Quantitatively differentiating foliar adhesion and absorption of different lead-based particles on Solanum melongena L.

Abstract

A variety of atmospheric lead-based chalcogenide particles (PbX_n, where X = S or O) present a significant risk to environmental and public health. Foliar uptake dominates atmospheric Pb contamination of crops, although the precise mechanisms are unclear, particularly for different types of PbX_n. In this paper, the effects of 5 atmospheric PbX_n (PbS-S, PbS-Q, Pb₃O₄, PbO₂ and PbO) properties, including particle lateral size, hydrodynamic size, zeta potential, contact angle, BET surface area and K_sp, on the adhesion and absorption of eggplant (Solanum melongena L.) leaves were studied. The adhesion and absorption of PbX_n in leaves were quantitatively distinguished by a water–EDTA-2Na solution step-by-step rinsing method. Adhesion accounted for 33–98% of the total foliar uptake and caused overestimation to a varying extent of total foliar absorption of different PbX_n (uptake includes adhesion and absorption). The contribution of stomata and cuticle to PbX_n particle absorption was also tested. Cuticular pathway contributed to 19–69% of the total absorption. Multiple linear regression and path analyses revealed that zeta potential and hydrodynamic size were the two most positive factors for leaf adhesion, while for absorption it was the opposite. BET surface area was the most important property of PbX_n to be absorbed through the cuticular/stomatal pathway. This study provides an important insight into foliar uptake mechanisms of common atmospheric lead-based particles and can be used to construct more accurate and environmentally ecological risk assessments of Pb contaminants.