The use of passive lichen biomonitoring in combination with positive matrix factor analysis and stable isotopic ratios to assess the metal pollution sources in throughfall deposition of Bolu plain, Turkey

Abstract

The main objective of this study was to determine the elemental content of (51 elements) and stable isotope (δ13C, δ15N) content of lichen, Xanthoria parietina. The results were evaluated according to seasonal changes, pollution source, and altitudes. The data indicated that there is no significant impact of seasonal variation in concentrations of most of the elements and isotopes. The uptake efficiency of Xanthoria parietina and pine needle was compared and it was found out that significantly higher amounts of metals were accumulated by Xanthoria parietina than by pine needles. The lowest δ13C and the highest δ15N values were obtained in pine needle in both seasons. Both δ13C and δ15N showed increasing (for summer) and decreasing (for winter) trends with a rise in an altitude. Source apportionment of elements was performed by using positive matrix factorization (PMF) and supported by G-score maps. As a result, six sources were determined for the area namely urban environment, lichen nutrient elements, contaminated soil, traffic and mixed soil, lichen metabolism and coal combustion. The concentration pollution maps and G-score maps of Pb and Ba were similar and this was an indication of the vehicle emissions. The elements As, Bi and Tl signed the coal combustion.