Statistical atmospheric inversion of local gas emissions by coupling the tracer release technique and local-scale transport modelling: a test case with controlled methane emissions
This study presents a new concept for estimating the pollutant emission rates of a site and its main facilities using a series of atmospheric measurements across the pollutant plumes. This concept combines the tracer release method, local-scale atmospheric transport modelling and a statistical at...
Main Authors: | , , , , , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2017-12-01
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Series: | Atmospheric Measurement Techniques |
Online Access: | https://www.atmos-meas-tech.net/10/5017/2017/amt-10-5017-2017.pdf |
Summary: | This study presents a new concept for estimating the pollutant emission rates
of a site and its main facilities using a series of atmospheric measurements
across the pollutant plumes. This concept combines the tracer release method,
local-scale atmospheric transport modelling and a statistical atmospheric
inversion approach. The conversion between the controlled emission and the
measured atmospheric concentrations of the released tracer across the plume
places valuable constraints on the atmospheric transport. This is used to
optimise the configuration of the transport model parameters and the model
uncertainty statistics in the inversion system. The emission rates of all
sources are then inverted to optimise the match between the concentrations
simulated with the transport model and the pollutants' measured atmospheric
concentrations, accounting for the transport model uncertainty. In principle,
by using atmospheric transport modelling, this concept does not strongly rely
on the good colocation between the tracer and pollutant sources and can be
used to monitor multiple sources within a single site, unlike the classical
tracer release technique. The statistical inversion framework and the use of
the tracer data for the configuration of the transport and inversion
modelling systems should ensure that the transport modelling errors are
correctly handled in the source estimation. The potential of this new concept
is evaluated with a relatively simple practical implementation based on a
Gaussian plume model and a series of inversions of controlled methane point
sources using acetylene as a tracer gas. The experimental conditions are
chosen so that they are suitable for the use of a Gaussian plume model to
simulate the atmospheric transport. In these experiments, different
configurations of methane and acetylene point source locations are tested to
assess the efficiency of the method in comparison to the classic tracer
release technique in coping with the distances between the different methane
and acetylene sources. The results from these controlled experiments
demonstrate that, when the targeted and tracer gases are not well collocated,
this new approach provides a better estimate of the emission rates than the
tracer release technique. As an example, the relative error between the
estimated and actual emission rates is reduced from 32 % with the tracer
release technique to 16 % with the combined approach in the case of a tracer
located 60 m upwind of a single methane source. Further studies and more
complex implementations with more advanced transport models and more advanced
optimisations of their configuration will be required to generalise the
applicability of the approach and strengthen its robustness. |
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ISSN: | 1867-1381 1867-8548 |