Dataset: Fourier Transform-Ion Cyclotron Resonance Mass spectrometry (FT-ICR MS) peaks lists from the Tapajós River, Brazil from 2016-2023

Water samples were collected near‐monthly from the Tapajós River upstream of Itaitubam Brazil (-4.3375,-56.06953). Three water samples (1 L) were collected at 0.5 m depth from the river across the channel in equal spacing and combined into a 4 L acid‐washed carboy to make a composite sample.  Water samples  were collected at 0.5 m depth from the river across the channel in equal spacing.The water was filtered through a 0.45 μm capsule filter with a peristaltic pump into acid‐rinsed high‐density polyethylene (HDPE) bottles. Filtered samples were kept cold during transport and immediately frozen upon transfer to the laboratory and kept in the dark until analysis.

Mass spectral peaks (>6σ root‐mean‐square (RMS) baseline noise) were exported to a peak list and processed using PetroOrg. Molecular formulae were assigned to ions constrained by C4‐75H4‐150O1‐30N0‐4S0‐2 not exceeding 300 ppb error. The resulting peak list includes all confidently assigned molecular formulae across every analyzed sample. Individual molecular formulae peaks can be compared between samples and bulk stoichiometric parameters (e.g., mean H/C , O/C ratio) can be determined for each sample in this dataset.