Global_Environmental_Research_Vol.27No.1
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Our dataset is based on a literature search and review to identify and extract relevant articles from scientific databases under appropriate inclusion and exclusion criteria. We aimed to find comprehensive chemical properties of IPF-derived PM (haze) at source and receptor sites in SEA with size distributions as well as laboratory-generated PM from burning of Indonesian or Malaysian peats. Hence, studies were included when they were in peer-reviewed publications, written in English with a full text article available, and 1) included mass concentration or mass fraction of chemical species in PM (all available species, carbonaceous components, water- soluble ions, elements, organic compounds, isotopes, aerosol mass spectra, etc.) with the PM samples having been collected during a haze period or at (near) fire sources in SEA, 2) included mass concentration, emission factor (below, “EF”), or emission ratio of generated PM species the contribution of IPFs or biomass burning to PM using samples collected during haze periods in SEA. Studies were excluded when they 1) focused on a specific purpose (e.g., optical properties, simulation models) and included no observed chemical properties, or 2) were review articles, book chapters, or reports, except for one pioneering US-EPA report5. 2. Methods investigating the chemical properties of haze, and 4) The extent to which smoke haze degrades the air quality in SEA (the potential of peatland fires to contribute to and elevate ambient PM concentrations). Therefore, we conducted a holistic review of source profiles, key indicators of IPFs at source and receptor sites, and transformation of haze during its long-range transport (aging, secondary aerosol formation) as well as source apportionment in SEA, using a comprehensive chemical component dataset. Fig. 1 Schematic representation of the cause-effect chains of environmental problems associated with Indonesian peatland fires according to a DPSIR framework. Emphasis is placed on aerosols from the fires in the “state” element of the framework. (Revised from Fig. 1 in Fujii and Tohno104) Van et al.116 discussed the definition of haze from these fires and proposed to use PM2.5 > 50 μg m-3, visibility < 5 km and relative humidity (RH) < 90% as criteria for a “haze day,” but we used whatever definition of haze each respective article on field studies used as it was. The origin of the haze in each article was confined to IPFs using air mass backward trajectory analysis, meteorological factors and other factors. That meant clear differences in total PM mass concentration or visibility, etc. were found between haze events from IPFs and non-haze periods in each field study. Firstly, we created a detailed dataset of as many chemical compositions as possible and size distributions of the haze as well as possible indicators of peatland fires by collecting and reviewing the data from field and laboratory studies. Contained therein is also the contribution of IPFs or biomass burning to PM concentrations (annual or long-term average) in SEA. Our dataset creation methods and review process are described in the next section. Our dataset enables a subsequent holistic review of the chemical compositions of haze from IPFs in SEA. Chemical Properties of the Southeast Asian Haze from Indonesian Peatland Fires Article identification and selection were conducted using three databases, Web of Science, Scopus and ScienceDirect, searching for publications that included the queries in Table S2. The time range was from 1990 to 31 laboratory studies, or 3) presented in 39

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