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1.
All-sky camera (ASC), Global Positioning System (GPS), and ionosonde measurements were used to investigate the upper atmospheric variations at mid-latitude during the strong geomagnetic storm on October 29–31, 2003. An arc-shaped 630.0 nm emission was observed in the northern sky on all-sky images taken at Mt. Bohyun (36.2°N, 128.9°E, GMLAT=29°N) in Korea during 17:48–8:58 UT in the main phase of the geomagnetic storm on October 29. The NmF2 and hmF2 from the ionosonde show strong disturbances at that time. The vertical profiles of electron densities, calculated by the ionospheric tomographic method using ground-based GPS slant total electron contents measurements, show the largest value at ∼440 km height at 18:30 UT on October 29 when the enhancements of OI 630.0 nm emission were observed. The arc-shaped red emission observed during the main phase of the magnetic storm is likely a low-latitude red aurora due to its short duration of ∼1 h. The result implies that the plasmapause was at L=1.4–1.6 during the geomagnetic storm. The fact that the arc did not follow a constant L-value appears to suggest that neutral precipitation and a traveling ionospheric disturbance could also be the cause of the arc.  相似文献   

2.
Erythemal ultraviolet (UVER; 280–400 nm) and total shortwave (SW; 305–2800 nm) solar irradiances were recorded from 2000 to 2009 in Valladolid, Spain. UVER and SW values under cloudless conditions are simulated by radiative transfer (TUV 4.6) and empirical models. These model estimations are tested with experimental measurements showing a great agreement (root mean square error around 7%). The aerosol effect on UVER irradiance is determined through a model study. UVER radiation and total ozone column (TOC) temporal evolutions show a negative relationship. TOC accounts for 80% of UVER variance and its radiation amplification factor is 1.1 at zenith of 65°. Cloud effects on solar radiation are shown and quantified by the cloud modification factor. Moreover the enhancement effect cases are analysed. SW radiation proves more sensitive to clouds than UVER. Clouds are seen to attenuate and enhance solar radiation by up to 93% and 22% in the UVER range, respectively.  相似文献   

3.
In this paper, we investigate the solar flare effects of the ionosphere at middle latitude with a one-dimensional ionosphere theoretical model. The measurements of solar irradiance from the SOHO/Solar EUV Monitor (SEM) and GOES satellites have been used to construct a simple time-dependent solar flare spectrum model, which serves as the irradiance spectrum during solar flares. The model calculations show that the ionospheric responses to solar flares are largely related to the solar zenith angle. During the daytime most of the relative increases in electron density occur at an altitude lower than 300 km, with a peak at about 115 km, whereas around sunrise and sunset the strongest ionospheric responses occur at much higher altitudes (e.g. 210 km for a summer flare). The ionospheric responses to flares in equinox and winter show an obvious asymmetry to local midday with a relative increase in total electron content (TEC) in the morning larger than that in the afternoon. The flare-induced TEC enhancement increases slowly around sunrise and reaches a peak at about 60 min after the flare onset.  相似文献   

4.
A database of the electron temperature (Te) comprising of most of the available LEO satellite measurements is used for studying the solar activity variations of Te. The Te data are grouped for two levels of solar activity (low LSA and high HSA), five altitude ranges between 350 and 2000 km, and day and night. By fitting a theoretical expression to the Te values we obtain variation of Te along magnetic field lines and heat flux for LSA and HSA. We have found that Te increases with increase in solar activity at low and mid-latitudes during nighttime at all altitudes studied. During daytime the Te response to solar activity depends on latitude, altitude, and season. This analysis shows existence of anti-correlation between Te and solar activity at mid-latitudes below 700 km during the equinox and winter day hours. Heat fluxes show small latitudinal dependence for daytime but substantial for nighttime.  相似文献   

