Temporal trends and spatial patterns of heavy metal concentrations in mosses in Bulgaria and Switzerland: 1990–2005

Owing to their ability to accumulate heavy metals, mosses are especially suitable to monitor heavy metal airborne pollution. In Europe, starting in 1990 within the framework of UNECE ICP-Vegetation, the monitoring of background heavy metal deposition based on concentrations found in mosses were performed every five years in Switzerland, and, since 1995 also Bulgaria. Here we compare spatial and temporal trends of heavy metal depositions in these two countries and we assess to what extent a large scale European deposition model (MSCE-HM model) can be applied on these two countries.Highly significant differences in concentrations in mosses between the two countries were found for Cd, Cu, Ni, V, Cr, Fe, Pb. For Zn the differences were less clear, but still significant in 2000 and 2005. In Bulgaria, with the exception of Cr, heavy metal concentrations decreased between 1995 and 2005 (−14% to −29%). In Switzerland, Cd (−38%), Pb (−63%) and V (−23%) showed the strongest decrease between 1995 and 2005. For Fe, Ni and Zn no or only small concentration changes were found, whereas a considerable rise was recorded for Cr (+65%) and Cu (+15%). In comparison to median heavy metal concentrations in Europe, concentrations in Bulgaria were nearly always higher, while concentrations in Switzerland were always lower. For both Pb and Cd, relationships between modelled and moss-derived values for all of the years were highly significant, but explained variances were rather low. Overall, relationships between moss-derived depositions and modelled depositions were rather close to a 1:1-relationship in Switzerland. In Bulgaria the modelled depositions were considerably lower than the moss-derived depositions.Although deposition levels in Bulgaria also decreased, heavy metal concentrations in mosses were still high. In contrast to Switzerland, Bulgaria has a strong non-ferrous and ferrous heavy industry. New technologies must be implemented in order to reduce deposition levels in Bulgaria. Continuing the moss monitoring is crucial for future evaluations of environmental measures.

Research highlights► We compare the atmospheric accumulation of metals in mosses between Bulgaria (BG) and Switzerland (CH). ► Spatial and temporal trends between 1990 and 2005 were surveyed. ► Significantly higher concentrations were found in BG for Cd, Cu, Ni, V, Cr, Fe and Pb. ► In BG most metal concentrations decreased between 2000 and 2005, in CH between 1990 and 1995. ► EMEP-modelled Pb deposition fitted well to moss-derived in CH, but not in BG.