Investigation of spatial and temporal metal atmospheric deposition in France through lichen and moss bioaccumulation over one century

Abstract

Lichens and mosses were used as biomonitors to assess the atmospheric deposition of metals in forested ecosystems in various regions of France. The concentrations of 17 metals/metalloids (Al, As, Cd, Co, Cr, Cs, Cu, Fe, Mn, Ni, Pb, Sb, Sn, Sr, Ti, V, and Zn) indicated overall low atmospheric contamination in these forested environments, but a regionalism emerged from local contributions (anthropogenic activities, as well as local lithology). Taking into account the geochemical background and comparing to Italian data, the elements from both natural and anthropogenic activities, such as Cd, Pb, or Zn, did not show any obvious anomalies. However, elements mainly originating from lithogenic dust (e.g., Al, Fe, Ti) were more prevalent in sparse forests and in the Southern regions of France, whereas samples from dense forests showed an accumulation of elements from biological recycling (Mn and Zn). The combination of enrichment factors and Pb isotope ratios between current and herbarium samples indicated the historical evolution of metal atmospheric contamination: the high contribution of coal combustion beginning 150 years ago decreased at the end of the 20th century, and the influence of car traffic during the latter observed period decreased in the last few decades. In the South of France, obvious local influences were well preserved during the last century.

Evaluation of lichen species resistance to atmospheric metal pollution by coupling diversity and bioaccumulation approaches: A new bioindication scale for French forested areas

“…Metal atmospheric pollution has already been studied for these sites through surface horizons of soils (Gandois et al, 2010a;Hernandez et al, 2003), bulk atmospheric deposition (Gandois et al, 2010b), and lichen bioaccumulation (Agnan et al, 2015). The metal concentrations registered in lichens collected on the trees considered for bioindication are given in Table 2.…”

“…We followed the standardized European protocol (EN 16413, 2014), leaving the random sampling to maximize the number of lichen species by increasing the tree diversity (Moreau et al, 2002). Since we aimed to evaluate the metal resistance and sensitivity of lichens by combining bioaccumulation and diversity approaches, we thus followed the same procedure as for bioaccumulation study (Agnan et al, 2015). The four cardinal points of the tree trunks were sampled using a ladder grid of five vertical squares of 10 cm × 10 cm to cover an area of 500 cm 2 per tree side and a total area of 24000 cm 2 (i.e., 240 squares) for …”

“…Summary of metal bioaccumulation (mean ± standard deviation, in g g −1 ) in three foliose lichen species (i.e., X. parietina, P. sulcata, and H. physodes) from the investigated forest areas (from Agnan et al, 2015 each study site (Asta et al, 2002;Fig. 2).…”

“…To determine the resistance or sensitivity of each lichen species to metal atmospheric pollution, we performed multivariate statistical analyses including the three diversity variables previously studied (lichen richness, lichen abundance, and Shannon index), the six ecological parameters mentioned above, the two bioindication indices (IAP and LDV), and metal bioaccumulation data measured in foliose lichen species (i.e., Xanthoria parietina, Parmelia sulcata, or Hypogymnia physodes) estimated using the sum of enrichment factors (EF) for 17 metals (Al, As, Cd, Co, Cr, Cs, Cu, Fe, Mn, Ni, Pb, Sb, Sn, Sr, Ti, V, and Zn; see Agnan et al (2015)). A PCA was then performed and the first two components (81% of the data variance) were represented (Fig.…”

“…However, organic pollutants also accumulated by lichens (Bajpai et al, 2010;Harmens et al, 2013), were not investigated here. By applying the frequencies of studied species to these indices, and comparing to the enrichment factors from Agnan et al (2015), we observed that the four more polluted sites (i.e., HET 54a, EPC 08, CHS 35, and PM 72) as evidenced by bioindication, obtained negative scores (i.e., dominated by resistant lichen species), while several less contaminated sites (e.g., EPC 63 and EPC 74) obtained positive values (i.e., dominated by sensitive lichen species).…”