干旱区生态环境知识资源中心

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 x 0.224 m x 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 degrees 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 mu M m(-2) d(-1). The sum of major cations on white marble and red stone are 516.4 and 450.4 mu eq m(-2) d(-1), respectively while sum of major anions are 425.3 and 400.4 mu 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.