Production of methyl chloride and methyl bromide in laboratory cultures of marine phytoplankton   总被引：1，自引：0，他引：1  

M. G. Scarratt  R. M. Moore 《Marine Chemistry》1996,54(3-4)

Laboratory cultures of three phytoplankton species (Phaeodactylum tricornutum, Phaeocystis sp., Thalassiosira weissflogii) were tested for methyl halide (monohalomethane) production by sparging and cryotrapping coupled with GC-ECD detection. Both axenic and xenic cultures were tested under various nutrient regimens. Production of methyl bromide (CH₃Br) and methyl chloride (CH₃Cl) was observed in all cultures. Methyl iodide (CH₃I) production was also observed but could not be quantified due to Chromatographic interference. No consistent differences in production rates were observed between axenic and xenic cultures or between nutrient regimens. Methyl halide production was not directly dependent on photosynthesis. Within each species, total methyl halide production was most closely correlated with biomass, measured as utilized nitrate (ΔDIN) or Chl a. Among the three species, Phaeocystis sp. had the highest production rates and T. weissflogii the lowest. In all cases, the biomass-normalized production rates were only a fraction of the levels needed for the ocean to constitute a significant global source of either CH₃Cl or CH₃Br. However, it must be noted that these data comprise results from a limited number of species and a limited range of conditions.  相似文献   

A descriptive analysis of temporal and spatial patterns of variability in Puget Sound oceanographic properties     

Stephanie K. Moore  Nathan J. Mantua  Jan A. Newton  Mitsuhiro Kawase  Mark J. Warner  Jonathan P. Kellogg 《Estuarine, Coastal and Shelf Science》2008,80(4):545-554

Temporal and spatial patterns of variability in Puget Sound's oceanographic properties are determined using continuous vertical profile data from two long-term monitoring programs; monthly observations at 16 stations from 1993 to 2002, and biannual observations at 40 stations from 1998 to 2003. Climatological monthly means of temperature, salinity, and density reveal strong seasonal patterns. Water temperatures are generally warmest (coolest) in September (February), with stations in shallow finger inlets away from mixing zones displaying the largest temperature ranges. Salinities and densities are strongly influenced by freshwater inflows from major rivers during winter and spring from precipitation and snowmelt, respectively, and variations are greatest in the surface waters and at stations closest to river mouths. Vertical density gradients are primarily determined by salinity variations in the surface layer, with stations closest to river mouths most frequently displaying the largest buoyancy frequencies at depths of approximately 4–6 m. Strong tidal stirring and reflux over sills at the entrance to Puget Sound generally removes vertical stratification. Mean summer and winter values of oceanographic properties reveal patterns of spatial connectivity in Puget Sound's three main basins; Whidbey Basin, Hood Canal, and Main Basin. Surface waters that are warmed in the summer are vertically mixed over the sill at Admiralty Inlet and advected at depth into Whidbey Basin and Hood Canal. Cooler and fresher surface waters cap these warmer waters during winter, producing temperature inversions.  相似文献   

Evidence for an impact‐induced magnetic fabric in Allende,and exogenous alternatives to the core dynamo theory for Allende magnetization          下载免费PDF全文

Adrian R. Muxworthy  Phillip A. Bland  Thomas M. Davison  James Moore  Gareth S. Collins  Fred J. Ciesla 《Meteoritics & planetary science》2017,52(10):2132-2146

We conducted a paleomagnetic study of the matrix of Allende CV3 chondritic meteorite, isolating the matrix's primary remanent magnetization, measuring its magnetic fabric and estimating the ancient magnetic field intensity. A strong planar magnetic fabric was identified; the remanent magnetization of the matrix was aligned within this plane, suggesting a mechanism relating the magnetic fabric and remanence. The intensity of the matrix's remanent magnetization was found to be consistent and low (~6 μT). The primary magnetic mineral was found to be pyrrhotite. Given the thermal history of Allende, we conclude that the remanent magnetization was formed during or after an impact event. Recent mesoscale impact modeling, where chondrules and matrix are resolved, has shown that low‐velocity collisions can generate significant matrix temperatures, as pore‐space compaction attenuates shock energy and dramatically increases the amount of heating. Nonporous chondrules are unaffected, and act as heat‐sinks, so matrix temperature excursions are brief. We extend this work to model Allende, and show that a 1 km/s planar impact generates bulk porosity, matrix porosity, and fabric in our target that match the observed values. Bimodal mixtures of a highly porous matrix and nominally zero‐porosity chondrules make chondrites uniquely capable of recording transient or unstable fields. Targets that have uniform porosity, e.g., terrestrial impact craters, will not record transient or unstable fields. Rather than a core dynamo, it is therefore possible that the origin of the magnetic field in Allende was the impact itself, or a nebula field recorded during transient impact heating.  相似文献   

