Investigation of Zn-, Pb-, and Cd-containing nanoparticles in Canadian urban and Arctic environments: a comprehensive study utilizing single particle inductively coupled plasma mass spectrometry for characterization

Abstract

Measuring metal-containing nanoparticles (NPs) in the environment requires sensitive analytical techniques capable of determining the concentration and elemental composition, particle mass and size. Here we report the characterization of Zn-, Pb-, and Cd-containing NPs by single-particle inductively coupled plasma mass spectrometry (spICP-MS) in snow samples collected from two vastly different sites in Canada: an urban environment from Winnipeg and a remote location at the Müller Ice Cap in Axel Heiberg Island of the Canadian Arctic. Average mass concentrations of Zn-, Pb-, and Cd-containing NPs in fresh snow samples from the urban location ranged from 0.7–149, 1.5–296 and 0.2–1.6 ng L⁻¹, respectively. These concentrations accounted for 0.05–17% of total dissolved (operationally defined as the fraction filtered by a 0.45 µm membrane) concentrations of Zn, 0.2–31.5% of Pb, and 0.05–2.2% of Cd for Cd in the urban snow samples. Mass concentrations for Zn- and Pb-containing NPs in snowpits at depths of 10 to 60 cm from the Müller Ice Cap ranged from 10.0 to 297 ng L⁻¹ (or 2.4–28.8% of the total concentration) for Zn and 0.5 to 2.9 ng L⁻¹ (or 0.9–4.0% of the total concentration) for Pb. Cd-containing NPs were not detectable in the Müller Ice Cap snowpit. A contrary characteristic in the average equivalent diameter for Zn- and Pb-containing NPs was observed in Winnipeg and Müller Ice Cap snow. The average equivalent diameter of Zn-containing NPs in the urban snow (78.5–116.4 nm) was smaller than that from the High Arctic site, whereas the average equivalent diameter of Pb-NPs in the urban snow was 4.8-fold larger than in the High Arctic snow. Additionally, analysis of Pb isotopic ratios indicated that anthropogenic aerosols in the urban snow predominantly originated from North America, primarily via vehicular traffic and various industrial sources. Conversely, aerosols in the Arctic snow were derived from a combination of natural and anthropogenic sources, notably from Asia and North America.