Assessment of degree of trace element pollution of soil and root vegetables

Abstract

The investigations were focused on determining the level of trace element pollution of soil and root vegetables cultivated for human consumption in the Miechowski county. The collected soils differed in view of their floatable particles, colloidal clay and organic matter content, as well as pH value. Differences in the total content of trace elements and the content of their soluble forms extracted with 0.1 mol dm HCl solution also occurred. The total content of trace elements in the analysed soils and their soluble forms were determined by soil reaction. Geometric mean of total heavy metals content in the studied soils was as follows: 55.08 mg Zn kg, 8.08 mg Cu kg, 10.05 mg Ni kg, 19.85 mg Pb kg and 0.46 mg Cd kg. The assessment of heavy metals content in the analysed soils was conducted according to the framework guidelines for agriculture elaborated by IUNG. In this respect 44 of analysed samples were classified as soils with natural heavy metals contents. The content of trace elements in cultivated root vegetables was determined by the species, analysed plant part and soil pH. The content of these elements was much higher in plant tops than in roots. For instance, if one assumes geometric mean of cadmium and lead content in parsley roots grown in soil with pH 6.5 as 100, cadmium concentration in leaves was higher by 64 %, and lead content was higher by 36 %. On the basis of the obtained results, content of trace elements in vegetable roots was assessed assuming the critical levels of trace element in agricultural products stated by IUNG. Taking into consideration these criteria was stated that all samples of the vegetable roots fulfilled the requirements of usefulness for human consumption in respect of copper and nickel contents, and majority of them in respect of lead content. However, 7.6 % of samples did not fulfil these requirements because of excessive content of lead (> 1 mg kg), 52.5 % of zinc (> 50 mg kg), and as much as 81.6 % samples because of cadmium excess (> 0.15 mg kg), despite their being cultivated in majority in soils with natural these metals content. Excessive content of copper and nickel was registered only in 1.3 % of tops samples, lead in 51.3 %, zinc in 79.7 %, and cadmium in 98.1 % of tops samples, in which 7.6 % of tops samples did not meet fodder requirements for zinc, and as much as 65.8 % for cadmium. DOI: 10.2428/ecea.2014.21(1)7 ECOL CHEM ENG A. 2014;21(1):69-78 1 Department of Agricultural and Environmental Chemistry, University of Agriculture in Krakow, al. A. Mickiewicza 21, 31–120 Krakow, Poland, phone: +48 12 662 4348, fax: +48 12 662 43 41, email: rrrogoz@cyf-kr.edu.pl, email: rrkielia@cyf-kr.edu.pl * Corresponding author: rrrogoz@cyf-kr.edu.pl Taking in to account all roots and tops samples, only 0.6 % of them did not meet criteria of usefulness for human consumption, because of copper and nickel excess, 29.4 % for lead, 66.1 % for zinc, and as much as 89.9 % of samples contained excessive amount of cadmium. Moreover, in 3.8 % of samples Zn content exceeded admissible values in fodder and in 32.9 % contained excessive amount of Cd.