空氣汙染對都市聲景影響的初步分析

Abstract

近年來全球環境變動日趨劇烈，尤其是人類活動所造成的環境汙染，其中空氣汙染對人類與眾多生物皆有直接與間接的影響，故引起很大的關注。有研究顯示空汙不僅會影響生物呼吸系統的生理作用，如降低肺活量、增加呼吸速率等，導致生物的發聲行為產生變化，同時也會影響生物的時空分布與物種組成，改變一個地點的聲音的多樣性與能量，最終將會反映在聲景(soundscape)的特徵上。然而多數有關空氣汙染和聲景的研究是針對森林大火或沙塵暴等重大特殊事件，評估空氣汙染對聲景的影響，卻甚少探討都市中常見的空氣汙染對聲景的影響。本研究使用空氣品質指標(air quality index, AQI)評估空氣汙染的程度，同時利用亞洲聲景監測網三個測站的聲景資料，計算聲音指數(acoustic indices)量化聲音特徵，首先以spearman's correlation分析聲音指數與AQI之間的關係，並以研究期間之日AQI分別在三個地點中四季的第25百分位數和第75百分位數作為閾值分別篩選出在台中與高雄所發生的空氣汙染不嚴重和嚴重空氣汙染的日子，以Mann-Whitney U test分析汙染嚴重與汙染不嚴重期間指數的差異，探討都市中空汙對聲景的影響。結果顯示大部分在春季、清晨與夜晚群集時空氣汙染對聲景有負面影響，使發聲頻率單一且生物聲音能量降低，環境中生物音的比例降低，而在秋冬季的空氣汙染大部分對聲景有正向影響，顯示發聲頻率多樣且生物聲音能量增強，環境中生物音的占比增加，表示生物的活動、鳴叫方式會受空氣汙染影響而改變。本研究呈現了空氣汙染期間聲景變化的例子，透過聲音的角度來探討空汙不同面向的影響，將能更了解空汙對生物的危害，並提供未來環境影響評估時的參考。In the recent years, global environment has been going through drastic changes, especially the environmental pollution caused by human activities. Among different types of environmental pollution, air pollution has direct and indirect effects on both humans and wildlife as such has attracted a lot of attention. Studies have shown that air pollution not only affects the physiological functions of respiratory systems, such as reducing lung capacity and increasing respiratory rates, but also leads to changes in the vocalization behavior. Furthermore, air pollution also influences the species composition and temporal and spatial distribution of wildlife. These changes may ultimately influence the characteristics of the soundscape. However, most previous studies reported the effect of pollution on soundscape through extreme events such as forest fire or sandstorm, with the effects of air pollution in urban areas on soundscape largely unknown. In this study four acoustic indices from three sites of Asian Soundscape Monitoring Network were used to quantify the characteristics of soundscape. Spearman’s correlation was used to analyze the relationship between the acoustic indices and air quality index (AQI), an indicator of the air pollution level. The 25th and 75th percentiles of the daily AQI during the study period were used to select days with low and high pollution for each of the three locations across four seasons. The Mann-Whitney U test was used to analyze the differences in acoustic indices between low and high AQI pollution days to investigate the impact of urban air pollution on soundscape. Results showed that air pollution reduced frequency diversity, intensity of the sounds produced by non-human organisms (biophony), and the dominance of biophony in soundscape mostly in the spring and mostly for the dawn, dusk and night acoustic communities. However, in autumn and winter, air pollution had opposite effects on soundscape. These results suggest that vocalization patterns and activities of wildlife could be influenced by air pollution. This study illustrates that the effects of air pollution on individuals were ultimately reflected in soundscape. Thus, through analyzing variation of soundscape using acoustic indices, it is possible to explore the effects of air pollution to wildlife and provide a reference for future environmental impact assessments.