Micro-structural analysis of individual aerosol coarse particles during different seasons at an eastern coastal site in India

Micro-structural analysis of PM samples collected during various seasons (from July-2012 to August-2013) were carried out by Field Emission Scanning electron microscopy (FESEM), Transmission Electron Microscope (TEM) coupled with Energy Dispersive X-Ray Analysis (EDX) and Selected area electron diffraction (SAED) image for in-depth analysis of their morphology, elemental composition and crystal pattern. Significant variation was observed in the particle size and surface morphology during the different seasons of a year. Four different types of particles were commonly observed among which the carbonaceous particles, mainly the soot aggregates were found to be the most abundant species in the PM samples. Few biogenic particles were observed, mostly during post-monsoon period, with distinct microstructure in comparison to other particles. Micro-structural analysis also gives an indication about their post-production history e.g., the age of aerosol particles, turbulence of the air, agglomeration etc. that influences aerosol microstructure. Most of the elements including transition metals were observed to be present in the form of metal oxides from their EDX pattern. Key source of the aerosol particles were from crustal, industrial, biological, and marine or sometimes from long range transport.