The Study of Seasonal Variation of PM10 Concentration in Peninsular ...
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The Study of Seasonal Variation of PM10 Concentration in Peninsular, Sabah and Sarawak (Nur Aleesha Abdullah, Siti Hawa Shuhaimi, Toh Ying Ying, Afizal Haqeem Shapee, Maznorizan Mohamad)
ABSTRACT To assess the influence of seasonal variation on PM-10 concentration, Malaysia is categorized according to four different seasons namely, Northeast Monsoon (November-February), First Intermonsoon (March-May), Southwest Monsoon (JuneAugust) and Second Intermonsoon (September – October). The monitoring stations were chosen to represent six main regions in Malaysia, namely the Northern Region (Bayan Lepas Station), Central Region (Petaling Jaya Station), Southern Region (Senai Station), East Coast (Kuantan Station), Sabah (Kota Kinabalu Station) and Sarawak (Kuching Station) while the Tanah Rata Station is representing the background location. Tapered
Element
Oscillating
Microbalance
(TEOM)
is
used
for
real-time
measurement of PM-10 concentrations at MMD’s air pollution monitoring network where the daily 24-hour continuous air monitoring are being carried out. In this study, PM-10 and the meteorological parameter were analyzed to investigate the seasonal variation on PM-10 concentration and meteorological parameter. Statistical analyses of PM-10 data sets were carried out to investigate the seasonal trend of PM-10 concentrations in Malaysia. The result suggested that the PM-10 concentration recorded during Southwest monsoon is relatively higher as compared to the concentration value recorded during Northeast Monsoon. Keyword: Particulate matter, aerosol, total suspended particulate, TEOM.
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1.0 INTRODUCTION Malaysia is a maritime country located at lat 2˚30’ North and long 112˚ 30’ East and experienced equatorial climate. Hot and humid with relative humidity ranging from 80-90 percent, except in the highland, and the temperature averages from 20-30˚C throughout the year. The climate is governed by the regime of the northeast and southwest monsoons. During Northeast Monsoon (November-March), areas on the east side of Peninsular such as Kelantan, Terengganu and Pahang will experience heavy rainfall. As for Sabah and Sarawak, they will experience the same heavy rainfall through this period of time. The weather systems that develop in conjunction with cold air outbreaks from Siberia produce heavy rains, which often cause severe floods along the east coast states of Peninsular Malaysia [ 4]. On the other hand, during the Southwest Monsoon from May to September, Sumatras will bring significant amount of rainfall to the western side of Peninsular. The affected areas generally will be from coastal areas of Perak and down to western part of Johore. Moreover, the driest period in most districts occurring in June to August. Malaysia has experienced several haze period during this period for the past years. The haze episodes have created great interest because of its harmful health effects and social economic consequences. The most immediate effect is the reduction of visibility and bronchial related disease. The most severe haze episode was in 1997 that shrouded most part of the country, especially the Klang Valley and state of Sarawak. During haze periods, suspended particulate matter was found to be a major pollutant, while other parameters remained within standard level. The main sources of suspended particulates are forest fire from neighbouring country. Besides that, smoke from local burning also contributed to the severity of the haze. During non-haze period, most particulate sources were from vehicular emission [1]. The concentrations of suspended particulate tend to be higher with higher air temperature and stable atmosphere. Conversely, wet season has cleaning effects over the suspended particulate. Strong wind will increase the intensity of the vertical
2
and horizontal transport, thus reduce suspended particulate concentration in atmosphere [1]. An aerosol is a suspension of droplets or particles in the air and those particles with a diameter range from 10-3 to 20 µm. In meteorology, the term is often used to describe the particles suspended within the gas, such as minute fragment of seasalt, dust, organic matter, and smoke. Such aerosols enter the atmosphere by natural processes such as volcano eruption and by human activities like burning of fossil fuels. Aerosols absorb heat and may act as condensation nuclei. Particulate matter-10 (PM10) is used to describe particles with diameter of 10 micrometers or less for solid or liquid found suspended in the atmosphere. While individual particles cannot be seen with the naked eye, collectively they can appear as black soot, dust cloud or grey hazes. Particulate matter may be generated by natural process (e.g., pollen, bacteria, viruses, fungi, mold, yeast, salt spray, soil from erosion) or through human activities, including diesel trucks, power plants, wood stoves, and industrial processes. Particulate matter can be directly emitted or can be formed in the atmosphere when gaseous pollutants such as SO 2 and NOX react to form fine particles.[2] When El Nino Southern Oscillation (ENSO) phenomena occurred in certain year, it will shift the rainfall pattern over different regions around the globe. Many places in Southeast Asia countries experience dry conditions during an ENSO event. Due to that event, more open burning activities occurred which contributed to more severe haze events This study analyzes PM-10 concentration with seasonal variation in Peninsular, Sabah and Sarawak during year 1998 until 2007. Parameter that will be analyzed in this analysis will include PM-10 concentration from Tapered Element Oscillating Microbalance (TEOM), maximum temperature, rainfall amount, wind direction and relative humidity (RH).
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2.0 DATA AND METHODS 2.1 Instrumentation
Tapered Element Oscillating Microbalance (TEOM) Tapered Element Oscillating Microbalance (TEOM) was used for real-time measurement of PM10 concentrations at the Malaysian Meteorological Department’s air pollution monitoring network whereby daily 24-hour continuous air monitoring are being carried out. The TEOM is a true “gravimetric” instrument that draws ambient air through a filter at a constant flow rate, continuously weighing the filter and calculating near real-time (10 minute) mass concentrations. In addition, the instrument computes the total mass accumulation on the collection filter, as well as 30-minute, 1-hour, 8-hour and 24-hour averages of the mass concentration. The use of a hydrophobic filter material, along with sample collection at above-ambient temperature (50°C), reduces the necessity for humidity equilibration. When the instrument samples, the ambient sample stream first passes through the PM-10 inlet [Diagram 1]. At its design flow rate of 16.7 l/min, this inlet allows particles 4
smaller than 10 μm diameter to pass through. At the exit of the PM-10 inlet, the 16.7 l/min flow is isokinetically (constantly) split into a 3 l/min sample stream that is sent to the instrument’s mass transducer and a 13.7 l/min exhaust stream. Inside the mass transducer, this sample air stream passes through a filter made of Teflon-coated borosilicate glass fiber. This filter is weighed every two seconds. The difference between the filter’s current weight and the filter’s initial weight (as automatically measured by the instrument after the installation of the filter) gives the total mass of the collected particulate matter. These instantaneous readings of total mass are then smoothed exponentially (using a selectable time constant) to reduce noise.
