In recent years, with the rapid development of the automotive economy, the production and usage of motor vehicles have surged, leading to a significant increase in exhaust emissions that pose a growing threat to the environment.
Vehicle emissions have become a global public hazard.
The main pollutants in automobile exhaust emissions are carbon monoxide, hydrocarbons, nitrogen oxides, sulfur dioxide, lead compounds, polycyclic aromatic hydrocarbons, and particulate matter.
1. Carbon Monoxide (CO):
In internal combustion engines, CO is a colorless, odorless gas produced when combustion is incomplete due to insufficient air or other reasons.
Upon inhalation, CO readily binds with hemoglobin in the blood, with an affinity 300 times greater than that of oxygen. Consequently, hemoglobin in the lungs binds with CO instead of oxygen, resulting in oxygen deprivation, leading to symptoms of poisoning such as headaches, dizziness, vomiting, and potentially fatal outcomes.
2. Hydrocarbons (HC):
HC refers to the unburned components in engine exhaust, including fuel evaporation and leakage from the fuel supply system. While HC alone has minimal effects on human health except at relatively high concentrations, it is a significant contributor to the formation of photochemical smog.
3. Nitrogen Oxides (NOx):
NOx is a brownish, pungent-smelling exhaust gas produced in large quantities when the engine operates under certain loads. Initially, the toxicity of NO is relatively low when emitted, but it readily oxidizes to form more toxic nitrogen oxides such as NO2.
Upon entering the alveoli of the lungs, NOx forms nitrous acid and nitric acid, causing severe irritation to lung tissues. NOx reacts with HC under sunlight to form toxic photochemical smog, which, when present in high concentrations, induces eye irritation, tearing, redness, respiratory distress, and other symptoms of poisoning. Photochemical smog also damages plants, reduces atmospheric visibility, and harms rubber products.
4. Particulate Matter (PM):
Particulate matter emitted from the combustion chamber has three main sources: non-combustible substances, combustible substances that remain unburned, and combustion products.
Most of the particulate matter emitted during combustion consists of solid carbon, with additional components including hydrocarbons, sulfides, and metallic ash. Diesel engines emit substantial quantities of black carbon particles when fuel combustion is incomplete. These particles not only harm the respiratory system but also adsorb substances such as sulfur dioxide and carcinogenic polycyclic aromatic hydrocarbons in their pores.
Exhaust pollution has become one of the significant environmental challenges facing the world today, exerting severe impacts on human health and the environment. Addressing the issue of motor vehicle exhaust pollution requires not only governments to establish stricter emission standards and regulatory measures but also concerted efforts from automobile manufacturers and individuals to adopt effective measures.
Only through the collective efforts of society can motor vehicle exhaust pollution be effectively reduced, environmental quality improved, human health safeguarded, and sustainable development achieved.
