The source of the mercury is in part natural (volcanoes, mineral deposits), but primarily industrial (coal-fired utilities, waste incinerators, etc.).
(The source of the mercury; is; in part natural (volcanoes, mineral deposits), but primarily industrial (coal-fired utilities, waste incinerators, etc.)
The source of the mercury
is
in part natural (volcanoes, mineral deposits), but primarily industrial (coal-fired utilities, waste incinerators, etc.