【作者】 刘强；

【导师】 刘景双；

【作者基本信息】 中国科学院研究生院（东北地理与农业生态研究所） ， 环境科学， 2014， 博士

【摘要】 随着城市化与工业化的快速发展，城市土地污染在中国逐渐加重。而城市农业用地的质量状况与人体健康关系最为密切。城郊是城市农业的主要农产品产区，而蔬菜又是其中重要的经济作物，因此，城郊蔬菜产地的环境质量不容忽视。土壤重金属因其污染范围广、持续时间长、污染隐蔽性、无法被生物降解，并可能通过食物链不断地在生物体内富集，对食物链中某些生物产生毒害，最终在人体内蓄积而危害健康等特点受到人们广泛关注。研究城郊菜地土壤重金属的空间分布特征及其风险，探讨土壤-蔬菜系统中重金属的累积效应对于确保城郊菜地土壤环境安全及蔬菜清洁生产具有重要的理论与实践意义。本文以吉林省典型城市（长春市、吉林市、松原市、四平市）的郊区菜地为研究对象，通过田间调查、室内分析和盆栽模拟试验，系统的研究了重金属在城郊菜地中的污染分布规律与累积特征，参照土壤环境质量标准进行了蔬菜生产地质量等级划分；并对蔬菜在不同污染条件下以及种植管理模式下重金属的累积规律进行探讨，结合蔬菜产地环境质量等级划分结果指导蔬菜安全生产。主要结果如下：1.摸清了吉林省主要城市郊区菜地重金属污染状况与空间分布特征。由于人为活动强度和地域的不同，各城市郊区菜地环境质量存在较大差异。其中，长春市、吉林市、四平市以及松原市城郊菜地重金属含量基本都超出吉林省背景值，部分超出国家一级标准，少量样点超出国家二级标准，超标元素以Cd为主。重金属的空间分布受到了自然因素和人为因素的综合影响，热点污染区多集中在工业集中区附近以及盛行风下风向。2.对城郊菜地重金属进行人为源、自然源辨识。以长春市和吉林市为例，采用多元统计分析方法对长春市、吉林市城郊菜地重金属污染源进行分析，结果显示，Pb、Cu、Zn和Cd都倾向于来自人为源，而Cr和Ni主要来自成土母岩。3.对城郊菜地土壤重金属的生物有效性进行评价。以长春市为例，结果显示，城郊菜地可利用态金属浓度呈现较大的变异性，变异系数要大于总量。有些重金属总量虽然不高，但其可利用态重金属会呈现相对较高的浓度，仍会对植物、微生物等构成威胁。4.对城郊菜地土壤环境质量进行评价。利用单因子指数和综合污染指数评价方法对长春市、吉林市、四平市和松原市城郊菜地环境质量进行评价，结果显示，研究区菜地基本处于警戒线、轻污染水平，少数菜地达到了重污染水平。整体上看，Cr和Ni污染相对较轻，受人为干扰较小，Pb、Cu、Zn和Cd污染相对较重，尤其是Cd污染。从综合污染指数空间分布图可知，各城市郊区菜地重金属污染有明显的区域分布特征。5.参照土壤环境质量标准对菜地土壤环境质量进行分类，根据分类标准区划长春市、吉林市、四平市和松原市城郊菜地质量。结果显示，研究区大部分土壤都可作为无公害蔬菜基地使用，部分菜地可作为有机和绿色蔬菜基地使用，有一些菜地土壤进行蔬菜种植前需开展土壤污染风险评估，但没有菜地达到不能用于蔬菜种植的污染程度。6.通过盆栽模拟试验研究了不同收割条件下韭菜对Pb的累积效应。结果显示，同一生长周期内随着韭菜收割次数的增加韭菜根累积Pb的量会出现先降低后增加的趋势，不同Pb污染条件下收割两次的韭菜根中Pb含量均出现了极低值。而韭菜茎中Pb含量随着收割次数的增加呈现上升趋势，在高浓度Pb污染条件下相对于4次收割的韭菜5次收割使得茎内Pb含量略有下降。韭菜可食部分Pb累积量呈现先增加后减小的趋势，在3、4次收割时累积量达到最大。且韭菜可食部分Pb累积浓度和累积量没有随生长时间持续增加，而是不断波动，该结果表明，韭菜吸收累积在可食部分的Pb并不稳定，而是在植株各器官中不断运移。7.通过盆栽模拟试验研究了单一及复合污染条件下菠菜对Pb、Cd的累积效应。土壤Cd添加浓度为0.35mg/kg和1.4mg/kg时，Pb与Cd表现为拮抗作用，Cd抑制了菠菜对Pb的累积；当土壤Cd添加浓度为4.90mg/kg时，Pb与Cd之间的拮抗作用转变为协同作用，Cd促进了菠菜对Pb的吸收。当土壤Pb添加浓度为75mg/kg时，Pb与Cd的复合作用表现为加合作用；当土壤Pb添加浓度为300mg/kg，且土壤Cd含量较高时，Pb开始对菠菜Cd累积产生了一定的抑制了作用；当土壤Pb添加浓度为1050mg/kg时，Pb与Cd之间产生了明显的拮抗作用，即高浓度Pb阻碍了菠菜对Cd的吸收。8.通过盆栽模拟试验研究了小白菜和菠菜在单一种植和混合种植模式下对Cd的累积效应。小白菜在两种种植方式下Cd累积量并没有显著差异，而菠菜呈现了不同的Cd累积规律。在混合种植模式下，菠菜中Cd含量显著高于单一种植，表现为“协同作用”，即在混合种植时小白菜促进了菠菜对Cd的吸收，该现象的出现可能由于小白菜根系分泌物与Cd形成了利于菠菜吸收的螯合物，而且在混合种植时菠菜与小白菜形成了一种竞争，促进了菠菜根系分泌物的产生，通过溶解、螯合、还原等作用活化了土壤重金属，进而增强了对Cd的累积。因此，菠菜和小白菜不适合进行间作，且不同Cd浓度胁迫下，相对于小白菜菠菜都呈现出了较高的Cd累积能力。更多还原

【Abstract】 Due to rapid industrialization and urbanization, contamination of urban soils ison an increase all over China. The quality of urban agricultural land is closely relatedwith the health of the population. The suburb is the main producing area ofagricultural products, and vegetable production in peri-urban areas is now a key sectorof the urban agricultural economy, therefore, the environmental quality of peri-urbanvegetable fields should be paid more attention to all over the world. Among allchemical contaminates, heavy metals are considered potential hazardous contaminantsin the biosphere to human health. This kind of pollution exhibits the followingcharacteristics: wide range, long time with toxicity, invisibility, easily cumulating,transfer along with food chain and hardly resuming etc. The study on the spatialdistribution characteristics and risks of heavy metals in peri-urban vegetable soils is ofgreat significance