Which of the following describes how nitrogen from fertilizers may harm the environment?

Nitrogen from fertilizers can harm the environment in several significant ways, which is why the most comprehensive option is the best choice.

Leaching into groundwater occurs when excess nitrogen, particularly in the form of nitrate, moves downward through the soil beyond the root zone. This can lead to contamination of drinking water sources, posing risks to human health and aquatic ecosystems.

Runoff into surface water happens when rain or irrigation causes water to flow over the land, carrying nitrogen from fertilized fields into nearby rivers, lakes, or oceans. This excess nitrogen can cause eutrophication, which leads to algal blooms that deplete oxygen in the water and harm aquatic life.

Denitrification is a natural microbial process where anaerobic bacteria convert nitrates into nitrogen gas, releasing gases such as nitrous oxide, a potent greenhouse gas. This process is particularly concerning as it contributes to climate change.

Since nitrogen from fertilizers can cause all these environmental issues, the option that encompasses all aspects—leaching into groundwater, runoff into surface water, and denitrification releasing greenhouse gases—is the most complete response to the question.