The majority of atmospheric mercury is produced by

Atmospheric mercury is produced by burning of coals where it accumulates on crops resulting in ingestion.

Since it is poisonous, when ingested it causes health problems that affect the reproductive system, immune system, nervous system, etc.  

Other mercury contributing sources are gold mine operations, burning processes in the incinerators, and industrial boilers. In the US, coal combustion is the highest source of the atmospheric mercury accounting 50%. Asia also emits mercury at a high rate due to a lot of coal-powered incinerators.

answer; the correct answer to the above statement is (biosphere); ///