Investigating the temporal and spatial variation of dust and their relation to hydro-climatic and land cover factors in the salt lake basin in Iran

Abstract

Abstract The Salt Lake Basin is one of the largest and most important basins in central Iran, and in recent decades, numerous climatic and human factors have led to significant changes in its environmental condition. In this study, an attempt is made to determine the process of physical changes of the Salt Lake in a period of 20 years with the help of remote sensing technology and geographical information system, the important factors affecting the drying of the lake, the process of changes on the surface area of the lake and surrounding land use. The effects of these changes on internal dust source should also be studied. To this end, the process of changes in the Salt Lake was first studied using MODIS Terra/Aqua satellite images, and then the factors affecting the changes in the Salt Lake surface, including incoming surface water flow, precipitation, temperature, and sea level pressure as the main hydro-climatic parameters were discussed. According to the changes of the above parameters, the studies were divided into two decades: 2000–2010 and 2010–2020. The results show a significant correlation between the lake surface area and the water flow into the lake from the Qomroud river side. Due to the decrease of inflows to the lake and the increase of temperature and atmospheric pressure around the Salt Lake, we found a strong decrease of the lake surface area in recent years. Changes in land cover in the Basin show that bare and barren land has increased over time. The area used for agriculture has also decreased over the past decade. To determine the role of lake bed drying in dust generation and the areas affected by dust, the temporal and spatial monitoring of dust concentration, the detection of dust storms and their occurrence were performed using the Aerosol optical depth (AOD) Index and the Sentinel-5 and MODIS Aqua/Terra satellite images. The study of the satellite images showed that in the Salt Lake Basin, the bed of the dried lakes of the Hovz-Sultan and the Qom Salt Lake, as well as the Qomrud River pathway in the desert plain of Masileh (between the Hovz-Soltan Lake and the Salt Lake) are the most critical areas in the basin in terms of dust generation and occurrence, so the highest dust concentrations occurred in these areas in the basin. In the second decade (2010–2020), an increase in the AOD index is observed throughout the basin, especially in the area around the Salt Lake to the Sultan Basin. Despite the decrease in the number of dust events in the second decade, we also observed a much greater dispersion of dust in this decade than in the previous decade. Areas of high dust concentration in the basin originated from the central desert basin, and the salt lake itself has acted as a source of dust production and is additionally influenced by currents from the adjacent basin. In general, climatic and human changes, including cover change, have evolved in a direction that has led to the enhancement and formation of new dust centers. These changes, in turn, have also affected the ecosystem of the lake, which requires comprehensive management of this ecological system to bring the situation under control.