中国环境科学2008,28(7)：577~581ChinaEnvironmentalScience交通道路旁茶园多环芳烃的污染特征林道辉,朱利中(浙江大学环境科学系,浙江杭州310028)摘要：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.关键词：茶叶；汽车尾气；多环芳烃；源解析中图分类号：X51文献标识码：A文章编号：1000-6932(2008)07-0577-05Characteristicofpolycyclicaromatichydrocarbonsinaroadsideteafield.LINDao-hui,ZHULi-zhong(DepartmentofEnvironmentalScience,ZhejiangUniversity,Hangzhou310028,China).ChinaEnvironmentalScience,2008,28(7)：577~581Abstract：Polycyclicaromatichydrocarbon(PAH)contentsinair,soil,andteaplantsamplesfromaroadsideteafieldwereanalyzed,andthecontributionoftrafficexhauststothePAHsinfreshtealeaveswasdiscussed.Totalconcentrationsof16PAHs(∑PAHs)intheair,soil,andteasampleswere1780~4710ng/m3,n.d.~35.9µg/kg,and100~885µg/kg,respectively.∑PAHsdecreasedwithincreasingdistancefromtheroadcurb,implyingthattrafficexhaustsmaybethemainPAHsourcetotheteafield.However,∑PAHsoftheteaplantatthesamplingsiteof50mfromtheroadcurbvariedlittlefromthatof250m,indicatingthattheimpactoftrafficexhaustsonteaPAHcontentsmaybelimitedin50mfromtheroadcurb.∑PAHsoftheabove-groundteatissueswerehigherthanthatoftheundergroundpart,withanorderofmatureleaves>fibrousroot>tenderleaves>softshoot>taproot.80.6%of∑PAHsinthetenderleaveswerethe3-ringPAHs.However,4-ringPAHcontentsinthematureleaveswerehigherthanthe3-ringones,andthematureleaveshadmuchhigher5-6ringPAHsthanthetenderleaves,suggestingthattealeavesarepronetoaccumulatinghighringPAHs.Keywords：tea；trafficexhaust；polycyclicaromatichydrocarbons；pollutantsourceanalysis多环芳烃(PAHs)是环境中广泛存在的一类持久性的“三致”有毒有机污染物,主要由石油、煤等化石燃料及木材、烟草等在不完全燃烧过程中产生,可通过多种途径进入农作物,进而可能影响人体健康[1].成茶中已检出PAHs[2].茶叶中的PAHs能随泡茶过程溶出而进入人体[2-3].制茶过程可能是PAHs污染的主要途径[4].但实验室研究表明,空气中的PAHs会强烈吸附在鲜叶上,根部吸附/吸收的PAHs也会在一定程度上转运到鲜叶中[5].迄今,鲜见野外调查研究茶园茶鲜叶中PAHs的污染状况及源解析的报道.只有了解茶鲜叶中PAHs的污染来源,才能采取针对性的防治措施.本研究考察了某交通道路旁茶园的空气、土壤和茶树根、茎、叶等介质中PAHs的污染特征,分析汽车尾气对茶鲜叶中PAHs的影响,为防治路域内茶园PAHs污染提供科学依据.1实验部分1.1样品采集与预处理茶园位于2条交通道路的交界处,面积约为收稿日期：2007-12-27基金项目：国家自然科学基金资助项目(20507015,20737002);十一五国家科技支撑计划课题(2006BAJ02A08-2);国家“973”项目(2003CB415004);责任作者,教授,zlz@zju.edu.cn578中国环境科学28卷200m×250m.茶园内的茶树品种为龙井43,生产历史30多年.在茶园内布置3个采样点,距交通道路1的红线距离分别约5,50,250m(图1),距交通道路2的红线距离约150m.茶园所在地夏季盛行东南风,冬季多西北风.采样时天气晴朗,基本无风,气温约30°C,交通道路1上的车流量约为90辆/h,交通道路2上约为60辆/h.交通道路2▲▲小土丘(1~2m高)茶园小树林小树林交通道路15m50m▲250m图1交通道路旁茶园采样点示意Fig.1Samplingsitesintheroadsideteafield每个采样点均采集茶组织、空气、土壤3类样品,样品采集方法详见文献[6].茶组织分嫩叶、老叶、生产枝、须根、主根5部分,每个采样点每部分茶组织采集量约1kg(须根、主根较少,约0.5kg),在距交通道路红线同一距离3个不同点采集后合并;样品采集后密封在样品袋内运往实验室,先用自来水冲洗干净,再用超纯水漂洗3次,滤纸蘸干表面水分后装入样品袋放进冰箱备用.空气样品采用DDY-1.5型低噪音、小体积采样泵同时采集气态和颗粒态PAHs,采样流量为1.0L/min,采样时间为5h,采样高度为1.5m.