Pennsylvania Northern Region Emissions Practice Exam 2026 - Free Emissions Practice Questions and Study Guide

Nitrogen oxides are primarily responsible for acid rain due to their role in the formation of nitric acid in the atmosphere. When nitrogen oxides, which are emitted from vehicle exhaust, industrial processes, and power plants, react with water vapor and other atmospheric elements, they undergo a series of chemical reactions that ultimately lead to the production of nitric acid (HNO3). This acid can then mix with rainwater, resulting in acid rain that has a lower pH and can negatively impact ecosystems, buildings, and human health.

In contrast, hydrocarbons are typically associated with the formation of ground-level ozone and smog, rather than acid rain; carbon dioxide is a greenhouse gas that contributes to climate change and ocean acidification but does not directly lead to acid rain; and ozone, while a crucial component of the atmosphere, particularly in the stratosphere, is not a direct contributor to acid rain formation. These distinctions underscore the specific role nitrogen oxides play in the creation of acid rain and its environmental effects.