Accumulation of low-molecular-weight organic acids in wetlands and influence on the formation of natural acidic environments

Surface water in wetlands is a naturally heavily diluted, equilibrium-state and self-regulating system. This article examines the hydrochemical composition of surface water in the oligotrophic bogs Blizkoye and Agvensuo (the Republic of Karelia). The redox potential and the acidity of Blizkoye bog water are variable during the growing season. The low-molecular-weight organic acids (formic, acetic, oxalic, lactic, and citric acids) were identified and their seasonal variations in dissolved organic matter from May through August were followed in relation to water pH. The content of organic acids in the surface water of Blizkoye bog formed the following sequence: acetic > formic > lactic > oxalic. Citric acid was found in trace amounts. The content of low molecular weight carbonic acids increased until July. The total content of the acids in dissolved organic matter in Blizkoye bog was 2.7% in May, 7.7% in June, 11.4% in July, and 2.0% in August. A linear dependence was found for the concentration of formate and oxalate ions in bog water. The redox potential of surface waters plays a crucial role in the accumulation of acetic and lactic acids.