ANNUAL AIR QUALITY REPORT 

2003

1. Introduction

The Malaysian Meteorological Service Air Pollution Monitoring Network comprises a total of 22 stations well distributed over Peninsular Malaysia, Sabah and Sarawak. 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.

In Malaysian Meteorological Service, the Environmental Studies Division carries out monitoring of air quality over the country and assesses the data collected from the network. Data from the network is used to document long-term trends and for detection of significant changes in atmospheric concentration to provide 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. 

Rainwater 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 Services 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

Figure 2 shows the volume weighted average pH of rainwater collected during 2003. On an annual average basis, the pH of rainwater collected in the northern peninsula states, Sabah and Sarawak is in the normal range of 4.8 to 5.2. However, rainwater in the western and southern states with exception of the Klang Valley Region and South Johore during 2003 is slightly acidic with average pH between 4.4 and 4.8. The pH of rainwater in the Klang Valley Region and South Johore is below 4.4.

Monthly variation of pH 

Individual maps of the monthly volume-weighted average pH of rainwater are shown in Figure 3. Areas in the Klang Valley Region which are subjected to low pH levels of below 4.4 do not show significant monthly variations. On the other hand, the rest of Peninsular Malaysia including Sabah and Sarawak, shows monthly variations of pH. Generally, relatively lower and normal pH levels are detected during the month of April to October, the Southwest Monsoon while higher pH levels are frequent from November to March which coincide with Northeast Monsoon season.

Aerosols are Total Suspended particles (TSP) in the atmosphere with sizes ranging from submicrons to about 100 microns. PM-10 are suspended particles with sizes that are less than 10 microns and are greater concern because of their health impacts.

Total Suspended Particulate

TSP concentration was measured using the High-Volume Air Sampler at 14 stations. The monthly trends in TSP loads for these stations are shown in Figure 4. During the first half of the year, TSP concentrations at most of the stations are closed to the long-term average values except in Perai where the levels are slightly higher and during the second half especially during the beginning, TSP levels are lower than the long-term average.

Particulate Matter (PM-10)

PM-10 particulate concentration was measured at 8 stations in the monitoring network using the High-Volume PM-10 Sampler. The monthly trends in PM-10 concentrations at these stations are shown in Figure 5. The PM-10 concentrations at most of the stations are close to or slightly below to the long-term average values except in Kuantan and Petaling Jaya where the levels are below normal throughout 2003.

4. Atmospheric Ozone

Ozone, a very reactive gas is 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 by direct sun and zenith sky measurements. Direct sun measurements in 2003 are presented here (Figure 6). The measured amount of total column ozone varied between 236 to 270 Dobson unit (DU). There is seasonal variation in total column ozone 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 twice a month. The annual 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 tropical tropopause layer. Above 15 kilometres, ozone levels increased rapidly to a maximum at about 27 km above MSL. 

5. Reactive Gases

Currently the Malaysian Meteorological Service monitors gaseous sulphur dioxide (SO2) and nitrogen dioxide (NO2) concentration at the Petaling Jaya and Tanah Rata Global Atmosphere Watch Stations using passive samplers.


Figure 8 shows the weekly concentration of SO2 and NO2 measured at Petaling Jaya. SO2 values fluctuate between 1.3 ppb and 8.0 ppb throughout the year with no discernible seasonal variation. While concentrations of NO2 are higher and fluctuate between 21.0 ppb and 43.0 ppb. 

The SO2 and NO2 concentrations measured at Tanah Rata are shown in Figure 9. Generally, the concentrations of both these gases are low, below 1.5 ppb. 

Currently Malaysian Meteorological Service monitor gaseous sulphur dioxide (SO2) and nitrogen dioxide (NO2) at the Petaling Jaya and Tanah Rata sites using passive samplers. 

Figure 8 shows the weekly concentration of SO2 and NO2 measure 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 40.5 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 Average Rainwater pH

FIGURE 3  : Monthly Distribution pH for 2003

FIGURE 4  : TSP Concentration

FIGURE 5  : PM - 10 Concentration

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