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1.
The deposition fluxes of inorganic compounds dissolved in fog and rain were quantified for two different ecosystems in Europe. The fogwater deposition fluxes were measured by employing the eddy covariance method. The site in Switzerland that lies within an agricultural area surrounded by the Jura mountains and the Alps is often exposed to radiation fog. At the German mountain forest ecosystem, on the other hand, advection fog occurs most frequently. At the Swiss site, fogwater deposition fluxes of the dominant components SO42− (0.027 mg S m−2 day−1), NO3− (0.030 mg N m−2 day−1) and NH4+ (0.060 mg N m−2 day−1) were estimated to be <5% of the measured wet deposition (0.85, 0.70 and 1.34 mg m−2 day−1, respectively). The corresponding fluxes at the forest site (0.62, 0.82 and 1.16 mg m−2 day−1, respectively) were of the same order of magnitude as wet deposition (1.04, 1.01 and 1.36 mg m−2 day−1), illustrating the importance of fog (or occult) deposition. Trajectory analyses at the forest site indicate significantly higher fogwater concentrations of all major ions if air originated from the east (i.e. the Czech Republic), which is in close agreement with earlier studies.  相似文献   

2.
Throughfall (TF) and wet only (WO) deposition along with SO2 and sulfate (SO42−) concentration in air at 4 urban and rural sites in southwestern China were monitored in order to understand the role of different forms of sulfur (S) emission to the S deposition and its effect in China. The sites were located in Chongqing, Hunan, and Guizhou provinces. S deposition at the most polluted site reached 15 g S m− 2 yr− 1. At three of the sites, located in the vicinity of several emission sources, dry S deposition is 2.1–4.2 times that of wet deposition, which is significantly higher than what is found in most other parts of the world.Main components in airborne particles (PM10) are (NH4)2SO4 and CaSO4 at the highly polluted Tie Shan Ping (TSP) site. Dust particles of gypsum (CaSO4) in the air are partly due to direct emission and partly from the reaction of calcium oxides and carbonates with sulfuric acid in the air. To illustrate the importance of sulfate emission to total S deposition we analyzed the source of S deposition based on both measurements and models. Results indicated that direct emission of SO42− particles could account for high proportion in total S deposition at the three most polluted sites.  相似文献   

3.
The fog meteorology, fog chemistry and fog deposition on epiphytic bryophytes were investigated from July 2000 to June 2001 in the Yuanyang Lake forest ecosystem. The elevation of the site ranges from 1650 to 2420 m, at which the high frequency of fog occurrence throughout the year has been thought to be of benefit to the establishment of the primary Taiwan yellow cypress forest [Chamaecyparis obtusa var. formosana (Hayata) Rehder] and to the extensive growth of the epiphytic bryophytes. A weather station including a visibility sensor and an active fog collector was installed for fog meteorological and chemical study. The fog deposition rate on epiphytic bryophytes was estimated by measuring the increase rate in plant weight when exposed to fog. Average fog duration of 4.7 and 11.0 h per day was measured in summer months (June to August) and the rest of the year, respectively. November 2000 was the foggiest month in which the average fog duration reached 14.9 h per day. The ionic composition of fog water revealed that the area was less polluted than expected from literature data. The in situ exposure experiments done with the dominant epiphytic bryophytes showed an average fog deposition rate of 0.63 g H2O g−1 d. w. h−1, which approximated 0.17 mm h−1 at the stand scale. The nutrient fluxes estimated for February 2001 showed that for all ions, more than 50% of the ecosystem input was through fog deposition. These results demonstrate the importance of epiphytic bryophytes and fog deposition in nutrient cycling of this subtropical montane forest ecosystem. The incorporation of fog study in the long-term ecosystem research projects is necessary in this area.  相似文献   

