【正文】 s most polluted neighborhoods, the annual mean is double that value. Still, these levels are low whenpared to annual means of more than 400 micrograms per cubic meter in Taiyuan and Lanzhou and more than 300 micrograms in Linfeng, Chongqing (Sichuan), and Guiyang (Guizhou). Particulates and sulfur dioxide cause relatively little damage to crops. Most of the yield losses are seen in suburban vegetable farms. They do, however, inflict considerably greater damage on materials, above all to buildings and corrodible surfaces. As acid deposition intensifies in the rainy South, the amount of this kind 西安航空學(xué)院畢業(yè)設(shè)計（論文） 43 of damage will only number of worrisome human health risks are also associated with this kind of pollution. At least 200 million Chinese are exposed to annual particulate concentrations of more than 300 micrograms per cubic meter。 西安航空學(xué)院畢業(yè)設(shè)計（論文） 41 detailed assumptions are urged to refer to them specifically. Air and Water Pollution A small pioneering opinion survey published in China in 1994 uncovered some interesting facts. First, the public ranked air and water pollution second only to earthquakes and floods when asked to list environmental hazards. Respondents with science or engineering degrees, however, put the two pollution risks ahead of natural 39。s ecosystems, I began work on a more prehensive evaluation in this assessment was being pleted, a group of Chinese researchers began a similarly prehensive independent evaluation. Having both of these studies available creates an unparalleled opportunity to appraise the economic impact of environmental change in China. The following discussion will review some of the country39。s official government 西安航空學(xué)院畢業(yè)設(shè)計（論文） 40 agencies are filled with masses of uncooperative bureaucrats prone to treat any unflattering figure as a state secret. Dubious statistics and unverifiable claims also abound. It seems to be one thing for the Dutch or Germans to assign a cost to environmental degradation in their countries and another thing entirely for the Chinese to do so. That said, the Chinese actually did some of the earliest studies. One, begun in 1984 and published in 1990, estimated the cost of pollution to be about percent of the nation39。s population grows by at least 13 million each year. This is the equivalent of adding the population of France in less than five years. During the 1980s, China39。t these figures been developed? First, there are (as yet) no generally accepted procedures for conducting such methodological uncertainties leave individual researchers with no choice but to use subjective judgments when deciding which variables to include and how to treat them. 西安航空學(xué)院畢業(yè)設(shè)計（論文） 37 Suppose, for example, researchers wanted to quantify the health effects of chronically high levels of urban air pollution. They could take the more minimalist approach, limiting the analysisto the value of the labor time lost due to higher they could attempt a more allenpassing evaluation that would put a price on every individual disfort and include the cost of premature death. As these researchers would quickly discover, the former approach is much easier than the latter. While a rich and fascinating literature on the price of personal suffering and the value of life does exist, objective criteria for putting a moary value on respiratory disfort, physical limitations, and anxiety induced by asthma attacks do not. As far as the value of life is concerned, actuarial practices, economic considerations, and moral imperatives offer estimates that may differ widely sometimes by up to an order of magnitude. Having a standard set of procedures would not really simplify the task, however. The basic problem is that the kinds of specific figures required as basic inputs in such calculations are typically unavailable even in affluent countries, which have long had good statistical makes it impossible for researchers to 西安航空學(xué)院畢業(yè)設(shè)計（論文） 38 avoid making subjective choices and simplifying assumptions, even though this weakens the persuasiveness of the eventual bottom line. As it is, the cumulative effect of even small departures from reality can easily halve or double a final figure. The second and perhaps most significant obstacle is the impossibility of putting a meaningful price on lost or reduced environmental services. For example, suppose a peasant living on a treeless plain takes straw from a field to light a fire to cook a meal. How can the loss of that straw be valued? The loss of the plant nutrients in the straw could be expressed rather easily by equating it with the cost of the synthetic fertilizers needed to replace those nutrients. But the straw also improved the soil39。 Hennessy J L. Computer anization and design: The hardware/software interface. 2nd Edition, San Francisco: Man Kaufmann, 1994 [15]Carreira J, Madeira H and Silva J G. Xception: A technique for the experimental evaluation of dependability in modern puters. IEEE Transactions on Software Engineering, 1998, 24(2): 125136 [16]Koopman P and DeVale K. Comparing the robustness of POSIX operating systems. In: Proceedings of the IEEE 29th International Symposium on FaultTolerant Computing, Madison, IEEE CS Press, June 1999, pp. 3037 西安航空學(xué)院畢業(yè)設(shè)計（論文） 36 外文翻譯 China shoulders the cost of environmental change（摘譯） Ecologists today have at their disposal a great deal of evidence about the processes that degrade our environment, ranging from coastal eutrophication to tropical deforestation. They have e to understand the intricacies of humaninduced changes such as acid deposition and heavy metal accumulation. But they do not have realistic assessments of the economic losses that result from environmental pollution and ecosystem degradation. Possession of these kinds of numbers