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Lecture 9 - Engineering Science: Air Pollution from Vehicles

约 504 个字 预计阅读时间 2 分钟

  • Speaker: Prof. Felix Leach

What is Air Pollution

  • Sources
    • Mobile Sources
    • Natural Sources
    • Stationary Sources
  • Pollutants
    • Primary Pollutants
    • Secondary Pollutants

Perception and Reality

  • The UK air quality crisis has shown gradual improvement due to stringent regulatory measures.
  • In China, air quality has seen slow but steady improvement since 2014, following the implementation of comprehensive environmental policies.

Health Effects

  • Headache and anxiety (\(\ce{SO2}\))
  • Impacts on the central nervous system (PM)
  • Irritations of eyes, nose and throat
  • Breathing problems (\(\ce{O3}\), PM, \(\ce{NO2, BaP}\))
  • Irritation, inflammation and infections
  • Asthma and reduces lung function (\(\ce{NO2}\))
  • Chronic obstructive pulmonary disease (PM)
  • Lung cancer (PM, \(\ce{BaP}\))
  • Cardiovascular diseases (PM, \(\ce{O3}, \ce{SO2}\))
  • Impacts on liver, spleen and blood (\(\ce{NO2}\))
  • Impacts on the reproductive system (PM)

Current Situation

  • Immediate action is required to address deteriorating urban air quality.
  • Fleet renewal is a critical component of improving air quality.
  • Economic considerations play a significant role in implementing effective solutions.
  • The widespread adoption of electric vehicles (EVs) is unlikely to yield significant improvements in the short term.

Where do Emissions Come From

  • Ideal combustion: \(\ce{C_{x}H_{y}} + \ce{O2} \rightarrow \ce{CO2} + \ce{H2O}\)
  • Combustion in air: \(\ce{C_{x}H_{y}} + (\ce{O2} + \frac{79}{21} \ce{N2}) \rightarrow \ce{CO2} + \ce{H2O} + \ce{N2}\)
  • Real combustion involves high temperatures and rapid reactions, leading to the formation of by-products: \(\ce{C_{x}H_{y}} + (\ce{O2} + \frac{79}{21} \ce{N2}) \rightarrow \ce{CO2} + \ce{H2O} + \ce{N2} + \ce{CO} + \ce{NO_{x}} + \ce{C} + \ce{C_{x}H_{y}}\)

The by-products of combustion, including \(\ce{CO}, \ce{NO_{x}}, \ce{C}, \ce{C_{x}H_{y}}\), constitute the primary pollutants.

Cleaning Up These Emissions

Modern vehicles employ advanced aftertreatment systems, historically referred to as catalytic converters, to mitigate emissions.

Contemporary internal combustion engines are equipped with highly efficient aftertreatment systems.

As a result, many modern vehicles achieve near-zero emissions of regulated pollutants.

Particulates: A Forgotten Problem

Particulate matter (PM) is inhaled through the respiratory tract, entering the body via the nose and mouth.

While the respiratory system filters out larger particles, smaller particles such as PM2.5 penetrate deeper into the lungs.

PM2.5 particles can reach the alveoli, leading to severe health implications for both the respiratory and cardiovascular systems.

The highest concentrations of PM are often attributed to sources such as fast-food outlets and smoking, rather than unregulated diesel trains.

Conclusion

  • Time is a critical factor: While electric vehicles (EVs) alone are insufficient, a technology-neutral approach may yield better results.
  • The primary challenge is not rooted in engineering science but rather in economic constraints.
  • Internal combustion engines (ICEs) can contribute to the solution, but their limitations must be carefully considered.
  • Current trends indicate a lack of significant progress in addressing air pollution.
  • Individual and collective decision-making play a crucial role in mitigating air pollution.
  • Substantial further research is required to develop effective solutions.
  • Several cost-effective and straightforward measures are available to achieve rapid improvements.