4.
Measurements of fog and rain water chemistry at the summit of Mt. Fuji, the highest peak in Japan, as well as at Tarobo, the ESE slope of Mt. Fuji in September 2002. The pH of fog and rain water sampled at Mt. Fuji varied over a range of 4.0–6.8. Acidic fogs (pH < 5.0) were observed at the summit when the air mass came from the industrial regions on the Asian continent. The ratio of [SO42−]/[NO3−] in the fog water was lower at Tarobo than at the summit. High concentrations of Na+ and Cl− were determined in the rain water sampled at the summit, possibly because of the long-range transport of sea-salt particles raised by a typhoon through the middle troposphere. The vertical transport of sea-salt particles would influence the cloud microphysical properties in the middle troposphere. Significant loss of Mg2+ was seen in the rain water at the summit. The concentrations of peroxides in the fog and rain water were relatively large (10–105 μM). The potential capacity for SO2 oxidation seems to be strong from summer to early autumn at Mt. Fuji. The fog water peroxide concentrations displayed diurnal variability. The peroxide concentrations in the nighttime were significantly higher than those in the daytime.  相似文献   

5.
To better understand the role of terpenic compounds in atmospheric chemistry the influence of sobrerol, a water-soluble product of photochemical autoxidation or ozonolysis of -pinene, on the rate of S(IV) autoxidation was studied. Laboratory experiments were performed under heterogeneous conditions, at constant supply with S(IV) by dissolution of CaSO3.1/2 H2O fine particles and with air oxygen by diffusion through a planar gas-liquid interface. The progress of S(IV) autoxidation, uncatalysed or catalysed by Fe2(SO4)3 or CoSO4, was followed conductometrically. The inhibiting effect of sobrerol was discussed in terms of the chain reaction terminated in a step linear with respect to sulphoxy radicals. A method was proposed for quantification of the inhibiting effect and the rate constant (2.0–3.8)108 M–1s–1 was given for the step eliminating sulphate radicals. Further consequences of the inhibition: shifting the reaction locus from the gas-liquid (droplet) interface to the liquid (droplet) bulk and strong oscillations in the rate of S(IV) autoxidation resulting of the activity of sobrerol-derived radicals were also shown.  相似文献   

6.
Experimental data from two field experiments on ground based clouds were used to study the distribution of formic acid, acetic acid, ammonia and S(IV) species between liquid and gas phase. The ratio of the concentrations of these compounds between the phases during concurrent measurements was compared to ratios expected according to Henry's law (considering the pH influence). Large discrepancies of several orders of magnitude were seen. Three hypotheses have been investigated to explain the observed discrepancies: The existence of a microscale equilibrium which does not persist in a bulk sample, a thermodynamic shift of the equilibrium due to competing reactions, and nonequilibrium conditions due to mass transfer limitations. Approximate quantitative calculations show that none of these hypotheses is sufficient to explain all of the discrepancies, so a combination of different effects seems to be responsible for this observation. The same theoretical considerations also suggest that mass transfer limitation may be an important factor for highly soluble compounds. The data presented here indicates that it is not possible to simply extrapolate interstitial gas phase composition from measured bulk liquid phase concentrations of a fog or cloud.Notation [r max] liquid phase molar uptake rate (mol l–1 s–1) - [A g ] concentration ofA in gas phase (atm) - [A l ] concentration ofA in liquid phase (mol l–1) - [A g , 0] concentration ofA in gas phase (atm) at time 0 - LWC liquid water content (g m–3) - R universal gas constant (0.082 l atm mol–1 K–1 - D g diffusivity (for all gases 0.1 cm2 s–1 was used) - K H * effective Henry's law coefficient (mol l–1 atm–1) - t f lifetime of fog droplet (s) - a droplet radius (cm) - accommodation coefficient - R factor of discrepancy - T temperature (K) - v mean molecular speed (cm s–1) formic acid: 35 000 acetic acid: 31 000 ammonia: 58 000  相似文献   