5.
The total solar eclipse of 29 March, 2006 which was visible at Ibadan (7.55°N, 4.56°E), south-western Nigeria was utilized to document atmospheric surface-layer effects of the eclipse for the first time in Nigeria. The meteorological parameters measured are global radiation, net radiation, wind speed (at different heights), atmospheric pressure and soil temperature (5, 10 and 30 cm), moisture and heat flux and rainfall. The results revealed remarkable dynamic atmospheric effects. The observations showed that the incoming solar radiation, net radiation and air temperature were significantly affected.There was an upsurge of wind speed just before the first contact of the eclipse followed by a very sharp decrease in wind speed due to the cooling and stabilization of the atmospheric boundary layer. The atmospheric pressure lags the eclipse maximum by 1 h 30 min, while the soil temperature at 5 and 10 cm remain constant during the maximum phase of the eclipse.  相似文献   

6.
Parallel factor analysis of fluorescence excitation emission matrices of surface water samples of a globally large river (Yangtze River, China) watershed identified three classes of fluorescent dissolved organic matter (FDOM) that had ex/em = 280/330 nm, 305/385 nm and 350/450 nm respectively, resembling “peak T”, “peak M” and “peak C” commonly identified in natural water, respectively. Peak T (a tyrosine/tryptophan-like FDOM) did not show correlations to peak M or C which were humic-like substances, while a positive correlation (r = 0.935, p < 0.001) was present between the natural log-transformed maximum fluorescence intensity (Fmax) of peaks T and M indicating a tight link during their production and processing. Fmax values (in Raman unit nm?1) normalized to dissolved organic carbon (DOC) concentration were low, varying in ranges 15.93–85.95, 29.83–83.54 and 19.73–51.05 × 10?5 nm?1 (μmol/L)?1 for peaks T, M and C, respectively, in line with the history of strong photobleaching of the water samples as indicated by fairly high absorption spectral slope ratios (0.75–1.53 with a mean 1.03). Intermediate fluorescence index (FI) (1.46–1.83 with a mean 1.61) and small specific absorption at 254 nm (0.64–1.93 with a mean 1.15 m?1 mg?1 L) of the water samples, indicated the presence of both aquatic microbial DOM (e.g. peak T) and soil DOM (e.g. peak C). Peak C could be substantially removed by UV-A (320–400 nm) irradiation, while peak M was slightly increased when a microbe-containing water was exposed to the same UV-A irradiation. Taken together, peak C was attributed to diffuse soil source while peak M was likely attributed to joint effects of microbial activities and solar irradiation on the chromophores in the sample.  相似文献   

7.
The isotopic compositions of terrestrial hydrogen and nitrogen are clearly different from those of the nebular gas from which the solar system formed, and also differ from most of cometary values. Terrestrial N and H isotopic compositions are in the range of values characterizing primitive meteorites, which suggests that water, nitrogen, and other volatile elements on Earth originated from a cosmochemical reservoir that also sourced the parent bodies of primitive meteorites. Remnants of the proto-solar nebula (PSN) are still present in the mantle, presumably signing the sequestration of PSN gas at an early stage of planetary growth. The contribution of cometary volatiles appears limited to a few percents at most of the total volatile inventory of the Earth. The isotope signatures of H, N, Ne and Ar can be explained by mixing between two end-members of solar and chondritic compositions, respectively, and do not require isotopic fractionation during hydrodynamic escape of an early atmosphere.The terrestrial inventory of 40Ar (produced by the decay of 40K throughout the Earth's history) suggests that a significant fraction of radiogenic argon may be still trapped in the silicate Earth. By normalizing other volatile element abundances to this isotope, it is proposed that the Earth is not as volatile-poor as previously thought. Our planet may indeed contain up to ~ 3000 ppm water (preferred range: 1000–3000 ppm), and up to ~ 500 ppm C, both largely sequestrated in the solid Earth. This volatile content is equivalent to an ~ 2 (± 1) % contribution of carbonaceous chondrite (CI-CM) material to a dry proto-Earth, which is higher than the contribution of chondritic material advocated to account for the platinum group element budget of the mantle. Such a (relatively) high contribution of volatile-rich matter is consistent with the accretion of a few wet planetesimals during Earth accretion, as proposed by recent dynamical models.The abundance pattern of major volatile elements and of noble gases is also chondritic, with two notable exceptions. Nitrogen is depleted by one order of magnitude relative to water, carbon and most noble gases, which is consistent with either N retention in a mantle phase during magma generation, or trapping of N in the core. Xenon is also depleted by one order of magnitude, and enriched in heavy isotopes relative to chondritic or solar Xe (the so-called “xenon paradox”). This depletion and isotope fractionation might have taken place due to preferential ionization of xenon by UV light from the early Sun, either before Earth's formation on parent material, or during irradiation of the ancient atmosphere. The second possibility is consistent with a recent report of chondritic-like Xe in Archean sedimentary rocks that suggests that this process was still ongoing during the Archean eon (Pujol et al., 2011). If the depletion of Xe in the atmosphere was a long-term process that took place after the Earth-building events, then the amounts of atmospheric 129Xe and 131–136Xe, produced by the short-lived radioactivities of 129I (T1/2 = 16 Ma) and 244Pu (T1/2 = 82 Ma), respectively, need to be corrected for subsequent loss. Doing so, the I–Pu–Xe age of the Earth becomes ≤ 50 Ma after start of solar system formation, instead of ~ 120 Ma as computed with the present-day atmospheric Xe inventory.  相似文献   

