Heavy metals in Estonian coniferous forests
Date
2017-10-27
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Abstract
Töö peamiseks eesmärgiks oli teha kokkuvõte keskkonnaseire riikliku programmi raames kogutud raskmetallide andmestiku baasil meie looduslike okasmetsade – raskmetallidega saastatuse tasemest. Seireandmestik võimaldas analüüsida kuut erinevat raskmetalli: Zn, Cu, Cr, Ni, Cd ja Pb. Peamiselt kasutati metsaseire ja kompleksseire raames kogutud raskmetallide andmeid, kuid ka raskmetallide andmestikku sammaldes ning kohalike sademete seire võrgustiku andmebaasi. Erinevate andmete kombineerimine andis ülevaate raskmetallide kontsentratsioonidest, nende liikumisest okasmetsa erinevate osade vahel (muld, peenjuured, elusokkad, varis), peetumisest ja akumuleerumisest okasmetsa mulla orgaanilises osas. Iseloomustati ka raskmetallide sadestumise ja akumuleerumise territoriaalset varieerumist.
Raskemetallide peamisteks allikateks Eestis on olnud ja on ka praegusel hetkel paiksed antropogeensed saasteallikad: põlevkivil töötavad elektrijaamad, põlevkiviõli-, tsemendi- ning keemiatööstus, mis asuvad Kirde-Eesti tööstuspiirkonnas (Kohv et al., 2002). Alates 1990. aastatest on raskmetallide heitkogused Eestis märkimisväärselt vähenenud. Suurim langus emissioonides toimus 1990. aastate alguses seoses elektritootmise vähenemisega. Jätkuv raskmetallide emissioonide vähendamine pärast aastat 2000 on saavutatud põlevkivitööstuse moderniseerimise, rahvusvaheliste keskkonnaalaste eeskirjade rakendamisega ning investeeringutega puhastesse tehnoloogiatesse (Treier et al., 2008; Statistikaamet, 2017).
Uuringu tulemusel leiti, et Eesti erinevates piirkondades on raskmetallide sadenemine ja sellega seotud varude osas erinevusi, seda just mulla orgaanilisse osasse kogunenud varudes. Raskmetallide suurimad varud oli mulla ülemises orgaanilises kihis, kuid raskmetallide kontsentratsioonid olid tihti kõrgemad peenjuures ja nendega seotud mütseelis. Mulla orgaanilistesse kihtidesse akumuleerunud raskmetallid satuvad uuesti ringlusesse peenjuurte abil, kus omastatud raskmetalllid suures osas ka peetuvad (eriti Pb Cd ja Cr). Seetõttu aeglustavad peenjuured raskmetallide liikumist mulla alumistesse kihtidesse ning pikendavad kõdukihi puhastumist raskmetallidest. Depositsioon on aga endiselt oluline raskmetallide allikas metsaökosüsteemis.
The aim of this thesis was to get an overview of heavy metal pollution in natural coniferous ecosystems based on the data of environmental monitoring programmes. Therefore six different heavy metals (Zn, Cu, Cr, Ni, Cd, and Pb) in Estonian coniferous ecosystems were investigated. Samples of different media were collected under the framework of international and local monitoring programmes (ICP Forests, ICP IM, ICP Vegetation, and data from national precipitation network stations) to understand the differences in heavy metal concentrations and accumulation in different parts of the coniferous ecosystem. In addition, the concentrations, accumulation, and fluxes of heavy metals per territorial differences in heavy metal depositions and accumulation were estimated. The sharp decrease in heavy metal depositions during the 1990s were followed by slower decreasing trends over 2003–2013, and heavy metal depositions levels are now considered modest. High concentrations of heavy metals in fine roots, and significant correlations between heavy metal concentrations in soil organic horizons and fine roots, indicate that heavy metals accumulated in soil organic layers during the peak oil-shale-usage period. In some cases, these heavy metals might still be transported to the coniferous trees. High accumulation of heavy metals—especially Pb—was observed in fine roots and thereby the heavy metals’ stay in the ecosystem is prolonged, and the soil purification processes of upper soil organic layers delayed. The highest stores of heavy metals in the studied media were found in the soil organic layers. Territorial differences in current heavy metal deposition and accumulated storages of heavy metals occur in Estonia, especially regarding past depositions now accumulated in the older parts of soil organic horizons. Combining the results of international monitoring programmes with local datasets gave a unique insight into heavy metals in Estonian coniferous ecosystems both currently and in the past. This kind of scientific analysis of environmental data helps to form an overview of the current environmental status of forests and predict the effects of previously accumulated pollutants under changing environmental conditions.
The aim of this thesis was to get an overview of heavy metal pollution in natural coniferous ecosystems based on the data of environmental monitoring programmes. Therefore six different heavy metals (Zn, Cu, Cr, Ni, Cd, and Pb) in Estonian coniferous ecosystems were investigated. Samples of different media were collected under the framework of international and local monitoring programmes (ICP Forests, ICP IM, ICP Vegetation, and data from national precipitation network stations) to understand the differences in heavy metal concentrations and accumulation in different parts of the coniferous ecosystem. In addition, the concentrations, accumulation, and fluxes of heavy metals per territorial differences in heavy metal depositions and accumulation were estimated. The sharp decrease in heavy metal depositions during the 1990s were followed by slower decreasing trends over 2003–2013, and heavy metal depositions levels are now considered modest. High concentrations of heavy metals in fine roots, and significant correlations between heavy metal concentrations in soil organic horizons and fine roots, indicate that heavy metals accumulated in soil organic layers during the peak oil-shale-usage period. In some cases, these heavy metals might still be transported to the coniferous trees. High accumulation of heavy metals—especially Pb—was observed in fine roots and thereby the heavy metals’ stay in the ecosystem is prolonged, and the soil purification processes of upper soil organic layers delayed. The highest stores of heavy metals in the studied media were found in the soil organic layers. Territorial differences in current heavy metal deposition and accumulated storages of heavy metals occur in Estonia, especially regarding past depositions now accumulated in the older parts of soil organic horizons. Combining the results of international monitoring programmes with local datasets gave a unique insight into heavy metals in Estonian coniferous ecosystems both currently and in the past. This kind of scientific analysis of environmental data helps to form an overview of the current environmental status of forests and predict the effects of previously accumulated pollutants under changing environmental conditions.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone
Keywords
raskmetallisaaste, okasmetsad, keskkonnaseire, Eesti, heavy metals pollution, coniferous forests, environment monitoring, Estonia