Southeast PM 2.5 Data Analysis

Analysis of PM 2.5 FRM data and data for monitors in southeast Pennsylvania.

Monitor Information

Site Name County FRM Start Date FRM Sample Frequency Speciated Start Date Speciated Frequency

Lancaster Lancaster 1/1999 1/3 4/2002 1/6 Freemansburg Northampton 1/1999 1/1 NA NA Bristol Bucks 2/1999 1/3 NA NA New Garden Chester 1/2002 1/3 4/2002 1/6 Chester Delaware 1/1999 1/3 4/2002 1/6 Norristown Montgomery 2/1999 1/3 NA. NA

AMS Lab Philadelphia 2/1999 1/1 5/2006 1/6 500 Broad St Philadelphia 2/1999 1/3 to 1/1 NA. NA

Items in BOLD are within the Philadelphia-Wilmington nonattainment area.

Data Analysis:

Design Value Contribution Analysis:

Only one monitor in southeast Penns ylvania currently exceeds the annual PM 2.5 NAAQS (15.0 μ g/m 3 ). PM 2.5 annual design values for 2006 are listed in Table 1 for six FRM monitoring sites in southeast Pennsylvania. Design values across southeast Pennsylvania have remained relatively stable for most monitors over the last five years.

Table 1. Annual PM 2.5 Design Values

Site 2002-04 2003-05 04-06 Lancaster 16.8 17.5 16.3 Freemansburg 14.0 14.1 13.6 Bristol 13.9 13.9 13.2 New Garden 14.8 15.2 14.2 Chester 15.0 15.6 15.2 Norristown 13.2 12.8 12.2

AMS Lab 14.5 14.3 13.9 500 Broad St 15.4 15.0 15.0

Items in BOLD are within the Philadelphia-Wilmington nonattainment area.

The nature of the annual standard makes it di fficult to determine what causes a monitor to exceed the annual PM 2.5 standard. For a well-run monitor, between 365 to 1096 FRMmeasurements make up its annual design value. The shear number of samples makes it very difficult to determine what days (s amples) are contributing to monitor’s annual design value.

A monitor’s annual PM 2.5 design value is determined by first calculating its quarterly average. Quarterly averages are then averag ed to calculate the monitor’s average annual PM 2.5 concentration. Three consecuti ve years of average annual PM 2.5 concentrations are then averaged to determine a monitor’s annual PM 2.5 design value. Thus any one particular sample will make only a minor contribution to a monitor’s annual PM 2.5 design value.

The Pennsylvania DEP has come up with a methodology to quickly analyze a monitor’s design value and determine which measurem ents (or types of measurements) are contributing to a site’s design va lue. Each twenty-four hour PM 2.5 FRM measurement’s contribution to the monitor’s annual de sign value is calculated. FRM 24-hour concentrations are then groupe d into different sample ra nges to gauge each sample range’s contribution to the monitor’s annua l design value. Monitors then can be compared to determine which monitor sample ranges are important.

For the purposes of this analys is, contributions are determin ed such that contributions from samples less than 15.0 μ g/m 3 are negative and those samp les that are greater than 15.0 μ g/m 3 are positive. Th e break point of 15.0 μ g/m 3 represents the break-off point for the annual PM 2.5 standard. Mathematically the cont ributions for each sample range can be represented by this equation:

For values less than or equal to 15.0 μ g/m 3 :

0 < x ≤ 15

For values greater 15.0 μ g/m 3 :

15 < x < MaxContributions from several ranges of samp le concentrations then can be summed to determine a monitor’s annual de sign-value concentration. Ta ble 2 shows the results of the design-value contribution analysis for six monitors in southeast Pennsylvania. The list includes all of the PA DEP maintained monitors in the Philadelphia-Wilmington PM 2.5 nonattainment area plus the Lancaster mon itor which lies west of Philadelphia and the Freemansburg monitor which lies to the north.