7.
A field study was conducted at a mountain-top site in northwestern Colorado. Supercooled cloud water, collected as a function of droplet size, was analyzed for anions, cations and trace elements. Enrichment factors (EF) of SO 4 2– , K+, Na+ and Cl– relative to crustal and marine reference elements (Al and Na) were calculated to determine whether chemical fractionation of the aerosol occurs during cloud droplet formation. The largest EF's for all ions were found for droplets less than 10–15 µm diameter. Ratios of the small to large droplet mean EF's ranged from 1 to 2, for SO 4 2– relative to both Al and Na+, to 10 to 12 for Na+, Cl– and K+, relative to Al. EF's of K+ and Cl– in the bulk cloud water were in crustal and marine proportions, respectively. It was concluded that although bulk could chemistry may indicate a lack of enrichment of a species, this may not be true throughout the droplet size distribution. The higher enrichments in small droplets is likely a result of their formation on small aerosol particles whereas the large droplets form on the largest aerosol particles. This may suppress EF's in precipitation relative to the total aerosol.  相似文献   

8.
Within the framework of IDAF (IGAC DEBITS AFRICA: International GlobalAtmospheric Chemistry/DEposition of Biogeochemically Important TraceSpecies/Africa) network, data analysis is realised on precipitation chemical composition collected in Zoétélé, in Southern Cameroon. This station, located atabout 200 km from the Atlantic Ocean, is representative of a so-called `Evergreen Equatorial Forest' ecosystem. An automatic wet-only precipitation collector was operated at the station from 1996 to 2000. The rainfall regime, associated with eastward advection of moist and cool monsoon air masses, amounts to an average of 1700 mm/year. Inorganic and organic content of the precipitation were determined by IC in 234 rainfall events, representing a total 4,583 mm of rainfall from an overall of 7,100 mm.The mean annual precipitation chemistry and wet deposition fluxes characteristic of an African equatorial forest are quantified. Typical atmospheric gases and particles sources influence the precipitation chemical content and the associated deposition of chemical species. Indeed, hydrogen concentration is the highest (12.0 eq.L–1) of the IDAF measurements, leading to acid rains with a low mean pH 4.92. The mineral species are dominated by nitrogenous compounds (NH4 +:10.5 and NO3 –: 6.9 eq.L–1), Ca2+ (8.9 eq.L–1) and SO4 2 – 5.1 eq.L–1. Relationship between Ca2 + and SO4 2 – indicated aterrigeneous particulate source and an additional SO4 2 – contributionprobably due to swamps and volcano emissions. Na+ and Cl–concentrations, around 4.0 eq.L–1, seem very low for this site,accounting for the marine source. Besides, strong correlations between NH4 +/K+/Cl– indicate the biomass burning originof these species. Accordingly, precipitation chemistry in Zoétéléis influenced by three major sources: biogenic emissions from soil and forest ecosystems, biomass burning from savannah, and terrigenous signature from particles emissions of arid zones; and three minor sources: marine, volcano and anthropogenic. In spite of the relatively low concentration of all these elements, the wet deposition is quite significant due to the high precipitation levels, with for example a nitrogenous compounds deposition of 34 mmol.m–2.yr–1.  相似文献   

9.
Summary We measured ionic compounds in rain and fog at two remote sites in the South Island of New Zealand and at two sites in the Fichtelgebirge, F. R. of Germany. In the Fichtelgebirge high concentrations of H3O+, NO 3 – , SO 4 2– and NH 4 + indicate an anthropogenic impact, whereas in New Zealand concentrations were generally very low except for seasalt derived ions such as Na+, Cl– and Mg2+ at one site near the coast which receives precipitation from maritime sources. Remarkable differences occur in the acidity of hydrometeors in New Zealand and the Fichtelgebirge. The low pH values of the Fichtelgebirge (pH 4.2) are due to an excess of strong mineral acids, whereas the acidity of rain and fog in New Zealand is controlled by dissolved CO2 (pH 5.6). In the Fichtelgebirge, acidity in fog is much higher than in rain, whereas no difference could be observed in New Zealand due to marine influences and the lack of strong mineral acids. Rain of different trajectories of air flow in New Zealand is accompanied by a wide range of ionic concentrations.
Zusammenfassung An zwei entlegenen Meßstellen der Südinsel Neuseelands und an zwei Meßstellen im Fichtelgebirge haben wir die Ionen im Regen und Nebel gemessen. Die Luftverschmutzung im Fichtelgebirge ist gekennzeichnet durch hohe Konzentrationen von H3O+, NO 3 – , SO 4 2– und NH 4 + . Die Ionenkonzentrationen im neuseeländischen Niederschlagswasser waren durchwegs sehr gering mit Ausnahme von Na+, Cl– und Mg2+, die aus Seesalzen stammen und nur in einer küstennahen Meßstelle bei günstigen Wetterlagen bestimmt werden konnten. Große Unterschiede bestehen in der Azidität der Hydrometeore. Während im Fichtelgebirge starke Mineralsäuren niedrige pH-Werte (pH 4.2) bewirken, wird die Azidität des Regens und des Nebels an den neuseeländischen Meßstellen durch gelöstes CO2 kontrolliert (pH 5.6). Im Fichtelgebirge ist die Azidität im Nebel erheblich höher als im Regen. Im Gegensatz dazu konnten wir keinen Unterschied in der Azidität zwischen Nebel und Regen in Neuseeland beobachten, was wir mit dem marinen Einfluß und dem Fehlen starker Mineralsäuren erklären. Unterschiedliche Trajektorien der atmosphärischen Strömung in Neuseeland unterscheiden sich zugleich in ihren Ionenkonzentrationen im Regen.

