What is a major contributing factor to environmental acidification in lakes?

Environmental acidification in lakes is primarily influenced by the presence of certain pollutants, notably nitrogen oxides and sulfur oxides, which can lead to increased acidity when they fall back to the earth as acid rain. The correct contributing factor, however, is more accurately linked to the cycles of these pollutants rather than heavy metals alone, which usually do not directly cause a decrease in pH levels in the water.

Increased levels of nitrogen oxides, found in option A, play a critical role in forming acid rain when they react with water in the atmosphere to produce nitric acid, leading to a lower pH in water bodies. Additionally, higher precipitation rates mentioned in option D can exacerbate acidification by increasing the volume of water that picks up pollutants, but they do not fundamentally cause acidification by themselves.

The decrease in caustic materials, referred to in option C, implies a reduction of buffering agents such as limestone or alkaline minerals that help neutralize acids in lakes. A significant reduction of these materials can indeed lead to increased acidification, reflecting a major environmental concern.

In summary, while heavy metals have various environmental effects, they are not a leading cause of lake acidification. The dynamics of nitrogen and sulfur compounds and the lack of buffering agents are