Diagram 1 - The Flow of Sample Stream through TEOM Next, the mass rate is calculated by taking the change in the smoothed total mass between the current reading and the immediately preceding one and expressing this as a mass rate in g/sec. This mass rate is also smoothed exponentially to reduce noise. 5
Finally, the mass concentration in μg/m3 is computed by dividing the mass rate by the flow rate (corrected to EPA standard temperature and pressure and expressed in m3/sec), and then multiplying the result by 106 to convert from g/m3 to μg/m3. Internal temperatures in the instrument are controlled to minimize the effects of changing ambient conditions. The sample stream is preheated to 50°C before entering the mass transducer so that the sample filter always collects under conditions of very low and relatively constant humidity.
2.2 The Flow System Diagram 1 shows the flow of the sample stream through the TEOM. The particle size separation at 10 μm diameter takes place as the sample proceeds through the PM10 inlet. The flow splitter separates the total flow (16.7 l/min) into two parts: a main flow of 3 l/min that enters the sensor unit through the sample tube, and the auxiliary (bypass) flow of 13.7 l/min. The main flow passes through the exchangeable filter in the mass transducer [Diagram 2] and then proceeds through an air tube and in-line filter to a mass flow controller. The bypass flow is filtered in the large bypass in-line filter before it enters a second mass flow controller. A single pump provides the vacuum necessary to draw the sample stream through the system.
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Diagram 2- The TEOM Sensor Unit - Mass Transducer 2.3 Methodology In this study, PM10 which is categorized as inhalable particles were measured in seven monitoring stations throughout Malaysia for the period from January 1998 to December 2007 except for the Tanah Rata station which only consist data from January 2006 to December 2007. The monitoring stations were chosen to represent six main regions in Malaysia, namely the Northern Region (Bayan Lepas Station), Central Region (Petaling Jaya Station), Southern Region (Senai Station), East Coast
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(Kuantan Station), Sabah (Kota Kinabalu Station) and Sarawak (Kuching Station) while the Tanah Rata Station is representing the regional background location. Since the meteorological variables have a significant influence on the dispersion of PM10 concentration and behaviour, several meteorological parameters namely rainfall amount, atmospheric pressure, temperature and humidity are also considered. Meteorological data from all the seven monitoring stations was used considering the weather information of corresponding study period. For preliminary analysis and to get an overall view of the PM10 concentration trend, monthly data was being analyzed for all the stations to produce the monthly time series. To get a better representation of PM10 concentration and to understand the influence of meteorological parameters on PM10, we have considered the daily 24hour average PM10 concentration recorded in seven monitoring stations. The data through the years 1998 to 2007 was taken up for analysis and to assess the influence of seasons on PM10, the seasons of Malaysia in a year is categorized into four different seasons namely, Northeast Monsoon (November – February), Intermonsoon (March – May), Southwest Monsoon (June-August) and Intermonsoon (September – October). After categorizing the data in different data sets, statistical analysis of PM10 data sets are carried out to investigate the trend of PM10 concentrations in Malaysia. The relationship between PM10 concentration and other meteorological parameters in the study area was analyzed using the correlation analysis. Correlation deals with relationships among variables. The correlation coefficient is a measure of linear association between two variables. Values of the correlation coefficient are always between -1 and +1. A correlation coefficient of +1 indicates that two variables are perfectly related in a positive linear sense; a correlation coefficient of -1 indicates that two variables are perfectly related in a negative linear sense, and a correlation coefficient of 0 indicates that there is no linear relationship between the two variables.
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3.0
RESULTS AND DISCUSSIONS
3.1
Seasonal Variations of PM10 concentrations
The PM10 concentrations from year 1998 to 2007 for Bayan Lepas, Petaling Jaya, Senai, Kuantan, Kota Kinabalu and Kuching Stations were presented in this study. Whereas, for Tanah Rata station, only two years data from 2006 to 2007 were presented as the TEOM system was only installed in year 2006. Based on the ambient air quality guidelines established by the Malaysian government in 1988, the recommended guidelines for PM10 concentration is 50μg/m3 for 12 months averaging times. From the analysis that have been done, the annual mean PM10 concentrations at all seven stations remained below the recommended guidelines except for Kuching in year 2006. The onset date of the monsoon season fluctuates from year to year. In this study, we define the northeast monsoon from November to February, first intermonsoon from March to May, southwest monsoon from June to August and the second intermonsoon from September to October. The mean concentrations of PM10 from 1998 to 2007 according to monsoon season at these stations are shown in Figure 1. The highest PM10 concentration at Bayan Lepas, Petaling Jaya, Kuantan, Kota Kinabalu and Kuching is observed during the southwest monsoon. The higher value of PM10 concentration during the period is mainly due to the drier weather condition, stable atmosphere, local effects and also transboundary transport of air pollutants from the biomass burning from the neighbouring countries. Whereas, for Senai and Tanah Rata station (2006-2007), the highest PM10 value is observed during the second intermonsoon. The lowest PM10 concentration is observed during northeast monsoon except for Bayan Lepas station which recorded lowest PM10 values in second intermonsoon.
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PM10 Concentration
ug/m3
Northeast Monsoon
First Intermonsoon
Southwest Monsoon
Second Intermonsoon
50 45 40 35 30 25 20 15 10 5 0 Bayan Lepas Petaling Jaya
Senai
Kuantan
Kota Kinabalu
Kuching
Tanah Rata
Figure 1: The Seasonal Mean of PM10 concentration
3.1.1 Bayan Lepas
Bayan Lepas 150
μg/m3
100
50
Jul-07
Jan-07
Jul-06
Jan-06
Jul-05
Jan-05
Jul-04
Jan-04
Jul-03
Jan-03
Jul-02
Jan-02
Jul-01
Jan-01
Jul-00
Jan-00
Jul-99
Jan-99
Jul-98
Jan-98
0
Month
Figure 2: PM10 Monthly Mean Concentration at Bayan Lepas The monthly mean concentrations at Bayan Lepas from January 1998 to December 2007 are shown in Figure 2. The missing values in the PM10 concentrations are mainly due to the instrument technical problem. Generally, the PM10 concentration at Bayan Lepas shows two maximum in the annual cycle. The first maximum is observed in February or March that is end of the northeast monsoon, while the second maximum is observed in June, July and August which is during southwest monsoon. 10
3.1.2 Petaling Jaya Petaling Jaya 150
μg/m3
100
50
Jul-07
Jan-07
Jul-06
Jan-06
Jul-05
Jan-05
Jul-04
Jan-04
Jul-03
Jan-03
Jul-02
Jan-02
Jul-01
Jan-01
Jul-00
Jan-00
Jul-99
Jan-99
Jul-98
Jan-98
0
Month
Figure 3: PM10 Monthly Mean Concentration at Petaling Jaya
The seasonal variation of PM10 concentrations at Petaling Jaya shows a maximum during southwest monsoon and a minimum during the northeast monsoon. Overall, the Petaling Jaya which is an urban site, has a higher PM10 concentration compared to the other six stations.
