Chemistry Reference
In-Depth Information
Fig. 8
Upper
: CTM model results for PM10 levels.
Lower
: relative shares of sources in percent-
age compared to base run. (a, c) German sources on, foreign sources off; (b, d) German sources
off, foreign sources on; from [
29
] with permission from publisher
3.3 Main Sources and Processes in Detail
3.3.1 Natural Sources
On the global scale, natural emissions of particulate matter from wildfires,
volcanoes, sea spray, wind erosion and the biosphere are estimated to exceed by
far the emissions by anthropogenic activities (Hainsch [
31
] quoting Warneck [
47
]).
In densely populated and industrialised countries like Germany this relation
changes and on average natural aerosols are thought to play a minor role compared
to anthropogenic particle emissions. However, short-term events like volcano
eruptions [
48
] and trans-boundary dust intrusions from arid areas (Fig.
9
) have
sporadically led to elevated PM concentrations in parts of Germany [
49
].
Besides such high PM events, more frequent natural contributions to PM mass
concentrations may occur from biogenic particles [
50
] and from sea salt.
Biogenic particles which comprise primary (fungal spores, bacteria, viruses, plant
debris) and secondary organic aerosol (SOA) from biogenic non-methane VOCs are
part of the commonly measured organic carbon fraction. Model results [
51
] indicate a
