Nitrate depletion via HnO₃ release from mixed dicarboxylic acid - salt aerosol

Atmospheric aerosols are complex mixtures of organic and inorganic compounds and their reaction products. Nitrates, sulphates, low molecular weight dicarboxylic acids are commonly found in aged aerosols. As the aerosol dries, high solute concentrations and ionic strength, significantly higher than the bulk solution, are attained, thus enabling rare chemistry. Here we have studied reactions involved during the hygroscopic growth cycle of homogeneously mixed sodium nitrate (SN) and malonic acid (MA) aerosols of sizes 40-50 micron at 85% relative humidity (RH) using micro-Raman spectroscopy. Mixed aerosols (1:1) were spray-deposited onto Ag substrate placed inside a RH controlled gas flow observation cell. Growth cycle was studied by first drying till 5% RH followed by humidification upto 83%. In-situ Raman spectra of individual particles were recorded from 100-2000cm^-1 and 2700-4000 cm^-1