The Gothenburg Protocol is an international treaty established under the United Nations Economic Commission for Europe (UNECE) to address air pollutants. It aims to reduce the emissions of various air pollutants that have significant impacts on human health and the environment. The Protocol sets emission reduction targets for its member countries and promotes the use of best available techniques and practices to achieve these targets.

The air pollutants covered under the Gothenburg Protocol include:

1. Sulphur dioxide (SO2): Sulphur dioxide is a gas released from burning fossil fuels, particularly coal and oil. It is a major contributor to acid rain, which can have detrimental effects on ecosystems and human health. The Protocol sets emission reduction targets for sulphur dioxide to mitigate its environmental impacts.

2. Nitrogen oxide (NOx): Nitrogen oxides are gases produced from the combustion of fossil fuels, especially in vehicles and power plants. They contribute to the formation of smog and acid rain, as well as being a precursor to the formation of ground-level ozone, which is harmful to human health. The Protocol sets emission reduction targets for nitrogen oxides to reduce their impacts on air quality.

3. Particulate matter (PM): Particulate matter refers to tiny particles suspended in the air, including dust, soot, and other pollutants. These particles can be released from industrial processes, vehicle emissions, and natural sources. They can have adverse effects on human health, particularly when inhaled. The Protocol aims to reduce emissions of particulate matter to improve air quality.

4. Black carbon: Black carbon, also known as soot, is a component of particulate matter that is generated from incomplete combustion of fossil fuels, biomass, and other organic matter. It is a potent climate forcer and contributes to global warming and climate change. The Protocol addresses black carbon emissions as part of its efforts to mitigate climate change.

5. Volatile organic compounds (VOCs): Volatile organic compounds are a group of chemicals that easily evaporate at room temperature. They are emitted from various sources, including industrial processes, solvents, and vehicle emissions. VOCs can contribute to the formation of ground-level ozone and have adverse effects on human health. The Protocol includes measures to reduce VOC emissions.

In conclusion, the Gothenburg Protocol covers a range of air pollutants, including sulphur dioxide, nitrogen oxides, particulate matter, black carbon, and volatile organic compounds. By setting emission reduction targets and promoting best practices, the Protocol aims to improve air quality, protect human health, and mitigate the environmental impacts of these pollutants.