1) A volume including the lower part of the troposphere (as high as living organisms can fly or be lofted) and the surface of the earth including the oceans. This region, by definition, encompasses all the living matter of the earth. Some very important atmospheric chemicals are produced in this region and pass into the atmosphere. This region exchanges chemicals and particulate matter with the atmosphere and soils and waters of the earth.
source: [Journal of Geophysical Research;v99; 16511-16521;1994]