From September to October 2011, the inland lakes, rivers and mountains of the Pamir Plateau in western Tajikistan, the Amu Darya River and its tributaries in the southwest, the northern plain area, and the eastern plains and mountains were inspected and collected on the surface layer (top 1 cm) soil, river bottom sand, lake sediments or bedrock. See Figure 1 for the locations of the sampling points:

Figure 1: Sampling point location diagram

In June 2012, an inspection was carried out in eastern Kazakhstan and 82 samples of surface soil were collected. This area belongs to East Kazakhstan and Almaty Oblast. It is an industrially developed area of Kazakhstan and an economic zone dominated by non-ferrous metal mining, smelting, hydropower generation and livestock product processing. See Figure 2 for sampling point locations.

Figure 2: Schematic diagram of sampling point locations in eastern Kazakhstan In 2012, a scientific investigation was conducted in Kyrgyzstan, and a total of 40 topsoil samples were collected in three different environments: highways, farmland and rivers. See Figure 3 for the locations of sampling points.

Figure 3: Schematic diagram of sampling point locations in Kyrgyzstan

In 2009, a scientific survey of different geomorphological units of Uzbekistan was conducted from the capital Tashkent to the Aral Sea. During the inspection, both convenient transportation and ensuring the collection of different types of soil were taken into account. The focus was on inspecting soil distributed at different altitudes in the Amu Darya River Basin and different types in the Aral Sea Basin. A total of 31 different types of surface soil samples were collected from 28 points. See Figure 4 for the location of the sampling points.

Figure 4: Schematic diagram of sampling points in Uzbekistan

After freeze-drying, all collected soil samples were ground to 200 mesh, dried in an oven at 105℃, 0.120 - 0.125 g of samples were taken into a nitrification tank, 0.5 mL of hydrochloric acid, 4.0 mL of nitric acid and 3.0 mL of hydrofluoric acid were added, and nitrated in a Berghof MWS-3 microwave nitrification system in Germany. After naturally cooling, transfer it to a polytetrafluoroethylene beaker, add 0.5 mL of perchloric acid and evaporate to dryness, then add 5 mL of 1:3 nitric acid, 0.1 mL of hydrogen peroxide and a small amount of deionized water, and heat to dissolve the residue. After cooling, the volume was constant to 25 mL, the solution was transferred to a polyethylene bottle and stored at 4℃. The concentrations of each chemical element were measured using Leeman Labs Profile ICP-AES(Inductively Coupled Plasma Atomic Emission Spectrometer) in the United States. After freeze-drying soil samples collected in Tajikistan, the contents of 17 elements, including Al, Fe, Ca, Mg, Ti, Co, V, Cr, Sr, Cu, Zn, Mn, Ni, P, Na, Pb and Cd, were determined. After freeze-drying of soil samples from Kazakhstan, the contents of 20 elements including Al, K, Ti, Be, Ba, Fe, Co, Mg, V, Li, Cr, Mn, Na, P, Ni, Zn, Cu, Sr, Ca and Pb were determined. After freeze-drying of soil samples from Kyrgyzstan, the contents of 20 elements including Al, Fe, Ca, Li, Na, K, Mg, Ti, Co, V, Cr, Be, Ba, Sr, Cu, Zn, Mn, Ni, P, and Cd were determined. After freeze-drying of soil samples from Uzbekistan, a total of 19 elements including Al, Fe, Ca, Na, K, Mg, Ti, Co, V, Cr, Be, Ba, Sr, Cu, Zn, Mn, Ni, P and Cd were determined. Among them, Cd was below the detection limit and was not detected.