Detection and characterization of Cu-bearing particles in throughfall samples from vine leaves by DLS, AF4-MALLS (-ICP-MS) and SP-ICP-MS

Abstract

Some evidence shows that Cu-based fungicides used on vines increase the levels of copper in soil and sediments. The rainfall induced foliar wash-off is the most complex pathway of contaminants in the environment. Since the Cu wash-off occurs during rain episodes, Cu can be transported in streams along considerable distances as particulate forms. The colloidal properties of Cu suspended in runoff are related to its mobility in the environment. Asymmetrical-flow field-flow fractionation (AF4) performs colloid separation based on hydrodynamic properties and can contribute as a useful tool to understand the environmental fate of colloidal contaminants. In this work, we studied the Cu-bearing micro- and nanoparticles (NPs) in throughfall samples containing fungicide residues of vines previously sprayed with copper oxychloride. Suspended particles in the throughfall were characterized by Dynamic light scattering (DLS) and AF4 coupled to multi-angle laser light scattering and inductively coupled plasma mass spectrometry (AF4-MALLS-ICP-MS). Then, single-particle ICP-MS analysis (SP-ICP-MS) was performed to evaluate the presence of Cu NPs. AF4 allowed particle fractionation and detection in throughfall waters coupled AF4-MALLS-ICP-MS demonstrating that Cu was bound to a well-defined fraction of small particles clearly separated from a broad size distribution of organic colloids that did not contain Cu. SP-ICP-MS supported the evidence that throughfall contained Cu bound to organo-mineral particles of much smaller size than the powder formulation sprayed on vines, which favors their mobility in natural waters.