Extensive forest fires occurred during late July 2014 across the forested region of Siberia, Russia. Smoke plumes emitted from Siberian forest fires underwent long-range transport over Mongolia and northeast China to the Korean Peninsula, which is located ∼ 3000 km south of the Siberian forest. A notably high aerosol optical depth of ∼ 4 was observed at a wavelength of 500 nm near the source of the Siberian forest fires. Smoke plumes reached 3–5 km in height near the source and fell below 2 km over the Korean Peninsula. Elevated concentrations of levoglucosan were observed (119.7 ± 6.0 ng m⁻³), which were ∼ 4.5 times higher than those observed during non-event periods in July 2014. During the middle of July 2014, a haze episode occurred that was primarily caused by the long-range transport of emission plumes originating from urban and industrial complexes in East China. Sharp increases in SO₄²⁻ concentrations (23.1 ± 2.1 µg m⁻³) were observed during this episode. The haze caused by the long-range transport of Siberian forest fire emissions was clearly identified by relatively high organic carbon (OC) ∕ elemental carbon (EC) ratios (7.18 ± 0.2) and OC ∕ SO₄²⁻ ratios (1.31 ± 0.07) compared with those of the Chinese haze episode (OC ∕ EC ratio: 2.4 ± 0.4; OC ∕ SO₄²⁻ ratio: 0.21 ± 0.05). Remote measurement techniques and chemical analyses of the haze plumes clearly show that the haze episode that occurred during late July 2014 was caused mainly by the long-range transport of smoke plumes emitted from Siberian forest fires.

We investigate regional sources contributing to CO during the Korea United States Air Quality (KORUS‐AQ) campaign conducted over Korea (1 May to 10 June 2016) using 17 tagged CO simulations from the Community Atmosphere Model with chemistry (CAM‐chem). The simulations use three spatial resolutions, three anthropogenic emission inventories, two meteorological fields, and nine emission scenarios. These simulations are evaluated against measurements from the DC‐8 aircraft and Measurements Of Pollution In The Troposphere (MOPITT). Results show that simulations using bottom‐up emissions are consistently lower (bias: −34 to −39%) and poorer performing (Taylor skill: 0.38–0.61) than simulations using alternative anthropogenic emissions (bias: −6 to −33%; Taylor skill: 0.48–0.86), particularly for enhanced Asian CO and volatile organic compound (VOC) emission scenarios, suggesting underestimation in modeled CO background and emissions in the region. The ranges of source contributions to modeled CO along DC‐8 aircraft from Korea and southern (90°E to 123°E, 20°N to 29°N), middle (90°E to 123°E, 29°N to 38.5°N), and northern (90°E to 131.5°E, 38.5°N to 45°N) East Asia (EA) are 6–13%, ~5%, 16–28%, and 9–18%, respectively. CO emissions from middle and northern EA can reach Korea via transport within the boundary layer, whereas those from southern EA are transported to Korea mainly through the free troposphere. Emission contributions from middle EA dominate during continental outflow events (29–51%), while Korean emissions play an overall more important role for ground sites (up to 25–49%) and plumes within the boundary layer (up to 25–44%) in Korea. Finally, comparisons with four other source contribution approaches (FLEXPART 9.1 back trajectory calculations driven by Weather Research and Forecasting (WRF) WRF inert tracer, China signature VOCs, and CO to CO₂ enhancement ratios) show general consistency with CAM‐chem.

The impact of biomass burning (BB) on atmospheric particulate matter of <2.5 µm diameter (PM_2.5) at Ulaanbaatar, Mongolia, was investigated using an optimized tracer-based approach during winter and spring 2017. Integrated 24 h PM_2.5 samples were collected on quartz-fiber filters using a 30 L min⁻¹ air sampler at an urban site in Ulaanbaatar. The aerosol samples were analyzed for organic carbon (OC) and elemental carbon (EC), anhydrosugars (levoglucosan, mannosan, and galactosan), and water-soluble ions. OC was found to be the predominant species, contributing 64 % and 56 % to the quantified aerosol components in PM_2.5 in winter and spring, respectively. BB was identified as a major source of PM_2.5, followed by dust and secondary aerosols. Levoglucosan ∕ mannosan and levoglucosan ∕ K⁺ ratios indicate that BB in Ulaanbaatar mainly originated from the burning of softwood. Because of the large uncertainty associated with the quantitative estimation of OC emitted from BB (OC_BB), a novel approach was developed to optimize the OC ∕ levoglucosan ratio for estimating OC_BB. The optimum OC ∕ levoglucosan ratio in Ulaanbaatar was obtained by regression analysis between OC_non-BB (OC_total–OC_BB) and levoglucosan concentrations that gives the lowest coefficient of determination (R²) and slope. The optimum OC ∕ levoglucosan ratio was found to be 27.6 and 18.0 for winter and spring, respectively, and these values were applied in quantifying OC_BB. It was found that 68 % and 63 % of the OC were emitted from BB during winter and spring, respectively. This novel approach can also be applied by other researchers to quantify OC_BB using their own chemical measurements. In addition to OC_BB, sources of OC_non-BB were also investigated through multivariate correlation analysis. It was found that OC_non-BB originated mainly from coal burning, vehicles, and vegetative emissions.

