kg CH4‐C ha?1 yr?1, respectively. The climate was warm and wet from April through September 2003 (the hot‐humid season) and became cool and dry from October 2003 through March 2004 (the cool‐dry season). The seasonality of soil CO2 emission coincided with the seasonal climate pattern, with high CO2 emission rates in the hot‐humid season and low rates in the cool‐dry season. In contrast, seasonal patterns of CH4 and N2O fluxes were not clear, although higher CH4 uptake rates were often observed in the cool‐dry season and higher N2O emission rates were often observed in the hot‐humid season. GHG fluxes measured at these three sites showed a clear increasing trend with the progressive succession. If this trend is representative at the regional scale, CO2 and N2O emissions and CH4 uptake in southern China may increase in the future in light of the projected change in forest age structure. Removal of surface litter reduced soil CO2 effluxes by 17–44% in the three forests but had no significant effect on CH4 absorption and N2O emission rates. This suggests that microbial CH4 uptake and N2O production was mainly related to the mineral soil rather than in the surface litter layer. 相似文献
16.
We investigated soil carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) exchanges in an age‐sequence (4, 17, 32, 67 years old) of eastern white pine (Pinus strobus L.) forests in southern Ontario, Canada, for the period of mid‐April to mid‐December in 2006 and 2007. For both CH4 and N2O, we observed uptake and emission ranging from ?160 to 245 μg CH4 m?2 h?1 and ?52 to 21 μg N2O m?2 h?1, respectively (negative values indicate uptake). Mean fluxes from mid‐April to mid‐December across the 4, 17, 32, 67 years old stands were similar for CO2 fluxes (259, 246, 220, and 250 mg CO2 m?2 h?1, respectively), without pattern for N2O fluxes (?3.7, 1.5, ?2.2, and ?7.6 μg N2O m?2 h?1, respectively), whereas the uptake rates of CH4 increased with stand age (6.4, ?7.9, ?10.8, and ?23.3 μg CH4 m?2 h?1, respectively). For the same period, the combined contribution of CH4 and N2O exchanges to the global warming potential (GWP) calculated from net ecosystem exchange of CO2 and aggregated soil exchanges of CH4 and N2O was on average 4%, <1%, <1%, and 2% for the 4, 17, 32, 67 years old stand, respectively. Soil CO2 fluxes correlated positively with soil temperature but had no relationship with soil moisture. We found no control of soil temperature or soil moisture on CH4 and N2O fluxes, but CH4 emission was observed following summer rainfall events. LFH layer removal reduced CO2 emissions by 43%, increased CH4 uptake during dry and warm soil conditions by more than twofold, but did not affect N2O flux. We suggest that significant alternating sink and source potentials for both CH4 and N2O may occur in N‐ and soil water‐limited forest ecosystems, which constitute a large portion of forest cover in temperate areas. 相似文献
17.
Katerina Machacova Hans Papen Jürgen Kreuzwieser Heinz Rennenberg 《Plant and Soil》2013,364(1-2):287-301
Background and aims
Nitrous oxide (N2O) and methane (CH4) can be emitted from surfaces of riparian plants. Data on the emission of these greenhouse gases by upland trees are scarce. We quantified CH4 and N2O emissions from stems of Fagus sylvatica, an upland tree, and Alnus glutinosa, a riparian tree.Methods
The gas fluxes were investigated in mesocosms under non-flooded control conditions and during a flooding period using static chamber systems and gas chromatographic analyses.Results
Despite differences in the presence of an aerenchyma system, both tree species emitted N2O and CH4 from the stems. Flooding caused a dramatic transient increase of N2O stem emissions by factors of 740 (A. glutinosa) and even 14,230 (F. sylvatica). Stem emissions of CH4 were low and even deposition was determined (F. sylvatica controls). The results suggest that CH4 was transported mainly through the aerenchyma, whereas N2O transport occurred in the xylem sap.Conclusions
For the first time it has been demonstrated that upland trees such as F. sylvatica clearly significantly emit N2O from their stems despite lacking an aerenchyma. If this result is confirmed in adult trees, upland forests may constitute a new and significant source of atmospheric N2O. 相似文献18.
