Discharges, radon fluxes, dissolved silicon, biogenic silica, stable silicon isotopes of water and sediment samples and XRF data from Lake 850, Northern Sweden

The stream discharges, dissolved silicon (DSi) concentrations, stable silicon isotopes, radon concentration, were 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 concentrations of lead 210 (210Pb) were used for dating from the short sediment core, which was taken in March 2019 from the ice-covered lake are presented. All data were sampled to constrain the lake's recent water and silicon budget 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 Nalgene bottles and filtered directly in the field through a 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. The time of sampling and temperature was noted down. The samples were measured in the upcoming 24 hours by Rn-in-air alpha spectrometer RAD7 (Durringe Inc.). DSi was analyzed by molybdate blue method (Strickland and Parsons, 1972) using Smarrtchem 200, AMS System discrete analyzer. Stable silicon isotopes were performed on cation-exchange column cleaned (Georg et al., 2006) samples using MC-ICP-MS at Vegacenter, Stockholm. 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. Further, the d13C and TOC was performed on de-calcified bulk sediment from 2019 core (250 mg in 50 ml of 5% HCl for 24 h (Brodie et al., 2011)) and analysed with an Elemental Analyser connected to a MAT-252 mass spectrometer at Weizmann Institute of Science, Rehovot. The biogenic silica concentrations were determined using weak alkaline extraction by Conley and Schleske, 2002 using 30mg of freeze-dried sediment reacting with 40ml of 0.1M Na2CO3 for 5 hours. The DSi concentration in the extracted aliquot was measured using the molybdate blue method (Strickland and Parsons, 1972) using Smarrtchem 200, AMS System discrete analyzer. The short core was dated using an ORTEC high-purity germanium detector at Lund University, and R package Plum (Blaauw et al., 2021) was used to build the age-depth model. Cleaned diatoms from the piston sediment core from 1999 (Shemesh et al., 2001) were measured for stable silicon isotopes and data from the uppermost 8 cm was used for mass balance in Zahajská et al. (2021, BGS). The stable silicon isotopes from cleaned diatom material from the entire core was combined with BSi, TOC, C/N, δ13C from the newly collected piston core in 2019 and used for Holocene silicon cycling dynamics in the lake in Zahajská et al. (2021, Holocene). The new core from 2019 was dated using radiocarbon dating at Lund University laboratory, and the age-depth model was constructed using R package Bacon. The whole core was scanned for elemental composition using X-ray fluorescence (XRF) with an ITRAX CS37 at the GLOBE Institute, Copenhagen University, Denmark.