资源环境科技发展态势分析平台

Nine size-fractionated particles (<0.4–10 μm) were collected by an Andersen sampler at Shijiazhuang (North China) during four sampling periods to ascertain the size distributions of carbonaceous species (OC and EC) and water-soluble inorganic ions (WSIIs, including Na⁺, NH₄⁺, K⁺, Mg²⁺, Ca²⁺, F⁻, Cl⁻, SO₄²⁻, and NO₃⁻), and furthermore to explore the contribution of secondary components to particulate matter (PM). The carbonaceous species and WSIIs concentrations exhibit a similar temporal pattern with the decreasing order of January, October, May, and August. The WSIIs and carbonaceous species in PM₁₀ on average account for about 31.3% and 35.2% of the total mass of PM₁₀, respectively. The secondary WSIIs (i.e., NH₄⁺, SO₄²⁻, and NO₃⁻) constitute about 69.7–87.5% of the total ions for all PM₁₀ samples, and they all display a uni-modal pattern during the four study periods with the peak around 0.7–2.1 μm. Acid-base analysis shows that most of fine particles (PM_2.1) were acidic while coarse particles (PM_2.1–10) were alkaline. The average OC concentrations in PM_2.1 and PM₁₀ were 49.1 and 71.4 μg m⁻³, while the average EC concentrations in PM_2.1 and PM₁₀ were 5.6 and 8.9 μg m⁻³. This indicates that OC was the dominant carbonaceous fractions. Additionally, the OC and EC concentrations in PM₁₀ were 3.5–6.0 and 2.5–3.5 times higher during January than during other three periods. Similarly, SOC concentrations in PM₁₀ were 5–10 times higher in January compared with the other periods. The elevated OC concentration (173.9 ± 33.4 μg m⁻³) as well as OC/EC (10.0) and SOC/POC (2.8) ratios in January reveal a large amount of particles came from secondary generation. It is quite crucial to cut the emissions of precursors to alleviate particle pollution in Shijiazhuang region (especially in cold seasons) based on the facts that nearly half of components in PM₁₀ come from secondary generation.