Influence of wind-speed on short-duration NO2 measurements using Palmes and Ogawa passive diffusion samplers

Nicola Masey,Jonathan Gillespie,Mathew R Heal,Scott Hamilton,Iain J Beverland

doi:10.1016/j.atmosenv.2017.04.008

Abstract

We assessed the precision and accuracy of nitrogen dioxide (NO2) concentrations over 2-day, 3-day and 7-day exposure periods measured with the following types of passive diffusion samplers: standard (open) Palmes tubes; standard Ogawa samplers with commercially-prepared Ogawa absorbent pads (Ogawa[S]); and modified Ogawa samplers with absorbent-impregnated stainless steel meshes normally used in Palmes tubes (Ogawa[P]). We deployed these passive samplers close to the inlet of a chemiluminescence NO2 analyser at an urban background site in Glasgow, UK over 32 discrete measurement periods. Duplicate relative standard deviation was <7% for all passive samplers. The Ogawa[P], Ogawa[S] and Palmes samplers explained 93%, 87% and 58% of temporal variation in analyser concentrations respectively. Uptake rates for Palmes and Ogawa[S] samplers were positively and linearly associated with wind-speed (P < 0.01 and P < 0.05 respectively). Computation of adjusted uptake rates using average wind-speed observed during each sampling period increased the variation in analyser concentrations explained by Palmes and Ogawa[S] estimates to 90% and 92% respectively, suggesting that measurements can be corrected for shortening of diffusion path lengths due to wind-speed to improve the accuracy of estimates of short-term NO2 exposure. Monitoring situations where it is difficult to reliably estimate wind-speed variations, e.g. across multiple sites with different unknown exposures to local winds, and personal exposure monitoring, are likely to benefit from protection of these sampling devices from the effects of wind, for example by use of a mesh or membrane across the open end. The uptake rate of Ogawa[P] samplers was not associated with wind-speed resulting in a high correlation between estimated concentrations and observed analyser concentrations. The use of Palmes meshes in Ogawa[P] samplers reduced the cost of sampler preparation and removed uncertainty associated with the unknown manufacturing process for the commercially-prepared collection pads.

Highlights

Exposure to nitrogen dioxide (NO2) has been associated with adverse effects on human health, including cardio-respiratory illness, hospital admissions and mortality (World Health Organization, 2013)
The mean relative standard deviation (RSD) for duplicate measurements was
If the passive samplers were to be used over multiple sites without reliable information on wind speed variations, or in personal sampling to monitor in individuals with different levels and types of physical activity patterns, our observations suggest that it appears necessary to use field calibrated passive sampling devices with some form of modification to prevent wind-induced turbulence within the diffusion path

Summary

Introduction

Exposure to nitrogen dioxide (NO2) has been associated with adverse effects on human health, including cardio-respiratory illness, hospital admissions and mortality (World Health Organization, 2013). Because of their relatively low cost and simplicity of deployment, have been used in studies to estimate outdoor NO2 concentrations over large geographical areas (Cyrys et al, 2012; Gillespie et al, 2017, 2016; Lewne et al, 2004) and for indoor and personal exposure (Yu et al, 2008). Passive samplers can be grouped into tube and badge designs (Cape, 2009; Tang et al, 2001; Yu et al, 2008). Tube samplers, including the commonly-used Palmes sampler (Palmes et al, 1976), have relatively long diffusion paths and low uptake rates, and are typically used for measuring concentrations over 1e5 week periods. Com/), have relatively short path lengths and higher uptake rates facilitating measurement of relatively low NO2 concentrations and exposures over shorter intervals (e.g. 24 h) Badge samplers, including Ogawa samplers (http://ogawausa. com/), have relatively short path lengths and higher uptake rates facilitating measurement of relatively low NO2 concentrations and exposures over shorter intervals (e.g. 24 h)

Methods

Results

Conclusion