3.1.3 Senai Senai 150
μg/m3
100
50
Month
Figure 4: PM10 Monthly Mean Concentration at Senai
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Jul-07
Jan-07
Jul-06
Jan-06
Jul-05
Jan-05
Jul-04
Jan-04
Jul-03
Jan-03
Jul-02
Jan-02
Jul-01
Jan-01
Jul-00
Jan-00
Jul-99
Jan-99
Jul-98
Jan-98
0
Senai Station recorded the lowest value of PM10 concentration during the northeast monsoon, while the second intermonsoon showed the highest concentrations. Based on the monthly mean concentration in Figure 4, the maximum values recorded mainly during September or October month.
3.1.4 Kuantan Kuantan 150
μg/m3
100
50
Jul-07
Jan-07
Jul-06
Jan-06
Jul-05
Jan-05
Jul-04
Jan-04
Jul-03
Jan-03
Jul-02
Jan-02
Jul-01
Jan-01
Jul-00
Jan-00
Jul-99
Jan-99
Jul-98
Jan-98
0
Month
Figure 5: PM10 Monthly Mean Concentration at Kuantan
For Kuantan station, the PM10 concentration slowly increases in the beginning of the year and reach maximum during middle of the year then slowly decrease again when approaching the end of the year. The PM10 concentration at Kuantan which is situated at East Coast region remained consistent throughout the 10 years period.
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3.1.5 Kota Kinabalu Kota Kinabalu 150
μg/m3
100
50
Jul-07
Jan-07
Jul-06
Jan-06
Jul-05
Jan-05
Jul-04
Jan-04
Jul-03
Jan-03
Jul-02
Jan-02
Jul-01
Jan-01
Jul-00
Jan-00
Jul-99
Jan-99
Jul-98
Jan-98
0
Month
Figure 6: PM10 Monthly Mean Concentration at Kota Kinabalu
The highest monthly mean concentration at Kota Kinabalu is observed during the beginning of the year 1998,associated with the severe haze episode that occurred in1997/1998 during the strongest El-Nino event. The following years, the highest monthly mean concentration is mainly during July, August or September month.
3.1.6 Kuching Kuching 150
μg/m3
100
50
Month
Figure 7: PM10 Monthly Mean Concentration at Kuching
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Jul-07
Jan-07
Jul-06
Jan-06
Jul-05
Jan-05
Jul-04
Jan-04
Jul-03
Jan-03
Jul-02
Jan-02
Jul-01
Jan-01
Jul-00
Jan-00
Jul-99
Jan-99
Jul-98
Jan-98
0
For the 10 years study period, the PM10 concentrations at Kuching from 1998 to 2000 shows high values in the month of March and April, whereas starting from year 2001, the highest PM10 concentrations is observed in July, August and September.
3.1.7 Tanah Rata The Tanah Rata station is representing the regional background station. Located at highland area, the PM10 concentration at Tanah Rata is relatively lower than all the other six stations at the lowland area. The higher value of monthly concentration was observed in July to October 2006 which coincides with several severe haze episode during that period. Tanah Rata 150
μg/m3
100
50
Dec-07
Oct-07
Nov-07
Sep-07
Aug-07
Jul-07
Jun-07
May-07
Apr-07
Mar-07
Jan-07
Feb-07
Dec-06
Nov-06
Oct-06
Sep-06
Jul-06
Aug-06
Jun-06
May-06
Apr-06
Mar-06
Feb-06
Jan-06
0
Month
Figure 8: PM10 Monthly Mean Concentration at Tanah Rata
3.2
The influence of meteorological parameters and seasonal effects on
PM10 concentrations Meteorological parameters have a significant influence on PM10 concentrations. To asses the effect of meteorological parameters to PM10 concentrations, an analysis was conducted on the relationship between PM10 concentrations and relative humidity, maximum temperature, rainfall and wind direction according to each monsoon season. 14
3.2.1 Maximum Temperature The correlation between the maximum temperature of a day and daily mean PM10 concentration according to season is show in Table 1. All the correlation results for each station and each monsoon season show a positive correlation between maximum temperature and PM10 concentration. Although the correlation result is between low to moderate, we can conclude that when the temperature increase, the PM10 concentration will also increase. Stations Bayan Petaling Senai Kuantan Kota Kuching Tanah Season Lepas Jaya Kinabalu Rata Northeast 0.387 0.133 0.063 0.286 0.108 0.147 0.0923 monsoon First 0.506 0.285 0.104 0.374 0.283 0.108 0.2853 intermonsoon Southwest 0.311 0.073 0.064 0.184 0.146 0.340 0.4891 monsoon Second 0.231 0.122 0.019 0.143 0.045 0.162 0.5394 intermonsoon Table 1: Correlation between daily mean PM10 concentration and maximum temperature
3.2.2 Mean Relative Humidity The daily mean relative humidity shows a negative correlation with daily mean PM10 concentrations for all seven stations and also for all four monsoon season. Petaling Jaya and Senai have a weaker correlation than other stations. The negative correlation shows that higher value of PM10 concentration is associated with lower value of relative humidity. Stations
Bayan Lepas
Petaling Senai Jaya
Kuantan
Kota Kuching Kinabalu
Tanah Rata
Season Northeast -0.446 -0.012 -0.073 -0.548 -0.373 -0.402 monsoon First -0.405 -0.032 -0.027 -0.449 -0.458 -0.279 intermonsoon Southwest -0.228 -0.123 -0.086 -0.362 -0.497 -0.524 monsoon Second -0.202 -0.086 -0.107 -0.261 -0.324 -0.373 intermonsoon Table 2: Correlation between daily mean PM10 concentration and relative humidity 15
3.2.3 Rainfall amount Rainfall has an important feature to deposit and wash out the aerosol in the atmosphere. All of the rainfall amount and PM10 concentration are negatively correlated except for Petaling Jaya and Senai Station during the second intermonsoon and Tanah Rata during the first intermonsoon. The negative correlation shows that when the rainfall amount is high, the PM10 concentration will decrease. Stations
Bayan Lepas
Petaling Senai Jaya
Kuantan
Kota Kuching Kinabalu
Tanah Rata
Season Northeast -0.206 0.047 -0.067 -0.361 -0.193 -0.192 -0.2377 monsoon First -0.179 -0.024 -0.062 -0.174 -0.145 -0.145 0.0156 intermonsoon Southwest -0.186 -0.100 -0.040 -0.123 -0.107 -0.146 -0.2566 monsoon Second -0.176 0.036 0.018 -0.130 -0.108 -0.135 -0.1078 intermonsoon Table 3: Correlation between daily mean PM10 concentration and rainfall amount
