【作者】 丁爱芳；

【导师】 潘根兴；

【作者基本信息】 南京农业大学 ， 土壤学， 2007， 博士

【摘要】 持久性有机污染物(POPS)在环境中的分布及其对人体健康和生态系统的影响已引起了全球性的关注。多环芳烃(PAHs)是一类环境中最为重要的致癌有机污染物。本论文主要以美国环保署(EPA)列为环境优控污染物的16种PAHs为研究对象,探讨其在江苏省部分地区农田土壤中的污染来源、污染程度及其生态风险;从宏观和微域2个方面研究PAHs在土壤剖面和土壤团聚体颗粒组中的分布,探讨PAHs在土壤中的吸附和运移,结果有助于了解PAHs在农田土壤中的归宿与生态环境风险。1、江苏省部分地区农田土壤中16种PAHs的污染程度及来源。江苏省兴化市、吴江市、宜兴市、南京市六合区的农田表层土壤(0～15cm)中16种PAHs总量介于45.6-2286.8μg/kg。兴化市、吴江市土壤中PAHs平均含量分别为1370.3、801.1μg/kg,污染严重;宜兴市、南京市六合区两地土壤中PAHs平均含量分别为210.8、126.7μg/kg,为轻微污染或无污染。根据多环芳烃环数相对丰度、菲(Phe)/蒽(Ant)、荧蒽(Fla)/芘(Pyr)比值和对4地的实际调查表明,研究地区PAHs污染源为多源污染,主要有机动车尾气排放、煤燃烧、草和木材的燃烧、石油泄漏等。因此,农田土壤由于污染来源广泛,潜在环境风险大。2、PAHs在农田土壤剖面中的纵向分布及其影响因素。分析了宜兴市和南京市4个土壤剖面中16种PAHs的总量,发现PAHs总量在土壤剖面的纵向分布总体上是随着土壤深度的加深而降低,在0-30cm土层中PAHs总含量下降剧烈,30cm以下土层中含量低且相对稳定。多环芳烃的单一组分含量也随土壤深度的加深而逐渐降低,在土壤剖面底层主要分布的是低环PAHs(≤3环)。2环的萘和3环的菲在0-80cm土层中都有分布,4环的芘和5环的苯并[a]芘在犁底层以下含量较少甚至检测不到。PAHs在农田土壤剖面中的纵向分布与土壤有机质的含量与性质、PAHs的疏水性能及人为扰动土壤活动有很大的关系。3、农田土壤团聚体颗粒组中PAHs的分布及其环境意义。以黄泥土、青紫泥、白土等3种农田水稻土为研究对象,测定了土壤团聚颗粒组中16种PAHs的含量。结果表明,供试水稻土不同粒径团聚体颗粒组中PAHs含量分布存在差异,PAHs总含量以＜2μm粒径的颗粒组最高,其次是200～2000μm粒径的颗粒组,PAHs在这2个颗粒组有明显富集现象(富集系数为1.25～3.92);而20～20μm和2～2μm粒径的颗粒组中PAHs含量小于本土,呈现亏缺现象(富集系数为0.64～0.88)。水稻土这种PAHs的团聚体颗粒组分布格局其环境意义不同,200～200μm粒组中PAHs易重新进行分配,＜2μm粒径的颗粒组中PAHs易在土-水和土-气间发生迁移,具有一定的环境风险。不同粒径团聚体颗粒组中PAHs的含量与其总有机碳(r=0.73,P＜0.01)、腐殖质碳(r=0.81,P＜0.01)、胡敏酸碳(r=0.85,P＜0.01)都呈显著相关,说明不同粒径团聚体颗粒组中有机碳含量控制和影响了PAHs在土壤中的吸附和分配。4、农田土壤中菲含量的动态变化。在水稻土黄泥土中添加0.4～3.2μg/g的菲进行培养,土壤中菲含量随着培养时间的延长而逐渐下降,其下降幅度随着土壤中菲添加量的增加而迅速增大。培养56天后,菲添加浓度为3.2和1.6μg/g的土壤中菲含量下降最快,分别下降了77.0%和65.0%,菲添加浓度为0.8和024μg/g的分别下降了48.3%和25.0%,下降幅度相对较小。这可能是因为添加到土壤中的菲浓度越大,被土壤微生物降解和土壤固定吸附的菲也越多。5、农田土壤中菲污染对土壤酶活性和微生物多样性的影响。在土壤中添加菲进行培养实验的条件下,研究了土壤中酶活性变化及其与菲污染量之间的关系。结果显示,黄泥土中添加菲对土壤脲酶和磷酸酶活性有影响。在1-7天内菲对土壤脲酶活性有抑制作用,与对照相比,添加浓度超过3.2μg/g时抑制作用显著;菲对土壤磷酸酶活性在1-28天内有激活作用,当添加浓度超过1.6μg/g时,土壤磷酸酶活性与对照存在显著差异。在培养的56天中,不同处理的菲污染对过氧化氢酶的活性没有影响。因此,磷酸酶和脲酶都可以作为菲污染土壤的生态毒理指标,敏感诊断期为1-7天,磷酸酶比脲酶更敏感。采用PCR-DGGE分子生物技术对菲含量不同(0.05～1.60μg/g)的水稻土中微生物多样性进行研究,发现土壤在小于1.60μg/g菲污染水平下,没有影响土壤微生物多样性,但在菲污染的土壤中,出现了特有的微生物种,这些特有微生物可能具有降解菲的能力。更多还原

