# Control of wind speed and contact angle on submicron particulate matter sampling

## TL;DR

This study shows how wind speed and contact angle affect submicron particle sampling accuracy, which is important for air quality monitoring.

## Contribution

The study introduces new models for sampling efficiency based on wind speed and contact angle for submicron particles.

## Key findings

- Wind-induced aerosol losses can reach up to 9% in submicron PM sampling.
- Sampling efficiency has a negative linear relationship with wind speed and a third-order polynomial relationship with contact angle.
- Classic models are inaccurate for submicron aerosols, requiring new predictive approaches.

## Abstract

While particulate matter (PM) instruments are widely used for air quality monitoring and policy development, there is limited research on how wind speed (U0) and contact angle (θ) affect the measurement accuracy of submicron PM, or particles with their diameters ≤ one µm (PM1). This study addresses this gap by employing a wind tunnel experiment with a common sampling system featuring a customized thick-walled cylindrical metal inlet. The results reveal that wind-induced aerosol losses can reach up to 9%, and the sampling efficiency has a negative linear relationship with U0 and a third-order polynomial relationship with cos(θ). This model demonstrates a significant discrepancy with classic models in predicting sampling efficiency, which indicates the inapplicability of classic sampling efficiency models to submicron aerosols. The findings of this study can help correct wind-induced errors, improve sampling protocols, and develop new predictive models, which have implications for improving hazardous air quality warning systems and safeguarding public well-being.