With 6 Figures  相似文献   

10.
The changing chemical composition of cloud water and precipitation in the Western Sudety Mountains are discussed against the background of air-pollution changes in the Black Triangle since the 1980s until September 2004. A marked reduction of sulphur dioxide emissions between the early 1990's and the present (from almost 2 million tons to around 0.2 million tons) has been observed, with a substantial decline of sulphate and hydrogen concentration in cloud water (SO42− from more than 200 to around 70 μmol l− 1; H+ from 150 to 50 μmol l− 1) and precipitation (SO42− from around 80 to 20–30 μmol l− 1; H+ from around 60 to 10–15 μmol l− 1) samples. At some sites, where fog/cloud becomes the major source of pollutants, deposition hot spots are still observed where, for example, nitrogen deposition can exceed 20 times the relevant critical load. The results show that monitoring of cloud water chemistry can be a sensitive indicator of pollutant emissions.  相似文献   

11.
Radiative Heat Transfer and Hydrostatic Stability in Nocturnal Fog   总被引：1，自引：0，他引：1  
We have performed a one-dimensional and transient radiative heat transfer analysis in order to investigate interaction between atmospheric radiation and convective instability within a nocturnal fog. The radiation element method using the Ray Emission Model (REM2), which is a generalized numerical method, in conjunction with a line-by-line (LBL) method, is employed to attain high spectral resolution calculations for anisotropically scattering fog. The results show that the convective instability has a strong dependence on radiative properties of the fog. For the condition of a 20-m droplet diameter and liquid water content of 0.1 × 10–3 kg m–3;, the temperature profile within the fog becomes S shaped, and a convective instability layer forms in the middle or lower level of the fog. However, for the same water content and a 40-m diameter droplet, no strong convective instability layer forms, whereas for a 10-m diameter droplet a strong convective instability is observed.  相似文献   

12.
Fogs observed over Incheon international airport (IIA) in the west coast of Korea from January 2002 to August 2006 are classified into categories of coastal fog, cold sea fog, and warm sea fog based on the areal extent of the fogs and the difference between the air temperature (T) and the SST, i.e., cold sea fog if TSST = T-SST>0oC and warm sea fog if TSST <0oC. The numbers of coastal, cold, and warm sea fog cases are 64, 26, and 9. Coastal fogs form most frequently in winter, while cold sea fogs occur mostly in summer and warm sea fogs are observed from January to May but not in November and December. On average the air gets colder by 1.6oC during the three hours leading up to the coastal fog formation, and an additional cooling of 1.1oC occurs during the fog. The change in the dew point temperature (Td) is minimal except during the fog (0.6oC). Decreases in T for the cold and warm sea fogs are relatively smaller. The average Td is higher than SST during the cold sea fog periods but this Td is more than 4oC higher than that for the corresponding non-fog days, suggesting that cold sea fogs be formed by the cooling of already humid air (i.e., Td>SST). Increases of Td are significant during the warm sea fog periods (1.4oC), implying that efficient moisture supply is essential to warm sea fog formation. Four major synoptic patterns are identified in association with the observed fogs. The most frequent is a north Pacific high that accounts for 38% of cases. Surface or upper inversions are present in 77%, 69%, and 81% of the fog periods for coastal, cold, and warm sea fogs, respectively.  相似文献   

