Abstract:

The size distribution of the chemical components of particulate matter in the atmosphere is closely related to its source, formation process, environment, and health effects. There are relatively few studies on the characteristics of the particle size distribution of particulate matter in different seasons and the contribution of different sources to coarse and fine particulate matter. Size-resolved aerosol samples were collected in Nanjing during December 2022 (winter) and August 2023 (summer). Samples of coarse and fine particulate matter (PM_2.1-10, PM_2.1) were further analyzed for their carbonaceous compositions and water-soluble inorganic ions. The size distributions and seasonal variations of all the species were characterized. The potential sources of aerosols were quantified using the positive matrix factorization (PMF) model. The results showed that organic carbon (OC), elemental carbon (EC), and water-soluble organic carbon (WSOC) had bimodal distributions in both seasons. Both SO₄²⁻ and NO₃⁻ showed a bimodal distribution during the warm and cold seasons. NH₄⁺ exhibited a unimodal distribution, peaking at 0.43-0.65 μm in both seasons. Regarding the seasonal variation, the concentrations of the main chemical species were higher in winter, with the exception of Na⁺ and SO₄²⁻. Markers of crustal materials, such as Ca²⁺ and Mg²⁺, were mainly found in the coarse mode during summer and winter. Finally, four emission sources were resolved using the PMF model. The results showed that secondary aerosols and biomass burning were the dominant sources of PM_2.1, accounting for 65.7% and 61.0% in winter and summer, respectively. Biomass burning and secondary nitrate dominated PM_2.1 pollution in winter, while secondary sulfate was a major source in summer. For PM_2.1-10, traffic emissions were a major source in winter, with a share of 41.8%. In contrast, biomass burning and secondary nitrate were the main sources of PM_2.1-10 in the summer, contributing approximately 43.9% of the PM_2.1-10 masses. This study investigated the characteristics of the particle size distribution, seasonal variations, and sources of the chemical components of particulate matter, which can provide a scientific basis for the effective prevention and control of air pollution.

Key words: atmospheric particulate matter, carbonaceous aerosol, water-soluble ions, size distribution, seasonal variation, positive matrix factorization

摘要：

大气颗粒物中化学组分的粒径分布与其来源、形成过程、环境及健康效应密切相关。而过去对不同季节颗粒物的粒径分布特征，以及不同来源对粗、细颗粒物的贡献的研究相对较少。于2022年12月（冬季）和2023年8月（夏季）在南京采集了大气分粒径颗粒物样品，分析了粗颗粒物（PM_2.1-10）和细颗粒物（PM_2.1）中碳质组分和主要水溶性无机离子的粒径分布和季节变化，运用正定矩阵因子分解模型（Positive Matrix Factorization，PMF）进行PM_2.1-10和PM_2.1的源解析。结果表明，在粒径分布特征上，冬夏两季有机碳（OC）、元素碳（EC）、水溶性有机碳（WSOC）的平均浓度呈双峰型分布。SO₄²⁻和NO₃⁻的季节平均浓度均为双峰型分布。NH₄⁺主要分布在细颗粒物中，季节平均浓度呈单峰型分布，冬夏季均在0.43－0.65μm出现峰值。在季节变化上，颗粒物中除Na⁺和SO₄²⁻外的主要化学组分浓度均在冬季高于夏季。冬夏两季Ca²⁺、Mg²⁺主要集中在粗颗粒物中。根据PMF模型解析结果，南京大气颗粒物主要有4类来源贡献，即交通源、二次生成、生物质燃烧和扬尘源。PM_2.1主要来自二次生成和生物质燃烧源，冬夏季分别贡献了65.7%和61.0%，其中冬季生物质燃烧和二次硝酸盐的贡献占主导地位，而夏季主要来自二次硫酸盐的贡献。冬季PM_2.1-10主要来自交通源（41.8%），夏季则主要来自生物质燃烧和硝酸盐的二次生成贡献（43.9%）。研究探讨了大气颗粒物的化学组分的粒径分布特征、季节差异及来源，可为制定有针对性的大气污染防控措施提供科学依据。

关键词: 大气颗粒物, 碳质气溶胶, 水溶性离子, 粒径分布, 季节差异, 正定矩阵因子分解模型