3.2.4 Wind Direction Wind plays an important role in transporting and dispersing the air pollutants. The seasonal wind flow pattern in Malaysia distinguished the monsoon season. During southwest monsoon, the prevailing wind flow is generally southwesterly and light. Whereas during the northeast monsoon, steady easterly or northeasterly winds prevail in the country. The winds are generally light and variable during the two intermonsoon seasons. The highest PM10 concentration in Senai is observed during the second intermonsoon season. The prevailing wind direction in Senai for September is from the south while October is from the west (see Figure 9). It is indicated probably the significant source of PM10 could be from the burning activities from the neighbouring country. The highest PM10 concentration at Bayan Lepas, Kota Kinabalu, Kuantan, Kuching and Petaling Jaya is observed during southwest monsoon. 16
For Bayan Lepas, the 1998 to 2007 monthly wind roses show that the wind is generally from the north throughout the year except for July where the dominant wind is from the south to southwest (refer Figure 11). Referring to Figure 12, the prevailing wind throughout the year at Kota Kinabalu is from the east. The wind pattern over this station is influenced by the easterlies blowing from the Pacific. There is a possibility that higher values of PM 10 concentration during the drier season is contributed by the local burnings and transportations and not so much coming from the neighbouring country. From Figure 13, the wind roses in Kuantan show that the wind is blowing mainly from the north from January to April and October to December. Whereas from May to September, the wind is blowing mainly from the south to southwest. It is quite noticeable that the higher value of PM10 concentration in Kuantan is during the southwest monsoon and second intermonsoon. In Petaling Jaya, the wind is blowing mainly from the northwest in December, January and February, from the west in March, October and November, from the northeast in April to June and from the east during July to September. (refer Figure14). The chaotic wind pattern in Petaling Jaya is due to location of the Meteorological station which is surrounded by the tall buildings and it’s difficult to relate the wind pattern with the PM10 concentration in Petaling Jaya. For Kuching station, the monthly wind roses in Figure 15 show that the wind is blowing mainly from the north from January to March. From April to September, the prevailing wind is from the southeast. Whereas, westerly prevails during October to December. The surface wind direction does not show significant influence on PM10 concentration. Therefore, further study is needed to look into wind pattern at several levels over the region.
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Figure 9: Monthly wind roses at Senai (1998-2007) 18
Figure 10: Monthly wind roses at Tanah Rata (2006-2007) 19
Figure 11: Monthly wind roses at Bayan Lepas (1998-2007)
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Figure 12: Monthly wind roses at Kota Kinabalu (1998-2007)
21
Figure 13: Monthly wind roses at Kuantan (1998-2007)
22
Figure 14: Monthly wind roses at Petaling Jaya (1998-2007)
23
Figure 15: Monthly wind roses at Kuching (1998-2007) 24
4.0
CONCLUSION AND RECOMMENDATION
From the analysis that has been done, it is quite obvious that the higher concentration of PM10 usually occurred during the drier season of Southwest monsoon which is from June to August, especially in the areas of Penang, central Peninsular and western part of Sarawak, Similarly with areas in eastern part of Pahang and western part of Sabah but with lower concentration values. The influence of meteorological parameter namely wind direction, rainfall amount, maximum temperature and relative humidity are significant either reducing or increasing the concentration of PM10. Among the meteorological parameters that influence quite substantially to the daily PM10 concentration is the maximum temperature, where it shows low to moderate positive correlation. The highest correlation of 0.506 calculated in Bayan Lepas during the first inter-monsoon, while Senai showed the lowest. Similarly, the daily mean RH and Daily rainfall amount showed between low to moderate negative correlation with station in Senai and Petaling Jaya recorded among the lowest correlation both for RH and rainfall amount. Even though the wind direction play an important role in contributing to the concentration of PM10, but due to the changing landscape surrounding the monitoring station, such as Petaling Jaya, the influence of wind direction to PM10 concentration becoming insignificant. Since surface wind direction alone does not show significant influence on PM10 concentration, therefore, further analysis is crucial to look at the influence of wind pattern at different levels. This study analysis focussed on the monthly wind data rather than the hourly data, it’s then recommended that the investigation need to be expanded using the hourly data. In general, the seasonal analyses of the PM10 concentration from the seven stations, concluded that the higher value of PM-10 concentration is recorded during the southwest monsoon, which is considered as the driest season for the year. On the other hand the lowest values of PM10 concentration is recorded during the Northeast Monsoon which is the wet period of the year that hampered the burning 25
activities in the country as well as in the neighbouring country. However, all the seven stations show that the concentration values remained below recommended guideline value of 50μg/m3 that indicate the air quality of most places in the country is still in good category.
