Safety Exam 3 Material Flashcards

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Questions and Answers

What does stability class indicate and why is it important?

Pasquill-Gifford stability class ranges from A (most unstable) to F (most stable); D is neutral. It depends on wind speed and quantity of sunlight.

What is the Convective Boundary Layer?

Unstable to neutral (ABCD).

What is the Stable Boundary Layer?

Natural to stable (DEFG).

What is the difference between unstable, neutral, and stable atmospheric conditions?

Unstable enhances atmospheric turbulence; neutral indicates no influence from temperature differences; stable suppresses turbulence. Signup and view all the answers

What time of day can stable atmospheric conditions typically occur?

In nighttime conditions or during the day when ground temperature is lower than temperature at higher elevations. Signup and view all the answers

What is surface roughness and how is it related to mean obstacle height?

Surface roughness refers to irregularities on the surface that generate turbulence, influenced by surrounding terrain. Signup and view all the answers

What causes plume meander?

Atmospheric variations in wind direction cause plumes to change direction or meander. Signup and view all the answers

How is the concentration of a passive contaminant at a given location related to the mass release rate?

Concentration at a given location is directly proportional to the release rate, E. Cmax = E/(piusigmay*sigmaz). Signup and view all the answers

How is the concentration of a passive contaminant related to wind speed?

Concentration at a given location is inversely proportional to wind speed, u. Cmax = E/(piusigmay*sigmaz). Signup and view all the answers

How is the concentration of a passive contaminant at a given location related to atmospheric stability?

Concentration increases with increased atmospheric stability. Signup and view all the answers

How are passive atmospheric dispersion coefficients related to atmospheric stability?

Dispersion coefficients decrease with increased stability. Signup and view all the answers

What is the effect of meander on the concentration of a plume at a given downwind distance?

Meander decreases the concentration of a plume at a given downwind distance. Signup and view all the answers

What is the effect of meander on the concentration of a puff at a given downwind distance?

Meander has no effect on a puff. Signup and view all the answers

What is the difference between a plume and a puff release?

Plume release is continuous, while a puff is instantaneous. Signup and view all the answers

What is the difference between continuous and instantaneous release?

Continuous release happens over a long period, while instantaneous release is a very short release of gas. Signup and view all the answers

Study Notes

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.

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Description

Prepare for your Safety Exam 3 with these flashcards covering key concepts such as stability classes and boundary layers. Each card highlights important definitions and their significance in understanding environmental stability. Perfect for quick reviews and exam preparation.