An intensive field campaign was conducted on Deokjeok Island off the west coast of the Korean Peninsula during spring 2009 to characterize the optical and hygroscopic properties of Asian continental outflows. A slightly high wavelength dependence of light absorption coefficient, α of 1.6 ± 0.05 (average ± 1· standard deviation), and a low humidity‐dependent light scattering enhancement factor at 80% relative humidity, f(80%) (2.0 ± 0.2), were obtained when air masses originated from the northern part of China (N China), compared to those obtained when air masses originated from the eastern part of China (E China) (α = 1.4 ± 0.1; f(80%) = 2.4 ± 0.2). The relatively high α and low f(80%) during the N China compared to those during the E China were consistent with a relatively high mass ratio of organic aerosol to sum of SO₄²⁻, NO₃⁻, and NH₄⁺ during the N China (1.01 ± 0.17) compared to the E China episode (0.25 ± 0.13). This result indicates the importance of organic aerosol on aerosol optical and hygroscopic properties of haze plumes. Single scattering albedo (SSA) of dry particulate matter with a diameter less than or equal to 2.5 µm (PM_2.5) (0.92 ± 0.01) and mass scattering efficiency (MSE) of dry PM_2.5 at 550 nm wavelength during the E China episode (3.6 ± 0.3 m² g⁻¹) were higher than those previously obtained at the air mass source regions in China (SSA = ~0.8; MSE = ~3.0 m² g⁻¹), implying that optical properties of PM_2.5 were significantly altered during long‐range atmospheric transport.

Long-range transported (LRT) haze can affect the regional radiation budget and the air quality in areas downwind of the Asian continental outflow. Because in situ observations of spectral aerosol optical properties of the LRT haze are rare, an intensive characterization of aerosol optical properties is needed. This study characterized the spectral optical properties of the LRT haze and Asian dust originating from the Asian continent. Integrated chemical and optical measurements of aerosol particles were carried out in a downwind area of the Asian continental outflow (Daejeon, South Korea) during winter 2014. High concentrations of PM₁₀ (particulate matter with a diameter ≤ 10 µm) and light scattering coefficients at 550 nm, σ_s, 550, were observed during a long-range transport (LRT) haze episode (PM₁₀ = 163.9 ± 25.0 µg m⁻³; σ_s, 550 = 503.4 ± 60.5 Mm⁻¹) and Asian dust episode (PM₁₀ = 211.3 ± 57.5 µg m⁻³; σ_s, 550 = 560.9 ± 151 Mm⁻¹). During the LRT haze episode, no significant change in the relative contribution of PM_2. 5 (particulate matter with a diameter ≤ 2.5 µm) chemical components was observed as particles accumulated under stagnant atmospheric conditions (13–17 January 2014), suggesting that the increase in PM_2. 5 mass concentration was caused mainly by the accumulation of LRT pollutants. On the other hand, a gradual decrease in Ångström exponent (Å) and a gradual increase in single scattering albedo (ω) and mass scattering efficiency (MSE) were observed during the stagnant period, possibly due to an increase in particle size. These results imply that a change in particle size rather than chemical composition during the stagnant period is the dominant factor affecting the aerosol optical properties. During the Asian dust episode, a low PM_2. 5 ∕ PM₁₀ ratio and Å(450∕700) were observed with average values of 0.59 ± 0.06 and 1.08 ± 0.14, respectively, which were higher than those during the LRT haze episode (0.75 ± 0.06 and 1.39 ± 0.05, respectively), indicating that PM_2. 5 ∕ PM₁₀ mass ratios and Å(450∕700) can be used as tracers to distinguish aged LRT haze and Asian dust under the Asian continental outflow.

Precise measurement of particulate matter (PM) on skin is important for managing and preventing PM-related skin diseases. This study aims to directly visualize the deposition and penetration of PM into human skin using a multimodal nonlinear optical (MNLO) imaging system. We successfully obtained PM particle signals by merging two different sources, C–C vibrational frequency and autofluorescence, while simultaneously visualizing the anatomical features of the skin via keratin, collagen, and elastin. As a result, we found morphologically dependent PM deposition, as well as increased deposition following disruption of the skin barrier via tape-stripping. Furthermore, PM penetrated more and deeper into the skin with an increase in the number of tape-strippings, causing a significant increase in the secretion of pro-inflammatory cytokines. Our results suggest that MNLO imaging could be a useful technique for visualizing and quantifying the spatial distribution of PM in ex vivo human skin tissues.