Trace elements, essential or non-essential are distributed and redistributed naturally in the environment by both geologic and biologic cycles. Weathering and disintegration of rocks bring them into the soil, streams and rivers. Ultimately they are carried to the oceans to be deposited as sediments.
Geologic disturbances in earth’s crust finally bring these deposits up as sedimentary rocks. From the soil or water these elements are taken up by plants in the living system and passed on to higher trophic levels. When living beings die, decay and decomposition release them in the environment. Some of these elements may become air-borne in the process from where they are returned to the soil or water underneath as dry fall-outs or along with rains.
The natural cycling of trace elements has, however, been disturbed by human activity in two j ways. Firstly, man has caused a rapid increase in the concentration of trace elements in various I components of the environment and the biosphere. Secondly, he has altered the speciation – the | chemical or biochemical form of many of these elements so as to make them available to the biosphere.
Man’s thirst for minerals from which these elements come is enormous. Extensive use and combustion of fossil fuels bring out a number of toxic trace elements which are added to the environment. Naturally occurring rather innocuous minerals are mined, refined and processed to be used by technologically advanced societies. In the process a lot of the non-biodegradable stuff is converted to harmful state or is simply left over as wastes to be added, ultimately to the environmental load of pollutants.