Supplementary data for: Field and experimental measurements of antimony flux from lake sediment contaminated by gold mining Kuzey Güneşli a, John Chételat a*, Michael J. Palmer b, Katrina Paudyn c, Brittany Astles d, Heather Jamieson c a Environment and Climate Change Canada, National Wildlife Research Centre, Ottawa, Ontario, Canada b North Slave Research Centre, Aurora Research Institute, Aurora College, Yellowknife, Northwest Territories, Canada c School of Environmental Studies, Queen’s University, Kingston, Ontario, Canada d Geography and Environmental Studies, Carleton University, Ottawa, Ontario, Canada * Corresponding Author: John Chételat, email: john.chetelat@ec.gc.ca 1 Contents Table S1. Site information for sediment cores collected to measure antimony flux and porewater arsenic concentrations in Yellowknife Bay (Great Slave Lake, Northwest Territories, Canada). ............................ 2 Table S2. Sediment characteristics (0-3 cm) and antimony fluxes in 28 sediment cores collected from 20 sampling sites in Yellowknife Bay in 2018 and 2019................................................................................... 3 Table S3. Data used to estimate annual load of antimony from the Yellowknife River to the water column of Yellowknife Bay. ...................................................................................................................................... 4 Table S4. Data used to estimate annual load of antimony from Baker Creek to the water column of Yellowknife Bay. .......................................................................................................................................... 5 Table S5. Data used to estimate annual load of antimony from sediments in the nearfield area of Yellowknife Bay. .......................................................................................................................................... 6 Figure S1. Map of Yellowknife Bay (Great Slave Lake, Northwest Territories, Canada) with the boundaries of cells used to model sediment load. Sediment loads of antimony were estimated using the surface areas of cells 1, 2 and 8 in the nearfield area. ................................................................................... 6 2 Table S1. Site information for sediment cores collected to measure antimony flux and porewater antimony concentrations in Yellowknife Bay (Great Slave Lake, Northwest Territories, Canada). Site name Field IDs for cores/sites Sampling dates Porewater sampling? Latitude (°N) Latitude (°W) Water depth (m) S1 C1* Aug 2018 no 62 25 37.74 N 114 19 39.30 W 17 S2 C2* Aug 2018 no 62 27 12.54 N 114 20 11.82 W 12 S3 C3, WC3*, SC3* Aug 2018, Mar 2019 yes 62 28 30.66 N 114 19 45.90 W 19 S4 C4, C5 Aug 2018, Mar 2019 yes 62 28 58.26 N 114 20 25.44 W 10 S5 C6* Aug 2018, Mar 2019 yes 62 29 11.10 N 114 21 05.16 W 10 S6 C7 Aug 2018 no 62 28 23.40 N 114 21 36.84 W 2 S7 C8 Aug 2018 no 62 28 37.56 N 114 20 21.96 W 1 S8 C9*, C10 Aug 2018, Mar 2019 yes 62 29 16.02 N 114 21 28.38 W 8 S9 C11 Aug 2018 no 62 29 42.78 N 114 20 38.52 W 1 S10 C12 Aug 2018 no 62 29 41.22 N 114 18 56.58 W 3 S11 FS1 Jul 2019 no 62 27 33.08 N 114 19 36.84 W 2 S12 FS2 Jul 2019 no 62 28 00.44 N 114 21 20.09 W 3 S13 FS3 Jul 2019 no 62 29 24.07 N 114 20 02.33 W 2 S14 FS4 Jul 2019 no 62 29 58.13 N 114 19 52.36 W 4 S15 LD1 Jul 2019 no 62 26 27.13 N 114 19 51.20 W 20 S16 LD2 Jul 2019 no 62 28 28.52 N 114 21 02.02 W 6 S17 LD3, BCS* Jul 2019 yes 62 28 52.46 N 114 21 19.62 W 10 S18 LD4, D1* Jul 2019 yes 62 29 21.19 N 114 20 49.85 W 9 S19 LD5 Jul 2019 no 62 29 12.77 N 114 19 16.97 W 10 S20 LD6 Jul 2019 no 62 29 48.48 N 114 20 11.08 W 7 * Site IDs used by Paudyn et al. (2023) for the same locations as this study Paudyn KA, Jamieson HE, Chételat J, Schuh CE, Palmer MJ, and McHale S. 2023. Geogenic, anthropogenic, and authigenic solid phases hosting arsenic and antimony in Yellowknife Bay sediments. The Canadian Mineralogist, accepted (22-00035). 3 Table S2. Sediment characteristics (0-3 cm) and antimony fluxes in 28 sediment cores collected from 20 sampling sites in Yellowknife Bay in 2018 and 2019. Characteristic (n = 28) Mean (± SD) Range Antimony flux (µg m-2 day-1) 50 ± 68a 0 - 279 Antimony concentration (µg g-1) 14 ± 15 0.7 - 47 Iron concentration (mg g-1) 33.5 ± 6.7 16.3 - 43.1 Manganese concentration (µg g-1) 1622 ± 1086 235 - 4173 Sulphur concentration (µg g-1) 496 ± 244 200 - 1200 Total organic carbon (%) 1.6 ± 0.4 0.3 - 2.4 Dissolved oxygen saturation (%) at 1 cm sediment depthb 15 ± 12 1 - 40 Water depth at collection site (m) 8.6 ± 5.4 1.1 - 19.8 Water temperature (°C) 11 ± 4 4 - 19 a n = 17, mean calculated only for cores with a detected flux (i.e. non-zero) b n = 22 4 Table S3. Data used to estimate annual load of antimony from the Yellowknife River to the water column of Yellowknife Bay. Month Monthly average discharge Water Sb load m3/s m3/day # days L/month [Sb] µg/L* kg/month Jan 35.957 3106697 31 96307611429 0.1/0.05 10/5 Feb 