Appendix D

Natural Sources
ARB Almanac 2013 – Appendix D: Natural Sources 

Appendix D

Appendix D: Natural Sources

 Introduction .................................................................................................................................................................. Biogenic Sources ........................................................................................................................................................... Geogenic Sources .......................................................................................................................................................... Wildfires ........................................................................................................................................................................
ARB Almanac 2013 – Appendix D: Natural Sources 

Appendix D

 D-1 Statewide Natural Source Emissions .........................................................................................................

 D-2 Natural Source Emissions - Biogenic Sources ............................................................................................

 D-3 Natural Source Emissions - Geogenic Sources...........................................................................................

 D-4 Natural Source Emissions - Wildfires ........................................................................................................

List of Tables

 D-1 Statewide Biogenic Emissions ....................................................................................................................

 D-2 Wildfires 2001-2010 ..................................................................................................................................

List of Figures
ARB Almanac 2013 – Appendix D: Natural Sources 

Appendix D

Introduction

Appendix D contains estimates of emissions from natural processes 

occurring in terrestrial, marine, or aquatic ecosystems. Natural source air emissions include a variety of compounds and occur as a result of geologic or meteorological activity (such as petroleum seeps, or 

wildfires), or living processes by flora and fauna (such as emissions 

from vegetation foliage, or from soil microbes). Emissions resulting from anthropogenic activities, such as soil ammonia (NH3) emissions 

resulting from fertilizer application, burning of agricultural crop residues, prescribed burning of natural areas, wildfires that are managed for resources benefit, and windblown dust from crop fields and pastures are provided in Chapter 2. Windblown dust emissions from dry lake beds have not been included.For this edition of the Almanac, categories of natural sources include geogenic (petroleum seeps) and biogenic (vegetation) sources, and 

wildfires. Other categories may be added in future editions. Natural 

emissions are strongly affected by seasonal influences on factors such as temperature and moisture conditions, or wind regimes. Emissions during “peak season” are often orders of magnitude greater than emissions during dormant periods. Emissions for some categories (for example see Figure D-1) are therefore reported with respect to time of 

year, in addition to annual averages. Emissions can fluctuate greatly 

from year-to-year due to variation in meteorology or land cover/land use. Methods for forecasting future natural emissions due to changes in climate or land cover/land use remain in the realm of on-going scientific research, and have not been applied in this edition of the 

Almanac.

Category VOC NOX Biogenic Sources 2067 0 Geogenic Sources 31 0 

Wildfires 335 27 

Natural Sources Total 2433 27 

StatewideNatural Source Emissions (tons/day, a

* Biogenic and geogenic emissions are not year-specific.** Wildfire emissions reflect 10-year averages.

Table D-1 
ARB Almanac 2013 – Appendix D: Natural Sources 

Appendix D

Biogenic volatile organic compounds (BVOCs) are emitted into the atmosphere from terrestrial ecosystems such as vegetation. BVOCs include isoprene, monoterpenes, methylbutenol (MBO), and other biogenic VOCs (OVOCs). These compounds are of interest because of their roles in atmospheric chemistry and climate. In the presence of anthropogenic NOx compounds, isoprene has been found to play 

a significant role in ozone chemistry. Monoterpenes and MBO are moderately reactive. OVOCs are a general category comprised of less reactive compounds, such as methanol and acetone. Isoprene, monoterpenes, MBO, and a fraction of the OVOCs are considered as reactive organic gas (ROG).Plant BVOC emissions vary by compound and by orders of magnitude among various plant species. BVOCs play roles in plant physiology and chemical defense from pests and plant diseases. BVOC emissions are strongly influenced by environmental factors such as temperature and sunlight. Biophysical and environmental mechanisms controlling the synthesis and emission of isoprene, monoterpenes, and MBO have been studied across a variety of plant species and landscapes. Less is known about OVOCs. As a result, the BVOC research community has developed BVOC emission models, which have been routinely applied by the climate research, air quality, and emissions modeling community. A statewide model was developed to estimate BVOC emissions from vegetation over the course of a calendar year. The model runs at a 4 km x 4 km spatial resolution and generates hourly emissions of isoprene, monoterpenes, MBO, and OVOCs. Emissions from vegetation were estimated from plant species leaf mass and emission factors, and environmental adjustment algorithms representing light and temperature dependence of BVOC emissions. Leaf mass density estimates, used to scale emissions from leaf to landscapes, were based on geographic information system (GIS) land use/land cover databases, species leaf weight factors, and monthly satellite leaf area index (LAI) 

