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Studies on the accumulation of polycyclic aromatic hydrocarbons (PAHs) in plant leaves and the techniques for biomonitoring
|關鍵字:||polycyclic aromatic hydrocarbons;多環芳香族碳氫化合物;accumulation;biomonitoring;Bidens pilosa L. var. radiata;air pollution;累積;生物監測;大花咸豐草;空氣污染||出版社:||生命科學系||摘要:||
多環芳香族碳氫化合物(polycyclic aromatic hydrocarbons, PAHs) 在環境中普遍存在，是有機物或塑膠品燃燒不完全之副產物，垃圾焚燒、引擎操作、工廠運作及家庭取暖皆是PAHs之重要來源。多種PAHs具致變性或致癌性，因而引起關切。PAHs具持久性，為脂溶性，會累積於植物體。台灣地區有關大氣中PAHs對植物之影響以及植物對PAHs之吸收與累積之相關研究很少。本研究之目的有四：(1)建立植物體及空氣中PAHs之分析方法；(2)監測不同污染源周邊植物之PAHs累積情形；(3)由植物葉片之PAHs累積評估PAHs污染範圍；(4)篩選出適合的植物種類作為監測指標，監測環境中PAHs之污染情形。
植體中PAHs之萃取及分析是研究PAHs累積之首要步驟，本研究建立同時檢測植物葉片中16種PAHs（naphthalene、acenaphylene、acenaphthene、fluorine、phenanthrene 、anthracene、fluoranthene、pyrene、benzoanthracene、chrysene、benzo(b)fluoranthene、benzo(k)fluoranthene、benzo(a)pyrene、dibenzoanthracene、benzoperylene 及 indenopyrene）之分析方法。先以二氯甲烷萃取葉片，萃取液經氧化鋁分離管柱淨化，以高效液態層析儀(HPLC)附紫外光或螢光檢測器進行定量分析。16種PAHs化合物標準檢量線之相關係數(R2)在0.9950－0.9999間。本方法可適用於11種測試植物葉片16種PAHs含量之檢測，偵測界限為1.27 - 8.21 ng g-1。
雲林縣元長工業區一塑膠廢棄物處理廠在2002年12月7日發生大火，本研究藉以探討火災造成PAHs污染植物之情況。火災後採集廠區周邊11個樣區之植物葉片(檬果、構樹、大花咸豐草及玉米)，檢測其PAHs累積量，亦評估其作為被動生物監測之可應用性。葉片PAHs累積總量，大花咸豐草高於檬果與構樹；樣點SW4(工廠西南方400m)之大花咸豐草、檬果及構樹PAHs總量分別為2221.9、 940.3 及1158.0 ng g-1 f.w.。植物葉片PAHs含量隨著與火災現場之距離增加而減少，樣點S1(工廠南方30m)之檬果葉片PAHs累積總量(2933.3 ng g-1 f.w) 為樣點SW4(工廠西南方400m)累積總量(940.2 ng g-1 f.w)之3.1倍，其中anthracene (3-環)含量差異最大，樣點S1(381.0 ng g-1 f.w)為樣點SW4(65.0 ng g-1 f.w)之5.9倍。本研究發現塑膠廢棄物大火引發PAHs污染之影響範圍約為700 m。植物葉片PAHs含量會隨時間而遞減。大花咸豐草、檬果及構樹可多量累積PAHs之特性，在本區域可作為火災後大氣PAHs污染程度與範圍之被動監測植物。大花咸豐草是台灣極普遍之菊科野草，對PAHs污染具耐性，尤適合作為台灣地區PAHs污染之監測植物。
Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in the environment. PAHs are by-products of the incomplete combustion or pyrolysis of organic materials or plastics. Incineration, internal combustion engines, industrial activities and residential heating all are important sources of PAHs. PAHs are a major health concern because many kinds of PAHs are carcinogenic and mutagenic. PAHs persist in the environment and may accumulate in vegetation. In Taiwan, there were only few studies concerning the effects of PAHs on plants as well as the uptake and accumulation of PAHs in plants. Four items were studied in this research, including: (1) to set up the adequate analytical method of PAHs in vegetation and in air; (2) to investigate the accumulation of PAHs in plants in the vicinity of different pollution sources; (3) to evaluate the scale of polluted area from pollution source by the PAHs accumulation in plants; (4) to choose the suitable plant species as indicators for active or passive biomonitoring PAHs in the environment.
