387 For. Snow Landsc. Res. 80, 3: 387–390 (2006)
Calculation and mapping of critical loads of heavy metals for agricultural areas in the Crimea
Helene Evstafyeva*, Natalya Ovsyannikova, Irina Gluchenko and Sergey Karpenko Crimean State Medical University, bvd. Lenina 5/7, Simferopol, Ukraine, 95006.
helene@csmu.strace.net, nataly@csmu.strace.net, ir256@rambler.ru
* Corresponding author
Abstract
Critical loads of lead (Pb), cadmium (Cd) and mercury (Hg) were calculated and mapped with respect to drinking water protection in agricultural areas of the Crimea. In accordance with the ICP modelling and mapping manual, the calculation of critical loads was based on an effect-based approach, accounting for the possible negative influence of heavy metals on the biota at defined critical concentrations in the soil solution. The calculations of critical loads of Pb and Cd were based on a simplified mass balance for the metals in a 30 cm thick soil layer under the prerequisite that the airborne input of heavy metals into the agricultural ecosystem must not exceed the total fluxes of these metals from the system. For Hg a soil depth of 1 m was considered. As a large part of the agricultural areas in the Crimea is in the northern territories, where mainly wheat and other cereals are grown, the potential plant uptake of metals by these cultures was taken into account.
Based on the results of the calculations, the Crimea could be subdivided into sensitive regions with critical loads of up to 10.2 g ha–1a–1Pb, 3.16 g ha–1a–1Cd, and 1.02 g ha–1a–1Hg, and less sensitive regions with critical loads that are up to two times (Pb, Cd) or three times (Hg) lager.
Keywords: Pb, Cd, Hg, calculation and mapping of critical loads, mass-balance approach
1 Introduction
The intensive pollution of the environment is a risk factor for ecosystems and human health.
Different approaches are used to estimate such risks. One of them is the critical load con- cept. Determining the so-called critical load, which is defined as the maximum atmospheric load that causes no or tolerable damage to sensitive parts of the ecosystems, is one approach which can be used successfully for international negotiations on the reduction of atmospheric deposition of heavy metals on terrestrial ecosystems. This concept has been developed in Europe since the mid-1980s under the auspices of the Convention on Long-range Transboundary Air Pollution (SPRANGERet al. 2004).
The critical load is the maximum deposition rate of a pollutant that an ecosystem can tolerate during long time without any considerable risk to its condition and function. The calculation of critical loads narrows down to the determination of ecosystem boundaries, collection of basic data, modelling and mapping.
Critical load calculations are based on two main approaches: the effect-based and the steady-state mass-balance concept, with the mass-balance approach being used more often.
Therefore, the aim of this study was to calculate critical loads of Pb, Cd and Hg for agri - cultural areas in the Crimea using the mass-balance approach. Since the calculations were motivated by the protection of drinking water quality, the soil solution was chosen as the receptor.
388 Helene Evstafyeva et al.
2 Materials and methods
The calculations of critical loads of Pb and Cd were based on the simplified mass balance of metals in a 30 cm thick soil layer assuming that the airborne input of heavy metals into the agricultural ecosystem must not exceed the total fluxes of these metals from the system. In contrast to Pb and Cd, for the calculations of critical loads of Hg the entire soil column has to be considered. This was approximated by using a soil depth of 1m in the calculations for Hg.
Data for the calculations included a digital soil map (DRAGAN2003), a database of land use with cells of 10’ by 10’ (geographical minutes; VELDKAMPet al.1996). The results are processed for the 50 ×50 km sub grid of the EMEP (European Monitoring and Evaluation Program) net.
A large part of the agricultural areas in the Crimea is in the northern territories, where mainly wheat and other cereals are grown. Therefore, for these first calculations, we took into account only these cultures. As the sensitive ecosystem receptor we chose the soil solution. Critical loads were related to human health effects via drinking water quality, and thus, groundwater contamination.
Critical loads of Cd, Pb and Hg were calculated using the following equations:
CL(M) = Mu + Mle(crit),
where:CL(M) = critical load of a heavy metal M (Cd, Pb, Hg) (g ha–1a–1);
Mu = metal net uptake in the harvestable parts of plants (g ha–1a–1);
Mle(crit) = critical leaching flux of heavy metal from the considered soil layer (g ha–1a–1).
Reemission of deposited Hg occurs as an additional flux in mass balance models for Hg.
However, this flux could be ignored when calculating critical loads of Hg, because this reemission is treated as part of the atmospheric net deposition.
The metal plant uptake by crop biomass was estimated as follows:
Mu = fMu*Yha*[M]ha,
where:Mu = metal net uptake in harvestable parts of crop under critical load conditions (g ha–1a–1);
fMu = fraction of metal net uptake within the considered soil depth (0,3 m for Cd and Pb, 1 m for Hg); in our calculations fMu was assumed to be equal to 1; this means that the whole amount of metal found in the harvested biomass is due to immediate uptake of deposited metal.
