11-CS-3 Engineering Management · May 2016
Nivaar worked solution (AI-drafted; not reviewed by a licensed engineer)
National Exams — May 2016 — 11-CS-3 Sustainability, Engineering and the Environment. Closed book; approved calculator permitted. Any four questions constitute a complete paper; all questions are of equal value (25 marks each).
Question text not reproduced: the examination questions are © Engineers and Geoscientists BC. Open the official past paper (linked at the top of this page) to read the question, then follow the worked solution below.
The road-vehicle pollutants that create photochemical smog are nitrogen oxides (NOₓ) and volatile organic compounds (VOCs) (unburned hydrocarbons), with carbon monoxide also present. In sunlight, NO₂ photolyzes and drives ozone formation:
Normally NO would destroy the ozone ($\text{NO} + \text{O}_3 \rightarrow \text{NO}_2 + \text{O}_2$), but VOCs intercept and consume the NO (forming more NO₂ without consuming ozone), allowing ozone to accumulate. The main toxic chemical is ground-level ozone (O₃). In humans it irritates the eyes and respiratory tract, reduces lung function, and aggravates asthma and other respiratory disease; in plants it damages leaf tissue, impairs photosynthesis, and reduces crop yields and growth.
The Montreal Protocol controls ozone-depleting substances—CFCs, halons, HCFCs, carbon tetrachloride, and methyl bromide. These affect the environment's protective (regulating) service function of shielding the surface from harmful solar ultraviolet radiation: by destroying stratospheric ozone, they degrade the ozone layer that protects life from UV.
The Sun emits high-energy short-wave radiation, including ultraviolet (UV) and visible light, which passes largely unimpeded through the atmosphere and warms the Earth's surface. The warmed surface re-radiates energy at longer wavelengths as infrared (IR) radiation. Greenhouse gases are transparent to the incoming UV/visible but strongly absorb the outgoing IR and re-emit it in all directions, including back to the surface, trapping heat in the lower atmosphere. A higher concentration of greenhouse gases absorbs more of the outgoing IR, returning more heat to the surface and reducing the rate at which the planet sheds energy to space, so the surface must warm to restore radiative balance—hence a warmer planet.
Convert to CO₂e (mass × GWP; CO₂ = 1, CH₄ = 25, SF₆ = 22,800):
Ranked from greatest to least: SF₆ (1.37×10¹⁵) > CH₄ (1.25×10¹⁵) > CO₂ (1.20×10¹⁵). Here the three are comparable, and SF₆'s extreme potency lets even 60 Gg edge out the others—unlike the global picture, where CO₂'s vast mass dominates.
Mitigation reduces the cause of climate change—cutting emissions or enhancing sinks. Example: wind or solar generation replaces fossil-fuel combustion, so less CO₂ is emitted, attacking the driver of warming. Adaptation adjusts to the effects. Example: building dykes/sea walls, which reduce harm from rising seas and storm surge by physically holding back higher water. Mitigation lessens future warming; adaptation reduces vulnerability to warming already underway.
