Coupling Pb and Zn bioaccessibility with sequential and HNO3 extraction in soil from the industrial area of Volos, Greece

The urban environment is a complicated system where various anthropogenic sources contribute to the accumulation of metals in soil, leading to potential negative environmental effects. Within this context, we performed single and sequential extractions in contaminated soil from the industrial area of Volos. The objective was to understand how Pb and Zn oral bioaccessibility was related to different pools in soil based on sequential and 0.43 M HNO3 extractions. Pb was principally found in the reducible fraction (F2;15-76%), followed by the residual (F4; 9-54%) and the oxidizable (F3; 6-54%), whereas the acid soluble fraction was of minor importance (F1; 2-15%). Zn fractionation was dominated by the residual fraction (20-73%), followed by the oxidizable (10-49%) and the reducible (5-38%). Significant correlations were found between Pb and Zn bioaccessibility and the sum of fractions F1, F2 and F3 (0.50 for Pb and 0.86 for Zn, p<0.01), indicating that the applied bioaccessibility solution preferentially targeted the mobile fraction of Pb and Zn in soil. HNO3-extractable Pb and Zn were highly correlated to bioaccessible Pb and Zn (0.80 and 0.93 respectively, p<0.01), suggesting that the HNO3 can determine the oral bioaccessibility of Pb and Zn in urban soil influenced by industrial activities.