13.
This paper presents dry deposition flux and deposition velocity of atmospheric particles on white marble and red stone at Dayalbagh, a suburban site of semi arid region, which is 10 km away from the industrial sector of the Agra city where due to agricultural practices vegetation predominates. The wind speed at Agra is mostly in the range of 1–2 m s–1. The atmospheric calm conditions at Agra in summer, monsoon, and winter seasons are 47%, 35%, and 76%, respectively. Industrial areas of the city are away from Dayalbagh and are located in the NE, E, SE, and SW sectors. The main industrial activities, which are in operation in Agra city and its outskirts, are foundry and forging industry. The other industrial activities in Agra are rubber processing, lime oxidation and pulverization, chemicals, engineering and brick refractory kilns. Dry deposition samples were collected on dry days on white marble and red stone (0.224 m × 0.224 m × 0.02 m) using surface washing method. Both slabs were fixed to an iron stand (1.5 m height) at an angle of about 80 from the horizontal and exposed for 24 h on the roof of the faculty building. The order of deposition flux on white marble is NH4+ > Mg2+ > Ca2+ > Na+ > Cl– > K+ > NO3– > SO42– > F– and that on red stone is NH4+ > Mg2+ > Ca2+ > SO42– > Na+ > NO3– > K+ > F– > Cl–. Average dry deposition flux of major ions varies from 3.4 to 128.5 M m–2 d–1. The sum of major cations on white marble and red stone are 516.4 and 450.4 eq m–2 d–1, respectively while sum of major anions are 425.3 and 400.4 eq m–2 d–1 on white marble and red stone, respectively. Higher deposition of all ions was observed when wind blows from NE as most of the Agra Iron foundries and Ferozabad glass industries lie in this direction. The mean values of dry deposition velocity of ions vary between 0.22 cm s–1 to 1.49 cm s–1. Deposition velocity for all ions is higher on white marble than red stone inspite of rougher surface of red stone as compared to white marble. This could be due to the chemical nature of white marble, which is made of dolomite and hence adds significant amount of ions by dissolution during washing. Seasonally the deposition velocity was highest in winter.  相似文献   

14.
This study describes the chemical composition of dry deposition collected at a highway traffic site in central Taiwan during daytime and nighttime periods by using a dry deposition plate (DDP) and water surface sampler (WSS). In addition, the characterization for mass and water-soluble species of total suspended particulate (TSP), both PM2.5 and PM10, was studied at the study site from August 22 to November 30, 2006. Dry deposition fluxes of ambient air particulates and inorganic species (Na+, NH4+, K+, Mg2+, Ca2+, Cl−, NO3− and SO42−) were analyzed by Ion Chromatography (DIONEX-100).Results of the particulate dry deposition fluxes and mass concentrations are higher in the water surface sampler with respect to the dry deposition plate used in this study. Statistical results also showed the average dry deposition flux of the ionic species (Na+, NH4+, K+, Cl−, NO3− and SO42−) obtained by the DDP and WSS displayed significant differences. Also, the average concentrations of Mg2+ and, Ca2+ were statistically the same at this study site.  相似文献   

