Spectraa 240z

The total heavy metal content was determined after mineralization in a 2.5 mL 65% HNO3 Suprapur^® (Merck, Darmstadt, Germany) and 7.5 mL 37% HCl Suprapur^® (Merck, Darmstadt, Germany) mixture. This mixture is able to extract almost all heavy metals from the soil solution, with the exception of silicate and aluminosilicate soil grid structures.
The mineralization tubes were sealed and placed in a microwave digestion apparatus MarsX-press5 (CEM Corp., Matthews, NC, USA). The samples were filtered through quantitative filter paper Filtrak 390 (Munktell, GmbH, Bärenstein, Germany) and diluted with deionized water (0.054 µS/cm). For all procedures, high purity analytical reagents were used. The total heavy metal content was determined using the atomic absorption spectrometer SpectrAA 240FS (Varian Inc., Mulgrave, VIC, Australia) (Mn, Zn, Cu, Cr, Ni) and the atomic absorption spectrometer SpectrAA 240Z (Cd and Pb) with Zeeman background correction. CertiPUR^® (Merck, Darmstadt, Germany) calibration standard was used for calibration of the instruments.
The total Hg content was determined by the CV-AAS method on a selective Hg analyzer AMA-254 (Altec, Praque, Czech Republic.)

Mobile (available) forms of heavy metals, which are more accessible for plants, were determined by extracting 20 g of dried soil samples in 50 mL of NH₄NO₃ (Sigma-Aldrich, Inc., Saint-Loius, MO, USA) (c = 1 mol/dm³) using a horizontal shaker Unimax 2010 (Heidolph Instrument, GmbH, Schwabach, Germany) for 2 h. After extraction, the samples were filtered through quantitative filter paper Filtrak 390 (Munktell, GmbH, Bärenstein, Germany).
The content of mobile forms of heavy metals in soil was determined using the atomic absorption spectrometer SpectrAA 240FS (Varian Inc., Mulgrave, VIC, Australia) (Mn, Zn, Cu, Cr, Ni) and atomic absorption spectrometer SpectrAA 240Z (Cd and Pb) with Zeeman background correction. CertiPUR^® (Merck, Darmstadt, Germany) calibration standard was used for the calibration of the instruments.
The measured concentrations of selected heavy metals in soil samples were compared with Slovakian limit values, as given by Act No 220/2004, as well as with Threshold value given by the European Commission (2006).