Persistent Organic Pollutants in the Environment

EMEP Status Report 3/2004

S. Dutchak, V. Shatalov, E. Mantseva, O. Rozovskaya, N. Vulykh, M. Fedyunin, W. Aas, K. Breivik,
S. Mano

ABSTACT

In accordance with the EMEP work-plan for 2004 (ECE/EB.AIR/79/Add.2) Meteorological Synthesizing Centre - East (MSC-E) and Chemical Coordinating Centre (CCC) continued the investigations of the environmental pollution by persistent organic pollutants (POPs) on the basis of monitoring and emission data, and modelling results. In the current year the pollution of the environment by polycyclic aromatic hydrocarbons (PAHs), polychlorinated dibenzo-p-dioxins and dibenzofurans (PCDD/Fs), polychlorinated biphenyls (PCBs) and hexachlorobenzene (HCB) was studied. The outcome of the studies is summarized below.

At present the measurements of POP concentrations in the atmosphere and precipitation are performed by 13 EMEP monitoring sites. Most of these sites are located in Northern Europe. There is only one site in Central Europe located in the Czech Republic. In the southern and eastern parts of Europe there are no POP monitoring sites. To improve the spatial distribution of monitoring sites in Europe the new EMEP monitoring strategy has been developed. In accordance with the strategy it is expected to have about 20 sites evenly distributed over the EMEP region to measure POPs in both the atmosphere and precipitation ("Core sites level 2" - supersites). The uncertainties in the measurement data are partially evaluated on the basis of the laboratory intercomparison. The detailed description of measurement results and methodology being applied can be found in the EMEP/CCC Report [Aas and Breivik, 2004].

The official data on POP emissions (PAHs, PCDD/Fs, PCBs, HCB and g-HCH) for the period from 1990 to 2001 (at least for one year) were submitted by 32 Parties to the Convention. Data on other pollutants (Aldrin, Chlordane, Chlordecone, Dieldrin, Endrin, Heptachlor, Hexabromobiphenyl, Mirex, Toxaphene, DDT, PCP and SCCP) were submitted by 16 countries. It should be pointed out that in recent years the number of countries that submit official information on POP emissions and their spatial distribution is increasing.
According to the official data and expert estimates the emissions of all the pollutants of concern tend to decrease from 1990 to 2001. For example, emissions of PAHs (B[a]P and B[b]F) decreased by 25% and emissions of PCDD/Fs - more than 2 times.

In the current year the model assessment of the environmental pollution levels was performed for the three indicator PAHs: benzo[a]pyrene (B[a]P), benzo[b]fluoranthene (B[b]F) and benzo[k]fluoranthene (B[k]F). For these PAHs spatial distribution of the air pollution in 2001 was obtained. The deposition flux mean value amounted to about 10 g/km2/y. For part of the territory of Poland, Germany, the Czech Republic, Lithuania and Latvia, higher deposition fluxes (50-100 g/km2/y) are typical. PAH concentrations in the air of most of European countries do not exceed 1 ng/m3, but in polluted areas they reach 2-3 ng/m3.

The transboundary transport of PAHs between European countries was assessed by the example of B[a]P. It is demonstrated that the contribution of the external sources to air concentrations is significant and varies typically from 30 to 60%. The detailed information for each European country is available on the Internet (www.emep.int è www.msceast.org).

The trends in the environmental pollution by PAHs were analyzed by the example of B[b]F and B[k]F. It is demonstrated that the rate of the decrease of PAH contents in all the environmental compartments except soil mostly correlates with that of PAH emission reduction. In soil PAH concentrations decrease much more slowly due to the high persistence of PAHs in this compartment. As a consequence a significant fraction of the total PAH content in the environment is found in soil.

The assessment of the environmental pollution by dioxins/furans (PCDD/Fs) was based on simulation of each of 17 toxic congeners. The calculated levels of PCDD/F air concentrations (in TEQ units) in 2001 typical for most of European countries vary from 1 to 5 fg TEQ/m3. In the most polluted regions of Central Europe (Poland, the Czech Republic, Slovakia, Belgium and some areas of Germany) PCDD/F air concentrations reach 10-30 fg TEQ/m3 and more.

The calculations demonstrated that 60% of PCDD/F emissions deposit to the underlying surface. About 10% of the annual emissions deposit to the sea surface and about 50% - to the land surface. Due to the high persistence of PCDD/Fs in soil about 95% of the total PCDD/F content in the environment were contained in this compartment due to long-term accumulation (1970-2001). Against the background of the total emission decrease the re-emission flux from soil becomes significant. In 2001 the re-emission from soil in Europe amounted to 20% of the total European emissions.

