Chemistry Reference
In-Depth Information
Fig. 2 Illustration of the “spatial increment” approach according to Lenschow et al. [
3
]
2.2 Lenschow Approach
The basic increment approach described before has further been extended [
3
]to
include chemical composition data (for the major compounds) as well as emission
inventories for the corresponding areas. Using this data, the measured compound
concentrations are apportioned according to the relative shares of the corresponding
emissions for each environment.
The Lenschow method has become particularly attractive for Germany's air
quality management authorities (e.g. [
4
]) since it directly relates measured PM
levels to source categories listed in official emission inventories. For example,
measured regional levels for elemental carbon (EC) are distributed according to
the shares of various EC emission sources registered in the national emission
inventory. Similarly, the urban increments are related to the urban emission register.
The local increment, e.g. measured at a traffic site, is considered to be exclusively
caused by the local traffic emissions, if chemical composition does not indicate
otherwise. Similar computation is performed for all other measured compounds.
Clearly, the validity of the result depends on the accuracy and completeness of the
emission registers. Moreover, for some source types the distribution depends on
assumptions that may be considerably uncertain (e.g. tailpipe/non-tailpipe traffic
emissions). Natural sources as well as contributions by trans-boundary long-range
transport are not always included, which may cause overestimation of the relative
contributions by national emission sources [
5
].
