Which factor contributes to excess nitrates in water bodies?

Fertilizer runoff is a significant contributor to excess nitrates in water bodies. When fertilizers are applied to agricultural fields, they often contain high levels of nitrates, a vital nutrient for plant growth. However, during rainfall or irrigation, these nitrates can leach into the soil and subsequently wash into nearby water bodies. This process increases the nitrate concentration in streams, rivers, and lakes, leading to nutrient pollution.

Elevated nitrate levels can result in harmful algal blooms, which deplete oxygen in the water and negatively impact aquatic ecosystems. The runoff occurs notably after heavy rains when the water carries excess nutrients from the fields into the water systems.

Other factors such as industrial waste or agricultural irrigation can also affect water quality, but fertilizer runoff stands out as a primary source of excess nitrates due to the direct application of these substances in agricultural practices and the potential for them to wash into waterways relatively easily.