Distribution of dissolved and suspended forms of heavy metals in the water of the Syr Darya, South Kazakhstan

The water of the Syr Darya is the main source of fresh water in South Kazakhstan and heavily used for agriculture. The use water from the Syr Darya for irrigation of agricultural fields affects its chemical composition and is reflected in the water quality class provided in the bulletins of the Ministry of Ecology, Geology and Natural Resources of the Republic of Kazakhstan. In the present work, the distribution of suspended and dissolved forms of heavy metals in the water of the Syr Darya has been studied in two areas – the upper reaches of the river from the Shardara reservoir to the «Koksaray» bridge and the lower reaches of the river from Turkestan to Terenozek. Concentrations of heavy metals and metalloids were determined by inductively coupled plasma mass spectrometry (ICP-MS, Agilent 7500A, United States) and compared to these recommended levels. Total concentrations of several metals (V, Cu, Mn, Fe, Sr) exceed the Maximum Permissible Concentrations established for waters of fishery reservoirs. The role of the suspended form in the geochemical migration of a number of metals in the water of the Syr Darya River is estimated and it was shown that this form is a significant fraction of the total metal concentration. The distribution of suspended forms of metals correlates to the turbidity of the water of the Syr Darya.