8.
This paper describes the operational principles, design and field testing of a new, compact, Faraday filter-based spectrometer to measure the D2 (589.158 nm) to D1 (589.756 nm) intensity ratio of the sodium nightglow. This work was motivated by the observations of Slanger et al. (2005) who reported an annual variation in D2/D1 with values ranging from 1.2 to 1.8. Their proposed explanation, a modified Chapman mechanism, requires that the intensity ratio is related to the concentration ratio of atomic oxygen [O] to molecular oxygen [O2]. Our method of measuring D2/D1 utilizes narrowband Na vapor Faraday filters, which can yield observations on the fractional contributions of the two chemical pathways of the modified Chapman mechanism. Since delineation of the two chemical pathways requires a spectral resolution of 0.0002 nm, this is not possible with any other existing instrument.  相似文献   

9.
Using over 20 years of ground-based magnetometer data from the CANOPUS/CARISMA magnetometer array, we present a statistical characterisation of Pc5 ultra-low frequency (ULF) power in the 2–10 mHz band as a function of magnetic local time (MLT), L-shell, and solar wind speed. We examine the power across L-shells between 4.2 and 7.9, using data from the PINA, ISLL, GILL and FCHU stations, and demonstrate that there is a significant MLT dependence in both the H- and D-component median 2–10 mHz power during both fast (>500 km/s) and slow (<500 km/s) solar wind speeds. The H-component power consistently dominates over D-component power at all MLTs and during both fast and slow solar wind. At the higher-L stations (L>5.4), there are strong MLT power peaks in the morning and midnight local time sectors; the morning sector dominating midnight during fast solar wind events. At lower L-shells, there is no evidence of the midnight peak and the 2–10 mHz power is more symmetric with respect to MLT except during the fastest solar wind speeds. There is little evidence in the ground-based power of a localised MLT peak in ULF power at dusk, except at the lowest L-shell station, predominantly in the H-component. The median 2–10 mHz power increases with an approximate power law dependence on solar wind speed, at all local times across the L-shell domain studied in both components. The H-component power peaks at the latitude of the GILL station, with significantly lower power at both higher and lower L-shells. Conversely, the D-component power increases monotonically. We believe that this is evidence for 2–10 mHz power accumulating at auroral latitudes in field line resonances. Finally, we discuss how such ULF wave power characterisation might be used to derive empirical radiation belt radial diffusion coefficients based on, and driven by, the solar wind speed dependence of ULF wave power.  相似文献   