Table 2. Design Value Contribution Analysis

Site 0-15.0 15.0-40.5 40.5-65.5 >65.5 Sum Lancaster -3.0663 3.7532 0.6286 0.0000 1.3155 Freemansburg -4.2393 2.5064 0.2885 0.0000 -1.4444 Bristol -4.3432 2.5612 0.0000 0.0000 -1.7820 New Garden -3.7375 2.8114 0.2304 0.0000 -0.6956 Chester -3.2745 3.3408 0.0719 0.0000 0.1000 Norristown -4.7638 1.9427 0.0000 0.0000 -2.8211

AMS Lab -3.9434 2.6133 0.2299 0.0000 -1.1000 500 Broad St -3.2481 3.0771 0.1973 0.0000 0.0000

Items in BOLD are within the Philadelphia-Wilmington nonattainment area.

The break lines in Table 2 are roughly based on the twenty-four hour AQI scale for PM 2.5 with the lower scale being cut off at 15.0 μ g/m 3 . Most of the PA DEP monitors within the Philadelphia PM 2.5 nonattainment area meet the annua l standard (except Chester). Surprisingly, there appear to be fewer days with high PM 2.5 concentrations (> 40.5 μ g/m 3 ) in the Philadelphia nonattainment area than in areas to the west (Lancaster) and north (Freemansburg). The Chester and to a lesser extent the 500 Broad Street monitors also appear to have fewer days w ith concentrations less than 15 μ g/m 3 than the other four (4) Philadelphia monitors in this analysis.

Design Value Contribution Analysis Summary:

• Only one monitor in the Philadelphia-Wilmington PM 2.5 nonattainment area exceeds the annual standard though th ere are data capture issues for the Philadelphia County monitors.

• There appear to be fewer days with high PM 2.5 concentrations (> 40.5 μ g/m 3 ) in the Philadelphia-Wilmington nonatta inment area than there are in areas to the west (Lancaster) and north (Freemansburg).

• The Chester and 500 Broad Street monitors appear to have fewer days with PM 2.5 concentrations less than 15 μ g/m 3 than other monitors in the region.Correlation Coefficient Analysis:

Correlation coefficients are a statistical m easure to determine how well two different samples track one another. There are three possibilities; the two samples react similarly, they appear to be random or th ey react oppositely. Daily FRM PM 2.5 measurements from six monitors in southeast Pennsylvania (2000- 06) were correlated with one another to determine how well the monitors tracked each other over time. PA DEP monitors were also compared with monitors to the we st and north to determine how well the Philadelphia area monitors tracked concentrations in nearby regions.

The largest distance between monitors is approximately 80 miles (between Lancaster and Bristol). The bulk of the monitors are within 30 miles of one another. There are no large terrain features in the region so airflow is generally unrestricted.

Table 3 lists the correlation coefficients fo r several FRM monitoring sites in southeast Pennsylvania. Coefficients range from 1.0 to –1.0. Correlation ranges and their meaning are broken down as follows:

1.0 to 0.667 Positive correlation (samples move in a similar direction) 0.667 to -0.667 Samples not well co rrelated (0.334 to – 0.334, random) -0.667 to –1.0 Negative correlation (sam ples move in opposite direction)

Table 3. Southeast Pennsylvania PM 2.5 Correlation Coefficients

Lancaster Freemansburg Bristol New Garden Chester Norristown Lancaster 0.8528 0.859 4 0.9211 0.8346 0.8639 Freemansburg 0.8528 0.885 5 0.8751 0.8113 0.8838 Bristol 0.8594 0.8855 0. 8915 0.8602 0.9059 New Garden 0.9211 0.8751 0.891 5 0.8928 0.9030

Chester 0.8346 0.8113 0.860 2 0.8928 0.8580 Norristown 0.8639 0.8838 0.905 9 0.9030 0.8580

AMS 500 Broad Bristol New Garden Chester Norristown AMS 0.9480 0.9346 0. 9346 0.9076 0.9159 500 Broad 0.9480 0.8985 0. 9111 0.9024 0.8792

Bristol 0.9346 0.8985 0. 8915 0.8602 0.9059 New Garden 0.9346 0.9111 0.891 5 0.8928 0.9030

Chester 0.9076 0.9024 0.860 2 0.8928 0.8580 Norristown 0.9159 0.8792 0.905 9 0.9030 0.8580

