Size-segregated aerosol mass closure and chemical composition in Monte Cimone (I) during MINATROC

摘要

Physical and chemical characterizations of the atmospheric aerosol werecarried out at Mt. Cimone (Italy) during the 4 June-4 July 2000 period.Particle size distributions in the size range 6nm-10µm were measuredwith a differential mobility analyzer (DMA) and an optical particle counter(OPC). Size-segregated aerosol was sampled using a 6-stage low pressureimpactor. Aerosol samples were submitted to gravimetric and chemicalanalyses. Ionic, carbonaceous and refractory components of the aerosol werequantified. We compared the sub- and superµm aerosol massconcentrations determined by gravimetric measurements (m_GM), chemicalanalyses (mm_CA), and by converting particle size distribution to aerosolmass concentrations (mm_SD). Mean random uncertainties associated withthe determination of mm_GM, mm_CA, and mm_SD were assessed. Thethree estimates of the sub-µm aerosol mass concentration agreed, whichshows that within experimental uncertainty, the sub-µm aerosol wascomposed of the quantified components. The three estimates of the super-µmaerosol mass concentration did not agree, which indicates that randomuncertainties and/or possible systematic errors in aerosol sampling, sizingor analyses were not adequately accounted for. Aerosol chemical compositionin air masses from different origins showed differences, which weresignificant in regard to experimental uncertainties. During the Saharan dustadvection period, coarse dust and fine anthropogenic particles wereexternally mixed. No anthropogenic sulfate could be found in the super-µmdust particles. In contrast, nitrate was shifted towards the aerosolsuper-µm fraction in presence of desert dust.