Which process is least likely to impact residence time of pollutants?

The impact of pollutants' residence time in the atmosphere refers to the duration that these pollutants remain suspended in the air before they are removed through various processes. Among the listed options, increased vehicle emissions primarily contribute to the overall concentration of pollutants but do not have a direct influence on how long those pollutants stay in the atmosphere.

Rainfall events are significant as they can lead to the removal of pollutants through processes such as washout and scavenging, effectively decreasing their residence time. High wind speeds can also transport and disperse pollutants, potentially reducing their concentration in a given area and impacting how long they remain there. Temperature changes can affect the chemical reactions and physical properties of pollutants, including their volatility, which could also lead to alterations in residence time.

In contrast, while increased vehicle emissions may lead to higher levels of pollutants, they do not inherently change how quickly those pollutants are removed from the atmosphere. Therefore, this option is least likely to impact the residence time of pollutants when compared to the other processes listed.