交通道路旁茶园多环芳烃的污染特征

Characteristic of polycyclic aromatic hydrocarbons in a roadside tea field

采样分析了某交通道路旁茶园多介质环境中多环芳烃(PAHs)的浓度水平,探讨汽车尾气对茶鲜叶中PAHs的影响.结果表明,茶园空气、土壤和茶组织中16种PAHs的总浓度(∑PAHs)分别为1780.0～4710.0ng/m3、n.d.(未检出)～35.9.0μg/kg和100.00～885.00μg/kg,均随交通道路距离增加而降低,说明汽车尾气对茶园环境造成了PAHs污染.但离交通道路50m和250m处的茶组织中的∑PAHs差异不明显,说明汽车尾气对茶树的PAHs污染主要局限在路旁50m范围内.茶组织中∑PAHs的大小顺序为老叶>须根>嫩叶>生产枝>主根,地上部分大于地下部分.嫩叶中PAHs以3环为主,占∑PAHs的80.6%.老叶中4环比例高于3环,且5～6环的比例显著高于嫩叶.在茶树生长过程中,茶鲜叶会逐渐积累环境中毒性更强的高环PAHs.

Polycyclic aromatic hydrocarbon （PAH） contents in air, soil, and tea plant samples from a roadside tea field were analyzed, and the contribution of traffic exhausts to the PAHs in fresh tea leaves was discussed. Total concentrations of 16 PAHs （∑PAHs） in the air, soil, and tea samples were 1780-4710ng/m^3, n.d.-35.9μg/kg, and 100-885μg/kg, respectively. ∑PAHs decreased with increasing distance from the road curb, implying that traffic exhausts may be the main PAH source to the tea field. However, ∑PAHs of the tea plant at the sampling site or 50 m from the road curb varied little from that of 250 m, indicating that the impact of traffic exhausts on tea PAH contents may be limited in 50 m from the road curb.∑PAHs of the above-ground tea tissues were higher than that of the underground part, with an order of mature leaves 〉 fibrous root 〉 tender leaves 〉 soft shoot 〉 tap root. 80.6% of ∑PAHs in the tender leaves were the 3-ring PAHs. However, 4-ring PAH contents in the mature leaves were higher than the 3-ring ones, and the mature leaves had much higher 5-6 ring PAHs than the tender leaves, suggesting that tea leaves are prone to accumulating high ring PAHs.