Is There a Relationship between Lake Urmia Saline Lakebed Emissions and Wet Deposition Composition in the Caucasus Region?

Abstract

One of the most significant environmental catastrophes throughout the Middle East and Caucasus region has been the desiccation of Lake Urmia, the world second-largest hypersaline lake. This lake has lost approximately two-thirds of its water volume since 1999, resulting in increased exposure of lacustrine deposits that are considered as a new aerosol source. This in situ study investigates for the first time the spatial distribution of water-soluble ion concentrations (Cl–, Br–, NO2 –, NO3 –, SO4 2–, methanesulfonate (MSA), pyruvate, oxalate, adipate, Na+, K+, Ca2+, Mg2+, and NH4 +) in wet deposition samples collected around the Lake Urmia region to characterize relationships between rainwater composition and location relative to the lake. Rainwater collection was performed for 21 rain events from September 2017 to September 2018 across 13 sampling stations, providing representative coverage of the region surrounding Lake Urmia. The most dominant ions are as follows: Ca2+ > Cl– > SO4 2– > Na+ > NO3 –. Organic acids and MSA contribute negligibly to the total ion concentrations. Principal component analysis (PCA) and correlation coefficient (CC) analyses show that the majority of ions throughout the region are associated with salt and crustal particles comprised of Cl–, Br–, SO4 2–, Na+, Ca2+, and Mg2+, with the minority of ions (e.g., NH4 + and NO3 –) stemming from anthropogenic emissions. Concentrations of salt and crustal tracer species (i.e., Na+, Cl–, Br–, Mg2+, and SO4 2–) were inversely related to the distance from the Lake Urmia shoreline, suggestive of potential subcloud scavenging (washout) of freshly emitted aerosols. Backward trajectory analysis (HYSPLIT) shows that most of the rain events were linked to air masses originating in areas far upwind of Lake Urmia. Results of this study emphasize that wet deposition data provide support for effective scavenging of salt and crustal emissions as a function of distance from a desiccated lakebed.

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

“…Earlier works by Ahmady‐Birgani et al. (2020, 2021) and Ravan et al. (2019) reported elevated values of these elements and species in nearby locations to Lake Urmia (i.e., Golmankhaneh, Salmas, and Ashk Island).…”

“…In sum, unlike the winter season that contains the lowest values of marine components, the highest concentration of these ions appears in March, April, May, and June (i.e., in the late winter to spring months). Earlier works by Ahmady-Birgani et al (2020, 2021 and Ravan et al (2019) reported elevated values of these elements and species in nearby locations to Lake Urmia (i.e., Golmankhaneh, Salmas, and Ashk Island). Meaning, rainwater samples have been affecting by marine elements and ions near 40km farthest from the Lake's shoreline.…”

“…The rainwater samples were collected in HDPE containers, and approximately 250 ml of rainwater equivalent to 8 mm precipitation was stored. Care was taken to collect the samples once the rain initiated to rain, as the concentration of aerosols and pollutants are in the highest quantity (Ahmady‐Birgani et al., 2020, 2021; Khan & Sarwar, 2014). Before sampling, the containers were rinsed with ultra‐pure water and positioned out away from buildings, animals, and all pollutant sources at the height of 1 m. Also, the containers were mounted out precisely at the beginning of rain events to avoid any possible contamination of dry deposition.…”

“…& Khalesifard., 2020; Quick & Chadwick., 2011). So, as a critical challenge, the nature and concentration of Lake Urmia emissions for dwellers and adjacent lands are still vague (Abuduwaili et al, 2010;Aghakouchak et al, 2015;Ahmady-Birgani et al, 2021. Therefore, the role of the Lake Urmia basin as the source of dust emission in its nearby regions is unknown.…”

“…So it is inferred that shoreline recession of saline lakes and subsequently emitting salt‐bearing particles will create saline dust storms which might be transported for thousands of kilometers (Ghomashi & Khalesifard., 2020; Quick & Chadwick., 2011). So, as a critical challenge, the nature and concentration of Lake Urmia emissions for dwellers and adjacent lands are still vague (Abuduwaili et al., 2010; Aghakouchak et al., 2015; Ahmady‐Birgani et al., 2021, 2020). Therefore, the role of the Lake Urmia basin as the source of dust emission in its nearby regions is unknown.…”