Asia Center for Air Pollution Research (ACAP)

Study on air pollution at Niigata-Maki National Acid Deposition Monitoring Station (2000-)

• In addition to the regular monitoring of wet and dry deposition, source analysis of PM_2.5 is conducted including PM_2.5 sampling, components analysis, and receptor model analysis with trainees from EANET participating countries.

Chemical Characteristics and Source Apportionment of PM_2.5 and Long-range Transport from Northeast Asia Continent to Niigata

During the four seasons from May 2015 to February 2017, seasonal intensive sampling was conducted for two weeks at the Niigata-Maki National Acid Deposition Monitoring Station.

Daily mean concentrations of PM_2.5 ranged from 4.2 µg m^-3 to 33.4 µg m^-3 during the observation period, which was lower than Japanese Air Quality Standard for PM_2.5 (35 µg m^-3). The higher concentrations of SO₄^2-, NH₄ ⁺ and organic carbon (OC) were observed in spring and summer, which may result from the photochemical activity and secondary OC production.

The major chemical components of PM_2.5 were SO₄^2-, NO₃^-, NH₄ ⁺, OC, elemental carbon (EC) and crustal elements. Compared with data at other urban sites, a lower concentration of EC and NO₃^- and higher OC/EC ratio were observed at the Niigata-Maki site, which may result from the lower anthropogenic origin such as stationary source or vehicular traffic and showed a character of the rural site.

PM_2.5 source apportionment was characterized by positive matrix factorization (PMF) analysis, and the results inferred four major sources: sea salt (10.2%), biomass combustion (18.9%), soil dust (13.2%) and secondary aerosol (44.4%). The potential source contribution function (PSCF) analysis suggested that the major sources of secondary aerosol and sea salts were domestic in southwest Japan and the Sea of Japan, whereas the sources of biomass combustion and soil dust in specific seasons were transported long distance from the Northeast Asian continent (NEA).

Comparing with previous studies in western Japan, this study showed a large domestic contribution of southwest Japan for secondary aerosol, while a larger contribution of the NEA was observed in the previous studies. The significant contribution of biomass combustion from northeast China in autumn, and local area in Niigata and southwest Japan in the other seasons were uniquely observed in this study.

This work was partly supported by JSPS KAKENHI Grant Number 25502005 and Environment Research and Technology Development Fund (5-1306) of the Ministry of the Environment, Japan.

The paper on this study is as follows:

• Li et al. 2018. Chemical Characteristics and Source Apportionment of PM_2.5 and Long-range Transport from Northeast Asia Continent to Niigata in Eastern Japan.
  Aerosol and Air Quality Research, 18: 938–956.
  http://www.aaqr.org/files/article/6596/9_AAQR-17-05-OA-0181_938-956.pdf