National Environment Agency Nailing down air quality is complicated
We thank Mr Dennis Sim for his feedback (NEA needs to give useful info on haze, The Straits Times Online, Nov 17).

The air around us is a mixture of gases and particles that can come from a variety of sources, and determining the composition of the particulate matter in the air is a complex process.

When there is haze, our immediate priorities are real-time monitoring of the situation and issuance of the necessary advisories to the public. We seek to keep the public informed as much as possible, with care taken to release accurate and reliable information.

For significant episodes of air pollution, our protocol is indeed to conduct detailed laboratory analysis using representative samples taken during the affected period.

Based on post-incident lab analyses of the carbonaceous profile of the particulate matter (PM2.5) samples taken on Nov 12 and 13, the particulate matter originated predominantly from burning peat forests, which would have come from outside Singapore, with a lower contribution from local sources.

The carbonaceous profile of particulate matter comprises fractions of organic carbon and elemental carbon.

Higher fractions of organic carbon in the carbonaceous profile of particulate matter would be influenced predominantly by peat forest burning.

The build-up of particulate matter over Singapore was slow to disperse as the prevailing winds on Nov 12 and 13 were light and variable in direction. With the highly humid conditions on those days, water droplets in the air were also bound to the particulate matter, further affecting visibility.

Cheang Kok Chung
Director, Pollution Control Department
National Environment Agency


Source: https://www.straitstimes.com/forum/letters-in-print/nailing-down-air-quality-is-complicated
 

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