Ice Nucleation Abilities of Mexican Agricultural Soils

Abstract:

Ice nucleating particles (INPs) are responsible for primary ice particle formation in the atmosphere, and therefore, they can influence precipitation formation and the hydrological cycle. Efficient at nucleating ice particles include mineral dust, bioparticles, and organic particles. Although recent studies have suggested that aerosol particles from agricultural soils have the potential to act as INPs, Mexican agricultural soils have not been studied yet. In this study the ice nucleating abilities of aerosol particles from agricultural soils from the Zacatecas State, Morelos State, and Mexico City are evaluated. Aerosol and soil samples were collected during soil tillage to determine the concentration of INPs as a function of temperature and particle size. Aerosol particles were generated from the soil samples through dry and wet aerosol generation systems. The aerosol generated in the laboratory, together with the aerosol samples collected in the field, were analyzed using the UNAM - Microorifice uniform deposit impactor - Droplet freezing technique (UNAM-MOUDI-DFT). The chemical and mineralogical composition of the samples was assessed by x-ray fluorescence and x-ray diffraction. Finally, soil samples were cultured in different growing media to verify the presence of bacteria and fungal propagules. The mineral and organic components present in the Mexican agricultural soils were found to influence ice crystals’ formation with INPs concentrations ranging between 10^-1 and 10² L^-1. The present results are consistent with the literature for agricultural soils from Wyoming, in terms of the freezing temperatures. Higher concentrations of INPs were found in this study compared to agricultural soils from Colorado, Kansas, and Wyoming. Correlations between the concentrations of INPs and microorganisms will be computed, in addition to correlations between the INPs onset freezing temperatures with the aerosol composition and meteorological variables.