The effect of pH and ionic strength on proton adsorption by the thermophilic bacterium Anoxybacillus flavithermus     

Peta-Gaye Burnett  Hannah Heinrich  Phil J. Bremer  Christopher J. Daughney 《Geochimica et cosmochimica acta》2006,70(8):1914-1927

Numerous studies have utilized surface complexation theory to model proton adsorption behaviour onto mesophilic bacteria. However, few experiments, to date, have investigated the effects of pH and ionic strength on proton interactions with thermophilic bacteria. In this study, we characterize proton adsorption by the thermophile Anoxybacillus flavithermus by performing acid-base titrations and electrophoretic mobility measurements in NaNO₃ (0.001-0.1 M). Equilibrium thermodynamics (Donnan model) were applied to describe the specific chemical reactions that occur at the water-bacteria interface. Acid-base titrations were used to determine deprotonation constants and site concentrations for the important cell wall functional groups, while electrophoretic mobility data were used to further constrain the model. We observe that with increasing pH and ionic strength, the buffering capacity increases and the electrophoretic mobility decreases. We develop a single surface complexation model to describe proton interactions with the cells, both as a function of pH and ionic strength. Based on the model, the acid-base properties of the cell wall of A. flavithermus can best be characterized by invoking three distinct types of cell wall functional groups, with pK_a values of 4.94, 6.85, and 7.85, and site concentrations of 5.33, 1.79, and 1.42 × 10⁻⁴ moles per gram of dry bacteria, respectively. A. flavithermus imparts less buffering capacity than pure mesophilic bacteria studied to date because the thermophile possesses a lower total site density (8.54 × 10⁻⁴ moles per dry gram bacteria).  相似文献   

Continuous field estimation of dissolved organic carbon concentration and biochemical oxygen demand using dual‐wavelength fluorescence,turbidity and temperature          下载免费PDF全文

Kieran Khamis  Chris Bradley  Rob Stevens  David M. Hannah 《水文研究》2017,31(3):540-555

Dissolved organic matter (DOM) quality and quantity is not measured routinely in‐situ limiting our ability to quantify DOM process dynamics. This is problematic given legislative obligations to determine event based variability; however, recent advances in field deployable optical sensing technology provide the opportunity to address this problem. In this paper, we outline a new approach for in‐situ quantification of DOM quantity (Dissolved Organic Carbon: DOC) and a component of quality (Biochemical Oxygen Demand: BOD) using a multi‐wavelength, through‐flow fluorescence sensor. The sensor measured tryptophan‐like (Peak T) and humic‐like (Peak C) fluorescence, alongside water temperature and turbidity. Laboratory derived coefficients were developed to compensate for thermal quenching and turbidity interference (i.e., light attenuation and scattering). Field tests were undertaken on an urban river with ageing wastewater and stormwater infrastructure (Bourn Brook; Birmingham, UK). Sensor output was validated against laboratory determinations of DOC and BOD collected by discrete grab sampling during baseflow and stormflow conditions. Data driven regression models were then compared to laboratory correction methods. A combination of temperature and turbidity compensated Peak T and Peak C was found to be a good predictor of DOC concentration (R² = 0.92). Conversely, using temperature and turbidity correction coefficients provided low predictive power for BOD (R² = 0.46 and R² = 0.51, for Peak C and T, respectively). For this study system, turbidity appeared to be a reasonable proxy for BOD, R² = 0.86. However, a linear mixed effect model with temperature compensated Peak T and turbidity provided a robust BOD prediction (R² = 0.95). These findings indicate that with careful initial calibration, multi‐wavelength fluorescence, coupled with turbidity, and temperature provides a feasible proxy for continuous, in‐situ measurement of DOC concentration and BOD. This approach represents a cost effective monitoring solution, particularly when compared to UV – absorbance sensors and DOC analysers, and could be readily adopted for research and industrial applications.  相似文献   

New insights into the heterogeneity of the Tagish Lake meteorite: Soluble organic compositions of variously altered specimens     

Danielle N. Simkus  Jos C. Aponte  Jamie E. Elsila  Robert W. Hilts  Hannah L. McLain  Christopher D. K. Herd 《Meteoritics & planetary science》2019,54(6):1283-1302

