1. Dep. of Analytical Chemistry, Faculty of Chemistry Gdansk Univ. of Technology 11/12 Narutowicza St. Gdańsk 80‐233 Poland
2. Institute of Geography Kazimierz Wielki Univ. 8 Koscielecki Sq. Bydgoszcz 85‐033 Poland
3. Dep. of Sanitary Engineering, Faculty of Civil and Environmental Engineering Gdansk Univ. of Technology 11/12 Narutowicza St. Gdańsk 80‐233 Poland