Chemical Properties of the Southeast Asian Haze from Indonesian Peatland Fires

Abstract

Anthropogenic activities such as forest degradation; the expansion of commodity crops, including oil palm; and drainage of fire-prone peatlands have resulted in extensive peatland and forest fires in Indonesia. Uncontrollable and intense peatland fires have frequently occurred in the Indonesian islands of Sumatra and Kalimantan, particularly during the hot and dry seasons of the El Niño-Southern Oscillation. Air pollution in the form of transboundary haze is an urgent issue in Southeast Asia. The physical and chemical properties of the aerosols from peatland fires are fundamental to know when assessing their impact on human health and the environment, conducting source apportionment of haze events, and unraveling their dynamic state in the environment (e.g., secondary aerosol formation). In this paper, we conduct a holistic review of source profiles, key indicators of Indonesian peatland fires at source and receptor sites, and transformation of haze during its long-range transport (aging, secondary aerosol formation) as well as source apportionment in Southeast Asia, using a comprehensive chemical component dataset. Knowledge of the chemical characteristics of particulate matter at Indonesian peatland fire sources and receptor sites is still limited, especially regarding controlling factors (e.g., combustion conditions, peat composition and the effects of vegetative burning on peatland) that determine the Indonesian peatland fire source profile of particulate matter. Additionally, the process of secondary organic aerosol formation derived from Indonesian peatland fires during transport to receptor sites remains largely unresolved.