郑州市细颗粒物时空差异及管控措施影响

为研究郑州市细颗粒物（PM_2.5）时空分布差异及秋冬季管控措施影响，于2017年秋季至2018年冬季选取5个点位采集PM_2.5样品并进行组分分析，利用正定矩阵因子分解模型（PMF）解析PM_2.5污染来源，评估郑州市秋冬季管控效果，并基于源解析结果为下一阶段秋冬季管控提供支撑.郑州市PM_2.5浓度冬季 > 秋季 > 春季 > 夏季，郑州大学（ZZU）PM_2.5浓度最高［（83.1±44.7）μg·m^-3］，高出平均浓度［（76.5±46.1）μg·m^-3］的8.7%.SO₄^2-、NO₃^-和NH₄⁺在9种水溶性离子中平均占比高达22.5%、43.6%和23.4%，受燃煤影响Cl^-两年冬季占比高于其他季节（6.7%和6.6%）.秋冬季二次有机碳（SOC）污染严重，浓度占有机碳的一半以上，2018年市监测站（JCZ）和ZZU点位SOC/OC比2017年有所下降，但其他3个点位大幅度升高，说明这些地区不同的排放基础应对管控措施的表现不尽相同.重构结果表明硫酸盐占比在夏季最高（25.0%），硝酸盐两年秋季占比较高（23.1%和25.1%），地壳物质春季占比最高（18.2%），二次有机气溶胶（SOA）冬季最高（14.1%和20.5%）；JCZ和航空港（HKG）点位SOA贡献较大（16.9%和16.4%），ZZU点位受到一次有机气溶胶和地壳物质影响较大（14.3%和12.1%）.PMF结果表明二次无机盐（37.5%）、SOA（15.4%）、交通源（14.9%）、工艺过程源（4.8%）、燃煤源（16.0%）、扬尘源（6.5%）和生物质燃烧源（2.8%）是郑州市PM_2.5的主要污染源，SOA和燃煤源在冬季贡献最大，扬尘源和生物质燃烧源在春季和秋季贡献较大；市区点位JCZ、ZZU和临近机场的HKG受到交通源的影响高于其他点位，非市区点位新密和HKG受到生物质燃烧源的影响较大.对比两年秋冬季，2018年秋冬季SOA、交通源和工艺过程源的贡献有所升高，而二次无机盐、燃煤源和生物质燃烧源有所下降，冬季扬尘源也有所下降.结果表明秋冬季管控措施对一次源中的扬尘、燃煤和工业效果显著，同时SOA前体物挥发性有机物是进一步减排管控的方向.

Spatiotemporal Variations in Fine Particulate Matter and the Impact of Air Quality Control in Zhengzhou

To study the spatiotemporal variations in fine particulate matter (PM_2.5) and the impact of air quality management in autumn and winter in Zhengzhou, five sites were selected to collect PM_2.5 samples from the autumn of 2017 to the winter of 2018, and the characteristics of the chemical components were analyzed. The positive matrix factorization (PMF) model was also applied to identify the sources of PM_2.5, and the effect of air quality control was evaluated to provide support for air quality control in autumn and winter in the next stage. The PM_2.5 concentrations in the four seasons in Zhengzhou were ranked as winter > autumn > spring > summer. The PM_2.5 concentration at Zhengzhou University (ZZU) was the highest (8.7% higher than the average concentration), and the PM_2.5 concentrations at the other sites were slightly lower than the average concentration. The concentration of water-soluble ions (WSIs) was low in spring and summer and high in autumn and winter. The average proportions of SO₄^2-, NO₃^-, and NH₄⁺ in the nine WSIs were as high as 22.5%, 43.6%, and 23.4%, respectively. The proportion of Cl^- in winter was higher than that in the other seasons owing to coal combustion (6.7% and 6.6% in 2017 and 2018, respectively). Owing to wind and sand, the proportions of Ca²⁺ and Mg²⁺ in spring were the highest (4.4% and 0.4%, respectively), and those at the Jiancezhan (JCZ) and ZZU sites were higher than those at the other sites. K⁺, as a marker of biomass burning, had a higher proportion in spring, autumn, and winter. The proportion of K⁺ in the spring of 2018 was 1.9%, those in the autumn and winter of 2017 were 1.6% and 2.1%, respectively, and those in the autumn and winter of 2018 were 1.3% and 1.8%, respectively. JCZ, Hangkonggang (HKG), and Xinmi (XM) had higher proportions of NO₃^-, and the proportions of SO₄^2- were lower. Secondary organic carbon (SOC) pollution was serious in autumn and winter, and the concentration accounted for more than half of the organic carbon (OC). In 2018, the SOC/OC at the JCZ and ZZU sites decreased compared with that in 2017, but that at the other three sites increased significantly, thereby indicating that different air pollutant emissions in these regions had different performances in response to control policies. The chemical composition reconstruction results showed that the proportion of sulfate was highest in summer (25.0%), the contribution of nitrate was higher in autumn (23.1% and 25.1% for 2017 and 2018, respectively) and winter (20.6% and 23.0% for 2017 and 2018, respectively), the proportion of crustal material was higher in spring (18.2%), and the contribution of secondary organic aerosol (SOA) was the highest in winter (14.1% and 20.5% for 2017 and 2018, respectively). SOA had higher contributions at the JCZ and HKG sites (16.9% and 16.4%, respectively), and ZZU was affected more by primary organic aerosol (14.3%) and crustal materials (12.1%). The PMF results showed that secondary inorganic salts (37.5%), SOA (15.4%), traffic (14.9%), industry (4.8%), coal combustion (16.0%), fugitive dust (6.5%), and biomass burning (2.8%) were the main pollution sources of PM_2.5 in Zhengzhou. SOA and coal combustion contributed more in winter and fugitive dust contributed more in spring, followed by autumn. Biomass burning contributed more in spring and autumn. The urban sites JCZ and ZZU and the characteristic site HKG near the airport were more affected by traffic sources (16.9%, 16.2%, and 16.0%, respectively) than the other sites. The impact of biomass burning on the non-urban sites XM and HKG was slightly larger (both 2.7%), and the contribution of coal combustion to the suburban site XM was higher (16.8%). Owing to the construction around ZZU, the loading of fugitive dust at ZZU was higher than that at other sites. Comparing the results of the two-year autumn and winter, the contribution of SOA, traffic, and industry increased in the autumn and winter of 2018, whereas the contribution of secondary inorganic salts, coal combustion, and biomass burning decreased and the contribution of fugitive dust in winter also decreased. The results showed that the control strategies in autumn and winter had significant effects on the primary sources, including fugitive dust, coal combustion, and industry, and SOA precursor volatile organic compounds should be targeted for further pollution control.