THE MIGRATION OF CADMIUM AND LEAD FROM SOIL TO PLANTS IN AREA OF HEAVY METAL INDUSTRY PRODUCTION

摘要

The transition of cadmium and lead compounds from the organic soil layer into the local plants represents a significant risk of contamination of the food chain and can affect the health of the population. We have focused on the determination of the content of cadmium and lead in soil and biomass. The measured values were compared with the limit values laid down by the legislation of hazardous substances in the soil (Act No. 220/2004 Coll.). Samples of soil (n = 37) and plants (n = 37) were taken in the northern part of the Slovak Republic in the south to southeasterly direction from the source of contamination, which is an company in city Istebne. This company is the diversified manufacturer of ferroalloys in central Europe. The history of company is dated back to the year 1952, when first ferroalloys were manufactured in Slovakia. Soil samples were taken from a depth of 0.10 m and samples of plant material sampling were collected from the same sampling sites. We have defined the basic parameters that affect the mobility of heavy metals in soil (pH active, pH exchange, humus and oxidizable carbon). Analyzes to determine a bioavailable forms of cadmium and lead was performed by extraction of soil leachate in 50 cm~3 of NH_4NO_3 (1 mol/dm~3). Samples of the dried plant samples were mineralized by acid digestion using microwave digestion device MARS X-press. The end of determining the cadmium and lead content in the samples was performed by atomic absorption spectrometer Varian 240 FS. The average value of the active soil reaction was 7.02 ± 0.67 and exchange soil reaction was 5.91 ± 0.79. Based on analyses of soil from the area could be described as a weakly acidic to neutral. The total content of cadmium and lead in soil and plants depends on the content of humus and oxidizable carbon. Median humus content in soil samples was 3.27 ± 3.41 % in the case of oxidizable carbon 1.90 ± 1.98 %. The cadmium and lead content in biomass increases with the content of heavy metals in soil and humus. The content of cadmium in soil samples was 0.11 ± 0.05 mg/kg, which exceeded the limit value by 2.4 times. The lead content in soil samples was 0.36 ±0.14 mg/kg, which exceeded the limit value by 6.8 times. In the case of plant material, the average of cadmium content was 0.20 ± 0.27 mg/kg and lead content was 1.20 ± 1.13 mg/kg. The results are set out in the fresh biomass conversion of dry matter, whose average content was 30%. The limit values were exceeded in 22 (n = 37) soil samples in the case of cadmium and lead in all 37 (n = 37) samples.