Assessment of Air Pollution in Hai Phong City (Vietnam) Using Lichens as Biomonitors

Lichens are widely used as bioindicators of air pollution. This study aims to evaluate the accumulation of potentially toxic elements in lichens Usnea articulata (L.) Hoffm to assess atmospheric pollution in Hai Phong city, Vietnam. The content of Al, Cd, Co, Cr, Cu, Fe, Mn, Ni, P, Pb, S, Sr, V, Zn, and Hg in exposed and unexposed lichen samples was determined using Inductively Coupled Plasma-Optical Emission Spectrometry and a direct mercury analyzer. Analysis data showed that mean content of all elements, except Hg and S, was higher in exposed lichens. High levels of Zn, Al, Mn, Fe, V, and Ni were found in samples exposed near industrial zones. The Relative Accumulation Factor revealed lichens enrichment in Al, Co, Mn, Fe, and V, as well as a depletion of Hg and S. Correlation and principal component analyses identified the predominant sources of elements deposition as industrial activity, coal combustion, and transport activity. Based on contamination factor values, the level of air pollution in Hai Phong can be classified as suspected with low ecological risk index values. Additionally, the assessment of exposure to potentially toxic elements through inhalation, ingestion, and dermal contact allowed determination of the hazard index values, which did not exceed unit at any exposure sites. For future research, long-term or multi-seasonal biomonitoring studies should be conducted in this area.