Quantification and Characterization of Nanoparticulate Zinc in an Urban Watershed

Abstract

The recent expansion in the use of nanomaterials in consumer and industrial applications has led to a growing concern over their behavior, fate, and impacts in environmental systems. However, engineered nanoparticles comprise only a small fraction of the total nanoparticle mass in aquatic systems. Human activities, particularly in urban watersheds, are increasing the population of incidental nanoparticles and are likely altering the cycling of more abundant natural nanoparticles. Accurate detection, quantification, characterization, and tracking of these different populations is important for assessing both the ecological risks of anthropogenic particles, and their impact on environmental health. The urban portion of the South Platte watershed in Denver, Colorado (United States) was sampled for zinc to identify and quantify different nanomaterial sources. Single particle ICP-QMS was employed, to provide single elemental (Zn) signals arising from particle detection events. Coupling spICP-QMS to sample pre-fractionation (sedimentation, filtration) provided some insights into Zn association with nanoparticulate, colloidal, and suspended sediment phases. Single particle ICP-TOFMS (spICP-TOFMS) provided quantification across a large atomic mass range, yielding an even more detailed characterization (elemental ratios) on a particleby-particle basis, providing some delineation of multiple sources of particles. Across the watershed, on average, 21% of zinc mass was present as zinc-only particles with a rather uniform mean size of 40.2 nm. Zinc that was detected with one or more other elements, primarily Al, Fe, and Si, is likely to be present as heteroagglomerates or within mineral colloids. Although spICP-TOFMS provides a substantial amount of information, it is still in its early stages as an analytical technique and currently lacks the requisite sensitivity to study the smallest of nanoparticles. As this technique continues to develop, it is anticipated that this methodology can be broadly applied to study sources, behavior and effects of a disparate variety of nanoparticles from both geogenic and anthropogenic origins.

Monodisperse microdroplets: a tool that advances single-particle ICP-MS measurements

“…as natural or engineered. 37,[64][65][66][67][68] In our sp-ICP-TOFMS measurements, we use microdroplet sample introduction in two distinct ways: (1) for online calibration of NP mass in individual NPs, and (2) as a tool to study data analysis approaches for the quantitative detection of fast transient signals, which is critical for reliable PNC determination in sp-ICP-TOFMS. In both of these applications, microdroplets are a exible platform for controlled introduction of discrete masses of analytes which allow us to better probe sp-ICP-TOFMS measurements.…”

Emerging investigator series: automated single-nanoparticle quantification and classification: a holistic study of particles into and out of wastewater treatment plants in Switzerland

“…Between the extremes of abundant mmNP or smNP fractions, there are some elements-such as Ce and Zn-that have moderate mmNP fractions (between 40-60% mmNPs). These elements are known to exist as both smNPs and mmNPs; 10,25 an even distribution of smNP and mmNP types could indicate an equal contribution (on a particle-number basis) of natural and anthropogenic NPs in the wastewater samples. Or again, this could be an artifact caused by associated elements at masses below the critical value in some of the registered smNPs.…”

“…8 A challenge in developing models to calculate mass flows of NPs is that they depend on manufacturers to disseminate accurate data about production and use of NPs, which is often not required. The most used NPs across all industries are carbon black, TiO 2 , Ag, SiO 2 , Fe(oxide), ZnO, Al 2 O 3 , carbon nanotubes, graphene, and nanoclays; 3,9,10 however, there are many more types of ENPs. There are also many incidental NPs (INPs) that are produced as a byproduct of human activities that remain unknown and/or have not been studied sufficiently to accurately predict their contribution to system-wide models of NP fate and transport.…”

“…Being able to distinguish between naturally occurring NPs (NNPs) and engineered NPs (ENPs) has been the topic of many studies. 10,[22][23][24][25][26][27][28][29] Although there is ambiguity on the best method of investigation of these particles types, the most prominent NP characteristics used to categorize a NP as either engineered or natural include composition, crystal structure, particle morphology, and shape. 30,31 An advantage of sp-ICP-TOFMS is that one can simultaneously measure most of the metal and metalloid elements in single run, which means that non-targeted analysis can be used to detect variable and unique elemental fingerprints of different particle types.…”

Benefits at the nanoscale: a review of nanoparticle‐enabled processes favouring microbial growth and functionality

“…Similarly, cryogenic‐focused ion beam‐scanning electron microscopy (cryo‐FIB‐SEM) will soon provide 3D structures of microbial‐nanoparticle aggregates. Lastly, spICP‐MS can provide the elemental compositions of hundreds to thousands of suspended nanoparticle aggregates within minutes (Lee et al ., 2014; Bevers et al, 2020). A derivation of this technique has already been used to probe the variation in Fe content of magnetotactic bacteria at the single cell levels using single‐cell ICP‐MS (Amor et al ., 2020).…”