From input to transformation: Investigating the dynamic evolution of volatile organic compounds and driving mechanisms during sandstorms

Sandstorms are frequent natural phenomena in arid and semi-arid regions, with significant impacts on air quality and ecological systems. Volatile organic compounds (VOCs) demonstrate high photochemical reactivity and a strong tendency to form secondary pollutants during sandstorm events. However, the mechanisms governing their interactions with dust particles remain poorly understood. This study was conducted using synchronous observations at the Yinchuan Urban Ecosystem Positioning Station in Ningxia, where data on meteorological parameters, atmospheric pollutants, and VOCs were collected across different dust storm stages. By integrating Positive Matrix Factorization and Structural Equation Model, we systematically examined the dynamic evolution of VOCs, pollution sources, and their driving mechanisms during dust storm events. Results showed that during sandstorm period, the total VOCs concentration declined from 36.14 × 10⁻⁹ (pre-sandstorm period) to 20.76 × 10⁻⁹, then gradually increased to 23.58 × 10⁻⁹ (post-sandstorm period). The primary contributors to VOCs included alkanes and oxygenated VOCs. Sandstorm inputs altered the VOCs component ratios, with the most pronounced reduction observed in low-reactivity alkanes. In the pre-sandstorm period, VOCs primarily originated from industrial activities and motor vehicle emissions, contributing 28 % and 23 %, respectively. During the sandstorm and post-sandstorm period, solvent sources and motor vehicle emissions emerged as the primary sources of VOCs. Meteorological factors, such as wind speed, primarily exerted a dilution effect on VOCs, whereas temperature and humidity promoted VOCs generation in the post-sandstorm period. During the sandstorm period, dust particles mainly diluted VOCs concentrations, whereas in the post-sandstorm period, they contributed to increased VOCs levels by facilitating secondary pollutant formation. This study enhances the theoretical understanding of compound pollution formation during sandstorm events and provides scientific guidance for regional pollution control strategies.