Abstract

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DOI: http://dx.doi.org/10.1065/ehs2004.06.011

Goal, Scope and Background. The Heavy Metals in Mosses Survey provides data on accumulation of, at least As, Cd, Cu, Fe, Hg, Ni, Pb, V and Zn in naturally growing mosses throughout Europe. Germany took part in the monitoring campaigns of 1990, 1995 and 2000 under leadership of the Federal Agency for Environmental Protection. The article concentrates on two methodical aspects of the statistical data analysis: spatial estimation of sampling data and aggregation of element specific data to three metal accumulation indicators.

Main Features. The sampling and analysis procedures are outlined, and the analytical results are summarized by means of descriptive statistics. Then, the focus is on the geostatistical analysis and transformation of point data to areal information by example of the German monitoring data. The data is aggregated to three spatially and temporally differentiated indicators of metal accumulation.

Results and Discussion. The 2000 moss monitoring reveals low metal concentrations in most European countries. Those in the west and north of Europe tended to have localized high concentrations, while the countries in the east tended to have extensive areas with such high concentrations. From 1990 to 2000, a decrease in the concentrations of most metals took place. Mapping concentrations as dot maps delivers a detailed picture of the spatial structure of the accumulation of the metals measured. This information, detailed with respect to metal species and space, is supplementarily generalized spatially by means of geostatistical estimation. Finally, three indicators of metal accumulation are calculated. One of them is based on percentiles of sample data, the other is extracted by means of cluster analysis from the spatially estimated data. The advantages and disadvantages of these indicators are discussed.

Conclusions. Moss monitoring is an effective and cheap method for the detection of temporal and spatial trends in metal accumulation. The comparison of the 1990, 1995 and 2000 monitoring campaigns reveals a European-wide decline in metal concentrations, especially of arsenic and cadmium. In 2000 there was a clear east / west decrease in heavy metal concentration in mosses, related particularly to industry. In areas without contemporary industries, hot spots of high concentrations are due to former industrial sites and historic mines.

Recommendations and Outlook. The spatial and temporal trends of metal accumulation in mosses should be compared with deposition data. The influences of moss species and analytical techniques on the measured concentrations should be investigated further. Finally, a synoptic cluster-analytical and geostatistical assessment of the monitoring campaigns of 1990, 1995 and 2000 would be valuable, detailing the results by additional empirical and location describing information (e.g. moss species, ecoregions, site and species-specific variability of metal accumulation), as well as the optimization of indicator building through the testing of multivariate statistical regression models.