氣候變遷下台灣地區近地表臭氧對農作物潛在的影響

The potential impact of surface ozone on crops due to climate change in Taiwan

許莉詩(Li-Shih Hsu)

指導教授 ： 陳正平

共同指導教授 ： 蔡宜君(I-Chun Tsai)

國立臺灣大學/理學院/氣候變遷與永續發展國際學位學程/碩士(2021年)

https://doi.org/10.6342/NTU202100536

摘要

臭氧為重要的空氣污染物和強氧化劑，它由葉片氣孔進入損害植物細胞，導致農作物減產。臭氧由前驅物經複雜光化學反應下產生，並受氣象條件的調節，因此近地表臭氧被認為是最難管制的空氣污染物之一。本研究旨在研究近地表臭氧對台灣作物的產量及其未來影響。本研究在人為排放固定的情境下，使用WRF和CMAQ模式模擬台灣區域的臭氧時空分佈，估算氣候變化下臭氧的潛在風險；CMIP5耦合模式的平均值用於氣象參數模擬所需的邊界條件。
模擬的臭氧值轉換為濃度指數AOT40（累積白天臭氧濃度每小時平均超過40 ppb），以及植物氣孔吸收毒性臭氧的劑量（POD），並疊加實際土地利用資料，來量化農作物產量受臭氧影響之變化。在目前氣候情境下，AOT40於臭氧的產量損失佔相對產量（relative yield, RY）的5.26％；其中西瓜的產量損失最為顯著11.4％，馬鈴薯產量損失最低為0.16％。水稻在第一季（3至5月）的相對產量損失為6.04％，第二季（6至8月）的相對產量損失為5.01%小麥，馬鈴薯，番茄的POD（AOT40）產量損失分別為18.2％（8.64％），5.3％（1.05％）和26.4％（6.15％）。兩項指數顯示出可比的時空分布，特別是台灣西部的內陸區域，春秋兩季的相對產量(RY)顯著減少。在目前氣候條件下，AOT40和POD得出的相對產量(RY)差異達-30％至-2％。未來氣候變遷的情境則顯示，西部平原的臭氧濃度顯著增加約4 ppb，而東部地區則保持相對不變。POD和AOT40估算目前和未來氣候之間的相對產量(RY)差異分別為-1.7％和-9.6％，其中未來的臭氧濃度主導了植物的反應，同時氣象因子也造成農作物相對產量的略降。

關鍵字

氣候變遷 ； 臭氧 ； 作物產量 ； AOT40 ； PODY ； PGW ； 風險評估

並列摘要

Ozone is a major air pollutant and powerful oxidant; it can cause significant damages to plants by entering leaf stomata and eventually lead to a crop-yield reduction. With the complicated photochemical reactions involving precursors and modulated by meteorological conditions, surface ozone is regarded as one of the most challenging air pollutants to regulate. This study aims to study the regional impacts of surface ozone on Taiwan's cash crops and its future projection. To estimate the potential risk of ozone exposure under climate change, we simulated the spatial-temporal distribution of ozone around Taiwan by using the Weather Research and Forecasting (WRF) model and the Community Multiscale Air Quality Modeling System (CMAQ) model for current and future climate scenarios with fixed emissions. The ensemble mean of CMIP5 models is used to represent changes in meteorological parameters due to global warming for the boundary conditions.
To estimate the potential risk to crops, the simulated ozone fields are converted to the concentration-based index called AOT40 (accumulated the hourly mean ozone concentration over a threshold of 40 ppb during daylight hours) and the metrics of stomatal uptake by the accumulated phytotoxic ozone dose (POD) for the growing season. These indices are further overlaid with land-use information to quantify changes in crop yield between current and future conditions. The mean yield loss by ozone exposure in AOT40 accounted for 5.26% of the relative yield (RY) in current climate run, and the most significant relative yield losses was 11.4% for watermelon and the slightest is 0.16% for potato; rice had relative yield losses 6.04% in first rice season (March, April, May) and 5.01 RY lossess in second rice season (June, July, August). The average estimated POD (AOT40) relative yield loss of wheat, potato, tomato was 18.2% (8.64%), 5.3% (1.05%) and 26.4% (6.15%), respectively. Both metrics showed comparable spatial and temporal patterns, where significant RY reduction occurred in western Taiwan, especially the inland plain areas in spring and fall. Under current climate conditions, the discrepancy between AOT40 and POD crop RY ranged from -30% to -2%. The pseudo global warming scenario suggests a significant increase in ozone over the western plain areas by about 4 ppb, while the eastern regions remain relatively unchanged. The RY differences between current and future climate estimated with POD and AOT40 were -1.7% and -9.6%, respectively, with future O3 dominated the plant response while future meteorological factors also contributed a slight decrease.

並列關鍵字

ozone ； crop yield ； AOT40 ； PODY ； climate change ； pseudo warming method ； risk assessment

參考文獻

Agathokleous, E., Kitao, M., Kinose, Y. (2018). A Review Study on Ozone Phytotoxicity Metrics for Setting Critical Levels in Asia. Asian Journal of Atmospheric Environment (AJAE), 12(1).

Akimoto, H. (2003). Global air quality and pollution. Science, 302(5651), 1716-1719.

Anav, A., De Marco, A., Friedlingstein, P., Savi, F., Sicard, P., Sitch, S., . . . Paoletti, E. (2019). Growing season extension affects ozone uptake by European forests. Science of The Total Environment, 669, 1043-1052.

Anav, A., De Marco, A., Proietti, C., Alessandri, A., Dell'Aquila, A., Cionni, I., . . . Paoletti, E. (2016). Comparing concentration‐based (AOT40) and stomatal uptake (PODY) metrics for ozone risk assessment to European forests. Global Change Biology, 22(4), 1608-1627.

Ashmore, M. (2005). Assessing the future global impacts of ozone on vegetation. Plant, Cell Environment, 28(8), 949-964.