【作者】 龚宁；

【导师】 杨公明；

【作者基本信息】 西北农林科技大学 ， 食品科学， 2011， 博士

【摘要】 蔬菜为人类提供丰富的维生素、纤维素和矿物质,在膳食结构中占有很重要的地位。相对于其他农作物而言,蔬菜生长周期短,对水、肥和农药的需求量大,因此蔬菜安全问题一直为人们所重视。表面活性剂是一类在较低浓度下就能使液体表面张力显著降低的有机化合物,被广泛应用于日用化工、纺织印染、食品等各领域,用量巨大,在环境中的普遍存在。但目前表面活性剂对蔬菜生长方面和是否促进重金属、农药等有害物质的吸收、富集方面的研究极少。因此,研究表面活性剂对蔬菜的生理毒性,以及表面活性剂-重金属复合污染对蔬菜重金属蓄积的影响,可为农田环境中关于表面活性剂的安全性评价奠定基础,为农业标准的修订提供新的试验依据。本文选择了市场最常见的叶类和根类蔬菜,其中叶类蔬菜包括小白菜(一年生)和韭菜(多年生),根类蔬菜以胡萝卜(多年生)为代表,共3种供试植物,选用直链烷基苯磺酸钠(SDBS)、十六烷基三甲基溴化铵(CTMAB)和吐温80(TW-80)三种表面活性剂,研究表面活性剂对蔬菜生长及其食用安全性的影响。研究表明,表面活性剂浓度高于0.5mg·L-1对蔬菜萌发有明显抑制,同时蔬菜幼根和幼芽发生了一系列抗性生理变化,改变了蛋白质分子氢键数目、果胶质含量和酯类分子中不饱和结构类型比例,提高了幼根中蛋白质、碳水化合物含量。表面活性剂-重金属复合处理时,表面活性剂对蔬菜重金属蓄积量、土壤重金属生物可利用态浓度、蔬菜对重金属的运移能力等均有影响。具体内容如下：1.通过种子萌发实验,探讨蔬菜对表面活性剂的生理响应机理。结果表明：(1)当SDBS、CTMAB和TW-80浓度≥0.5mg·L-1时,对蔬菜的正常萌发产生显著抑制,发芽率显著低于对照组(P<0.05),且随表面活性剂浓度增大而降低。在0.1～5.0 mg·L-1范围时,小白菜等三种蔬菜的幼芽长度、可溶性糖含量和可溶性蛋白含量等生理指标都有“低升高降"的趋势。(2)以发芽率、幼根和幼芽长抑制率三项指标来评判种子萌发受伤害程度及对表面活性剂耐受性的差异,SDBS、CTMAB、TW-80三种表面活性剂对三种蔬菜萌发阶段的生理毒害大小顺序：CTMAB>TW-80>SDBS,而三种蔬菜对同种表面活性剂的耐受性大小顺序为：小白菜>胡萝卜>韭菜。2.运用衰减全反射傅里叶变换红外光谱法(Attenuated Total Reflectance Fourier Transform Infrared Spectrophotometre, ATR-FTIR)分析经表面活性剂处理的蔬菜幼根中蛋白质、碳水化合物等物质结构变化,探讨表面活性剂对植物的伤害机理。由ATR-FTIR谱结果可知,表面活性剂处理浓度较低时(0.1 mg·L-1),小白菜和胡萝卜幼根中蛋白质分子稳定性因氢键比例增加而提高,果胶质比例提高,酯类分子的不饱和结构比例增加,细胞膜的流动性得到改善。韭菜幼根中果胶质的比例增大,自身组织细胞的保水性加强。表面活性剂处理浓度较高时(1.0～5.0 mg·L-1)时,幼根和幼芽的纤维素比例有所增加,蛋白质的氢键减少,结构松散,酯类分子不饱和结构比例有所降低,细胞膜的流动性变差。3.由ATR-FTIR谱特征官能团吸收峰强度与亚甲基吸收峰强度A2926的比值,半定量表征蔬菜幼根和幼芽中蛋白质、碳水化合物和酯类物质相对含量的变化,探讨表面活性剂对植物的伤害机理。结果表明：表面活性剂浓度范围为0.1～1.0 mg·L-1时,小白菜、胡萝卜和韭菜幼根中蛋白质和碳水化合物含量高于对照组,小白菜幼根中酯类化合物含量同时也高于对照。这表明供试植物在表面活性剂影响下,其幼根中的蛋白质、碳水化合物和酯类物质含量得到了应激性的提高。4.通过盆栽试验,研究表面活性剂-重金属复合污染对蔬菜生长量的影响。结果表明：土壤复合污染浓度低时(0.5 mg·Kg-1 Cd+0.5 mg·Kg-1表面活性剂；25.0～50.0mg·Kg-1 Cu+0.5 mg·Kg-1表面活性剂),刺激蔬菜的生长,高浓度复合污染(5.0～10.0mg·Kg-1 Cd+0.5 mg·Kg-1表面活性剂；100.0～200.0 mg·Kg-1 Cu+50.0 mg·Kg-1表面活性剂)则抑制蔬菜的生长。5.运用原子吸收分光光度计(Atomic AbsorptionSpectrometer)测定表面活性剂-重金属复合污染蔬菜体内重金属浓度、重金属在植物体内的迁移率、重金属在土壤中各种形态浓度等指标,结合主成分分析法对上述指标进行了分析,结果如下：(1)主成分分析结果表明,影响蔬菜食用安全的各因素可提取四个主成分,其中表面活性剂-Cd处理组的主成分分别命名为PC1(Cd分布因子)、PC2(Cd运移因子)、PC3(交换态Cd因子)、PC4(表面活性剂浓度因子)；表面活性剂-Cu处理组的主成分分别命名为PC1(Cu分布因子)、PC2(蔬菜的Cu富集因子)、PC3(Cu运移因子)和PC4(表面活性剂浓度因子)。(2)由四个主成分的贡献率可知,不同表面活性剂处理组的各主成分对蔬菜食用安全的影响程度不同,其中表面活性剂-Cd处理组的PC1贡献率顺序SDBS>CTMAB>TW-80, PC2贡献率顺序CTMAB>TW-80>SDBS, PC3贡献率SDBS> CTMAB>TW-80, PC4贡献率顺序SDBS> CTMAB> TW-80;表面活性剂-Cu处理组的PC1贡献率CTMAB>SDBS>TW-80, PC2的贡献率CTMAB> SDBS> TW-80,PC3的贡献率CTMAB>SDBS>TW-80,PC4的贡献率十分接近。(3)由主成分得分排序可知：SDBS、CTMAB和TW-80提高了Cu或Cd从蔬菜根部向茎叶部的运移系数及土壤中Cd交换态比例,同时SDBS和TW-80还促进了蔬菜对Cu的吸收。(4)由各处理组蔬菜的综合得分排序可知：小白菜最易受到重金属污染,且SDBS-重金属复合污染对小白菜食用安全的威胁最大,CTMAB-重金属复合污染对韭菜和胡萝卜食用安全的威胁最大。更多还原

【Abstract】 Vegetables contain vitamins, minerals, cellulose and fiber, which are important part of human being’s main food resource. However, vegetables are easily polluted by sewerage, fertilizer and pesticide for its short growth cycle. So more and more people pay close attention to diet safety of vegetables.As one of organic compound, the surfactants can reduce remarkably liquid surface tension under low concentration. And it is widely used in the daily chemical products, textile printing and dyeing industry, lubricants, carriers and food industry. To the best of our knowledge, whether the surfactants promote vegetables to absorb hazardous substances such as pesticides, heavy metal and organic pollutants was seldom reported. For this reason, it is very important to study whether the surfactants is harmful to the edible plant, and whether the surfactants promote the heavy metal accumulation in tested vegetables.In this experiment, the effects of surfactants on growth and diet safety of vegetables were studied with three tested edible plant and three kinds of surfactants.The leaf vegetables and root vegetables were screened for their common edibility. Brassica rapa L(annual leaf vegetable)and Allium tuberosum L. (perennial leaf vegetables)were selected as the leaf vegetables, and Daucus carrot L.