Comparison of size distribution and electrical particle sensor measurement methods for particle lung deposited surface area (LDSA^al) in ambient measurements with varying conditions

Abstract

Abstract. During recent years it has become evident that additional metrics along the particle mass concentration together with dense air quality monitoring networks within cities are needed to understand the most efficient ways to tackle the health burden of particulate pollution. Particle lung deposited surface area (LDSAal) is a metric to estimate particle exposure in the lung alveoli, and it has gained interest as a parameter for air quality monitoring as it is relatively easy and cost-efficient to measure with electrical particle sensors. Also, various studies have indicated its potential as a health-relevant metric. In addition to the electrical particle sensors, LDSAal can be measured with various size distribution methods. However, different LDSAal measurement methods have fundamental differences in their operation principles e.g., related to the measurement size ranges, size-classification or conversion from the originally measured quantity into LDSAal. It is not well understood how these differences affect the accuracy of the measurement in ambient conditions where especially the particle effective density and hygroscopicity can considerably change the particle lung deposition efficiencies. In this study, the electrical particle sensor measurement (Partector) and two size distribution approaches (ELPI+, DMPS/SMPS) were compared in road traffic environments with different environmental conditions in Helsinki and Prague. The results were compared by utilising general assumptions of LDSAal measurement (spherical hydrophobic particles with the standard density) and by evaluating the effects of the particle effective density and hygroscopicity. Additionally, the Partector and ELPI+ were compared in various urban environments near road traffic, airport, river traffic and residential wood combustion. The results show that comparison of different LDSAal measurement methods can be complicated in ambient measurements. The challenges were especially related to the estimated lung deposition of accumulation mode particles roughly larger than 200–400 nm. On the other hand, the results suggest that the differences between the methods are reasonably low when considering only ultrafine and soot particles, highlighting the suitability of LDSAal as a monitored metric when estimating spatial differences in the particulate pollution within cities.