ABSTRACT
The carbon cycle in groundwaters begins with weathering reactions in the recharge area driven by C02 dissolved from the soil. Carbonate reactions dominate the geochemical evolution in shallow groundwaters, and so bicarbonate is generally the dominant anion in fresh water resources. The carbonate system evolves with subsequent organic and inorganic reactions in soils and aquifers. Microbiological activity plays a key role in the degradation of organic compounds and evolution of redox conditions. The chemistry and isotopes of carbon species provide insights into carbonate evolution and carbon cycling in groundwaters: insights required for an understanding of groundwater quality, fate of contaminants and for a correct interpretation of groundwater age. This review of the all-important carbon system provides a basis for the topics of groundwater quality, groundwater dating, and water-rock interaction, which are discussed in subsequent chapters.