(perennial root vegetables)was selected as the root vegetables. Furthermore, Sodium dodecyl-benzene suffonate (SDBS), Cetyltrimethylamm bromide (CTMAB) and Polysorbate 80 (Tween 80, TW80) were selected as tested surfactants.In oder to study the effects of surfactants on the seeds germination and growth of tested vegetables, the proportion change of pectic substance, the number of hydrogen bond in the protein and the proportion change ofα,β-unsaturated group in ester molecule in these seedlings were detected. So the tested vegetables physiological and harmed response mechanisms which caused from the tested surfactants were discussed.The effects of surfactants combined with the heavy metal on the vegetables biomass, the total accumulation and bioconcentration factors of the heavy metal in tested vegetables, and the elemental form of heavy metal in the soil were investigated. The result showed as follows:1. The tested vegetables’physiological response mechanism caused from the tested surfactants was detected by seeds germination experiment.(1) The result showed that the content of soluble sugar, soluble protein and the seedling length of tested vegetables showed an earlier raised and later decreased tendency under the SDBS, CTMAB and TW-80 concentrations ranged from 0.1 to 5.0 mg-L-1. The seed germination rate of tested vegetables remarkably decreased when the concentrations of tested surfactants were 0.5 mg-1(P<0.05), and decreased following with the increase of the tested surfactants concentrations.(2) Considering the germination rate and the inhibition rate of the tested vegetables seedling growth under the tested surfactants effect, the order of the germination inhibition rate influenced by surfactants was:Allium tuberosum L.> Daucus carrot L.> Brassica rapa L., and the order of the surfactants hurt degree was:CTMAB>TW>SDBS.2. The tested vegetables’harmed response mechanism caused from the tested surfactants was detected by analyzing the structural changes of protein, carbohydrates and ester in the tested vegetables seedlings by means of ATR-FTIR (Attenuated Total Reflectance Fourier Transform Infrared Spectrophoto-metre) method. The details were as follows:In the concentration of 0.1 mg-L"1 surfactants-treatment, there were many variations on the molecular structures in radicles of Brassica rapa L. Chinensis Group and Daucus carrot L., the number of hydrogen bonds in protein molecule was enhanced and the protein stability was increased, the proportion of pectin was increased and the histiocytic water-retaining property was increased, the proportion ofα,β-unsaturated group in ester molecule was increased and the fluidity of cell membrane lipids of tested plant improved. At the same conditions, the proportion of pectin in the radicles of Allium tuberosum L. was increased and the histiocytic water-retaining property was increased.Under the surfactant-treatment of 1.0～5.0 mg-L-1, this also brought many variations on the molecular structures in radicles and sprouts of 3 vegetables, the proportion of hydrogen bonds in protein molecule was decreased and the protein structure was loose, the proportion ofα,β-unsaturated group in ester molecule was decreased and the fluidity of cell membrane lipids of tested plant became inferior gradually, the increase of the proportion of cellulose in the tested plant could prevent cell damage caused by the injury from the tested