Co-sampled fruticose and foliose epiphytic lichens as spatial biomonitors of airborne mercury and arsenic in a historical "Gold Rush" mining district

Smith, Michael P.1 ; Campbell, Linda M.1 ; Richardson, David H.S.1; Parsons, Michael B.2; Rickwood, Carrie J.3

Published Dec 08, 2025 on Dryad. https://doi.org/10.5061/dryad.zgmsbccsc

Data files

Dec 08, 2025 version files 12.02 KB

Raw_data_smith_et_al.zip

6.36 KB
README.md

5.66 KB

Abstract

Historical gold mine tailings may have elevated total mercury (THg) and total arsenic (TAs) concentrations. We collected and analyzed the fruticose lichen genus Usnea and the foliose lichen genus Platismatia for biomonitoring airborne sources of Hg and As at the historical Montague Gold Mine District in Nova Scotia, Canada. We investigated spatial trends of Hg and As measured from 112 Usnea (10 species) and 113 Platismatia (2 species) lichen thalli collected across four sampling grids covering both tailings and non-tailings areas. Usnea consistently had higher THg concentrations, while Platismatia showed higher TAs concentrations. Areas where there was evidence of known past mining activities (i.e. mine shafts, stamp mills, Hg-amalgamation sites) were found to be hotspots for both Hg and As in the lichen samples collected nearby. These areas likely received greater inputs of these elements from windblown tailings or volatilization processes, or indirectly from the interception of these elements by the forest edge/canopy adjacent to the tailings. A tailing-contaminated wetland at Montague was also identified as a hotspot for Hg, likely facilitating its redistribution into the atmosphere. Co-sampling of a fruticose and a foliose lichen can be an effective method for airborne monitoring of contaminants around historical mine tailing sites.

Dataset DOI: 10.5061/dryad.zgmsbccsc

Description of the data and file structure

The goals of our research were (1) to assess the feasibility of co-sampling two morphologically different epiphytic lichens (fruticose vs foliose spp.) for biomonitoring airborne mercury (Hg) and arsenic (As) at the Montague gold mine tailings site in Nova Scotia, and (2) to investigate the fine-scale geospatial distribution patterns of Hg and As concentrations in the co-sampled lichens at Montague and interpret any spatial trends along a distance gradient from the tailings. Lichens (Usnea and Platismatia spp.) were sampled from spruce (Picea spp.) trees in July and August of 2019 across four sampling grids at Montague. Each sample was identified to the species level, homogenized, and analyzed for total mercury (THg) and total arsenic (TAs) concentrations. This raw data was then analyzed spatially in ArcGIS using interpolation modelling as well as other datasets and geoprocessing tools.

Files and variables

File: Raw_data_smith_et_al.zip

Description: Raw mercury and arsenic concentration (μg/kg) data measured from Usnea and Platismatia lichens sampled at the Montague Gold Mining District, Nova Scotia, Canada.

Variables for Usnea_raw_data.csv file:

Site: Site number or code, based on the georeferenced sampling points on Grids 1, 2, 3, and 4. The site numbers refer to sites (grid intersection points) on Grids 1-4. Specific site codes were used for some of our early lichen samples collected. These include: MO3 (Montague-3), MO2 (Montague-2), BR1 (Barry's Run), OSMA (Old Stamp Mill A), OSMB (Old Stamp Mill B), OSM1 (Old Stamp Mill 1), and MBRef (Mitchell Brook Reference).
Latitude: Latitude coordinate where the lichen sample was collected, in decimal degrees.
Longitude: Longitude coordinate where the lichen sample was collected, in decimal degrees.
Grid_Number: Based on the sampling design, grid in which the site falls within (Grid 1, 2, 3, or 4).
Distance_to_Nearest_Tailings_Edge: The distance of each sampling site to the nearest tailings edge, in metres (m). Buffer polygons of 100 m were created around the Montague tailings layer, and each sampling site that fell within each buffer was denoted that distance category (e.g. On Tailings, 0-100m, 100-200m, 200-300m, and >300m).
Land_Type: Each sampling site was sorted into the corresponding land type (road corridor, natural forest stand, urban, wetland, treed bog, and wind throw), determined using the Nova Scotia Forest Inventory dataset (https://novascotia.ca/natr/forestry/gis/dl_forestry.asp). See the Figshare online resource for descriptions of each land type: https://doi.org/10.6084/m9.figshare.22094969.v8.
Species: Usnea species collected at the site, as identified from chemical spot tests.
Usnea _THg_concentration: Total mercury concentration measured in the collected Usnea sample (µg/kg). Missing values are populated with "NA".
Usnea _TAs_concentration: Total arsenic concentration measured in the collected Usnea sample (µg/kg). Missing values are populated with "NA".

Variables for Platismatia_raw_data.csv file:

Site: Site number or code, based on the georeferenced sampling points on Grids 1, 2, 3, and 4. The site numbers refer to sites (grid intersection points) on Grids 1-4. Specific site codes were used for some of our early lichen samples collected. These include: MO2 (Montague-2), BR1 (Barry's Run), OSMA (Old Stamp Mill A), OSMB (Old Stamp Mill B), OSMC (Old Stamp Mill C), OSM1 (Old Stamp Mill 1), and MBRef (Mitchell Brook Reference).
Latitude: Latitude coordinate where the lichen sample was collected, in decimal degrees.
Longitude: Longitude coordinate where the lichen sample was collected, in decimal degrees.
Grid_Number: Based on the sampling design, grid in which the site falls within (Grid 1, 2, 3, or 4).
Distance_to_Nearest_Tailings_Edge: The distance of each sampling site to the nearest tailings edge, in metres (m). Buffer polygons of 100 m were created around the Montague tailings layer, and each sampling site that fell within each buffer was denoted that distance category (e.g. On Tailings, 0-100m, 100-200m, 200-300m, and >300m).
Land_Type: Each sampling site was sorted into the corresponding land type (road corridor, natural forest stand, urban, wetland, treed bog, and wind throw), determined using the Nova Scotia Forest Inventory dataset (https://novascotia.ca/natr/forestry/gis/dl_forestry.asp). See the Figshare online resource for descriptions of each land type: https://doi.org/10.6084/m9.figshare.22094969.v8.
Species: Platismatia species collected at the site, as identified from chemical spot tests.
Platismatia _THg_concentration: Total mercury concentration measured in the collected Platismatia sample (µg/kg).
Platismatia _TAs_concentration: Total arsenic concentration measured in the collected Platismatia sample (µg/kg). Missing values are populated with "NA".

Access information

Other publicly accessible locations of the data:

https://arcg.is/zCa1H