The regional nature of nitrate-dominant haze pollution during autumn over the Pearl River Delta area

ABSTRACT

China has experienced severe haze and visibility degradation problems in recent years because of rapid urbanization and industrialization. In this study, daily atmospheric fine-aerosol samples were concurrently collected at three sites over the Pearl River Delta (PRD) region during 1–29 October 2014. PM_2.5 samples were analyzed for organic carbon and elemental carbon using a thermal/optical carbon analyzer. Major water-soluble inorganic ions including F⁻, Cl⁻, NO₃⁻, SO₄²⁻, Na⁺, NH₄⁺, K⁺, Mg²⁺, and Ca²⁺ were analyzed by ion chromatography. The results show that the temporal variations of PM_2.5 concentration at the three sites were highly parallel, with particle pollution events simultaneously observed during 13–19 October (EP1) and 23–27 October (EP2), suggesting that pollution events in the PRD region are usually regional. This can most likely be attributed to the significant influences of synoptic conditions, which regionally facilitate or block diffusion of air pollutants. The chemical compositions of PM_2.5 at the three sites were also found to be similar, dominated by organics and sulfates. The results indicate that accumulation of traffic emissions seems to play important roles in particle pollution for the PRD region, leading in this case to elevated nitrate contributions during both EP1 and EP2 at the three sites. Moreover, the authors found that locally emitted aerosols from biomass burning only markedly influenced the air condition at one site, Nanhai, during EP1, while regionally transported biomass burning aerosols from eastern and northern Guangdong Province influenced all three sampling sites when the PRD was dominated by polluted air from these directions during EP2.

Graphical abstract

摘要

为研究珠三角地区大气霾污染特征和形成机制, 于2014年秋季在区域内三个典型观测站同步开展了细颗粒物外场观测。结果表明, 三个站点大气细颗粒物及其化学组分质量浓度的时间变化趋势高度一致, 呈现出区域性特征。结合气象因素分析, 发现珠三角区域霾污染的形成受到中尺度的静态天气形势的影响。随着霾污染过程的发展, 细颗粒物中硝酸盐的比例显著增加, 移动源的贡献较大。结合后向气流轨迹和卫星火点分布, 证实区域内的生物质燃烧会加剧大气霾污染的强度。为进一步改善珠三角的空气质量, 建议在区域尺度上实施联防联控的减排方案。

KEYWORDS:

• HAZE
• chemical components
• nitrate
• biomass burning
• pearl river delta region

关键词:

• 霾污染
• 颗粒物化学组分
• 硝酸盐
• 生物质燃烧
• 珠三角

Disclosure Statement

No potential conflict of interest was reported by the authors.

Supplementary Material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the National Key Research and Development Program of China [grant numbers 2017YFC0210104 and 2016YFC0203305], the National Natural Science Foundation of China [grant numbers 41875152, 41530641, and 41630422], the Special Fund Project for Science and Technology Innovation Strategy of Guangdong Province [Grant No.2019B121205004], and the Fundamental Research Funds for the Central Universities [grant number 19lgpy26].