Mass concentration determination of particles smaller than 2.5 microns in air

A system for real-time determination of airborne particulate matter concentration, the system comprising:

• a sharp cut cyclone configured to receive ambient air and to separate airborne particulate matter at or below a predetermined size threshold;
• a volumetric flow control assembly comprising a flow sensor, an internal pump, a pressure sensor, and a temperature probe affixed to an inlet of the sharp cut cyclone, the volumetric flow control assembly configured to control a flow rate of the ambient air through the sharp cut cyclone;
• a multi-wavelength integrating nephelometer in fluid communication with the sharp cut cyclone, the multi-wavelength integrating nephelometer configured to simultaneously measure a first scattering coefficient of airborne particles in the ambient air at a first optical wavelength and a second scattering coefficient of airborne particles in the ambient air at a second optical wavelength;
• a humidity and temperature sensor configured to measure relative humidity and temperature of an air sample within or adjacent to a measurement cell of the multi-wavelength integrating nephelometer;
• a sample conditioning system configured to maintain relative humidity of the air sample below a predetermined threshold;
• and
• a processor configured to:
• (i) determine a scattering Ångström exponent (SAE) using at least the first scattering coefficient and the second scattering coefficient,
• (ii) determine a dewpoint correction factor based at least on the measured relative humidity and temperature, and
• (iii) determine an airborne particle concentration for a range of particle sizes based at least on the SAE, the first scattering coefficient used outside of the determination of the SAE, and the dewpoint correction factor.