Atmospheric Chemistry and Physics | 2019
Quantification and evaluation of atmospheric pollutant emissions from open biomass burning with multiple methods: a case study for the Yangtze River Delta region, China
Abstract
Abstract. Air pollutant emissions from open biomass burning (OBB) in the\nYangtze River Delta (YRD) were estimated for 2005–2015 using three\n(traditional bottom-up, fire radiative power (FRP), and constraining)\napproaches, and the differences among those methods and their sources were\nanalyzed. The species included PM 10 , PM 2.5 , organic carbon (OC),\nelemental carbon (EC), CH4 , non-methane volatile organic compounds\n(NMVOCs), CO, CO2 , NOx , SO2 and NH3 .\nThe interannual trends in emissions with FRP-based and constraining methods\nwere similar to the fire counts in 2005–2012, while those with the\ntraditional method were not. For most years, emissions of all species\nestimated with the constraining method were smaller than those with the\ntraditional method except for NMVOCs, while they were larger than those with\nthe FRP-based method except for EC, CH4 and NH3 . Such\ndiscrepancies result mainly from different masses of crop residue burned in\nthe field (CRBF) estimated in the three methods. Chemistry transport modeling\n(CTM) was applied using the three OBB inventories. The simulated PM 10 \nconcentrations with constrained emissions were closest to the available\nobservations, implying that the constraining method provided the best\nemission estimates. CO emissions in the three methods were compared with\nother studies. Similar temporal variations were found for the constrained\nemissions, FRP-based emissions, GFASv1.0 and GFEDv4.1s, with the largest and\nthe lowest emissions estimated for 2012 and 2006, respectively. The temporal\nvariations in the emissions based on the traditional method, GFEDv3.0, and\nthe method of Xia et al.\xa0(2016) were different. The constrained CO emissions\nin this study were commonly smaller than those based on the traditional\nbottom-up method and larger than those based on burned area or FRP in other\nstudies. In particular, the constrained emissions were close to GFEDv4.1s\nthat contained emissions from small fires. The contributions of OBB to two\nparticulate pollution events in 2010 and 2012 were analyzed with the\nbrute-force method. Attributed to varied OBB emissions and meteorology, the\naverage contribution of OBB to PM 10 concentrations in 8–14\xa0June 2012\nwas estimated at 37.6\u2009% (56.7\u2009 µ g\u2009m −3 ), larger than that\nin 17–24\xa0June 2010 at 21.8\u2009% (24.0\u2009 µ g\u2009m −3 ). Influences\nof diurnal curves of OBB emissions and meteorology on air pollution caused by\nOBB were evaluated by designing simulation scenarios, and the results\nsuggested that air pollution caused by OBB would become heavier if the\nmeteorological conditions were unfavorable and that more attention should be\npaid to the OBB control at night. Quantified with Monte Carlo simulation, the\nuncertainty of the traditional bottom-up inventory was smaller than that of\nthe FRP-based one. The percentages of CRBF and emission factors were the main\nsource of uncertainty for the two approaches. Further improvement on CTM for\nOBB events would help better constrain OBB emissions.