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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 l.jpg

Wilmington Air Quality StudyModeling for Neighborhood Assessment

Todd Sax

Vlad Isakov

September 12, 2002

California Air Resources Board

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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, 2002California Air Resources Board

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  • 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)

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Wilmington Study Domain

September 12, 2002California Air Resources Board

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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, 2002California Air Resources Board

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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

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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, 2002California Air Resources Board

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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

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Emissions Inventory - Facilities

  • 195 facilities in CEIDARS

  • Corrected geo-locations

  • Integration with existing HRAs

  • Improved release locations and parameters

  • Sampled for data quality evaluation

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Emissions Inventory - Facilities

  • Integrating inventory with GIS platform

  • 1 km or 100m grid cells

  • Drill-in capability on selected sources

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Emissions Inventory - On-Road Sources

Wilmington Road Links, SCAG Models

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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, 2002California Air Resources Board

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Wilmington Wind Patterns

Summer - daytime

Summer - night-time

Long Beach, Aug./Sept.

  • Typical coastal wind patterns

  • Daytime southerly and westerly flow

September 12, 2002California Air Resources Board

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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, 2002California Air Resources Board

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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, 2002California Air Resources Board

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Tracer Study - Dispersion Example

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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, 2002California Air Resources Board

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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

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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, 2002California Air Resources Board

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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, 2002California Air Resources Board

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