INTERANNUAL AND SEASONAL VARIABILITY OF CHEMICAL RUNOFF ALONG THE MAIN DELTA BRANCHES OF THE KUBAN RIVER

Abstract

The long-term interannual and seasonal variability of the chemical runoff along the main branches of the Kuban River delta was investigated. We analyzed the data of systematic observations on water runoff and the concentrations of the main ions, biogenic and organic substances, phenols, oil products and heavy metals for the period from 2008 to 2018. The annual and seasonal runoff of dissolved chemicals in the main branches of the Kuban River delta, i. e. the Protoka branch and the Kuban branch, was calculated. The chemical composition of water in the main branches of the Kuban River delta is practically the same, and the greatest differences are characteristic of the con-centrations of chlorides, iron compounds, copper and oil products. Multidirectional trends of changes in the ionic composition and content of biogenic elements were revealed. There was a synchronous increase in the concentration of sulphates and ammonium nitrogen in both deltaic branches of the Kuban River; the content of nitrates and nitrites in the Kuban branch practically did not change, while it was decreasing in the Protoka branch. At the same time, the maximum frequency of exceeding the MPC for all components is rather low, and a low level of water pollution is typical. The chemical runoff along the delta branches is rather similar, especially in terms of the runoff of sulphates, organic substances and biogenic elements. The greatest differences by 20-22% are observed in the runoff of chlorides, iron and copper compounds. It is shown that the runoff of chlorides and sulphates, as well as biogenic and organic substances, is interconnected with water runoff. In general, the distribution of chemical runoff along the delta branches is uniform, its seasonal variability corresponds to changes in water amount during the principal seasons, while some differences are observed only for chlorides and iron compounds. Under actual climatic changes and anthropogenic impact, the revealed features and trends of variability of chemical runoff along the main branches of the Kuban River delta are of great practical importance. The data obtained can be used for predictive estimates of the removal of chemicals into the coastal zone of the Sea of Azov.