Page 68 - Special Topic Session (STS) - Volume 2

STS459 Norshahida S. et al.
photochemical reactions of precursors such as volatile organic compound
(VOCs) and Nitrogen Oxides (NOx) (Lee et al., 2010). During hot and sunny day,
the formation of O3 is greatly enhanced. The variation of O3 is largely depends
on meteorology variables such as sunlight, temperature and wind (Ling et al.,
2014).
Surface or Troposphere O3 contributes to a certain environmental problem
including health problems, vegetation and materials, as well as climate
changing. O3 is defined as a secondary pollutant whereby volatile organic
compounds and NOx from point sources are the precursors of Ozone in the
country. Ozone shows strong day-to-day variation and sometimes virtually
undetectable (Ramli et al., 2010). In the Malaysia environment, the main
sources of VOCs and NOx emissions are from industries and motor vehicles
particularly in urban areas (DOE 2014). In Klang Valley for example, it is found
that O3 exceedances pattern is strongly influenced by local pollutant emission
and its dispersion characteristics. It is also observed that the variation of O3
concentration is continuous in nature and its severity behaviour is often
uncertain (Shaadan et al., 2018). O3 pollution is odourless, the physical form is
invisible and the pattern of occurrence is less understood. Thus, the existence
of ozone pollution is often unaware.
According to Ghazali et al. (2014), Malaysia has not yet reached a critical
level of the air pollution as in other metropolitan areas in Asia but its potential
increased need to be assessed and predicted. Data monitoring and studies on
air quality shows that some of the air pollutants in several large cities such as
Johor, Selangor and Sabah are increasing with time and are not always at a
satisfied level in comparison to the national standard (Rafia & Ibrahim, 2002).
Since Ozone is one of the important pollutants, for the purpose of managing
and mitigating air pollution, it is important to study and predict the return
period of ozone pollution in the future period. Malaysia weather is
characterized by two main seasons, the Northwest and Southwest monsoons
and other two transaction periods. Drier weather condition often recorded
during Southwest monsoon and during the second and the first transition
period at several regions. On the other hand, more frequent and larger
amount of rain were recorded during the Northwest monsoon particularly at
the east coast region in Peninsular Malaysia. As reported by Siti et al., (2015)),
air pollution occurrence and high level of pollutants concentration often
recorded during the dry season.
There are many statistical methods and models can be used for predicting
air pollutant level. However, the application of probability models for
predicting high pollutant levels and the exceedance is rarely discussed on O3
data in the Malaysia environment. Majority of the studies had discussed on
PM10 pollutant since PM10 is reported as a major component of haze. To fill the
gap, this study will focus on the comparison of several chosen probability

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