Surface Distribution of Sulfites and Sulfates on Natural Volcanic and Desert Dusts: Impact of Humidity and Chemical Composition

In this work, we investigated the amount of sulfites and sulfates formed on the surface of volcanic and desert dusts under atmospheric conditions of 298 K, 760 Torr, and different relative humidity (RH) values ranging from 0 to 83%. Controlled processing of volcanic and desert dusts with SO2 was achieved in a custom-made atmospheric pressure reactor, and surface sulfites and sulfates were analyzed using a recently developed HPLC method. The kinetics of formation and loss of sulfur species formed on the surface of five Icelandic volcanic dusts and three desert dusts was investigated. Our results evidence that surface composition influences the amount of sulfites and sulfates formed on the surface under low humidity conditions (RH below 30%). Higher amounts of sulfites are positively correlated with the (Fe + Ti)/Si parameter, while higher amounts of sulfates are positively correlated to the amount of Na on the surface of dust. However, the dominant role in both formation and distribution of sulfites and sulfates on the surface is attributed to water, as it increases the rate of transformation of sulfites into sulfates.

Automated summary

This study investigated the formation of sulfites and sulfates on the surface of volcanic and desert dusts under atmospheric conditions. It was found that surface composition and water play important roles in the formation process.