ANNUAL AIR QUALITY REPORT 

2002

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.

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

A map showing the pH of rainwater is shown in Figure 2. Generally the western and southern states of Peninsular Malaysia receive rainfall with higher acidity while the other parts of peninsula receive rainfall with pH between 4.4 and 5.2. 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 maps, it was noted that generally the rainfall from the west coast of Peninsular Malaysia is more acidic then that from the east coast of Peninsular Malaysia and rainwater acidity was higher during the months from March to October. During these months, the northwestern part of Peninsular Malaysia received rainfall of pH between 4.4 - 4.8 while the central part and southern part received rainfall of pH less than 4.4. In East Malaysia rainfall of 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 micrometres or less are called PM10 particulates and are usually of much greater health concern. 

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. The TSP concentrations at most of the stations are close to the long-term average values except in Alor Setar, Kuala Trengganu, Perai, Senai and Bintulu where the levels are slightly higher in 2002.

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. All the stations recorded PM-10 levels which are close to the longterm average.

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. Direct sun measurements are presented here in Figure 6. The measured amount of total column ozone varied between 239 to 282 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 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 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 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 pH

FIGURE 3  : Monthly Distribution pH for 2002

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