Correlation between plasmid DNA damage induced by PM_(10) and trace metals in inhalable particulate matters in Beijing air     

T. P. Jones  L. Merolla  R. J. Richard 《中国科学D辑(英文版)》2006,49(12)

Based on the study of Beijing PM10 bioreactivity with the newly developed plasmid DNA assay method, and analysis for trace elements of PM10, the cause of plasmid DNA damage by PM10 was investigated. The study showed that plasmid DNA oxidative damages by PM10 are of difference in different seasons at various areas. The concentrations of TM50 of PM10 in whole samples respectively collected at urban and comparison sites during winter were 900 μg mL?1 and 74 μg mL?1, while those in their corresponding soluble fractions were 540 μg mL?1 and 86 μg mL?1. In contrast, TM50 contents of PM10 from summer whole samples at urban areas and comparison sites were 116 μg mL?1 and 210 μg mL?1, whereas those in their soluble fractions were 180 μg mL?1 and 306 μg mL?1. The difference of bioreactivity of Beijing PM10 resulted from the variation of trace elements. The oxidative damage of plasmid DNA caused by Pb, Zn, As in PM10 (whole sample) was relatively strong. TM50 and Mn, V, Zn display stronger correlation in the soluble fraction. It implies that Zn could be the major trace element in Beijing PM10 which contributes to oxidative damage to plasmid DNA.  相似文献   

Co-existing fluid and silicate inclusions in mantle diamond   总被引：1，自引：0，他引：1  

E.L. Tomlinson  A.P. Jones  J.W. Harris 《Earth and Planetary Science Letters》2006,250(3-4):581-595

We document the compositions of co-existing silicate macro-inclusions and fluid micro-inclusions in the fibrous coats of eight coated diamonds from the Panda kimberlite (Canada). The mineral inclusions in the diamond coats come from either the peridotite suite (Cr-pyrope, orthopyroxene, olivine and Cr-diopside) or the eclogite suite (omphacite). Therefore, fibrous diamonds grow in the same paragenetic environments as octahedral diamonds. The inclusions document a more fertile source composition (lower Mg# and higher CaO) than for equivalent phases in octahedral diamonds from Panda and worldwide. However, moderate to high Cr₂O₃ contents in garnet and clinopyroxene inclusions suggest that this apparent fertility is due to a secondary process. Geothermometry of the silicate inclusions yields low equilibration temperatures of 930 to 1010 °C. The co-existing fluid micro-inclusions are dominated by H₂O, carbonate and KCl. Fluid inclusions in both the peridotitic and eclogitic samples fall along linear arrays between Fe–Ca–Mg carbonate and KCl. Inclusions in the one eclogitic sample also contain quartz. We suggest that the diamonds have trapped both metasomatised minerals and the metasomatic fluid, and so provide a snap shot of a metasomatic event in the mantle.  相似文献   

Contrasting response of monazite and zircon to a high-T thermal overprint     

Christopher R.M. McFarlane  James N. Connelly  William D. Carlson 《Lithos》2006,88(1-4):135-149

Contact metamorphism in the aureole of the 1322 Ma Makhavinekh Lake Pluton, northern Labrador, affected monazite and zircon in the adjacent 1850 Ma metapelitic gneisses. Transformation of regional garnet and sillimanite to lower-pressure symplectitic intergrowths of cordierite, orthopyroxene, and spinel was accompanied by resorption of inherited monazite inclusions in garnet coupled with the appearance of coronitic high-Y monazite rims. In situ ion-microprobe dating is used to show that high-Y rims formed during contact metamorphism. Liberation of Y and HREE from garnet also gave rise to new xenotime growth. The coronitic nature of monazite overgrowths reflects the diffusion-controlled nature of net-transfer reactions whereas its higher Y composition reflects equilibration with xenotime at peak T (> 800 °C) conditions in the inner aureole. Very thin overgrowths on inherited zircon were also encountered, but only where zircon is surrounded by the symplectitic assemblage, reflecting liberation of Zr from garnet. Although these overgrowths are too thin to date using conventional ion-microprobe techniques, well-developed triple junctions between zircon and orthopyroxene suggests that they grew in textural equilibrium with the contact metamorphic assemblage.

