Forest Damage Caused by Acid Precipitation and
Pollution in Malaysia
Philip, E.1, M. Rizal1, M.K and Siti Mariam, S.2
1
Forest Research Institute Malaysia, Kepong 52109 Kuala Lumpur
2
Faculty of Applied Sciences, UiTM, Shah Alam, Selangor
email: [email protected]
Abstract
Many urgent global environmental problems confronting society such as climate change and depletion of
the stratospheric ozone layer are connected with man-made changes in the state and composition of the
atmosphere and its interactions with other environmental media. Pertinent issues like pollution and green
house gases and their impact on various ecosystems and human health have invariably posed many
questions to both policy makers and researchers. Hence a study was conducted to examine chemical
composition factors associated with pH of precipitation, stemflow and throughfall at 3 different forest
reserves, around Kuala Lumpur. Data were collected on a monthly basis for 36 months and where
possible after every rainfall. The mean acid precipitation at forests closer to pollutant source had mean
annual rainfall pH between 4.8-5.1 while forest further away from pollution source, the pH was above 5.6
and declined to 5.2 as sampling progressed. It was assumed that accelerated leaching of nutrients
occurred as a result of this acid precipitation. Ions like K+ and Mg2+ were the most vulnerable to acid
precipitation. On the other hand, uptake of anions like SO42- had increased as well.
Keywords: Stemflow, throughfall, precipitation, forest reserves, leaching
1.0
Introduction
Atmospheric pollution occurs when substances are present at concentrations sufficiently above the normal
ambient levels to produce a measurable effect on humans, animals, plants or materials. These substances
may come from natural or anthropogenic sources and may exist in the atmosphere as gases, liquids or
particulates (Wood, 1990). The major anthropogenic sources include transportation, power generation,
biomass burning and industrial processes. Once released into the atmosphere, pollutants may then be
transported by high level winds across national boundaries, diluted and physically or chemically
transformed.
The conventional acid rain precursors, sulphur dioxide and nitrogen oxides ultimately form sulphuric
acid and nitric acid which may be carried with the winds over long distances before descending in the
rain. Hence soil and water can become acidified far away from the sources of emission (National Swedish
Environmental Protection Board, 1991) As a result of the acidification, rain water becomes more acidic
and is termed acid precipitation. Acid rain is a good indicator to air pollution status.
Malaysia is also not spared from acid rain phenomenon. Anthropogenic emissions have increased over
the years as the levels of pollutants suspended in the atmosphere is increasing. The repeated occurrence
of haze nationwide and the rapid change in weather bare testimony that the air quality is on a decline.
Rapid development especially in the Klang Valley over the last decade has resulted in natural resource
contamination in the form of polluted water, degraded air quality and the accumulation of toxic and
hazardous wastes all of which affect human health and quality of living and is gaining wide attention
(Leong and Lim 1994)
As a result of climate change and pollution, vegetation distribution has also been relocated in some places
affected by atmospheric acidification; for example pollutants had removed the trees that once bordered
Germany and the former Czechoslovakia (Chadwick et al, 1994)[3]. Elsewhere, acidification has led to
depletion of fishes in lakes and damage of trees in the Scandinavian countries.
This paper had attempted to use acid precipitation as the indicator to air contamination and to assess its
impact on forest ecosystem. Acid precipitation occurs when the pH of rainfall is lower than 5.6. (Halvey,
1982). The present investigation is pursued with the objectives of studying the impacts of acid
precipitation on 3 different forest reserves. The results presented summaries the results obtained over a
three year period.
2.0
Materials and methods
2.1
Research sites
The ecosystem research of this project focused on three adjacent forest represented by lowland logged
over forest. All are located in the Klang Valley. The first site, Bukit Cerakah is situated in the industrial
hub of the Klang Valley. The second site, Bukit Bujang is a plantation forest and the third is Bukit
Lagong. Both Bukit Cerakah and Bukit Bujang are situated close to the industrial zones and are close to
roads with heavy traffic. Bukit Lagong, on the other hand is situated away from the hustle and bustle of
the city. Description of the sites and their geographical coordinates are shown in Table 1.
