Relationship of Soil Properties to Fractionation of Pb and Zn in Soil and Their Uptake into Plantago lanceolata

Abstract

Soil samples (0 to 5 cm) from 30 locations in the Celje region, Slovenia, an area that has been subjected to severe industrial emissions of Pb and Zn, were analyzed for selected soil properties and subjected to a six-step sequential extraction of Pb and Zn. Phyto-available forms of heavy metals: soluble in soil solution and exchangeable from soil colloids to soil solution together accounted for 0 to 1.68% of Pb and 0 to 40.8% of total soil Zn. Most of the Pb and Zn was found to reside in less labile forms bound to carbonate (2.04 to 43.5% Pb, 3.9 to 35.1% Zn), bound to Fe and Mn oxides (0 to 16.1% Pb, 1.4 to 25.4% Zn), bound to organic matter (35.8 to 71.1% Pb, 14.8 to 56.2% Zn), and in the residual fraction (10.4 to 53.4% Pb, 14.2 to 75.3% Zn). Factor analysis and stepwise multiple regression revealed that the concentration of Pb in the proposed indicator plant, narrow leaf plantain (Plantago lanceolata) did not correlate with the measured soil properties, Pb fractionation in soil, and total soil Pb. Plant uptake of Zn, however, significantly correlated with soil pH and with the share of phyto-available forms of Zn in the soil (R2 = 86.9). A statistically significant correlation (P<0.01) was found between the fractions of Pb and Zn carbonates and soil organic matter content (R2 = 90.6 and 90.9, respectively); the fraction of Pb bound to organic matter and soil organic matter content (R2 = 90.6); the residual fraction of Pb and total Pb content in soil (R2 = 95.7); the fraction of Zn bound to Fe an Mn oxides, the fraction of Zn bound to organic matter, the residual fraction of Zn and total Zn content in soil (R2 = 75.9, 93.2, and 87.4, respectively). Soil texture, pH, and cation exchange capacity did not affect the relative proportions of Pb and Zn forms in soil.