Hydrochemistry data for thaw slump upstream, downstream, and rill samples, collected between July 21 - 27, 2019.

Total and dissolved mercury were measured using oxidation, purge and trap, and Cold Vapor Atomic Fluorescence Spectrometry on a Tekran 2600 Total Mercury Analyzer.Methylmercury and dissolved methylmercury were measured by isotope dilution, distillation, aqueous ethylation, purge and trap, gas chromatography and inductively coupled plasma mass spectrometry using a Tekran 2750 Methyl Mercury Distillation System, Tekran 2700 Methyl Mercury Analyzer, and Agilent 7900 ICP-MS.Filterable and nonfilterable residue concentrations (i.e., total dissolved and total suspended solids; TDS and TSS) were derived from masses of, respectively, evaporated, and dried materials of known original volumes.MDL: method detection limit