to soil environment quality and safety in vegetable production.Using peri-urban vegetable plots in four typical cities (Changchun, Jilin, Siping andSongyuan) in Jilin province, the research carried out field survey, lab analysis and potexperiment. The distribution and cumulative effect of heavy metals in peri-urbanvegetable soils are researched systematically. Then the environmental quality ofvegetable fields was classified as four classes based on the soil environmentalstandard, and we thoroughly studied the accumulation rules of heavy metals underdifferent environmental condition and planting patterns. At last, on the basis of theresearch results, we can guide the safe production of vegetables in study area. Themain results of this study are as follows:1. The pollution and spatial distributions of heavy metals in the peri-urban vegetable soils in the major cities of Jilin province were made clear. Due to thedifference of the intensity of the human activities and regional differences, theenvironmental quality of vegetable fields in the cities varied greatly. The heavy metalcontents in most of the peri-urban vegetable fields in Changchun, Jilin, Siping andSongyuan exceeded their background values of Jilin province, some exceeded thenational first standard and little reached to the national secondary standard, and Cdwas the major element. The distribution of heavy metals was constrained by bothnatural and contrived factors, and hotspots were mainly distributed in industryconcentrating area and downwind area of prevailing wind.2. To identify the potential sources of heavy metals in peri-urban vegetable soils.With Changchun and Jilin, for example, the multivariate statistical analysis resultssuggested that Pb, Cu and Zn were consistently from anthropogenic sources, while Crand Ni were from natural sources with low concentrations.3. To estimate the metal availability in peri-urban vegetable soils. WithChangchun city, for example, the results showed that available metal concentrationsshowed large variability and the CV values exceeded those of the total metal forms. Itis clear that though the total metal concentrations are not perceived to be particularlyhigh, the availability of Pb, Cr, Cu, Ni and Zn may present a relatively high level andincrease risk of these metals to accumulate to microbial and plant tissues.4. To evaluate the environmental quality of peri-urban vegetable fields. Singlegene index method and complex pollution indices method were used in this paper toevaluate the environmental quality of peri-urban vegetable fields in Changchun, Jilin,Siping and Songyuan. The environmental quality of most vegetable fields was atguard line and light pollution level, and little fields reached heavily pollution grade.Cr and Ni had relatively low levels of contamination and were less influenced byhumanity. Pb, Cu, Zn and Cd were relatively seriously influenced by anthropogenicactivities, especially for Cd. Spatial distribution of synthetic pollution index inperi-urban vegetable soils indicated that the heavy metal pollution indifferent