Stable Nitrogen Isotope Ratio and the Anion Concentrations in Cloud-Based Aerosols

Abstract

It is important to determine the stable nitrogen isotope ratio for the nitrogenous substances in aerosols and the geochemistry behaviour of stable nitrate ion isotopes in aerosols in order to elucidate the chemical and physical functions of clouds. Hence, aerosol field sampling was conducted in the skies offshore from Malibu Beach and Santa Barbara, California, U.S.A. on 16 and 18 July 2009, using an airplane. The samples were analyzed for nitrate and nitrite ions using ion chromatography and GC-mass spectrometry (GC-MS). The results indicate a higher stable isotopic ratio of d 15N/14N in the aerosols collected at the cloud top of one cloud than the aerosols collected from the cloud base of a second cloud at the same altitude (30.48 m) on 18 July 2009. NO₂^– nitrite ions were present only in the aerosols sample at the cloud base. At the same altitude, the stable nitrogen isotope ratio in the nitrogenous substances found in the aerosol depended on the aerosol position within the clouds. Furthermore, the altitude effect was small for the isotope ratio. To date, no research has been published that explores the relationship between the electric charge of clouds or the atmosphere and the fate or transformation of aerosols. Present investigation indicated that past models describing the fate or transformation of aerosols within clouds are not based on the actual details of the situation. This study showed that the fates of electrically charged aerosols or ionized aerosols were affected by the electrically charged cloud.