Utilization of Contact Tests for Evaluation of Agricultural Soils

Abstract

A soil has been of great concern throughout the world due to increasing environmental awareness and interest in the quality and management of such soils. Košice, the city in eastern Slovakia, is exposed to typical urban contamination sources such, furthermore, being the largest steel producer in Central Europe, it is long-term environmentally loaded by the iron and steel works that represent the largest source of (metallic elements) contamination in Slovakia. Five sampling sites located in the surrounding of U.S.Steel Košice (Slovakia), were selected, where almost all the agricultural soils were polluted by the metallic elements (Fe3+, Al3+, Mn2+, Cu2+, As3+). Agricultural soils toxicity was assessed with the toxicity bioassay -Phytotoxkit. Tests of limit concentrations of the elements (Fe3+, Al3+, Mn2+, Cu2+ and As3+) and Tests of soil concentration series (100-50-25-12.5%) - screening tests mustard Sinapis alba and Lepidium sativum were performed. The testing of the concentration range was performed in order to determine the values of 14d/EC50 and the possibility of comparing the ecotoxicity of metallic elements in agricultural soils (ISO 11269-2 Soil quality). Four concentrations were prepared in test plates: 12.5 - 25 - 50 - 100% soil samples. Concentration of metals in the soil samples ranged from 24400 to 39000 mg/kg for iron; 54000 to 85000 mg/kg for aluminum; 381 to 1035 mg/kg for manganese; 27 to 59 mg/kg for copper; and 7 to 36 mg/kg for arsenic. Based on the median concentration, the metals in the soils were arranged in the following decreasing order: Al3+ > Fe3+ > Mn2+ > Cu2+ > As3+. In the agricultural soils (4USS-PW) showed high contamination values for the iron with a median 35300 mg/kg, aluminum with a median 82500 mg/kg, manganese with a median 1027 mg/kg. The median level of arsenic in the soil (4USS-PW) was 34 mg/kg, this indicate higher concentration as the limit concentration is 25 mg/kg (Law No. 220/2004-2). Agricultural soils 1-3USS and 5USS showed less than 50% inhibition of the seed germination and root growth in the S.alba and L. sativum tests compared to the control, excepting of soil from 4USS plant west (values of the EC50 to 65%). Thus, the results of phytotoxicity tests were consistent with the chemical data. The rapid increase in urbanization, industrialization, human population, and traffic flow has resulted in the environment surrounding farmland ecosystems being critically contaminated by metallic elements.