Download PrepIQ NWCA Atmospheric Science Air Quality and Pollution Control Ultimate Exam and more Exams Technology in PDF only on Docsity!
Science Air Quality and Pollution
Control Ultimate Exam
Question 1. Which gas makes up approximately 78 % of the dry atmosphere? A) Oxygen B) Nitrogen C) Argon D) Carbon dioxide Answer: B Explanation: Dry air consists of about 78 % nitrogen, 21 % oxygen, ~0.93 % argon, and trace gases including CO₂. Question 2. The layer of the atmosphere where temperature increases with height due to ozone absorption is: A) Troposphere B) Stratosphere C) Mesosphere D) Thermosphere Answer: B Explanation: In the stratosphere, ozone absorbs ultraviolet radiation, causing a temperature inversion (the “stratospheric temperature rise”). Question 3. The dry adiabatic lapse rate is approximately: A) 3 °C km⁻¹ B) 6.5 °C km⁻¹ C) 9.8 °C km⁻¹ D) 12 °C km⁻¹ Answer: C
Science Air Quality and Pollution
Control Ultimate Exam
Explanation: For unsaturated air, the temperature decreases about 9.8 °C per kilometer when rising adiabatically. Question 4. Which of the following is a primary pollutant? A) Ozone B) Sulfuric acid C) Nitrogen dioxide D) Particulate sulfate Answer: C Explanation: NO₂ is emitted directly from combustion sources; ozone forms secondarily from photochemical reactions. Question 5. The main acid component of acid rain is: A) Hydrochloric acid B) Sulfuric acid C) Nitric acid D) Both B and C Answer: D Explanation: Acid rain contains both sulfuric (from SO₂) and nitric acid (from NOₓ) produced by atmospheric oxidation. Question 6. Which hazardous air pollutant is a heavy metal that bioaccumulates in fish? A) Lead (Pb) B) Mercury (Hg) C) Arsenic (As) D) Cadmium (Cd)
Science Air Quality and Pollution
Control Ultimate Exam
C) Stack exit velocity D) Effective stack height Answer: A Explanation: σ_y is the standard deviation of concentration distribution in the cross-wind (horizontal) direction. Question 10. Which factor most directly increases the plume rise of a stack emission? A) Lower ambient temperature B) Higher exit velocity C) Smaller stack diameter D) Increased atmospheric stability Answer: B Explanation: Higher exit velocity imparts greater momentum, causing the plume to rise higher before mixing. Question 11. The most common method for continuous SO₂ monitoring at ambient stations is: A) Chemiluminescence B) UV fluorescence C) Non-dispersive infrared (NDIR) D) Electrochemical cell Answer: B Explanation: UV fluorescence selectively excites SO₂ molecules, providing rapid, accurate ambient measurements.
Science Air Quality and Pollution
Control Ultimate Exam
Question 12. Which sampler is designed to collect PM₂.₅ while minimizing wall losses? A) High-volume filter sampler B) Cascade impactor C) Tapered element oscillating microbalance (TEOM) D) Cyclone separator Answer: C Explanation: TEOM draws air through a filter on a heated element, providing real-time PM₂.₅ mass with reduced artifact losses. Question 13. The analytical technique that separates complex VOC mixtures before detection is: A) Mass spectrometry (MS) alone B) Gas chromatography (GC) C) Chemiluminescence D) NDIR Answer: B Explanation: GC resolves individual VOCs based on volatility and polarity, allowing subsequent detection (e.g., by MS). Question 14. The Air Quality Index (AQI) value of 151–200 corresponds to which health category? A) Good B) Moderate C) Unhealthy for Sensitive Groups D) Unhealthy
Science Air Quality and Pollution
Control Ultimate Exam
