Assessment of Heavy Metals Contamination and Ecological Risk of Roadside Agricultural Soil, Used for Sunflower (Helianthus annuus L.) Cultivation

The present study is an attempt for comprehensive assessment of the pollution intensity andcorresponding ecological risk of heavy metals including Cd, Co, Cr, Cu, Fe, Ni, Pb, Zn and Sbfor agricultural soil, located alongside the national road II-81 in Bulgaria, used for the sunflower(Helianthus annuus L.) cultivation, by various factors and indices calculation. In total, 18 surface soil samples (0 - 20 cm depth) were collected at distances 11 m, 36 m and61 m from the road edge at two sunflower plants’ growth stages: vegetative (V-3) and maturity (R9).The total concentrations of heavy metals of soil samples, collected at two different sunflower growthstages were used for assessment of the potential ecological risk. Based on the results for the potentialecological risk index, pollution load index, enrichment factor, contamination factor and the degree ofcontamination, calculated from the average total concentrations, considerable pollution of the testedagricultural soil was observed, mainly with Sb.The values of enrichment factor show that with the exception of Fe, Cr and Ni the rest of thetested heavy metals are mostly from anthropogenic sources. There are strong, not statisticallysignificant correlations between the enrichment factors, ecological risk index, pollution load index andcontamination degree and the distance from the road edge and strong correlations between enrichmentfactors of heavy metals related to the road traffic emissions and the distance from the road edge. Thevalues of the factors and indices above mentioned are lower at the growth stage R9 than at the growthstage V-3 that shows the sunflower capacity of accumulation of the tested heavy metals.