金沙遗址博物馆大气污染特征研究

为全面了解金沙遗址博物馆遗址区空气污染特征及污染物来源,在2019年秋季对遗址保护厅内外大气中细颗粒物(PM_2.5)和挥发性有机物(VOCs)进行了观测,并对各自化学组分进行了全面分析。结果发现:金沙遗址博物馆遗址保护厅内外PM_2.5污染严重,平均质量浓度分别为77.0μg/m³和94.6μg/m³;受人为影响程度的不同,室内昼夜差异明显强于室外。室外的OM、NO₃^-和SO₄^2-浓度高于室内,而室内的NH+4和典型的地壳元素(K⁺、Mg²⁺和Ca²⁺)浓度高于室外;受化学组成的影响,室内外PM_2.5分别呈碱性和酸性。地壳元素在整体元素中占据绝对主导,室内外占比分别可达82.8%和84.4%。通过富集因子分析得知Cu(室外)、Ag、Cd、Sb元素均达到了重度富集。室内外VOCs浓度几乎相同,分别为81.2×10^-9和81.3×10^-9,其中烷烃的贡献比例最高,分别为44%和46%;源自机动车、工业溶剂涂料使用、燃油挥发及生物质燃烧等人为源的VOCs物质在室外的浓度要明显高于室内。这些研究结果对于金沙遗址博物馆遗址区空气质量的全面了解、土遗址及其中文物的高质量保存和提供优质的参观环境具有重要意义。     

SIMULATION OF RIDGE-WEATHERING EFFECTS ON THE GROUND MOTION CHARACTERISTICS

Seismic responses of weathered ridge model with various types of weathering materials/soils and thickness were simulated, using double-couple point shear dislocation sources to evaluate the significance of ridge-weathering effects on the ground motion characteristics. 2.5D finite difference modeling was adopted for simulating the ground motion using parsimonious staggered grid scheme. The analysis of responses of weathered and non-weathered ridge models reveals that surface waves were generated near the top of the ridge. The surface waves were not dominating on the top of the ridge but at some lower elevation. Results also revealed ground motion amplification with elevation. Maximum amplitude of ground displacement was observed on the top of the ridge, when it was not very much weathered, but the reverse was the case (surface waves were dominating near the base) when weathering velocity was more than three times lesser than the underlying rock. An important conclusion was drawn based on simulated results that the thickness of weathering in terms of wavelength (λ) play a vital role in the generation of very strong surface wave with long duration, i.e. when the thickness is equal to or more than λ/8. The decrease of weathering-velocity further increased the amplitude and duration of surfaces waves. On the other hand, surface waves caused by the ridge itself or by weathered materials having thickness less than λ/12 have amplitudes similar or somewhat more than the incoming waves and with much smaller duration. Therefore, special measure for weathering thickness and its velocity is recommended on the basis of simulated results during the construction of buildings on the ridge topography.