Biogenic Sources

data. Temporal and spatial variation in monthly estimates of leaf mass densities perature. The annual statewide emission ROG) is estimated to be over 750,000 to

isoprene, 30 percent MBO, 24 percent m

OVOC. As shown in Figure D-1, the major

produced during the ozone season (May 

Statewide Biogenic Em

0

100020003000400050006000

JAN FEB MAR APR MAY JUN JU

tons ROG/day

Figure D-1 
ARB Almanac 2013 – Appendix D: Natural Sources 

Appendix D

Natural Source Emissions - Biogenic Sources

(tons/day, annual average)

Table D-2 

COUNTY AIR BASIN DISTRICT VOCAlameda San Francisco Bay Area Bay Area AQMD 11Alpine Great Basin Valleys Great Basin Unifi ed APCD 9Amador Mountain Counties Amador County APCD 15Butte Sacramento Valley Butte County AQMD 41Calaveras Mountain Counties Calaveras County APCD 38Colusa Sacramento Valley Colusa County APCD 22Contra Costa San Francisco Bay Area Bay Area AQMD 11Del Norte North Coast North Coast Unifi ed AQMD 24El Dorado Lake Tahoe El Dorado County APCD 2El Dorado Mountain Counties El Dorado County APCD 49Fresno San Joaquin Valley San Joaquin Valley Unifi ed APCD 63Glenn Sacramento Valley Glenn County APCD 17Humboldt North Coast North Coast Unifi ed AQMD 81Imperial Salton Sea Imperial County APCD 3Inyo Great Basin Valleys Great Basin Unifi ed APCD 7Kern Mojave Desert Kern County APCD 23Kern San Joaquin Valley San Joaquin Valley Unifi ed APCD 18Kings San Joaquin Valley San Joaquin Valley Unifi ed APCD 4Lake Lake County Lake County AQMD 55Lassen Northeast Plateau Lassen County APCD 56Los Angeles Mojave Desert Antelope Valley AQMD 6Los Angeles South Coast South Coast AQMD 30Madera San Joaquin Valley San Joaquin Valley Unifi ed APCD 38Marin San Francisco Bay Area Bay Area AQMD 7Mariposa Mountain Counties Mariposa County APCD 35Mendocino North Coast Mendocino County AQMD 117Merced San Joaquin Valley San Joaquin Valley Unifi ed APCD 6Modoc Northeast Plateau Modoc County APCD 54Mono Great Basin Valleys Great Basin Unifi ed APCD 21Monterey North Central Coast Monterey Bay Unifi ed APCD 50
ARB Almanac 2013 – Appendix D: Natural Sources 