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References [1] Application of Wavelet Transform on Airborne Suspended Particulate Matter and Meteorological Temporal Variations; Mokhtar Shaharuddin, Azami Zaharim, Mohd. Jailani Mohd. Nor, Othman A. Karim, Kamaruzzaman Sopian;UKM February 2008. [2] Spatio-Temporal Characteristic of PM10 Concentration Across Malaysia. Juneng, L, M.T. Latif, F.T. Tangang, and H. Mansor (2009). Atmospheric Environment, 43(30):4584-4594 [3] PM10 and Total Suspended Particulates (TSP) Measurements In Various Power Stations; Masitah Alias, Zaini Hamzah, Lee See Kenn; The Malaysian Journal of Analytical Sciences Vol 11 No 1 (2007): 255 – 261 [4] http://www.epa.gov/airtrends/aqtrnd95/pm10.html [5] http://www.met.gov.my/index.php_ [6] http://iee.osu.edu/education/downloads/Aerosolandglobalwarming.pdf
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2
The Study of Seasonal Variation of PM10 Concentration in Peninsular, Sabah and Sarawak (Nur Aleesha Abdullah, Siti Hawa Shuhaimi, Toh Ying Ying, Afizal Haqeem Shapee, Maznorizan Mohamad)
ABSTRACT To assess the influence of seasonal variation on PM-10 concentration, Malaysia is categorized according to four different seasons namely, Northeast Monsoon (November-February), First Intermonsoon (March-May), Southwest Monsoon (JuneAugust) and Second Intermonsoon (September – October). The monitoring stations were chosen to represent six main regions in Malaysia, namely the Northern Region (Bayan Lepas Station), Central Region (Petaling Jaya Station), Southern Region (Senai Station), East Coast (Kuantan Station), Sabah (Kota Kinabalu Station) and Sarawak (Kuching Station) while the Tanah Rata Station is representing the background location. Tapered
Element
Oscillating
Microbalance
(TEOM)
is
used
for
real-time
measurement of PM-10 concentrations at MMD’s air pollution monitoring network where the daily 24-hour continuous air monitoring are being carried out. In this study, PM-10 and the meteorological parameter were analyzed to investigate the seasonal variation on PM-10 concentration and meteorological parameter. Statistical analyses of PM-10 data sets were carried out to investigate the seasonal trend of PM-10 concentrations in Malaysia. The result suggested that the PM-10 concentration recorded during Southwest monsoon is relatively higher as compared to the concentration value recorded during Northeast Monsoon. Keyword: Particulate matter, aerosol, total suspended particulate, TEOM.
1
1.0 INTRODUCTION Malaysia is a maritime country located at lat 2˚30’ North and long 112˚ 30’ East and experienced equatorial climate. Hot and humid with relative humidity ranging from 80-90 percent, except in the highland, and the temperature averages from 20-30˚C throughout the year. The climate is governed by the regime of the northeast and southwest monsoons. During Northeast Monsoon (November-March), areas on the east side of Peninsular such as Kelantan, Terengganu and Pahang will experience heavy rainfall. As for Sabah and Sarawak, they will experience the same heavy rainfall through this period of time. The weather systems that develop in conjunction with cold air outbreaks from Siberia produce heavy rains, which often cause severe floods along the east coast states of Peninsular Malaysia [ 4]. On the other hand, during the Southwest Monsoon from May to September, Sumatras will bring significant amount of rainfall to the western side of Peninsular. The affected areas generally will be from coastal areas of Perak and down to western part of Johore. Moreover, the driest period in most districts occurring in June to August. Malaysia has experienced several haze period during this period for the past years. The haze episodes have created great interest because of its harmful health effects and social economic consequences. The most immediate effect is the reduction of visibility and bronchial related disease. The most severe haze episode was in 1997 that shrouded most part of the country, especially the Klang Valley and state of Sarawak. During haze periods, suspended particulate matter was found to be a major pollutant, while other parameters remained within standard level. The main sources of suspended particulates are forest fire from neighbouring country. Besides that, smoke from local burning also contributed to the severity of the haze. During non-haze period, most particulate sources were from vehicular emission [1]. The concentrations of suspended particulate tend to be higher with higher air temperature and stable atmosphere. Conversely, wet season has cleaning effects over the suspended particulate. Strong wind will increase the intensity of the vertical
2
and horizontal transport, thus reduce suspended particulate concentration in atmosphere [1]. An aerosol is a suspension of droplets or particles in the air and those particles with a diameter range from 10-3 to 20 µm. In meteorology, the term is often used to describe the particles suspended within the gas, such as minute fragment of seasalt, dust, organic matter, and smoke. Such aerosols enter the atmosphere by natural processes such as volcano eruption and by human activities like burning of fossil fuels. Aerosols absorb heat and may act as condensation nuclei. Particulate matter-10 (PM10) is used to describe particles with diameter of 10 micrometers or less for solid or liquid found suspended in the atmosphere. While individual particles cannot be seen with the naked eye, collectively they can appear as black soot, dust cloud or grey hazes. Particulate matter may be generated by natural process (e.g., pollen, bacteria, viruses, fungi, mold, yeast, salt spray, soil from erosion) or through human activities, including diesel trucks, power plants, wood stoves, and industrial processes. Particulate matter can be directly emitted or can be formed in the atmosphere when gaseous pollutants such as SO 2 and NOX react to form fine particles.[2] When El Nino Southern Oscillation (ENSO) phenomena occurred in certain year, it will shift the rainfall pattern over different regions around the globe. Many places in Southeast Asia countries experience dry conditions during an ENSO event. Due to that event, more open burning activities occurred which contributed to more severe haze events This study analyzes PM-10 concentration with seasonal variation in Peninsular, Sabah and Sarawak during year 1998 until 2007. Parameter that will be analyzed in this analysis will include PM-10 concentration from Tapered Element Oscillating Microbalance (TEOM), maximum temperature, rainfall amount, wind direction and relative humidity (RH).
3
2.0 DATA AND METHODS 2.1 Instrumentation
Tapered Element Oscillating Microbalance (TEOM) Tapered Element Oscillating Microbalance (TEOM) was used for real-time measurement of PM10 concentrations at the Malaysian Meteorological Department’s air pollution monitoring network whereby daily 24-hour continuous air monitoring are being carried out. The TEOM is a true “gravimetric” instrument that draws ambient air through a filter at a constant flow rate, continuously weighing the filter and calculating near real-time (10 minute) mass concentrations. In addition, the instrument computes the total mass accumulation on the collection filter, as well as 30-minute, 1-hour, 8-hour and 24-hour averages of the mass concentration. The use of a hydrophobic filter material, along with sample collection at above-ambient temperature (50°C), reduces the necessity for humidity equilibration. When the instrument samples, the ambient sample stream first passes through the PM-10 inlet [Diagram 1]. At its design flow rate of 16.7 l/min, this inlet allows particles 4
smaller than 10 μm diameter to pass through. At the exit of the PM-10 inlet, the 16.7 l/min flow is isokinetically (constantly) split into a 3 l/min sample stream that is sent to the instrument’s mass transducer and a 13.7 l/min exhaust stream. Inside the mass transducer, this sample air stream passes through a filter made of Teflon-coated borosilicate glass fiber. This filter is weighed every two seconds. The difference between the filter’s current weight and the filter’s initial weight (as automatically measured by the instrument after the installation of the filter) gives the total mass of the collected particulate matter. These instantaneous readings of total mass are then smoothed exponentially (using a selectable time constant) to reduce noise.
