The air quality of Palangka Raya, Central Kalimantan, Indonesia: The impacts of forest fires on visibility.

Airborne particles in urban Palangka Raya, Kalimantan from Oct 2011 until Oct 2020 have been collected and analyzed for PM_2.5, PM₁₀, and Black Carbon (BC) concentrations. Palangka Raya is a city that serves the capital of the Central Kalimantan province on the island of Borneo. Kalimantan is affected by peat fires that occur periodically. There were identified increases in PM_2.5 and PM₁₀ concentrations during El Niño periods. During the forest fire episode in September - October 2015, PM_2.5 and PM₁₀ concentrations increased significantly, to nearly 400 µg/m³ and 800 µg/m³, respectively, and visibility in the city was reduced to &lt; 0.2 miles. The highest BC concentrations were observed during this massive forest fires episode. The regression analyses for PM_2.5, PM₁₀ and visibility in Palangka Raya during the period of 2011-2020, showed a non-linear correlation with reduction in visibility due to increased PM_2.5 and PM₁₀. There was no correlation for BC with visibility. Air quality in Palangka Raya was at a relatively good level with concentrations below the national ambient air quality standard when there were no forest fires event. Emissions from forest fires caused a substantial reduction in air quality reaching concentrations well above ambient air quality standards and are likely to have caused adverse health effects on the people living in the area.<i>Implications</i>: Indonesia has repeatedly experienced forest fires, especially on Kalimantan and Sumatera Islands, which burned large areas of peatland. The forest fires leading to increasing PM concentrations especially in the PM_2.5 size range which influence visibility. The seasonal variations of BC in Palangka Raya and the relationships of fine particulates with visibility were assessed. The results of regression analyses for PM_2.5 and PM₁₀ to visibility during the period of 2011-2020 showed non-linear relationships. An increasing of PM_2.5 and PM₁₀ concentrations during El Nino periods were detected well above the ambient air quality standard. To ensure effective and continued handling and prevention of forest and peatland fires, the government set up a special task force and review on several rules, including laws and government regulations as well as governor regulations that permit the burning of forest and peatland areas. These results are expected to be used to formulate more effective mitigations in reducing forest fires events in Indonesia.