http://www.chemsoc.org/chembytes/ezine/2001/bashkin_jun01.htm A rain check on Asia Without better methods for monitoring and controlling the effects of acid rain, the environmental consequences for East Asia could be devastating, warn Vladimir Bashkin and Miroslav Radojevic In the 1960s Scandinavian scientists began to link the mysterious disappearance of fish from lakes and streams to wind-blown pollution from the UK and central Europe. By the early 1980s widespread environmental devastation throughout Europe and the US was blamed on acid rain (Box 1). The death of fish in thousands of lakes, forest decline and damage to historical monuments are among the most well publicised examples. Although first recognised as a regional problem in Europe and the US,1 over the past 10 years acid rain has been observed at sites throughout the world, from the polar ice caps to the tropical rainforests of Asia, Africa and South America. Within just a single generation, acid rain has grown from being a local and regional nuisance to a major global problem. More recently, alarm has been expressed about increasing levels of acidification in East Asia.2-4 Approximately one-third of the world's population resides in East Asia and the region has been experiencing phenomenal economic growth over the past two decades. The rapid growth of industrial and agricultural production, especially in China, India, Thailand, and Indonesia, has resulted in a remarkable increase in SO2 and NOx emissions during the past decade, and these emissions look set to grow further. Although emissions of these pollutants are lower than in Europe and the US on a per capita basis, experts predict that total emissions in East Asia will surpass the combined emissions of Europe and the US by the year 2020. The main reasons for the increasing pollution are the low quality of fuel in most of East Asia (the S content can be as high as 7 per cent in Thai lignite and up to 5 per cent in Chinese brown coal) and the absence of control technologies in many countries. There is concern that these increasing emissions will cause enormous environmental damage, with some impacts already apparent. Governments throughout the region are starting to treat the problem with growing urgency, and in China abatement of acid rain is now considered a top government priority. Monitoring acidity Acid rain monitoring networks provide information required by policymakers to make sound abatement decisions. Although networks are well established in Europe and the US, rainwater monitoring in East Asia is still in its infancy and the few existing national networks do not yet give a clear picture of acid deposition in the region.2 While some rainwater monitoring stations in East Asia participate in the Global Atmosphere Watch (GAW) of the World Meteorological Organisation (WMO), these are few and far between. A recent review of acid rain monitoring networks in East Asia indicates that these vary considerably between countries, from being relatively sophisticated, through rudimentary, to non-existent.2 Studies of rainwater composition were first reported in Japan in 1894, and today Japan has the most advanced acid rain monitoring and abatement programme in the region. The Japan Environment Agency (JEA) has been monitoring acid rain since the early 1970s. In 1983 this agency established the National Acid Deposition Monitoring Network, which samples rainwater at 48 sites throughout the country, together with routine analysis of surface waters and soils. In China, the Institute of Environmental Chemistry initiated a rainwater survey in the late 1970s, and nationwide surveys have been carried out since 1982. Measurements in 82 Chinese cities from 1991 to 1995 showed the occurrence of acid rain, with average annual pHs <5.6, in nearly half of the cities. Southern cities were the worst affected: 87 per cent of cities south of Qingling Mountain and Huaihe River were affected by acid rain and the lowest pH value was 3.52 in Changsha, Hunan province. The chemical composition of rainwater in China is different from that in Europe; rainwater in China has lower pH values and higher sulfate, calcium and ammonium concentrations. Furthermore, the concentration of calcium relative to sulfate is very high in China while nitrate concentrations are low relative to other components. Rainwater has been routinely monitored at 14 sites throughout Malaysia since 1985 as part of the National Acid Rain Monitoring Network, and a rainwater monitoring station was set up in Brunei in 1995 by the Brunei Meteorological Service. South Korea, Taiwan and Hong Kong also have well developed rainwater monitoring networks. In Taiwan, approximately 70 per cent of rainfall is considered to be acidic, with pH values <5.6. Although rainwater composition has been intermittently determined in Singapore, Indonesia, the Philippines, Thailand and Vietnam, monitoring in these countries has been neither systematic nor comprehensive and the existing programmes are far from satisfactory. On the other hand, rainwater monitoring in Laos, Cambodia and Myanmar is virtually non-existent, due mainly to a lack of adequate resources and technical expertise. More than 50 per cent of rain events monitored in East Asia have pHs <5.0. For meaningful comparisons to be made between measurements at different sites and for effective policy decisions to be taken, there is an urgent need for a regional rainwater monitoring network in East Asia. The JEA has been advocating such a monitoring network for some time, and has proposed a uniform rainwater sampling and analysis protocol to be adhered to by all participating