Evaluating BC and NOx emission inventories for the Paris region from MEGAPOLI aircraft measurements

摘要

High uncertainties affect black carbon (BC) emissions, and, despite itsimportant impact on air pollution and climate, very few BC emissionsevaluations are found in the literature. This paper presents a novelapproach, based on airborne measurements across the Paris, France, plume,developed in order to evaluate BC and NO emissions at the scale of awhole agglomeration. The methodology consists in integrating, for eachtransect, across the plume observed and simulated concentrations abovebackground. This allows for several error sources (e.g., representativeness, chemistry, plume lateral dispersion) to be minimized in the model used. Theprocedure is applied with the CHIMERE chemistry-transport model to threeinventories – the EMEP inventory and the so-called TNO and TNO-MPinventories – over the month of July 2009. Various systematic uncertaintysources both in the model (e.g., boundary layer height, vertical mixing,deposition) and in observations (e.g., BC nature) are discussed andquantified, notably through sensitivity tests. Large uncertainty values aredetermined in our results, which limits the usefulness of the method torather strongly erroneous emission inventories. A statistically significant(but moderate) overestimation is obtained for the TNO BC emissions and theEMEP and TNO-MP NO emissions, as well as for the BC / NO emission ratioin TNO-MP. The benefit of the airborne approach is discussed through acomparison with the BC / NO ratio at a ground site in Paris, whichadditionally suggests a spatially heterogeneous error in BC emissions overthe agglomeration.