AS&T Article Highlight
AS&T Article Highlight
By Kerry E. Kelly
“Long-term sensor measurements of lung deposited surface area of particulate matter emitted from local vehicular and residential wood combustion sources”
Joel Kuula, Heino Kuuluvainen, Jarkko V. Niemi, Erkka Saukko, Harri Portin, Anu Kousa, Minna Aurela, Topi Rönkkö, and Hilkka Timonen (2019), Aerosol Science and Technology
Most studies that seek to understand the health effects of particulate matter (PM) focus on PM mass concentration or size-fractionated PM concentration. A number of studies support the value of additional measurements, such as particle composition, particle number, and surface area, to assist with understanding how particle properties affect human health. However, these measurements tend to be expensive, particularly for ultrafine particles that make small contributions to particle mass concentration but are large contributors to particle number and surface area. Ultrafine particles, such as those from combustion sources, are generally too small to be effectively detected by optical methods, common in low-cost particulate matter sensors. The expense of measuring particle size and surface area limits the amount of data that can be collected. Kuula and co-authors evaluated a mid-priced diffusion charger to estimate lung-deposited surface area (LDSA) in four different regions of an urban area (Helsinki, Finland) that are affected by vehicle emissions and residential wood combustion. This appears to be the first long-term deployment of diffusion chargers in a sensor network.
They compared the LDSA estimated from a diffusion charger over a 12-month period with that estimated from a differential mobility particle size (DMPS). As illustrated in Figure 2 of the article, the LDSA from the diffusion charger correlated well with the DMPS, and the slope of the linear relationship varied slightly by season from 1.10 (March) to 0.86 (October), which was likely associated with seasonal differences in the particle size distribution. The LDSA measurements were also highly correlated with black carbon measurements, which highlights the usefulness of diffusion chargers for measuring combustion-generated particles. Over the course of the study, the diffusion charger measurements did not exhibit significant drift, and the LDSAs in the four different locations exhibited differences. For example, the LDSAs in an urban street canyon were more than double that of the urban background site. In addition, residential wood combustion caused LDSA peaks in the evening.
This study highlights the potential utility of a sensor network that includes diffusion chargers to estimate LDSA. This type of information could prove valuable for understanding the links between particle properties and health effects and future policies related to PM standards and emission controls.