Final answer:
True, an increase in nitrates and nitrites does indicate nitrification, which is a part of the nitrogen cycle. The false statement is that nitrification converts nitrites to ammonium ion, as it actually converts ammonia to nitrite and then to nitrate.
Step-by-step explanation:
The statement that an increase in secondary nitrate (NO3-) and nitrite (NO2-) indicates nitrification is true. Nitrification is a biological process in the nitrogen cycle where ammonia (NH3) is oxidized to nitrate (NO3-), passing through nitrite (NO2-) as an intermediate.
This process occurs in two steps: first, ammonia is oxidized to nitrite by certain bacteria, and then another group of bacteria oxidizes nitrite to nitrate.
When comparing the options provided about the nitrogen cycle, statement d is false: Nitrification is the process by which nitrites (NO2-) are converted to ammonium ion (NH4+). In fact, nitrification actually converts ammonia to nitrites and then to nitrates, not the other way around.