On the use of the field Sunset semi-continuous analyzer to measure equivalent black carbon concentrations

This study describes a method to calculate equivalent black carbon (EBC) concentrations comparable to those obtained from optical filter-based EBC instrumentation from data obtained with a semi-continuous thermo-optical analyzer (Sunset Laboratory Inc., USA) without any need of instrument alterations or extra costs. A correction for the reflection of the Sunset analyzer laser beam by the walls of the sampling tube is introduced. EBCSunset concentrations obtained during two intensive campaigns in Prague (one in winter and one in summer) were compared also to EBC measured by an AE31 Aethalometer (EBCaeth), an AE51 MicroAethalometer (EBCmicro), and a Multi Angle Absorption Photometer (EBCMAAP). Good agreement was observed in both campaigns. The EBCSunset data were also corrected for loading effects in two ways-a simple loading correction and a total correction using data also from the MAAP and a nephelometer. The loading corrections gave similar results for EBCSunset and the aethalometer data except for the simple correction for summer EBCSunset data. The multiple scattering correction factors computed for EBCSunset agreed well with those calculated for EBCaeth. The wall reflection correction for the Sunset analyzer data further improves the agreement between EBCSunset and EBCMAAP.