Direct and subsequent effects of contaminated urban particulate matter on risk element mobility and plant-availability in soil

The effect of soil amendment by different physical fractions (0.063-0.119 mm, and < 0.063 mm) of urban particulate matter (PM) on mobility of potentially risky elements in soil and/or element uptake by plants was investigated in a pot experiment, in which spinach (Spinacia oleracea L.) was cultivated on two different soils. The cadmium (Cd), iron (Fe), lead (Pb), and zinc (Zn) levels were determined in plant biomass and soil after direct and subsequent (evaluated after second vegetation period) soil amendment by PM. Three soil extraction procedures (2 mol·l⁻¹ HNO₃, 0.11 mol·l⁻¹ CH₃COOH, 0.01 mol·l⁻¹, and CaCl₂) were used for the extraction of mobile portions of elements in PM-amended soils. Additionally, the diffusive gradient in thin films (DGT) technique was applied for the assessment of bioavailable pools of the elements in soil. Element mobility decreased in the following order: Cd > Zn > Pb ≈ Fe. The effect of soil physicochemical properties were determinative for extractability as well as for plant uptake of these elements. Neither in the first nor in the second vegetation period did the soil amendment by PM result in significant changes of mobility and plantavailability of the investigated elements which confirms a relatively high stability of PM in the soil and a weak plant uptake of PM-derived risk elements via roots.