楠竹笋对土壤中铅和镉的吸收特征分析

Absorption Characteristics Analysis of Pb and Cd from Soil by Phyllostachys pubescens Shoots

为了研究楠竹笋生长时期对土壤中铅(Pb)和镉(Cd)的累积效应及在各器官中的分配特征,在竹笋生长期的楠竹林里,施加外源硝酸铅(Pb(NO_3)_2)和硝酸镉(Cd(NO_3)_2)模拟土壤不同污染程度:5 mg·m^(-2)轻度污染、50 mg·m^(-2)中度污染、500 mg·m^(-2)重度污染以及0 mg·m^(-2)(对照)4个浓度梯度的Pb、Cd,分析Pb和Cd在楠竹笋不同生长期及各器官中的富集、累积和分配特征。结果表明:笋中各部位Pb、Cd的富集与外施Pb、Cd浓度和时间呈正相关,竹笋体内Pb和Cd的累积量随时间推移、污染程度增强而明显增加。三种污染程度中,除重度污染笋底在第21 d Pb含量超标,楠竹笋可食部分Pb含量均低于国家食品卫生标准(1.0 mg·kg^(-1));轻度、中度污染的竹笋可食部分Cd含量在0.02~0.14 mg·kg^(-1),低于国家食品卫生标准(0.2 mg·kg^(-1)),然而重度镉污染使可食部分竹笋在第14 d以后含量超过国家食品卫生标准。重度污染时,施药第21 d后Pb、Cd在竹笋各器官中的累积百分比分别表现为笋根(73.84%、72.79%),笋底(6.33%、6.97%),笋中(2.52%、1.95%),笋尖(2.68%、0.52%),笋皮(14.63%、17.77%)。生物富集系数(BCF)和转移系数(TF)呈"上升"趋势。综上认为,Pb和Cd在楠竹笋体内具有明显的累积效应,并可转移到竹笋地上部各器官或组织中,导致这些器官或组织被Pb和Cd污染。

The aim of this study was to investigate the characteristics of Pb and Cd accumulation and its redistribution in organs of bamboo shoots grown on contaminated soils.Effects of four combinations of two heavy metals Pb and Cd, as polluter at both light pollution （ 5 mg·m - 2 ）, moderate pollution （ 50 mg· m - 2 ）, heavy pollution （ 500 mg· m - 2 ） and non- treated, respectively. Bamboo shoots was grown on Pb-and Cd-contaminated soils under natural conditions, and the accumulation, transport, and organ redistribution of Pb and Cd were then analyzed at various growth stages.The results showed that Pb and Cd accumulation by bamboo shoots was significantly greater in soils with over time and a higher Pb and Cd content.The Pb content of the edible part of bamboo shoots were under national food hygiene standards（ 1.0 mg·kg-1） except excess of the standard with heavy pollution on the 21 th day ;The Cd content of the edible part of bamboo shoots with mild and moderate pollution were 0.02- 0.14 mg·kg-1 ,lower than the national food hygiene standard （0.2 mg·kg-l）, but higher than the national food hygiene standard after the 14th d. under serious contamination after polluting 21 d, the accumulative percent of Pb, Cd in organs of bamboo shoots showed the following pattern ： roots （ 73.84%, 72.79% ）, under part （ 6.33%, 6.97% ）, central part （ 2.52%, 1.95% ）, top part （ 2.68% , 0.52% ）, shell （ 14.63% , 17.77% ）, respectively. The bioaccumulation factor （ BCF ） and the translocation factor（ TF） of Pb and Cd in bamboo shoots gradually increased with an over time.This implied that Pb and Cd had obvious biological accumulation effect in the bamboo shoots, were easily transferred to aboveground parts, and resulted in serious pollution of the plant＇ s organs and tissues.