Spatiotemporal variability of nitrogen dioxide (NO2) pollution in Manchester (UK) city centre (2017–2018) using a fine spatial scale single-NOx diffusion tube network

Abstract

Nitrogen dioxide (NO2) is linked to poor air quality and severe human health impacts, including respiratory and cardiovascular diseases and being responsible annually for approximately 23,500 premature deaths in the UK. Automated air quality monitoring stations continuously record pollutants in urban environments but are restricted in number (need for electricity, maintenance and trained operators), only record air quality proximal to their location and cannot document variability of airborne pollutants at finer spatial scales. As an alternative, passive sampling devices such as Palmes-type diffusion tubes can be used to assess the spatial variability of air quality in greater detail, due to their simplicity (e.g. small, light material, no electricity required) and suitability for long-term studies (e.g. deployable in large numbers, useful for screening studies). Accordingly, a one passive diffusion tube sampling approach has been adapted to investigate spatial and temporal variability of NO2 concentrations across the City of Manchester (UK). Spatial and temporal detail was obtained by sampling 45 locations over a 12-month period (361 days, to include seasonal variability), resulting in 1080 individual NO2 measurements. Elevated NO2 concentrations, exceeding the EU/UK limit value of 40 µg m−3, were recorded throughout the study period (N = 278; 26% of individual measurements), particularly during colder months and across a wide area including residential locations. Of 45 sampling locations, 24% (N = 11) showed annual average NO2 above the EU/UK limit value, whereas 16% (N = 7) showed elevated NO2 (> 40 µg m−3) for at least 6 months of deployment. Highest NO2 was recorded in proximity of highly trafficked major roads, with urban factors such as surrounding building heights also influencing NO2 dispersion and distribution. This study demonstrates the importance of high spatial coverage to monitor atmospheric NO2 concentrations across urban environments, to aid identification of areas of human health concern, especially in areas that are not covered by automated monitoring stations. This simple, reasonably cheap, quick and easy method, using a single-NOx diffusion tube approach, can aid identification of NO2 hotspots and provides fine spatial detail of deteriorated air quality. Such an approach can be easily transferred to comparable urban environments to provide an initial screening tool for air quality and air pollution, particularly where local automated air quality monitoring stations are limited. Additionally, such an approach can support air quality assessment studies, e.g. lichen or moss biomonitoring studies.

Exposure to Air Pollution from Road Traffic and Incidence of Respiratory Diseases in the City of Meknes, Morocco

“…The effects of meteorology on the concentration and dispersion of nitrogen dioxide have been revealed in many studies. As in our case study, some of them confirm the absence of a significant difference in average NO 2 concentration between the different study periods [72,73]. On the other hand, other studies have revealed a periodic variability attributed mainly to differences in the meteorological profiles of these periods [74,75].…”

High spatial resolution assessment of air quality in urban centres using lichen carbon, nitrogen and sulfur contents and stable-isotope-ratio signatures

“…nitrate (NO 3 − ) and ammonium (NH 4 + ). Accordingly, different nitrate (NO 3 − ) and ammonium (NH 4 + ) concentrations have been reported in X. parietina samples across Manchester (Niepsch et al 2021b), suggesting site-specific and diverse sources; e.g., from vehicular, domestic and industrial emissions that potentially impacted on lichen wt% N recorded by this study (further discussed in "Lichen nitrogen stableisotope ratios (δ 15 N)"; Fig. 8).…”

“…Indeed, lichen enrichment in 15 N was recorded at sampling locations in proximity to the highlytrafficked Mancunian Way with approximately 30,000 vehicles passing daily (DfT 2017). Comparably, δ 15 N was positively correlated with passively-derived NO 2 concentrations by Niepsch et al (2021a) in X. parietina (Pearson's r = 0.54, p < 0.01) and Physcia spp. (Pearson's r = 0.37, p < 0.01; Table S6), consequently suggesting a major NO x -related influence in Manchester.…”

“…To further investigate potential impacts by nitrogen compounds on lichens, as reported by Pinho et al (2017), N wt% and δ 15 N was linked to lichen NO 3 − and NH 4 + (Fig. 7), using the nitrogen speciation method described by Niepsch et al (2021b). Species-specific responses to nitrogen compounds, − concentrations, whereas no such relationship was recorded for X. parietina (Fig.…”

Distinguishing atmospheric nitrogen compounds (nitrate and ammonium) in lichen biomonitoring studies

“…However, NH4 + concentrations were elevated in both environments (no statistically significant difference), although likely linked to different sources, whereas NO3concentrations are potentially related to increased NOx emissions in the urban environment. Comparably, Niepsch et al (2021) reported elevated NO2 concentrations across Manchester 76 .…”