C) Gravity settling chamber D) Wet scrubber Answer: C Explanation: Gravity settling chambers rely on particles reaching a terminal velocity where drag balances gravity, allowing them to settle out. Question 18. In an electrostatic precipitator, the “corona discharge” is used to: A) Heat the gas stream B) Generate ions that charge particles C) Create turbulence for mixing D) Vaporize condensable gases Answer: B Explanation: The high-voltage electrode creates a corona that ionizes the gas, providing charge carriers that attach to particles. Question 19. Which of the following best describes Henry’s Law in absorption processes? A) Solubility is proportional to partial pressure of the gas B) Solubility is inversely proportional to temperature C) Solubility depends on particle size distribution D) Solubility is independent of pressure Answer: A Explanation: Henry’s Law states that at constant temperature, the amount of gas dissolved in a liquid is proportional to its partial pressure. Question 20. Activated carbon removes VOCs primarily by:
Science Air Quality and Pollution
Control Ultimate Exam
A) Chemical reaction forming sulfates B) Physical adsorption onto pore surfaces C) Catalytic oxidation to CO₂ D) Electrostatic precipitation Answer: B Explanation: VOC molecules are attracted to the high surface area of activated carbon pores and held by van der Waals forces. Question 21. The most effective method for controlling nitrogen oxides (NOₓ) from a coal-fired boiler is: A) Selective catalytic reduction (SCR) B) Electrostatic precipitation C) Fabric filtration D) Wet scrubbing with lime Answer: A Explanation: SCR injects ammonia (or urea) and uses a catalyst to convert NOₓ to N₂ and H₂O with high efficiency. Question 22. The “venturi scrubber” achieves high collection efficiency for particles by: A) Increasing gas velocity to create a low-pressure zone that atomizes liquid B) Using a packed bed of sorbent material C) Employing an electric field to charge particles D) Rotating baffles to enhance impaction Answer: A
Science Air Quality and Pollution
Control Ultimate Exam
D) Lead Answer: C Explanation: VOCs react with NOₓ in sunlight to produce ozone, the key component of photochemical smog. Question 26. The “planetary boundary layer” height typically: A) Decreases at night due to cooling B) Remains constant throughout the day C) Increases with altitude above sea level D) Is independent of surface heating Answer: A Explanation: Nocturnal cooling stabilizes the surface layer, causing the mixed layer (PBL) to shrink. Question 27. Which of the following is NOT a greenhouse gas? A) Methane (CH₄) B) Nitrous oxide (N₂O) C) Water vapor (H₂O) D) Ozone (O₃) in the troposphere Answer: D Explanation: Tropospheric ozone acts as a pollutant and a short-lived greenhouse gas, but in the context of the major long-lived greenhouse gases, O₃ is not listed among the primary ones (CO₂, CH₄, N₂O, H₂O). Question 28. The term “global warming potential (GWP)” quantifies: A) The radiative efficiency of a gas relative to CO₂ over a 100-year horizon
Science Air Quality and Pollution
Control Ultimate Exam
B) The atmospheric lifetime of a gas only C) The solubility of gases in seawater D) The ozone depletion potential Answer: A Explanation: GWP compares the integrated radiative forcing of a gas to that of CO₂ over a specified time period. Question 29. Under the Clean Air Act, the National Ambient Air Quality Standards (NAAQS) are set for: A) Only criteria pollutants B) All listed hazardous air pollutants C) Both criteria and HAPs D) Indoor air quality Answer: A Explanation: NAAQS are health-based limits for the six criteria pollutants (SO₂, NO₂, CO, O₃, PM₂.₅, PM₁₀). Question 30. The Montreal Protocol primarily addresses: A) CO₂ emissions B) Ozone-depleting substances (CFCs) C) Mercury emissions D) Black carbon Answer: B Explanation: Signed in 1987, the protocol phases out chlorofluorocarbons and related compounds that damage the stratospheric ozone layer.
