科研之友
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摘要
With the purpose of exploring the characteristics of atmospheric particulate pollution at the Mogao Grottoes，the samples of PM2. 5 and PM10~2. 5 were collected in Cave 16 and exterior environment of Cave 72 from April to December，2014. The researcher conducted contrastive analysis on the variation and influence factors of the water-soluble ions in the samples，and studied their main sources by the approach of Principal Component Analysis（PCA）. The results are as follows：（1）The main wind direction at Mogao Grottoes area is south wind and the frequency of wind with sand is only 0. 01%，which is unfavorable to the diffusion of pollutants.（2）The total concentration of water-soluble ions of PM2. 5 and PM10~2. 5 in the exterior environment of Cave 72 are 6. 1±4. 0 μg·m-3 and 12. 2±9. 1 μg·m-3，while in the interior environment of Cave 16 are 3. 7±0. 8 μg·m-3 and 7. 5±1. 6 μg·m-3. SO24-，Ca2+，NO-3，Na+，and Cl- are the main components of water-soluble ions. As for the proportion of water-soluble ions of PM2. 5 and PM10~2. 5 in the exterior environment，SO24-，NO-3，and Ca2+ together account for 79. 24% and 76. 81%. In the interior environment，the number is 80. 61% and 77. 74%. The Secondary ions originate mainly from stationary pollution sources.（3）The ratio of each ion concentration in PM2. 5 and PM10~2. 5 are 0. 33~0. 88（outside the cave）and 0. 25~0. 94（inside the cave）. 9 water-soluble ions are different in terms of their concentration degrees in different particle sizes. Sand storms from March to May，rainfalls from July to September，straw burning in rural areas in November，and coal burning for heating in winter have some effects on water-soluble ions. The number of tourists inside the caves has certain correlation with NH4+ and NO3- from the perspective of PM2. 5（R2=0. 27，0. 35），and with NH4+（R2=0. 31）from PM10~2. 5.（4）Owing to the sand and dust weathers，the concentration of Cl-，SO24-，Na+，K+ and Ca2+ increase in the PM2. 5 and PM10-2. 5 inside and outside the cave. The results indicate that micro-environment at the Mogao Grottoes is mainly influenced by the regional meteorological factors. Therefore，the caves should be closed during inclement weather.（5）The atmospheric environment at Mogao Grottoes area is alkaline. （6） The main resources causing the increase of PM2. 5 and PM10~2. 5 are crop burning in local areas，secondary pollution sources，sand and dust，and dried-out Daquan River.
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