15.
Summary Vertical profiles of H2O, CO2, O3, NO and NO2 were measured during the Hartheim Experiment (HartX) to develop and calibrate a multi-layer resistance model to estimate deposition and emission of the cited gaseous species. The meteorological and gas concentration data were obtained with a 30 m high telescopic mast with 7 gas inlets located at 5 m intervals and meteorological sensors at 5, 15 and 30 m above ground; a complete gas profile was obtained every 9 min 20 s. Measured profiles were influenced by several exchange processes, namely evapotranspiration, dewfall, assimilation of CO2 in the tree crowns, soil respiration, deposition of NO2 and O3 to the soil and advection of NOx from the nearby highway. Surprisingly, no decrease in O3 concentration was observed in the crown layer during daytime, probably due to the relatively low density of foliage elements and strong turbulent mixing.The advantage of measuring in-canopy profiles is that turbulent exchange coefficients need not be estimated as a prerequisite to obtaining vertical flux estimates. In recent years, flux-gradient relationships in canopies have been subject to many criticisms. If fluxes are calculated at several heights considering only the transfers between the turbulent air and the interacting surfaces at a certain height, and those fluxes are then integrated vertically in a subsequent step, then exchange estimates (deposition or emission) can be obtained independent of turbulent exchange conditions.Typical estimated deposition velocities calculated for a 3-day period are between 4 and 10 mm/s for NO2 and about 4–9 mm/s for O3 (day and night values respectively). This leads to deposition rates of about 20–40 ng N/m2s for NO2 and about 30–40 mg O3/m2 deposited daily under the conditions encountered during HartX. Sensitivity tests done with the best available and most realistic values for model parametrization have shown that sensitivity is large with respect to the soil and cuticula resistances as well as for gas-phase ozone destruction and that more research is required to describe the effectiveness of cuticula and soil in modifying sink characteristics for NO2 and O3.With 12 Figures  相似文献   

16.
人为大气污染物对一次冬季浓雾形成发展的影响研究   总被引：8，自引：2，他引：6  
贾星灿  郭学良 《大气科学》2012,36(5):995-1008
基于WRF/Chem模式和雾的观测资料,开展了包含和不包含人为污染排放源两种大气背景条件下的数值模拟对比试验,在此基础上探讨了人为污染物对2009年12月1日发生在我国华北和华东地区的一次浓雾天气过程的影响机理.结果表明,在考虑污染排放源时,模式模拟的雾的空间分布和强度变化与卫星、能见度仪和微波辐射计的观测更为接近.污...  相似文献   

17.
The paper presents monitoring results and environmental pollution assessment for the Gdask-Sopot-Gdynia Tricity (Poland), based onanalysis of precipitation. Precipitation samples were collected over a period of 12 months (January–December 1998) at ten locations in the Tricity. The following selected ions were determined in the samples:SO4 2–, F–, Cl–, NO3 –,PO4 3–, NH4 +, Na+,Mg2+, Ca2+, K+. The results were subjected to full statistical evaluation. Values of the parameters determined were correlated with each other. An attempt was made to explain co-occurrences of certain ions and the significance of their mutual effects. Pollutant concentrations and loads in precipitation were also correlated with data on wind direction and temperature in the region.Deposition of pollutants was very high in spring due to the prevailing air circulation patterns and low temperatures. Analysis of the correlations between co-occurring ions confirmed the significant impact of the location (sea coast) on the composition of rain water. Ionic ratios in rainwater were similar to those observed for sea salt samples. In addition, heavy traffic was most probably responsible for high concentrations of various forms of nitrogen and sulphates in the vicinity of major highways.  相似文献   