In contrast to monazite, inherited zircon remained intact during contact metamorphism, exhibiting no change in morphology (other than the growth of thin rims) or internal zoning throughout the aureole. However, inherited sector-zoned zircons of anatectic origin display evidence for intracrystalline Pb redistribution in the inner aureole. In these samples, ion-microprobe analyses encountered heterogeneous Pb signals and a dispersion of ²⁰⁷Pb / ²⁰⁶Pb dates away from the well constrained 1850 Ma age of regional metamorphism. Whereas analyses from the outer aureole faithfully record the age of regional metamorphism, those from the inner aureole are normally and reversely discordant and distributed along a line collinear with a 1850 to 1322 Ma discordia. This disturbance is correlated with proximity to the pluton implying that Pb was mobile in the zircon lattice during contact metamorphism. Most grains are characterized by apparent Pb loss from low-U domains and apparent Pb gain in higher-U domains. These data are interpreted to reflect recovery of strained crystalline domains leading to expulsion of Pb* that was able to efficiently diffuse into higher-U domains that were partly amorphous prior to rapid reheating in the inner aureole.  相似文献   

Simulation of Time Series of Concentration Fluctuations in Atmospheric Dispersion Using a Correlation-distortion Technique     

Andrew R. Jones  David J. Thomson 《Boundary-Layer Meteorology》2006,118(1):25-54

Short-duration fluctuations in the concentration of airborne substances can be important in a variety of atmospheric dispersion problems, especially when assessing the risks posed by harmful materials. This paper discusses a simulation technique for generating individual realisations of fluctuating concentration time series in dispersing plumes based on target probability distributions and spectral functions. The scheme uses a correlation-distortion approach to simulate these time series. Gaussian processes with modified spectral characteristics are generated and then transformed to yield non-Gaussian processes with the desired spectral characteristics. The simulation scheme is initially developed for a single receptor, and is then extended to model pairs of correlated time series at two receptors. In fact, the modelling technique can be generalised to an arbitrary number of receptors and this provides, in principal, an approach that is applicable to a wide class of similar problems (such as the modelling of instantaneous puff releases or the response of line-of-sight detection systems). The simulation technique is illustrated using observations made during recent field experiments, conducted both in the United Kingdom and in the U.S.A., investigating the short-range dispersion of a passive tracer.  相似文献   

Causes and uncertainty of future summer drying over Europe   总被引：1，自引：5，他引：1  

David P. Rowell  Richard G. Jones 《Climate Dynamics》2006,27(2-3):281-299

Previous studies have shown that the continuing rise in anthropogenic emissions is likely to cause continental European summers to become substantially drier over the coming century. Since this predicted decline in rainfall and soil moisture (SM) would bring significant stress to society and ecosystems, it is essential that its reliability or otherwise is properly assessed. One approach is to gain a better understanding of the model’s mechanisms of regional climate change and integrate this with a knowledge of the model’s strengths and weaknesses. Here we propose a methodology that partitions some of the mechanisms of regional climate change, and apply it to the problem of summer drying over continental Europe. Earlier work suggests that a plausible partition of the mechanisms of future mid-latitude continental summer drying might be as follows: (a) an earlier and more rapid decline in SM during spring, leading to lower SM in summer, and hence less convective rainfall (‘Spring SM’); (b) a larger land–sea contrast in lower tropospheric summer warming, leading to reduced relative humidity in air advected onto the continent, and so reduced rainfall (‘Warming’); (c) other large-scale atmospheric changes, including remotely forced circulation changes (‘Large-Scale’); and (d) a positive feedback mechanism in summer, whereby the reduced rainfall dries the soil further, so reducing convective activity further (‘Summer SM Feedback’). We attempt to isolate these mechanisms by integrating a geographic subset of the high resolution global atmospheric model HadAM3P to assess their relative importance in generating the projected European summer drying. Each mechanism is approximately represented (and so isolated) using an appropriate mix of inputs to the model, with some matching a control integration and others matching a future scenario integration. These mixed inputs are: atmospheric composition (CO₂, aerosol and ozone), surface boundary data (SM and SSTs), and lateral boundary data (temperature, moisture, winds, and surface pressure). We describe this methodology and the experimental suite in some detail, as well as the constraints on our ability to fully separate these mechanisms. It is also shown that the separation of mechanisms is not compromised by interactions between them. For continental and southeastern Europe, it is found that both the ‘Warming’ and ‘Spring SM’ mechanisms are the primary drivers of the projected summer drying. ‘Summer SM Feedback’ plays an important secondary role, and ‘Large-Scale’ mechanisms, as represented here, have least influence. Since the two dominant mechanisms depend on processes in which we have reasonable confidence, this gives us high confidence in the sign of the projected summer drying over continental and southeastern Europe. Nevertheless, uncertainties in model formulation and future anthropogenic emissions mean that the magnitude of this future rainfall anomaly remains unclear. Over Great Britain and southern Scandinavia, our experiments show that the rainfall anomaly is dominated by opposing effects from the ‘Warming’ and ‘Large-Scale’ mechanisms, which in this area dictate increased and decreased rainfall respectively. Given this rivalry, and also that we have low confidence in the ‘Large-Scale’ mechanism, this suggests that even the sign of the projected drying here is uncertain.  相似文献   

