tailieunhanh - ECOTOXICOLOGY: A Comprehensive Treatment - Chapter 26

Một vài thập kỷ trước đây, mối quan tâm của chúng tôi về các chất gây ô nhiễm không khí chủ yếu giới hạn trong những người liên quan đến quá trình đốt cháy nhiên liệu hóa thạch (ví dụ, SO2, NOx, H +). Trong khi đốt cháy nhiên liệu hóa thạch vẫn được coi là một nguồn quan trọng cho nhiều chất gây ô nhiễm không khí, định nghĩa hiện đại của chúng ta về các chất gây ô nhiễm khí quyển đã mở rộng đáng kể. Bây giờ chúng ta nhận ra rằng những căng thẳng trên toàn. | 26 Community Responses to Global and Atmospheric Stressors INTRODUCTION Several decades ago our concerns about atmospheric pollutants were primarily limited to those associated with the combustion of fossil fuels . SO2 NOX H . While fossil fuel combustion is still regarded as a major source for many atmospheric pollutants our contemporary definition of atmospheric pollutants has broadened considerably. We now recognize that many stressors are globally distributed Table and that the temporal scale of effects ranges from days to centuries. Today we have serious concerns not only about the direct effects of atmospheric pollutants such as CH4 and CO2 but also their indirect effects on global climate. In addition persistent organic pollutants POPs once regarded as a local problem primarily associated with industrial and agricultural discharges are now globally distributed and occur in very remote environments such as the Canadian arctic. We now understand that not only is ozone O3 a serious atmospheric stressor for many plants but that loss of stratospheric ozone owing to release of chlorofluorocarbons CFCs has significantly increased levels of ultraviolet radiation UVR striking the earth s surface over the past 20 years. Effects of atmospheric stressors on communities are likely to be complex interactive and difficult to predict. The regional and global distribution of atmospheric pollutants presents unique challenges for study design and interpretation. Long-range transport of some atmospheric pollutants . SO2 NO_f and geographic variation in exposure to other stressors . UV-B radiation complicate assessment of effects. Researchers are often forced to extrapolate results of relatively small-scale and short duration studies to much larger spatiotemporal scales. Some communities particularly those characterized by long-lived species . forests will respond very slowly to atmospheric stressors. Because long-term data from these systems are often .