What is recognized as the dominant source of excess Nitrogen in surface waters?

Fertilizer runoff is recognized as the dominant source of excess nitrogen in surface waters due to the extensive use of nitrogen-rich fertilizers in agricultural practices. When it rains, these fertilizers can be washed off fields and into nearby streams, rivers, and lakes. This runoff increases the nitrogen levels in these bodies of water, leading to problems such as eutrophication—a process where excessive nutrients cause algal blooms that deplete oxygen in the water and harm aquatic life.

The widespread application of fertilizers in modern agriculture contributes to significant nitrogen loads entering surface waters, especially in regions with intensive farming. This increased nitrogen not only disrupts ecosystems but also poses risks to drinking water quality and environmental health.