Generating MODFLOW grids from boundary representation solid models   总被引：3，自引：0，他引：3  

Jones NL  Budge TJ  Lemon AM  Zundel AK 《Ground water》2002,40(2):194-200

Complex stratigraphy can be difficult to simulate in MODFLOW models. MODFLOW uses a structured grid that requires that each grid layer be continuous throughout the model domain. This makes it difficult to explicitly represent common features such as pinchouts and embedded seams in a MODFLOW model. In this paper, we describe a method for automatically generating MODFLOW-compatible grids from boundary-representation solid models. Solid models are data structures developed originally for computer-aided design applications that define the geometry of three-dimensional objects. Solid models can be used to represent arbitrarily complex stratigraphy. The elevations defined by the solids are then extracted from the solids in a manner that preserves the continuous-layer requirement imposed by MODFLOW. Two basic approaches are described: The first method adjusts the MODFLOW grid dimensions (layer elevations) to fit the solid model boundaries, and the second method creates a regular MODFLOW grid and adjusts the material properties to match the changes in stratigraphy. One of the main benefits of using solid models to define stratigraphy for MODFLOW models is that it provides a grid-independent definition of the layer elevations that can be used to immediately re-create the MODFLOW grid geometry after any change to the grid resolution.  相似文献   

Validation of Ground-Based Visible Measurements of Total Ozone by Comparison with Dobson and Brewer Spectrophotometers     

M. Van Roozendael  P. Peeters  H. K. Roscoe  H. De Backer  A. E. Jones  L. Bartlett  G. Vaughan  F. Goutail  J.-P. Pommereau  E. Kyro  C. Wahlstrom  G. Braathen  P. C. Simon 《Journal of Atmospheric Chemistry》1998,29(1):55-83

Comparisons of total column ozone measurements from Dobson, Brewer and SAOZ instruments are presented for the period 1990 to 1995 at seven stations covering the mid- and the high northern latitudes, as well as the Antarctic region. The main purpose of these comparisons is to assess, by reference to the well established Dobson network, the accuracy of the zenith-sky visible spectroscopy for the measurement of total ozone. The strengths and present limitations of this latter technique are investigated. As a general result, the different instruments are found to agree within a few percent at all stations, the best agreement being obtained at mid-latitudes. On average, for the mid-latitudes, SAOZ O₃ measurements are approximately 2% higher than Dobson ones, with a scatter of about 5%. At higher latitudes, both scatter and systematic deviation tend to increase. In all cases, the relative differences between SAOZ and Dobson or Brewer column ozone are characterised by a significant seasonal signal, the amplitude of which increases from about 2.5% at mid-latitude to a maximum of 7.5% at Faraday, Antarctica. Although it introduces a significant contribution to the seasonality at high latitude, the temperature sensitivity of the O₃ absorption coefficients of the Dobson and Brewer instruments is shown to be too small to account for the observed SAOZ/Dobson differences. Except for Faraday, these differences can however be largely reduced if SAOZ AMFs are calculated with realistic climatological profiles of ozone, pressure and temperature. Other sources of uncertainties that might affect the comparison are investigated. Evidence is found that the differences in the air masses sampled by the SAOZ and the other instruments contribute significantly to the scatter, and the impact of the tropospheric clouds on SAOZ measurements is displayed.  相似文献   

Simulation of climate change over Europe using a global variable resolution general circulation model   总被引：2，自引：1，他引：1  

