Mercury content and elemental composition of fruticose lichens from Nahuel Huapi National park (Patagonia, Argentina): Time trends in transplanted and in situ grown thalli

BUBACH, D F; PÉREZ CATÁN, S.; ARRIBERE MA; DIÉGUEZ, MC; GARCÍA, PE; MESSUTI, M.I.

Atmospheric Pollution Research

Elsevier B.V.

Año: 2024 vol. 15 p. 1 - 12

Lichens have a unique structure involving the symbiosis of fungus and algae, and can grow in almost any type of substrate. They absorb gases, water, nutrients and pollutants through their cortex, and thus are good indicators of environmental processes, enabling the biomonitoring of environmental pollutants. These organisms are widely distributed; however, as some species do not occur in some areas, transplants are commonly used to monitor air pollution. In this study, transplants of the fruticose species Protousnea magellanica were set up at the EMMA Station (Global Mercury Observation System, GMOS) located at a suburban site of San Carlos de Bariloche city within Nahuel Huapi National Park (North Patagonia, Argentina) to assess the uptake of different elements and particularly the accumulation of mercury. Periodic samplings of the transplanted species P. magellanica and the naturally occurring Usnea pusilla were performed concurrently at the experimental site, along 483 days of experimental exposure. In both species, the elemental composition and concentration of the thalli were determined by Neutron Activation Analysis in a nuclear reactor. Atmospheric mercury concentration (Gaseous Elemental Mercury, GEM) was monitored at the EMMA Station by an automated cold vapor atomic fluorescence system (Tekran 2537B). Mercury concentrations in the lichens were at least three orders of magnitude higher than atmospheric mercury levels (0.80-0.94 ng/m3, ppt) highlighting the accumulation capacity of these organisms. The concentrations found in thalli of P. magellanica (0.080-0.327 µg/g dry weight, ppm) were in the range of values reported previously from a site of Nahuel Huapi National Park with low anthropogenic impact. During the experimental exposure both lichen species followed displayed the same trend regarding their Hg content. Total Hg content level increased 25 days after 25 days of the start of ing the experiment, and then decreased approximately up to 385 days. In U. pusilla, the positive relationship of Hg content with lithophilic elements (ie, La) suggested a preferential Hg uptake of from airborne particles (deposited dust).