The Urmia playa as a source of airborne dust and ice-nucleating particles – Part 2: Unraveling the relationship between soil dust composition and ice nucleation activity

Abstract. Ice-nucleating particles (INPs) originating from deserts, semi-arid regions, and dried lakebeds may cause heterogeneous ice nucleation, impacting cloud properties. Recently, due to climate change water scarcity, abandoned agricultural lands with little surficial crust negligible vegetation cover have become an increasing source of atmospheric dust worldwide. Unlike these areas are rich in soluble salt (bio-)organic compounds. Using soil samples various sites the Lake Urmia playa (LUP) northwestern Iran airborne dusts collected at nearby meteorological stations, we elucidate how minerals, salts, organic matter interact determine IN activity saline soils dust. X-ray powder diffraction shows that mineralogical composition is dominated by K-feldspars (microcline), quartz, carbonates, clay minerals. The were stripped stepwise matter, salts. After each removal step, nucleation (IN) was quantified terms onset freezing temperatures (Thet) heterogeneously frozen fractions (Fhet) emulsion experiments using differential scanning calorimetry (DSC). We examined influence salts pH on microcline quartz experiments, comparing reference suspensions exposed concentrations levels characteristic LUP samples. These analyses, combined correlations between Thet Fhet, allow us identify components contribute or inhibit activity. turn out be very good INPs, around 248 K immersion experiments. Interestingly, their proves relatively small share (1 %–5.3 %). removal, remaining (Thet≈244 K) can traced back fraction, because Fhet correlate positively mineral content but negatively microcline. attribute inability act as INPs basic well presence additionally removing increased again significantly (Thet≈249 K), negative correlation turned into a slightly positive one. Removing carbonates natural leads increase well, indicating also suppresses INPs. Overall, this study demonstrates do not just add up yield behavior governed inhibiting promoting interactions components.