Oil, pesticides, pollutants in our oceans and atmosphere...humans have a major impact on the environment. The aim of this course is to describe the chemical functioning of natural systems and the impact of human activity on these systems. Principles and methods applicable to the understanding and resolution of environmental problems are developed. Concepts concerning elementary cycles (S, C, etc.) and natural biological and physical processes are integrated into the study of polluted environments such as the atmosphere, the ocean and soils. Various anthropogenic pollutants are addressed, such as petroleum and synthetic organic compounds. The analysis of sedimentary records is also addressed, enabling us to understand the temporal dynamics of pollutants during the industrial era.