Particle-particle chemistry between micrometer-sized PbSO4 and CaCO3 particles in turbulent flow initiated by liquid water.

A mixture of natural and anthropogenic particles is ubiquitous in the troposphere and exerts an important influence on air quality. This work reports the study of mixing and heterogeneous chemistry of particles of natural-like mineral dust (CaCO(3)) and anthropogenic-like microparticle (PbSO(4)) in turbulent air flow under varying relative humidity. Sparse monolayers of laboratory-generated particles were collected on substrates using impaction. The grain size distribution and chemistry of micrometer-sized particles were determined as CaCO(3)-PbSO(4) internal and external mixtures by Raman imaging, scanning electron microscopy, and time-of-flight static secondary ionization mass spectrometry. The condensation of a thin water layer on mixed aggregates initiates the formation of complex internal mixtures of Pb(3)(CO(3))(2)(OH)(2), PbCO(3), CaSO(4)·2H(2)O, CaCO(3), and PbSO(4) fine particles. These heterogeneous chemistry processes which may occur in ambient air can increase dramatically the amounts of hazardous breathable particles.