ANNUAL AIR QUALITY REPORT 

2004

1. Introduction

The Malaysian Meteorological Service Air Pollution Monitoring Network comprises a total of 22 stations well distributed over Peninsular Malaysia and Sabah and Sarawak. This network was established in 1976 with only two stations, but gradually over the years the network expanded when more stations were added to it. At the same time, as the need arises, more parameters were 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 the Malaysian Meteorological Department, 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 the detection of significant changes in atmospheric concentration to provide early warnings 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 averaged 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 of the samples.

 Annual pH

Figure 2 shows the volume weighted average pH of rainwater collected during 2004. On an annual average basis, the pH of rainwater in the northern states in Peninsular Malaysia, Sabah and Sarawak is in the normal range of 4.8 to 5.2. However, rainwater in the western and southern states excluding the Klang Valley Region and South Johore during 2004 is slightly acidic with averages pH of between 4.4 and 4.8. Finally, the average pH of rainwater in the Klang Valley Region and South Johore especially in Senai area 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 pH levels are detected during the month of April to October, the Southwest Monsoon season while higher pH levels are frequent from November to March which coincides with the Northeast Monsoon season.
 

Aerosols or Total Suspended Particulates (TSP) are small airborne particulates with diameters of less than 100 micrometers (). 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 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. TSP concentrations in Bayan Lepas, Petaling Jaya and Tawau were below normal throughout the year while in Perai and Alor Setar, the concentrations were mainly above normal. The rest of the stations showed normal and slightly above normal the long-term average values with sometimes large monthly variations.

 Particulate Matter (PM-10)

PM-10 particulates were measured at 8 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. Generally, normal to above normal concentrations were measured during the beginning of the year and mainly below normal concentrations towards the end of the year.
 

4. Atmospheric Ozone

Ozone is a very reactive gas found in trace amounts 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 2004 are presented here (Figure 6). The measured amount of total column ozone varied between 234 to 288 Dobson unit (DU). There is a seasonal variation in ozone concentration with higher levels in April- May and lower levels in December. This variation is not as evident as those sites in the middle latitudes.

 Vertical Ozone Profile

Vertical ozone profile is measured twice a month 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, the ozone level increases rapidly to a maximum at about 27 km above MSL
 

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