25th International Meeting on Organic Geochemistry IMOG 2011

P-005
A Monte Carlo application for introducing source variability in
source apportionment calculations
August Andersson 1 , Rebecca Sheesley 1,2 , Jorien Vonk 1,3 , Örjan Gustafsson 1
1 Stockholm University, Stockholm, Sweden, 2 Baylor University, Waco, United States of America, 3 ETH,
Zurich, Switzerland (corresponding author:august.andersson@itm.su.se)
End-member mixing analysis (EMMA) using e.g.
molecular and isotopic markers are commonly used to
decipher the relative contributions from different
sources to a mixed environmental sample. By setting
up a set of linear equations with N+1 sources and N
source markers, the relative source contributions may
be solved analytically. A major drawback of that
standard approach is that the natural variability of the
source markers (the end-members) is not taken into
account. Here a Monte Carlo approach for accounting
of the end-member variability in source calculations is
presented.
This methodology is exemplified by two applications:
1. Apportioning relative contributions to organic
carbon (OC) in Arctic Ocean surface sediments from
marine, riverine and erosion sources using 13C and
14C isotope [1]. Interestingly, the erosion component
was found to be around 50%, irrespective of the
distance of the sampling site to the Kolyma river
mouth, Figure 1.
2. Apportioning relative contributions to carbonaceous
aerosols in southern Asia from biomass combustion,
liquid petroleum combustion and coal combustion
using various polyaromatic hydrocarbon (PAH)
signals as molecular source markers [2]. This study
shows that the fossil fuel contribution is roughly
equally split between petroleum- and coal combustion
sources.
Taken together, these results points to the general
conclusion that source variability influences both the
calculated relative contributions from different sources
and the precision by which it may be calculated. This
conclusion is reinforced by analysis of synthetic data
sets, designed to span the main source configurations
possible.
Figure 1 Relative contributions (with error bars) of
riverine, erosion and marine contributions to OC in
surface sediments along the Kolyma paleoriver.
References
[1] Vonk, J. et al. (2010) Biogeosciences, 7, 3153-
3166
[2] Sheesley, R. et al. (2011) Atmospheric
Environment, Accepted for publication.
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