Science Air Quality and Pollution
Control Ultimate Exam
Explanation: Warm indoor air rises, creating pressure differentials that draw in cooler outdoor air at lower levels. Question 34. Which of the following gases has the highest global warming potential over a 20-year horizon? A) CO₂ B) CH₄ C) N₂O D) HFC- 23 Answer: D Explanation: HFC-23 has a GWP of about 12,000 over 20 years, far exceeding CO₂ (1), CH₄ (~84), and N₂O (~298). Question 35. The term “fugacity” in atmospheric chemistry refers to: A) The tendency of a gas to escape a liquid phase B) The kinetic energy of particles C) The ratio of actual pressure to standard pressure D) The concentration of aerosols Answer: A Explanation: Fugacity is an effective pressure that accounts for non-ideal behavior, describing a gas’s propensity to transfer between phases. Question 36. Which meteorological condition most enhances the formation of ground-level ozone? A) Low solar radiation B. High relative humidity and low temperature C. Strong wind shear
Science Air Quality and Pollution
Control Ultimate Exam
D. High temperature and strong sunlight Answer: D Explanation: Ozone production accelerates with intense UV radiation and warm temperatures, which drive VOC and NOₓ photochemistry. Question 37. A “fugacity diagram” is useful for: A) Estimating pollutant deposition velocities B. Predicting phase partitioning between air and water C. Calculating plume rise D. Determining stack height Answer: B Explanation: Fugacity diagrams illustrate the distribution of a chemical among environmental media at equilibrium. Question 38. The “dry deposition velocity” of a gas is influenced most by: A. Atmospheric pressure only B. Surface roughness and chemical reactivity C. Cloud cover D. Altitude Answer: B Explanation: Rough surfaces and reactive gases increase deposition velocity, while smooth or inert surfaces reduce it. Question 39. What is the primary pollutant emitted from diesel engines that contributes to particulate matter? A. Sulfur dioxide
Science Air Quality and Pollution
Control Ultimate Exam
Question 42. The “effective stack height” (H_e) is the sum of: A. Physical stack height plus plume rise B. Stack diameter plus exit velocity C. Ground elevation plus meteorological visibility D. Stack temperature differential only Answer: A Explanation: H_e = H_s (physical height) + Δh (plume rise due to buoyancy and momentum). Question 43. Which instrument measures ambient CO concentrations using infrared absorption? A. Chemiluminescence detector B. Non-dispersive infrared (NDIR) analyzer C. Electrochemical sensor D. UV fluorescence detector Answer: B Explanation: NDIR analyzers detect CO by measuring attenuation of IR light at characteristic wavelengths. Question 44. The “mixing height” in the daytime is primarily controlled by: A. Surface roughness length B. Solar heating of the ground C. Atmospheric pressure gradients D. The Coriolis force Answer: B
Science Air Quality and Pollution
Control Ultimate Exam
Explanation: Daytime solar heating creates buoyancy, deepening the mixed layer (mixing height). Question 45. Which of the following best describes “biofiltration” for VOC control? A. Thermal oxidation at >800 °C B. Catalytic conversion on a metal surface C. Passage of contaminated air through a biologically active media where microbes degrade organics D. Physical adsorption onto activated carbon Answer: C Explanation: Biofilters use microorganisms immobilized on a support medium to metabolize VOCs into CO₂, water, and biomass. Question 46. In the context of the Clean Air Act, “NAAQS” are reviewed and potentially revised every: A. 5 years B. 10 years C. 15 years D. 20 years Answer: B Explanation: The EPA is required to review the standards at least once every five years, but major revisions typically occur on a ten-year cycle. Question 47. Which of the following gases is the most abundant anthropogenic greenhouse gas? A. Methane (CH₄) B. Nitrous oxide (N₂O)
Science Air Quality and Pollution
Control Ultimate Exam
B. Eulerian model C. Box model D. Gaussian plume model Answer: B Explanation: Eulerian models discretize the atmosphere into grid cells and compute fluxes across them. Question 51. The primary mechanism for removal of SO₂ in a limestone wet scrubber is: A. Physical absorption only B. Chemical neutralization to calcium sulfite/sulfate C. Photolysis D. Adsorption onto activated carbon Answer: B Explanation: SO₂ reacts with CaCO₃ (limestone) forming calcium sulfite or sulfate, which are removed in the liquid. Question 52. Which pollutant is regulated under the “Lead and Copper Rule” for drinking water but also considered a hazardous air pollutant? A. Lead (Pb) B. Arsenic (As) C. Mercury (Hg) D. Cadmium (Cd) Answer: A Explanation: Lead is both a drinking-water contaminant and a HAP under the Clean Air Act.
Science Air Quality and Pollution
Control Ultimate Exam
Question 53. The “mass balance” equation for a control volume at steady state neglects: A. Inflow and outflow terms B. Chemical reactions within the volume C. Accumulation term D. Source term Answer: C Explanation: At steady state, the accumulation (change with time) term is zero. Question 54. Which of the following is a typical emission factor for gasoline-powered passenger cars for CO (g kg⁻¹ fuel)? A. 0. B. 0. C. 2. D. 20. Answer: B Explanation: Typical CO emission factors for gasoline cars are around 0.2 g per kg of fuel burned. Question 55. The “first-order decay” model for atmospheric pollutant concentration assumes: A. Linear increase with time B. Exponential decrease with a constant rate coefficient C. No chemical transformation D. Immediate removal at the source
