Resonance Raman imaging as a tool to assess the atmospheric pollution level: carotenoids in Lecanoraceae lichens as bioindicators

• Published in: Environmental science and pollution research international Vol. 23; no. 7; pp. 6390 - 6399
• Main Authors: Ibarrondo, I, Prieto-Taboada, N, Martínez-Arkarazo, I, Madariaga, J. M
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.04.2016; Springer Nature B.V
• Subjects: Air Pollutants - analysis; Air Pollutants - pharmacology; Air pollution; antioxidants; Antioxidants - metabolism; Aquatic Pollution; astaxanthin; Atmospheric Protection/Air Quality Control/Air Pollution; beta-carotene; Biomarkers; Carotenoids; Carotenoids - metabolism; Earth and Environmental Science; Ecotoxicology; Environment; Environmental Chemistry; Environmental conditions; Environmental Health; Environmental Monitoring - methods; Environmental science; image analysis; Indicator species; Lasers; Lecanora; Lecanora campestris; Lecanoraceae; Lichens; Lichens - drug effects; Lichens - metabolism; lutein; Metabolites; Pigments; Pollution; Pollution levels; Radiation; Raman spectroscopy; Research Article; Resonance; screening; Spain; Spectrum Analysis, Raman; Studies; Waste Water Technology; Water Management; Water Pollution Control; Xanthophylls - metabolism; zeaxanthin; Bioindication; lichens; Carotenoids; Raman imaging; Environmental conditions; Lecanoraceae lichens
• ISSN: 0944-1344; 1614-7499
• DOI: 10.1007/s11356-015-5849-9

Raman spectroscopy differentiation of carotenoids has traditionally been based on the ν ₁ position (C = C stretching vibrations in the polyene chain) in the 1500–1600 cm⁻¹ range, using a 785 nm excitation laser. However, when the number of conjugated double bonds is similar, as in the cases of zeaxanthin and β-carotene, this distinction is still ambiguous due to the closeness of the Raman bands. This work shows the Raman results, obtained in resonance conditions using a 514 mm laser, on Lecanora campestris and Lecanora atra species, which can be used to differentiate and consequently characterize carotenoids. The presence of the carotenoid found in Lecanoraceae lichens has been demonstrated to depend on the atmospheric pollution level of the environment they inhabit. Astaxanthin, a superb antioxidant, appears as the principal xanthophyll in highly polluted sites, usually together with the UV screening pigment scytonemin; zeaxanthin is the major carotenoid in medium polluted environments, while β-carotene is the major carotenoid in cleaner environments. Based on these observations, an indirect classification of the stress suffered in a given environment can be assessed by simply analysing the carotenoid content in the Lecanoraceae lichens by using resonance Raman imaging.