基于2012—2018年内江市PM2.5化学组分变化对《大气污染防治行动计划》实施效果的评估

2013年9月国务院发布了《大气污染防治行动计划》（简称"《气十条》"）.基于《气十条》实施前期（2012年5月-2013年5月）和实施后期（2015年9月-2016年9月）在四川省内江市采集的PM_2.5及其化学组分，以及2013-2018年空气自动监测站在线监测数据，通过比较分析PM_2.5中WSIIs（water-soluble inorganic ions，水溶性离子）和6项常规污染物质量浓度的变化来评估《气十条》实施效果，同时应用PMF（positive matrix factorization，正矩阵因子分析法）模型解析WSIIs源变化以探究空气污染源的改变.结果表明:①2018年内江市ρ（SO₂）、ρ（NO₂）、ρ（PM₁₀）、ρ（PM_2.5）、ρ（O₃）和ρ（CO）年均值分别为9.4 μg/m3、23.9 μg/m3、53.1 μg/m3、34.9 μg/m3、140.0 μg/m3和1.1 mg/m3，6项污染物首次全部达到GB 3095-2012《环境空气质量标准》二级标准.②《气十条》实施后期ρ（PM₁₀）和ρ（PM_2.5）分别为（74.5±55.1）（63.0±47.0）μg/m3，较实施前期分别下降了36%和20%，说明《气十条》的实施明显改善了空气质量.PM_2.5中ρ（SO₄2-）和ρ（NO₃-）分别下降了47%和25%，表明SO₂和NO_x的排放均得到有效控制；PM_2.5中ρ（K+）和ρ（Mg2+）分别增加了66%和92%，这与春节期间燃放烟花爆竹和生物质燃烧有关，因此应加强对重点时段特殊事件的管控.③相较《气十条》实施前期，实施后期ρ（PM_2.5）/ρ（PM₁₀）由0.69升至0.84，SOR（sulfate oxidation ratio，硫氧化率）由0.22增至0.25，说明PM_2.5和二次污染占比增加.④PMF模型解析结果发现，与《气十条》实施前期相比，实施后期的燃煤-工业源、二次硫酸盐、二次硝酸盐和扬尘源对ρ（PM_2.5）的贡献量下降，生物质燃烧源对ρ（PM_2.5）的贡献量增加；燃煤-工业源和二次硫酸盐对ρ（PM_2.5）的贡献率之和大幅下降，二次硝酸盐和生物质燃烧的贡献率均升高.研究显示，《气十条》的实施使内江市燃煤和工业排放得到显著控制，但机动车和生物质燃烧尚需严控. 

Evaluation of Effects of Air Pollution Prevention and Control Action Plan Based on Variations of Chemical Components in PM2.5 during 2012-2018 in Neijiang City

The State Council issued the Air Pollution Prevention and Control Action Plan (APPCAP) in September 2013. The effects of APPCAP in Neijiang City, Sichuan Province was evaluated by comparing the variations of WSIIs (water-soluble inorganic ions) mass concentrations in PM_2.5 before (from May 2012 to May 2013) and in the later period (from September 2015 to September 2016) of the policy implementation. In addition, the temporal variations of six criteria air pollutant mass concentrations obtained from automatic monitoring stations during 2013-2018 were also used to evaluate the effectiveness of APPCAP. In order to explore the changes of air pollution sources, PMF (positive matrix factorization) model was applied to identify the variation of WSIIs source. The results showed that:(1) The annual average mass concentrations of SO₂, NO₂, PM₁₀, PM_2.5, O₃, and CO in 2018 were 9.4 μg/m3, 23.9 μg/m3, 53.1 μg/m3, 34.9 μg/m3, 140.0 μg/m3 and 1.1 mg/m3, respectively. It was the first time that all six air pollutants reached the Grade Ⅱ of National Ambient Air Quality Standards (GB 3095-2012). (2) The mass concentrations of PM₁₀ and PM_2.5 were (74.5±55.1) and (63.0±47.0)μg/m3, respectively, in the later period of the policy implementation, which was 36% and 20% lower than those before the policy implementation, indicating that APPCAP has significantly improved the air quality in Neijiang City. The mass concentrations of SO₄2- and NO₃- in PM_2.5 decreased by 47% and 25%, suggesting both SO₂ and NO_x emissions were effectively controlled. K+ and Mg2+ in PM_2.5 increased by 66% and 92%, respectively, which were related to fireworks during the Spring Festival and biomass burning in May. So it is necessary to strengthen the control of these special incidents. (3) Before and in the later period of the policy implementation, the ratio of PM_2.5/PM₁₀ increased from 0.69 to 0.84, and SOR (sulfate oxidation ratio) increased from 0.22 to 0.25, showing that the proportions of PM_2.5 and secondary pollution increased. (4) Compared with results from PMF model before the policy implementation, the contributions of coal combustion-industrial source, secondary sulfate, secondary nitrate and dust to PM_2.5 mass concentrations decreased in the later period of the policy implementation, whereas the contribution of biomass burning to PM_2.5 mass concentrations increased. The total contribution rate of coal combustion-industrial source and secondary sulfate to PM_2.5 decreased dramatically, whereas the contribution rates of secondary nitrate and biomass burning increased. The results suggested that the emissions from coal combustion and industry were controlled remarkably due to the implementation of the APPCAP, but motor vehicles and biomass burning need to be strictly controlled.