Towards a data driven understanding of dissolved organic matter in the critical zone This dissertation presents modern approaches for the identification of molecular markers and marker patterns as indicators for natural processes that transform dissolved organic matter (DOM) in the Critical Zone. The attached manuscripts describe the transformation of plant derived DOM in the litter layer soils and aquifers. The results of these investigations show that the interdisciplinary integration of untargeted ultrahigh resolution mass spectrometry data on DOM composition with hydrological isotopic and microbial information can substantially improve our understanding of the functioning of the Critical Zone.