Wet Scavenging in Removing Chemical Compositions and Aerosols: A Case Study Over the Lake Urmia

Lake Urmia, NW Iran, and S Caucasus region, has lost approximately three-fourth of its water volume resulting in increased exposure of lacustrine deposits. Therefore, the role of Lake Urmia desiccated saline lands on local aerosols and rainwater compositions is still vague. This study investigates the temporal and seasonal patterns of rainwater chemistry from January 2018 to June 2018 (six months) in 13 stations throughout the Lake Urmia basin. The samples collected were analyzed using triple quadrupole inductively coupled plasma mass spectrometry (ICP-QQQ) and ion chromatography (IC) to measure elemental and ionic concentrations. Then, the Hybrid Single-Particle Lagrangian Integrated Trajectory model (HYSPLIT) was applied to identify the pathway and contribution of emissions. The results depict that the concentration of elemental and ionic components over different parts of the Lake Urmia basin are significantly different. West and north directions have the highest concentrations of marine ions associated with fewer toxic elements. In contrast, the east and south directions show a high concentration of heavy metal elements and ions. The high level of heavy and toxic elements at the east and south directions indicates that local anthropogenic sources are more influential. The seasonal and monthly variabilities of chemical compositions depict that the highest concentration of Na+, Mg2+, Ca2+, K+, Cl-, Br-, NO3-, Al, Cr, Mn, Fe, and Co were in the spring season and SO42-, NH4+ and NO2- were highest in winter. Seasonal variation for MSA, organic acids (i.e., Pyruvate, Adipate, and Oxalate), Ni, Cu, Zn, V, and Ti were not apparent. Cluster-mean HYSPLIT backward trajectories results show the most dominant air mass sectors are from W (a: Iraq, Syria, and Arabian deserts; b: Mediterranean Sea; and c: KSA) and NE (the Caspian Sea and its vicinity), contributed to almost 65% and 22%, respectively. These air masses bring a significant quantity of crustal and marine aerosols, respectively. It is inferred that the Lake Urmia dried-up lakebeds have less impact on the contribution of emissions across the region.

Automated summary

This study investigates the temporal and seasonal patterns of rainwater chemistry in the Lake Urmia basin and identifies the pathways and contributions of emissions using the HYSPLIT model. The results show significant differences in elemental and ionic concentrations across different parts of the basin, indicating the influence of local anthropogenic sources on heavy metal and toxic element concentrations. Seasonal and monthly variations reveal peak concentrations of different elements and ions in different seasons. The HYSPLIT model results indicate that the dominant air masses in the region come from Iraq, Syria, the Arabian deserts, the Mediterranean Sea, and the Caspian Sea, bringing substantial amounts of crustal and marine aerosols.