Table 2.
Effect of hourly traffic and weather on black carbon concentrations at U2 and S1
| Variable (Interquartile range increase) | Beta Estimatea (p-value) | ||
|---|---|---|---|
| U2b | S1b | ||
| Trucks/Buses | 0.62 (0.003) | 0.20 (0.0009) | |
| per 443/hr increase | per 70.5/hr increase | ||
| Cars | 0.19 (0.17) | 0.07 (0.42) | |
| per 1895/hr increase | per 479/hr increase | ||
| Wind Direction | NW to NE | Reference | Reference |
| NE to SE | −1.29 (0.0008) | −0.22 (0.04) | |
| (S2 downwind of highway) | SE to SW | −0.09 (0.83) | 0.21 (0.13) |
| (U2 downwind of roadway) | SW to NW | 0.48 (0.25) | 0.15 (0.10) |
| Wind Speed | −1.67 (<0.0001) | −0.12 (0.0009) | |
| per 3.4m/s increase | per 1.5 m/s increase | ||
| Humidity | 0.04 (0.31) | 0.29 (0.0009) | |
| per 50.8% increase | per 26% increase | ||
| Temperature | −0.26 (0.273) | 0.22 (0.007) | |
| per 5.1°C increase | per 5.5°C increase | ||
| Mixing Height | −1.75 (0.51) | −0.14 (0.003) | |
| per 354 m increase | per 479 m increase | ||
a
Describes change in concentration of BC (μg/m3) per interquartile range increase in dependent variable, adjusted for other variables in the model.
b
U2 = Urban School 2, S1 = Suburban School 2003 measurements.
c
Variables significantly associated with changes in BC (p<0.05) are in bold.