The Buddhist cave temples at the Yungang Grottoes, China, experience rapid soiling due to the deposition of airborne particles. Contributing sources include coal mining and combustion, fugitive road dust, and regional dust storms. Both particle and gas-phase air pollutants are characterized at that site. Annual average coarse (diameter, dp > 2.1 µm) particle concentrations outdoors average 378 µg/m3, increasing to more than 1200 µg/m3 during peak 24-hour periods. These coarse airborne particles include crustal dust (e.g., soil dust; over 80% of coarse mass) and carbon-containing particles (10%). Fine airborne particle concentrations (dp < 2.1 µm) outdoors average 130 µg/m3 and consist mainly of carbon-containing particles (45.5%) and crustal dust (24%). Airborne particle concentrations inside Cave 6 average approximately 60% of those outdoors. SO2 is the principal gas-phase air pollutant averaging 31 ppb outdoors and 19 ppb inside Cave 6 over the year studied. Other pollutant gases are present at lower average concentrations: NH3 (4-10 ppb), NO2 (4-6 ppb), HNO3 (0.1-0.2 ppb) and HCl (< 0.1 ppb).
Lynn Garry Salmon <>{