Jarmo Poikolainen

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.

MODIS-NDVI-based mapping of the length of the growing season in northern Fennoscandia

Northern Fennoscandia is an ecologically heterogeneous region in the arctic/alpine-boreal transition area. Phenology data on birch from 13 stations and 16-day MODIS-NDVI composite satellite data with 250 m resolution for the period 2000 to 2006 were used to map the growing season. A new combined pixel-specific NDVI threshold and decision rule-based mapping method was developed to determine the onset and end of the growing season. A moderately high correlation was found between NDVI data and birch phenology data. The earliest onset of the growing season is found in the narrow strip of lowland between the mountains and the sea along the coast of northern Norway. The onset follows a clear gradient from lowland to mountain corresponding to the decreasing temperature gradient. In autumn, the yellowing of the vegetation shows a more heterogeneous pattern. The length of the growing season is between 100 and 130 days in 55% of the study area.

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.

On the abundance of epiphytic green algae in relation to the nitrogen concentrations of biomonitors and nitrogen deposition in Finland

Green algae have become considerably more abundant in the years 1985–1995 in Finland and their distribution area has expanded northwards. Green algae on conifers were most abundant in southern Finland where the nitrogen deposition is highest. Correlations were observed between the abundance of green algae and a modelled nitrogen and sulphur deposition as well as the nitrogen concentration of the biomonitors. The increased abundance of green algae in Finland may be caused by several concurrent changes which have taken place in the environment and which have all promoted the occurrence of green algae. A slight rise in mean annual temperature, the long-term stability of nitrogen deposition, and the clear fall in the amount of sulphur deposition have probably all increased the growth and abundance of green algae. At a local level, the differences in microclimate have also effect on the abundance of green algae and the microclimate varies, inter alia, by the nutrient-richness of the habitat, the predominant tree species, stand age and stand density.

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.

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.

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.

Heavy metal loading

The carpet-forming moss species, Hylocomium splendens and Pleurozium schreberi, are especially suitable for surveying heavy metal deposition because they obtain most of their nutrients directly from rainwater and particles deposited on their surfaces. The dense stands formed by these mosses also filter out particulate and aerosol material from large volumes of air, and are thus efficient at collecting air pollutants. The moss technique has been used in many regional and national heavy metal surveys (Anon. 1987, Steinnes et al 1993, Markert et al 1996, Ruhling 1994, Ruhling and Steines 1998).

Mapping of the epiphytic lichens on conifers in Finland in the years 1985–1986 and 1995

Abstract A systematic mapping of thirteen epiphytic lichen species on conifers was carried out in Finland at the first time in 1985–1986 and the second time in 1995. The aim of mapping work was to describe the regional distribution of the most common epiphytic lichens and to assess air quality based on the abundance of epiphytic lichens. All lichen species demonstrated increases in their abundance between the years 1985 and 1995. Scoliciosphorum chlorococcum , a species tolerant to air pollution, increased most in parts of the southern Finland where the nitrogen levels are relatively high. This indicate increased levels of nutrients in the forests. On the other hand, sensitive lichen species had become more common particularly in the central parts of the country, which is in agreement with decreasing sulphur deposition. The climate, tree species, stand age etc., however, mainly determining the distribution and the abundance of epiphytic lichens in Finland.

Estimation of the Long-range Transport of Mercury, Cadmium, and Lead to Northern Finland on the Basis of Moss Surveys

Abstract Nation-wide surveys of the accumulation of 10 heavy metals in mosses were carried out in Finland in 1985, 1990, 1995, and 2000. Separate investigations were carried out, on the basis of these surveys, into the atmospheric deposition of Hg, Cd, and Pb beyond the Arctic Circle in northern Finland. These metals are readily distributed in the form of long-range transboundary pollution, and particular concern has been raised about the transport and accumulation of these metals into Arctic areas. The Hg, Cd, and Pb concentrations in mosses in northern Finland were low. There was a clear decrease in Cd and Pb concentrations during the period 1985–2000. The Pb concentration decreased, on the average, from 8 to 2 μg g−1, and the Cd concentration from 0.3 to 0.1 μg g−1. Hg concentrations, which were analyzed in 1995 and 2000, decreased only slightly from 0.037 to 0.031 μg g−1. The slight decrease in Hg concentrations in northern Finland appears to reflect the decreasing Hg emissions and the high mobility of this metal. Factors leading to the decrease in Pb and Cd concentrations in mosses in northern Finland include a decrease in local emissions and a decrease in transboundary air pollution. The past two decades have been characterized by decreases in heavy metal emissions of throughout Europe. The greatest reductions have been in Pb emissions, due to the introduction of unleaded fuels.