Table 1: Sampling Sites
Sampling Site
Description
Bukit Cerakah
(3°13’60N,
101°22’60E)
Situated in the vicinity of the industrial Shah Alam. Development has been minimal
within the site. The southern part has been developed into an agricultural park, while
to the northern side, it has been converted to housing project. This forest has been
logged some 15 years ago. There were many regenerating trees reaching over 20 m
in height. There is a dominance of Dipterocarpus sp. in this area. Bukit Cerakah is
approximately 5 km from the industrial zones and is popular amongst tourist.
Bukit Lagong
(3°15’23N.
101°38’33E)
A once vegetable farm is now the house of plantation forest consisting mainly of
Shorea curtisii and Dyera costulata. Over the years, many species from nearby forest
reserve have invaded into this area. This place is situated approximately 30 km from
the industrial zone but is surrounded by light industrials and main roads
Bukit Bujang
(3°31’60N,
101°39’0E)
40 km from industrial zone and without an major road or even human activities.
This forest was logged some 50 years ago thus explaining the absence of commercial
tree species. Main species observed here are Instia palembanica and Pterocymbium sp.
Its elevation is 110m above the sea level.
2.2
Sample collection
Sampling was done on a monthly basis over a three year period from 1998 to 2000. pH was determined
in situ during sample collection, after which the samples were immediately stored in a cold box during
transportation. Upon arrival at the laboratory, samples are then filtered and refrigerated until analysis.
Samples of rainwater, throughfall and stemflow were collected at each site. Litter traps were set up and
collected on a monthly basis to account for the amount of leaf litter.
3.0
Chemical analysis
The samples were analysed for cations (NH4+, Na+, Ca2+, Mg2+, K+) using atomic absorption
spectrophotometer while the anions (N03-, S042-, P042-) were analysed by Ion exchange chromatography.
Each analysis was carried out in triplicates to get the mean monthly values. Six species of seeds were
germinated in media wetted with solutions of pH 2.8, 3.6, 4.8, 5.6 and 7.0. The seedling germination was
monitored for 10 days. 20 seedlings were then planted and watered with solutions at pH of 2.8, 3.6,
4.8, 5.6 and 7.0 respectively to determine the growth of the seedlings. These seedlings were
monitored for 6 months and height was measured monthly
4.0
Results and discussion
4.1
Acid precipitation occurrence
The mean annual rainfall pH at Bukit Cerekah and Bukit Bujang in first year was between 5-5.1 and it
gradually dropped to 4.8 in the third year. The trend at Bukit Bujang suggested that the rainfall was
declining towards the acid range as monitoring progressed. There was no clear trend noticed at Bukit
Cerekah. At Bukit Lagong on the other hand, the pH was 5.64 and 5.22 in first and third years
respectively (Fig. 1). The drop in pH indicated that acid precipitation is beginning to make its presence
felt in Bukit Lagong. The drop in mean annual rainfall pH especially at Bukit Lagong was due to the
increase in the incidence of acid precipitation. In the case of Bukit Lagong, noxious gases like NOx and
SO2 have been transported during the wetter seasons from areas like Shah Alam, Sg. Buluh and Kepong.
Both Kepong and Sg. Buluh are known for their cottage and small scales industries while Shah Alam is
the one of the national industrial hub.
4.2
The impact of acid precipitation on foliar leaching and foliar uptake
Acid precipitation exposure may predispose foliage to leaching loss by cuticular erosion, membrane
dysfunction or metabolic abnormality (Smith, 1990). In this case, excessive leaching of K has been
observed. K is an important macro element in plant that helps in maintaining the osmotic potentials of
cells and pH stabilization in cell (Bennett, 1993). It also counteracts the negative charge of inorganic
anions like soi-. Hence, the excessive loss of K may affect the pH balance in cells especially when
sulphate is being taken up as a result of acid precipitation.
4.3
Impact of acid precipitation on leaf litter
A significant correlation was noticed between the leaf litter and rainfall pH. It appeared that the acid
precipitation did increase leaf litter. Chemical analysis for heavy metal in fallen leaves over the sampled
years did not show any specific trends. Except for Pb, there were no clear trends of heavy metal
accumulation in leaf litter. Pb was not detected in the first three years of sampling but in the final year
there was a rapid increase of this element in leaves.
5.
Conclusion
A conclusion can be made that:forest damage due to acid rain was not noticed during the sampling
period. The variation in rain, stemflow and throughfall pH were closely associated with the change in
sulfate and nitrate concentration. However, a rapid rise in total amount of leaf litter was recorded when
the rain pH was within the acidic range.
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