The Tagish Lake carbonaceous chondrite exhibits a unique compositional heterogeneity that may be attributed to varying degrees of aqueous alteration within the parent body asteroid. Previous analyses of soluble organic compounds from four Tagish Lake meteorite specimens (TL5b, TL11h, TL11i, TL11v) identified distinct distributions and isotopic compositions that appeared to be linked to their degree of parent body processing (Herd et al. 2011; Glavin et al. 2012; Hilts et al. 2014). In the present study, we build upon these initial observations and evaluate the molecular distribution of amino acids, aldehydes and ketones, monocarboxylic acids, and aliphatic and aromatic hydrocarbons, including compound‐specific δ¹³C compositions, for three additional Tagish Lake specimens: TL1, TL4, and TL10a. TL1 contains relatively high abundances of soluble organics and appears to be a moderately altered specimen, similar to the previously analyzed TL5b and TL11h lithologies. In contrast, specimens TL4 and TL10a both contain relatively low abundances of all of the soluble organic compound classes measured, similar to TL11i and TL11v. The organic‐depleted composition of TL4 appears to have resulted from a relatively low degree of parent body aqueous alteration. In the case of TL10a, some unusual properties (e.g., the lack of detection of intrinsic monocarboxylic acids and aliphatic and aromatic hydrocarbons) suggest that it has experienced extensive alteration and/or a distinct organic‐depleted alteration history. Collectively, these varying compositions provide valuable new insights into the relationships between asteroidal aqueous alteration and the synthesis and preservation of soluble organic compounds.  相似文献   

Floods in the Southern Alps of New Zealand: the importance of atmospheric rivers          下载免费PDF全文

Daniel. G. Kingston  David A. Lavers  David M. Hannah 《水文研究》2016,30(26):5063-5070

Extremely high precipitation occurs in the Southern Alps of New Zealand, associated with both orographic enhancement and synoptic‐scale weather processes. In this study, we test the hypothesis that atmospheric rivers (ARs) are a key driver of floods in the Southern Alps of New Zealand. Vertically integrated water vapour and horizontal water vapour transport, and atmospheric circulation, are investigated concurrently with major floods on the Waitaki River (a major South Island river). Analysis of the largest eight winter maximum floods between 1979 and 2012 indicates that all are associated with ARs. Geopotential height fields reveal that these ARs are located in slow eastward moving extratropical cyclones, with high pressure to the northeast of New Zealand. The confirmation of ARs as a contributor to Waitaki flooding indicates the need for their further exploration to better understand South Island hydrometeorological extremes. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

The Alpine nappe stack in western Austria: a crustal-scale cross section     

Hannah Pomella  Hugo Ortner  Michael Zerlauth  Bernhard Fügenschuh 《International Journal of Earth Sciences》2015,104(3):733-745

  相似文献   

Wildfire-Migration Dynamics: Lessons from Colorado's Fourmile Canyon Fire     

Raphael J. Nawrotzki  Hannah Brenkert-Smith  Lori M. Hunter  Patricia A. Champ 《社会与自然资源》2014,27(2):215-225

The number of people living in wildfire-prone wildland–urban interface (WUI) communities is on the rise. However, no prior study has investigated wildfire-induced residential relocation from WUI areas after a major fire event. To provide insight into the association between sociodemographic and sociopsychological characteristics and wildfire-related intention to move, we use data from a survey of WUI residents in Boulder and Larimer counties, Colorado. The data were collected 2 months after the devastating Fourmile Canyon fire destroyed 169 homes and burned more than 6,000 acres of public and private land. Although this study is working with a small migrant sample, logistic regression models demonstrate that survey respondents intending to move in relation to wildfire incidence do not differ sociodemographically from their nonmigrant counterparts. They do, however, show significantly higher levels of risk perception. Investigating destination choices shows a preference for short-distance moves.  相似文献   

Closing the Gap Between Researchers and Policymakers: Lessons from the History of Fisheries Management in the United States     

Hannah L. Owens 《社会与自然资源》2014,27(12):1339-1345

Increases in sea surface temperature have led to distributional changes in many commercially exploited fish species. These changes have already led to conflict over mackerel fisheries, arising from demand for fair resource apportionment and desire to manage the fishery sustainably. In order to develop adaptable management strategies for complex ocean fishery systems, policymakers and researchers must move beyond a reactive producer–consumer relationship to develop proactive, supportive collaborations. The history of U.S. national fisheries management is presented as an example of this transition. Building cooperative capacity over the last two centuries has lead to a more systematic understanding of the oceans, and has led to success in reducing the number of overfished stocks. Similar development of cooperation between policymakers and researchers on an international scale may be the surest way to develop management strategies adaptable enough to withstand challenges posed by future climate change.  相似文献   

Amenity migration: diverse conceptualizations of drivers,socioeconomic dimensions,and emerging challenges   总被引：7，自引：0，他引：7  

Hannah?GosnellEmail author  Jesse?Abrams 《GeoJournal》2011,76(4):303-322

Rural communities throughout the postindustrial world are in the midst of a significant transition, sometimes referred to as rural restructuring, as traditional land uses, economic activities, and social arrangements transition to those associated with “post-productivist” or “multifunctional” landscapes. Amenity migration, the movement of people based on the draw of natural and/or cultural amenities, can be thought of as both driver and implication of this transition, resulting in significant changes in the ownership, use, and governance of rural lands, as well as in the composition and socioeconomic dynamics of rural communities. In concert with other social, economic and political processes, amenity migration is contributing to the fundamental transformation of rural communities throughout the world. This paper presents a review of the social science literature related to the concept of amenity migration, focusing on the ways in which it has been conceptualized, theorized, and documented by different communities of scholars. We then profile and summarize diverse perspectives on drivers and socioeconomic impacts, highlighting emerging challenges and opportunities related to this type of migration occurring at multiple scales and in multiple sites. The paper also identifies and discusses particular areas where further research is needed.  相似文献   