10.
The UV camera is becoming an important new tool in the armory of volcano geochemists to derive high time resolution SO2 flux measurements. Furthermore, the high camera spatial resolution is particularly useful for exploring multiple-source SO2 gas emissions, for instance the composite fumarolic systems topping most quiescent volcanoes. Here, we report on the first SO2 flux measurements from individual fumaroles of the fumarolic field of La Fossa crater (Vulcano Island, Aeolian Island), which we performed using a UV camera in two field campaigns: in November 12, 2009 and February 4, 2010. We derived ~ 0.5 Hz SO2 flux time-series finding fluxes from individual fumaroles, ranging from 2 to 8.7 t d?1, with a total emission from the entire system of ~ 20 t d?1 and ~ 13 t d?1, in November 2009 and February 2010 respectively. These data were augmented with molar H2S/SO2, CO2/SO2 and H2O/SO2 ratios, measured using a portable MultiGAS analyzer, for the individual fumaroles. Using the SO2 flux data in tandem with the molar ratios, we calculated the flux of volcanic species from individual fumaroles, and the crater as a whole: CO2 (684 t d?1 and 293 t d?1), H2S (8 t d?1 and 7.5 t d?1) and H2O (580 t d?1 and 225 t d?1).  相似文献   

11.
The ultraviolet spectrometers (UVS) on the solar mesosphere explorer (SME) and student nitric oxide explorer (SNOE) measured scattered limb radiance at small and large scattering angles from polar mesospheric clouds (PMCs). The SME data are for the northern summer hemisphere (NH) in 1983 and 1984. The SNOE measurements are for the NH in 2000 and for the southern hemisphere (SH) in the 2000/2001 season. From this database, we deduce the modal particle size from the measured scattering angle asymmetry in radiance. This quantity is determined as a function of time within the PMC season, and latitude, assuming several scattering models depending on the adopted size distribution and particle shape. For assumed spherical particles with a Gaussian distribution of width of 14 nm, the results for SME show mode particle sizes that vary from about 35 to 60 nm throughout the season. The results for SNOE under the same assumption show that for high latitudes in the NH the particle size grows systematically from the seasonal onset, from about 25 nm to a maximum of about 45 nm at 30 days after solstice. Lower latitudes show a similar time dependence, but with smaller particle sizes. SH PMC particle sizes display a more complicated seasonal variability. Generally, variability in measured cloud height is anti-correlated with particle size for the seasons analyzed here. Particle sizes in the SH are generally smaller than those in the NH, consistent with the northern bias in PMC brightness, and with previous satellite studies. These results are interpreted in terms of our understanding of PMC microphysics and inter-hemispheric differences in temperature and dynamics. Our quantitative results for mode radius depend on the assumption of a constant distribution width. If the width varies with latitude or time, our calculated gradients of mode radius would be different.  相似文献   

12.
The spectral attenuation of solar irradiation was measured during summer in two types of coastal waters in southern Chile, a north Patagonian fjord (Seno Reloncaví) and open coast (Valdivia). In order to relate the light availability with the light requirements of upper subtidal seaweeds, the saturating irradiance for photosynthesis (Ek) from P–I curves was measured. In addition the UV risk was assessed. Based on the z1% of PAR, the lower limit of the euphotic zone in the studied systems averaged 21 m (Kd 0.24 m?1) in Seno Reloncaví and 18 m (Kd 0.27 m?1) in the coast of Valdivia. Photosynthesis of the studied seaweeds was saturated at markedly lower irradiances than found in their natural depths at the time of the study. Solar radiation penetrating into these depths at both locations largely supports the light requirements for the photosynthesis of subtidal species: 50–160 μmol m?2 s?1 for seaweeds from Seno Reloncaví (7 m tidal range) and 20–115 μmol m?2 s?1 for Valdivia assemblages (2 m tidal range). Optimal light conditions to saturate photosynthesis (Ek) were present at 10–16 m water depth. The attenuation of solar irradiation did not vary significantly between the fjord and coastal sites of this study. However, the underwater light climates to which seaweeds are exposed in these sites vary significantly because of the stronger influence of tidal range affecting the fjord system as compared with the open coastal site. The patterns of UV-B penetration in these water bodies suggest that seaweeds living in upper littoral zones such as the intertidal and shallow subtidal (<3 m) may be at risk.  相似文献   

