A Shelter to Protect a Passive Sampler for Coarse Particulate Matter, PM_{10 − 2.5}

Figures & data

FIG. 1 Shelters tested in the wind tunnel.

FIG. 2 Experimental setup for laboratory tests.

TABLE 1 Summary of wind tunnel tests averaged over all wind speeds and for the highest wind speed (24 km hr⁻¹)

	PM10 − 2.5 Ratio	PM10 − 2.5 Ratio
Sampler	(all wind speeds)	(24 km hr^−1)	CV%
Dichot	–	–	15.4
Flat Plates	1.04	1.4	13.3
Louvered Plates	2.36	1.6	40.7
Fence	4.86	8.7	25.2
Drum	**	10.5	16.1
Funnel Lid	**	21.8	49.9
Gill Screen	8.48	13.1	40.5
**only done at high speed.

FIG. 3 PM_{10 − 2.5} ratio for four shelters by wind speed: A. Gill Screen, Fence, and Louvered Plates shelters; B. Flat Plates shelter.

FIG. 4 Particle size distributions measured on the substrates for the four shelters tested at three wind speeds: A. 24 km hr⁻¹; B. 8 km hr⁻¹; C. 2 km hr⁻¹. Note that Y-axis scales vary.

TABLE 2 Summary of field tests

	Test	Dichot PM10 − 2.5	Passive/Dichot	Passive	Mean Wind	Mean Precip	Mean	Mean
Site	Week #	(μ g m^−3)	Ratio	CV %	Speed (km hr^−1)	(cm day^−1)	RH%	Temp (°C)
Airport	2	21.2	1.39	3.8	5.05	0.01	70.3	6.9
Airport	3	13.9	1.27	7.3	7.81	0.43	72.8	6.0
Airport	4	12.8	1.11	19.9	9.29	0.01	71.5	−1.1
Airport	5	13.4	1.25	7.2	6.00	0.00	70.1	1.7
Airport	6	3.7	1.18	9.4	5.90	0.65	84.5	0.8
IREH	1	20.9	1.43	4.1	3.22	0.01	64.8	4.6
IREH	2	12.5	1.56	3.9	3.70	0.32	75.8	7.3
Residence	4	13.4	1.11	20.8	2.66	0.01	71.5	−1.1
Mean	—	14.0	1.29	9.5	5.45	0.18	72.7	3.1
St. Dev.	—	5.48	0.16	7.0	2.29	0.25	5.70	3.49

TABLE 3 Summary of PM_{10 − 2.5} measured with passive sampler regressed on that measured with dichotomous sampler: with and without meteorological data

Model without Meteorological Data
Parameter	Estimate	Std. Error	p-value
Intercept	−2.22	2.20	0.352
Dichot	1.47	0.15	< 0.0001
r^2= 0.943
Final Model with Meteorological Data
Intercept	−11.08	3.03	0.015
Dichot	1.31	0.10	< 0.0001
Temperature	0.30	0.09	0.022
r^2 = 0.987
Full Model with Meteorological Data			(Type III)
Intercept	−8.86	28.09	0.782
Dichot	1.24	0.46	0.116
Wind speed	−0.28	0.30	0.444
Temperature	0.31	0.22	0.297
R.H.	−0.0007	0.35	0.999
Precipitation	−0.99	7.07	0.902
r^2 = 0.988

FIG. 5 Box and whisker plot of wind speed measured at different sites. Minimum, maximum, median, lower quartile, and upper quartile are shown. A plus symbol represents outliers with values greater than 1.5 times the median value.

TABLE 4 Pairwise comparison of hourly wind speed at different stations

	Airport	Airport	Airport
X-Station	(on tower)	(on tower)	(on site)
Y-Station	Airport (at site)	Residence	Residence
N	1379	738	528
Slope ± St. Err.	0.41 ± 0.01**	0.15 ± 0.01**	0.33 ± 0.01**
Intercept ± St.	1.98 ± 0.16**	−0.286 ± 0.10**	−0.76 ± 0.11**
Err., km hr^−1
r^2	0.51	0.42	0.53