2 research outputs found
First thorough identification of factors associated with Cd, Hg and Pb concentrations in mosses sampled in the European Surveys 1990, 1995, 2000 and 2005
The aim of this study was, for the first time ever, to thoroughly identify the factors influencing Cd, Hg and Pb concentrations in mosses sampled within the framework of the European Heavy Metals in Mosses Surveys 1990–2005. These investigations can be seen as a follow up of a previous study where only the moss data recorded in the survey 2005 was included in the analysis (Schröder et al. 2010). The analyses of this investigation give a complete overview on the statistical association of Cd, Hg and Pb concentrations in mosses and sampling site-specific and regional characteristics, encompassing data from 4661 (1990), 7301 (1995), 6764 (2000) and 5600 (2005) sampling sites across Europe. From the many metals monitored in the European moss surveys, Cd, Hg and Pb were used as examples, since only for these three metals deposition measurements are being recorded in the framework of the European Monitoring and Evaluation Programme (EMEP). As exemplary case studies revealed that other factors besides atmospheric deposition of metals influence the element concentrations in mosses, the moss datasets of the above mentioned surveys were analysed by means of bivariate statistics and decision tree analysis in order to identify factors influencing metal bioaccumulation. In the analyses we used the metadata recorded during the sampling as well as additional geodata on, e.g., depositions, emissions and land use. Bivariate Spearman correlation analyses showed the highest correlations between Cd and Pb concentrations in mosses and EMEP modelled total deposition data (0.62 ≤ rs ≤ 0.73). For Hg the correlations with all the tested factors were considerably lower (e.g. total deposition r s ≤ 0.24). Decision tree analyses by means of Classification and Regression Trees (CART) identified the total deposition as the statistically most significant factor for the Cd and Pb concentrations in the mosses in all four monitoring campaigns. For Hg, the most significant factor in 1990 as identified by CART was the distance to the nearest Hg source recorded in the European Pollutant Emission Register, in 1995 and 2000 it was the analytical method, and in 2005 it was the sampled moss species. The strong correlations between the Cd and Pb concentrations in the mosses and the total deposition can be used to calculate deposition maps with a regression kriging approach on the basis of surface maps on the element concentrations in the mosse
Are cadmium, lead and mercury concentrations in mosses across Europe primarily determined by atmospheric deposition of these metals?
Purpose This study aimed at investigating correlations between
heavy metal concentrations in mosses and modelled deposition
values as well as other site-specific and regional characteristics
to determine which factors primarily affect cadmium, lead and
mercury concentrations in mosses. The resulting relationships
could potentially be used to enhance the spatial resolution of
heavy metal deposition maps across Europe.
Materials and methods Modelled heavy metal deposition
data and data on the concentration of heavy metals in naturally
growing mosses were integrated into a geographic information
system and analysed by means of bivariate rank
correlation analysis and multivariate decision trees. Modelled
deposition data were validated annually with deposition
measurements at up to 63 EMEP measurement stations within
the European Monitoring and Evaluation Programme
(EMEP), and mosses were collected at up to 7,000 sites at 5-
year intervals between 1990 and 2005.
Results and discussion Moderate to high correlations were
found between cadmium and lead concentrations in mosses and modelled atmospheric deposition of these metals:
Spearman rank correlation coefficients were between 0.62
and 0.67, and 0.67 and 0.73 for cadmium and lead,
respectively (p<0.001). Multivariate decision tree analyses
showed that cadmium and lead concentrations in mosses were primarily determined by the atmospheric deposition of
these metals, followed by emissions of the metals. Low to
very low correlations were observed between mercury
concentrations in mosses and modelled atmospheric deposition
of mercury. According to the multivariate analyses,
spatial variations of the mercury concentration in mosses
was primarily associated with the sampled moss species and
not with the modelled deposition, but regional differences
in the atmospheric chemistry of mercury and corresponding
interactions with the moss may also be involved.
Conclusions At least for cadmium and lead, concentrations
in mosses are a valuable tool in determining and mapping
the spatial variation in atmospheric deposition across
Europe at a high spatial resolution. For mercury, more
studies are needed to elucidate interactions of different
chemical species with the moss