13.
Mid-latitude Digisonde Doppler velocities, auroral electrojet (AE) indices and cloud-to-ground (CG) lightning strokes during August 2003–2004 were used to study the perturbations in the F-region vertical drift associated with terrestrial thunderstorms. A superposed epoch analysis (SEA) showed that the F-region vertical drifts Vz had a net descent of ～0.6 m s?1 peaking ～3 h after lightning. Stronger downward perturbations of up to ～0.9 m s?1 were observed in the afternoon on the day prior to lightning days. The perturbations were less significant on the day after and insignificant during the remaining intervals up to 144 h on either side of the lightning. The stronger responses on the day before are consistent with causality because the lightning times were merely proxies for the physical mechanisms involved. The actual causes are unclear, but we discuss the possible roles of lightning-induced ionisation enhancements, intense electric fields penetrating upward from electrified clouds, and atmospheric gravity waves (AGWs) radiated from thunderstorms or from the accompanying tropospheric fronts. There is no doubt that the behaviour of the mid-latitude F-region is controlled by the thermospheric winds and the solar wind-magnetosphere electrical generators, but our results suggest that electrified clouds also account for a significant, albeit relatively small component of the ionospheric variability.  相似文献   

14.
The single backscattering model was used to estimate total attenuation of coda waves (Qc) of local earthquakes recorded on eight seismological stations in the complex area of the western continental Croatia. We estimated Q0 and n, parameters of the frequency dependent coda-Q using the relation Qc = Q0fn. Lapse time dependence of these parameters was studied using a constant 30 s long time window that was slid along the coda of seismograms. Obtained Qc were distributed into classes according to their lapse time, tL. For tL = 20–50 s we estimated Q0 = 45–184 and n = 0.49–0.94, and for tL = 60–100 s we obtained Q0 = 119–316 and n = 0.37–0.82. There is a tendency of decrease of parameter n with increasing Q0, and vice versa. The rates of change of both Q0 and n seem to decrease for lapse times larger than 50–80 s, indicating an alteration in rock properties controlling coda attenuation at depths of about 100–160 km. A very good correlation was found between the frequency dependence parameter n and the Moho depths for lapse times of 50, 60 and 70 s.  相似文献   

15.
Data on the distribution of fCO2 were obtained during a cruise in the Aegean Sea during February 2006. The fCO2 of surface water (fCO2sw) was lower than the atmospheric fCO2 (fCO2atm) throughout the area surveyed and ΔfCO2 values varied from ?34 to ?61 μatm. The observed under-saturation suggests that surface waters in the Aegean represent a sink for atmospheric CO2 during the winter of 2006. Higher fCO2sw values were recorded in the ‘less warm’ and ‘less saline’ shallow northernmost part of the Aegean Sea implying that the lower seawater temperature and salinity in this area play a crucial role in the spatial distribution of fCO2sw.A first estimate of the magnitude of the air–sea CO2 exchange and the potential role of the Aegean Sea in the transfer of atmospheric CO2 was also obtained. The air–sea CO2 fluxes calculated using different gas transfer formulations showed that during February 2006, the Aegean Sea absorbs atmospheric CO2 at a rate ranging from ?6.2 to ?11.8 mmol m?2 d?1 with the shipboard recorded wind speeds and at almost half rate (?3.5 to ?5.5 mmol m?2 d?1) with the monthly mean model-derived wind speed. Compared to recent observations from other temperate continental shelves during winter period, the Aegean Sea acts as a moderate to rather strong sink for atmospheric CO2.Further investigations, including intensive spatial and temporal high-resolution observations, are necessary to elucidate the role of the Aegean Sea in the process of transfer of atmospheric CO2 into the deep horizons of the Eastern Mediterranean.  相似文献   