Aim: To investigate the effect of curli expression on cell hydrophobicity, biofilm formation and attachment to cut and intact fresh produce surfaces. Methods and Results: Five Escherichia coli O157:H7 strains were evaluated for curli expression, hydrophobicity, biofilm formation and attachment to intact and cut fresh produce (cabbage, iceberg lettuce and Romaine lettuce) leaves. Biofilm formation was stronger when E. coli O157:H7 were grown in diluted tryptic soy broth (1 : 10). In general, strong curli‐expressing E. coli O157:H7 strains 4406 and 4407 were more hydrophobic and attached to cabbage and iceberg lettuce surfaces at significantly higher numbers than other weak curli‐expressing strains. Overall, E. coli O157:H7 populations attached to cabbage and lettuce (iceberg and Romaine) surfaces were similar (P > 0·05), indicating produce surfaces did not affect (P < 0·05) bacterial attachment. All E. coli O157:H7 strains attached rapidly on intact and cut produce surfaces. Escherichia coli O157:H7 attached preferentially to cut surfaces of all produce types; however, the difference between E. coli O157:H7 populations attached to intact and cut surfaces was not significant (P > 0·05) in most cases. Escherichia coli O157:H7 attachment and attachment strength (SR) to intact and cut produce surfaces increased with time. Conclusions: Curli‐producing E. coli O157:H7 strains attach at higher numbers to produce surfaces. Increased attachment of E. coli O157:H7 on cut surfaces emphasizes the need for an effective produce wash to kill E. coli O157:H7 on produce. Significance and Impact of the Study: Understanding the attachment mechanisms of E. coli O157:H7 to produce surfaces will aid in developing new intervention strategies to prevent produce outbreaks. 相似文献
19.
城镇快速发展对河流温室气体溶存及扩散通量的影响——以重庆市黑水滩河流域场镇为例 总被引:5,自引:0,他引:5
场镇发展是西南山区城镇发展的重要模式,且大部分场镇沿河分布,快速城镇发展给河流水环境及生物地化过程带来了一系列影响,然而其对河流温室气体排放时空格局的影响及机制尚不清楚。选择流域场镇发展特征明显的黑水滩河为研究对象,于2014年9月、12月、2015年3月、6月,对流域内干、支流水体温室气体浓度及扩散通量进行分析,旨在阐明流域场镇式发展下河流温室气体排放时空特征及关键驱动因素。研究结果表明,黑水滩河干、支流水体年均二氧化碳分压(pCO_2)及甲烷(CH_4)、一氧化二氮(N_2O)浓度均处于过饱和状态,是大气温室气体的净排放源;流域内干、支流水体流经不同场镇区前后水体碳、氮、磷及叶绿素a含量均不同程度增加,从上游向下游呈现明显的污染累积;水体溶存pCO_2\\CH_4\\N_2O浓度及扩散通量在不同场镇前后也呈现显著增加的趋势,三种温室气体扩散通量平均增幅分别为25.88%、55.22%、99.64%;河流水体pCO_2与N_2O浓度及通量秋季高于其他季节,CH_4浓度及扩散通量春季最高,秋季次之,夏、冬季最低,温室气体浓度及排放的季节变化主要受温度和降雨格局共同影响。相关分析表明,pCO_2与水温和pH关系密切,而水体CH_4和N_2O浓度与水体碳、氮、磷等生源要素均呈显著的正相关关系,水体CH_4与N_2O浓度对生源要素输入极为敏感,流域场镇发展带来的河流污染负荷的增加可能对水体CH_4与N_2O排放产生明显的激发效应。本研究认为,山区河流流域内沿河串珠状场镇分布对河流水体生源要素及其他理化性质产生累积影响,进而改变了水体温室气体的产生与排放时空格局。 相似文献
20.
Agnes Tirol‐Padre Munmun Rai Mahesh Gathala Sheetal Sharma Virender Kumar Parbodh C. Sharma Dinesh K. Sharma Reiner Wassmann Jagdish Ladha 《Global Change Biology》2014,20(1):287-299
Rapid, precise, and globally comparable methods for monitoring greenhouse gas (GHG) fluxes are required for accurate GHG inventories from different cropping systems and management practices. Manual gas sampling followed by gas chromatography (GC) is widely used for measuring GHG fluxes in agricultural fields, but is laborious and time‐consuming. The photo‐acoustic infrared gas monitoring system (PAS) with on‐line gas sampling is an attractive option, although it has not been evaluated for measuring GHG fluxes in cereals in general and rice in particular. We compared N2O, CO2, and CH4 fluxes measured by GC and PAS from agricultural fields under the rice–wheat and maize–wheat systems during the wheat (winter), and maize/rice (monsoon) seasons in Haryana, India. All the PAS readings were corrected for baseline drifts over time and PAS‐CH4 (PCH4) readings in flooded rice were corrected for water vapor interferences. The PCH4 readings in ambient air increased by 2.3 ppm for every 1000 mg cm?3 increase in water vapor. The daily CO2, N2O, and CH4 fluxes measured by GC and PAS from the same chamber were not different in 93–98% of all the measurements made but the PAS exhibited greater precision for estimates of CO2 and N2O fluxes in wheat and maize, and lower precision for CH4 flux in rice, than GC. The seasonal GC‐ and PAS‐N2O (PN2O) fluxes in wheat and maize were not different but the PAS‐CO2 (PCO2) flux in wheat was 14–39% higher than that of GC. In flooded rice, the seasonal PCH4 and PN2O fluxes across N levels were higher than those of GC‐CH4 and GC‐N2O fluxes by about 2‐ and 4fold, respectively. The PAS (i) proved to be a suitable alternative to GC for N2O and CO2 flux measurements in wheat, and (ii) showed potential for obtaining accurate measurements of CH4 fluxes in flooded rice after making correction for changes in humidity. 相似文献