CHAPTER 13: Fluorides in Different Types of Aquatic Systems and their Correlation with Metals and Metalloids Check Access

The levels of fluorides and heavy metals in aquatic systems are related to various factors, such as direct and indirect pollution sources, natural geochemical processes and physico-chemical characteristics of water systems (pH, salinity, cation and anion presence, etc.). Fluorides and heavy metals have been found to interrelate and to correlate with other inorganic constituents. Quality problems arise when groundwaters contain low sulfate, calcium or magnesium concentrations. The positive correlation between arsenic and other heavy metals with fluorides and the negative correlation between calcium, magnesium and hardness levels with fluoride content is usual in waters related to volcanism and hydrothermal activity. Fluorides also interact and correlate with various aluminium forms and other inorganic constituents forming complexes of varying solubility. A review of the presence of heavy metals and fluoride ions in various water systems has been carried out, in order to present the monitoring aspects and magnitude of the problem. Major health effects on humans, plants and animals are also presented. The importance of various physico-chemical parameters and water types (hardness, hydrothermal activity, etc.) are examined and presented, with a special focus ono fluoride presence and the effect on the complexation properties and interactions with various metal and metalloids present in the system. Finally, several techniques are described for the removal of fluorides under specified conditions, their major advantages and relation to the interaction of fluorides with other elements.