Technical note: Emission mapping of key sectors in Ho Chi Minh City, Vietnam, using satellite-derived urban land use data

Abstract

Abstract. Emission inventories are important for both simulating pollutant\nconcentrations and designing emission mitigation policies. Ho Chi Minh City\n(HCMC) is the biggest city in Vietnam but lacks an updated spatial\nemission inventory (EI). In this study, we propose a new approach to update\nand improve a comprehensive spatial EI for major short-lived climate\npollutants (SLCPs) and greenhouse gases (GHGs) ( SO2 , NOx , CO, non-methane volatile organic compounds (NMVOCs), PM 10 ,\nPM 2.5 , black carbon (BC), organic carbon (OC), NH3 , CH4 , N2O and CO2 ). Our originality is the use of\nsatellite-derived urban land use morphological maps which allow spatial\ndisaggregation of emissions. We investigated the possibility of using freely\navailable coarse-resolution satellite-derived digital surface models (DSMs) to\nestimate building height. Building height is combined with urban built-up\narea classified from Landsat images and nighttime light data to generate\nannual urban morphological maps. With outstanding advantages of these remote\nsensing data, our novel method is expected to make a major improvement in\ncomparison with conventional allocation methodologies such as those based on\npopulation data. A comparable and consistent local emission inventory (EI)\nfor HCMC has been prepared, including three key sectors, as a successor of\nprevious EIs. It provides annual emissions of transportation, manufacturing\nindustries, and construction and residential sectors at 1\u2009km resolution. The\ntarget years are from 2009 to 2016. We consider both Scope\xa01, all direct\nemissions from the activities occurring within the city, and Scope\xa02, that is\nindirect emissions from electricity purchased. The transportation sector was\nfound to be the most dominant emission sector in HCMC followed by\nmanufacturing industries and residential area, responsible for over 682\u2009Gg\u2009CO, 84.8\u2009Gg\u2009 NOx , 20.4\u2009Gg\u2009PM 10 and 22\u2009000\u2009Gg\u2009 CO2 emitted in 2016. Due to a sharp\nrise in vehicle population, CO, NOx , SO2 and CO2 traffic emissions show\nincreases of 80\u2009%, 160\u2009%, 150\u2009% and 103\u2009% respectively between 2009\nand 2016. Among five vehicle types, motorcycles contributed around 95\u2009% to\ntotal CO emission, 14\u2009% to total NOx emission and 50\u2009%–60\u2009% to CO2 \nemission. Heavy-duty vehicles are the biggest emission source of NOx , SO2 and particulate matter (PM)\nwhile personal cars are the largest contributors to NMVOCs and CO2 .\nElectricity consumption accounts for the majority of emissions from\nmanufacturing industries and residential sectors. We also found that Scope\xa02\nemissions from manufacturing industries and residential areas in 2016\nincreased by 87\u2009% and 45\u2009%, respectively, in comparison with 2009. Spatial\nemission disaggregation reveals that emission hotspots are found in central\nbusiness districts like Quan\xa01, Quan\xa04 and Quan\xa07, where emissions can be\nover 1900 times those estimated for suburban HCMC. Our estimates show\nrelative agreement with several local inherent EIs, in terms of total amount\nof emission and sharing ratio among elements of EI. However, the big gap was\nobserved when comparing with REASv2.1, a regional EI, which mainly applied\nnational statistical data. This publication provides not only an approach\nfor updating and improving the local EI but also a novel method of spatial\nallocation of emissions on the city scale using available data sources.