Table 2.
Summary of median one-minute PNC by monitoring platform.
| Period | Median 1-min PNC in Boston (particles/cm3) | Median 1-min PNC in Chelsea (particles/cm3) | ||||
|---|---|---|---|---|---|---|
| Central Site | On Roadc | Residential | Central Site | On Roadc | Residential | |
| Wintera | 28,000 | 33,000 | 21,000 | 20,000 | 26,000 | 16,000 |
| Summera | 14,000 | 18,000 | 8,500 | 11,000 | 14,000 | 9,100 |
| Overnightb | 16,000 | n/a | 9,500 | 13,000 | n/a | 10,000 |
| Daytimeb | 21,000 | 12,000 | 15,000 | 12,000 | ||
| All Data | 18,000 | 27,000 | 11,000 | 14,000 | 18,000 | 11,000 |
a
Dec., Jan., and Feb. represent winter months; Jun., Jul., and Aug. represent summer months.
b
18:00–06:00 represent overnight hours; 06:00–18:00 represent daytime hours.
c
On-road data was largely from the daytime, thus no comparison was made to overnight hours (n/a = not applicable).