THE CONTENT OF RISK ELEMENTS IN AGRICULTU RAL SOILS IN THE IMMISSION-LOADED TERRITORY OF NORTH-WESTERN PART OF THE CZECH-REPUBLIC

In agricultural soil in immission-loaded territory of the north-wester n part of the Czech Republic, which included 38 localities in 13 distr icts (Tab. I, Fig. 1), the degree and area of soil contamination by ri sk elements Cd, Pb, Cr, Ni, Zn, Cu, Co, As and Hg were determined in a n extract of 2M HNO3 under cold annually in the years 1991 to 1993. Co ntamination in most cases did not attain the limits of maximum-admissi ble releasable contents in soils (Tab. II) and at the same time no mar ked annual fluctuations in the content of elements during the period o f investigations were recorded. Figs 1 to 4 show sites where backgroun d values were exceeded for lighter-medium, medium-heavy to heavy subst rates. Tab. III gives ranges of measured concentrations of elements, e specially with regard to the definition of percentage of soils not exc eeding background values and soils exceeding the limits of contaminati ons. The highest area distribution of loaded soils were found out in A s, Ni, Cd and Co. The contamination by Zn and Cr was lower. Limits of contamination were not exceeded in the other elements. The results acq uired by us are in congruency with similar measurements conducted by P odlesakova et al. (1994) in the part of the same territory. The backgr ound values were much exceeded in As (55.3%). Raised values were measu red in the regions Sokolov, Karlovy Vary, Louny, Teplice, Usti nad Lab em, Kladno (Fig. 4). Background values above 4.1 ppm were found out in 21.1% (Tab. III). The above elements were found in the regions which are close to prevailing flowing and are continuously and significantly affected by load of risk elements. Increased Ni values were in the re gions Usti nad Labem, Teplice, Litomerice and Chomutov (Fig. 2). Backg round values above 12.1 ppm were found out in 13.5% of cases. Regions of higher Cd-load are Usti nad Labem and Teplice and impinges on the e astern part of the Most region. Other regions with higher incidence of this element are eastern part of the Louny region and adjacent north- western part of the Kladno region (Fig. 1). Limits of contamination we re exceeded in the districts Usti nad Labem and Karlovy Vary (by 5.3%) . High load above the level of background values in Co was ascertained in the districts Teplice, Usti nad Labem and Karlovy Vary (Fig. 4). L imits were exceeded in two cases (5.3%). Excess of background values i n other elements (Pb, Cr, Zn, Cu and HE) were point-found out. The res ults ascertained documented in Tab. III show that, except for the As c ontent, the prevailing part of measured values falls into the category below the background values (52.6 to 92.1%). More distinct excess of the contamination limit indicating increased inputs was recorded only in As (21.1%) and Ni (13.2%). Despite the above findings, the fact tha t cultivated plants have different capacity of accumulation of undesir able elements and the content of their biomass can be affected by fall s-out cannot be omitted. The risk of increased contents is just on soi ls with their increased contents (Tlustos et al., 1995).