Question 4 of 5: Air Toxics, Mobile Sources, and Emissions-Reporting Programs

Problem 4: Air Toxics, Mobile Sources, and Emissions-Reporting Programs (25 marks)

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.

Part (i) — three air toxics. Polycyclic aromatic hydrocarbons (PAHs): generated by incomplete combustion of organic material (coal, wood, diesel); a representative industry is aluminum smelting (Söderberg/pre-bake anode production) and coke-oven operations for the steel industry, where volatilisation of coal-tar pitch is a major PAH source. Control: thermal oxidation/afterburners at sufficient temperature and residence time to destroy PAH vapours, combined with fabric filtration or ESP capture of particle-bound PAH, sometimes with activated-carbon injection to adsorb the condensed fraction. Volatile organic compounds (VOCs): generated by evaporation of solvents and fuels and by incomplete combustion; a representative industry is petroleum refining (storage-tank and loading-rack losses) and printing/surface-coating operations (solvent-based inks and paints). Control: vapour-recovery units (activated-carbon adsorption or refrigerated condensation) on tank vents and loading racks, thermal or catalytic oxidisers on process vent streams, and substitution with low-VOC or water-based coatings. Gaseous ammonia: generated by fertiliser manufacturing, livestock and agricultural operations, and as an unwanted "slip" product from selective catalytic reduction (SCR) NOₓ control systems that over-dose reagent. Control: wet acid scrubbing (sulphuric or phosphoric acid solution absorbs NH₃), tighter SCR reagent-dosing control to minimise ammonia slip, and covered manure storage with biofilters for agricultural sources.

Part (ii) — mobile source definition and example. A mobile source is any emission source that is not fixed in one location — its emissions come from an engine that moves under its own power, whether on-road (highway vehicles) or non-road (rail, marine, aircraft, construction and agricultural equipment). A representative example is an on-road heavy-duty diesel truck: a compression-ignition engine burns diesel fuel at high in-cylinder temperature and pressure and discharges exhaust through a tailpipe while the vehicle travels the highway network, with emission rates varying strongly with duty cycle (idle, acceleration, steady highway cruise). Two associated pollutants: NOₓ, from thermal formation at the diesel engine's characteristically high combustion temperature, and diesel particulate matter (black carbon), from incomplete combustion of the heavier diesel fuel producing elemental-carbon soot.

Part (iii) — two emissions-reporting programs. National Pollutant Release Inventory (NPRI): a federal program administered by Environment and Climate Change Canada under the authority of the Canadian Environmental Protection Act, 1999 (CEPA); facilities that exceed threshold criteria for employee-hours and production/processing activity must annually report releases, transfers, and disposals of some 300-plus listed substances to air, water, and land into a publicly accessible national database supporting trend analysis, pollution tracking, and public right-to-know. Jurisdiction: federal. Ontario Regulation 127/01 (O. Reg. 127/01, Airborne Contaminant Discharge Monitoring and Reporting): a provincial regulation made under Ontario's Environmental Protection Act, requiring specified facilities to monitor stack emissions of listed contaminants and report the discharge data to the province, feeding Ontario's point-of-impingement standards/Airborne Contaminant Discharge reporting framework. Jurisdiction: provincial (Ontario). Similarities: both are mandatory, facility-level, threshold-triggered reporting programs targeting a defined substance list, and both feed a government database supporting regulatory oversight and public transparency. Differences: NPRI is federal in scope and covers releases to air, water, and land with no direct emission limit attached (it is a pure inventory/reporting tool), whereas O. Reg. 127/01 is Ontario-only, airborne-contaminant-specific, and its reported data feeds directly into point-of-impingement standards that can trigger compliance obligations — so the Ontario program is more directly linked to enforceable technical standards than the purely disclosure-oriented NPRI.