Long term assessment of heavy metals in the atmosphere of background regions of Russia and other NIS countries.

 

Sergey A. Gromov*, Veronika A. Ginzburg, Sergey G. Paramonov

Laboratory of Integrated Monitoring, Institute of Geography RAS, Moscow, 107258 Russia
E-mail:  <Sergey.Gromov@mtu-net.ru>

Larisa V. Burtseva

Institute of Global Climate and Ecology, Moscow, 107258 Russia

Nadezda A. Bunina

Hydrometobservatory, Moscow State University, Moscow, 118899 Russia

 

Abstract

 

The overview of the integrated background monitoring network (IBMoN) in Russia are presented including measurement programs, sampling, analysis and data handling for atmospheric heavy metals. The results of statistical calculations carried out for long-term measurements of their concentrations in air and precipitation are presented for period of 1982-1996. Long-term changes were evaluated for atmospheric lead, cadmium and mercury over the former USSR territory based on their annual and seasonal averages. The evident decreasing of their airborne content levels was determined for the most of Russian regions started the beginning of 1990s. The simple appropriate models to evaluate removal from the atmosphere were used taking into account the spatial peculiarities of both emissions and land-cover. Dry and wet depositions of lead, cadmium and mercury were calculated for annual period of IBMoN operating with mostly complete data both spatially and temporally followed by comparison with ones prepared by EMEP/MSC-E for Russian EMEP region.

 

Introduction

 

Regional or global contents of heavy metals in the atmosphere were measured over the territory of Russia and other NIS by Integrated Background Monitoring Network (IBMoN) carried out a monitoring of environmental pollution in remote areas. This network was established at the beginning of 1980s with a special measurement program closely correlated with principles of the UNEP Global Environmental Monitoring System (GEMS UNEP) and provided measurements were used to detect global and regional trends in environmental pollution. Locations of IBMoN stations together with other background atmospheric networks are presented in the map showed the highest development of ones over the former USSR before 1991 (Fig.1). The most of Russian IBMoN stations are operating until now as well as other stations in Central Asia countries carrying out their measurements under the CIS Intergovernmental Agreement on Hydrometeorology and Environmental Monitoring.

The measurement data on concentration of lead, cadmium and mercury in air and precipitation were used in this study for period of 1982-1996.

 

Methods

 

The measurement program comprised daily air sampling of both aerosols (of lead and cadmium) and vapour mercury. Aerosol particles were taken with Petryanov FPA-15 filters by up to 1000 m3/day capacity of air volume permeating. Silver sorbents in glass absorbing tubes were used for collecting of vaporous (gaseous) mercury with air flow rate of 1.5-2.5 l/min. Bulk precipitation samples of 10-days or monthly collecting are taken through all seasons as a liquid ones. Moreover, daily fall-out was collected at single IBMoN site for 1978-1985.

Fig.1. Background atmospheric networks in the former USSR for 1990.

 

Lead and cadmium were measured by means of atom absorption spectrophotometry (AAS) with flame and flameless atomisation. Atom absorption method of “cold vapour” was applied to detect mercury content in samples. Summary error of individual measurements for lead and cadmium concentrations in air (within ranges of 0.4-100 ng/m3 and 0.01-5.0 ng/m3 respectively) and in precipitation (within ranges of 0.1-20 and 0.02-2.0 mg/l respectively) does not exceed +25%. The same value was determined for error of mercury concentration in air and precipitation within ranges of 2-70 ng/m3 and 0.05-10 mg/l respectively.

The information on heavy metal concentrations in air and precipitation was taken form IGCE's Database "Background monitoring". Calculated weighted means and other statistics are presented for all of monitoring stations in Table 2.Standard general statistical methods were used for evaluation of data. Trend investigation was based on annual and seasonal averages of concentrations. Dry depositions of heavy metals were calculated with help of simple empirical model using air pollutant concentrations and dry deposition velocity. Wet depositions were evaluated by the way of extension weighted concentration in fall-out at monitoring stations over the regions with same precipitation regime and industrial development.