Appendix D

COUNTY AIR BASIN DISTRICT VOCNapa San Francisco Bay Area Bay Area AQMD 26Nevada Mountain Counties Northern Sierra AQMD 36Orange South Coast South Coast AQMD 9Placer Lake Tahoe Placer County APCD 1Placer Mountain Counties Placer County APCD 26Placer Sacramento Valley Placer County APCD 7Plumas Mountain Counties Northern Sierra AQMD 43Riverside Mojave Desert Mojave Desert AQMD 0Riverside Mojave Desert South Coast AQMD 0Riverside Salton Sea South Coast AQMD 7Riverside South Coast South Coast AQMD 22Sacramento Sacramento Valley Sacramento Metropolitan AQMD 10San Benito North Central Coast Monterey Bay Unifi ed APCD 17San Bernardino Mojave Desert Mojave Desert AQMD 6San Bernardino South Coast South Coast AQMD 15San Diego San Diego San Diego County APCD 67San Francisco San Francisco Bay Area Bay Area AQMD 1San Joaquin San Joaquin Valley San Joaquin Valley Unifi ed APCD 8San Luis Obispo South Central Coast San Luis Obispo County APCD 32San Mateo San Francisco Bay Area Bay Area AQMD 7Santa Barbara South Central Coast Santa Barbara County APCD 35Santa Clara San Francisco Bay Area Bay Area AQMD 29Santa Cruz North Central Coast Monterey Bay Unifi ed APCD 5Shasta Sacramento Valley Shasta County AQMD 166Sierra Mountain Counties Northern Sierra AQMD 17Siskiyou Northeast Plateau Siskiyou County APCD 159Solano Sacramento Valley Yolo/Solano AQMD 4Solano San Francisco Bay Area Bay Area AQMD 3Sonoma North Coast Northern Sonoma County APCD 23Sonoma San Francisco Bay Area Bay Area AQMD 10

Natural Source Emissions - Biogenic Sources

(tons/day, annual average) (Cont)Table D-2 (Cont)
ARB Almanac 2013 – Appendix D: Natural Sources 

Appendix D

COUNTY AIR BASIN DISTRICT VOCStanislaus San Joaquin Valley San Joaquin Valley Unifi ed APCD 12Sutter Sacramento Valley Feather River AQMD 3Tehama Sacramento Valley Tehama County APCD 66Trinity North Coast North Coast Unifi ed AQMD 118Tulare San Joaquin Valley San Joaquin Valley Unifi ed APCD 61Tuolumne Mountain Counties Tuolumne County APCD 46Ventura South Central Coast Ventura County APCD 26Yolo Sacramento Valley Yolo/Solano AQMD 15Yuba Sacramento Valley Feather River AQMD 15

Natural Source Emissions - Biogenic Sources

(tons/day, annual average) (Cont)Table D-2 (Cont) * Biogenic emissions are not year-specific.
ARB Almanac 2013 – Appendix D: Natural Sources 

Appendix D

Petroleum gas and oil seeps occur naturally in California and have been active for millennia. Oil and gas seeps form where oil or natural gas emerge from subsurface sources to the ground or water surface. Seeps are associated with water springs in which oil floats to the surface of the water, and gas bubbles out into the atmosphere. Large seeps may be comprised of nearly pure oil, asphaltum, or semisolid bitumen. Most seeps are mixed with varying amounts of sand, clay, and biomass debris. Terrestrial seep flows vary with the seasons, with elevated flows occurring during warm weather. Seismic activity can create new seeps or cause increased flows from existing seeps. Major marine seeps are located off the coast of Santa Barbara County. Other seeps occur in regions of oil and gas production throughout the state.