stations. However, JEA's proposed sampling and analysis protocol, which is remarkably similar to that of the WMO's GAW programme, suffers from several shortcomings. For example, weak organic acids such as methanoic and ethanoic acids are not determined. Also, effective measures (eg the use of biocides) are not taken to reduce biological and chemical activity in collected samples. Biochemical processes - eg degradation of organic acids - could alter rainwater composition, resulting in unrepresentative measurements. Damaging effects Extensive environmental devastation by acid rain, such as that previously observed in Europe and the US, is still not apparent in East Asia. Nevertheless, some of the expected impacts are starting to be seen. There are several reports of damage to trees, crops and materials in areas of China seriously affected by acid rain. For example, 87 per cent of cedar trees on Omei Mountain, Sichuan Province, have suffered damage from acid deposition. However, the extent to which acid rain contributes to these problems is uncertain. In Japan, long-term records in some mountainous lakes show decreases in pH and there is evidence of damage to trees, but again the contribution of acid rain to the reported effects is unclear. Increasing concern is being expressed about the potential impacts of acid rain and air pollution on many historical monuments in the region; the case of the Taj Mahal in India is well known. Recently, Unesco initiated a programme to document and monitor damage to historical monuments in Asia. Expert studies suggest that environmental damage will become more widespread and severe if the growth in pollutant emissions continues unabated. Already, 28 per cent of Chinese territory is affected by acid rain, and it has been estimated that acid rain damage to crops and forests alone costs China some $4900m (ca �2900m) each year. The area affected by acid rain has extended northwards from south of the Yangtze River in 1986 to the whole of east China at present. The concept of critical loads is increasingly being used to assess potential damage by acid rain throughout the world, including East Asia.2 A critical load (CL) is the threshold level of a pollutant at which harmful effects begin to be observed (Box 2). The applicability of critical load methodology for determining the sensitivity of natural terrestrial ecosystems to S acidity loading can be illustrated by using South Korea as an example. According to S deposition patterns, CL(S) was exceeded in roughly 40 per cent of all Korean ecosystems (mainly in the southeast of the country) during 1994-97. Chinese ecosystem sensitivity to acid deposition was assessed on the basis of the mineralogy controlling weathering and soil development, and taking into account the effects of temperature, soil texture, land use and precipitation. The results show that the podzolic soil zone in the Northeast is the most sensitive area to acid deposition, followed by latosol (found in wet subtropical and tropical forests), dark brown forest soil, and black soil zones. Different regional soil sensitivities to acid deposition can be attributed to differences in temperature, humidity and soil texture. Sulfur deposition exceeds CLmaxS values in 25 per cent of the total country area. In Japan, models have been developed to evaluate soil acidification and ecosystem sensitivity to acid deposition. A dynamic model takes into consideration rapid chemical reactions, eg chemical weathering, nutrient uptake and nitrification. Applying this to an area on the island of Yakushima, a world natural heritage site, shows that more than 90 per cent of the Ca in the soil has been depleted due to acidification. The Rains-Asia impact model was used to assess ecosystem sensitivity to acid deposition and to calculate CL(S) for six forest ecosystems in Taiwan. The results indicate that forest ecosystems in Taiwan are very sensitive to acid deposition because of the low soil pH (<5.5). Lowland subtropical forest ecosystems in Taiwan were found to have low or moderately low CL(S), suggesting that they are vulnerable to acid deposition. Yet, many forest ecosystems are exposed to acid deposition far exceeding their critical loads. Although these forest ecosystems appear healthy, sudden detrimental change may occur once the current buffering capacity is depleted. Cation leaching, both from the forest canopy and from forest soils, has been observed in some forest ecosystems in Taiwan. Continuous exposure to high levels of acid deposition can lead to nutrient imbalance in the forests and thereby undermine forest health. Surface waters are the most sensitive ecosystems in East Asia. The natural pH of surface waters is between 6.5 and 8.5 depending on the type of water body, underlying geological rocks, water trophic levels, food webs and so on. At pHs <6.0 undesirable changes in biodiversity and even death of many aquatic species can result. Below about pH 4.0 lakes become a suitable habitat for white moss, which prefers an acidic environment. The moss forms a 'felt mat' on the lake bottom that may grow to a thickness of 0.5m or more. The mat prevents the exchange of nutrients between the water and the bottom sediments and it also prevents the sediments from exerting any buffering action. The resultant lake waters are crystal clear but support very few life forms. The pHs of various regions of East Asia are comparable with the threshold pHs in Table 1, below which several species of fish die. For instance, in Lake Osorezan, Japan, the water has an annual average pH3.4-3.8. The pH of the water in the Sawanoike artificial reservoir, Japan, is 5.5. Similar