Relationships between Visibility and Selected Air Pollutants in the Klang Valley

Abstract

Hazy conditions over the Klang Valley which last appeared in October 1991, began to reappear in August 1994. This study which was conducted during the beginning period of the haze episode, represents a preliminary attempt to identify the types of air pollutants that may be most associated with visibility reduction. Visibility and rainfall data were obtained from the Subang Airport Meteorological Station. The levels of selected air pollutants which include respirable particulates (PMIO), nitrogen oxide, nitrogen dioxide, sulfur dioxide, carbon monoxide and ozone were measured from a station located at Dewan Bandaraya Kuala Lumpur. Data for visibility, rainfall and air pollutants were collected from August 1 to September 4, 1994, giving a total of 35 24-hour sampling days. On 2 of the 4 days with poor visibility, the Recommended Malaysian Air Quality Guidelines for PM10 nitrogen dioxide and sulfur dioxide were exceeded. Pearson correlation analysis showed statistically significant inverse correlations between visibility and PM10, nitrogen oxide, nitrogen dioxide and carbon monoxide, indicating pollutants from motor vehicles and other local combustion sources as important contributors to visibility reduction. A statistically significant inverse correlation between visibility and rainfall also indicates the ineffectiveness of light rain in dispersing the haze. This study concludes that visibility in the Klang Valley may be worsening over the years; that local air pollution sources may play a much more important role in visibility reduction and the haze problem, than what might be realised; and that atmospheric PM10 may reach unhealthy levels at times. Comparison with other studies strongly support these conclusions.

ABSTRAK

Keadaan berjerebu di Lembah Klang yang kali akhirnya berlaku pada Oktober 1991, mula muncul kembali pada Ogos 1994. Kajian ini yang dilakukan semasa permulaan episod jerebu tersebut, merupakan usaha awal untuk mengenal pasti jenis pencemar udara yang paling berhubungan dengan pengurangan visibiliti. Data visibiliti dan hujan telah diperolehi daripada Stesen Kajicuaca Lapangan Terbang Subang. Aras pencemar udara tertentu yang termasuk habuk ternafas (PM10), nitrogen oksida, nitrogen dioksida, sulfur dioksida, karbon monoksida dan ozon telah diukur dari sebuah stesen yang terletak di Dewan Bandaraya Kuala Lumpur. Data visibiliti, hujan dan pencemar udara telah dikumpul dari 1 Ogos hingga 4 September 1994, berjumlah 35 hari pensampelan selama 24 jam. Pada 2 dari 4 hari yang mempunyai visibiliti yang buruk, Panduan Kualiti Udara Malaysia untuk PM10, nitrogen dioksida dan sulfur dioksida telah dilampaui. Analisis Korelasi Pearson menunjukkan korelasi songsang yang bererti secara statistik antara visibiliti dengan PM10, nitrogen oksida, nitrogen dioksida dan karbon monoksida. Ini menunjukan pencemar daripada kenderaan bermotor serta punca pembakaran tempatan yang lain sebagai penyumbang penting kepada pengurangan visibiliti. Korelasi songsang yang bererti secara statistik di antara visibiliti dengan hujan juga menunjukkan ketidakkeberkesanan hujan renyai dalam dispersi jerebu. Kajian ini mengambil kesimpulan bahawa visibiliti di Lembah Klang mungkin semakin merosot dari tahun ke tahun; bahawa punca pencemaran udara tempatan mungkin memainkan peranan yang lebih penting dalam pengurangan visibiliti dan masalah jerebu, daripada apa yang dijangkakan; dan PM10 di atmosfera boleh mencapai aras yang tidak sihat pada ketika tertentu. Perbandingan dengan kajian-kajian lain mengukuhkan kesimpulan ini.