Environmental Engineering Reference
In-Depth Information
Atmospheric Modification to Other Biogeochemical
Components
Atmospheric Biota
Atmospheric aerosols are likely to be composed in part by primary biogenic
particles, or particles derived from the biota, for example, plant or insect bits,
pollen, bacteria, or viruses [
108
]. Recent estimates suggest less than 5% of the
aerosols are primary biogenic particles [
109
]. Some small fraction of these biogenic
aerosols may contain viable living cells. While estimates of culturable bacteria are
dependent on the methods used, estimates suggest that some bacteria do remain
viable in the atmosphere, and can perhaps grow again if deposited onto the ground
[
110
,
111
]. Clearly, plants depend on pollen, and fungi on spores, to move genetic
material from one place to another, and some fraction of this pollen and spores can
be carried far from the source [
112
]. The amount of viable biota moving through the
atmosphere and the importance of this process for global biogeochemical cycling is
not well understood, but deserves future study.
Climate Modification of Biogeochemical Cycles
Changes in atmospheric biogeochemistry can modify climate, which in turn can
also modify land and ocean biogeochemistry. This feedback has been used as
a mechanism for understanding how carbon dioxide can be modulated on long
timescales. For example, it is hypothesized that there are higher temperatures and
more precipitation on land during higher carbon dioxide levels, thus increasing
weathering [
113
]. This will reduce the atmospheric concentrations of carbon
dioxide levels, acting as a feedback to prevent a runaway green house effect [
113
].
In the anthropocene, modeling studies have suggested that changes in anthropo-
genic aerosols and mineral aerosol particles can modify precipitation, incoming
solar radiation, and temperature, and therefore modify land and ocean biogeochem-
istry enough to be seen at the global level [
89
,
90
,
114
,
115
].
The Atmosphere as an Integrator
The atmosphere is the one part of the earth system that is transparent in many
wavelengths of light, and thus can be readily observed using remote sensing
methods. In addition, we live at the interface of the atmosphere and land surface,
and thus have easy access to the lower layers of the atmosphere. This means
that we have much better observations of the state of many biogeochemical
cycles in the atmosphere, than in the land or ocean [
16
]. Thus understanding