 

Result and Discussion

 

Background concentrations of heavy metals in air are corresponded to a log-normal frequency distribution both throughout the year and in different seasons. For 95% of all measurements over the European Russian, lead and cadmium concentrations were below 22.4 and 2.33 ng/m3 respectively. Over Eastern Siberia, these values were 5.71 and 0.30 ng/m3. As a contrast with above data limits the most of mercury concentrations in air were less than 16 ng/m3 over the whole Russia. The highest mercury vapour contents in the atmosphere were detected in mountain regions of Central Asia – the boundary of 95% was determined at 56 ng/m3. Multiyear mean geometric values of heavy metals in air for different Russian regions as well as several CIS countries presented in Fig.2 according to general west-east direction.


Fig.2. Annual mean geometric concentrations of heavy metals in air over FSU territory.

 


The long-term changes of atmospheric heavy metals showed different features for lead and cadmium, and from other side, for mercury. According to long-term measurements the general tendency was to decrease lead and cadmium aerosol content in the air. However this feature was not evident for 1980-1988 for most of regions and the significant fall of concentration was appeared after 1988 everywhere of the former USSR regions (Fig.3). The trends of mercury in the atmosphere were not so significant and the alike conclusions could not be done based on simple statistic evaluations.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


Fig. 3. Multi-year trends of lead (mean seasonal values) for European stations

(02, 04), Caucasus (03) and Western Siberia (01), in ng/m3.

 

More frequent values of lead concentration in fall-out were in the range of 3-8 mg/l. Maximums of measurements were greater than minimum as factor of 15-20. Mean annual concentrations of cadmium were equal 0.2-1.7 mg/l with maximum values in Central Russia. The mercury concentrations in Russia were in the wider range of values ‑ from 0.2 to 4.1 mg/l.

The variations of heavy metals in precipitation are presented as generalised values for parts of Russia (Fig. 4). The evident decreasing of cadmium in precipitation was recorded for Asian part of Russia. In opposite the 40% growth was detected in southern part of European Russia during last 10 years. A similar increasing was recorded for mercury in precipitation from the beginning of 1990s in mentioned region and in Asia - up to twice of magnitude.

 

Fig. 4. Multi-year changes of annual heavy metal concentrations, mg/l.

Spatial differences of multi-year annual wet deposition of lead over the former USSR with general direction from west to east is presented in Fig. 5. Based of data for 20 regions distinguished over the former USSR territory on precipitation amounts the annual wet deposition fluxes were evaluated (in mg/m3) as 0.3-8.8 (mean is 2.7) of lead, 0.03-0.5 (0.16) of cadmium and 0.03-1.3 (mean is 0.24) of mercury.

 

Fig. 5. Spatial differences of seasonal wet deposition in different regions of CIS, mg/m2

 

Dry deposition of metals varied considerably in space both in summer and winter. Monthly lead depositions were 3-120 mg/m2 in summer and 1.0-45 in winter depends on both Pb air concentrations and surface conditions as well as atmospheric turbulence. The fluxes of Hg were not so variable although they differed in some parts of Russia significantly (Fig. 6).

 

Fig. 6. Monthly dry deposition of mercury and lead for 1990 at station 01, 04 and 05, mg/m2.

 

Annual dry depositions onto Russian territory calculated for 1990 were 2.0-2.6 thousand tons of lead, 60-78 tons of cadmium and 0.96-1.2 thousand tons of mercury whereas total (wet and dry) values (in thousands tons): 43.3 of lead, 2.7 of cadmium and 4.1 of mercury. These data were changed from year to year. Based on estimation for 1990 the less values of annual deposition for Russia were evaluated for lead and mercury - 27.6 and 2.3 thousands tons respectively with the similar value for cadmium (2.8 thousand tons).