Heavy metal and nitrogen concentrations in mosses are declining across Europe whilst some "hotspots" remain in 2010.

In recent decades, naturally growing mosses have been used successfully as biomonitors of atmospheric deposition of heavy metals and nitrogen. Since 1990, the European moss survey has been repeated at five-yearly intervals. In 2010, the lowest concentrations of metals and nitrogen in mosses were generally found in northern Europe, whereas the highest concentrations were observed in (south-)eastern Europe for metals and the central belt for nitrogen. Averaged across Europe, since 1990, the median concentration in mosses has declined the most for lead (77%), followed by vanadium (55%), cadmium (51%), chromium (43%), zinc (34%), nickel (33%), iron (27%), arsenic (21%, since 1995), mercury (14%, since 1995) and copper (11%). Between 2005 and 2010, the decline ranged from 6% for copper to 36% for lead; for nitrogen the decline was 5%. Despite the Europe-wide decline, no changes or increases have been observed between 2005 and 2010 in some (regions of) countries.

Country-specific correlations across Europe between modelled atmospheric cadmium and lead deposition and concentrations in mosses.

Previous analyses at the European scale have shown that cadmium and lead concentrations in mosses are primarily determined by the total deposition of these metals. Further analyses in the current study show that Spearman rank correlations between the concentration in mosses and the deposition modelled by the European Monitoring and Evaluation Programme (EMEP) are country and metal-specific. Significant positive correlations were found for about two thirds or more of the participating countries in 1990, 1995, 2000 and 2005 (except for Cd in 1990). Correlations were often not significant and sometimes negative in countries where mosses were only sampled in a relatively small number of EMEP grids. Correlations frequently improved when only data for EMEP grids with at least three moss sampling sites per grid were included. It was concluded that spatial patterns and temporal trends agree reasonably well between lead and cadmium concentrations in mosses and modelled atmospheric deposition.

Nitrogen concentrations in mosses indicate the spatial distribution of atmospheric nitrogen deposition in Europe.

In 2005/6, nearly 3000 moss samples from (semi-)natural location across 16 European countries were collected for nitrogen analysis. The lowest total nitrogen concentrations in mosses (<0.8%) were observed in northern Finland and northern UK. The highest concentrations (≥ 1.6%) were found in parts of Belgium, France, Germany, Slovakia, Slovenia and Bulgaria. The asymptotic relationship between the nitrogen concentrations in mosses and EMEP modelled nitrogen deposition (averaged per 50 km × 50 km grid) across Europe showed less scatter when there were at least five moss sampling sites per grid. Factors potentially contributing to the scatter are discussed. In Switzerland, a strong (r(2) = 0.91) linear relationship was found between the total nitrogen concentration in mosses and measured site-specific bulk nitrogen deposition rates. The total nitrogen concentrations in mosses complement deposition measurements, helping to identify areas in Europe at risk from high nitrogen deposition at a high spatial resolution.

Long-term changes in nitrogen deposition in Finland (1990-2006) monitored using the moss Hylocomium splendens.

Nitrogen deposition in Finland was investigated on the basis of the nitrogen concentration in the forest moss, Hylocomium splendens, collected during heavy metal moss surveys carried out in 1990, 1995, 2000, and 2005/06. Significant regional differences were found in the nitrogen concentrations in mosses. The concentrations were the highest in the southern part of the country in all the surveys, with a decreasing trend on moving northwards. The mean concentrations in the surveys were 1.07%, 1.00%, 0.89% and 0.92%. In general, the concentrations in mosses reflected nitrogen deposition at the level of the whole country. However, they did not correlate very well with the modelled nitrogen deposition because of the high local variation in the nitrogen concentration in H. splendens. One reason for the high variation was the effect of the structure of the tree stand on nitrogen concentrations in H. splendens.

Preliminary study of the use of terrestrial moss (Pleurozium schreberi) for biomonitoring traffic-related Pt and Rh deposition.

The use of Pt and Rh as active components in automobile catalytic converters has led to increasing concentrations of these elements in several natural matrices. Because of this, the suitability of the use of a terrestrial moss (Pleurozium schreberi) for the passive biomonitoring of traffic-related Pt and Rh deposition was studied. The moss samples collected from Finland in and around areas with heavy traffic had increased Pt and Rh concentrations, with maximum values of 12.2 and 4.5 ng g(-1), respectively. In addition, the concentrations of commonly used catalytic converter additives (Al, Ce, La, Y, and Zr) and some elements related to traffic or mineral dust (Cd, Cu, Fe, Hf, Pb, and Zn) were also measured to obtain more information about the sources of Pt and Rh. Multivariate principal component analysis and cluster analysis were applied for identification of the emission sources of the elements. The results indicated a common traffic-related source of Pt and Rh. However, the results also showed that Pt and Rh concentrations in mosses are increased only in areas located close to traffic lanes.

Atmospheric heavy metal deposition in Finland during 1985-2000 using mosses as bioindicators.

Heavy metal deposition and changes in the deposition patterns were investigated on the basis of surveys carried out in 1985, 1990, 1995 and 2000. The concentrations of 10 elements (Cd, Cr, Cu, Fe, Ni, Pb, Zn and V; and As and Hg since 1995) were determined on moss (Hylocomium splendens, Pleurozium schreberi) samples collected from the same permanent sample plots in each survey. The heavy metal concentrations, apart from those in southernmost Finland and close to a number of major emission sources, were relatively low. The mean concentrations of all the heavy metals decreased during the period covered by the surveys. The metals that showed the strongest decrease in concentration since 1985 were Pb (78%), V (70%) and Cd (67%). The concentrations of the other heavy metals decreased by 16-34%. The concentrations of Cr, Cu and Ni were clearly associated with local emission point sources and changes in emission levels. The concentrations of As and Hg, which were measured for the first time during the 1995 survey, decreased on the average by 26% and 10%, respectively.

Environmental specimen banking of nationwide biomonitoring samples in Finland.

An environmental specimen bank was built in 1994 by the Finnish Forest Research Institute. The main material stored is moss samples collected from the permanent nationwide sampling network every five years since 1985 for both national and international heavy metal surveys. Correspondingly there are nationwide biomonitoring samples of epiphytic lichen, pine bark and humus for surveying atmospheric heavy metal deposition. The bank is also storage of forest litter collected from 1960's onwards. This large material, tens of thousands of sorted samples, is valuable for indicating environmental changes of the forest ecosystem.