Emission Evolutions Characteristics Of Air Pollutants In Guangdong Province And Their Impacts On Air Quality

With the rapid economic development and urbanization in Guangdong Province,energy consumption and emissions have increased dramatically,leading to the frequent emergence of regional complex air pollutants for smog and haze characterized by high ozone?O₃?levels.These episodes severly reduce visibility and threat human health.In response to the persistent deterioration of air quality,the national and local governments have made great efforts to formulate a series of policies and control measures to reduce emissions.These measures have resulted in the significant improvement of air quality in Guangdong Province.However,the PM_2.5 levels still frequently exceed the limit recommended by the World Health Organization?WHO?;the O₃ levels were almost unchanged and even elevated.In order to realize the overall improvement of the air quality for various pollutants,it is imperative to establish a comprehensive systematic inter-annual emission inventory and fully review the pollution policy measures have been issued over past decades,for analyzing effectiveness and potentials of emission reductions and explaining the reasons of variations in air quality,hoping to better guide further air pollution prevention actions.Given all that,emission trends of air pollutants in Guangdong Province from 2006 to 2015were firstly developed and then validated via multi-source observations.Also,relocations of some pollutant emissions within Guangdong Province were ascertained by comparing the differences and their reasons in emission characteristics between the Pearl River Delta?PRD?and non-Peral River Delta?Non-PRD?.Results demonstrated that the emissions of most of the pollutants presented declining trends throughout GD with the exception of volatile organic compounds?VOCs?and ammonia?NH₃?,which continued to grow and remained constant,respectively.The observed decreases were mainly attributable to reductions in the PRD,especially those from power plants,industrial combustion and on-road mobile source.Nevertheless,emissions in the non-PRD decreased to a lesser extent or even increased for some pollutants,such as SO₂ emissions from industrial combustion and NO_X emissions from power plants;these indicated that some energy-and pollution-intensive industries were relocated into this less-developed area.Secondly,predictions for 2020 were also conducted under scenarios both with and without control regulations to quantify the reduction gains and potentials.Results showed control measures on power plants,industrial combustion and on-road mobile sources exhibited the most reduction gains over the past few years,and the overall reduction gains of the non-PRD were weaker than those in the PRD.Large reduction potentials still exist for power plants,non-road mobile source,on-road mobile source,dust source and VOCs-related sources,and the reduction potentials in the non-PRD were higher than those in the PRD.Finally,the WRF/SMOKE/CMAQ model combined emission inventories during 2006-2015 and meteorological data in 2013 were applied to analyze the impacts of emission trends on air quality.The simulation results showed the levels of SO₂ in the PRD during 2006-2015reduced by⁴8%;from 2006 to 2010,the levels of SO₂ in non-PRD increased by⁷%,and it decreased by⁴%during 2010-2015.The levels of NO₂ in the PRD decreased by¹%during2006-2010,and continually reduced by¹0%during 2006-2011;from 2006 to 2011,the levels of NO₂ in the non-PRD increased by²5%,and then decreased by¹%during 2006-2015.The levels of PM_2.5 in the PRD increased¹%during 2006-2009,and decreased by¹9%during2009-2015;its levels in the non-PRD increased by²%during 2006-2009,and decreased by¹1%during 2009-2015.These changes in the concentrations of air pollutants were consistent with according emission trends and their proportions,indicating that emission variations during2006-2015 had great impacts on air quality.In addition,there were discrepancies in inter-annual O₃-8h-90%concentrations in different seasons.It was extremely effective to relieve O₃ levels if VOCs-foused controls were adopted in October,January and NO_X-foused controls in July,April.Moreover,short-term despiking and long-term attainment for O₃ in the PRD were successful as a result of VOCs-and NO_X-focused controls,respectively.