Rapid economical growth in East Asia causes consumption of vast amount of fossil fuel for energy source, which is estranged from a harmonized development with the environment. Emission of green house gases such as CO2, acidic gases such as NOx and SO2, as well as particulate matter affects the environment of the source country, surrounding countries, and moreover, whole northern hemisphere. Not only regional but global scale atmospheric environmental problems were arisen. Among these atmospheric pollutants, aerosols attract special attention these days, because there are many unclear points; for example, aerosol spatial distribution, formation mechanisms in the atmosphere, quantitative evaluation of environmental impacts, and so on. Human health, in particular, has the highest priority to be protected, so that the assessment of the impacts on human health is urgently needed. In addition, the impacts on vegetation, which is an important CO2 sink, are also a very urgent issue to be investigated from a point of view of global warming, too. Under such circumstances we proposed a research project entitled “Impacts of Aerosols in East Asia on Plants and Human Health” to the Grant-in-Aid for Scientific Research on Innovative Areas, which was newly started in 2008. Fortunately, our project was accepted by The Ministry of Education, Culture, Sports, Science and Technology (MEXT) and started in Nov. 2008. This research project consists of four Research Items. Namely, A01: Evaluation of Aerosol Formation and the Emission Sources, A02: Elucidation of Transport and Distribution of Aerosols and Air Pollutants in East Asia, A03: Elucidation of the Impacts of Aerosols on Plants, and A04: Elucidation of the Impacts of Aerosols on Human Health.
Research outline and progress are presented for the Research Item A01 “Evaluation of Aerosol Formation and the Emission Sources” which is one of the items in Research Area “Impacts of Aerosols in East Asia on Plants and Human Health” supported by the Grand-in-Aid for Scientific Research on Innovative Areas, MEXT. A01 focuses on the emission characteristics of aerosols and the precursors, reactions of the precursors relevant to subsequent aerosol formation and the formation mechanism of secondary particles. In addition, we aim at creating an innovative scientific area with new research development by mutual sharing of the findings of each research group, reflection of the achievements of other research items, and adoption of a socio-economic perspective to evaluate the emission sources. The main concerns are (i) evaluation of emission characteristics of aerosols and their precursors (both anthropogenic and of plant origin) in Asian regions and (ii) elucidation of the reaction mechanism of the precursors and formation process of secondary particles in various ambient environments. Furthermore, (iii) evaluation of indirectly induced environmental burden or impact potential in other countries as well as one’s own in accordance with the economic activity of the industrial sector in each country will be performed by combining quantified source-receptor relationships and input-output analysis.
In East Asia, various kinds of aerosols emitted from anthropogenic and natural sources such as sulfate, nitrate, black carbon, organic carbon and mineral dust, coexist as a mixture. In order to clarify the effects of aerosols on plants and human health, it is indispensable to understand the characteristics of aerosols and their distribution and movement in a regional scale. In this study (Research Item A02), three different approaches are taken in the three research groups (P05, P06, and P07). P05 employs the lidar network and ground-based measurement networks including the measurement in mountain regions to study the distribution and movement of aerosols in various spatial and temporal scales. In P06, the chemical and physical characteristics of aerosols are observed at the ground stations. In P07, observations using an aircraft are performed. In A02, proposed researches are also conducted on the behavior of specific pollutants, namely polycyclic aromatic hydrocarbons (PAHs) (K04), nitrogen oxides (K05), and black carbon (K07), and on satellite remote sensing (K06)
The research project of “Impacts of Aerosols in East Asia on Plants and Human Health” supported by the Grant-in-Aid for Scientific Research on Innovation Areas is in progress in 2008-2012 (fiscal year). This research project consists of four research items, A01: Evaluation of aerosol formation and the emission sources, A02: Elucidation of transport and distribution of aerosols and air pollutants in East Asia, A03: Elucidation of the impacts of aerosols on plants, and A04: Elucidation of the impacts of aerosols on human health. The objective of research item A03 is to clarify the effects of aerosol such as black carbon on plants. In the research item A03, experimental studies and field surveys in Japan and other Asian countries on possible impacts of aerosols on plants are being conducted. This feature article introduces ongoing experimental and field studies on the effects of aerosol on forest tree species.
We formed health impact study group which consists of toxicological study, epidemiological study, Japanese cedar pollen study and 3 Asian dust epidemiological studies. Based on the knowledge from A01 and A02 groups, which studied generation and transformation of transboundary aerosols, we selected possible hazardous components of particulates. Toxicological study evaluated the effect of these candidates on cells and animals, and using the result of toxicological study, epidemiological study evaluates the effect of transboudary pollution on humans. With the novel and better exposure measurement of Asian dust from A02 group, the three studies evaluate effects of Asian dust. Eventually, these studies would validly evaluate the health effect of transboundary air pollution. Pollen study investigates the alteration of the pollen and its interaction with air pollutants, and found that the allergen protein inside the pollen may be exposed to air pollutants that include Asian dust by pollen rupture; the exposure may affect the allergic response.
In a corona-discharge field, airborne condensable organic compounds are often decomposed to smaller molecules and generate fragment ions and particles. In order to study the influence of fragmentation on the adsorption of condensable organic compounds, two types of experiments were performed. Through the measurement of abundance ratios of various airborne molecular contaminants at various drift voltages, it was found that the abundance ratio of TCEP was decreased at a high voltage while that of smaller molecules was increased. A chamber test was performed with exposing a semiconductor wafer downstream of corona-discharge type ionizer in unidirectional airflow that contains TCEP vapor. When the voltage between ionizer's electrode and the wafer exceeded 10kVs, the adsorption of TCEP was markedly decreased. The reason was that the fragment ions of TCEP generated at a high voltage are responsible for transferring the electric charge in place of TCEP ions. The adsorption of TCEP onto wafer was also simulated by applying Langmuir-type adsorption model. The simulation result well expressed the experimental data when the influence of fragment ions was included.
Volume fraction (ε) of water-soluble material in atmospheric aerosol particles is an important parameter related to hygroscopicity and activation processes to cloud particles. In order to estimate ε of individual coarse dust particles, a confocal scanning laser microscope was applied to direct measurement of volume difference of individual particles before and after water-dialysis using Nuclepore filters (nominal pore size: 0.05 µm) as a collection substrate of an aerosol impaction sampler. Individual particles of Arizona Test Dust (ATD) and reference Asian dusts (CJ-1 and CJ-2) were analyzed for , and their results were combined into 3 size ranges (2-3.4, 3.5-8.4, and 8.5-30 µm) and 2 size ranges (2-3.4 and 3.5-10 µm), respectively. These test dust particles showed various ε ranging from 18% (ATD) to 41% (CJ-1) on the average. More than 50% of the analyzed test dusts particles contained soluble fraction (ε>10%), except the ATD particles of size range 2-3.4 µm which are dominated by particles with insoluble components.