What impact does agricultural runoff typically have on water quality?

Agricultural runoff has a significant and often detrimental impact on water quality, primarily because it carries various substances from farming practices into nearby bodies of water. When rainfall or irrigation occurs, water can wash away fertilizers, pesticides, herbicides, and sediments from agricultural lands and transport them into streams, rivers, and lakes.

This introduction of chemicals can lead to nutrient pollution, characterized by an excess of nitrogen and phosphorus in the water. These nutrients contribute to problems such as algal blooms, which can deplete oxygen in the water and create "dead zones" where aquatic life cannot survive. Additionally, pesticides and other chemicals can be harmful to both aquatic ecosystems and human health, leading to toxicological concerns.

Therefore, the assertion that agricultural runoff can introduce fertilizers, pesticides, and sediments, leading to pollution, accurately reflects the reality of its impact on water quality. Other choices do not consider the negative aspects of agricultural runoff, such as the introduction and accumulation of pollutants rather than filtration or cleaning effects.