M. Déqué  P. Marquet  R. G. Jones 《Climate Dynamics》1998,14(3):173-189

 This study presents results from a downscaling simulation of the impact of a doubling of CO₂ concentration. A multidecadal coupled simulation of a 1% per year increase of CO₂ concentration with the Hadley Centre ocean-atmosphere model provides its sea-surface temperatures and deep soil climatological temperatures as a boundary condition to two 10-year integrations with a version of the ARPEGE-IFS atmosphere model. This global spectral model has a horizontal resolution varying between 60 km in the Mediterranean Sea and 700 km in the southern Pacific. The global impact as well as the regional impact over Europe in this time slice are examined and compared with results from other studies. Over Europe, our main focus, the model impact consists of a warming of about 2 ^°C, relatively uniform and with little seasonal dependence. There are precipitation increases of about 10% over the northern part in winter and spring, and 30% over the southern part in winter only. Precipitation decreases by 20% in the southern part in autumn. The day-to-day variability of the precipitation increases, except over the southern area in summer. No strong impact is found on the soil moisture. Budgets of physical fluxes are examined at the top of the atmosphere and at the land-atmosphere interface. Received: 26 February 1997/Accepted: 21 October 1997  相似文献   

Biogeochemical processes controlling methane in gassy coastal sediments—Part 2: groundwater flow control of acoustic turbidity in Eckernförde Bay Sediments     

Daniel B. Albert  Christopher S. Martens  Marc J. Alperin 《Continental Shelf Research》1998,18(14-15)

To understand the origin of the methane distributions in sediments of Eckernförde Bay, three sites were sampled in May 1994 for determination of methane, sulfate and chloride concentrations in the sediment porewaters. In much of the Bay, bubbles of biogenic methane gas within the sediments lead to widespread ‘acoustic turbidity’ seen in acoustic surveys, masking the sedimentary structure below the gassy horizon. Acoustic windows, where the gas does not appear to be present, occur in several locations in the Bay, often surrounded by acoustically turbid sediments. Pockmarks, shallow depressions in the sediment, are also found in Bay sediments and may show acoustic turbidity at even shallower depths below the interface than surrounding sediments. One site of each type was sampled in this study. The site probably representative of much of the bay below 20 m water depth, revealed methane saturated conditions by about 75 cm depth below the interface, confirming inferences from acoustic scattering data that free gas was present in the sediment. Above this, the methane concentration profile was concave-upward, indicative of methane oxidation in the overlying, sulfate-reducing sediments. These porewaters showed a slightly decreasing chlorinity with depth. At an acoustic window site, methane concentrations rose to a maximum at about 125 cm depth, but did not reach saturation. Below this depth they decreased in a concave-down pattern. Chloride concentrations decreased markedly with depth, indicative of vertical freshwater flow from below. The third site was a pockmark exhibiting very shallow acoustic turbidity at about 25 cm depth. Here methane concentrations rose to exceed saturation within 25 cm depth below the interface and the porewaters became almost fresh by 1.5 m depth, indicative of a stronger flow of freshwater from below. These groundwater flows have competing effects on the methane inventory. They help exclude sulfate from the sediment, allowing the earlier/shallower onset of methanogenesis, but they also aid loss of methane through advection. A diagenetic model that couples the biogeochemistry of sulfate and methane is used to explain the presence or absence of methane gas in these sediments in relation to the flow rate of fresh groundwater from below. Model results indicate that acoustic windows within otherwise acoustically turbid sediments of the bay are likely due to relatively higher rates of vertical advection of fresh groundwater. The gassy pockmark, however, with an even higher vertical advection rate, seems to require the input of additional reactive organic carbon to explain its vertical methane distribution.  相似文献   

Plasma drift estimates from the Dynasonde: comparison with EISCAT measurements     

K. J. F. Sedgemore  J. W. Wright  P. J. S. Williams  G. O. L. Jones  M. T. Rietveld 《Annales Geophysicae》1998,16(10):1138-1143

Modern ionosondes make almost simultaneous measurements of the time rate of change of phase path in different directions and at different heights. By combining these Doppler measurements and angles of arrival of many such radar echoes it is possible to derive reliable estimates of plasma drift velocity for a defined scattering volume. Results from both multifrequency and kinesonde-mode soundings at 3-min resolution show that the Dynasonde-derived F-region drift velocity is in good agreement with EISCAT, despite data loss during intervals of blanketing by intense E-region ionisation. It is clear that the Tromsø Dynasonde, employing standard operating modes, gives a reliable indication of overall convection patterns during quiet to moderately active conditions.  相似文献