三种蔬菜对镍累积转运规律及食用安全研究

为了解三种蔬菜(黄瓜、豇豆、青椒)体内镍(Ni)累积转运规律及食用安全,采用盆栽实验研究了不同浓度Ni处理[原土(对照)、200、350、500、650、800 mg·kg~(-1)]对三种蔬菜生物量、体内分配特征及富集规律的影响。结果表明:(1)Ni对三种蔬菜生长的影响因蔬菜品种不同而不同。在试验浓度范围促进黄瓜的生长;低浓度Ni促进青椒和豇豆生长,当土壤中Ni浓度为650 mg·kg~(-1)时青椒和豇豆的生长受到抑制。(2)在所研究土壤Ni浓度条件下三种蔬菜各部位Ni含量分布不同,青椒和豇豆中根茎叶可食部分;黄瓜中茎叶根可食部分。三种蔬菜中Ni由根部向可食部位转运能力豇豆黄瓜青椒;根部向茎叶转运能力黄瓜豇豆青椒。(3)黄瓜、豇豆、青椒可食部分Ni累积量与土壤中Ni投加量呈显著正相关关系(r2分别为0.973、0.984、0.992,P0.05)。三种蔬菜可食部分Ni含量高于基于美国环境保护署(USEPA)推荐的Ni人体最大允许摄入量所推导的新鲜蔬菜中Ni的安全阈值(成人3.58mg·kg~(-1),儿童2.83 mg·kg~(-1))。Ni在豇豆中的富集能力高于黄瓜和青椒,更容易超过食品安全阈值,Ni污染土壤要避免种植豇豆。

Accumulation and transport of nickel in three vegetable crops and their edible safety

In the present study, the accumulation characteristics of nickel(Ni)in three kinds of vegetable crops(cucumber, cowpea and green pepper)and their safety for ingestion were investigated. A pot experiment was carried out with six different dosages of Ni(control, 200, 350, 500, 650, and 800 mg·kg^-1)to investigate the effects of Ni on the biomass and accumulation of Ni in different parts of the vegetable crops. The results showed that:(1)The effects of Ni on the growth of three vegetable crops differed. The growth of cucumber was promoted by Ni at the concentration range tested. Relatively low concentration of Ni promoted the growth of green pepper and cowpea. Furthermore, the growth of green pepper and cowpea was inhibited when the concentration of Ni in soil was above 650 mg·kg^-1.(2)The amount of Ni in different parts of the vegetable crops was different. In green peppers and cowpea, Ni accumulation was in the order of root > stem and leaf > fruit, while, in cucumber, the accumulation was in the order of stem and leaf > root > fruit. The transportation rate of Ni from root to edible parts was in the order of cowpea > cucumber > green pepper, and that from root to stem and leaf was in the order of cucumber> cowpea> green pepper.(3)The accumulation of Ni in the edible parts positively correlated with the amount of Ni in soil(R² was 0.973, 0.984, and 0.992,respectively, P<0.05). The concentration of Ni in the edible parts was higher than the safety threshold of Ni in fresh vegetables based on the maximum allowable intake of Ni for humans recommended by the United States Environmental Protection Agency(USEPA)(adult 3.58 mg·kg^-1; children 2.83 mg·kg^-1). The concentration of Ni in cowpea exceeds the food safety threshold with high probability. Therefore planting cowpea in Ni contaminated soils is not recommended.