Quantifying the role of the snowpack in generating water available for run‐off during rain‐on‐snow events from snow pillow records          下载免费PDF全文

Joel W. Trubilowicz  R. Dan Moore 《水文研究》2017,31(23):4136-4150

Rain‐on‐snow events have generated major floods around the world, particularly in coastal, mountainous regions. Most previous studies focused on a limited number of major rain‐on‐snow events or were based primarily on model results, largely due to a lack of long‐term records from lysimeters or other instrumentation for quantifying event water balances. In this analysis, we used records from five automated snow pillow sites in south coastal British Columbia, Canada, to reconstruct event water balances for 286 rain‐on‐snow events over a 10‐year period. For large rain‐on‐snow events (event rainfall >40 mm), snowmelt enhanced the production of water available for run‐off (WAR) by approximately 25% over rainfall alone. For smaller events, a range of antecedent and meteorological factors influenced WAR generation, particularly the antecedent liquid water content of the snowpack. Most large events were associated with atmospheric rivers. Rainfall dominated WAR generation during autumn and winter events, whereas snowmelt dominated during spring and summer events. In the majority of events, the sensible heat of rain contributed less than 10% of the total energy consumed by snowmelt. This analysis illustrated the importance of understanding the amount of rainfall occurring at high elevations during rain‐on‐snow events in mountainous regions.  相似文献   

Field investigation of the groundwater contribution to baseflow in an urban stream from a Quaternary aquifer with a leaky base     

Trisha L. Moore  John L. Nieber  John S. Gulliver  Joseph A. Magner 《水文研究》2020,34(26):5512-5527

Groundwater contributions to baseflow in Minnehaha Creek, a creek located in a highly developed watershed in the Minneapolis-St. Paul metropolitan area, from the watershed's Quaternary aquifer were quantified as part of an effort to manage low flow conditions in the creek. Considerable uncertainty exists with any single method used to quantify groundwater contributions to baseflow; therefore, a “weight of evidence” approach in which methods spanning multiple spatial scales was utilized. Analyses conducted at the watershed-scale (streamflow separation and stable isotope analyses) were corroborated with site-scale measurements (piezometer, seepage meter, and streambed temperature profiles) over a multi-year period to understand processes and conditions controlling connectivity between the stream, its shallow aquifer system and other flow sources. In the case of Minnehaha Creek, groundwater discharge was found to range from 6.2 to 23 mm year⁻¹, which represented only 5 to 11% of annual streamflow during the study period. From the weight of evidence, it is conjectured that regional-scale hydrogeological conditions control groundwater discharge in Minnehaha Creek. Implications of these results with regard to possible augmentation of baseflow by increasing groundwater recharge with infiltration of stormwater are discussed.  相似文献   

Estimating snow water equivalent using cosmic-ray neutron sensors from the COSMOS-UK network     

John R. Wallbank  Steven J. Cole  Robert J. Moore  Seonaid R. Anderson  Edward J. Mellor 《水文研究》2021,35(5):e14048

The intensity of cosmic ray neutrons is inversely correlated with the amount of water present in the surrounding environment. This effect is already employed by around 50 neutron sensors in the COSMOS-UK network to provide daily estimates of soil moisture across the UK. Here, these same sensors are used to automatically provide estimates of snow water equivalent (SWE). Lying snow is typically ephemeral and of shallow depth for most parts of the UK. Moreover, soil moisture is usually high and variable, which acts to increase uncertainties in the SWE estimate. Nevertheless, even under such challenging conditions, both above ground and buried cosmic ray neutron sensors are still able to produce potentially useful SWE estimates. Triple collocation analysis suggests typical uncertainties of less than around 4 mm under UK snow conditions.  相似文献   

Erratum to: Potential impacts of increased coastal flooding in California due to sea-level rise     

Matthew Heberger  Heather Cooley  Pablo Herrera  Peter H. Gleick  Eli Moore 《Climatic change》2012,112(2):523-523

  相似文献   

The Gauss–Listing geopotential value W 0 and its rate from altimetric mean sea level and GRACE     

