These are converted into strong acids which attack new and old buildings, bridges, monuments, rock carvings, etc. Worst affected are objects and structures of easily weathered materials, such as limestone and sandstone. The deposition of nitrogen, from emissions of nitrogen oxides and ammonia, leads to a surplus of nutrients in environments that are normally poor, such as heaths and moorland, which causes a decline in biodiversity. Excess nitrogen is also a problem at sea, where it causes algal blooms, and oxygen depletion. Ground-level ozone is formed in the atmosphere by nitrogen oxides and volatile organic compounds in the presence of sunlight.
Ozone is a poisonous gas that causes damage to agricultural crops, trees and people.
The concentration regularly reaches harmful levels all over Europe. Climate change . Almost all sulphur and a large proportion of the nitrogen oxides that are released into the atmosphere come from the burning of coal and oil. These fossil fuels are also the source of most emissions of carbon dioxide, which contributes to climate change. Most comes from burning coal and oil, during which the sulphur in the fuel is converted into sulphur dioxide.