ANNUAL AIR QUALITY REPORT 

2001

1. Introduction

The Malaysian Meteorological Service Air Pollution Monitoring Network comprises a total of 22 stations well distributed over Peninsular Malaysia and East Malaysia. This network was started in 1976 with only two stations, but gradually over the years more stations were added. At the same time, as the need arises, more parameters have been added to the observation programme at selected stations. Most of the stations are located some distance from urban centers, thus ensuring that only ambient conditions are monitored Figure 1.

Most of these stations are co-located with climatological stations so that simultaneous and continuous observation of both meteorological and air pollution parameters are carried out. This would ensure that a comprehensive data set comprising of both air quality and meteorological data would be available for assessment of any air pollution event.

The Environmental Studies Division is responsible for monitoring and assessing the air quality of the country through the network. Data from the network is also used to document long-term trends and providing early warning of environmental disasters.

The parameters measured by the Division are:

	Rainwater Acidity
	Aerosols
	Atmospheric Ozone
	Reactive Gases

Regular and methodological measurement of rainwater chemical composition through a network of stations over a long period of time provides an indication of air quality including acidification trends in the country and identifies the areas that are currently subjected to elevated amounts of the wet component of acidic deposition. Such measurements will contribute towards the determination of wet and dry deposition fluxes of acidic species at the measurement sites which will eventually lead to a better understanding of the atmospheric acidification issues in the region.

Rain acidity is commonly reported as pH. pH is a measure of the hydrogen ion concentration in a liquid and has a scale ranging from 0 to 14. Rain from even very clean, remote sites is slightly acidic with pH varying between 5.2 to 6.0 due to the presence of dissolved natural acids; therefore rain is only considered acidic if the pH is less than 5.2. Since rainfall amount varies, all values of pH are volume weighted.

The Malaysian Meteorological Service uses either the Automatic Wet and Dry Fallout Collector or the Wet-Only Sampler to collect rainwater in its network. The rainwater samples are accumulated weekly and sent to the Department of Chemistry, Malaysia for chemical analysis of the principal anions and cations. A biocide, thymol, is used to prevent biological degradation.

Annual pH

A map showing the pH of rainwater is shown in  Figure 2. Generally the northern states of Peninsular Malaysia and East Malaysia received rainfall with pH between 4.8 and 5.2 while the other parts of the peninsula received rainfall with pH between 4.4 and 4.8. The areas that experience high levels of acidity are located in and around the Klang Valley and southern part of Johore. Coincidently these areas are rapid growth centers, heavily industrialized with high population density.

Monthly variation of pH

Individual maps of the monthly volume-weighted pH are shown in  Figure 3. From the sequence of the maps, it was noted that rainwater acidity generally was higher during the months from April to September for Peninsular Malaysia. During these months, the northern part of Peninsular Malaysia received rainfall of pH between 4.8 - 5.2, the central part between 4.4 - 4.8 while the western and southern parts received rainfall of pH less than 4.4. In East Malaysia rainfall pH was generally between 4.8 - 5.6.

Aerosols or Total Suspended Particulates (TSP) are small airborne particulates with diameters less than 100 micrometers (m). TSP with an aerodynamic diameter of 10 micrometers or less are called PM10 particulates and are usually of a much greater health concern.

Total Suspended Particulate

TSP was measured using High-Volume Air Sampler at 14 stations. The monthly trends in TSP loads for these stations are shown in  Figure 4. Bayan Lepas, Tanah Rata, Petaling Jaya, Kuala Trengganu, Kuching, Labuan and Senai showed below normal TSP levels during most of the months except Tawau which showed above normal.

Particulate Matter (PM-10)

PM-10 particulates were measured at 9 stations in the monitoring network using the High-Volume PM-10 Sampler. The monthly trends in PM-10 concentrations for these stations are shown in  Figure 5. Kluang, Petaling Jaya, Kuantan and Kota Bharu experienced below normal PM-10 levels during most of the months. The others are slightly above normal or normal PM-10 levels.

4. Atmospheric Ozone

Ozone, is very reactive gas found in very small quantities in the atmosphere. Its mean concentration can vary from a few to hundreds of parts per billion (ppb) depending on the location and altitude. At the surface layer, ozone is considered a secondary pollutant which causes oxidant episodes such as haze and smog. In the stratosphere, the layer of ozone reduces harmful ultraviolet radiation reaching the earth’s surface. On the global scale, ozone is a greenhouse gas which contributes to global warming.

Total Column Ozone

Daily total column ozone is monitored automatically in Petaling Jaya using the Brewer Spectrophotometer. Direct sun measurements are presented here  Figure 6. The measured amount of total column ozone varied between 225 to 285 Dobson unit (DU). There is seasonal variation in ozone concentration but it is not as evident as those sites in the middle latitudes.

Vertical Ozone Profile

The vertical ozone profile is measured at KLIA, Sepang using ozonesondes released at the beginning and middle of the month. The monthly mean vertical ozone profile is shown in  Figure 7. The ozone profiles show a minimum at about 15 kilometres above mean sea level (MSL) corresponding to the top of the tropical tropopause layer. Above 15 kilometres, ozone levels increased rapidly to a maximum about 27 km above MSL.

5. Reactive Gases

Currently the Malaysian Meteorological Service monitors gaseous sulphur dioxide and nitrogen dioxide at the Petaling Jaya and Tanah Rata sites using passive samplers.

Figure 8 shows the weekly concentration of SO₂ and NO₂ measured at Petaling Jaya. SO₂ values fluctuate between a range of 2.0 ppb and 9.0 ppb throughout the year with no seasonal variation. The concentrations of NO₂ are higher and fluctuate between a range of 14.5 ppb and 40.0 ppb.  

The SO₂ and NO₂ concentrations measured at Tanah Rata are shown in Figure 9. Generally, the concentrations of these gases are low, seldom exceeding 3.1 ppb.

Figures :

FIGURE 1  : Monitoring Station

FIGURE 2  : Annual pH

FIGURE 3  : Monthly Distribution pH for 2001

FIGURE 4  : TSP Trends

FIGURE 5  : PM - 10 Trends

FIGURE 6  : Total Column Ozone

FIGURE 7  : Annual Mean Ozone Profile

FIGURE 8  : SO₂ and NO₂ Concentration at Petaling Jaya

FIGURE 9  : SO₂ and NO₂ Concentrations at Tanah Rata