Clays in the environment

Abstract

Clays in surface environments are critical to the passage of dissolved species in aqueous solution as they move from one medium to another: air—earth, rainwater—groundwater, sewage—river or ocean, etc. Clays are at the interface of the major surface environments. They are at the surface of the solid earth in its contact with the atmosphere. Any transfer of material between airborne and sediment or rock aqueous systems passes through soils, and hence clays are the critical materials present. The resting place of particulate matter in bodies of water, lakes or oceans, is on clay-dominated sediments. The release or retention of chemical entities in the sediments is governed by clays. Clays are the major inorganic particulate materials in river and groundwaters which will accept or reject ionic or molecular species in aqueous suspensions. The fixation or passage of chemical products will largely be governed by the properties of the clays present. Clays are the substrate of plants and hence will govern the availability of chemical products to plants as they take up nutrients from aqueous solution. They are at the interface between the plant and the mineral world. Clays are present in most aqueous pathways in rocks and hence will be important to the transfer of potential pollutants in problems of nuclear waste disposal (see Section 6.2). Clays are intimately related to the biological processes which are vital to man.