AIRBORNE POLLUTANTS IN THE BUDDHIST CAVE TEMPLES AT THE YUNGANG GROTTOES, CHINA

The Buddhist cave temples at the Yungang Grottoes, China, experience r apid soiling due to the deposition of airborne particles. Contributing sources include coal mining and combustion, fugitive road dust, and r egional dust storms. Both particle and gas-phase air pollutants are ch aracterized at that site. Annual average coarse (diameter, d(p) > 2.1 mum) particle concentrations outdoors average 378 mug/m3, increasing t o more than 1200 mug/m3 during peak 24-h periods. These coarse airborn e particles include crustal dust (e.g., soil dust; over 80% of coarse mass) and carbon-containing particles (10%). Fine airborne particle co ncentrations (d(p) less-than-or-equal-to 2.1 mum) outdoors average 130 mug/m3 and consist mainly of carbon-containing particles (45.5%) and crustal dust (24%). Airborne particle concentrations inside cave 6 ave rage approximately 60% of those outdoors. SO2 is the principal gas-pha se air pollutant averaging 31 ppb outdoors and 19 ppb inside cave 6 ov er the year studied. Other pollutant gases are present at lower averag e concentrations: NH3 (4-10 ppb), NO2 (4-6 ppb), HNO3 (0.1-0.2 ppb), a nd HCI (<O.1 ppb).