Linking pollution of roadside soils and ecotoxicological responses of five higher plants

This research studies a typical landscape of an agricultural area separated from the road by a ditch with trees. Soils were sampled at 1, 2, 7, 25, and 50 m from the road. The concentrations of polycyclic aromatic hydrocarbons (PAH), total and phyto-available heavy metals (HM), total petroleum hydrocarbons (TPH), and de-icing salts (DS, Cl^-) were determined using standard techniques. A set of higher plants (Lepidium sativum L., Sinapis alba L., Raphanus sativus L., Hordeum vulgare L., Avena sativa L.) was applied for toxicity evaluation of soils. The objective of this research is to find correlations between pollution of roadside soils and their phytotoxicity. HM, TPH and DS contamination of soils was observed in the 0-25 m zone, and PAH contamination was found up to the 50 m. Soil toxicity was declining from the road to the 50 m. Phytotoxicity related to majority of plants performed correlations with the same set of contaminants: TPH, 2-rings PAH, phyto-available Zn, Cu, Pb, and total Zn. No any correlations demonstrated Avena sativa L., being not applicable for ecotoxicological assessment of roadside soils. Despite the phytotoxicity was generally in line with contaminants loads, surprisingly low values were indicated in the ditch characterized by the strong pollution. We attribute this to the contrasting properties of soils there - the higher content of organics and clay. Sensitivity of plants to roadside pollution decreased in the row Lepidium sativum L. > Hordeum vulgare L. > Sinapis alba L. > Raphanus sativus L. The most reliable test-parameters for toxicity estimation were the root and the shoot length, germination rate was not informative indicating low phytotoxicity values. The research showed the importance of the right choice of test-cultures and test-parameters to judge phytotoxicity correctly. Linking the contaminants loads and phytotoxicity effects is valuable for comprehensive ecotoxicological assessment.