Correlation coefficients indicate that th e six monitors within the PhiladelphiaWilmington nonattainment area respond similarly. There are greater similarities in the FRM data between monitors that are relatively close together than for monitors that are far apart. Correlations also tend to be s lightly lower between monitors exceeding the annual PM 2.5 standard (Lancaster and Chester) and t hose that do meet the standard.Correlation coefficients for the Chester and Br oad Street monitors appear to be lower than any of the other monitors. This may i ndicate these monitors are behaving differently than the surrounding monitors within the nonatt ainment area. There also does not seem to be as much seasonal variability in co rrelations as was found in other areas of Pennsylvania.

Correlation Coefficient Analysis Summary:

• Correlation coefficients constructed from 2000-06 FRM data indicate all of the monitors in the Philadelphia gen erally respond in a similar fashion.

• Correlations are better between the monito rs that are close to one another.

• Correlations between Chester and the 500 Broad Street monitor are a bit lower than correlations between the oth er monitors indicating these monitors may be behaving differently than oth er monitors in the nonattainment area.

• There appears to be little change in correlations based on time of year. This is different than other areas of Pennsylvania where correlations were analyzed.

Coefficients of Divergence Analysis:

Correlation of divergence is a statistical m easure to quantify the magnitude of difference between two groups of samples. FRM samples between 2000 and 2006 were analyzed to determine the coefficients of divergence for six monitors in sout heast Pennsylvania and the Lancaster and Fremansburg monitors to the west and north respectively. Table 4 summarizes the results of this analysis. In general numbers close to zero indicate small differences in daily concentrations between monitors. Numbers close to one or above indicate significant differences in the daily PM 2.5 concentrations between the two monitors.

Table 4. Southwest Pennsylvania PM 2.5 Coefficient of Divergence

Lancaster Freemansburg Bristol New Garden Chester Norristown Lancaster 0.9632 0.766 7 0.2749 0.6090 0.6597 Freemansburg 0.9632 0.565 3 0.5752 0.9398 0.5024 Bristol 0.7667 0.5653 0. 4270 0.7206 0.3910 New Garden 0.2749 0.5752 0.427 0 0.4603 0.4160

Chester 0.6090 0.9398 0.720 6 0.4603 0.7349 Norristown 0.6597 0.5024 0.391 0 0.4160 0.7349

AMS 500 Broad Bristol New Garden Chester Norristown AMS 0.3274 0.2023 0. 2703 0.4149 0.2343 500 Broad 0.3274 0.4952 0. 3351 0.3389 0.6003

Bristol 0.2023 0.4952 0. 4270 0.7206 0.3910 New Garden 0.2703 0.3351 0.427 0 0.4603 0.4160

Chester 0.4149 0.3389 0.720 6 0.4603 0.7349 Norristown 0.2343 0.6003 0.391 0 0.4160 0.7349The results of this analysis indicate there ar e some significant diffe rences in daily fineparticulate concentrations across southeast Pennsylvania. In pa rticular there are significant differences in daily monitor valu es between the Philadelphia nonattainment area and the Lancaster and Freemansburg mon itors, with the exception of the Lancaster and New Garden monitors, which surprisi ngly showed little difference in daily concentrations. Again there are significant di fferences in values between the Chester and 500 Broad Street monitors and the other monitors in the Philadelphia-Wilmington nonattainment area. This is similar to patte rns observed in the correlation coefficient analysis and supports the contention that th ese monitors are behaving differently than other monitors in the nonattainment area. Coefficients of divergence values do not appear to vary much by time of year. This differs for from other areas of Pennsylvania that appear to show some seasonal variability

Coefficients of Divergence Analysis Summary:

• Coefficients of Divergence construc ted from 2000-06 FRM data indicate there are some significant differences in daily PM 2.5 concentrations betweenthe Chester and 500 Broad Street and other monitors in the PhiladelphiaWilmington nonattainment area.

• Coefficients of Divergence do not appear to vary much by season. This differs from other areas of Pennsylvania that have been analyzed.