Heavy Metals: Transboundary Pollution of the Environment

EMEP Status Report 2/2005

I.Ilyin, O.Travnikov, W.Aas

ABSTRACT

In accordance with the 2005 Work-plan for the Implementation of the Convention [ECE/EB.AIR/83/Add.2] the Meteorological Synthesizing Centre - East (MSC-E) and the Chemical Coordinating Centre (CCC) continue research activities in the field of heavy metal atmospheric pollution assessment. The main objective of the work is to evaluate lead, cadmium and mercury pollution levels in Europe on the basis of measurement data and modelling results. Particular attention is paid to cooperation with the effect community on development of the critical loads approach, to support of activities on the review of the Protocol on Heavy Metals, and to the evaluation of the MSC-E heavy metal transport model in the framework of preparation to the model review.

At present the EMEP monitoring network contains 64 stations measuring lead and cadmium, of which 23 stations measure concentrations of these metals both in air and precipitation. There are 15 stations where at least one mercury form is measured. The monitoring stations, however, are non-uniformly distributed over European territory: they are mainly located in Central and Northern Europe. Annual analytical intercomparison of national laboratories treating measurements of heavy metals indicate an essential improvement of data quality during the period of 1995-2003, but still there is need for improvement for some countries.

Measured concentrations of Pb and Cd in air and precipitation show a significant decrease at most of the sites with long time series, a reduction more than 60% for both the elements since 1989. The lowest concentrations of lead, cadmium and mercury in 2003 were observed in Northern Scandinavia. In general, concentration levels increase towards the southeast of Europe.

National data on lead, cadmium and mercury emissions were submitted to the UN ECE Secretariat by 33 countries at least for one year of the period 1990-2003. However, only 14 of them submitted data for the whole period, whereas 11 counties did not submit any national data. Completeness of data on annual total emissions for the whole period is about 60%. Analysis of national data consistency has shown that anthropogenic emissions data officially submitted to the Convention cannot explain observed levels of lead and cadmium wet depositions in Europe. Based on observations of these metals in the EMEP monitoring network one can expect 2-3-fold underestimation of emission data in Europe.

Following the TFMM work-plan MSC-E has started preparation for the EMEP/TFMM Workshop on the review of the MSC-E models. As a first step towards model review MSC-E presented a detailed description of the regional HM transport model, model sensitivity study, uncertainty analyses and results of the five-year programme of model intercomparison study for mercury. The model sensitivity study demonstrated that the modelling results for such heavy metals as lead and cadmium are the most sensitive to anthropogenic emissions, natural emission and re-emission and to removal parameters. Sensitivity of mercury modelling results is highest to boundary concentration of gaseous elemental mercury. The intrinsic model uncertainty of lead and cadmium concentration in air, concentration in precipitation and total deposition are estimated as 43%, 40% and 33% respectively; the appropriate uncertainties for mercury are 19%, 53% and 39%.

Model estimates of the environment pollution with heavy metals in Europe were performed using the adjusted emission scenarios. According to the modelling results decrease of heavy metal depositions over the European territory on the whole in the period from 1990 to 2003 constituted 2.3 times for lead and cadmium and 1.6 times for mercury. Less essential decrease of depositions in comparison with the anthropogenic emission reduction is conditioned by the contribution of natural sources, re-emission as well as by global sources of heavy metals.

According to the modelling results deposition flux in different parts of Europe in 2003 can differ by more than an order of magnitude. High deposition levels are characteristic of Central and Southern Europe, the lowest levels - of Northern Europe. The transboundary transport plays an important role in pollution of most of European countries. Contribution of the external European anthropogenic sources to depositions ranges from 9 to 89% for lead, 7 - 83% for Cd and 2 - 55% for Hg. The contribution of the transboundary transport to depositions of heavy metals to the European Union varies from 3 to 10%.

Atmospheric depositions contribute significantly to heavy metal pollution of marginal seas. The highest mean deposition flux of lead and cadmium is obtained over the Black Sea, and of mercury - over the North and the Baltic Seas.

The MSC-E regional transport model used for the assessment of the pollution levels in Europe was evaluated against the available measurement data for the period 1990-2003. Modelling results based on the adjusted emission scenario were used in the model evaluation. The evaluation demonstrates satisfactory agreement with measurement data for all tree metals. A significant correlation of calculations with measurements was obtained for all metals and more 70% of modelling results differ from observations less than by 50% of the observed values.

The activities under the multi-stage project on the intercomparison of mercury transport models are complete. The third stage of the project was dedicated to the comparison of long-term modelling results with annual and monthly mean measurements of mercury concentration in the ambient air and atmospheric deposition fluxes. The comparison reveals that for the main calculated parameters both regional and hemispheric MSC-E models predict quite similar results. Both models do not occupy any extreme position among the other participating models.

In the framework of cooperation with the Working Group on Effects MSC-E performed calculations of relevant parameters of atmospheric inputs of heavy metals to ecosystems based both on official emission data and the adjusted emission scenario. Ecosystem-specific depositions of heavy metals in Europe were assessed and analysed.

Besides, the EMEP Centres were involved in cooperation with other subsidiary bodies to the Convention as well as international organizations and national programmes (European Commission, HELCOM). The main results were discussed at a number of scientific conferences, workshops and expert meetings.