Yha = yield of harvestable biomass (dry mass) (kg ha–1a–1);
[M]ha = metal content in the harvestable part of wheat (g kg–1);
Critical leaching flux of heavy metal from the considered soil layer Mle(crit) was estimated by the following equation:
Mle(crit)= 10*Qle*[M]ss(crit),
where:Qle = flux of drainage water leaching from the considered soil layer (m a–1);
[M]ss(crit) = critical total concentration of heavy metal in the soil solution (mg m–3).
The factor of 10 was used to convert the unit from mg m–2a–1to g ha–1a–1.
389 For. Snow Landsc. Res. 80, 3 (2006)
Data for calculations have been taken from different sources:
Qle was determined from the precipitation data for the Crimea (0.1–0.2 m a–1; The Autonomous Republic of Crimea 2002).
Yha have been taken from The Republic Statistic Committee (2002).
M[ha] metal contents of the harvestable parts of the plants were taken from SPRANGER
et al. (2004). The values for wheat were chosen: for Cd 0.08, for Pb 0.1, for Hg 0.01 mg kg–1. Yha – yield of harvestable biomass. For Crimea it equals 1500 to 2000 kg ha–1a–1.
[M]ss critical dissolved concentrations of Cd, Pb were taken also from SPRANGERet al.
(2004). The values according to WHO criteria for drinking water quality are for Cd 3, for Pb 10, for Hg 1 mg m–3.
4 Results and discussion
The following ranges of critical loads were calculated: for Pb 0–10.2 and 10.2 –20.2 g ha–1a–1, for Cd 0–3.16 and 3.16–6.16 g ha–1 a–1and for Hg 0–1.02 and 1.02–2.92 g ha–1a–1. These results allow distinguishing two groups of ecosystems based on two levels of critical loads for arable lands in the Crimea (Fig. 1). The higher ranges of critical loads indicate that the respective regions are less sensitive to HM pollution.
The results obtained for the Crimea were compared with the critical loads for other wheat growing regions in the southern part of Europe. For Cd, values of critical loads for the Crimea were the same as for the majority of regions in Europe (PRIPUTINA2002). Critical loads of Pb were higher in the Crimea than in the neighboring regions in Russia (PRIPUTINA
2002).
Fig. 1. Maps of critical loads of Pb (dark grey squares 0–10.2 g ha–1a–1, light grey squares 10.2–20.2 g ha–1a–1), Cd (dark grey squares 0–3.16 g ha–1a–1, light grey squares 3.16–6.16 g ha–1 a–1), and Hg (dark grey squares 0–1.02 g ha–1 a–1, light grey squares 1.02–2.92 g ha–1a–1) for drinking water protection in terrestrial ecosystems of the Crimea.
390 Helene Evstafyeva et al.
5 Conclusion
The calculated critical loads of heavy metals give a good first indication of the spatial varia - bility of ecosystem sensitivity to heavy metal pollution in the Crimea. However, the results are only a first step in using the approaches realized in the framework of the Convention on Long-range Transboundary Air Pollution.
More detailed analyses of ecosystem types and plant cultures are likely to improve the calculation of critical loads for EMEP cells not only for arable lands, but also for forests, for which preliminary data were already published (PRIPUTINA 2002). The next steps will include measuring the actual pollution with the given metals, comparing the pollution with the critical loads, mapping the population health status, and comparing the health status with exceedances of critical loads.
Acknowledgements
We thank our colleagues Priputina Irina, National Geochemistry institute, Puchino, Russia, Gudrun Schuetze, German National Focal Centre, Berlin, Germany and Jaap Slootweg, Netherlands Environmental Assesment Agency, The Netherlands. We thank Jörg Luster, Swiss Federal Institute for Forest, Snow and Landscape Research, WSL, Birmensdorf, Switzerland, for editing of the manuscript. We are even more pleased by the many friendships and rewarding pro- fessional relationships that have arisen because of this work.
6 References
The Republic Statistic Committee, 2002: Annual statistic bulletin of the Republic Statistic Committee, Crimea. 105 pp.
The Autonomous Republic of Crimea, 2002: Atlas “The Autonomous Republic of Crimea”, Crimea. 32 pp.
DRAGAN, N.A., 2003: Soil Map/Atlas “The Autonomous Republic of Crimea”. – Kiev-Simferopol.
VELDKAMP, J.G.; FABER, W.S.; VAN KATWIJK, V.F.; VELDE, R.J., 1996: Enhancements on the European land use – The National Institute for Public Health and the Environment (RIVM), Report No. 724001001. 70 pp.
SPRANGER, T.; LORENZ, U.; GREGOR, H.-D. (eds) 2004: Manual on Methodologies and Criteria for Modelling and Mapping Critical Loads and Levels and Air Pollution Effects, Risks and Trends. Federal Environmental Agency (Umweltbundesamt) Berlin, UBA-Texte 52/04.
PRIPUTINA, I., 2002: In: Proceedings 4-th Training-workshop on the calculation and mapping of critical loads for air pollutants relevant for the UN/ECE Convention on LRTAP in East and South East European countries. Sudak, Ukraine (Crimea).121 pp.
Revised version accepted November 6, 2006
