不同茶园土壤中外源铅的形态转化及其生物有效性

为了明确外源铅进入不同茶园土壤后其形态的转化及其生物有效性,采用盆栽试验及连续浸提形态分级方法,研究了外源铅在不同茶园土壤中的形态分布规律及其在茶树体内的累积分布规律。结果表明,不同母质茶园土壤中铅总量及各形态的含量有明显差异,无外源铅污染的情况下,临安凝灰岩与金华红壤母质茶园土壤以残渣态占主导地位,嵊州玄武岩和梅家坞鞍山母质茶园土壤则以铁锰态铅占主导地位,4种土壤的交换态含量均较低,均在总量的10%以内。当受外源铅污染后,4种茶园土壤中各形态铅均有不同程度的增加,转变为以铁锰态为主,碳酸盐态及可交换态含量在总量中所占比例明显增加,但不同母质土壤类型差异较大。在小于500mg·kg-1土的外源铅污染下,交换态以嵊州玄武岩、临安凝灰岩增幅最大,金华红壤最小;但外源铅达到2500mg·kg-1土时,金华红壤中的交换态铅急剧增加。低浓度外源铅对金华红壤、梅家坞鞍山斑岩茶园土中的茶树生长发育有促进作用,但对嵊州玄武岩和临安凝灰岩茶园土壤中的茶树生长刺激作用并不明显。高浓度的外源铅则对4种土壤中的茶树生长均产生明显的抑制作用,且碳酸盐态与交换态对茶树生长的抑制作用最大。对新梢中的铅而言,金华红壤茶园土壤以有机态铅对其贡献最大,其余3种母质茶园土壤均以碳酸盐态贡献最大;对老叶与茎杆中的铅而言,嵊州玄武岩母质茶园土壤以有机态贡献最大,其余3种土壤均以铁锰态贡献最大;对须根中的铅而言,梅家坞鞍山斑岩茶园土以有机态贡献最大,其他3种土壤均以铁锰态贡献最大。

Influence of Exogenous Lead on Change of Lead Forms and Bioavailability in Different Tea Garden Soils

Many studies have showed that the effect of lead（Pb）on soil-plant system is determined by Pb chemical forms,not by total Pb content.Therefore,studying the Pb characteristics in soils could be used to evaluate Pb pollution in tea garden soils.Exogenous Pb was added to study the distribution of Pb forms and their bioavailability to tea plants in four kinds of different parent material tea garden soils using pot experiments and the sequential extraction method.The results showed that,the forms and total lead content in different kinds of tea garden soils varied in different parent material soils.In case of no Pb pollution soil,the residual-Pb was the dominant one in soils with parent materials of quaternary red soil and porphyry.However,the Fe-Mn oxide-Pb was the dominant form in soils with parent materials of basalt and tuff.And the exchangeable-Pb in all those soils was low and accounted for less than 10% of total Pb content.When exogenous Pb was added into those soils,the contents of all Pb forms increased significantly,and the Fe-Mn oxide-Pb became the dominant form.When the added exogenous Pb was less than 500 mg·kg-1 soil,the exchangeable-Pb was the highest in the soils with the parent materials of basalt and tuff,and the lowest in red soil.When the exogenous Pb was added to 2 500 mg·kg-1 soil,the exchangeable-Pb in soils derived from basalt and quaternary red soil were the highest.The low concentration of exogenous Pb could improve the biomass of tea plants,but the high concentration of exogenous Pb restrained the growth of tea plants.The carbonate-Pb and exchangeable-Pb had the higher bioavailability but larger negative impact on the biomass of tea plants when high amount of Pb added to the soils.The organic-Pb and carbonate-Pb were the greatest contribution form to the tea shoots in the red soil and other three soils,respectively.The greatest contribution form was the organic-Pb to the lead content in the mature leaves and stalks in the basalt soil.It was Fe-Mn oxide-Pb for other three parent material soils.The organic-Pb was the greatest contribution form to the lead content in the absorption roots for porphyry soil,but for other three parent material tea garden soils,it was the Fe-Mn oxide-Pb.