Abstract for presentation at 14th IUAPPA World Congress

The measurement of the scattering properties of aerosols is limited by the errors introduced by typical single wavelength Integrating Nephelometers. These limitations however, can be reduced by implementing the features of the Ecotech Three Wavelength Integrating Nephelometer. These limitations are predominantly contributed by, Particle Size, Relative Humidity, Lambertian Distribution of the light source, Truncation Error and the Wavelength of the Nephelometer. Fitting a PM_2.5 size selective inlet and controlling the Relative Humidity of the sample reduces the effects larger particle sizes, and of moisture. The errors introduced by a non-Lambertian light source can be reduced by calibrating the light source distribution. This feature is unique to the Ecotech design. The truncation errors introduced by the physical constraints of the Nephelometer’s measurement cell can also be corrected by measuring the sample at three distinct wavelengths (450nm, 520nm & 700nm). The Ecotech Three Wavelength Nephelometer also has the added advantage of a compact Three wavelength light source which eliminated the need for complex optics and multiple Photo Multiplier Tubes, making the instrument more portable and robust. Theoretical studies have shown that the use of a size selective inlet can improve the uncertainty of the scattering measurement by an order of up 30% at a particle size of <1um. Further studies have shown that by correcting the truncation errors by measuring at different wavelengths can reduce this error a further 10%. These conclusions highlight that the Ecotech Three Wavelength Nephelometer can be used for very precise measurements of aerosol properties in varying conditions.