敦煌莫高窟大气可吸入颗粒物的化学元素特征

Chemical elemental characteristics of atmospheric inhalable particulates in Dunhuang Mogao Grottoes

利用电感耦合等离子体质谱仪测定了敦煌莫高窟洞窟内外大气可吸入颗粒物中27种元素的质量浓度。结果表明:典型地壳元素Na、Mg、Al、K、Ca、Fe占测定元素总质量浓度的96%以上。通过洞窟内外PM2.5与PM10-2.5中元素质量浓度对比发现,Li、Na、Mg、K、Ca、Co、Ni、Zn、Sr、Cs、Ba、U等元素主要存在于PM10-2.5中。沙尘天气时,洞窟外环境中的Co、Ga、As、Cs、Ba元素质量浓度降低,表明沙尘过程对这些元素有稀释作用。富集因子分析显示,洞窟内外可吸入颗粒物中B、Na、Ca、Mn、Cu、Zn、As、Sr、Tl、Pb、Bi、U的EF值均大于10,表明人类活动产生的污染物对以上元素的富集起主要作用。富含Ca、Mn、Cu、Zn、As、Pb等元素的矿物颜料在洞窟壁画制作中被大量使用,其对区域环境大气可吸入颗粒物微量元素的富集也有一定的贡献作用。游客数量与洞窟内外元素Bi浓度存在较显著的线性关系,表明环境中的Bi元素浓度变化受游客活动影响。本研究首次对莫高窟大气可吸入颗粒物中元素含量进行了监测和分析,研究成果为石窟文物及其赋存环境中可吸入颗粒物污染的治理及控制提供了科学依据。

This study investigates characteristics of atmospheric inhalable particulates in the Dunhuang Mogao Grottoes,a world cultural heritage site located at the western end of Hexi Corridor that is extremely dry.In this study,an atmospheric particulate sampler(Dichotomous Partisol-Plus Model 2025,Thermo Scientific,USA)was used to collect atmospheric particulate matter inside and outside the caves of Dunhuang Mogao Grottoes,and inductively coupled plasma mass spectrometry(ICP-MS,X-7,Thermo Elemental,USA)was used to measure the mass concentrations of 27 elements.The results showed that the typical crustal elements(Na,Mg,Al,K,Ca,and Fe)accounted for more than 96%of the total mass concentration of the measured elements.The Ca content was the highest at approximately 60%.In sand dust weather conditions,the mass concentrations of Li,Be,Zn,and various other elements increased by a factor of fourcompared to sunny weather conditions,whereas the mass concentrations of Co,Ga,As,Cs,and Ba decreased.This indicates that sand dust weather has a greater impact on the concentrations of these elements.Additionally,the concentrations of B,Sc,Ga,As,Cs,Tl,Pb,and various other elements are low in spring but high in winter,which is possibly related to fossil fuel burning in winter in rural areas around the Mogao Grottoes.Enrichment factor(EF)analysis showed that the EF concentrations of B,Na,Ca,Mn,Cu,Zn,As,Sr,Tl,Pb,Bi,and U in inhalable particles were all greater than 10.This suggests that pollutants from human activity play a key role in the variation of these elements.The Pb element EF value exceeded 250,and mainsource of Pb and Zn isfossil fuel burning.This is the first study monitoring and analyzing thecontent of various elements in atmospheric inhalable particulate matter in the Dunhuang Mogao Grottoes,and these results provide scientific basis for the future treatment and control of inhalable particulate matter pollution at this site and the surrounding environment.