Particulate carbon in Los Angeles air

Area of Science:

• Environmental Science
• Atmospheric Chemistry
• Analytical Chemistry

Background:

• Particulate carbon is a major component of air pollution.
• Understanding the sources of particulate carbon is crucial for air quality management.
• Los Angeles experiences significant air pollution challenges, particularly smog.

Purpose of the Study:

• To determine the concentrations of total, organic, and elemental particulate carbon in Los Angeles air.
• To analyze the temporal variations of these carbon components during smog episodes.
• To investigate the sources and formation pathways of particulate organic carbon.

Main Methods:

• A selective combustion method was employed for the analysis of particulate carbon.
• Measurements were conducted during multiday smog episodes in Los Angeles.
• Organic carbon to elemental carbon ratios were calculated.

Main Results:

• Carbon concentrations ranged from 10-56 micrograms per cubic meter.
• Organic carbon to elemental carbon ratios varied seasonally, from approximately 3 in winter to 10 during the smog season.
• Photochemical production of particulate organic carbon was estimated at 76-118 x 10(3) kg/day, significantly higher than direct emissions (31 x 10(3) kg/day).

Conclusions:

• Photochemical processes are a dominant source of particulate organic carbon in Los Angeles air.
• Gas-to-particle conversion of precursor hydrocarbons likely contributes significantly to organic carbon formation.
• The findings highlight the importance of controlling photochemical smog to reduce particulate carbon pollution.