International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 04 Issue: 09 | Sep -2017 www.irjet.net p-ISSN: 2395-0072 © 2017, IRJET | Impact Factor value: 5.181 | ISO 9001:2008 Certified Journal | Page 1274 Analysis of Effective Hygroscopic Growths, Kelvin Effects and Water Activities of Maritime Aerosols Using Volume Mix Ratio Muhammad Dahiru Audu 1 , Abdulrazak Tijjani 2 Ruhullahi Muhammad 3 1 Physics Department, Federal College of Education (Tech), Potiskum, Nigeria 2 College of Art and Sciences Kano, Kano State, Nigeria 3 Department of Physics with Electronics, Federal University Birnin Kebbi, Kebbi, Nigeria ---------------------------------------------------------------------***--------------------------------------------------------------------- Abstract - In this paper the effective hygroscopic growths of atmospheric aerosols and effective radii using microphysical properties of atmospheric aerosols are extracted from Optical Properties of Aerosols and Cloud (OPAC) at seven relative humidity (50%,70%,80%,90%,95%,98% and 99%).The microphysical properties extracted were radii of the individual aerosols and the volume mix ratios as functions of relative humidity (RH). The effective hygroscopic growths and effective radii were parameterized and the modified Kholer equation was used to determine water activities, kelvin effects and humidification factors. It was observed that the data fitted the models very well. The results shows that the growth factor and effective radii increases with increase in RH and are more pronounced at 90-99% RHs, the water activities is more dominant than the kelvin effect in all types of models. Key Words: Hygroscopic growths, Relative humidity, Kelvin Effect, Humidification factor, Water activity. 1. INTRODUCTION Aerosols in the atmosphere comprised of numerous and diverse components originating from both natural and anthropogenic activities. The interactions between aerosols and water vapor play a vital role in determining their effect on the environment. The chemical and physical characteristics of aerosols are diverse and attempting to comprehend such variability within hygroscopic model is complex. Aerosol may exist in a solid or liquid form or combination of two over a wide range of ambient conditions in both sub and super saturated humid environment [1]. Chemical compositions of aerosol particles released from natural and anthropogenic sources are not homogeneous either locally or globally, hence characteristics such as hygroscopicity, Kelvin effect and water activity are significantly different from one particle to another, controlling the particle’s ability to form cloud droplets and affect particles size [2]. The size dependence, which is due to the surface tension of the solution–air interface, is known as the Kelvin effect [3] is of central importance to cloud drop activation, and as the equilibrium radius is a key property of an atmospheric aerosol particle, affecting its light-scattering behavior, dry deposition, and Kelvin effect can also play an important role in other atmospheric processes [4]. The composition of a solution determines its water activity (aw) and surface tension (σs) [4]. The equation that is often used to describe both hygroscopic growth of aerosol particles and their activation to cloud droplets is the Kohler equation. This equation is divided into two as: (1) the Kelvin effect; this is responsible for the increase in equilibrium water vapor pressure over a curved surface, and is directly proportional to the effective surface tension as a result of the solution –air interface. For an aqueous solution drop with given concentration, the equilibrium fractional relative humidity increases with decreasing drop radius; and (2) the Raoult effect; this is the reduction in water activity associated with solute dissolution in terms of either effective hygroscopic growth and/or the effective radius of the mixtures at given RHs [3]. Almost every property of atmospheric aerosols is a strong function of Relative Humidity [5]. The main parameter used to characterize the hygroscopicity of the aerosol particles is the aerosol hygroscopic growth factor gf (RH), which is defined as the ratio of the particle diameter at any RH to the particle diameter at RH = 0 % [6]. Studies performed by [7] considered volume, mass and number base ratios, and it was observed that the hygroscopic growths factors increases exponentially with relative humidity at various aerosols types such as Antarctic, arctic, continental, desert, maritime and urban and also found almost all aerosols deliquesces behavior at 99% relative humidity. The urban environment is mostly affected by transportation and heavy industry emissions. For atmospheric aerosols, the range of κ typically varies from as low as ∼0.01 for some combustion aerosol particles up to ∼1 for sea-salt particles [8].