在每个土壤样品采集点均设置0~20cm、20~40cm、40~60cm3个垂直剖面.每个剖面土壤样品采集总量约1.5kg,在距交通道路红线同一距离3个不同点的同一垂直剖面采集后合并;土壤样品于托盘中自然风干,剔除小石子、茶树根等杂质,磨碎过20目筛后保存在冰箱中.1.2仪器与试剂Agilent-1100型高效液相色谱仪(G1314A紫外检测器,直径4.6mm、长250mm的C18PAHs专用色谱柱),KQ-300DE型医用数控超声波清洗器,RM-3型旋转浓缩蒸发器,PALL纯水器,IKAA11basic型分析用研磨机,直径0.7cm、长25cm的层析柱,DDY-1.5型大气采样器.16种PAHs混合标样购自Supelco公司,分别为萘(NA),苊(ACY),二氢苊(ACE),芴(FLU),菲(PHEN),蒽(AN),荧蒽(FL),芘(PY),苯并(a)蒽(BaA),(CHRY),苯并(b)荧蒽(BbF),苯并(k)荧蒽(BkF),苯并(a)芘(BaP),二苯并(a,h)蒽(dBAn),苯并(ghi)苝(BPe),茚(1,2,3-cd)芘(IcdP).乙腈、二氯甲烷、丙酮、正己烷均为色谱纯.无水硫酸钠、层析用硅胶(200~300目)为分析纯.1.3PAHs提取与分析样品的前处理与分析方法参见文献[6].空气中的气态(吸附在XAD-2颗粒上)与颗粒态(沉淀在玻璃纤维滤膜上)PAHs用有机溶剂超声提取,氮吹浓缩后用乙腈定容.磨碎过20目筛后的土壤样品及用研磨机粉碎混匀后的茶组织样品用有机溶剂超声提取,经无水硫酸钠柱脱水和硅胶柱净化,旋转蒸发浓缩后用乙腈定容.定容后的乙腈溶液过0.22µm孔径滤膜后,进入HPLC/UV分析,分析条件:Agilent-1100高效液相色谱仪;柱温:40;℃流动相:乙腈-水;流速:1.0mL/min;进样量:15µL;采用梯度淋洗和波长切换.1.4质量控制为了保证评价方法的准确度,在XAD-2、滤膜、土壤和茶叶样品中,加入用甲醇稀释的PAHs混合标准液,暗处静置,待甲醇挥发后,采用上述样品的前处理和分析方法,测定其PAHs本底(空白对照)和加标后的实测值.计算得XAD-2和滤膜中16种PAHs的加标回收率,除萘分别为76%和78%外,其余大于84%,相对标准偏差低于10%;土壤和茶叶样品中16种PAHs的加标回收率大于70%,相对标准偏差低于20%.各类样品中16种PAHs的检测限:空气7.91~49.30ng/m3;土壤0.475~2.960µg/kg;茶组织0.791~4.930µg/kg.每个样品设置2个重复,取平均值.每组实验设置2个空白和1个加标.2结果与讨论2.1茶园空气中PAHs汽车尾气中含有PAHs,会对道路两侧空气造成一定程度的污染[7-8].茶园离交通道路红线不同距离7期林道辉等：交通道路旁茶园多环芳烃的污染特征579处空气中PAHs的浓度为1780.0~4710.0ng/m3(表1),高于国外相关文献报道值[7],但低于国内交通主干道旁的有关报道值[8].离交通道路250m处空气中∑PAHs明显低于近距离两点,但近距离两点空气中PAHs的浓度变化不明显,这是因为空气中主要是气态PAHs,在近距离内沉降和降解差异不大.空气中萘占∑PAHs的比例为53.9%~65.0%,未检出5~6环PAHs.表1交通道路旁茶园空气中PAHs浓度水平(ng/m3)Table1AirPAHconcentrationsinaroadsideteafield(ng/m3)气态PAHs颗粒态PAHs总浓度PAHs种类5m50m250m5m50m250m5m50m250mNA3030.02870.0922.027.741.536.93060.02910.0959.0ACY112.0132.086.422.86.06.0134.0138.092.4ACE95.1116.069.1n.d.n.d.n.d.95.111669.1FLU220.0253.068.366.766.7n.d.287.0320.068.3PHEN608.0767.0403.0151.014347.6759.0909.0451.0AN25.497.729.58.0n.d.n.d.33.497.729.5FL114.0117.088.714.2n.d.n.d.128.0117.088.7PY133.072.020.822.7n.d.n.d.155.072.020.8BaA51.9n.d.n.d.n.d.n.d.n.d.51.9n.d.n.d.CHRYn.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.BbFn.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.BkFn.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.BaPn.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.dBAnn.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.BPen.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.IcdPn.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.∑PAHs4390.04420.01690.0313.0257.090.54710.04680.01780.0注:指采样点距交通道路红线的距离;n.d.为未检出2.2茶园土壤中PAHs茶园土壤中PAHs含量较低,大部分未检出,∑PAHs为n.d.~35.90µg/kg(表2),低于文献报道值[9].这是因为茶园附近除交通道路外基本无其他PAH污染源,土壤经过多年栽培,PAHs本底含量已很低,而土壤上茶树的郁闭度接近100%,大气中PAHs很难直接沉降到土壤上.