The Fate of mineral particles in bulk peat and corresponding humic acids throughout an ombrotrophic bog profile: Atmospheric dust depositions vs mineralization processes

Abstract

Peat cores from ombrotrophic bogs have increasingly been recognized as valuable archives of atmospheric dust depositions during millennia. The longest continuous record of atmospheric dust deposition in continental Europe has been provided by Etang de la Gruère (EGr), an ombrotrophic bog in the Jura Mountains of Switzerland, where 6.5 m of peat has accumulated during the past ca. 15,000 years. Analyzing both the ash and the acid-insoluble ash fraction along EGr cores, it is possible to observe that most of inorganic solids supplied to the EGr bog consisted of atmospheric soil dusts derived from the weathering of crustal rocks. Thus, these ash peaks could not have been caused exclusively by processes such as organic matter decay, but they are the result of either an increase in the rate of supply of dust particles, changes in the rates of peat accumulation, or both. Given the variation in dust deposition rates recorded since the Late Glacial, attributing peaks in ash content exclusively to variations in peat decomposition and humification seems to be a questionable, if not dangerous, practice.