Urban runoff is a significant source of pollutants, including incidental and engineered nanoparticles, to receiving surface waters. The aim of this study is to investigate the impact of urbanization on the concentrations of TiO 2 engineered particles in urban surface waters. The study area boundaries are limited to the Lower Saluda and Nicholas Creek-Broad River from upstream, and outlet of upper Congaree River in Columbia, South Carolina, United States from downstream. This sampling area captures a significant footprint of the urban area of the city of Columbia. Water samples were collected daily from four sites during two rain events. All samples were analyzed for total metal concentrations following acid digestion and for particle number concentration and elemental composition using single particle-inductively coupled plasma-time of flight-mass spectrometry (SP-ICP-TOF-MS). The Ti/Nb ratios in the Broad and Congaree River samples are generally higher than those of natural background ratios, indicating contamination of these two rivers with anthropogenic Ti-bearing particles. Clustering of multi-metal nanoparticles (mmNPs) demonstrated that Ti-bearing particles are distributed mainly among three clusters, FeTiMn, AlSiFe, and TiMnFe, which are typical of naturally occurring iron oxide, clay, and titanium oxide particles, indicating the absence of significant number of anthropogenic multi-element Ti-bearing particles. Thus, anthropogenic Ti-bearing particles are attributed to single-metal particles; that is pure TiO 2 particles. The total concentration of anthropogenic TiO 2 in the rivers was determined by mass balance calculation using bulk titanium concentration and increases in Ti/Nb above the natural background ratio. The concentration of anthropogenic TiO 2 increases following the order 0 to 24 μg L −1 in the Lower Saluda River <0 to 663 μg L −1 in the Broad River <43 to 1051 μg L −1 in Congaree River at Cayce <58 to 5050 μg L −1 in the Congaree River at Columbia. The concentration of anthropogenic TiO 2 increases with increases in urban runoff. The source of anthropogenic TiO 2 is attributed to diffuse urban runoff. This study demonstrates that diffuse urban runoff results in high concentrations of TiO 2 particles in urban surface waters during and following rainfall events which may pose increased risks to aquatic organisms during these episodic events.
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Identification and quantification of anthropogenic nanomaterials in urban rain and runoff using single particle-inductively coupled plasma-time of flight-mass spectrometry
Urban rain and runoff are potential sources of anthropogenic nanomaterials (engineered and incidental, ENMs and INMs) to receiving waterbodies. However, there is currently a limited knowledge on the nature and concentration of anthropogenic NMs in urban rain and runoff and the current study aims to fill this knowledge gap. Runoff samples were collected from drainage outlets of two bridges (Quail Lane and Blossom Street) in Columbia, South Carolina, representing small and medium size bridges at different times over the duration of precipitation events. Rain samples were collected in the vicinity of the same bridges at the same time as the runoff. Two soil samples at depths of 0 to 3 and 3 to 15 cm were collected at each runoff sampling site to extract background natural NMs. The elemental composition of NMs in the rain, runoff, and soils were determined using single particle-inductively coupled plasma-time of flight-mass spectroscopy (SP-ICP-TOF-MS). Nanomaterials were sorted into groups of similar elemental composition and compared among samples using a two-stage agglomerative hierarchical clustering. Several classes of anthropogenic NMs were identified in the urban rain and runoff, including iron, vanadium, titanium, barium, zinc, copper, chromium, tungsten, antimony, tin, and lead-bearing NMs, most likely due to traffic-related emissions. The total concentrations of anthropogenic titanium and tungsten were estimated using mass balance calculations, total Ti and W concentrations, and shifts in the elemental ratios of Ti/Nb and W/U above the natural background ratios. The concentrations of anthropogenic Ti- and W- in Blossom Street and Quail Lane bridges runoff ranged from 6.0 ± 2.1 to 60.6 ± 0.8 μg Ti L −1 and 1.9 ± 0.7 to 20.2 ± 1.8 μg Ti L −1 , and 0.23 ± 0.02 to 0.66 ± 0.03 μg W L −1 , and 0.11 ± 0.01 to 0.38 ± 0.03 μg W L −1 , respectively. Additionally, anthropogenic Ti and W concentrations generally decreased with time following the start of the storm events and increased with increases in traffic density. The detection of anthropogenic NMs in rain implies their occurrence in the atmosphere and thus a potential human exposure/risk via inhalation. The direct discharge of anthropogenic NMs to surface water with urban runoff implies exposure and potential risks to aquatic organisms.
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- Award ID(s):
- 1553909
- NSF-PAR ID:
- 10347398
- Date Published:
- Journal Name:
- Environmental Science: Nano
- Volume:
- 9
- Issue:
- 2
- ISSN:
- 2051-8153
- Page Range / eLocation ID:
- 714 to 729
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1039/d1en00850a
