不同宽度林带对国道两侧农田水稻叶片和糙米中重金属含量的影响

以205国道淮安段具有5 m和20 m宽林带的路段为研究区域,对国道东西两侧200 m范围内农田水稻(Oryza sativa L.)叶片和糙米中Al、Fe、Cu、Zn、Cd、Cr、Ni和Pb含量及其与路侧距离的相关性进行了分析.结果表明:具5 m宽林带路段两侧稻叶和糙米中大多数重金属元素的含量呈现随路侧距离增加而减少的趋势,且峰值多出现在距路侧5～10m或20 m附近；其中,东侧稻叶中Cu、Cr和Ni含量及糙米中Al、Fe、Cu、Zn和Ni含量以及西侧稻叶中Cu和Pb含量及糙米中Cd和Pb含量与路侧距离呈显著或极显著负相关.具20m宽林带路段两侧稻叶和糙米中大多数重金属元素的含量并没有呈现随路侧距离增加而减少的趋势,且峰值多出现在距路侧20 m以外；只有东侧稻叶中Cr和Ni含量及糙米中Fe和Ni含量以及西侧糙米中Al和Cu含量与路侧距离呈显著或极显著负相关.具5m宽林带路段两侧稻叶和糙米中的重金属含量分布特征与无林带路段十分相似,而具20m宽林带路段两侧稻叶和糙米中的重金属含量较低,说明20 m宽林带对公路大气污染物有较明显的阻滞作用.根据研究结果,建议在公路两侧10～20 m范围内设置乔灌草结构模式的防护林带,并适当提高防护林中灌木的比例,保持乔木疏密适度.

Effects of forest belts with different widths on heavy metal content in rice leaf and brown rice in crop field on both sides of national road

Taking Huai’an section of No.205 national road with 5 m and 20 m width forest belts as the research region,contents of Al,Fe,Cu,Zn,Cd,Cr,Ni and Pb in rice leaf and brown rice(Oryza sativa L.) in crop field of 200 m range away from eastern and western road sides and the correlation between heavy metal content and distance away from road edge were analyzed.The results show that contents of most heavy metal elements in rice leaf and brown rice on both sides of the section with 5 m width forest belt have the decreasing trend with increasing of distance away from road edge and most peak values of them appear at nearby 5-10 m or 20 m away from road edge.In which,contents of Cu,Cr and Ni in rice leaf and contents of Al,Fe,Cu,Zn and Ni in brown rice on the eastern side,contents of Cu and Pb in rice leaf and contents of Cd and Pb in brown rice on the western side all have significantly or extremely significantly negative correlation with distance away from road edge.However,contents of most heavy metal elements in rice leaf and brown rice on both sides of the section with 20 m width forest belt have no decreasing trend with increasing of distance away from road edge and their peak values appear at over 20 m away from road edge.And only contents of Cr and Ni in rice leaf and contents of Fe and Ni in brown rice on the eastern side,contents of Al and Cu in brown rice on the western side have significantly or extremely significantly negative correlation with distance away from road edge.Comparing with the section without forest belt,distribution characteristics of contents of heavy metals in rice leaf and brown rice on both sides of the section with 5 m width forest belt are similar,but contents of heavy metals on both sides of the section with 20 m width forest belt are lower.It means that 20 m width forest belt has an obvious detention effect to atmospheric pollutant of road.According to these results,it is suggested that the shelter belt with structure model of arbor-shrub-herb should be set at 10-20 m area on both road sides,properly increase shrub proportion in the belt and keep appropriate density of trees.