16.
We have measured magnetic hysteresis loops, zero-field-cooled (ZFC) and field-cooled (FC) remanence, and low-field AC susceptibility as a function of temperature between 2 and 40 K for a single crystal several mm in size and for two powders of manganese carbonate (mineral rhodochrosite, MnCO3), one ground from a natural precipitate (grainsize ∼100 μm) and another synthesized in the laboratory (grainsize ∼10 μm). For the single crystal, measurements carried out both in the basal (easy magnetization) plane and along the trigonal (hard magnetization) axis yielded, expectedly, grossly different magnetic properties. In the basal plane, hysteresis appears to be mostly controlled by domain wall movement at the two lowest temperatures studied, 5 and 15 K, as indicated by a fairly broad switching field distribution. At 25 K and above, however, magnetization reversal occurs at a single, well defined magnetic field, which we interpret as a characteristic field of the in-plane magnetic anisotropy. Hysteresis in the basal plane is observed up to 36 K which is above the nominal Néel temperature of rhodochrosite (34.3 K). In addition, a sharp coercivity peak occurs at 34.5 K. Rather unexpectedly, hysteresis is also observed for the magnetic field applied along the trigonal axis. It is very small at 5 K but develops gradually with increasing temperature, coercivity reaching maximum of 100 mT at 28 K and remanence peaking at slightly higher temperature (30–31 K). Hysteresis along the trigonal axis is observed up to 37 K. Hysteresis temperature dependence conforms with the AC susceptibility versus temperature curve which shows a maximum at 36.5 K. ZFC/FC remanence curves also closely match the temperature dependence of remanence extracted from hysteresis loops. We suggest that this behavior could be due to the presence of a minor, about 1 at.% amount of Fe2+ substituting for Mn in the crystalline lattice of rhodochrosite. Hysteresis measurements on powders have revealed a significant enhance in coercivity, up to 50 mT for the 100-μm powder and up to 150 mT for the 10-μm one. FC/ZFC ratio amounts to about 2 for the natural powder, while for the synthetic one, which is essentially pure material, it barely exceeds unity. FC/ZFC ratio can thus be viewed as a sensitive indicator of iron incorporation into rhodochrosite.  相似文献   

17.
The ground track of the annular eclipse of 3 October 2005 crossed the Iberian Peninsula. The main objective of this work was to analyze the variability of the solar irradiance and the total ozone column during the course of this event at El Arenosillo (Southwestern Spain). For achieving this goal, two Kipp & Zonen broadband radiometers (one for measuring total solar irradiance and other for measuring ultraviolet erythemal solar irradiance), one NILU-UV multi-band instrument and one Brewer spectroradiometer were used in this work. Total irradiance (310–2800 nm), and ultraviolet erythemal radiation (UVER) were recorded at a high frequency of 5 s, showing a strong reduction (higher than 80%) of the irradiance at the maximum solar obscuration which was of 79.6%. The irradiance decrease during the course of the eclipse was positively correlated with the percentage of eclipse obscuration, showing a very high agreement (R2～0.99). The irradiance recorded at selected wavelengths from the NILU-UV instrument shows a more pronounced decrease in the UV irradiance at the lower wavelengths during the solar eclipse. Finally, the evolution of the total ozone column (TOC) derived from Brewer and NILU instruments during the eclipse presented an opposite behavior: while the Brewer derived TOC values increase about 15 DU, the NILU derived TOC values decrease about 11 DU. This opposite behavior is mainly related to an artifact in the spectral irradiances recorded by the two instruments.  相似文献   

18.
The geochemical characteristics of mildly alkalic basalts (24–25 Ma) erupted in the southeastern Kerguelen Archipelago are considered to represent the best estimate for the composition of the enriched Kerguelen plume end-member. A recent study of picrites and high-MgO basalts from this part of the archipelago highlighted the Pb and Hf isotopic variations and suggested the presence of mantle heterogeneities within the Kerguelen plume itself. We present new helium and neon isotopic compositions for olivines from these picrites and high-MgO basalts (6–17 wt.% MgO) both to constrain the enriched composition of the Kerguelen plume and to determine the origin of isotopic heterogeneities involved in the genesis of Kerguelen plume-related basalts. The olivine phenocrysts have extremely variable 4He / 3He compositions between MORB and primitive values observed in OIB (∼90,000 to 40,000; i.e., R / Ra ∼8 to 18) and they show primitive neon isotopic ratios (average 21Ne / 21Neext ∼0.044). The neon isotopic systematics and the 4He / 3He ratios that are lower than MORB values for the Kerguelen basalts clearly suggest that the Kerguelen hotspot belongs to the family of primitive hotspots, such as Iceland and Hawaii. The rare gas signature for the Kerguelen samples, intermediate between MORB and solar, is apparently inconsistent with mixing of a primitive component with a MORB-like source, but may result from sampling a heterogeneous part of the mantle with solar 3He / 22Ne and with a higher (U, Th) / 3He ratio compared to typically high R / Ra hotspot basalts such as those from Iceland and Hawaii.  相似文献   

