降尘对乌鲁木齐地产辣椒中Pb含量的影响

Effects of dustfall on the content of Pb in peppers growing in Urumqi

为了探究降尘对辣椒中Pb含量的影响,通过同位素示踪结合盆栽试验,分析了干沉降及湿沉降对辣椒中Pb含量的影响。结果表明:辣椒各部位^(208)Pb计数值总体呈现T3(喷涂^(208)Pb湿沉降)>T2(涂抹^(208)Pb干沉降)>T1(涂抹干沉降)>CK1(未涂抹降尘)的趋势,且T3中^(208)Pb计数值远高其他3组,T3果实总Pb含量显著高于CK1(p<0.05),说明降尘是辣椒果实中Pb的重要来源,特别是湿沉降极大地促进了果实中Pb的累积。根据《食品安全国家标准-食品中污染物限量(GB2762-2017)》,茄果类蔬菜中的Pb含量限值为0.1mg·kg^(-1),T4(露天种植)和CK2(棚内种植)辣椒果实平均Pb含量分别为0.015 mg·kg^(-1)、0.005mg·kg^(-1),均未超标。通过辣椒叶面、果实、集尘缸降尘淋洗液中离子的浓度对比分析发现,T4辣椒叶面Pb^(2+)与叶片Pb含量呈显著负相关(p<0.05);叶面降尘中HCO^(-)_(3)、NO^(-)_(3)与叶片Pb含量呈显著正相关,SO^(2-)_(4)与果实Pb含量呈显著负相关,Mg^(2+)与果实Pb极显著正相关(p<0.01);果实降尘中Cl-与果实Pb呈显著负相关。降尘淋洗液p H值大小依次为T4叶片<T4果实<CK2果实<CK2叶片<集尘缸,p H值的降低有利于重金属生物有效性增加。加强对乌鲁木齐市大气降尘的源头治理,有助于降低蔬菜中Pb的含量。

In order to explore the effect of dustfall on Pb content in pepper,the effects of dry and wet deposition on Pb content in pepper were analyzed by isotope tracing combined with pot experiment.The results showed that the^(208)Pb counts in each part of pepper showed a trend of treatment T3(wet deposition-sprayed^(208)Pb)>T2(dry deposition-smeared^(208)Pb)>T1(dry deposition-smeared)>control CK1(no dust deposition),and the^(208)Pb counts in T3 were much higher than the other three groups,the total Pb content of fruit in treatment T3was significantly higher than that of CK1(p<0.05),indicating that dustfall was an important source of Pb in pepper fruit,especially wet deposition greatly promoted the accumulation of Pb in fruit.According to the"National Food Safety Standard-Limits of Contaminants in Foods(GB2762-2017)",the limit of Pb content in nightshade vegetables is 0.1mg·kg^(-1).In our experiment,the average Pb content in the fruit of peppers in treatment T4(open-air planting)and CK2(indoor planting)were 0.015mg·kg^(-1)and 0.005mg·kg^(-1),respectively,which did not exceed the standard.Through the comparative analysis of the concentration of ions in pepper leaves,fruits,and the dust-fall leachate in the dust collecting tank,it was found that the Pb^(2+)in leaf dustfall in T4 was significantly negatively correlated with the leaf Pb content(p<0.05),HCO^(-)_(3)and NO^(-)_(3)in leaf dustfall were significantly positively correlated with leaf Pb content,SO^(2-)_(4)was significantly negatively correlated with fruit Pb content,Mg^(2+)was significantly positively correlated with fruit Pb(p<0.01),Cl^(-)in fruit dustfall was significantly negatively correlated with fruit Pb.The pH value of the dust-fall eluent was in the order of T4 leaf<T4 fruit<CK2 fruit<CK2 leaf<dust collection tank,and the decrease of pH value was beneficial to the increase of the bioavailability of heavy metals.Therefore,strengthening the source control of atmospheric dust in Urumqi will be helpful to reduce the content of Pb in vegetables.