Chemical Characteristics of Atmospheric PM₁₀ and PM_2.5 at a Rural Site of Lijiang City, China

• Main Authors: Yu Liu, Xurui Li, Wan Wang, Baohui Yin, Yuanguan Gao, Xiaoyang Yang
• Format: Article
• Language: English
• Published: MDPI AG 2020-12-01
• Series: International Journal of Environmental Research and Public Health
• Subjects: PM₁₀ and PM_2.5; chemical components; PAHs and NPAHs; biomass burning; long range transport
• Online Access: https://www.mdpi.com/1660-4601/17/24/9553

Emissions from biomass burning are very serious in Southeast Asia and South Asia in April. In order to explore the effect of long-range transport of biomass emissions from the Indochina Peninsula in Southwest China during the period of the southeast monsoon season and to find out the main pollution sources in local atmospheric PM_2.5, a field campaign was conducted from 6–26 April 2011 in Lijiang, China. Twenty-four-hour PM₁₀ and PM_2.5 filter samples were collected, and inorganic ions, elements, and carbonaceous components (including organic carbon (OC) and elemental carbon (EC), polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs (NPAHs)) were measured. The monthly mean mass concentrations of particulate matter (PM) were 40.4 and 14.4 μg/m³ for PM₁₀ and PM_2.5, respectively. The monthly mean concentrations of OC and EC in PM₁₀ were 6.2 and 1.6 μg/m³, respectively. The weekly mean concentrations of ∑PAHs and ∑NPAHs were 11.9 ng/m³ and 289 pg/m³, respectively, in atmospheric PM₁₀ of Lijiang. The diagnostic ratios of PAH and NPAH isomers were used to analyze the sources of PAHs and NPAHs in PM₁₀. The ratios of Benz(a)anthracene/(Chrysene+Benz(a)anthracen), Fluoranthene/(Fluoranthene+Pyrene) and Indeno(1,2,3-cd)pyrene/(Benzo(g,h,i)perylene+Indeno(1,2,3-cd)pyrene) were 0.45 ± 0.04, 0.61 ± 0.01, and 0.53 ± 0.03, respectively, indicating the contribution from coal combustion and biomass burning. The 1-nitropyrene/Pyrene (1-NP/Pyr) ratio was 0.004 ± 0.001, suggesting that the contribution to NPAHs mainly came from coal combustion. Sulfate was the most prominent inorganic ionic species, with monthly mean levels of 2.28 and 1.39 μg/m³ in PM₁₀ and PM_2.5, respectively. The monthly mean mass ratios of NO₃⁻/SO₄²⁻ were 0.40 and 0.23 in PM₁₀ and PM_2.5, respectively, indicating that the contribution of atmospheric anions from coal combustion sources was much more important than that from other sources. Based on the relatively high SO₄²⁻ concentrations and low NO₃⁻/SO₄²⁻ ratios, combined with the data analysis of isomer ratios of PAHs and NPAHs, we can conclude that coal combustion, traffic, and dust were the major contributors to local atmospheric PM in Lijiang city, while biomass burning may also have contributed to local atmospheric PM in Lijiang city to some degree.