surfactants.3. The vegetables response mechanism caused from the surfactants was researched through a semiquantitative analysis which detects the ratio of the absorption peak intensity of characteristic functional group to that of methylene at 2926 cm-1 in the same infrared spectra as the relative contents of proteins, carbohydrates and ester in the radicles and sprouts of 3 vegetables. The result showed that the contents of proteins and carbohydrates in the radicles of 3 vegetables were higher than the control groups, the content of ester in the radicles of Brassica rapa L. was higher than the control group. The proteins content, carbohydrates content and ester content in tested seedlings were increased under surfactants stress.4. The effects of surfactants combined with the heavy metal on the vegetables biomass were investigated using pot experiment. The results showed that the low concentrations promote the growth of vegetables(0.5 mg·Kg-1Cd+0.5 mg·Kg-1,25.0～50.0 mg·Kg-1 Cu+0.5 mg·Kg-1), and the high concentrations had adverse effect on the growth of vegetables (5.0-10.0mg·Kg-1Cd+0.5mg·Kg-1,100.0～200.0mg·Kg-1 Cu+50.0mg·Kg-1).The effects of the heavy metals content, the heavy metals migration rate and the elemental forms and the heavy metal content in the soil were investigated by atomic absorption spectrometer with the method of principal component analysis (PCA) to handle the above mentioned indices. The results were as follows:(1) The results of Principal Component Analysis (PCA) showed that the PC1、PC2、PC3 and PC4 were four principal component selected from the multi-factor analysis tested in this study. As a result, under the stress of surfactants-Cd, PC1 means the factor of the distribution of Cd, PC2 means the migration factor of Cd, PC3 means the factor of exchangeable form of Cd, PC4 means the factor of surfactants concentration. Another showed that under the stress of surfactant-Cu, PC1 means the factor of the distribution of Cu, PC2 means the migration factor of Cu bioaccumulation on vegetables, PC3 means the migration factor of Cu, PC4 means the factor of surfactants concentration.(2) The principal component had different effects on the diet safety of vegetables respectively according to the different kinds of surfactants combined with the different kinds of heavy metal. As a result, under the stress of surfactants-Cd the sequence of PC1 Variance % was SDBS>CTMAB>TW-80, the sequence of PC2 Variance% was CTMAB>TW-80>SDBS, the sequence of PC3 Variance % was SDBS>CTMAB>TW-80, the sequence of PC4 Variance % was SDBS>CTMAB>TW-80. Another showed that under the stress of surfactant-Cu the sequence of PC1 contributing rate was CTMAB>SDBS>TW-80, the sequence of PC2 Variance % was CTMAB>SDBS>TW-80, the sequence of PC3 Variance % was TW-80> SDBS> CTMAB, the Variance % of PC4 was very close to each other.(3) Principal component score analysis showed that the transport rate of Cu/Cd from root to leaves and the proportion of exchangeable Cd in soil were increased with surfactants existed in soil. Another showed that SDBS and TW-80 also could promote the tested vegetables to absorb Cu.(4) The edible security of vegetables were evaluated through the application of more comprehensive analysis.The results indicated that Brassica rapa L.Chinensis Group was vulnerable to the threat of the heavy metal pollution in soil. Especially SDBS combined with the heavy metal in soil has a profound influence on edible security of Brassica rapa L.Chinensis Group, and CTMAB combined with the heavy metal in soil brought the most serious threat to the edible security of Allium tuberosum L. and Daucus carrot L.更多还原