32.367 2796480 28 78301440000 0.1/0.05 8/4 Mar 29.129 2516709 31 78017965714 0.1/0.05 8/4 Apr 26.305 2272731 30 68181942857 0.1/0.05 7/4 May 33.457 2890697 31 89611611429 0.1/0.05 9/5 Jun 45.200 3905280 30 1.17158E+11 0.1/0.05 12/6 Jul 53.055 4583931 31 1.42102E+11 0.1/0.05 14/7 Aug 46.740 4038295 31 1.25187E+11 0.1/0.05 13/7 Sep 39.880 3445673 30 1.0337E+11 0.1/0.05 10/5 Oct 37.215 3215355 31 99676018286 0.1/0.05 10/5 Nov 37.300 3222720 30 96681600000 0.1/0.05 10/5 Dec 37.386 3230126 31 1.00134E+11 0.1/0.05 10/5 Total load (kg/year) 119/62 *Two load estimates were generated using the analytical detection limit and half the detection limit (see below for details). Data sources:  River discharge for the Yellowknife River (1996-2016) from the Water Survey of Canada (Environment and Climate Change Canada, data available online at https://wateroffice.ec.gc.ca/mainmenu/historical_data_index_e.html)  Discharge station name: Yellowknife River at Outlet of Prosperous Lake (07SB002)  Background water antimony concentration (0.1 µg/L) near the mouth of the Yellowknife River was estimated using water quality monitoring data (n=37 samples between 2013 to 2022) obtained from the GNWT (2023) via the Mackenzie Datastream open data portal  The majority (95%) of the Yellowknife River water samples had Sb concentrations below analytical detection (<0.1 µg/L). We generated a range estimate of Sb load from the Yellowknife River using the detection limit (0.1 µg/L) and half the detection limit (0.05 µg/L) as the mean Sb water concentration. References GNWT. 2023. Communities of the Northwest Territories, NWT-wide Community Based Water Quality Monitoring Program, Government of the Northwest Territories, Environment and Climate Change. 2023-06-07. "NWT-wide Community-based Monitoring Program" (dataset). 10.0.0. DataStream. https://doi.org/10.25976/4der-gd31. https://wateroffice.ec.gc.ca/mainmenu/historical_data_index_e.html 5 Table S4. Data used to estimate annual load of antimony from Baker Creek to the water column of Yellowknife Bay. Month Monthly average discharge Water Sb load m3/s m3/day # days L/month [Sb] µg/L kg/month Jan 0.15 13278 31 411627789 144 59 Feb 0.12 10644 28 298022400 144 43 Mar 0.10 8994 31 278808686 144 40 Apr 0.10 8800 30 264013714 144 38 May 0.96 83269 31 2581339886 35 90 Jun 0.52 44541 30 1336237714 47 63 Jul 0.13 13420 31 416028267 125 52 Aug 0.09 9774 31 303006835 234 71 Sep 0.09 10370 30 311096000 187 58 Oct 0.21 18403 31 570499200 274 156 Nov 0.20 17086 30 512568000 144 74 Dec 0.16 13837 31 428945760 144 62 Total load (kg/year) 806 Data sources:  River discharge for the Baker Creek (1996-2016) from the Water Survey of Canada (Environment and Climate Change Canada, data available online at https://wateroffice.ec.gc.ca/mainmenu/historical_data_index_e.html)  Discharge station name: Station 07SB013 Baker Creek (outlet from Lower Martin Lake)  Effluent from Giant Mine is discharged into Baker Creek downstream of the gauging station at an average rate of 65000 m3 per month in July, Aug, Sept. This discharge was added to the monthly averages from the gauging station.  Water antimony concentrations were obtained from unpublished surveillance network program (SNP) water monitoring under the Giant Mine water licence (2012-2017, n = 146 sampling dates). Water sampling was conducted between May and October each year at the mouth of Baker Creek. Monthly water concentration data were used when available. For November to April, the average water antimony concentration for the entire dataset was used as an estimate. https://wateroffice.ec.gc.ca/mainmenu/historical_data_index_e.html 6 Table S5. Data used to estimate annual load of antimony from sediments in the nearfield area of Yellowknife Bay. Variable Value Surface Area of nearfield (m2) 5851057 Mean Sb flux (µg/m2/day) 50 Median Sb flux (µg/m2/day) 22 Days per year 365 Total load (kg/year) – Mean 107 Total load (kg/year) – Median 47 The median and mean Sb flux (n = 17) was calculated using only cores where fluxes were detected. Figure S1. Map of Yellowknife Bay (Great Slave Lake, Northwest Territories, Canada) with the boundaries of cells used to model sediment load. Sediment loads of antimony were estimated using the surface areas of cells 1, 2 and 8 in the nearfield area. Table S1. Site information for sediment cores collected to measure antimony flux and porewater antimony concentrations in Yellowknife Bay (Great Slave Lake, Northwest Territories, Canada). Table S2. Sediment characteristics (0-3 cm) and antimony fluxes in 28 sediment cores collected from 20 sampling sites in Yellowknife Bay in 2018 and 2019. Table S3. Data used to estimate annual load of antimony from the Yellowknife River to the water column of Yellowknife Bay. Table S4. Data used to estimate annual load of antimony from Baker Creek to the water column of Yellowknife Bay. Table S5. Data used to estimate annual load of antimony from sediments in the nearfield area of Yellowknife Bay.