Anhydrous ammonia
from the EPA's Mid-Atlantic Integrated Assessment:
Ammonia "is stored as a liquid, but when it hits the water it turns into a gas and dissolves. It reacts very quickly, rapidly raising pH. Special training and experience is needed to handle the hazardous ammonia, and additional analyses must be performed downstream in order to monitor the biological effects it has on the ecosystem. There are dangerous consequences associated with excessive ammonia application."