Temporal Distribution and Chemical Characterization of Atmospheric Fine Particulate Matter in a Coastal City

Aerosol particles with an aerodynamic diameter of less than 2.5 μm (PM_2.5) can deeply enter into human respiratory system, which is a common cause of air pollution in India. Water-soluble inorganic ions (WSII) found in PM_2.5 have the property of absorbing and condensing water and leads to new particle formation. These ions also indirectly affect ecosystems and environmental materials through deposition hence research on these ions can elucidate on their primary sources and methods of formation. In the present study, the characteristics of water-soluble inorganic ions in fine particulate matter at Calicut, a city on the Malabar Coast in the state of Kerala, India, are presented. Ambient PM_2.5 concentrations were monitored and further the particles were chemically characterized for its water-soluble ions. It is found that the PM_2.5 concentrations exceeded the National Air Quality Standard by about 10% of the time and the maximum value of PM_2.5 was found to be 98 μg/m³. Chemical analysis of the collected samples indicated that 39% of PM_2.5 mass is accounting for water-soluble inorganic ions. Among the total WSIIs in ambient PM_2.5, SO₄^2– (25.8%) was the predominant component, followed by Na⁺ (13.6%) Cl⁻ (13.4%), and K⁺ (13.1%). Presence of Cl⁻ and Na⁺ in particles indicated that it is sea salts origin. These findings imply that inorganic aerosol pollution is very significant in coastal cities.