Local versus Non-local Influences of PM2.5

1
Local versus Non-local Influences of PM2.5

• Background and Rationale
• Influence of wind speed on local concentrations
• Mid-Atlantic Rural Sites PM2.5 Vs Surface Wind
  Speed
• Mid-Atlantic Urban Sites PM2.5 Vs Surface Wind
  Speed
• Seasonal Urban-Rural Difference
• Conclusions
• Resource Links

Contact Bret Schichtel, Bret_at_mecf.wuslt.edu
2
Background and Rationale

• At any given location the PM concentration is the
  result of the PM mass originating from non-local
  sources transported in and PM mass originating
  from local sources. What is local??
• The local/non-local contributions depend on
  emissions, transport and aerosol formation and
  removal processes, so there is no typical
  non-local concentration.
• Quantifying the local contributions identifies
  the part of the PM problem that can be controlled
  locally.

3
Influence of wind speed on local concentrations

• The concentration C is equal to the sum of the
  background (Co) and local contribution (QL/UH)
• Assuming a fixed source region length (L),
  emission rate (Q) and mixing height (H) as the
  wind speed (U) increases the concentration from
  the local sources decreases asymptotically
  approaching the background concentration.

4
PM2.5 Vs Surface Wind Speed at Urban and Rural
Sites
The PM2.5 at the urban sites during the cold
season (Nov - March) decline sharply (60) with
increasing wind speeds compared to the rural
sites (30). This implies the urban PM2.5 is
dominated by local sources.
5
Washington, DC Seasonal PM2.5 Urban Excess

• The excess PM2.5 at Washington DC ranges from gt10
  mg/m3 (70) in the winter to 1-2 mg/m3 (10) in
  the summer.

6
Phoenix, AZ Seasonal PM2.5 Urban Excess

• The Phoenix excess PM2.5 ranges from 11 - 16
  mg/m3 (80) in the winter to 3 mg/m3 (30) in
  the summer.

7
Conclusions

• Mid-Atlantic and Southwest urban centers are
  dominated by local sources during the winter.
• At the Mid-Atlantic urban sites, the summer
  local sources contribute about 10 of the PM mass
  compared to up to 70 in the winter.
• At the urban Southwest, the local sources
  contribute about 30 of the summertime PM mass
  compared to about 80 in the winter.

8
Resource Links

• Workbook Table of Contents
• Comment and Feedback Page
• Applications / Reports
• Data sets used in the Applications
• Methods and tools used in the Applications