虽然交通道路上的PAHs可能会被雨水冲刷到两侧土壤中[10],但影响只局限于交通道路两侧小范围.与茶园空气中PAHs相似,250m处土壤中PAHs含量明显低于其他两点,基本不能检出.虽然5m处∑PAHs随土壤深度增加呈下降趋势,但总体上看,PAHs含量随土壤深度增加变化不明显.2.3茶组织中PAHs茶组织中∑PAHs为100~885µg/kg(表3),与文献[1]报道的植物中PAHs浓度水平相当.总体上看,茶树各组织中∑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.各组织中∑PAHs均随离交通道路距离增加而降低,说明汽车尾气可能是茶树中PAHs的主要来源.离交通道路红线距离5m处茶树各组织中∑PAHs明显高于50m和250m处的相应的∑PAHs,而50m和250m处的各相应组织中∑PAHs的差异不明显,说明汽车尾气对茶园茶树中PAHs含量的影响主要在交通道路旁50m范围内.研究表明,汽车尾气对路旁茶园茶组织中重金属浓度水平的影响也局限在近距离范围内[11].580中国环境科学28卷表2交通道路旁茶园土壤中PAHs浓度(µg/kg,干重)Table2SoilPAHcontentsinaroadsideteafield(µg/kg,dw)5m处50m处250m处PAHs种类0~20cm#20~40cm#40~60cm#0~20cm#20~40cm#40~60cm#0~20cm#20~40cm#40~60cm#NA0.26n.d.2.59n.d.0.47n.d.1.611.49n.d.ACY21.7014.80n.d.10.6010.003.75n.d.n.d.n.d.ACEn.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.FLU3.763.172.753.502.572.551.743.06n.d.PHEN6.273.641.528.604.416.20n.d.n.d.n.d.ANn.d.5.63n.d.n.d.n.d.n.d.n.d.n.d.n.d.FLn.d.1.820.820.661.911.49n.d.1.47n.d.PYn.d.n.d.n.d.n.d.6.37n.d.n.d.n.d.n.d.BaAn.d.n.d.1.17n.d.1.001.39n.d.n.d.n.d.CHRYn.d.n.d.1.40n.d.1.431.54n.d.1.08n.d.BbFn.d.n.d.2.68n.d.2.942.55n.d.n.d.n.d.BkF1.19n.d.1.441.301.391.34n.d.n.d.n.d.BaPn.d.n.d.1.38n.d.n.d.1.22n.d.n.d.n.d.dBAnn.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.BPen.d.n.d.1.52n.d.1.661.50n.d.n.d.n.d.IcdP1.06n.d.1.551.001.701.42n.d.n.d.n.d.ΣPAHs34.2029.1018.8025.6035.9024.903.347.09n.d.注:指采样点离交通道路红线的距离;#指采样深度;n.d.为未检出表3交通道路旁茶园茶组织中PAHs浓度(µg/kg,干重)Table3PAHcontentsofteatissuesinaroadsideteafield(µg/kg,dw)嫩叶老叶生产枝须根主根PAHs种类5m50m250m5m50m250m5m50m250m5m50m250m5m50m250mNA11.306.909.9336.3047.6030.5022.5020.2021.9050.4033.2020.1027.9013.2021.70ACY160.00118.0075.80n.d.n.d.n.d.26.9027.2026.9054.403.1615.0043.90n.d.23.20ACE65.2048.5044.1026.7032.407.1438.5013.9028.9037.8046.9037.3024.6020.7020.60FLU14.7017.7020.9025.9020.2024.6054.2026.9016.6022.4018.4016.7017.009.497.59PHEN59.1044.2019.50189.00111.00111.0037.40n.d.n.d.65.7006.96n.d.n.d.n.d.n.d.AN1.751.361.4412.502.391.621.261.0101.173.722.641.011.921.331.07FL23.1013.604.7238.0034.60n.d.42.7011.2015.1012.54.67n.d.6.78n.d.n.d.PY22.6015.8026.30291.00204.00189.0087.6036.30n.d.186.0082.8020.4082.0057.2022.90BaA2.25n.d.n.d.6.646.335.6615.901.529.941.771.913.63n.d.1.371.10CHRY6.624.052.4118.7019.3015.1011.204.91n.d.4.951.34n.d.1.89n.d.n.d.BbF4.18n.d.n.d.31.3019.0016.1088.20n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.BkF4.56n.d.n.d.17.804.544.9114.402.57n.d.4.663.87n.d.4.941.161.86BaP4.63n.d.n.d.22.003.034.35n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.n.d.dBAnn.d.n.d.n.d.60.9020.105.59n.d.n.d.n.d.56.10n.d.11.40n.d.n.d.n.d.BPe1.12n.d.n.d.27.1011.303.50n.d.n.d.n.d.4.3911.90n.d.n.d.n.d.n.d.IcdP4.38n.d.n.d.81.6017.9014.00n.d.n.d.n.d.26.107.483.06n.d.n.d.n.d.