N. Dayoub  S. J. Edwards  P. Moore 《Journal of Geodesy》2012,86(9):681-694

In geopotential space, the fundamental geodetic parameter W ₀ defines the Gauss–Listing geoid which can be used to best represent the Earth’s mean sea level (MSL) and hence specifies a conventional zero height level to unify vertical datums employed by mapping agencies throughout the world. Further, W ₀ cannot be considered invariant as the parameter varies temporally as a direct response to sea level change and mass redistributions. This study determines W ₀ and its rate, dW ₀/dt, by utilizing altimetric MSL models and an independent mean dynamic topography (MDT) model to define points on the geoid. W ₀ and dW ₀/dt are estimated by two approaches: (i) by means of a global gravity field model (GGM) and (ii) within normal gravity field space as the geopotential value of the best fitting reference ellipsoid. The study shows that uncertainty in W ₀ is mainly influenced by MDT while the choice of methodology, GGM and MSL data coverage are not significant within reason. Our estimate W ₀ =?62636854.2 ± 0.2 m²?s^?2 at epoch 2005.0 differs by 1.8?m²s^?2 from the International Astronomical Union reference value. This study shows that, at a sub-decadal time scale, the time variation dW ₀/dt stems mainly from sea level change with negligible effect from gravity field variations. dW ₀/dt =?(?2.70 ± 0.03)?×?10^?2?m²?s^?2?year^?1, corresponding to a MSL rise of 2.9?mm?year^?1, is evaluated from sea level change based on 16?years of TOPEX and Jason-1 data.  相似文献   

Blue straggler stars in dwarf spheroidal galaxies – II. Sculptor and Fornax     

M. Mapelli  E. Ripamonti  G. Battaglia  E. Tolstoy  M. J. Irwin  B. Moore  S. Sigurdsson 《Monthly notices of the Royal Astronomical Society》2009,396(3):1771-1782

The existence of blue straggler stars (BSSs) in dwarf spheroidal galaxies (dSphs) is still an open question. In fact, many BSS candidates have been observed in the Local Group dSphs, but it is unclear whether they are real BSSs or young stars. Shedding light on the nature of these BSS candidates is crucial in order to understand the star formation history of dSphs. In this paper, we consider BSS candidates in Sculptor and Fornax. In Fornax, there are strong hints that the BSS population is contaminated by young stars, whereas in Sculptor there is no clear evidence of recent star formation. We derive the radial and luminosity distribution of BSS candidates from wide field imaging data extending beyond the nominal tidal radius of these galaxies. The observations are compared with the radial distribution of BSSs expected from dynamical simulations. In Sculptor, the radial distribution of BSS candidates is consistent with that of red horizontal branch (RHB) stars and is in agreement with theoretical expectations for BSSs generated via mass transfer in binaries. On the contrary, in Fornax, the radial distribution of BSS candidates is more concentrated than that of all the considered stellar populations. This result supports the hypothesis that most of BSS candidates in Fornax are young stars, and this is consistent with previous studies.  相似文献   

The 6dF Galaxy Survey: final redshift release (DR3) and southern large-scale structures     

D. Heath Jones  Mike A. Read  Will Saunders  Matthew Colless  Tom Jarrett  Quentin A. Parker  Anthony P. Fairall †  Thomas Mauch  Elaine M. Sadler  Fred G. Watson  Donna Burton  Lachlan A. Campbell  Paul Cass  Scott M. Croom  John Dawe †  Kristin Fiegert  Leela Frankcombe  Malcolm Hartley  John Huchra  Dionne James  Emma Kirby  Ofer Lahav  John Lucey  Gary A. Mamon  Lesa Moore  Bruce A. Peterson  Sayuri Prior  Dominique Proust  Ken Russell  Vicky Safouris  Ken-ichi Wakamatsu  Eduard Westra  Mary Williams 《Monthly notices of the Royal Astronomical Society》2009,399(2):683-698

We report the final redshift release of the 6dF Galaxy Survey (6dFGS), a combined redshift and peculiar velocity survey over the southern sky  (| b | > 10°)  . Its 136 304 spectra have yielded 110 256 new extragalactic redshifts and a new catalogue of 125 071 galaxies making near-complete samples with  ( K , H , J , r _F, b _J) ≤ (12.65, 12.95, 13.75, 15.60, 16.75)  . The median redshift of the survey is 0.053. Survey data, including images, spectra, photometry and redshifts, are available through an online data base. We describe changes to the information in the data base since earlier interim data releases. Future releases will include velocity dispersions, distances and peculiar velocities for the brightest early-type galaxies, comprising about 10 per cent of the sample. Here we provide redshift maps of the southern local Universe with   z ≤ 0.1  , showing nearby large-scale structures in hitherto unseen detail. A number of regions known previously to have a paucity of galaxies are confirmed as significantly underdense regions. The URL of the 6dFGS data base is http://www-wfau.roe.ac.uk/6dFGS .  相似文献