Diagram 1 - The Flow of Sample Stream through TEOM Next, the mass rate is calculated by taking the change in the smoothed total mass between the current reading and the immediately preceding one and expressing this as a mass rate in g/sec. This mass rate is also smoothed exponentially to reduce noise. 5
Finally, the mass concentration in μg/m3 is computed by dividing the mass rate by the flow rate (corrected to EPA standard temperature and pressure and expressed in m3/sec), and then multiplying the result by 106 to convert from g/m3 to μg/m3. Internal temperatures in the instrument are controlled to minimize the effects of changing ambient conditions. The sample stream is preheated to 50°C before entering the mass transducer so that the sample filter always collects under conditions of very low and relatively constant humidity.
2.2 The Flow System Diagram 1 shows the flow of the sample stream through the TEOM. The particle size separation at 10 μm diameter takes place as the sample proceeds through the PM10 inlet. The flow splitter separates the total flow (16.7 l/min) into two parts: a main flow of 3 l/min that enters the sensor unit through the sample tube, and the auxiliary (bypass) flow of 13.7 l/min. The main flow passes through the exchangeable filter in the mass transducer [Diagram 2] and then proceeds through an air tube and in-line filter to a mass flow controller. The bypass flow is filtered in the large bypass in-line filter before it enters a second mass flow controller. A single pump provides the vacuum necessary to draw the sample stream through the system.
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Diagram 2- The TEOM Sensor Unit - Mass Transducer 2.3 Methodology In this study, PM10 which is categorized as inhalable particles were measured in seven monitoring stations throughout Malaysia for the period from January 1998 to December 2007 except for the Tanah Rata station which only consist data from January 2006 to December 2007. The monitoring stations were chosen to represent six main regions in Malaysia, namely the Northern Region (Bayan Lepas Station), Central Region (Petaling Jaya Station), Southern Region (Senai Station), East Coast
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(Kuantan Station), Sabah (Kota Kinabalu Station) and Sarawak (Kuching Station) while the Tanah Rata Station is representing the regional background location. Since the meteorological variables have a significant influence on the dispersion of PM10 concentration and behaviour, several meteorological parameters namely rainfall amount, atmospheric pressure, temperature and humidity are also considered. Meteorological data from all the seven monitoring stations was used considering the weather information of corresponding study period. For preliminary analysis and to get an overall view of the PM10 concentration trend, monthly data was being analyzed for all the stations to produce the monthly time series. To get a better representation of PM10 concentration and to understand the influence of meteorological parameters on PM10, we have considered the daily 24hour average PM10 concentration recorded in seven monitoring stations. The data through the years 1998 to 2007 was taken up for analysis and to assess the influence of seasons on PM10, the seasons of Malaysia in a year is categorized into four different seasons namely, Northeast Monsoon (November – February), Intermonsoon (March – May), Southwest Monsoon (June-August) and Intermonsoon (September – October). After categorizing the data in different data sets, statistical analysis of PM10 data sets are carried out to investigate the trend of PM10 concentrations in Malaysia. The relationship between PM10 concentration and other meteorological parameters in the study area was analyzed using the correlation analysis. Correlation deals with relationships among variables. The correlation coefficient is a measure of linear association between two variables. Values of the correlation coefficient are always between -1 and +1. A correlation coefficient of +1 indicates that two variables are perfectly related in a positive linear sense; a correlation coefficient of -1 indicates that two variables are perfectly related in a negative linear sense, and a correlation coefficient of 0 indicates that there is no linear relationship between the two variables.
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3.0
RESULTS AND DISCUSSIONS
3.1
Seasonal Variations of PM10 concentrations
The PM10 concentrations from year 1998 to 2007 for Bayan Lepas, Petaling Jaya, Senai, Kuantan, Kota Kinabalu and Kuching Stations were presented in this study. Whereas, for Tanah Rata station, only two years data from 2006 to 2007 were presented as the TEOM system was only installed in year 2006. Based on the ambient air quality guidelines established by the Malaysian government in 1988, the recommended guidelines for PM10 concentration is 50μg/m3 for 12 months averaging times. From the analysis that have been done, the annual mean PM10 concentrations at all seven stations remained below the recommended guidelines except for Kuching in year 2006. The onset date of the monsoon season fluctuates from year to year. In this study, we define the northeast monsoon from November to February, first intermonsoon from March to May, southwest monsoon from June to August and the second intermonsoon from September to October. The mean concentrations of PM10 from 1998 to 2007 according to monsoon season at these stations are shown in Figure 1. The highest PM10 concentration at Bayan Lepas, Petaling Jaya, Kuantan, Kota Kinabalu and Kuching is observed during the southwest monsoon. The higher value of PM10 concentration during the period is mainly due to the drier weather condition, stable atmosphere, local effects and also transboundary transport of air pollutants from the biomass burning from the neighbouring countries. Whereas, for Senai and Tanah Rata station (2006-2007), the highest PM10 value is observed during the second intermonsoon. The lowest PM10 concentration is observed during northeast monsoon except for Bayan Lepas station which recorded lowest PM10 values in second intermonsoon.
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PM10 Concentration
ug/m3
Northeast Monsoon
First Intermonsoon
Southwest Monsoon
Second Intermonsoon
50 45 40 35 30 25 20 15 10 5 0 Bayan Lepas Petaling Jaya
Senai
Kuantan
Kota Kinabalu
Kuching
Tanah Rata
Figure 1: The Seasonal Mean of PM10 concentration
3.1.1 Bayan Lepas
Bayan Lepas 150
μg/m3
100
50
Jul-07
Jan-07
Jul-06
Jan-06
Jul-05
Jan-05
Jul-04
Jan-04
Jul-03
Jan-03
Jul-02
Jan-02
Jul-01
Jan-01
Jul-00
Jan-00
Jul-99
Jan-99
Jul-98
Jan-98
0
Month
Figure 2: PM10 Monthly Mean Concentration at Bayan Lepas The monthly mean concentrations at Bayan Lepas from January 1998 to December 2007 are shown in Figure 2. The missing values in the PM10 concentrations are mainly due to the instrument technical problem. Generally, the PM10 concentration at Bayan Lepas shows two maximum in the annual cycle. The first maximum is observed in February or March that is end of the northeast monsoon, while the second maximum is observed in June, July and August which is during southwest monsoon. 10
3.1.2 Petaling Jaya Petaling Jaya 150
μg/m3
100
50
Jul-07
Jan-07
Jul-06
Jan-06
Jul-05
Jan-05
Jul-04
Jan-04
Jul-03
Jan-03
Jul-02
Jan-02
Jul-01
Jan-01
Jul-00
Jan-00
Jul-99
Jan-99
Jul-98
Jan-98
0
Month
Figure 3: PM10 Monthly Mean Concentration at Petaling Jaya
The seasonal variation of PM10 concentrations at Petaling Jaya shows a maximum during southwest monsoon and a minimum during the northeast monsoon. Overall, the Petaling Jaya which is an urban site, has a higher PM10 concentration compared to the other six stations.
