Environmental Applications of MC-ICPMS: Using Lead Isotope Ratios From Precipitation Samples to Help Constrain Pollutant Source and Fate in the Great Lakes and South Florida Regions

摘要

Methods to obtain precise measurements of Pb isotope ratios from precipitation samples containing low concentrations of Pb were developed using magnetic sector multiple-collector ICP-MS technology (MC-ICPMS). A comparison of the accuracy and precision of Pb isotope ratios obtained using MC-ICPMS versus conventional ICP-MS was then determined on archived samples previously collected for Hg transport and deposition studies in the Great Lakes and South Florida regions. Precise measurements of lead isotope ratios were obtained from samples of precipitation with 0.50 - 3.00 ppb concentrations of Pb using the Plasma54 MC-ICPMS without Pb pre-concentration. Average ~(207)Pb/~(206)Pb and ~(208)Pb/~(206)Pb two a precision of .060 and .057%, respectively, was obtained with sample consumption of less than 1 ml. Average two a precision of ~(207)Pb/~(206)Pb and ~(208)Pb/~(206)Pb ratios obtained using conventional ICP-MS on the same samples was 0.58 and 0.95% respectively. Samples collected on a regional scale at rural sites in the Great Lakes area contained distinct Pb isotope and trace element signatures characteristic of smelter emissions in the U.S. and Canada. Samples were found to generally have more homogenized Pb isotope and trace element signatures when associated with air parcel transport from urban areas. Samples collected on a smaller spatial scale in urban areas in southeast Florida required high precision Pb isotope ratios obtained with MC-ICPMS to help define source contributions from emission sources such as power plants and waste incinerators. The further refinement of MC-ICPMS techniques has the potential to make precise Pb and other isotope ratio measurements from precipitation and aerosol samples an integral component of source apportionment studies.