Personal exposure of street canyon intersection users to PM_(2.5), ultrafine particle counts and carbon monoxide in Central London, UK

摘要

Short-term human exposure to PM_(2.5), ultrafine particle counts (particle range: 0.02-1 μm) and carbon monoxide (CO) was investigated at and around a street canyon intersection in Central London, UK. During a four-week field campaign, groups of four volunteers collected samples at three timings (morning, lunch and afternoon), along two different routes (a heavily trafficked route and a backstreet route) via five modes of transport (walking, cycling, bus, car and taxi). PM_(2.5) was sampled using high-flow gravimetric personal samplers, ultrafine particle counts were measured using TSI P-TRAKs and Langans were used to measure CO exposure. Three hundred and ninety-four samples were collected—197 PM_(2.5), 86 ultrafine particle count and 111 CO. Arithmetic means of PM_(2.5) personal exposure were 27.5, 33.5, 34.5, 38.0 and 41.5 μg m~(-3), ultrafine particle counts were 67773, 93968, 101364, 99736 and 87 545 pt cm~(-3) and CO levels were 0.9, 1.1, 0.8, 1.3 and 1.1 ppm for walking, cycling, bus, car and taxi respectively. On the heavily trafficked route, personal exposure was 35.3 μg m~(-3), 101142 pt cm~(-3) and 1.3 ppm, and on the backstreet route it was 31.8 μg m~(-3), 71628 pt cm~(-3) and 0.6 ppm for PM_(2.5), ultrafine particle counts and CO, respectively. Personal exposure levels were high during the morning measurements for all three pollutants (34.6 μg m~(-3), 106 270 pt cm~(-3) and 1.5 ppm for PM_(2.5), ultrafine particle counts and CO, respectively).There was a moderately strong correlation between personal exposure of ultrafine particle counts and CO (r = 0.7, N = 67) but a weaker correlation between PM_(2.5) and ultrafine particle counts (r = 0.5, N = 83) and a low correlation between PM_(2.5) and CO exposure (r = 0.2, N = 105). The exposure assessment also revealed that the background and kerbside monitoring stations were not representative of the personal exposure of individuals to PM_(2.5) and CO at and around a street canyon intersection.