3.1.3 Senai Senai 150
μg/m3
100
50
Month
Figure 4: PM10 Monthly Mean Concentration at Senai
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Jul-07
Jan-07
Jul-06
Jan-06
Jul-05
Jan-05
Jul-04
Jan-04
Jul-03
Jan-03
Jul-02
Jan-02
Jul-01
Jan-01
Jul-00
Jan-00
Jul-99
Jan-99
Jul-98
Jan-98
0
Senai Station recorded the lowest value of PM10 concentration during the northeast monsoon, while the second intermonsoon showed the highest concentrations. Based on the monthly mean concentration in Figure 4, the maximum values recorded mainly during September or October month.
3.1.4 Kuantan Kuantan 150
μg/m3
100
50
Jul-07
Jan-07
Jul-06
Jan-06
Jul-05
Jan-05
Jul-04
Jan-04
Jul-03
Jan-03
Jul-02
Jan-02
Jul-01
Jan-01
Jul-00
Jan-00
Jul-99
Jan-99
Jul-98
Jan-98
0
Month
Figure 5: PM10 Monthly Mean Concentration at Kuantan
For Kuantan station, the PM10 concentration slowly increases in the beginning of the year and reach maximum during middle of the year then slowly decrease again when approaching the end of the year. The PM10 concentration at Kuantan which is situated at East Coast region remained consistent throughout the 10 years period.
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3.1.5 Kota Kinabalu Kota Kinabalu 150
μg/m3
100
50
Jul-07
Jan-07
Jul-06
Jan-06
Jul-05
Jan-05
Jul-04
Jan-04
Jul-03
Jan-03
Jul-02
Jan-02
Jul-01
Jan-01
Jul-00
Jan-00
Jul-99
Jan-99
Jul-98
Jan-98
0
Month
Figure 6: PM10 Monthly Mean Concentration at Kota Kinabalu
The highest monthly mean concentration at Kota Kinabalu is observed during the beginning of the year 1998,associated with the severe haze episode that occurred in1997/1998 during the strongest El-Nino event. The following years, the highest monthly mean concentration is mainly during July, August or September month.
3.1.6 Kuching Kuching 150
μg/m3
100
50
Month
Figure 7: PM10 Monthly Mean Concentration at Kuching
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Jul-07
Jan-07
Jul-06
Jan-06
Jul-05
Jan-05
Jul-04
Jan-04
Jul-03
Jan-03
Jul-02
Jan-02
Jul-01
Jan-01
Jul-00
Jan-00
Jul-99
Jan-99
Jul-98
Jan-98
0
For the 10 years study period, the PM10 concentrations at Kuching from 1998 to 2000 shows high values in the month of March and April, whereas starting from year 2001, the highest PM10 concentrations is observed in July, August and September.
3.1.7 Tanah Rata The Tanah Rata station is representing the regional background station. Located at highland area, the PM10 concentration at Tanah Rata is relatively lower than all the other six stations at the lowland area. The higher value of monthly concentration was observed in July to October 2006 which coincides with several severe haze episode during that period. Tanah Rata 150
μg/m3
100
50
Dec-07
Oct-07
Nov-07
Sep-07
Aug-07
Jul-07
Jun-07
May-07
Apr-07
Mar-07
Jan-07
Feb-07
Dec-06
Nov-06
Oct-06
Sep-06
Jul-06
Aug-06
Jun-06
May-06
Apr-06
Mar-06
Feb-06
Jan-06
0
Month
Figure 8: PM10 Monthly Mean Concentration at Tanah Rata
3.2
The influence of meteorological parameters and seasonal effects on
PM10 concentrations Meteorological parameters have a significant influence on PM10 concentrations. To asses the effect of meteorological parameters to PM10 concentrations, an analysis was conducted on the relationship between PM10 concentrations and relative humidity, maximum temperature, rainfall and wind direction according to each monsoon season. 14
3.2.1 Maximum Temperature The correlation between the maximum temperature of a day and daily mean PM10 concentration according to season is show in Table 1. All the correlation results for each station and each monsoon season show a positive correlation between maximum temperature and PM10 concentration. Although the correlation result is between low to moderate, we can conclude that when the temperature increase, the PM10 concentration will also increase. Stations Bayan Petaling Senai Kuantan Kota Kuching Tanah Season Lepas Jaya Kinabalu Rata Northeast 0.387 0.133 0.063 0.286 0.108 0.147 0.0923 monsoon First 0.506 0.285 0.104 0.374 0.283 0.108 0.2853 intermonsoon Southwest 0.311 0.073 0.064 0.184 0.146 0.340 0.4891 monsoon Second 0.231 0.122 0.019 0.143 0.045 0.162 0.5394 intermonsoon Table 1: Correlation between daily mean PM10 concentration and maximum temperature
3.2.2 Mean Relative Humidity The daily mean relative humidity shows a negative correlation with daily mean PM10 concentrations for all seven stations and also for all four monsoon season. Petaling Jaya and Senai have a weaker correlation than other stations. The negative correlation shows that higher value of PM10 concentration is associated with lower value of relative humidity. Stations
Bayan Lepas
Petaling Senai Jaya
Kuantan
Kota Kuching Kinabalu
Tanah Rata
Season Northeast -0.446 -0.012 -0.073 -0.548 -0.373 -0.402 monsoon First -0.405 -0.032 -0.027 -0.449 -0.458 -0.279 intermonsoon Southwest -0.228 -0.123 -0.086 -0.362 -0.497 -0.524 monsoon Second -0.202 -0.086 -0.107 -0.261 -0.324 -0.373 intermonsoon Table 2: Correlation between daily mean PM10 concentration and relative humidity 15
3.2.3 Rainfall amount Rainfall has an important feature to deposit and wash out the aerosol in the atmosphere. All of the rainfall amount and PM10 concentration are negatively correlated except for Petaling Jaya and Senai Station during the second intermonsoon and Tanah Rata during the first intermonsoon. The negative correlation shows that when the rainfall amount is high, the PM10 concentration will decrease. Stations
Bayan Lepas
Petaling Senai Jaya
Kuantan
Kota Kuching Kinabalu
Tanah Rata
Season Northeast -0.206 0.047 -0.067 -0.361 -0.193 -0.192 -0.2377 monsoon First -0.179 -0.024 -0.062 -0.174 -0.145 -0.145 0.0156 intermonsoon Southwest -0.186 -0.100 -0.040 -0.123 -0.107 -0.146 -0.2566 monsoon Second -0.176 0.036 0.018 -0.130 -0.108 -0.135 -0.1078 intermonsoon Table 3: Correlation between daily mean PM10 concentration and rainfall amount
