Razyeh Lak - Research Institute for Earth Sciences, Geological Survey of Iran
Najmeh Davari - Mineral Exploration Department, Geological Survey of Iran
Ali Mohammadi - Research Institute for Earth Sciences, Geological Survey of Iran

This project was carried out aiming at comparing the geochemical changes of the Urmia Lake brine during drought and wet periods. By 2010, the Urmia Lake brine was from Na-Mg-Cl type that is comparable to the Great Salt Lake of Utah (USA). This trend has dramatically changed due to drying up of Lake Urmia and increasing lake evaporation by tens of times, as well as decreasing surface water inputs in recent years. As the evaporation intensifies, magnesium to sodium ratio increases in brines and eventually the brine type changed to Mg-Na-Cl in 2012. Evolution trend of Urmia Lake brine doesn‟t follow Eugster & Hardie diagram since 2010 and some changes seems necessary to show the situation of Lake Urmia s brine.In this study, the brine type was investigated during drought and wet season in 2019. It should be noted that the density of sampling network was unique in March 2019 and sampling with this density has not been carried out in Lake Urmia yet.In order to study the hydrochemistry of Lake Urmia and to determine the brine type, some samples were taken from lake water. Then the results were compared and interpreted. In January 2019, sampling was carried out in the lake up to 30cm depth and 37 brine samples were taken. However, due to the drought, driving boat to the middle parts of the lake was not possible. In March 2010, 75 and 71 samples were taken from surface and deep brines respectively in north of the lake making use of a motor boat in a regular network with 5 km spaces. Density and depth were recorded on site and major cations and anions were analyzed in the laboratory of Khour Potash Complex. Analysis results indicated that the dominant brine type is Mg-Na-Cl in January 2019. However, the brine type is Na-Mg-Cl in March 2019 at both shallow and deep samples that is indicative of improving ecological conditions, increasing sodium to magnesium ratio and occurring conditions similar to 2007 because of salt solution. Today, potassium is economically exploited from the playas in Australia and USA with similar ratio as SOP (K2SO4) that this condition is more valuable in Lake Urmia due to easy access to the surface potassium-rich brines.