Evaluation of digital optical method to determine plume opacity during nighttime

Area of Science:

• Environmental Science
• Air Quality Monitoring
• Optical Engineering

Background:

• The United States Environmental Protection Agency (USEPA) established opacity standards for industrial emissions to safeguard air quality.
• USEPA Method 9 is the standard for quantifying plume opacity using human observers during daytime.
• Current methods lack nighttime capabilities and comprehensive graphical documentation.

Purpose of the Study:

• To describe the principles and methodology of the Digital Optical Method (DOM) for quantifying plume opacity during nighttime conditions.
• To evaluate the effectiveness of DOM using digital still cameras (DSCs) for nighttime emission monitoring.
• To provide a reliable method for nighttime visual emission evaluation.

Main Methods:

• Development and application of the Digital Optical Method (DOM) using digital still cameras (DSCs).
• Conducting a nighttime field campaign in Springfield, IL.
• Comparing DOM opacity readings with an in-stack transmissometer reference method.

Main Results:

• DOM demonstrated potential for quantifying plume opacity during nighttime.
• Average opacity errors for the DOM contrast model ranged from 2.3-3.5%.
• Average opacity errors for the DOM transmission model ranged from 2.0-7.6% for plumes with 0-50% opacity.

Conclusions:

• The Digital Optical Method (DOM) shows significant promise for accurate nighttime plume opacity quantification.
• DOM, utilizing digital still cameras, offers a viable alternative to traditional methods for nighttime emission monitoring.
• Further validation may lead to DOM's adoption for regulatory compliance in nighttime visual emission evaluations.