Heavy metals contamination of agricultural crops and soils was investigated during 1987 to 1992 in five selected regions of the Czech Republic: Chomutov, Sokolov, Liberec, Zatec (industrial immissions polluted regions, the Northern Bohemia) and Zamberk (control region). The main cause of air and environmental pollution and acid precipitation in the Northern Bohemia is action of a power engineering station, which includes an extraction and combustion of low-quality brown coal with a high content of sulphur (5 to 15%) and other pollutants, including heavy metals. A monitoring of heavy metals environmental pollution in immission-exposed regions was a main aim of this research work. The monitoring network included nearly 200 individual points situated in five above-mentioned regions. Eight important elements from the heavy metals (Cd, Pb, Hg, As, Co, Cr, Ni and Zn) were tested. Agrolandscapes, soils and crops typical for Bohemia were investigated. Ordinary sampling and analytical methods for determination of heavy metals content in the agricultural soils and crops were used. The examination method of heavy metals contamination was based on the comparison of heavy metals concentration in crops and soils with pollutants limiting values from the Czech state standards. Generally, the heavy metals contamination of agricultural soils in five selected regions of the Czech Republic in accordance with exceeding of limiting value was sufficiently low. Only 87 soil samples of the total number 1,187 of analyzed samples (7.3%) were contaminated in accordance with indicating value. The main soil pollutants were Cr (44 occurrences of contamination), Cd (31), Pb (29), Ni (14) and Zn (10). The As had not an indicating value in the Czech state standards and because one did not value. The highest heavy metals contamination was in Zatec, Sokolov and Chomutov regions (8 to 12% occurrence) and lowest was in Liberec and Zamberk (< 1%). In accordance with maximum permissible concentration of heavy metals in soils, which are much higher in comparison with indicating limiting value, the heavy metals contamination of soils was insignificant (30 occurrences of-total 1,187 samples or 2.5%). Only As (29 occurrences of contamination) and Pb (2 occurrences) participated in exceeding of maximum permissible concentration. This contamination was in three regions only (Sokolov, Chomutov, Zatec). No heavy metals soil contamination above maximum permissible concentration was discovered in Liberec and Zatec regions. Absolutely different situation was observed in accordance with heavy metals contamination of agricultural crops; 137 plant samples of total 2,258 tested samples or 6.1% were contaminated in accordance with maximum permissible concentration value for fodder crops and 440 plant samples from total 620 analysed samples or 71% was contaminated in accordance with maximum permissible concentration values for food crops. The main pollutants of fodder crops were Hg (74 occurrences of contamination), Cd (31), Pb (24) and Co (9). The highest heavy metals contamination was in Sokolov region (16% occurrences) and the lowest one was in the control Zamberk region (4%). The main pollutants of food crops were Cd (294 occurrences of contamination) and Hg (142). They were followed by Cr (85), Pb (79), As (72), Ni (14) and Zn (1). The highest heavy metals contamination occurred in Liberec, Sokolov and Chomutov regions (> 80% occurrences of contamination), but even in the control Zamberk region the heavy metals contamination of food crops was very high (57%). The lowest food contamination (49%) occurred in Liberec region, which has more contaminated soils than Zamberk. Summary of the obtained results showed, that relationship between heavy metals contamination of the plants and soils is not simple but very complicated by immissions. In most cases both total contamination degree and collection of pollutant elements of the plants were very different in comparison with soils. Situation is very serious, because, in spite of low degree of the soils contamination in examined regions (< 10%), the heavy metals contamination of agricultural crops is very high (from 3 to 16% contaminated samples of the total number in the case of fodder crops, to 49 to 86% contamination of food crops). Obviously, it is caused by direct heavy metals contamination of the crops from polluted air. Therefore monitoring of the food chain pollution in the immission-exposed regions should be directed on the testing of plant contamination above all.
