松阳县高速公路粉尘对茶叶重金属含量影响程度的探讨

Effect of stives from expressway on content of heavy metals in tea leaves in Songyang County

在浙江省松阳县新兴镇茶区选一段山脚下高速公路,在其中200 m路段的路边种植3m高的小松树作为绿篱,从绿篱伸向5°山坡上茶园深处500 m设为绿篱区;相连的200 m路段不种植绿篱,从其路边伸向山坡上茶园500 m为对照(CK)区。在种植绿篱前、后1.5年,采集1芽1叶嫩梢、成叶和表土,检测铅、砷、镉、铬、铜、镁、锰、钠、镍和锌10种元素含量。结果:(1)种植绿篱前后,无论绿篱区还是CK区,嫩梢、成叶和表土的铅等10种元素含量范围皆没有明显改变,比如绿篱区内,种绿篱之前距路边0 m、100 m、200 m、300 m、400 m和500 m的1芽1叶嫩梢、成叶和表土的铅含量范围分别为0.25～0.55 mg/kg、0.47～2.11 mg/kg和23.11～37.46 mg/kg,种植绿篱1.5年之后,则分别为0.23～0.56 mg/kg、0.45～2.13 mg/kg以及23.05～37.42 mg/kg;(2)种植绿篱前、后,未有距离路边愈远,重金属含量呈递减的趋势;(3)铅、砷、铬和锰在嫩梢中含量明显小于在成叶中含量,4者在成叶中有累积效应;铜、镁、锌和镍在嫩梢中含量明显大于在成叶中含量。认为:现阶段高速公路汽车尾气和扬尘对于路边茶园的重金属污染可忽略。

Pine trees with 3 m height were planted between roadside of expressway and tea fields in Songyang County for investigating the effects of expressway stives on the contaimination of heavy metals in tea leaves.The tea fields were 500 m away from the expressway.A same tea filed without plant hedge was used as control block.Concentrations of Pb,As,Pd,Cr,Cu,Mg,Mn,Na,Ni and Zn in mature leaves,shoots with one leaf and a bud and top soil were detected in samples token 1.5 years before planting the hedge plants and 1.5 year after planting the hedge plants.The results showed that:①There were no significant changes in concentrations of the tested heavy metals in texted samples and control before and after growing the hedge plants.For instance,in the hedge plants block,the concentrations of Pb in the shoots with one leaf and a bud,mature leaves and topsoil at the locations 0 m,100 m,200 m,300 m,400 m and 500 m away from the roadside were 0.25-0.55 mg/kg,0.47-2.11 mg/kg and 23.11-37.46 mg/kg 1.5 years before the hedge plant growing,respectively.After 1.5 years of the hedge plant growing,the concentrations of Pb were 0.23-0.56 mg/kg,0.45-2.13 mg/kg and 23.05-37.42 mg/kg,respectively.②There were no significant changes in the concentration of heavy metals in the samples collected at locations with various distances from the expressway.③The concentrations of Pb,As,Cr and Mn in the shoots with one leaf and a bud were obviously lower than those in the mature leaves,while the concentrations of Cu,Mg,Zn and Ni in the shoots with one leaf and a bud were markedly higher than those in the mature leaves.It is considered that vehicle exhaust and expressway stives are not the major factors leading to the pollution of the heavy metals in tea leaves.