# Nature of PM2.5 in the San Joaquin Valley

Karen Magliano California Air Resources Board Technical Symposium April 27, 2012

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# PM Characterization

2

# High PM2.5 Levels Occur In Winter

 

### PM2.5 builds up over several days or weeks (episode)
 

### Episodes generally occur during periods with:

• 

### stagnation

• 

### cool temperatures

• 

### high humidity

• 

### low mixing depths 0 5 10 15 20 25 30 35 40

1 2 3 4 5 6 7 8 9 10 11 12PM2.5 Concentration (μg/m3)

Month Bakersfield

- California Monthly Average

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# Challenge of 24

- Hour Standard

 

## Focuses on most severe days

 

## Strongly influenced by meteorology

 

## Impacts of episodic emissions such as residential wood burning 4

# Monitored PM2.5 Chemical Components

Ammonium Nitrate

67% Ammonium Sulfate 9% Organic Carbon 16% Elemental

Carbon 5% Geological 2% Elements 1% 2008 - 2010 Peak Day Composition Bakersfield

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# Monitored PM2.5 Chemical Components

Ammonium Nitrate

51%

Ammonium Sulfate 6% Organic Carbon 33% Elemental

Carbon 7% Geological 1% Elements 2% 2008 - 2010 Peak Day Composition Fresno

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# Monitored Concentrations of Key Species

0 5 10 15 20 25 30 35

Ammonium Nitrate Carbon Bakersfield FresnoConcentration (μg/m3)

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# Ammonium Nitrate Formation (Excess Ammonia)

NH3 

# +

+ + NOx

NOx

NOx NH3 NH3

NH3

NH3 Atmospheric Reactions

(NH 4 

### NO 3 

### ) Ammonium Nitrate

Ammonium Nitrate
Ammonium Nitrate

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# Ammonium Nitrate Formation ( NOx Control)

NH3 

# +
+ NOx

NOx

NH3 NH3

NH3

NH3 Atmospheric Reactions

(NH 4 

### NO 3 

### ) Ammonium Nitrate

Ammonium Nitrate

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# Measured Ammonia Much More Abundant than Nitric Acid

10 -10 0 10 20 30 40 50 60

-2 0 2 4 6 8 10 12 14 16 18 HNO3 Concentration (ug-N/m3)NH3 Concentration (ug-N/m3)

1:1 Line Angiola Monitoring Site

– CRPAQS Field Study

# Linkage to Modeling

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# Role of Air Quality Data in Attainment Demonstration

 

# Calculate design values
 

# Select modeling base year
 

# Weight of Evidence

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# Design Value Calculation

 

# Defines air quality starting point
 

# Uses measured PM2.5 concentrations
 

# Based on 98 th 

# percentile (generally between the 2 nd 

# and 8 th 

# highest value)
 

# Calculated as 3

- year average

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# Selecting Base Year For Planning

 

# Appropriate base year considers air quality and meteorology  

# Base year with stagnant meteorology is a conservative approach  

# Attainment demonstration estimates change in design value between base year and attainment year

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# 2007 Base Year

 

## 2007 meteorology one of most conducive to PM2.5 formation  

## Includes various types of meteorology conducive to high PM2.5  

## 2007 PM2.5 98 th 

## percentile concentrations highest in recent years  

## Excludes influence of 2008 wild fires

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# Design Values*

0 10 20 30 40 50 60 70 80PM2.5 Design Value (μg/m3)

2007 2011 * Year assigned to design value reflects last year of three year period 16

# Weight of Evidence

 

# Attainment demonstration based on weight of evidence approach  

# Collective assessment of control approach based on:

• 

## air quality grid modeling

• 

## source - receptor modeling

• 

## observed air quality trends

• 

## emission trends

• 

## field/modeling studies

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# Effectiveness of Wood Burning Controls

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# Effectiveness of NOx Controls

19 0 2 4 6 8 10 12

0 100 200 300 400 500 600

2002 2003 2004 2005 2006 2007 2008 2009 2010Ammonium Nitrate (ug/m3)NOx Emissions (tons/day)

NOx Emissions Ammonium Nitrate (Fresno)

# Future NOx Emission Trends

0 100 200 300 400 500 600

2007 2014 2019Emissions (tons/day)

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