Development,verification and application of a versatile aerosol calibration system for online aerosol instruments

Traditional calibration methods mostly focus on the calibration of detection systems while the calibration from the sampling and pre-condition systems to the detection system is usually ignored.In this regard,a Primary Standard Aerosol Mass Concentration Calibration System(PAMAS)is developed for the whole-process calibration of time-resolved aerosol measurement instruments.PAMAS is composed of a particle generation chamber,an ultrasonic atomizer,a dilution system,and a syringe pump.It is designed to steadily generate standard aerosol particles of known concentrations(≤250μg/m^(3)),chemical compositions,and stable particle size distributions.Monodispersed aerosol can be generated in the size range of hundreds of nanometers to several micrometers with a narrow size distribution.The generated particles with different compositions generated by PAMAS have been well verified by the filter-based gravimetric method,yielding accuracy and R^(2) of more than 95%and 0.999 in a wide concentration range.The response time by changing the target concentration of reference particles is 1-2 min.PAMAS has been applied to various types of time-resolved aerosol measurement instruments,including particle mass concentration monitors(Beta Attenuation and Tapered Element Oscillating Microbalance),online Ion Chromatograph,and semi-continuous OCEC carbon aerosol analyzer.Very consistent results between PAMAS and calibrated instruments can be obtained if the instruments are functioning well.As for instruments with certain technical issues,PAMAS can serve as a good tool for performance evaluation and quality assurance of the instruments and the accuracy of the measurement data can be adjusted based on the calibration results.