A low-cost monitor for measurement of fine particulate matter and aerosol optical depth. Part 1: Specifications and testing

Abstract. Globally, fine particulate matter (PM 2.5 ) air pollution is a leading contributor to death, disease, and environmental degradation. Satellite-based measurements of aerosol optical depth(AOD) are used to estimate PM 2.5 concentrations across the world, but the relationship between satellite-estimated AOD and ground-level PM 2.5 is uncertain. Sun photometersmeasure AOD from the Earth's surface and are often used to improve satellite data; however, reference-grade photometersand PM 2.5 monitors are expensive and rarely co-located. This work presents the development and validation of the Aerosol Mass and Optical Depth(AMOD) sampler, an inexpensive and compact device that simultaneously measures PM 2.5 mass and AOD and was designed specifically to be used in citizen sciencecampaigns. The AMOD utilizes a low-cost light-scattering sensor in combination with a gravimetric filter measurement to quantify ground-level PM 2.5 . Aerosol optical depthis measured using optically filteredphotodiodes at four discrete wavelengths. Field validation studies revealed agreement within 10 % for AOD values measured between co-locatedAMOD and AErosol RObotics NETwork ( AERONET) monitors and for PM 2.5 mass measured between co-locatedAMOD and EPA Federal Equivalent Method (FEM) monitors. These results demonstrate that the AMOD can quantify AOD and PM 2.5 accurately at a fraction of the cost of existing reference monitors.