Biomonitoring of traffic-related nitrogen pollution using Letharia vulpina (L.) Hue in the Sierra Nevada, California

• Published in: The Science of the total environment Vol. 490; pp. 205 - 212
• Main Authors: Bermejo-Orduna, R., McBride, J.R., Shiraishi, K., Elustondo, D., Lasheras, E., Santamaría, J.M.
• Format: Journal Article
• Language: English
• Published: Kidlington Elsevier B.V 15-08-2014; Elsevier
• Subjects: Air Pollutants - analysis; Animal, plant and microbial ecology; Applied ecology; Biological and medical sciences; California; Critical load; Ecotoxicology, biological effects of pollution; Environmental Monitoring - methods; Environmental Pollution - statistics & numerical data; Fundamental and applied biological sciences. Psychology; Heavy metals; Isotopic signature; Letharia vulpina; Lichens - chemistry; Nitrogen; Nitrogen - analysis; Terrestrial environment, soil, air; Traffic pollution; Vehicle Emissions - analysis; California; United States; North America; America; USA, California, Sierra Nevada Mts; USA, California; Letharia vulpina; Isotopic signature; Critical load; Nitrogen; Traffic pollution; Heavy metals; Epiphyte; Biological indicator; Isotopic composition; Motor vehicle; Heavy metal; Fungi; Trace element; Environment impact; Pollution source; Lichenes; Air pollution; Road traffic; Mixed forest stand; Coniferous forest
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2014.04.119

To assess the impact of vehicular emissions on a mixed conifer forest, we measured the contents of the trace elements, N, C, and their respective natural isotopes (δ15N and δ13C), in the epiphytic lichen, L. vulpina. The samples were collected along transects perpendicular to Interstate 80 (I-80) and along a more remote, secondary forest road (R07). Distance to the road verge, trunk cover, and stand basal area were also recorded. Percent N ranged from 1.10% to 2.00% near I-80 and from 0.78% to 1.13% along R07. Concentrations of N, 15N, Na, As, Pb, and Zn were enhanced in lichen samples near I-80 and were negatively correlated with distance from the road. Trunk cover values differed between roads (p<0.001) and were negatively correlated with %N (r2=0.74; p<0.001). The results indicate that vehicular N emissions are significant enough to alter the surrounding ecosystem, modifying the presence of a sensitive component such as L. vulpina, and suggest that a clean-site threshold of 1.0%N may be too high as an indicator of critical N load exceedance. The study also underscored the potential role of wolf lichen in a large-scale assessment of N deposition and source identification.
•Trace elements, %N and d15N were determined in lichens growing around two roads.•The proximity to roads resulted in enhanced N and trace elements concentrations.•Increases in N and 15N concentrations correlated with a reduction in lichen cover.•N deposition associated with traffic emissions exceeded the empirical critical load.•Arsenic concentrations in Letharia vulpina are a useful marker of traffic intensity.