Lichen transplants as indicators of gaseous elemental mercury concentrations

Fabrizio Monaci; Stefania Ancora; Luca Paoli; Stefano Loppi; Frank Wania

doi:10.1016/j.envpol.2022.120189

Lichen transplants as indicators of gaseous elemental mercury concentrations

Environ Pollut. 2022 Nov 15:313:120189. doi: 10.1016/j.envpol.2022.120189. Epub 2022 Sep 15.

Authors

Fabrizio Monaci¹, Stefania Ancora², Luca Paoli³, Stefano Loppi⁴, Frank Wania⁵

Affiliations

¹ Department of Life Sciences, University of Siena, Via Mattioli 4, 53100, Siena, Italy. Electronic address: fabrizio.monaci@unisi.it.
² Department of Physical Sciences, Earth and Environment, University of Siena, Via Mattioli 4, 53100, Siena, Italy.
³ Department of Biology, University of Pisa, Via Luca Ghini, 13, 56126, Pisa, Italy.
⁴ Department of Life Sciences, University of Siena, Via Mattioli 4, 53100, Siena, Italy.
⁵ University of Toronto Scarborough, Department of Physical and Environmental Sciences, 1065 Military Trail, Toronto, ON, M1C1A4, Canada.

PMID: 36116569
DOI: 10.1016/j.envpol.2022.120189

Abstract

Lichens play an important role in the biogeochemical cycling of mercury (Hg) and are commonly used as indicators of Hg enrichment in remote and anthropogenically impacted environments. To assess their capacity for Hg uptake and accumulation, we determined the concentration of gaseous elemental mercury (GEM) in air and the concentration of total Hg (THg) in transplanted thalli of two lichen species. Lichen transplants and passive air samplers (PASs) were concurrently deployed, side by side, at 10 sites within an abandoned mining area, characterized by large gradients in atmospheric Hg contamination. Highly variable time-weighted GEM concentrations determined by the PASs, ranging from 17 to 4,200 ng/m³, were mirrored by generally high Hg concentrations in transplanted thalli of both Xanthoria parietina (174-8,800 ng/g) and Evernia prunastri (143-5,500 ng/g). Hg concentrations in the two species co-varied linearly indicating about 60% greater Hg accumulation in X. parietina than in E. prunastri. Whereas Hg uptake in the fruticose E. prunastri increased linearly with GEM, a power law equation with a fractional exponent described the uptake in the foliose X. parietina. Extrapolating the relationships observed here to higher GEM levels yielded concentrations in lichen that agree very well with those measured in an earlier fumigation experiment performed under laboratory-controlled conditions. The uptake model of X. parietina was further verified by correctly estimating GEM concentrations from the THg measured in autochthonous thalli collected from the urban area adjacent to the mine site. Passive sampling can effectively provide time-weighted data of suitable spatial resolution to quantitatively describe GEM assimilation by lichens. Therefore, the combined use of passive sampling and lichen transplants can contribute to a more comprehensive understanding of the role of lichens, and potentially also of other cryptogams, in the deposition of atmospheric Hg to terrestrial ecosystems.

Keywords: Biomonitoring; Mercury uptake; Mining; Passive sampling; Terrestrial ecosystems.

MeSH terms

Air Pollutants* / analysis
Ecosystem
Environmental Monitoring
Lichens* / chemistry
Mercury* / analysis
Mining

Substances

Air Pollutants
Mercury