UAAT International Young Visiting Scholar Program
Kojiro Shimada
Assistant professor
University of the Ryukyus
Email: kshimada@cd.u-ryukyu.ac.jp
Webpage: https://helpful-ferret-k8hkq4.mystrikingly.com/
https://researchmap.jp/7000019703
Host Scholar: (Ta-Chih Hsiao, Professor)
Hosting Department/Institution: Institute of Environmental Engineering, National Taiwan University
Biography:
Research map: https://researchmap.jp/7000019703
Career
2025(March)-2025(May): Assistant Professor (Invited Professor) in National Taiwan University (University Academic Alliance in Taiwan (UAAT) international Young Visiting Scholar program)
2020(April)- present: Assistant Professor
University of the Ryukyus, Department of Chemistry, Biology, and Marine Science
2018(March)-2018(May): Assistant Professor in National Central University (Invited Professor)
2017(March)-2017(May): Assistant Professor in National Central University (Invited Professor)
2017(April)- present: Assistant Professor
Waseda University, School of Creative Science and Engineering
2016(March)-2016(May): Assistant Professor in National Central University (Invited Professor)
2014(November)-2017(March): Assistant Professor
Tokyo University of Agriculture and Technology, The Global Innovation Research Organization
2014(April)-2014(November): Research associate
Tokyo Metropolitan Research Institute for Environmental Protection
2013(April)-2014(March): Assistant Professor
Tokyo University of Agriculture and Technology, Department of Chemical Engineering
Education
2010(April)-2013(March): PhD degree in Doctor of Agriculture
Department of Symbiotic Science of Environment and Natural Resources, The United Graduate School of Agriculture, Tokyo University of Agriculture and Technology
Supervisor: Professor Shiro Hatakeyama and co-researcher Dr. Akinori Takami (National Institute for Environmental Studies).
Lecture [1]:
Time: 2025/4/8, 10:20AM
Venue: National Taiwan University, Sustainable Future Hall, Envi. Res. Building
Title: Development of a method for measuring isoprene generated by photodegradation of "plant grime"
Abstract:
BVOCs, represented by isoprene, influence the climate as precursors to secondary organic aerosols and ozone. However, conventional models show poor agreement with observed isoprene levels. The objective of this study is to elucidate the emission of BVOCs through photodegradation and improve model accuracy.
From July 25 to August 6, 2024, aerosol deposition was collected in the Yanbaru forest using a surrogate surface method with quartz filters impregnated with plant wax (simulated leaves), quartz filters, Teflon filters, and leaves of Castanopsis sieboldii. A comparison of WSOC (water-soluble organic carbon) concentrations in the deposited aerosols showed that the simulated leaves exhibited a trend similar to that of Castanopsis sieboldii leaves, with an average WSOC concentration of 184 ± 54 μg/cm². This result indicates that the presence or absence of wax affects the deposition and retention of organic matter.
Furthermore, online measurements using PTR-ToF-MS revealed the emission of isoprene and aldehydes from the simulated leaves under simulated sunlight irradiation. The maximum isoprene emission rate was 37.9 μg/m²s, exceeding the emission rate of 2.92 μg/m²s for the representative species Quercus serrata (Okumura et al., 2008), confirming a high emission rate due to photodegradation.
Lecture [2]:
Time: 2025/4/16
Venue: National Cheng Kung University, the Department of Environmental Engineering, classroom 47111
Title: Changes in aerosol acidity and its effect on SOA formation in a remote area of the Pacific Ocean
Abstract:
Atmospheric acidic particles and secondary organic aerosols (SOA) are considered contributing factors to health damage and climate change. Aerosol acidity is primarily governed by sulfuric acid (H₂SO₄) generated through the oxidation of SO₂. Numerous studies have been reported based on laboratory experiments, and the oxidation of SO₂, which is incorporated into chemical transport models such as CMAQ (Community Multiscale Air Quality model), is known to decrease in reaction rate with increasing acidity¹).
On the other hand, recent laboratory experiments have also reported oxidation processes whose reaction rates increase with acidity, such as the auto-oxidation of SO₂ by O₂ on acidic particle surfaces²). Additionally, the effect of aerosol acidity on SOA formation remains a topic of debate, particularly in laboratory-based studies³). Research on aerosol acidity changes and SOA formation has largely relied on laboratory experiments and numerical modeling, with few studies attempting to clarify these processes using multi-site observations.
Therefore, in this study, we conducted atmospheric observations at three sites: Tuoji Island in China, a source region of air pollutants, as well as Nagasaki University and Cape Hedo in Okinawa, which are downwind receptor sites. We aimed to evaluate the impact of long-range transport on aerosol acidity changes and SOA formation.
Atmospheric observations were conducted in the winters and springs of 2022 and 2023 at three sites: Tuoji Island, China (38.17°N, 120.76°E), Nagasaki University (32.79°N, 129.86°E), and CHAAMS (Cape Hedo Atmosphere and Aerosol Monitoring Station, 26.87°N, 128.25°E). Aerosols were collected using a high-volume air sampler (HV-1000F, SIBATA) equipped with a PM₂.₅ impactor, and pre-combusted quartz fiber filters (2500QAT-UP, Pall Flex) were used for sampling.
Ion composition analysis of the filters was performed using an ion chromatograph (ICS-1600, Thermo Fisher Scientific). The obtained ion concentrations were input into thermodynamic equilibrium models, E-AIM (Extended AIM Aerosol Thermodynamics Model) and ISORROPIA II, to calculate aerosol pH. Data analysis for SOA was conducted with reference to Hojo et al. (2024)⁴). The same air mass at the three sites was identified based on variations in elemental carbon (EC) concentration, PM₂.₅ concentration distribution from CMAQ version 5.2, backward trajectories calculated using HYSPLIT (Hybrid Single-Particle Lagrangian Integrated Trajectory Model), and satellite data from CALIPSO (Cloud-Aerosol Lidar with Orthogonal Polarization).
Figure 1 illustrates the relationship between acidity changes due to H₂SO₄ formation during long-range transport and the oxidation state ((OS)̅c) of humic-like substances (HULIS), which are high-molecular-weight organic compounds. The most abundant cation in all three sites was NH₄⁺. However, for anions, NO₃⁻ was the dominant species (27.7%) at Tuoji Island, whereas SO₄²⁻ was the most abundant at Nagasaki (30.9%) and CHAAMS (45.6%). As shown in Figure 1(a), aerosol pH decreased significantly during long-range transport.
This was attributed to an increase in the oxidation rate of SO₂ to H₂SO₄ with rising acidity, as illustrated in Figure 1(b). Furthermore, as shown in Figure 1(c), particles with similar (OS)̅c values exhibited a trend where higher acidity correlated with a higher O/C ratio. This suggests that in real atmospheric conditions, SOA undergoes functionalization and polymerization more extensively under acidic conditions.
(a) pH values at the three observation sites.
(b) Relationship between inferred [H⁺] (neq/m³) and the oxidation rate constant k (h⁻¹) of SO₂.
(c) Relationship between pH and the oxidation state ((OS)̅c) of humic-like substances (HULIS) in the Van Krevelen Diagram.