Physical And Chemical Characteristics Of Three-stage Fog Water In Deep Fog In City And Mountain In Eastern China

In recent years, the phenomenon of heavy fog weather has obviously increased in eastern China. Fog observation experiments for mountain clean area (Lushan) and city (Nanjing) are introduced successively in this paper. In the contrast of mountain fog physical and chemical characteristics , it is necessary to insight into the chemical composition of different size droplets in the fog city with combined atmospheric pollutants and the relationships of physical structure in Nanjing on behalf of the cities in eastern China and Lushan mountain for clean area. The outfield fog observation experiments were carried out in December 2013 in Nanjing and January 2016 in Lushan mountain. By using the observational data acquired from a field experiment conducted during this time period, it was able to investigate the contributions fromdifferent suspended aerosols with various sizes to the formation of fog droplets as well as the impacts of the ions in condensation nucleus on the chemical properties of the fog water. The observational data adopted in the present study consists of the concentrations of the water-soluble ions in three-stage fog droplets and also the particle-size aerosols, number distributions of the aerosol particles, distributions of the fog drop, meteorological factors and so on. The micro-physicochemical properties of the three-stages fog water (4-16?m for stage 3,16-22?m for stage 2, larger than 22?m for stage 1) as well as the particle-size aerosols are compared and discussed.The results shows that, fog droplets are mainly concentrated in the stage-3 (4-16?m)droplets phase, the stage-2 of (16-22?m) and the first level drops (>22?m) increase the quantity is relatively small. Aerosol particle size in 0.5-1 ?m in the largest decline, condenses the largest contribution to the growth. Small droplets continue to touch and grow into and big drops, and large drops in continue to capture droplets, and capture efficiency increases gradually, make the droplets change against the big end, droplets spectral correspondingly wider. Lushan cloud droplets is also the third highest number of droplets concentrations, and small drops in the relatively lower one order of magnitude. Compared with Lushan droplets,Nanjing fog droplets number concentration value is small, but the trend is more consistent,more gently, and the third level numerical similar small and in the second level drops.It is observed that the fog in Nanjing is acidic (pH=2.7-6.9), and the fog drops with smaller size have relatively stronger acidity. The second and the first level is relatively high, the average value is 4.58, 5.27 and 5.68, respectively. Little drops of the fog the highest conductivity value, the third level about the electrical conductivity of reaches more than 1000?s/cm. Average pH of three-stages cloud water in Lushan at all levels were 5.16, 5.11 and 4.79. It is a mild acidity. Conductivity within 33.1-268?s/cm, ion concentration is far lower than the Nanjing fog water.Determination of anion and cation concentration in the triple step about in 4-16 micronsdroplets are the highest in the fog in Nanjing, in the second and the first level in the fog.NO3-and SO42- have the highest concentration of anion ,but Cl- and NO2- have the lowest concentration, and the anion percentage is relatively stable. With the difference to the result that the concentration of SO42- has absolute advantage in previous Nanjing observation experiment, Nanjing atmospheric pollution has transformed from sulfuric acid to the nitrogen oxides primarily compound pollution. The concentration of Ca2+ in the highest in the stage 1,stage 2 and stage 3 have the highest concentration of NH4+, Na+, K+, and Mg2+ concentration is relatively low. Anionic NO3- and SO42- source similar, mainly absorbed sulphate aerosols and nitrate aerosol particles and gaseous contaminants, and points in the aerosol particle size diameter section of the anion NO3-and SO42- were showed higher values correspond. Ca2+ in fog water is mainly from the aerosol absorption, because decrease of cation Ca2+ concentration in the aerosol is the highest. In Lushan cloud water ion composition, cation the highest proportion of NH4+,the fog anion at all levels, the NO3- the highest proportion, followed by SO42-. The atmospheric pollution in Lushan has transformed from sulfate pollution into nitrogen oxide compound pollution.In Nanjing heavy fog, with the visibility of about 50 metres, formed due to the shortwave radiation reduced form stable inversion layer. The fog developed strongly and the height of fog top was about 500 m, in help to the accumulation of pollution aerosols and hygroscopic growth to droplets. Two clouds happened in Lushan is given priority to with the north wind,and wind speed is larger. With low temperature and low vapor pressure, wet air becomes droplets after the lifting of the mountain. Sampling points affected by radiation decrease less,but influenced by advection transport greatly. Compared with the existence of the Nanjing city thick fog droplets are more stable, Lushan cloud drops remain relatively short.