This study examines the release of dissolved and particulate matter due to the permafrost thaw in the Batagay mega thaw slump in central Yakutia (Russia) (67.58°N, 134.77°E) and how it affects the subsequent streams the Batagayka and Yana rivers. In total 11 samples were taken: 5 slump, 3 Batagayka River and 3 Yana River samples, representing the flow path from the slump to the Yana River. The liquid fraction of the samples was analyzed for: electrical conductivity, pH, DOC concentration, concentration of nitrogen and nitrogen compounds, major anion and cation concentrations, stable water isotope ratios, stable carbon isotopes of DOC (d13C-DOC), 14C AMS radiocarbon age of DOC. The solid fraction of the samples was analyzed for: total organic carbon (TOC), total carbon (TC), total nitrogen (TN), stable carbon isotopes of TOC (d13C-TOC), 14C AMS radiocarbon age of solids. The samples were analyzed for hydrogen carbonate content, DOC, nitrogen, and were dated using radiocarbon measurements. When available, particulate matter in suspension was analyzed for total carbon, total organic carbon, total nitrogen and stable carbon isotopes, and were radiocarbon dated. The Batagay mega thaw slump is located in the Siberian Yana Highlands about 10 km southeast of the village of Batagay, which is the municipal centre of the Verkhoyansk district, Sakha Republic (Yakutia). A total of eleven samples were collected during field work in late July to early August 2017. Samples 01, 02, 03, 06 and 08 were taken from inside the slump. Samples 08 and 02 represent the slump main drainage channel ending with 06 at the slump outflow to the Batagayka River. Samples 01 and 03 are side streams which at some point converge with the slump main drainage channel. Sample 04 was taken 5-6km downstream of the slump outflow in the Batagayka river. Samples 07 and 05 are from the Batagayka River directly up- (07) and downstream (05) of the mouth from the slump outflow into the river. Sample 10 represents the outflow of the Batagayka River into the Yana River, while 09, 11 are Yana River samples 50m down- (09) and upstream (11) of the Batagayka outflow. Samples were taken with a 1L Nalgene bottle and frozen until further processing.

Sampled by: T. Opel., K. Boxleitner (Ashastina) --Cations: 30 mL were filtered through disposable 0.45 µm pore size millipore cellulose acetate filter unit (Whatman® AQUA 30/0.45 CA filter unit white rim); for cations: 50 µL of 65% supra-pure nitric acid were added to 8 mL of the sample before measurementAnions: 30 mL were filtered through disposable 0.45 µm pore size millipore cellulose acetate filter unit (Whatman® AQUA 30/0.45 CA filter unit white rim) and frozen before measurement