measurements in China indicate that 52 per cent of the surface water in Guangdong province is affected by acid deposition. Table 1. pH and the survival of aquatic organisms -------------------------------------------------------------------------------- Surface water pH Aquatic organism 6.0 Death of snails and crustaceans 5.5 Death of salmon, rainbow trout and whitefish 5.0 Death of perch and pike 4.5 Death of eel and brook trout Controlling acid rain Japan has long been a world leader in air pollution legislation and abatement technologies. Methods of flue gas desulfurisation (FGD) and flue gas denitrification were first implemented at Japanese power stations as long ago as the early 1960s and 1970s, respectively. By the early 1990s more than 2000 industrial units were equipped with FGD technology and nearly 1000 units had denitrification systems installed. Further, Japan has had more stringent vehicle emission standards than the US and was the first country to mass produce low emission motor vehicles in the 1970s. China is currently undertaking a massive air pollution control programme that involves fitting FGD equipment to major industrial plants; so far more than 300 plants have been equipped with FGD scrubbers. The Chinese government needs more than $50,000m (ca �30,000m) to finance its environmental protection programme and it has already earmarked $21,700m (ca �14,000m) for environmental pollution control. Air pollution control technologies have also been implemented in Korea, Taiwan, Hong Kong and Singapore, but in many countries legislation and control technologies are either inadequate or non-existent. Malaysia and Indonesia have also started introducing control technologies at some plants, as has Thailand. In addition, in many countries catalytic converters are required in new vehicles. As we have already seen, however, though many countries have enacted air quality and emission standards, some do not have adequate air quality and acid rain monitoring networks. Legislation is ineffective without appropriate monitoring. Pollutant emissions from one country can affect receptors across borders and there is an urgent need to expand the UN ECE Convention on Long-Range Transboundary Air Pollution to the entire Eurasian super-continent. This commits signatories to reduce SO2 emissions up to and beyond 2005 (see Box 2). So far, there has been very little cooperation between governments in East Asia regarding the transboundary transport of acidic pollution or its abatement, and the initiative has come mainly from scientists. As previously mentioned that transboundary pollution can be significant is apparent from the haze problem, which is a major issue in Southeast Asia; air pollution from forest fires in Indonesia can spread over several million km2 and affect several countries during the burning season.5 Transport of acidic pollution from China and Korea to Japan is also well documented. The future In view of the volatile economic situation in the region it is difficult to make reliable predictions regarding the extent of acid rain and associated air pollution problems in the future. If sufficient funds are made available to implement the required pollution control technologies and policies then we may expect the problem to be effectively controlled, if not eliminated. Furthermore, reduction of effects is not linearly related to a reduction in emissions because of the complexity of the relevant impact processes. Economic growth, accompanied by increasing prosperity, would ensure that sufficient funds are available for pollution control. Economic downturn may not necessarily result in reduced emissions; it may lead to fewer, but more polluting, industries as less financial resources are available for implementing pollution control measures. In any case, international cooperation between industrialised nations, which have a longer history of successful air pollution management, and developing countries in East Asia on all aspects of the acid rain problem is to be encouraged. Technology transfer, sharing of information, collaborative research, and financial assistance by industrialised nations would greatly speed up the process of environmental recovery in East Asia. Vladimir N. Bashkin is a professor in environmental chemistry at the Joint Graduate School of Energy and Environment, King Mongkut's University of Technology Thonburi, Bangkok, 10140 Thailand, e-mail: [EMAIL PROTECTED]; Miroslav Radojevic is a senior lecturer at the department of chemistry, University of Brunei Darussalam, Tungku Link, BE 1410, Brunei Darussalam; e-mail: [EMAIL PROTECTED] References M. Radojevic and R. M. Harrison (eds), Atmospheric acidity: sources, consequences and abatement. London: Elsevier Applied Science, 1992. V. Bashkin and S.-U. Park (eds), Acid deposition and ecosystem sensitivity in East Asia. New York: Nova Science, 1998. Proceedings of the fifth joint seminar on regional deposition processes in the atmosphere. Department of Atmospheric Sciences, Seoul National University: Korea, October 1999. Acid rain 2000. Sixth international conference on acidic deposition. Dordrecht: Kluwer Academic, 2000. M. Radojevic, Chem. Br., December 1998, p38. M. Radojevic and V. N. Bashkin, Practical environmental analysis. Cambridge: RSC, 1999. M. Radojevic and K. S. Tan, Atmos. Environ., 2000, 34, 2739. V. Bashkin and M. Kozlov, Biogeochemistry, 1999, 47, 147. --------------------------------------------------------------------- Mulai langganan: kirim e-mail ke [EMAIL PROTECTED] Stop langganan: kirim e-mail ke [EMAIL PROTECTED] Archive ada di http://www.mail-archive.com/[email protected]
