Nitrogen is dissolved in rainwater to form dilute nitric acid, natural acid rain that provides some of the nitrogen fertiliser requirements of plants. Bacteria in the nodules of leguminous plants produce ammonia and soluble nitrates. There are no natural anion attractors in the soil, so they cannot be stored there. Instead they are washed through the soil to rivers. Thus, a constant supply of nitrates is required throughout the growing season.
Plant roots obtain nitrogen as nitrates and ammonia from the soil.
All three gases are present in the emissions from vehicles and contribute in various ways to acid rain. The properties of nitrogen dioxide can be investigated by preparing it in a gas jar in the laboratory or as shown on page 32 of the book. Its effects on the environment are discussed on page 34. 1 Nitrogen dioxide is prepared by pouring concentrated nitric acid on to copper turnings. As the gas forms, it is a strong brown colour.