Environmental Chemistry deals with the origins, transport, reactions, effects and fates of chemical species in the water, air, terrestrial and living environments. It overlaps with different branches of chemistry such as organic chemistry, analytical chemistry, physical chemistry, photochemistry, geochemistry and biological chemistry and also includes many widely different fields such as physics, life sciences, agricultural sciences, medical sciences, public health and sanitary engineering.
The environment consists of various segments such as atmosphere, hydrosphere, lithosphere and biosphere.
Atmosphere: The following points highlight the vital role played by atmosphere in the survival of life in this planet.
• The atmosphere is the protective blanket of gases which is surrounding the earth. It protects the earth from the hostile environment of outer space.
• It absorbs IR radiations emitted by the sun and reemitted from the earth and thus controls the temperature of the earth.
• It allows transmission of significant amounts of radiation only in the regions of 300 – 2500 nm (near UV, Visible, and near IR) and 0.01 – 40 meters (radio waves). i.e it filters tissue damaging UV radiation below 300 nm.
• It acts as a source for CO2 for plant photosynthesis and O2 for respiration
• It acts as a source for nitrogen for nitrogen fixing bacteria and ammonia producing plants.
• The atmosphere transports water from ocean to land.
Hydrosphere: The hydrosphere is a collective term given to all different forms of water. It includes all types of water resources such as oceans, seas, rivers, lakes, streams, reservoirs, glaciers and ground waters. The distribution of earth's water supply is shown in As can be seen, only 1% of the total water supply is available as fresh water in the form of rivers, lakes, streams and ground water for human consumption and other uses.
The major problem with global water supply is it's non-uniform distribution, since people in areas with low precipitation often consume more than people in regions with more rainfall.
• The earth is divided in to layers as shown in fig: 3
• The lithosphere consists of upper mantle and the crust.
- The crust is the earth's outer skin that is accessible to human.
- The crust consists of rocks and soil of which the latter is the important part of lithosphere.
- The biosphere refers to the realm of living organisms and their interactions with the environment (VIZ: atmosphere, hydrosphere and lithosphere)
• The biosphere is very large and complex and is divided into smaller units called ecosystems.
• Plants, animals and microorganisms which live in a definite zone along with physical factors such as soil, water and air constitute an ecosystem.
• Within each ecosystems there are dynamic inter relationships between living forms and their physical environment