Geogenic Sources
ARB Almanac 2013 – Appendix D: Natural Sources 

Appendix D

Natural Source Emissions - Geogenic Sources

(tons/day, annual average)Table D-3 

COUNTY AIR BASIN DISTRICT VOC NH3Alameda San Francisco Bay Area Bay Area AQMD 0 0Alpine Great Basin Valleys Great Basin Unifi ed APCD 0 0Amador Mountain Counties Amador County APCD 0 0Butte Sacramento Valley Butte County AQMD 0 1Calaveras Mountain Counties Calaveras County APCD 0 1Colusa Sacramento Valley Colusa County APCD 0 0Contra Costa San Francisco Bay Area Bay Area AQMD 0 0Del Norte North Coast North Coast Unifi ed AQMD 0 1El Dorado Lake Tahoe El Dorado County APCD 0 0El Dorado Mountain Counties El Dorado County APCD 0 1Fresno San Joaquin Valley San Joaquin Valley Unifi ed APCD 0 2Glenn Sacramento Valley Glenn County APCD 0 0Humboldt North Coast North Coast Unifi ed AQMD 0 3Imperial Salton Sea Imperial County APCD 0 1Inyo Great Basin Valleys Great Basin Unifi ed APCD 0 3Kern Mojave Desert Kern County APCD 0 1Kern San Joaquin Valley San Joaquin Valley Unifi ed APCD 0 1Kings San Joaquin Valley San Joaquin Valley Unifi ed APCD 0 0Lake Lake County Lake County AQMD 0 1Lassen Northeast Plateau Lassen County APCD 0 2Los Angeles Mojave Desert Antelope Valley AQMD 0 0Los Angeles South Coast South Coast AQMD 0 1Madera San Joaquin Valley San Joaquin Valley Unifi ed APCD 0 1Marin San Francisco Bay Area Bay Area AQMD 0 0Mariposa Mountain Counties Mariposa County APCD 0 1Mendocino North Coast Mendocino County AQMD 0 2Merced San Joaquin Valley San Joaquin Valley Unifi ed APCD 0 0Modoc Northeast Plateau Modoc County APCD 0 2Mono Great Basin Valleys Great Basin Unifi ed APCD 0 1Monterey North Central Coast Monterey Bay Unifi ed APCD 0 1
ARB Almanac 2013 – Appendix D: Natural Sources 

Appendix D

COUNTY AIR BASIN DISTRICT VOC NH3Napa San Francisco Bay Area Bay Area AQMD 0 0Nevada Mountain Counties Northern Sierra AQMD 0 1Orange South Coast South Coast AQMD 0 0Placer Lake Tahoe Placer County APCD 0 0Placer Mountain Counties Placer County APCD 0 1Placer Sacramento Valley Placer County APCD 0 0Plumas Mountain Counties Northern Sierra AQMD 0 2Riverside Mojave Desert Mojave Desert AQMD 0 0Riverside Mojave Desert South Coast AQMD 0 1Riverside Salton Sea South Coast AQMD 0 1Riverside South Coast South Coast AQMD 0 1Sacramento Sacramento Valley Sacramento Metropolitan AQMD 0 0San Benito North Central Coast Monterey Bay Unifi ed APCD 0 0San Bernardino Mojave Desert Mojave Desert AQMD 0 5San Bernardino South Coast South Coast AQMD 0 0San Diego San Diego San Diego County APCD 0 1San Francisco San Francisco Bay Area Bay Area AQMD 0 0San Joaquin San Joaquin Valley San Joaquin Valley Unifi ed APCD 0 0San Luis Obispo South Central Coast San Luis Obispo County APCD 0 1San Mateo San Francisco Bay Area Bay Area AQMD 0 0Santa Barbara Outer Continental Shelf Santa Barbara County APCD 9 0Santa Barbara South Central Coast Santa Barbara County APCD 18 1Santa Clara San Francisco Bay Area Bay Area AQMD 0 1Santa Cruz North Central Coast Monterey Bay Unifi ed APCD 0 0Shasta Sacramento Valley Shasta County AQMD 0 2Sierra Mountain Counties Northern Sierra AQMD 0 1Siskiyou Northeast Plateau Siskiyou County APCD 0 4Solano Sacramento Valley Yolo/Solano AQMD 0 0Solano San Francisco Bay Area Bay Area AQMD 0 0Sonoma North Coast Northern Sonoma County APCD 0 1

Natural Source Emissions - Geogenic Sources

(tons/day, annual average) (Cont)

