983628 - Black Carbon Atmospheric Emission Inventory of the Road Transport Sector in Portillo, Chilean Central Andes

Black Carbon (BC) is a byproduct emitted by incomplete fossil fuel combustion and biomass burning. It has a strong influence on radiative forcing, and when it is deposited on the cryosphere leads to enhanced melting rates. In this sense, the development of an atmospheric emissions inventory (AEI) can provide valuable information to be used in making decisions regarding mitigation measures and in climate models that allow evaluating its effects quantitatively. In this work, an AEI of the road transport sector has been developed for an area from the Chilean Central Andes, named Portillo (32.84°S, 70.13° W, 3000 m.a.s.l), located in the international border between Chile and Argentina, for the period October 2016-December 2019, with monthly temporal resolution. In this zone of the Andean cryosphere, local vehicular traffic coming from the road connecting Chile and Argentina has been identified previously as the main emission source of atmospheric BC, considering that for this road circulates most of trucks transporting goods between these countries. The “bottom up” approach was implemented, following the Tier 2 Method proposed by the European Monitoring and Evaluation Programme/European Environment Agency, Emissions Inventory Guidebook 2019 (EMEP/EEA EIG). The activity level (vehic month-1) was calculated from vehicular traffic information provided by the Chilean National Service of Customs, comprising monthly number of passenger cars, buses, and trucks. Buses and trucks were considered all with diesel engines, while passenger cars category was subdivided into gasoline or diesel engines, using data on the composition of the vehicle fleet from Chile and Argentina, resulting in 80% and 20% of total cars, respectively. Cars, SUVs and pickups vans for private use were included in this category. Emission factors (g vehic-1 km-1) by category were taken from the EMEP/EEA EIG 2019, considering a variety of emission technologies according to the vehicular fleet of both countries. Monthly atmospheric emissions of BC were obtained (in g month-1 km-1), which were not multiplied by a specific distance and they are expressed by km, since they are expected to be used in dispersion models with different spatial coverage, and in this way, they could be adapted to each case. Calculated total monthly BC emissions varied between 26.6 and 108.5 g month-1 km-1, with a mean value of 52.2 ± 18.2 g month-1 km-1. BC emission exhibited a seasonal pattern, where summer months presented higher levels, dominated by the contribution of passenger cars (63%), while in winter the major contribution came from trucks (62%). Trucks emissions presented a low variability with 22.3 ± 1.6 g month-1 km-1, while passenger cars (sum of diesel and gasoline) showed a strong variability with an average of 26.9 ± 17.4 g month-1 km-1. Emissions calculated were in agreement with BC atmospheric measurements performed in the study area by the authors, where the Pearson correlation coefficient (r) for the mean monthly measured levels of atmospheric BC (µg m-3) and the here calculated BC monthly emission reached 0.78, suggesting a good approach of the emissions estimation.
Acknowledgments: Projects ANID-FONDECYT Postdoc 3190513, ANID-FONDEF ID19I10359 and PI_M_2020_58 from UFSM.