Geochemical features of high and transitional moors under the impact of waste pits

Waste pits represent a significant ecological problem for oil–gas fields of the Khanty-Mansi Autonomous Okrug (Yugra) in Western Siberia. Drilling sludge contained in them results in chemical contamination of moors. Seven areas adjacent to waste pits were investigated. We determined the content of macro-, micro- and rare-earth elements in peat of undisturbed high moors in the middle taiga of the Middle Ob region and compared these data with their background contents and clarke values. The contents of macroand microelements in peat of the background areas of oilfields are higher for the Surgutskoe Poles’e deposit than for the Samotlor field. Waste pits increase in content of all investigated macro- and microelements in peat. The most intensively accumulated macroelements in the impact zones are typically chlorine, potassium, magnesium, and iron; the most intensively accumulated microelements are boron, strontium, nickel, and rubidium. Microelements accumulate in the top peat layer, while the accumulation of macroelements is more specific. Waste pits result in a one- to threefold increase in the pH of the peat water suspension, a threefold increase in the ash content in peat, and in sevenfold increase in the electric conductivity of peat water suspension. The impact of waste pits is stronger in the Samotlor oil-and-gas field than in the Surgutskoe Poles’e deposit, which can be explained by different histories of their development. Waste pits considerably alter the geochemical parameters of high moors, creating conditions for meso- and eutrophic vegetation.