citiesvaried greatly from regional differences.5. The environmental quality of vegetable fields in Changchun, Jilin, Siping and Songyuan was classified as four classes based on the soil environmental standard.Most of the vegetable fields in study area were non-pollution vegetable productionbases, some fields could be used as organic and green vegetables bases, and few fieldsrequired risk assessment before being used to grow vegetables, but all of the vegetablefields could be used to grow vegetables.6. To study the cumulative effect of Pb in Chinese chives under different cuttingfrequency through pot experiment. Lead concentrations in Chinese chives roots werefirst decreasing and then increasing with the increase of cutting frequency over aperiod of time, and extremely low values occurred under cutting twice. Leadconcentrations in Chinese chives stems were increasing with the increase of cuttingfrequency, Pb concentrations in stems had slight decline when cutting five timesunder high Pb pollution. Lead content in Chinese chives leaves were first increasingand then decreasing with the increase of cutting frequency, and extremely high valuesoccurred under cutting three and four times. The concentration and content of Pb inleaves had not risen with the increase of growth time continued to falter, indicatingthat the Pb in Chinese chives leaves was not stationary and had a continued movementwithin the plant.7. To study the cumulative effect of Pb and Cd in spinach under alone stress andcombined stress through pot experiment. Pb and Cd showed anti-action when the Cdconcentrations in soils were0.35and1.4mg/kg, respectively, indicating that Cd waslimiting Pb absorption. Pb and Cd showed synergy when the Cd concentrations insoils were4.9mg/kg, indicating that Cd was promoting the uptake of Pb by spinach.Pb and Cd showed adding effect when the Pb concentrations in soils were75mg/kg.Pb was limiting Cd absorption when the Pb concentrations in soils were300mg/kg.Pb and Cd showed obvious anti-action when the Pb concentrations in soils were1050mg/kg, indicating that Pb was limiting Cd absorption by spinach.8. To study the cumulative effect of Cd in spinach and pakchoi under singleplanting system and through pot experiment. Pakchoi did not make significantdifference under different planting ways, but pakchoi showed different accumulativerules. The content of Cd in pakchoi under companion planting system was significantly higher than single planting system, indicating that pakchoi waspromoting the uptake of Cd by spinach under companion planting system. Thephenomenon was likely due to that pakchoi root exudates and Cd formed chelate forbetter uptake by spinach, and spinach and pakchoi formed a competition undercompanion planting system, and then promoted the produce of spinach root exudates.The exudates could activate heavy metals by dissolving, chelation and reduction toincrease the accumulation of Cd by spinach, so spinach and pakchoi were unsuitablefor companion planting, and the capacity of accumulating Cd for spinach was strongerthan pakchoi.更多还原