103
7 Air and water quality observations
7.1 Air Quality Variations
Air pollution is the introduction of chemicals, particulate matter, or biological materials that cause harm or discomfort to humans or other living organisms, or damages the natural
environment, into the atmosphere.
An air pollutant is known as a substance in the air that can cause harm to humans and the environment. Pollutants can be in the form of solid particles, liquid droplets, or gases. In
addition, they can be natural or man-made.
Pollutants can be classified as either primary or secondary. Usually, primary pollutants are substances directly emitted from a process, such as ash from a volcanic eruption, the carbon
monoxide gas from a motor vehicle exhaust or sulfur dioxide released from factories.
Secondary pollutants are not emitted directly. Rather, they form in the air when primary pollutants react or interact. An important example of a secondary pollutant is ground level
ozone - one of the many secondary pollutants that make up photochemical smog.
Major primary pollutants produced by human activity include:
•
Sulfur oxides SO
x
- especially sulfur dioxide, a chemical compound with the formula SO
2
. SO
2
is produced by volcanoes and in various industrial processes. Since coal and petroleum often contain sulfur compounds, their combustion generates sulfur dioxide.
Further oxidation of SO
2
, usually in the presence of a catalyst such as NO
2
, forms H
2
SO
4
, and thus acid rain. This is one of the causes for concern over the environmental impact of the use of these fuels as power sources.
•
Nitrogen oxides NO
x
- especially nitrogen dioxide are emitted from high temperature combustion. Can be seen as the brown haze dome above or plume downwind of cities.
Nitrogen dioxide is the chemical compound with the formula NO
2
. It is one of the several nitrogen oxides. This reddish-brown toxic gas has a characteristic sharp, biting
odor. NO
2
is one of the most prominent air pollutants.
•
Carbon monoxide - is a colorless, odorless, non-irritating but very poisonous gas. It is a product by incomplete combustion of fuel such as natural gas, coal or wood. Vehicular
exhaust is a major source of carbon monoxide.
•
Carbon dioxide CO
2
- a greenhouse gas emitted from combustion but is also a gas vital to living organisms. It is a natural gas in the atmosphere.
•
Particulate matter - Particulates alternatively referred to as particulate matter PM or fine particles, are tiny particles of solid or liquid suspended in a gas. In contrast, aerosol
refers to particles and the gas together. Sources of particulate matter can be manmade or natural. Some particulates occur naturally, originating from volcanoes, dust storms,
forest and grassland fires, living vegetation, and sea spray. Human activities, such as
104 the burning of fossil fuels in vehicles, power plants and various industrial processes also
generate significant amounts of aerosols. Averaged over the globe, anthropogenic aerosols—those made by human activities—currently account for about 10 percent of
the total amount of aerosols in our atmosphere. Increased levels of fine particles in the air are linked to health hazards such as heart disease, altered lung function, lung cancer.
Table 7.1. Availability of pollution Source: Thailand Pollution Control Dept. 7.1.1.1
City PM
10
μgm
3
O
3
ppb; 10
-9
ppb CO
ppm; 10
-6
ppm SO
2
ppb; 10
-9
ppb NO
2
ppb; 10
-9
ppb
Chiang Rai 2008-2009
2008-2009 2008-2009
- -
Udon Thani
- - - - -
Phuket 1997-2009 1997-2009
- 1997-2009 -
Hat Yai Songkhla
1997-2009 1997-2009
except 1998 - 99
1997-2009 1997-2009 1997-2009 except 1998,
1999 Samut
Sakhon 1997-2009 1997-2009 1997-2009 1997-2009 1997-2009
Different pollution parameters as per the availability are plotted in Figure 7.1. It is seen from Figure 7.1a that over Chiang Rai, the average PM
10
value increase during 2009 by 88 from last year value and it is also higher than standard value of 50
μgm
3
. Similarly the maximum PM
10
value also increased from 77.8 μgm
3
in previous year to 286.4 μgm
3
in this year and is again higher than the corresponding standard value of 100
μgm
3
. Over Phuket, Hat Yai and Samut Sakhon though the values were higher than the standard value of 50 during
earlier years it is less than the standard value during recent 2 to 3 years.
Regarding the ozone O
3
in recent years it average concentration is increasing over all stations Chiang Rai, Phuket, Hat Yai and Samut Sakhon as shown in Figure 7.1b.
105
Figure 7.1. Pm
10
and O
3
concentration Source: Thailand Pollution Control Dept.
Regarding the Carbon Monoxide CO it increases from 0.6 ppm to 0.8 ppm over Chiang Rai in last one year Figure 7.2a, which is increase of 33. Similarly over Hat Yai there is
tendency of increasing CO concentration in last three years although less than that of Chiang Rai. Another point is that the average concentration of CO over Samut Sakhon is higher than
corresponding values over Hat Yai during the entire period from 1997 to 2009 except the year 2002 and 2009 Figure 7.2a.
Regarding the average SO
2
concentration the values are much higher for Samut Sakhon compared to Hat Yai and Phuket values Figure 7.2b. Still the values for all the three stations
are less than that of standard value of 50 ppb during the period from 1997 to 2009 Fig. 38d. Similarly the average NO concentration over Samut Sakhon is higher than that of
corresponding values over Hat Yai during the entire period from 1997 to 2009 Figure 7.2c.
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Figure 7.2. CO, SO
2
and NO
2
concentration Source: Thailand Pollution Control Dept.
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7.2 Water quality indicators Water Pollution
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