Table D-3 (Cont)
ARB Almanac 2013 – Appendix D: Natural Sources 

Appendix D

COUNTY AIR BASIN DISTRICT VOC NH3Sonoma San Francisco Bay Area Bay Area AQMD 0 0Stanislaus San Joaquin Valley San Joaquin Valley Unifi ed APCD 0 0Sutter Sacramento Valley Feather River AQMD 0 0Tehama Sacramento Valley Tehama County APCD 0 1Trinity North Coast North Coast Unifi ed AQMD 0 2Tulare San Joaquin Valley San Joaquin Valley Unifi ed APCD 0 2Tuolumne Mountain Counties Tuolumne County APCD 0 1Ventura South Central Coast Ventura County APCD 4 1Yolo Sacramento Valley Yolo/Solano AQMD 0 0Yuba Sacramento Valley Feather River AQMD 0 0

Natural Source Emissions - Geogenic Sources

(tons/day, annual average) (Cont)Table D-3 (Cont) * Geogenic emissions are not year-specific.
ARB Almanac 2013 – Appendix D: Natural Sources 

Appendix D

A wildfire is a natural event that burns a variety of vegetation types 

ranging in timing, scale and severity. This wildfire category does not include prescribed fires such as agriculture burning, forest management fires, or Wildland Fire Use (WFU). A prescribed burn is a fire ignited by a planned management action whereas a WFU is a naturally ignited lightning fire that is managed for resources benefit.Wildfires can vary significantly from year to year; an area may have extreme wildfire behavior one year and none the following year. Emissions for PM10, PM2.5, NOx, SOx, NH3, and VOC (Total NonMethane Hydrocarbon, reported here as VOC) are estimated by air 

basin and county. About 90 percent of wildfires occur between May and October, with July as the highest month. The wildfire emission estimates presented in this Almanac are based on a 10-year average that was calculated from actual 2001 - 2010 wildfire activity. Figure D-2 is a map showing all of the wildfires that burned between 2001 and 2010 in California. The tables that follow show the 10-year average emissions per county and air basin.

Wildfires

Figure D-2 
ARB Almanac 2013 – Appendix D: Natural Sources 

Appendix D

Natural Source Emissions - Wildfires

(tons/day, annual average)

Table D-4 

COUNTY AIR BASIN DISTRICT VOC NOx SOx Alameda San Francisco Bay Area Bay Area AQMD 0 0 0 Alpine Great Basin Valleys Great Basin Unifi ed APCD 0 0 0 Amador Mountain Counties Amador County APCD 2 0 0 Butte Sacramento Valley Butte County AQMD 9 0 1 Calaveras Mountain Counties Calaveras County APCD 1 0 0 Colusa Sacramento Valley Colusa County APCD 1 0 0 Contra Costa San Francisco Bay Area Bay Area AQMD 0 0 0 Del Norte North Coast North Coast Unifi ed AQMD 11 0 1 El Dorado Lake Tahoe El Dorado County APCD 1 0 0 El Dorado Mountain Counties El Dorado County APCD 1 0 0 Fresno San Joaquin Valley San Joaquin Valley Unifi ed APCD 1 0 0 Glenn Sacramento Valley Glenn County APCD 3 0 0 Humboldt North Coast North Coast Unifi ed AQMD 5 0 0 Imperial Salton Sea Imperial County APCD 0 0 0 Inyo Great Basin Valleys Great Basin Unifi ed APCD 1 0 0 Kern Mojave Desert Kern County APCD 8 0 0 Kern San Joaquin Valley San Joaquin Valley Unifi ed APCD 1 0 0 Kings San Joaquin Valley San Joaquin Valley Unifi ed APCD 0 0 0 Lake Lake County Lake County AQMD 2 0 0 Lassen Northeast Plateau Lassen County APCD 6 0 0 Los Angeles Mojave Desert Antelope Valley AQMD 1 0 0 Los Angeles South Coast South Coast AQMD 12 2 1 Madera San Joaquin Valley San Joaquin Valley Unifi ed APCD 1 0 0 Marin San Francisco Bay Area Bay Area AQMD 0 0 0 Mariposa Mountain Counties Mariposa County APCD 5 0 0 Mendocino North Coast Mendocino County AQMD 18 0 1 Merced San Joaquin Valley San Joaquin Valley Unifi ed APCD 0 0 0 Modoc Northeast Plateau Modoc County APCD 3 0 0 Mono Great Basin Valleys Great Basin Unifi ed APCD 2 0 0 Monterey North Central Coast Monterey Bay Unifi ed APCD 24 1 1 
ARB Almanac 2013 – Appendix D: Natural Sources 

