Investigation of High Particulate Matter Episodes in the Nogales Border Region

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Investigation of High Particulate Matter Episodes
in the Nogales Border Region
Nabin Upadhyay1, Qinyue Sun1, Jonathan O. Allen1,
Pierre Herckes1 Alberto Mendoza2, Ana Y. Vanoye2
1- Arizona State University 2- Instituto
Tecnologico y de Estudios Superiores de Monterrey
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Outlines

• Objectives
• Chemical characterization of PM
• Data analysis
• Modeling dust emissions
• Outlook

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Background
Nogales, AZ/Nogales, Sonora have high PM10 and
PM2.5 concentrations Frequent violation of
PM10 standards, more violation in Sonora ADEQ and
SCERP have funded studies in Nogales since
1990s unpaved roads (PM10) and motor vehicles
(PM2.5) Major infrastructure upgrades for
Nogales, Sonora paving of local roads, new
highway/border post Less exceedences but still
exceedences Winter season has more
high-pollution events Change in sources?
(population growth?) Missing sources?
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Objectives

• What are trace metal concentrations in PM2.5 and
  PMgt2.5 in Nogales, AZ?
• What are the factors influencing trace metals in
  PM2.5 and PMgt2.5 in Nogales, AZ?
• Can air pollution models predict these high PM
  episodes?
• How have these concentrations evolved since the
  studies in the 1990s?

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Field study December 2005/January 2006
Streaker,SEM Sampler, SMPS Inlet, AMS Inlet ASU
6-h ChemVol ASU
24-h ChemVol ASU
24-h HiVol ASU
PM10BAM
PM2.5BAM
PM2.5FRM ADEQ
PM10FRM ADEQ
6-h Filters ASU
24-h Filters ASU
Rooftop of post office Nogales, AZ
Funded by Arizona Department of Environmental
Quality ADEQ
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PM concentrations
150 µg m-3
65 µg m-3
High PM concentrations throughout the study
BAMS Baron Advance Meteorological Systems
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Hourly variation of PM Concentration
Evening hours
Morning hours
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Joint ADEQ study
Identification of Particulate Matter Sources in
the Nogales Border Region Using Electron
Microscopy and Organic Tracer Compounds Dr. J.
Allen, PI Dr. J. Anderson and P. Herckes, Co-PIs

• Detailed Characterization
• of High PM events
• Identify sources of PM
• using
• Electron microscopy
• Molecular markers

• Final report is in progress.

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Organic carbon source apportionment
Biomass (wood, trash,..)
PM2.5 Jan 6 (24h)
PM2.5 Jan 10 (24h)
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Metal analysis
Development and validation of a new protocol to
determine metal concentrations in PM collected on
substrates optimized for carbonaceous aerosol
studies Complete dissolution of
filter Quantification using ICP-MS
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Analytical scheme
Temperature program
Upadhyay et al. Analytical and Bioanalytical
Chemistry (Submitted)
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Trace element concentrations
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Data analysis

• Using statistical tools
• Principal Component Analysis
• Hierarchical Cluster Analysis
• Investigate variability with particle size PM10
  vs PM2.5
• Compare 2005/06 with historical data

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Factor analysis
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Factor analysis
soil
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Factor analysis
vehicles?
oil?
combustion
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Factor analysis
Trash burning?
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Factor analysis
?
Soil and combustion
Trash burning?
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Factor analysis
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Hierarchical cluster analysis
Identify groups of elements similar to each
other, but different from each other
Nogales 2005/2006 PM2.5 Similar results for the
past data
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2
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Air pollution modeling (ITESM team)

• Can models predict high PM events?
• underlying hypothesis, PM10 dust derived
• Simplified outline of modeling approach

The Fifth-Generation PSU/NCAR Mesoscale Modeling
System MM5
Single-event Wind Erosion Evaluation Program
(SWEEP)
Meteorological parameters
Dust emissions
California Institute of Technology CIT airshed
model
difficulty getting input data (soil use in Mexico)
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Modeling domain for dust emissions (35x35 grid of
4kmx4km)
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Soil re-suspension in the Nogales domain
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Model vs observation
January 6, 2006
Some events are very well reproduced (e.g.
morning) Some events are completely missed
sub-grid (local) events ?
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Comparison of 2005/06 studies with prior
work Change in sources?

• Metal concentrations available for winter of
  1999-2001.
• PM2.5 metals order of magnitude higher in winter
  05/06
• PMgt2.5 lower in 05/06 than PM10-2.5 in 99/01
• PCA, HCA similar results for the 99/01 and 05/06
  
• Winter season suggests no major change in sources
• However
• Inconsistencies in the past data
• 05/06 is a one-period campaign with consistently
  high PM
• 05/06 every other day sampling vs every 6 days
  in 99/01

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Summary

• Development of a novel method for trace metal
  analysis in PM
• High metal concentrations in Nogales, AZ (PM2.5
  and PM10)
• Main sources of metals soil and combustion
  processes
• Comparison to older dataset (1999-2001)
• No substantial changes in sources
• Modelling studies confirmed high impact of
  windblown dust
• Model predicted some PM10 events but missed
  others
• Importance of sub-grid (small scale) processes

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Future research?
Need of a more comprehensive picture in terms of
time and space Time longer studies high and
low PM events better time resolution morning and
evening peaks Temporal changes in PM
composition/sources? Space complex topography
spatial variability of sources is sampling
location really representative? Spatial changes
in PM composition/sources?
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Acknowledgements

• Dr. James Anderson (ASU), co-PI on the ADEQ
  study
• Dr. Panjai Prapaipong (ASU), ICP-MS
• ADEQ, especially Randy for help with logistics

Funding provided by

• Southwest Consortium for Environmental Research
  and Policy
• Arizona Department of Environmental Quality