Heavy Metals: Transboundary Pollution of the Environment

MSC-E Technical Report 5/2003

I.Ilyin, O.Travnikov

ABSTRACT

The aim of this study is to provide European countries, with information on concentration and deposition fields, long-term pollution trends and transboundary fluxes of lead, cadmium and mercury in Europe. Because of global character of mercury pollution, its atmospheric transport and depositions had to be evaluated also using global or, at least, hemispherical modelling. As the first step in the assessment of mercury pollution of scales larger than Europe, pollution levels over the Northern Hemisphere were evaluated in this work. Particular attention has been paid to the pollution of the Arctic. This region is characterized highly vulnerable ecosystems. In addition to this, the Arctic is characterized by recently discovered phenomenon of mercury springtime depletion, which can lead to elevated levels of mercury depositions in this region.

Information presented in this study is obtained by means of atmospheric transport modelling. Two models developed at Meteorological Synthesising Centre East of EMEP programme were used to evaluate pollution levels: MSCE-HM (European scale) and MSCE-Hg-Hem (Northern Hemisphere). In order to validate calculated results, monitoring data collected in the frameworks of national programmes and prepared under methodical leadership of Chemical Coordinating Centre of EMEP were used.

The first Chapter of this report is devoted to the description of the atmospheric transport models used in simulation of pollution levels in Europe and in the Northern Hemisphere. Special attention has been paid to the description of the modifications of MSCE-HM and MSCE-Hg-Hem models. These modifications include adaptation of dry deposition module to the updated land-use database, introduction of gas-phase reaction of elemental mercury with chlorine, modification of spatial discretization along vertical in MSCE-HM model by accepting so-called s-p coordinate system. Results of pilot calculations using the regional-scale model with new vertical coordinate were discussed.

Chapter 2 deals with the description of the emission data used in the calculations. In the first part the information on emissions of lead, cadmium and mercury was prepared for each European country and for each year for the period from 1990 to 2001. Temporal changes of the emissions in Europe were analysed and countries with the largest relative and absolute emission reduction during the considered period were identified. Second part of the chapter contains information on mercury natural and anthropogenic emission over the Northern Hemisphere.

Assessment of heavy metal pollution levels in Europe is presented in Chapter 3. Calculation results of lead, cadmium and mercury long-term trends for 1990 - 2001 period are discussed in section 3.1. Relative reduction of depositions to each European country was compared with the corresponding emission reduction in the country and its countries - neighbours. The effect of transboundary transport on the rate of deposition change during 1990 - 2001 period was discussed.

Special attention was paid to the analysis of pollution levels in Europe in 2001. In section 3.2 spatial distributions of air concentrations and deposition fluxes in Europe are presented for lead, cadmium and mercury. Since pollution levels in European countries are caused to substantial extent by transboundary pollution, special analysis was paid to transboundary pollution estimates. For each country main transboundary sources were identified. In addition to this, depositions of lead, cadmium and mercury to various ecosystems were evaluated. Totally 15 ecosystem (land-use) types were considered in this study.

In section 3.3 of the third Chapter pilot estimates of atmospheric transport of second priority metals are presented. Second priority heavy metals include arsenic, chromium, nickel, zinc and copper. In this study air concentrations and deposition fluxes of nickel and chromium for 1996 were simulated and compared with the available monitoring data. Regions in Europe with highest and lowest pollution levels by these metals were determined.

The last section is devoted to validation of MSCE-HM model. The validation comprises comparison of modelled data with the available monitoring results, comparison of the results obtained by different models between each other and with measurement data, and analysis of the model uncertainty with regard to input data. Modelled and measured air concentrations and wet deposition fluxes were compared for 2001. In addition to this, model performance of long-term pollution trends was compared with the available monitoring data. First basic steps in model validation are given this section. Further directions of the model validation are formulated.

Chapter 4 is devoted to the model assessment of mercury atmospheric transport and depositions over the entire Northern Hemisphere. In the first section of the chapter spatial pattern of mercury concentrations in air and its depositions are analysed. The regions where the pollution levels are most significant have been identified.

Because of long life time mercury is characterised by global nature of its atmospheric transport. Therefore, once emitted, significant amount of mercury can reach receptors locating thousands km from the source. In this connection, evaluation of the intercontinental transport of mercury was carried out. The results of these simulations are presented in section 4.2 of this chapter. The information, presented in thus section, allows to realize the role of intercontinental transport in the formation of mercury pollution levels over Europe as well as the role of European sources in pollution of other continent.

Section 4.3 deals with the evaluation of the Arctic contamination by mercury. In particular, the role of mercury springtime depletion phenomenon in the pollution of the Arctic regions was evaluated. The last section is devoted to validation of the hemispheric model. Modelled values of air concentrations and wet deposition fluxes were compared with relevant observed values. Particular attention was paid to the analysis of the model ability to reproduce background mercury air concentrations and behaviour of mercury concentrations during mercury spring-time depletion evens.

The last section is devoted to validation of MSCE-HM model. The validation comprises comparison of modelled data with the available monitoring results, comparison of the results obtained by different models between each other and with measurement data, and analysis of the model uncertainty with regard to input data. Modelled and measured air concentrations and wet deposition fluxes were compared for 2001. In addition to this, model performance of long-term pollution trends was compared with the available monitoring data. First basic steps in model validation are given this section. Further directions of the model validation are formulated.

Chapter 4 is devoted to the model assessment of mercury atmospheric transport and depositions over the entire Northern Hemisphere. In the first section of the chapter spatial pattern of mercury concentrations in air and its depositions are analysed. The regions where the pollution levels are most significant have been identified.
Because of long life time mercury is characterised by global nature of its atmospheric transport. Therefore, once emitted, significant amount of mercury can reach receptors locating thousands km from the source. In this connection, evaluation of the intercontinental transport of mercury was carried out. The results of these simulations are presented in section 4.2 of this chapter. The information, presented in thus section, allows to realize the role of intercontinental transport in the formation of mercury pollution levels over Europe as well as the role of European sources in pollution of other continent.

Section 4.3 deals with the evaluation of the Arctic contamination by mercury. In particular, the role of mercury springtime depletion phenomenon in the pollution of the Arctic regions was evaluated. The last section is devoted to validation of the hemispheric model. Modelled values of air concentrations and wet deposition fluxes were compared with relevant observed values. Particular attention was paid to the analysis of the model ability to reproduce background mercury air concentrations and behaviour of mercury concentrations during mercury spring-time depletion evens.


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