STUDY ON THE CHEMICAL CHARACTERISTICS OF POLLUTING FOG IN GUANGZHOU AREA IN SPRING

Samples of fog water collected in the area of Guangzhou during February, March and April of 2005 are used in this work to study the chemical composition of fog water in polluting fog there. Three typical episodes of polluting fog are analyzed in terms of ionic concentration and their possible sources. It is found that the concentration of various ions in fog water is much higher than those in rainwater. Fog not only blocks visual range but contains liquid particles that result in high degree of pollution and are very harmful to human health. SO4= is the anion with the highest concentration in fog water, followed by NO3-. For the cation, Ca++ and NH4+ are the highest in concentration. It is then known that rainwater is more acidic than fog water, indicating that ionic concentration of fog water is much higher than that of rainwater, but there are much more buffering materials in fog water, like NH4+ and Ca++. There is significant enrichment of Ca++, SO4=, and Mg++ in fog water. In the Guangzhou area, fog water from polluting fog is mainly influenced continental environment and human activity. The episodes of serious fog pollution during the time have immediate relationships with the presence of abundant water vapor and large amount of polluting aerosol particles.

Fog composition along the Yangtze River basin: Detecting emission sources of pollutants in fog water

To investigate the fog chemistry along the Yangtze River basin, a field observation experiment was performed from Shanghai to Vv＇uhan during November 2015. Fifteen fog water samples were collected by using a three-stage Caltech Active Strand Cloud water Collector （CASCC）. The three-stage CASCC was mounted on the board of a ship. PH, electrical conductivity （EC）, H202, HCHO, S（ll0, ten inorganic ions, seven organicacids and sixteen trace metal elements were measured in this study. The pH of fog water samples ranged from weakly acidic （pH 4.3） to weakly alkaline （pH 7.05） and the EC ranged from 32.4 to 436.3 μS/cm. The main cations in fog water were NH^4＋ and Ca2＋, accounting for 12.35% and 29.07% of those inorganic ions, respectively. In addition, SO24- and NO^-3 contributed to 25.52% and 12.93% to total anion concentrations respectively. Moreover, the dominant kinds of organicacids were formate and oxalate, occupying 45.28% and 28.03% of the total organicacids, respectively. For trace metal elements in fog samples, Al, Fe, Zn, and Ba revealed 34.6%, 16.4%, 19.3%, and 20.9% contributions to these sixteen trace element concentrations, respectively. The results indicated that pollutants were mainly from human activities, including fossil fuel combustion, biomass burning, steel-making, stone quarrying and sand digging. Besides, natural sources including natural background levels and long-range transport of sea salt particles also aggravated the pollution levels in the fog events along the Yangtze River.