Now considered a priority concern by Chinese environmental agencies, acid rain poses a threat to the environment, ecological systems, forests, and humans, with cost estimates varying from $1-32 U.S. billion (Larssen et al. 2006). China’s relentless economic growth has resulted in increasing sulfur dioxide (SO2)levels (Fig 1) and acid rain in much of the southern provinces (Fig 2).
Acid rain materialized as an issue in China during the 1970s (Dianwu et al. 1988), (Larssen et al. 2006) and persists as a contemporary environmental problem. The acidity stems from the integration of atmospheric moisture with pollutant elements and gases. In this article sulfur dioxide (SO2) will be focused on as an important anthropogenic pollutant responsible for acid rain production in China (Lu et al. 2010), (Tang and Wu, 2012).
Increasing coal combustion and pollutants derived from agriculture, industry and transportation accompanied the exponential economic growth witnessed in China over the latter part of the 20th Century (Larssen et al. 2006). It is likely that the production of these pollutants stimulated acid rain in China (Bhargava and Bhargava 2013). Galloway et al. (1987) support the influential nature of extensive Chinese combustion in facilitating acid rain.
Figure 1, Graph showing the historical evolution of SO2 emissions (Larsson et al. 2006)
Combusting coal releases substantial SO2 into the atmosphere. 69% of China’s energy production came from coal in 2004 (Larssen et al 2006) and this continual consumption of coal subsequently produces high levels of SO2 (Fig 1). Research by Lu et al. (2010) found an SO2 growth rate in China of 7.3% from 2000 to 2006. With high coal consumption yielding high SO2 levels, it is likely that acid rain over the last decade has followed this pattern.
The distribution of acid rain
Figure 2, pH distribution in China, 2012 (Tang and Wu, 2012)
The distribution of acid rain is primarily confined to the southern regions of China (Fig 2). The areas prone to the most acidic rainwater are the Chongqing, Sichuan and Guizhou provinces. These areas and the majority of acid rain areas exist south of the Yangtze River (Tang and Wu, 2012), (Dianqu and Jiling 1988).
As SO2 is a primary contributor to acid rain, the spatial distribution of acid rain shares similarities with the spatial distribution of SO2. However Dianqu and Jiling (1988) outline that cities with high levels of SO2 are not always subject to acid rain, stating that the formation of acid rain cannot solely be dependant on SO2 but on further external factors. Continuing, the south coast of China is densely populated, meaning that a considerable amount of people come into contact with the effects of acid rain.
Impacts and effects
Clearly then, with the increasing nature of both SO2 and acid rain, and the distribution of them, impacts are felt extensively in China.
Numerous environmental impacts have been documented in a paper by Bhargava and Bhargava, (2013), and of note is that acid rain affects every part of an ecosystem. Ecosystems most vulnerable to acid rain are aquatic. Leaching from acid rain creates polluted water, which in turn hinders aquatic flora and fauna in lakes and rivers. Similarly the issue of biomagnification can occur; in which acidic chemicals are passed from organism to organism, multiplying exponentially up through the trophic level system (Bhargava and Bhargava 2013).
Other delicate systems like forests are also sensitive to acid rain. Larssen et al (2006) outline the detrimental effects seen around Chongqing caused by extreme SO2 concentrations in rain and mist (Bian and Yu, 1992). A study of the Chongqing forests by Chuying, (1985), suggested 52-59% biological productivity damage accountable to acid rain.
Limited research makes the effects of soil acidification less certain, however Bhargava and Bhargava (2013) suggest that acid rain disrupts soil chemistry. They theorise that acid rain reacts with soil minerals such as mercury and aluminium creating harmful compounds that plants can absorb; again initiating biomagnification.
Although acid rain is too weak to affect humans directly, the particles intrinsically linked, (i.e. SO2,), are dangerous if inhaled (EPA 2012). Over time, the effects of biomagnification may be seen in humans as contaminants accumulate.
There are a number of measures outlined in the literature (Dianwu and Jiling 1988), (Wang et al. 2000) (Bhargava and Bhargava, 2013) that could be undertaken in order to reduce the effects and the amount of acid rain.
As discussed, China’s combustion of fossil fuels is underpinning its acid rain. The reduction of anthropogenic fossil fuel combustion, implementation of alternative energy sources, and increasing fuel efficiency (Wang et al. 2000) would lessen SO2 emissions.
The development of a more extensive monitoring network (Dianqu and Jiling, 1988) would aid the recording of acid rain distribution, similar to networks seen in Europe and North America (Larssen et al. 2006).
Further research could be carried out into areas of less certain consequence, such as soil acidification and biomagnification effects in humans.
National policies and regulatory schemes for mitigating SO2 (Wang et al. 2000) could aid the reduction of acid rain.
Localized targets are also needed for areas especially susceptible to acid rain.
Acid rain has been a serious environmental problem in recent times, and with development still growing in China, looks to continue to be a contemporary issue.
To mitigate acid rain, the Chinese government must develop and instigate SO2 reduction policies on both national and local spatial scales, implementing further research and monitoring to ensure targets are attained.
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Bian, Y., Yu, S., (1992), Forest Decline in Nanshan, China, Forest ecology management, 51, 53−59.
Chuying. C. ,(1985), Effects of acid rain on Pinus massoniana forests in the region of Chongqing. Presentation to the China-US Workshop on Air Pollution Ecological Effects. Nanjing, China
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Dianwu, Z., and Jiling, X., (1988), Chapter 10 Acidification in Southwestern China, In: Acidification in Tropical Countries, Wiley, pp 317- 345.
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