Analysis of organic and inorganic sulfur constituents and 34S-isotopes in dated sediments of Forest Lakes in southern Finland

Abstract

A modification of the Jonson-Nishita digestion-distillation apparatus was used to determine the S constituents of sediments from three forest lakes (Munajarvi, Orajarvi, and Sorvalampi) in southern Finland. Lakes Munajarvi and Orajarvi had undergone marked acidification during the past 30 yr or so presumably due to acid deposition as revealed from sedimentary diatom and chrysophycean remains. Organic S constituted a major part of the total S, and during the recent years the portion of C-bonded S increased in the Lakes Munajarvi and Sorvalampi more strongly than the portion of sulfate esters. In the case of Lake Orajarvi the concentration of total S increased by a factor of 2.3 from its preindustrial level which seems to be due to an increase of both C-bonded S and SO4 −2. Coincidentally with the up core increase in total S, the sediment cores of Orajarvi and Munajarvi were strongly depleted of the 34S-isotope (r = −0.83 in Orajarvi n = 15, and r = − 0.84 in Munajarvi n = 10). This implies that the recent changes in sedimentary S are related to the increasing input of airborne pollutant S since about 1850 in Orajarvi and 1950 in Munajarvi provided that the 210Pb dating of the cores is correct and diagenetic changes have not greatly altered the vertical distribution of S in these sediments.