Seasonal ambient air particulates and metallic elements (Cr, Cu, Zn, Cd, Pb) pollutants dry depositions fluxes predictions and distributions with appropriate models at a farmland site

Abstract

This study compare dry deposition models to identify the best one for predicting the deposition of ambient metallic elements (Cr, Cu, Zn, Cd, Pb) at a characteristic farmland sampling site from Aug. 2013 to Jun. 2014.In this study, the collection models of Baklanov and Sorensen, Zhang, and Wood, as well as the vegetation collection model, are used to calculate the dry depositions velocities of 2.5, 10, 20, and 23 μm. These values were used to calculate the seasonal dry deposition fluxes of ambient air particulates and metallic elements.The results thus obtained indicate that the specified collection models are all suitable for predicting the dry depositions of large (10, 20 and 23 μm) ambient air particles and metallic elements (Cr, Cu, Zn, Cd and Pb). All of the models yielded better predictions of dry depositions velocities for particles of size 20 and 23 μm in winter than in other seasons than particles of other sizes.The Baklanov and Sorensen, Zhang, Wood and vegetation collection models all predict the least dry deposition of ambient air particles of size at 2.5 μm and all metallic elements. Moreover, this study further revealed that the particle size is the key parameter that influence the modelled dry depositions fluxes and resulted in the calculated/measured fluxes variations ratios for ambient air particles and metallic elements. Another influence parameter is the pollutants (particles, metallic elements) concentrations. When the particle size is fixed, the higher of the pollutants concentrations, the higher the calculated/measured fluxes ratios can be obtained at this farmland sampling site.