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Wilmington Air Quality Study Modeling for Neighborhood Assessment. Todd Sax Vlad Isakov September 12, 2002. California Air Resources Board. Neighborhood Assessment. Program Objective

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wilmington air quality study modeling for neighborhood assessment

Wilmington Air Quality StudyModeling for Neighborhood Assessment

Todd Sax

Vlad Isakov

September 12, 2002

California Air Resources Board

neighborhood assessment
Neighborhood Assessment
  • Program Objective
    • “Develop source-receptor based, cumulative impact/risk assessment methodologies suitable for evaluating neighborhood-scale air pollution impacts and for comparing neighborhood exposures within a region” (NAP Work Plan)
    • Develop tools for evaluating local scale impacts and targeting risk reduction strategies

September 12, 2002 California Air Resources Board



  • Identified by MATES-II as one of the most impacted areas of the Los Angeles region
  • Located near
    • Freeways
    • Refineries
    • Ports
    • Local Traffic
    • Manufacturing
    • Local Facilities

MATES-II Health Risk


September 12, 2002 (source: MATES-II, pg. ES-12)


Wilmington Study Domain

September 12, 2002 California Air Resources Board


Wilmington Air Quality Study

  • Project Objectives
    • Improve assessment methodologies
    • Evaluate model results
    • Develop recommendations for policy development
    • Communicate results and risks to the public
  • Project Components
    • Emissions Inventory
    • Dispersion Modeling
    • Model Evaluation
    • Health Risk Assessment
    • Exposure Assessment

September 12, 2002 California Air Resources Board


Wilmington Neighborhood Assessment - Conceptual Plan

  • Emissions
  • Point Sources
  • Industrial
  • Metal platers
  • Refineries
  • Manufacturing Facilities
  • Other sources: Cr6+, DPM
  • Commercial
  • Gas stations
  • Dry cleaners
  • Autobody shops
  • Warehouses
  • Industrial diesel
  • Welding facilities
  • On-Road Sources
  • Link-based inventory
  • Evaluate with vehicle
  • counts
  • Off-Road Sources
  • Marine - Port, ARB
  • Dockside - Port, ARB
  • Railroads - ARB, Port
  • Health Risk
  • Modeling Results
  • Inhalation health risk
  • calculation
  • Multi-media health risk
  • calculation
  • Health risk assessment
  • Exposure
  • Microscale Modeling
  • ISCST3
  • Regional Modeling
  • CALGRID and/or CMAQ
  • Model Evaluation
  • Tracer Studies
  • June 2003
  • Powerplant elevated release
  • Toxics Monitoring
  • Multiple sites, June 2003
  • Focus on diesel particulate
  • Coordination with POLA
  • Uncertainty Assessment
  • Focus on diesel and Cr6+
  • Estimate range of pollutant
  • concentrations possible using
  • Monte Carlo techniques
  • Inventory Analysis
  • Focus on diesel and Cr6+
  • Examine by source and release point
  • Estimate range of possible emissions
  • using Monte Carlo techniques
  • Compile by release location

Emissions Inventory

  • Goal: comprehensive emissions inventory
    • Industrial and Commercial Facilities
      • Comparing multiple inventory sources (Federal, State, Local)
      • Conducting on-site surveys of large and small facilities
    • On-Road Mobile Sources
      • Building link-based inventory using SCAG light and heavy duty travel demand models
    • Off-Road Mobile Sources
      • Supplementing off-road inventories with facility-specific emissions identified by survey
      • Working with Ports of Los Angeles and Long Beach in inventory development for sources of diesel PM
      • Integrating spatially allocated off-road emissions from multiple sources

September 12, 2002 California Air Resources Board


Emissions Inventory - Facilities

  • Over 2500 businesses in modeling domain
  • 195 facilities in CEIDARS
  • Multiple inventory databases
  • 240 facilities surveyed, ~50% have emissions
  • More surveys planned

Emissions Inventory - Facilities

  • 195 facilities in CEIDARS
  • Corrected geo-locations
  • Integration with existing HRAs
  • Improved release locations and parameters
  • Sampled for data quality evaluation

Emissions Inventory - Facilities

  • Integrating inventory with GIS platform
  • 1 km or 100m grid cells
  • Drill-in capability on selected sources

