Protective Effects of Roadside Tree Lines on Heavy Metals Pollution to Roadside Tea Gardens in Wuyishan

In order to study protective effect of roadside tree lines on heavy metals pollution (Pb, Zn, Cd, Cu, Cr and Mn) to roadside tea gardens in Wuyishan, samples of soils and tea leaves were collected from two neighboring sections of a roadside tea plantation, of which one has a roadside tree line (Section B) and the other does not (Section A). With an ICP-MS, concentrations of these heavy metals in the samples were measured. Correlation analysis and principal component analysis of heavy metals in the soil and tea leaves differed in result between Section A and Section B, which may be attributed to the effect of the roadside tree lines intercepting pollutants from the road. The principal component analysis reveals that concentrations of the six heavy metals in the samples, that Pb, Cu and Zn was mainly affected by traffic, while that of Mn and Cr by both traffic and geological background, and that of Cd by both traffic and fertilization. Moreover, it was also found that a single row of fir trees along the roadside in Section B could reduce not only the mean concentrations of heavy metals in the tea trees 1-150 m away from the roadbed, but also the range of maximal concentrations of Zn and Pb alongside the road from 50-80 m down to 1-10 m, which was possibly attributed directly to the effect of the roadside tree line intercepting pollutants from the traffic and indirect to its interception of carbonate dispersal affecting soil pH. Obviously, decreasing the concentrations of traffic related heavy metals in tea and improving quality of the tea in roadside tea gardens can be achieved through planting roadside trees alongside the road in the tea gardens.