18.
In the present study, the wet and dry depositions of particulate NO3−, SO42−, Cl− and NH4+ were measured using a wet/dry sampler as a surrogate surface. Gas phase compounds of nitrogen, sulfur and chloride (HNO3, NH3, SO2 and HCl) were measured by an annular denuder system (ADS) equipped with a back up filter for the collection of particles with diameter ≤ 5 μm. Ambient concentrations of NO, NO2 and SO2 were also taken into consideration. Sampling was conducted at an urban site in the center of the city of Thessaloniki, northern Greece. The presence of the aerosol species was examined by cold/warm period and the possible compounds in dry deposits were also considered. Dry deposition fluxes were found to be well correlated with ambient particle concentrations in order to be used for the calculation of particle deposition velocity. Average particulate deposition velocities calculated were 0.36, 0.20, 0.20 and 0.10 cm s− 1 for Cl−, NO3−, SO42− and NH4+, respectively. Total dry deposition fluxes (gas and particles) were estimated at 3.24 kg ha− 1 year− 1 for chloride (HCl + p-Cl), 9.97 kg ha− 1 year− 1 for nitrogen oxidized (NO + NO2 + HNO3 + p-NO3), 5.32 kg ha− 1 year− 1 for nitrogen reduced (NH3 + p-NH4) and 15.77 kg ha− 1 year− 1 for sulfur (SO2 + p-SO4). 70–90% total dry deposition was due to gaseous species deposition. The contribution of dry deposition to the total (wet + dry) was at the level of 60–70% for sulfur and nitrogen (oxidized and reduced), whereas dry chloride deposition contributed 35% to the total. The dry-to-wet deposition ratio of all the studied species was found to be significantly associated with the precipitation amount, with nitrogen species being better and higher correlated. Wet, dry and total depositions measured in Thessaloniki, were compared with other countries of Europe, US and Asia.  相似文献   

19.
Methanesulfonate (MS–) and non-sea-salt sulfate (nss-SO 4 2– ), two of the major oxidation products of atmospheric dimethylsulfide (DMS), have been continuously measured in rainwater at three remote islands in the Southern Indian Ocean: Amsterdam since 1991, Crozet since 1992, and Kerguelen since 1993. The annual volume weighted mean (VWM) concentrations of nss-SO 4 2– in rainwater were 3.19, 3.04 and 4.57 eq l–1 at Amsterdam, Crozet, and Kerguelen, respectively while the VWM of MS– were 0.24, 0.15 and 0.30 eq l–1, respectively. At all three islands, MS– presented a well-distinguished seasonal variation with a maximum during summer whereas the seasonal variation of nss-SO 4 2– was less pronounced, possibly due to the increased anthropogenic influence during the winter period. Furthermore, MS– presented significant interannual variations, in particular at Amsterdam and Crozet, which is closely related to the sea-surface temperature (SST) anomalies). Finally, the nss-SO 4 2– deposition at Crozet Island presented a decreasing interannual trend, reflecting probably reductions in sulfur emissions from Southern Africa. On the contrary no interannual tendency was observed in the nss-SO 4 2– concentrations at Amsterdam Island, indicating that the biogeochemical sulfur cycle at this area is mainly influenced by biogenic emissions.  相似文献   

20.
Cloud/fog water samples were collected at Daekwanreung (840 m msl), a ridge site, in South Korea, from March 2002 to September 2003, by using a Caltech type, self fabricated active strand cloud water collector. The pH, electrical conductivity and major ion concentrations were analyzed. The cloud water pH ranged from 3.6 to 6.8 with an average of 5.2, which was close to the atmospheric neutral point. However, the pH calculated from average concentrations of H+ was 4.7, indicating the cloud/fog water was weakly acidified. SO4 2−, NO3 − and NH4 + are predominant ions of which average concentrations were 203.1, 128.1, and 211.7 μeq⋅L−1, respectively. Samples were categorized into four groups by applying 48-hour back trajectory analysis, using the HYbrid Single-Particle Largrangian Integrated Trajectory (HYSPLIT) model. Chemical compositions for the four cases significantly differed from each other. For air masses transported from the East Sea (group E), sea salt concentrations, including Na+, Cl− Mg2+, were relatively high. Principal acidifying pollutants, such as NO3 − and nss-SO4 2−, significantly increased in the case of air masses transported from the Northeast Asian continent through North Korea (group N) and air masses from the Seoul metropolitan area (group W). However, the mean pH of group N was the highest while the mean pH of group W was the lowest. This suggests that most NO3 − and nss-SO4 2− in cloud/fog water was neutralized by ammonia and calcium compounds under the influence of air masses transported from Northeast Asia. N/S ratio for the group W was significantly higher than those for the other three groups, suggesting nitrogen species transported from the Seoul metropolitan area contributed to acidification of cloud/fog water at Daekwanreung. Principle Component analysis (PCA) was applied to the cloud/fog water data for presenting characteristics in the four different categories.  相似文献   

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