| Summary: | The stream discharges, dissolved silicon (DSi) concentrations, stable silicon isotopes, radon concentration measured on water samples taken in March, June, July, August and September 2019 in Lake 850, Northern Sweden. Additionally, total organic carbon (TOC), biogenic silica (BSi) concentrations, total nitrogen (TN) concentrations and carbon nitrogen ratios (C/N) as well as conentrations of lead 210 (210Pb) used for dating from short sediment core, which was taken in March 2019 from ice-covered lake are presented. All data were sampled to constrain the recent water and silicon budget of the lake and to identify sources of dissolved silicon in the lake. Water samples for DSi and stable Si isotopes were sampled in HDPE acid-washed 125ml Naglene bottles and filtered directly in the filed through 0.45μm Sterivex filter and further acidified using HCl to pH 2. Water samples for radon concentration measurements were samples in PET 2l bottles, where the water was let to overflow the bottle volume 3 times. DSi was analyzed by molybdate blue method (Strickland and Parsosn, 1972) using Smarrtchem 200, AMS System descrete analyzer. Stable silicon isotopes were performed on cation-exchange collumn cleaned (Georg et al., 2006, DOI:10.1016/j.chemgeo.2006.06.006) samples using MC-ICP-MS at Vegacenter, Stockholm. The time of sampling and temperature was noted down. The samples were measured in upcoming 24 hours by Rn-in-air alpha spectrometer RAD7 (Durringe Inc.). The sediment core analyzes of TOC, TN and C/N were measured on 5 to 10 mg of freeze-dried sediment using elemental analyzer COSTECH ECS4010. The biogenic silica concentrations were determined using weak alkaline extraction by Conley and Schleske, 2001(DOI:10.1007/0-306-47668-1_14) using 30mg of freeze-dried sediment reacting with 40ml of 0.1M Na2CO3 for 5 hours. The DSi concentration in the extracted aliqote was measured using molybdate blue method (Strickland and Parsosn, 1972) using Smarrtchem 200, AMS System descrete analyzer. The core was dated using ORTEC ...
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