Emissions Inventory - On-Road Sources

Wilmington Road Links, SCAG Models


Air Quality Modeling

  • Goal
    • Develop and evaluate methodologies to estimate annual average concentrations of pollutants released from multiple sources on a neighborhood scale
  • Micro-scale modeling
    • Focus on air toxics with defined unit risk factors or reference exposure levels and particulate
  • Regional modeling
    • Focus on southern California
    • 30 toxic pollutants
    • Photochemical models (e.g. CMAQ and/or CALGRID)

September 12, 2002 California Air Resources Board


Wilmington Wind Patterns

Summer - daytime

Summer - night-time

Long Beach, Aug./Sept.

  • Typical coastal wind patterns
  • Daytime southerly and westerly flow

September 12, 2002 California Air Resources Board


Model Evaluation - Overview

  • Assess accuracy of model results
    • Tracer studies
      • Received new contract between ARB, CEC, UCR to conduct a tracer release from an elevated stack in Wilmington
      • Use existing tracer data to evaluate model performance and improve model algorithms
    • Supplemental monitoring
      • Focus on diesel particulate, but there is currently no acceptable method for measurement
    • Uncertainty analysis
      • Assess uncertainty for a subset of facilities in the modeling domain: Diesel PM (DPM) and Hexavalent Chromium (CrVI) emissions

September 12, 2002 California Air Resources Board


Model Evaluation - Tracer Study

  • Model performance evaluation - ensure model predictions are reliable
    • Develop database of tracer concentrations
    • Extend existing tracer database
  • Wilmington - elevated release (stack)
    • Improve dispersion algorithm
      • urban boundary layer conditions
      • large vertical gradients in wind speed and turbulence are present
    • Goal: improve model algorithms, incorporate into dispersion models (such as AERMOD)
  • Site: not yet chosen. Date: June 2003.

September 12, 2002 California Air Resources Board


Model Evaluation - Toxics Monitoring

  • Diesel PM is major inhalation risk in Wilmington
    • No accepted methodology for measuring DPM
    • Elemental carbon as a surrogate does not work well in all cases
    • Major CMB studies provide conflicting results
  • Likely Approach - CMB Analysis with Polycyclic Aromatic Hydrocarbon measurement
    • Multiple sites over several weeks, June 2003.
    • Measure PM 2.5, OC/EC, SVOC PAH, elements
    • Evaluate differences between sites, between days, and correlation between pollutants
    • Looking for additional funding to expand study

September 12, 2002 California Air Resources Board


Model Evaluation - Uncertainty Analysis

  • Provide context to estimated pollutant concentrations - evaluate assumptions
    • Uncertainty sources: emissions, spatial allocation of emissions, model options and release parameters, conceptual uncertainty in model physics
    • Approach
      • Focus on selected sources: CrVI and DPM
      • Evaluate range of possible emissions from each source through survey, databases, analysis of emission factors
      • Determine specific conditions of each emission release
      • Estimate range of inter-annual variability in meteorology
      • Assess range of acceptable model options and conduct sensitivity analysis
      • Use Monte Carlo statistical techniques to estimate confidence limits in modeling results

Health Risk Assessment

  • Evaluate inhalation health risk
  • Investigate alternative assessment methods
    • Goal: Provide perspective to inhalation health risk
    • Some pollutants have important multipathway component
      • Estimate differences in predicted health risks through evaluating multipathway contributions for selected pollutants
    • True inhalation exposure is a function of the amount of pollutant people breathe.
      • People spend time in microenvironments
      • Microenvironmental pollutant concentrations may be different than outdoor, ambient concentrations
      • May be possible to use existing data and models to compare ambient exposure to total exposure for selected pollutants

September 12, 2002 California Air Resources Board


Expected Conclusions

  • Answer relevant policy questions
    • Which inventory sources are most important?
    • Do commercial facilities impact cumulative risk? If so which ones?
    • Can on-road emissions be accurately allocated to individual streets? If not, what can be done?
    • Which models are most appropriate for neighborhood assessment? Do approaches vary by pollutant?
    • How should models be improved?
    • How reliable are modeling results?
    • What is the impact of exposure to ambient air pollution relative to estimated personal exposure?

September 12, 2002 California Air Resources Board