Appendix D

Natural Source Emissions - Wildfires

(tons/day, annual average) (Cont)Table D-4 (Cont)

COUNTY AIR BASIN DISTRICT VOC NOx SOx Napa San Francisco Bay Area Bay Area AQMD 1 0 0 Nevada Mountain Counties Northern Sierra AQMD 1 0 0 Orange South Coast South Coast AQMD 1 0 0 Placer Lake Tahoe Placer County APCD 0 0 0 Placer Mountain Counties Placer County APCD 7 0 0 Placer Sacramento Valley Placer County APCD 0 0 0 Plumas Mountain Counties Northern Sierra AQMD 22 1 1 Riverside Mojave Desert Mojave Desert AQMD 0 0 0 Riverside Mojave Desert South Coast AQMD 0 0 0 Riverside Salton Sea South Coast AQMD 0 0 0 Riverside South Coast South Coast AQMD 2 1 0 Sacramento Sacramento Valley Sacramento Metropolitan AQMD 0 0 0 San Benito North Central Coast Monterey Bay Unifi ed APCD 0 0 0 San Bernardino Mojave Desert Mojave Desert AQMD 2 0 0 San Bernardino South Coast South Coast AQMD 7 1 1 San Diego San Diego San Diego County APCD 17 5 2 San Francisco San Francisco Bay Area Bay Area AQMD 0 0 0 San Joaquin San Joaquin Valley San Joaquin Valley Unifi ed APCD 0 0 0 San Luis Obispo South Central Coast San Luis Obispo County APCD 0 0 0 San Mateo San Francisco Bay Area Bay Area AQMD 0 0 0 Santa Barbara South Central Coast Santa Barbara County APCD 11 2 1 Santa Clara San Francisco Bay Area Bay Area AQMD 2 0 0 Santa Cruz North Central Coast Monterey Bay Unifi ed APCD 2 0 0 Shasta Sacramento Valley Shasta County AQMD 13 1 1 Sierra Mountain Counties Northern Sierra AQMD 1 0 0 Siskiyou Northeast Plateau Siskiyou County APCD 37 2 2 Solano Sacramento Valley Yolo/Solano AQMD 0 0 0 Solano San Francisco Bay Area Bay Area AQMD 0 0 0 Sonoma North Coast Northern Sonoma County APCD 1 0 0 Sonoma San Francisco Bay Area Bay Area AQMD 0 0 0 
ARB Almanac 2013 – Appendix D: Natural Sources 

Appendix D

COUNTY AIR BASIN DISTRICT VOC NOx SOx Stanislaus San Joaquin Valley San Joaquin Valley Unifi ed APCD 2 0 0 Sutter Sacramento Valley Feather River AQMD 0 0 0 Tehama Sacramento Valley Tehama County APCD 10 0 1 Trinity North Coast North Coast Unifi ed AQMD 34 2 2 Tulare San Joaquin Valley San Joaquin Valley Unifi ed APCD 27 1 2 Tuolumne Mountain Counties Tuolumne County APCD 5 0 0 Ventura South Central Coast Ventura County APCD 11 2 1 Yolo Sacramento Valley Yolo/Solano AQMD 0 0 0 Yuba Sacramento Valley Feather River AQMD 0 0 0 

Natural Source Emissions - Wildfires

(tons/day, annual average) (Cont)

Table D-4 (Cont)