19.
Sulfur compounds in volcanic gases are responsible for the global cooling after explosive eruptions and they probably controlled the early evolution of the Earth's atmosphere. We have therefore studied the oxidation state of sulfur in aqueous fluids under the pressure and temperature conditions and oxygen fugacities typical for magma chambers (0.5–3 kbar, 650–950 °C, Ni–NiO to Re–ReO2 buffer conditions). Sulfur speciation was determined by Raman spectroscopy of quenched fluids trapped as inclusions in quartz. Our results show that sulfur in hydrothermal fluids and volcanic gases is much more oxidized than previously thought and in particular, some explosive eruptions may release a significant fraction of sulfur as SO3 or its hydrated forms. In the pressure range from 500 to 2000 bar, the equilibrium constant K1 of the reaction 2H2S + 3O2 = 2SO2 + 2H2O in aqueous fluids can be described by lnK1 = ?(57.1 ± 7.1) + (173,480 ± 7592)T? 1, where T is temperature in Kelvin. The equilibrium constant K2 for the reaction SO2 + ½O2 = SO3 in aqueous fluids, where SO3 may include hydrated forms, such as H2SO4, was found to be strongly pressure dependent, with lnK2 = ?(5.2 ± 5.7) + (19,243 ± 5993)T? 1 at 1500 bar; lnK2 = ?(11.1 ± 1.3) + (25,383 ± 1371)T? 1 at 2000 bar and lnK2 = ?(22.1 ± 2.2) + (37,082 ± 2248)T? 1 at 2500 bar. Our data imply that volcanoes may directly inject hexavalent sulfur in the form of H2SO4 into the atmosphere, not only on Earth, but possibly also on Venus and on Mars, when it was still tectonically active. Remote measurements from satellites may have underestimated the sulfur yield of some recent eruptions. Moreover, the mechanisms of the interaction of volcanic gases with the stratosphere need to be reconsidered.  相似文献   

20.
《Geofísica Internacional》2014,53(4):411-423
An investigation of the effect of some human activities on the magnetic susceptibility and frequency dependent susceptibility was conducted on top soil samples from, a commercial area, a motor park and a school environment in Jalingo, Taraba State, N-E Nigeria. The purpose was to assess the variation of magnetic susceptibility with different land use, detect pollution hotspots using magnetic proxy parameters and evaluate the contribution of superparamagnetic (SP) grain size contribution to the magnetic susceptibility from calculation of the frequency dependence of magnetic susceptibility (MS). The results of the mass specific low frequency magnetic susceptibility measurements showed significant enhancement with values ranging from 67.8 − 495.3 × 10−8 m3kg−1 with a mean value of 191.61 × 10−8 × m3kg−1 for the Jalingo College of Education (JCOE) data; 520.1 − 1612.8 × 10−8 m3kg−1 with a mean value of 901.34 × 10−8 m3kg−1 for the Jalingo main Market (JMM) and 188.5 − 1203.6 × 10−8m3kg−1 with an average value of 574 92 × 10−6 m3kg−1 for the Jalingo Motor Park (JMP). The significant magnetic enhancement indicates high concentration of ferrimagnetic minerals in the soil and hence increased pollution. The magnetic susceptibility of the different land use studied decreased in the order commercial area (market) > motor park > school premises. The results of the percentage frequency dependence susceptibility showed that most of the samples had a mixture of SP and coarse multi domain grains or SP grains < 0.05 µm. The value of χfd% range from 2.68 to 13.80% with an average value of 8.67% in the JCOE samples, 0.49 to 10.04% with an a-verage of 5.05% in the JMM samples and 0.56 to 13.04% with an average value of 5.86% in the JMP samples.  相似文献   

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