Arsenic speciation in Portuguese in situ lichen samples

Area of Science:

• Environmental Science
• Analytical Chemistry
• Biogeochemistry

Background:

• Lichens are sensitive bioindicators of air pollution.
• Arsenic speciation is crucial for understanding its environmental fate and toxicity.
• Natural and anthropogenic sources contribute to arsenic deposition.

Purpose of the Study:

• To quantify arsenic content in Parmelia sulcata lichens.
• To determine the extractability of different arsenic species.
• To investigate arsenic transformation pathways in lichens.

Main Methods:

• Collection of 29 lichen samples from diverse emission loading sites.
• Analysis of total arsenic content using established methods.
• Extraction and quantification of arsenic species (cationic, anionic, As(III), As(V), DMAA).

Main Results:

• Arsenic concentrations ranged from 430 to 5590 microg kg(-1).
• Cationic arsenic forms were extracted at most sites (0.5%–6.6%).
• As(III) exceeded As(V) in some samples, and dimethylarsinic acid (DMAA) was also detected.

Conclusions:

• Arsenic in Parmelia sulcata exists primarily as As(V) or As(III).
• Transformation of As(V) to As(III) and DMAA occurs in lichens.
• Arsenic speciation in lichens reflects environmental exposure and transformation processes.