Ultrafine particles in the urban atmosphere

Damayanti, Seny (2026). Ultrafine particles in the urban atmosphere. University of Birmingham. Ph.D.

Preview

Damayanti2026PhD.pdf
Text - Accepted Version
Available under License All rights reserved.
Download (12MB) | Preview

Abstract

Ultrafine particles (UFPs, Dp < 100 nm) are recognised as having a more detrimental effect on human health and climate compared to larger particles. However, critical gaps persist concerning this unregulated pollutant, particularly regarding their control strategies, personal exposure assessment, and new particle formation (NPF) in real-world urban settings. This thesis addresses these gaps through a combination of data analysis obtained from long-term monitoring and short field campaign data and personal exposure campaigns in urban areas in the UK. The research aims to (i) quantify long-term trends (2010-2021) in UFPs particle number and size distribution along with other pollutants at an urban traffic site (London Marylebone Road), (ii) assess personal exposure to important UFPs metrics, specifically particle number concentration (PNC), average diameter, and lung deposit surface area (LDSA) by mobile measurement, (iii) evaluate methods for normalising short-term personal exposure to UFPs and other pollutants with the aim of reflecting an annual mean exposure, and (iv) investigate NPF using an observational dataset collected during a 1-month summer campaign at an urban background site in Manchester.

The results show a statistically significant reduction in all examined air pollutants ranging from 4.7%/yr to 8.3%/yr, with the most rapid decline reported in Black Carbon (BC) and accumulation mode particle concentrations. Nevertheless, there has been little change in the concentration of the nucleation mode (Dp < 30 nm). The implementation of the Diesel Particulate Filter (DPF) was associated with a significant reduction in BC, confirming its efficacy under real-world conditions. Personal exposure assessments revealed that exposure to PNC and LDSA with a smaller average diameter was higher during bus journeys compared to walking, particularly on major roads compared to residential roads. A method to eliminate spikes in PNC concentrations during walking trips enables source estimation, specifically distinguishing hyperlocal sources from local background contribution (19%) and general local increments (9%). Moreover, new techniques for normalising personal exposure data, which incorporate a correction factor for two distinct timeframes (during the campaign and over a yearly period), have effectively diminished the non-normalised concentration for the majority of examined pollutants, thereby enhancing their comparability to the annual average concentration recorded at a local air monitoring station. NPF substantially contributes to total PNC under favourable conditions such as higher solar radiation and sulphuric acid levels, less polluted atmospheric conditions, and higher wind speed. This study suggests that sulfuric acid is the main driver of nucleation, while ULVOC may play a more important role in particle growth.

The findings demonstrated that while regulatory intervention has significantly decreased solid particles, its impact on the nucleation mode remains limited. Therefore, a more effective control technology is required to mitigate UFP emissions in urban areas. Employing spike removal and normalisation techniques for personal exposure data enhances the distinction between episodic peaks and the actual background exposure, as well as weather-independent trend estimations. Consequently, it improves the understanding of personal exposure evaluation to improve air quality regulations in urban areas. Furthermore, NPF events as a nontraffic UFP source play an important role in urban areas, underscoring the necessity to control gaseous precursors to effectively mitigate personal exposure to UFPs.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):