By the example of PCDD/Fs, a preliminary assessment of the transboundary transport of substances with a significant fraction of gaseous phase in the atmosphere was performed. Similar to PAHs the contribution of the PCDD/F transboundary transport to the total air concentrations for European countries varies typically from 30 to 60%. In the calculation the contribution of the re-emission process to air concentrations and depositions was also taken into account.

A possibility to use model calculations to evaluate the results of various scenarios of emission reduction is demonstrated by the example of two conventional scenarios for PCDD/Fs for the period from 2000 to 2010.

The parameterization of the PCB long-range transport model was further refined and air pollution in the EMEP region with account of emission sources of the Northern Hemisphere was assessed. Particular emphasis was given to PCB toxic congeners. At present expert estimates of emissions in the Northern Hemisphere are available for two toxic congeners: PCB-105 and PCB-118. In addition to the toxic congeners, PCB-28 ("light" congener with low chlorination degree) as well as PCB-153 and PCB-180 ("heavy" congener with high chlorination degree) were considered. The calculations were made for the period from 1970 to 2000 to take into account the impact of PCB long-term accumulation in environmental compartments on air pollution. Based on the calculations the trends of concentrations of various PCB congeners in the main environmental compartments (atmosphere, soil and seawater) as well as the spatial distribution of air pollution by PCB toxic congeners were evaluated.

The POP intercontinental transport was investigated by the example of HCB. Due to its high persistence in the air (typical atmospheric half-life is about 1 year) HCB has the maximum potential for the long-range transport among the POPs involved. It leads to the fact that about 80% of the HCB annual emissions in Europe are transported outside the European region. The calculations demonstrate that about 35% of air pollution in Europe are accounted for by external emission sources, and the contribution of Asian sources to pollution of the Arctic is about 30%. Therefore in assessing HCB air pollution in Europe its intercontinental transport should necessarily be taken into account.

For the pollutant being considered the main media-accumulators were identified (soil for PAHs, PCDD/Fs, PCBs and seawater for HCB). The trends of pollution of the main environmental compartments were analyzed. The obtained results may be of interest for the risk assessment. Currently a method is being developed to assess POP depositions to various types of the underlying surface.

In 2004, MSC-E took part in the two meetings of the Task Force on POPs aimed at the preparation of technical input for the reviewing the Protocol on POPs. At the first meeting (the Hague, 1-3 March) MSC-E has presented the information on the EMEP activities regarding the assessment of the environmental pollution by POPs and the results of model approach to the evaluation of new substances according to the criteria of long-range transport potential and overall persistence. At the second meeting the Task Force agreed that "a small team led by Canada, and including Norway and EMEP/MSC-E will carry out work on gathering best available scientific information on effects of deposition of POPs". Besides, "the POPs Task Force requests EMEP to prepare a synthesis document on the best available country-submitted emissions data, including 1990 and more recent years". According to the request MSC-E will present the information on emissions and atmospheric transport of selected POPs, depositions and contamination levels of the environmental media prepared under EMEP.

In the current year MSC-E continued to evaluate the long-range transport potential and overall persistence of some new substances in terms of their possible inclusion into the Protocol on POPs. In addition to the substances previously considered the long-range transport potential and overall persistence were evaluated for b-endosulfan and polybrominated diphenyl ethers (PDE-28 congener). The selected substances were ranked by the relevant criteria and compared with the "benchmark substance". Benzo[a]pyrene being a regional-global boundary pollutant was selected as the "benchmark substance".

In 2004, MSC-E continued the work on the intercomparison study of POP multicompartment models together with national experts from the Parties to the Convention. Experts from Canada, the Czech Republic, Denmark, France, Germany, Japan, the Netherlands, Switzerland, the United Kingdom, the USA, as well as the representatives of MSC-E and CCC took part in this work. In the current year the first stage of the intercomparison was completed and the calculations within the second stage were begun. The results of the first stage are presented in the MSC-E Technical Report [Shatalov et al., 2004b]. The report on the second stage will be published in 2005.

To refine model estimates of environmental pollution the MSCE-POP model was modified. In the current year model descriptions of the atmospheric removal and degradation processes were refined. The data on concentration of particles in seawater were prepared to refine model description of the sedimentation processes.
The assessment of environmental pollution by POPs was carried out in cooperation with international organizations and programmes (AMAP, HELCOM, UNEP, WMO).

The main results were presented for the discussion and examination at the fifth meeting of the Task Force on Measurements and Modelling (Prague, Czech Republic, April 2004).