Water and soil chemistry and molecular composition data of dissolved organic matter from soils in the central Amazon rainforest, 2019-2021

This dataset was created based on sampling campaigns in the central Amazon rainforest. It covers four field sites in vicinity of the Amazon Tall Tower Oberservatory project (ATTO). The field sites are comprised of pristine, old-growth rainforest with distinct forest types: terra firme forest (Plateau and Terrace sites) and white-sand forest (Campina and Campinarana sites). Freely percolating soil porewater was sampled repeatedly in soil profiles from 0 to 30 cm in the wet seasons (October to May) of 2019, 2020 and 2021. Solid soil samples were taken in vicinity to the plots in October 2017. The datasets include chemical and texture (particle size fractions) and chemical (metals, cation exchange capacities and pH) data from soil samples. Soil porewater samples were measured for pH, electrical conductivity and dissolved organic carbon (DOC) concentrations. There are some missing values for these data, particularly for DOC concentrations. Soil porewater samples were used for solid-phase extraction of dissolved organic matter (DOM). The molecular composition was measured by ultra-high resolution mass spectrometry (Orbitrap Elite MS). The detected masses were used to assign molecular formulas. The data include the assigned molecular formulas and sum-normalized intensites of all samples. This data is associated with a Ph.D. dissertation chapter (Lange, 2025) and a journal article (Lange et al., accepted).