Deposition of atmospheric particles within the Buddhist cave temples at Yungang, China

The Buddhist cave temples at Yungang, China, are soiled at a rapid rate by the deposition of airborne particles. Average mass deposition rates to horizontal surfaces of 13.42 μg m −2 s −1 outdoors and 5.23 μg m −2 s −1 inside Cave 6 were measured over a 1 yr period in 1991–1992. These rates are comparable to the rates inferred by examination of historically accumulated deposits within the caves. The surface area coverage by coarse particles is dominated by particles larger than about 10–20 μm in diameter, while the mass flux is dominated by even larger particles greater than 20–30 pm in diameter. Comparison of the deposition rate in Cave 6, which retains its wooden temple front structure, to that in Cave 9 which is open to the outdoors shows that the temple front does provide some protection. During spring 1991, the deposition rate to horizontal surfaces in Cave 6 was 4.5 μg m −2s −1 compared to 13.4 μg m −2s −1 in Cave 9 and 21.5 μg m −2s −1 outdoors.