∑PAHs385.00271.00205.00885.00554.00434.00441.00146.00121.00531.00225.00129.00211.00104.00100.00注同表17期林道辉等：交通道路旁茶园多环芳烃的污染特征581茶组织中的PAHs以低环为主,5~6环的浓度较低(图2).嫩叶中以3环为主,约占∑PAHs的80.6%;老叶中4环比例高于3环,3~4环合计占∑PAHs的68.7%~81.8%.茶叶中的低环PAHs更易挥发或被降解,因此,生长时间越长,高环PAHs比例越大.汽车尾气中高环PAHs主要以颗粒态形式存在[12],比低环PAHs更易沉降,对交通道路两侧的影响距离更短.因此,茶树地上部分5~6环PAHs的浓度及比例均随离交通道路距离增加而呈降低趋势,250m处的嫩叶与生产枝中未检出.茶树地下部分PAHs构成的变化与地上部分不同,其变化规律不明显,说明茶树地下部分与地上部分的PAHs来源可能不同,而且地上部分的PAHs很难迁移转运至地下部分,尤其是高环PAHs.6环5环4环3环2环3结语汽车尾气会在一定程度上造成路旁茶园的PAHs污染.茶鲜叶,尤其是老叶能蓄积毒性较强的高环PAHs.但汽车尾气对茶园环境PAHs的影响主要局限在路旁50m之内.参考文献：[1]WagrowskiDM,HitesRA.Polycyclicaromatichydrocarbonaccumulationinurban,suburban,andruralvegetation[J].EnvironmentalScienceandTechnology,1997,31(1):279-282.[2]LinDH,TuYY,ZhuLZ.Concentrationsandhealthriskofpolycyclicaromatichydrocarbonsintea[J].FoodandChemicalToxicology,2005,43(1):41-48.[3]LinDH,ZhuLZ,LuoL.Factorsaffectingtransferofpolycyclicaromatichydrocarbonsfrommadeteatoteainfusion[J].JournalofAgriculturalandFoodChemistry,2006,54(12):4350-4354.[4]LinDH,ZhuLZ.Polycyclicaromatichydrocarbons:pollutionandsourceanalysisofablacktea[J].JournalofAgriculturalandFoodChemistry,2004,52(26):8268-8271.[5]LinDH,ZhuLZ,HeW,etal.Teaplantuptakeandtranslocationofpolycyclicaromatichydrocarbonsfromwaterandaroundair[J].JournalofAgriculturalandFoodChemistry,2006,54(10):3658-3662.[6]LinDH,ZhuLZ,WangJ.EnvironmentalimpactofPAHsonthemetal-smeltingareaofTangxia,China[J].FreseniusEnviron-mentalBulletin,2004,13(5):447-453.[7]OdaJ,NomuraS,YasuharaA,etal.Mobilesourcesofatmosphericpolycyclicaromatichydrocarbonsinaroadwaytunnel[J].AtmosphericEnvironment,2001,35(28):4819-4827.[8]朱利中,刘勇建,沈学优,等.城市道路交通PAHs污染现状及来源解析[J].环境科学学报,2000,20(2):183-186.[9]TrapidoM.PolycyclicaromatichydrocarbonsinEstoniansoil:contaminationandprofiles[J].EnvironmentalPollution,1999,105(1):67-74.[10]KreinA,SchorerM.Roadrunoffpollutionbypolycyclicaromatichydrocarbonsanditscontributiontoriversediments[J].WaterResearch,2000,34(16):4110-4115.[11]石元值,马立锋,韩文炎,等.汽车尾气对茶园土壤和茶叶中铅、铜、镉元素含量的影响[J].茶叶,2001,27(4):21-24.[12]ZielinskaB,SagebielJ,ArnottWP,etal.Phaseandsizedistri-butionofpolycyclicaromatichydrocarbonsindieselandgasolinevehicleemissions[J].EnvironmentalScienceandTechnology,2004,38(9):2557-2567.作者简介：林道辉(1973-),男,浙江瑞安人,副教授,博士,主要从事环境污染化学研究.发表论文20余篇.
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