The Northern Giudicarie and the Meran-Mauls fault (Alps,Northern Italy) in the light of new paleomagnetic and geochronological data from boudinaged Eo-/Oligocene tonalites     

Hannah Pomella  Urs Klötzli  Robert Scholger  Michael Stipp  Bernhard Fügenschuh 《International Journal of Earth Sciences》2011,100(8):1827-1850

This study concentrates on small intrusions along two important faults of the Giudicarie fault system, the Northern Giudicarie and the Meran-Mauls fault, summarised under the term tonalitic lamellae. Magnetic fabric analyses in combination with structural field data indicate dextral strike slip deformation along the NE–SW striking northern part of the Giudicarie fault system, the Meran-Mauls fault, overprinted by younger thrusting. The regional stressfield was oriented approximately NNW–SSE during Tertiary times. The distinctive change in deformation along the Meran-Mauls fault from dextral strike slip to top-SE thrusting may be caused by a rotation or bending of the fault after the intrusion of the tonalites and the formation of their horizontal magnetic foliation. Based on the assumption of a preliminary straight Periadriatic lineament bent by the NNW-wards advancement of the Southalpine indenter, the tonalitic lamellae may be interpreted as lenses sheared off from the Adamello batholith during indentation. New U/Pb data on zircon show that some of the lamellae are of Oligocene (Rupelian), others of Late Eocene (Priabonian) age. An amphibole-gabbro lens occurring on the Meran-Mauls fault provides a Middle Eocene (Bartonian) age. Among the major Periadriatic plutons, only the southern units of the Adamello batholith also intruded in the Eocene that suggests a strong correlation between the tonalitic lamellae and the Adamello batholith. The analyses of the remanent magnetisation and the Curie point determinations argue for magnetite as the main carrier of a viscous magnetisation blocked at relatively low temperatures. This indicates slow cooling of the investigated intrusions along the Giudicarie fault system down to approximately 300°C, which is in contrast to the fast cooling determined for the Adamello intrusion units currently at the surface. The new zircon fission track data also show later cooling of the tonalites along the Giudicarie fault system when compared with the Adamello batholith in the south and the Mauls lamellae in the north, indicating that this area contains magmatic bodies exhumed from a deeper structural level than in the Adamello and the Mauls region. This may be due to important top-SE thrusting and transpressive faulting in the footwall of the Northern Giudicarie fault and the Meran-Mauls fault.  相似文献   

Hydrological influences on hyporheic water quality: implications for salmon egg survival     

I. A. Malcolm  C. Soulsby  A. F. Youngson  D. M. Hannah  I. S. McLaren  A. Thorne 《水文研究》2004,18(9):1543-1560

The spatial and temporal variability of groundwater–surface‐water (GW–SW) interactions was investigated in an intensively utilized salmon spawning riffle. Hydrochemical tracers, were used along with high‐resolution hydraulic head and temperature data to assess hyporheic dynamics. Surface and subsurface hydrochemistry were monitored at three locations where salmon spawning had been observed in previous years. Temperature and hydraulic head were monitored in three nests of three piezometers located to characterize the head, the run and the tail‐out of the riffle feature. Hydrochemical gradients between surface and subsurface water indicated increasing GW influence with depth into the hyporheic zone. Surface water was characterized by high dissolved oxygen (DO) concentrations, low alkalinity and conductivity. Hyporheic water was generally characterized by high levels of alkalinity and conductivity indicative of longer residence times, and low DO, indicative of reducing conditions. Hydrochemical and temperature gradients varied spatially over the riffle in response to changes in local GW–SW interactions at the depths investigated. Groundwater inputs dominated the head and tail of the riffle. The influence of SW increased in the area of accelerating flow and decreasing water depth through the run of the riffle. Temporal GW–SW interactions also varied in response to changing hydrological conditions. Gross changes in hyporheic hydrochemistry were observed at the weekly scale in response to changing flow conditions and surface water inputs to the hyporheic zone. During low flows, caused by freezing or dry weather, hyporheic hydrochemistry was dominated by GW inputs. During higher flows hyporheic hydrochemistry indicated that SW contributions increased. In addition, high‐resolution hydraulic head data indicated that rapid changes in GW–SW interactions occurred during hydrological events. The spatial, and possibly the temporal, variability of GW–SW interactions had a marked effect on the survival of salmon ova. It is concluded that hyporheic dynamics and their effect on stream ecology should be given increased consideration by fisheries and water resource managers. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献