Comparing early twentieth century and present-day atmospheric pollution in SW France: A story of lichens

Abstract

Lichens have long been known to be good indicators of air quality and atmospheric deposition. Xanthoria parietina was selected to investigate past (sourced from a herbarium) and present-day trace metal pollution in four sites from South-West France (close to Albi). Enrichment factors, relationships between elements and hierarchical classification indicated that the atmosphere was mainly impacted by coal combustion (as shown by As, Pb or Cd contamination) during the early twentieth century, whereas more recently, another mixture of pollutants (e.g. Sb, Sn, Pb and Cu) from local factories and car traffic has emerged. The Rare Earth Elements (REE) and other lithogenic elements indicated a higher dust content in the atmosphere in the early twentieth century and a specific lithological local signature. In addition to long-range atmospheric transport, local urban emissions had a strong impact on trace element contamination registered in lichens, particularly for contemporary data.

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

“…All cleaning procedures used highpurity water (18.2 MΩ cm). Approximately 100 mg of powdered sample was digested using 0.5 mL of 68% HNO 3 and 0.5 mL of 50% HF at 90°C in a Savillex (Teflon bottle) for 48 h (Agnan et al, 2013). After evaporation, 1 mL of H 2 O 2 was added and evaporated at 50°C, and 1 mL of 68% HNO 3 was added for 48 h at 90°C.…”

“…Each site covered an area of 25,000 m 2 including 3-5 sub-sampling sites. This protocol attempted to limit local influence in order to integrate a global and homogeneous signal (Agnan et al, 2013). The lichen sampling was performed on all sides of the tree trunks at a height of approximately 1.5 m to prevent any soil contamination (Bargagli and Nimis, 2002).…”

Elemental compositions of lichens from Duolun County, Inner Mongolia, China: Origin, road effect and species difference

“…Fe and Ti are highly positively correlated in all lichen and SS data sets (all r > 0.979, p < 0.001), and the Fe:Ti ratios are not significantly different between lichens and SS (Table 1). Because a good positive correlation between lichen elements can be evidence of a common origin 11, 32, 34 , the intimate correlations between G3 metals and between G4 elements in lichens is further evidence of terrigenous origin, although these correlations are also a reflection of similar spatial patterns (Figs 2 and 3). Actually, most G3 and G4 elements, such as Fe, K and Ti, are regarded as of crustal origin in Inner Mongolia 32 , even in the Taihang Mountains that experiences heavy air pollution 31, 33, 34 .…”

“…The poor correlation of Cu with terrigenous elements (G3 and G4 elements; Figs 2 and 3) may be partly explained by the fact that Cu is often associated with industrial activities and road traffic 3, 11 . A high EF SS of Cu in lichens is expected because samples were collected within 400 m off the road.…”

Impact of nickel mining in New Caledonia assessed by compositional data analysis of lichens

“…all metal concentrations are divided, for instance, by those of Ti, the normalizing element used in the following, Goix et al 2013; Monna et al 2012). This can be viewed as the first step towards the so-called enrichment factor (EF) calculation, which aims at detecting, in combination with other tools, which elements are enriched in relation to local soils or earth crust (Agnan et al 2013; Aničić et al 2009; Aslan et al 2012; Cloquet et al 2015). The only difference is that there is no final normalization by local reference values or, more simply, by those of the upper continental crust (e.g.…”