Sandstorms an enviromental risk

By Liou Ming-lone and Liu Chung-ming 劉銘龍、柳中明, Taipei Times, Friday 20 April 2001, Page 12

Last week, a sandstorm from China had a serious impact on Taiwan’s air quality. The threat to Taiwan’s air quality from China’s sandstorms will remain until late May. During this period, every time a cold air mass from China moves south and the cold front at its leading edge passes over Taiwan, what follows the rains may be a large blanket of sand moving south in the atmosphere. Since last spring, China’s sandstorms have repeatedly affected Taiwan’s air quality and such incidents will only become more frequent given the trends in global climate change.

According to statistics from the Chinese Academy of Sciences, the number of strong and very strong sandstorms increased from five in the 1950s to eight in the 1960s, to 10 in the 1970s, 14 in the 1980s and 17 in the 1990s. By last spring, how-ever, 12 sandstorms had already occurred since the previous year, and in most areas of north and northwest China, the number of sandstorms and the number of days with high levels of sand in the atmosphere were both above average. Especially in Beijing and Tianjin, the number of days with high levels of sand in the atmosphere was the greatest since 1988 and 1985 respectively.

The cause of the problem was that during the winter of 1999, frequent strong cold fronts, accompanied by high winds, struck north China. In addition, last spring temperatures increased significantly in northern China and the eastern part of northwest China while at the same time there was very little rainfall. Before a blanket of grass had time to form, the arrival of each big wind caused huge areas of thawed surface-level soil to become dry and loose, triggering more sandy, dusty weather.

In the first month of this year, three sandstorms in a row struck Gansu Province, in the corridor west of the Yellow River. The sandstorm that occurred from Dec. 31, 2000 to Jan. 2, 2001 was the earliest sandstorm in recent decades. Since then, sandstorms have occurred every month. They originate from Inner Mongolia or in the northwest and seem to occur increasingly frequently at shorter intervals and with greater intensity than before.

The storm that started on April 7 began in a sandy area of Inner Mongolia. By April 9, it had already spread to the deserts of Xinjiang Province. It had also spread south of the Yellow River and settled to earth east of the Yellow Sea. The first wave began to influence the air quality in Taiwan in the early morning hours of April 12, and it continued through April 13 and 14. The scale and sustained intensity of this storm were truly surprising.

This sandstorm also attracted the attention of scientific re-search units in the US, Japan, South Korea, Russia and France. They each conducted in-depth analysis and research by means of remote satellite and laser measurements, aerial surveys, weather station sampling surveys and mathematical forecasting models.

Under the influence of global warming, although interior, mid-latitude regions of the Northern hemisphere have experienced no major changes in precipitation, they have seen a clear rise in temperature, an increase in surface evaporation, and aridization of the land. These factors all contribute to a climatic background favorable to the production of sandstorms. In addition, China continues with its pursuit of a high-growth economy, despite being powerless to stop the over-extension its land resources. The degradation and reduction of grasslands in northwest China is going to be difficult to reverse. The future does not give cause for much optimism.

Thus, given the trend of global climatic change, sandstorms will occur in China with increasing frequency. The really worrying question is, besides all the yellow dust brought by the air currents, what other kind of matter will be deposited by the storms? What kind of physical (suspended particles, etc), chemical (acid rain, nitrogen oxide, etc), and biological (bacteria, fungi, etc) characteristics will it have? How might the sandstorms affect the quality of Taiwan’s air, rivers and ecological systems? How will they affect Taiwan’s environment, as well as the health of its people?

The government needs to face these questions pro-actively and ensure that they are researched in depth.