Safety Exam 3 Material Flashcards

Stability Class

• Pasquill-Gifford stability class indicates atmospheric stability, ranging from A (most unstable) to F (most stable), with D being neutral.
• Influenced by wind speed and sunlight exposure.

Convective Boundary Layer

• Characterized by unstable to neutral conditions (A, B, C, D).

Stable Boundary Layer

• Exhibits natural to stable conditions (D, E, F, G).

Atmospheric Conditions

• Unstable: Increased turbulence from solar heating of the ground, causing warmer air near the surface and promoting upward movement.
• Neutral: Wind speed increases while surface heating has less influence; minimal turbulence.
• Stable: Occurs at night or when the ground temperature is lower, resulting in higher-density air near the surface that suppresses turbulence.

Timing of Stable Conditions

• Stable atmospheric conditions are common at night or when surface temperatures are lower than those aloft.

Surface Roughness

• Refers to irregularities on the land surface that create turbulence.
• Includes buildings, trees, and other obstacles.
• Average roughness height (H) is used, typically estimated as H/z = 6/20.

Plume Meander

• Caused by variations in wind direction, leading to plumes changing direction.
• A location may be intermittently inside or outside a plume, with horizontal influence being greater than vertical.

Concentration of Passive Contaminants

• Directly proportional to mass release rate (E); higher release rates increase contamination levels downwind.
• Formula: Cmax = E / (π * u * σy * σz).

Wind Speed Effects

• Inversely proportional relationship; higher wind speeds distribute contaminants faster, reducing localized concentrations.

Atmospheric Stability and Concentration

• Increased atmospheric stability leads to an increase in contaminant concentrations.

Dispersion Coefficients and Stability

• The coefficients (σy and σz) vary based on atmospheric conditions and downwind distance, decreasing with greater stability.

Impact of Meander on Plume Concentration

• Meander results in decreased concentration of a plume at a specified downwind distance.

Impact of Meander on Puff Concentration

• Meander has no effect on the concentration of an instantaneous puff release.

Plume vs. Puff Release

• Plume Release: Continuous discharge over time.
• Puff Release: Instantaneous emission resulting in a shorter duration of gas release.

Continuous vs. Instantaneous Release

• Continuous release spans a prolonged period, while instantaneous release occurs almost instantaneously.