Uptake of atmospheric pollutants on road asphalt pavements: an underestimated sink in urban environments

The uptake coefficients of nitrogen dioxide (NO 2 ), ozone (O 3 ), formaldehyde (HCHO), and methanol (CH 3 OH) were determined on both weathered (real-world) and non-weathered asphalt pavements. Steady-state uptake coefficients of NO 2 and O 3 were significantly higher on aged asphalt surfaces, with values of 3.5 × 10 −5 and 2 × 10 −4 , respectively, based on geometric surface. To evaluate the impact on urban air quality, zero-dimensional (0-D) model simulations were conducted incorporating heterogeneous loss on asphalt pavements. The simulations revealed that pollutants heterogeneous loss influenced OH and NO 3 radical levels, thereby altering the oxidative capacity of urban atmospheres. Including O 3 reactivity on asphalt surfaces led to a 40% increase in nitric oxide (NO) concentrations, addressing a long-standing discrepancy in air quality models that have struggled to reproduce urban NOx levels for decades. Furthermore, during nighttime, the heterogeneous reactivity of NO 2 and O 3 on asphalt accounted for over 90% of dry deposition. These findings demonstrate the need to account the heterogeneous loss of pollutants on impervious urban surfaces and highlight critical gaps in understanding urban chemical processes, particularly their role in nighttime atmospheric chemistry.