3.2.4 Wind Direction Wind plays an important role in transporting and dispersing the air pollutants. The seasonal wind flow pattern in Malaysia distinguished the monsoon season. During southwest monsoon, the prevailing wind flow is generally southwesterly and light. Whereas during the northeast monsoon, steady easterly or northeasterly winds prevail in the country. The winds are generally light and variable during the two intermonsoon seasons. The highest PM10 concentration in Senai is observed during the second intermonsoon season. The prevailing wind direction in Senai for September is from the south while October is from the west (see Figure 9). It is indicated probably the significant source of PM10 could be from the burning activities from the neighbouring country. The highest PM10 concentration at Bayan Lepas, Kota Kinabalu, Kuantan, Kuching and Petaling Jaya is observed during southwest monsoon. 16
For Bayan Lepas, the 1998 to 2007 monthly wind roses show that the wind is generally from the north throughout the year except for July where the dominant wind is from the south to southwest (refer Figure 11). Referring to Figure 12, the prevailing wind throughout the year at Kota Kinabalu is from the east. The wind pattern over this station is influenced by the easterlies blowing from the Pacific. There is a possibility that higher values of PM 10 concentration during the drier season is contributed by the local burnings and transportations and not so much coming from the neighbouring country. From Figure 13, the wind roses in Kuantan show that the wind is blowing mainly from the north from January to April and October to December. Whereas from May to September, the wind is blowing mainly from the south to southwest. It is quite noticeable that the higher value of PM10 concentration in Kuantan is during the southwest monsoon and second intermonsoon. In Petaling Jaya, the wind is blowing mainly from the northwest in December, January and February, from the west in March, October and November, from the northeast in April to June and from the east during July to September. (refer Figure14). The chaotic wind pattern in Petaling Jaya is due to location of the Meteorological station which is surrounded by the tall buildings and it’s difficult to relate the wind pattern with the PM10 concentration in Petaling Jaya. For Kuching station, the monthly wind roses in Figure 15 show that the wind is blowing mainly from the north from January to March. From April to September, the prevailing wind is from the southeast. Whereas, westerly prevails during October to December. The surface wind direction does not show significant influence on PM10 concentration. Therefore, further study is needed to look into wind pattern at several levels over the region.
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Figure 9: Monthly wind roses at Senai (1998-2007) 18
Figure 10: Monthly wind roses at Tanah Rata (2006-2007) 19
Figure 11: Monthly wind roses at Bayan Lepas (1998-2007)
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Figure 12: Monthly wind roses at Kota Kinabalu (1998-2007)
21
Figure 13: Monthly wind roses at Kuantan (1998-2007)
22
Figure 14: Monthly wind roses at Petaling Jaya (1998-2007)
23
Figure 15: Monthly wind roses at Kuching (1998-2007) 24
4.0
CONCLUSION AND RECOMMENDATION
From the analysis that has been done, it is quite obvious that the higher concentration of PM10 usually occurred during the drier season of Southwest monsoon which is from June to August, especially in the areas of Penang, central Peninsular and western part of Sarawak, Similarly with areas in eastern part of Pahang and western part of Sabah but with lower concentration values. The influence of meteorological parameter namely wind direction, rainfall amount, maximum temperature and relative humidity are significant either reducing or increasing the concentration of PM10. Among the meteorological parameters that influence quite substantially to the daily PM10 concentration is the maximum temperature, where it shows low to moderate positive correlation. The highest correlation of 0.506 calculated in Bayan Lepas during the first inter-monsoon, while Senai showed the lowest. Similarly, the daily mean RH and Daily rainfall amount showed between low to moderate negative correlation with station in Senai and Petaling Jaya recorded among the lowest correlation both for RH and rainfall amount. Even though the wind direction play an important role in contributing to the concentration of PM10, but due to the changing landscape surrounding the monitoring station, such as Petaling Jaya, the influence of wind direction to PM10 concentration becoming insignificant. Since surface wind direction alone does not show significant influence on PM10 concentration, therefore, further analysis is crucial to look at the influence of wind pattern at different levels. This study analysis focussed on the monthly wind data rather than the hourly data, it’s then recommended that the investigation need to be expanded using the hourly data. In general, the seasonal analyses of the PM10 concentration from the seven stations, concluded that the higher value of PM-10 concentration is recorded during the southwest monsoon, which is considered as the driest season for the year. On the other hand the lowest values of PM10 concentration is recorded during the Northeast Monsoon which is the wet period of the year that hampered the burning 25
activities in the country as well as in the neighbouring country. However, all the seven stations show that the concentration values remained below recommended guideline value of 50μg/m3 that indicate the air quality of most places in the country is still in good category.
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References [1] Application of Wavelet Transform on Airborne Suspended Particulate Matter and Meteorological Temporal Variations; Mokhtar Shaharuddin, Azami Zaharim, Mohd. Jailani Mohd. Nor, Othman A. Karim, Kamaruzzaman Sopian;UKM February 2008. [2] Spatio-Temporal Characteristic of PM10 Concentration Across Malaysia. Juneng, L, M.T. Latif, F.T. Tangang, and H. Mansor (2009). Atmospheric Environment, 43(30):4584-4594 [3] PM10 and Total Suspended Particulates (TSP) Measurements In Various Power Stations; Masitah Alias, Zaini Hamzah, Lee See Kenn; The Malaysian Journal of Analytical Sciences Vol 11 No 1 (2007): 255 – 261 [4] http://www.epa.gov/airtrends/aqtrnd95/pm10.html [5] http://www.met.gov.my/index.php_ [6] http://iee.osu.edu/education/downloads/Aerosolandglobalwarming.pdf
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