【Abstract】 Persistent organic pollutants(POPs) have been of great concern due to their persistence in the environment,their bioaccumulation potential in the tissues of animals and humans through the food chain,and their toxic properties for human and wildlife.Polycyclic aromatic hydrocarbons(PAHs) are widespread contaminants in the environment.Some of the PAHs proved to be mutagenic,carcinogenic and teratogenic,and are listed as priority pollutants in the U.S.EPA.This study focuses on the contents,distribution,sources and ecological risk of 16 PAHs in soils of farmlands of parts of Jiangsu.The results acquired in this study will make us understand fate and risk of PAHs in soil.1.Contents and sources of 16 PAHs in soils of farmlands in parts of JiangsuContents of PAHs varied widely from 45.6～2286.8μg/kg in studied areas, averaging 1370.3 and 801.1μg/kg,respectively,for samples from Xinghua and Wujiang,signifying severe pollution,and 210.8 and 126.7μg/kg,respectively,for those from Yixing and Nanjing,meaning slight pollution or zero pollution.Based on the relative abundances of PAHs different in ring numbers,the ratios of Phe/Ant, Fla/Pyr and the finding of the site investigation,it was found that PAHs in the soils came from a number of sources,such as exhaust from automotives,combustion of coal,burning of straws and wood,leaking of petroleum,etc.2.Distribution characteristics of PAHs of soil profiles in farmlands and its affecting factorContents of PAHs of soil profiles in Yixing and Nanjing were determined. Concentration of total PAHs and every kind specie peaked at the soil surface and decline with depth,reducing rapidly in 0-30cm and keeping stability below 30cm of soils.Naphthalene and phenanthrene were detected from 0 to 80cm soil profiles, meaning high ability of transplant.Concentration of pyrene and benzo[a]pyrene was found lower than the limit of detection below the plough layer.Contents and characteristic of total organic carton(TOC),the physical and chemical features of PAHs,and human activity played major roles in affecting distribution of PAHs in soil profiles.3.Distrbution characteristic and the environmental significance of PAHs in particle size fractions of soils of farmlandTop soil of three types of paddy soils were studied and contents of PAHs of 16 species both in bulk samples and their particle size fractions were determined.The concentration of the total PAHs varies with the size of the particle fractions,which the order from higher level to lower is in those of＜2μm,200～2000μm,20～200μm and 2～20μm.Compared to that of bulk samples,PAHs are enriched either in the sand-sized or in the clay-sized fractions(with an enrichment ratio of 1.25-3.92) and depleted in the silt-sized fractions(with an enrichment ratio of 0.64-0.88).There is different environmental significance because of distrbution characteristic of PAHs in particle size fractions.Contents of PAHs in 200～2000μm can be distributed again and those in 2μm can be transplanted in soil-water and soil-atmosphere,then there exists environmental risk.There existed a general correlation of the total PAHs content with the contents of soil organic carbon,humus carbon and humis acid carbon respectively.The absorption and distribution of total PAHs in these different size fractions are mainly controlled by organic carbon content.4.The dynamic change of contents of phenanthrene in soils of farmlandThe laboratory incubation of one kind of paddy soils with different concentration of phenanthrene added to soil were studied and found that contents of phenanthrene decreased gradually.Degradation rate of phenanthrene accelerated with its concentration increasing.After incubation for 56d,contents of phenanthrene in paddy soil decreased quickly with 3.2 and 1.6μg/g concentration,the rate being 77.0%and 55.0%respectively,and degradation rate slowly with 0.8 and 0.4μg/g concentration being 48.3%and 25.0%respectively.The reason is that the more contents of phenanthrene added to soil,the more contents biodegraded and absorbed by paddy soil. 5.The effect of phenanthrene in soils of farmland on enzyme activity and microbial diversityThe dynamic changes of soil enzyme activities were researched with incubation experiment under condition of phenanthrene was added to soil.The relationship between enzyme activities and different phenanthrene concentrations were studied. The results showed that there is influence of phenanthrene in soil on urase and phosphotase.Compared to CK,urease activity was inhibited within 7 day under condition of phenanthrene concentration＞3.2μg/g.However,the activity of phosphatase was activated by phenanthrene from 1day to 28 days under condition of phenanthrene concentration＞1.6μg/g.There is no significant change of catalase activity in the phenanthrene with range of 0.4 to 3.2μg/g in the period of 56 day.It was concluded that soil urease activity and phosphatase activity may be considered as diagnoses indicators of soil contamination with phenanthrene,and the most sensitive period of the diagnoses was from the first day to the seventh day after phenanthrene contamination.Phosphotase activity is more sensitive.Molecular technique of PCR-DGGE on different types of paddy soils with different contents of phenanthrene(0.05～1.60μg/g) was used to study microbial gene diversity.The results indicated that microbial gene diversity did not change under condition of phenanthrene concentration≤1.60μg/g.However,there existed special gene diversity which can degrade phenanthrene in polluted soils.更多还原