The extraction and analysis of PAHs from plant tissues are essential steps for determining PAHs accumulation. This study developed a precise method for simultaneous detecting 16 PAHs by high performance liquid chromatography (HPLC) with fluorescence or UV detector. Leaf samples were extracted with dichloromethane solvent. The extract was then cleaned up by aluminum oxide column before being subjected to HPLC analysis. The correlation coefficients of calibration curve of 16 PAHs were 0.9950 - 0.9999. For the 11 tested plant species, all the 16 PAHs contents in leaves could be simultaneously determined by this developed method. The detection limits of 16PAHs were 1.27 - 8.21 ng g-1.
Among the 94 leaf samples from different sites in the vicinities of pollution sources, 18 samples were detected with PAHs contents. That implied that PAHs accumulation was found in the plants in the polluted areas in Taiwan. Bidens pilosa var. radiata accumulated higher levels of PAHs than the other species. Kinds of PAHs in leaves varied with pollution sources. Phenanthrene and pyrene were detected in leaves of B. pilosa var. radiata from the vicinity of incinerator. Phenanthrene, fluoranthene, pyrene and chrysene were detected in B. pilosa var. radiata from the industrial area.
An opportunity arose to examine the factors that govern the dispersion of PAHs following a massive waste plastic fire at Yunlin, central Taiwan, on Dec. 7 of 2002. With the aim of investigating the applicability of biomonitoring for PAHs contamination, leaves of Mangifera indica, Broussonetia papyrifera and B. pilosa var. radiata were collected from 11 sites in the vicinity of the burned warehouse after the large-scale waste plastic fire, and were analyzed for 16 PAHs. B. pilosa var. radiata leaves contained higher PAHs than M. indica and B. papyrifera. The concentration of ΣPAHs in leaves of B. pilosa var. radiata, M. indica and B. papyrifera on site SW4 (400m southwest from the warehouse) was 2221.9, 940.3 and 1158.0 ng g-1 f.w., respectively. The levels of ΣPAHs in leaves declined as the distance from the burned warehouse increased. The zone of contamination was estimated to be less than 700m from this plastic fire. The concentrations of PAHs in leaves declined rapidly with time. B. pilosa var. radiata, M. indica and B. papyrifera accumulated high levels of PAHs and could be used as passive biomonitors to evaluate gradient of atmospheric PAHs contamination after a plastic fire. B. pilosa var. radiata, that is one kind of widespread naturalized vegetation and is relatively tolerant to PAH pollution, is a suitable species in Taiwan for monitoring PAHs pollution through leaf analyses.
B. pilosa var. radiata accumulated higher level of PAHs than the other species both in the vicinity of incinerators and after a plastic fire. It showed no injured symptoms. In this study, B. pilosa var. radiata were studied for active and passive biomonitorings. The concentrations of 3- and 4-ring PAHs (phenanthrene, pyrene and chrysene), instead of 5- and 6-ring PAHs, were detected among all the B. pilosa var. radiata samples in the vicinity of incinerator. The concentrations of PAHs increased with time in active biomonitoring. The accumulation of PAH in B. pilosa var. radiata yielded useful information on the deposition of PAH and was a good indicator of pollution. B. pilosa var. radiata can be easily cultivated and widespread installed in the vicinity of pollution source and is suitable to be used as accumulator for active biomonitoring of PAHs pollution.
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