Influence of PAH's and trace elements contamination on soil microbiological activity and ecotoxicity

Abstract

Soil contamination with PAH’s and trace elements in Kaunas city (Lithuania) was investigated and soil ecotoxicity was evaluated by means of the soil microbiological activity and assay battery of biotests. Composite topsoil (5 cm) samples in 3 replicates were collected randomly in August from the potentially contaminated sites, such as transport spot, gas station, electric power station, airport, landfill, and village with individually heated houses. Soil sample from the town municipal park was taken as a control sample. Fresh soil samples were homogenized, sieved through 1 mm mesh, and stored at 4o C in the plastic boxes with perforated lids to ensure conditions for the microbiological activity. Also, a part of each soil sample was air dried, grounded, homogenized, sieved through 2 mm mesh sieve, and stored in the plastic boxes at lab conditions for the physicochemical and chemical analyses. Air dried soil samples were used for the analysis of the physicochemical properties, and for the hexane–acetone extraction for the PAHs determination by GC-MS, and aqua-regia extraction for the determination of trace elements by ICP-MS. Fresh soil samples were preincubated at 20oC and analyses of the MBC, BR, SIR,PAMO, and PAO were performed. Also, ecotoxicity assay battery of nematodes, microarthropods and plant seed germination tests was applied to understand influence of the soil contamination on the soil ecosystem (Allef and Nannipieri 1995). PAH (Σ 23 PAH < 5 mg∙kg-1) and trace element amounts were in the range of the legislative values, but V, Ni, Cu, As, Zn, Pb, Mo, Sb, Hg, and Cd amounts exceeded background soil concentrations in twice in some specific sites depending on the source of pollution. Pollutants impact on the soil microbiological activity decrease and ecotoxicity increase in the contaminated sites was evident and will bedescribed at the conference presentation