Distribution of dissolved trace elements amongst colloidal species in soil solutions using asymmetrical flow field-flow fractionation (AF4) coupled to ICPMS

Lina Du^{a, b}, C. W. Cuss^a, W. Shotyk^a, M. Dyck^a and T. Noernberg^a

^a Department of renewable Resources, University of Alberta, Canada

^b College of Natural Resources and Environment, Northwest A& F University, China

lina.du@nwafu.edu.cn

he distribution and speciation of dissolved (<0.45 µm) trace elements (TEs) in soils have implications for their availability, accessibility, and toxicity due to the distinct behavior of each species. The speciation of TEs in soil solutions depends on soil factors (e.g. moisture content, pH, redox potential, ionic strength, organic matter concentrations and soil texture) and the chemical properties of the elements. In this study we aimed to characterize the distribution of TE species in soil solutions using asymmetrical flow field-flow fractionation (AF4) coupled to ICPMS, and examined relationships between speciation and soil properties. AF4-UV-ICPMS is a powerful method for measuring the distribution of TEs among primarily ionic and small species < 1 nm, organic-dominated colloids, and primarily inorganic colloids on the basis of molecular size. Eight sampling locations were chosen from the University of Alberta Breton Plots and associated Bentley Forest Reserve. Soil solutions were collected under vacuum using a surgical (316) stainless steel lysimeters (5 micron pore size) after applying high purity water (deionized, type II Milli-Q). Analyses were performed in the metal-free, ultraclean SWAMP lab. The acid-cleaned lysimeters yielded excellent blank values for most of trace elements of environmental interest (Li, Al, Mn, Co, Ni, Cu, As, Mo, Cd, Ba, Tl, Pb, Th and U). Using the new lysimeter combined with AF4-ICPMS, we provide a new perspective on TE speciation in soil solutions, with a view towards understanding the bioavailability of micronutrients and potentially toxic trace elements.