【作者】 吴亮红；

【导师】 肖化云；

【作者基本信息】 南昌大学 ， 环境科学， 2010， 硕士

【摘要】 由于长期暴露在人为污染环境下,城市及其周边区域的生态环境相对脆弱,因而大气高N沉降的影响可能尤为显著。为了探讨维管束植物监测大气氮沉降的可行性,研究南昌市大气氮沉降的空间分布以及追溯其大气氮源,本论文测定了南昌市五个功能区的10个采样点155个樟叶样和22个根际土样品的氮含量和氮同位素值以及51个樟树叶片比叶面积和24个樟树叶片叶片面积。通过对不同功能区樟树叶氮含量和氮同位素的对比研究,揭示樟叶氮含量和氮同位素对环境因子和氮沉降变化的响应机制。进而运用不同影响条件下樟叶氮元素含量和氮同位素,并结合樟树叶年龄、樟树叶生长树冠条件以及生长土壤状况,对南昌地区的大气氮沉降进行了详细研究,探讨了樟树叶同位素方法在环境监测和大气氮沉降研究中应用的影响条件,并为城市氮污染的防治提供了地球化学依据,得到了一些有意义的发现和创新点。(1)不同功能区樟树叶氮含量和氮同位素的比较通过对比各个功能区中樟树叶的氮含量,我们发现居民区樟树叶氮含量是各功能区中最低的；除了高速路,其它公路附近樟树叶的氮含量都低于工业区。该结果显示樟树叶氮含量与所在功能区的氮沉降强度变化情况基本一致,维管束植物可以作为大气氮沉降的指示生物。分析各功能区樟树叶的氮同位素值发现,火电厂(-2.59‰-3.57‰)、公路(-4.42‰-3.04‰)、市区居民区(-0.79-2.52‰)等采样点樟树叶的δ15N随叶龄增大而增大,且整体偏正；氨厂采样点樟树叶的δ15N随叶龄增大而降低,且整体偏负(-9.85±0.62‰)；梅岭、前湖采样点樟树叶的δ15N基本不随叶龄发生变化。这可能说明前三者的大气氮沉降主要是燃料燃烧所产生的,与氨厂氮沉降源有本质区别,同时表明利用不同叶龄樟树叶氮同位素间变化规律可以定性分析氮沉降来源。对所有樟树叶样品的δ15N和N%拟合发现无相关性,表明南昌市大气氮沉降来源复杂多样。(2)距污染源不同距离上樟树叶氮含量和氮同位素的空间分布通过对南昌市两典型氮点源(江西氨厂和昌樟高速路)附近樟树叶氮素分析发现,樟树叶氮含量与距排放源距离关系密切,樟树叶氮含量随距离的增大而降低。氨厂附近樟树叶的δ15N整体偏负,而且其樟树叶的δ15N随距离增大而增大,随树叶年龄的增大而降低,且树底叶片的δ15N要高于树顶。这些结果都表明氨厂附近樟树叶吸收了大气中来自氨厂的大量δ15N偏负的氨。高速路附近樟树叶的δ15N整体偏正(-4.60-3.04%o),且距离公路最近的樟树叶δ15N最偏正,在离公路最远的160m处樟树叶δ15N最偏负,这反映了离公路近的樟树叶吸收了大量的来自公路的偏正的含氮化合物。(3)其它影响因素叶片面积、土壤环境、季节等是影响樟树叶监测大气氮沉降的内因或外因,也可以根据这些影响因子分别了解大气氮沉降情况。分析部分樟树叶面积和比叶面积(SLA)发现：居民区樟树叶样品的SLA低于工业区,平均低6%；梅岭的叶片面积是所有功能区中最高的。表明高污染区植物叶片的SLA要高于低污染区或无污染区；低污染区较高污染区植物叶片面积大。通过分析污染区和非污染区樟树叶与根际土的N%和δ15N,发现各区的N%的相关性显著,而只有非污染区的樟树叶和根际土δ15N相关性显著,这表明污染区氮沉降对樟树叶的生长影响巨大。对梅岭狮子峰脚下春秋季节的樟树叶样品进行分析,分析结果表明,除嫩叶外春季樟树叶氮含量(2.36%)略低于秋季(2.49%),但并没有显著差异(p>0.05)。春季(-0.34±0.23‰)樟树叶氮同位素值显著低于秋季(0.31±0.23‰)(p<0.05),这可能是樟树叶在春季和秋季吸收了不同大气δ15N氮沉降所导致的。关于季节对樟树叶示踪大气氮沉降的影响有待进一步的研究。更多还原

【Abstract】 With the industry economic and other human activities development, atmospheric nitrogen deposition which has caused people’s attention caused a series of ecological damage at city area. In order to discuss the reliability of vascular plants used as biological indicator to monitor atmospheric nitrogen pollution,the spatial distribution of atmospheric nitrogen deposition of Nanchang city and trace atmospheric nitrogen source, this paper packed 155 camphor tree leaves and 22 soil samples in 10 sampling sites of five functional zones in Nanchang city,and measured their nitrogen contents,nitrogen isotope values, specific leaf area and leaf area.By combining plant bionidicator method with isotopic technique, this paper was mainly contrast theirδ15N in camphor tree leaves of different functional zones for indicating environmental conditions and atmospheric N deposition. By investigating factors affecting leaves isotopic signatures, the mechanisms of leaves isotopic responses to environmental factors and N deposition were disccussed. By using elemental contents and isotopes in camphor tree leaves, and combining with other factors,N deposition at Nanchang area was systematically studied.This paper has deepened the application of leaves isotopes for monitoring environment and N deposition, and it has provided geochemical references for the prevention and control of N pollutants at city area. Some significant innovations have been obtained.To contrast N% andδ15N in camphor tree leaves of different functional zones:The tissue nitrogen content of residential area was higher than other functional zones and besides motorway,the tissue N% of traffic zones was less than that of industrial zones.It appeared that where atmospheric nitrogen concentration is high, tissue nitogen content of leaves was also high, indicating vascular plants can be used as bio-indicator to monitor atmospheric nitrogen pollution.The older leaves had moreδ15N than the younger leaves of coal-based power plant (-2.59%o-3.57%o), highway (-4.42%o-3.04%o) and residential area (-0.79-2.52%o). However, Ammonia Plant(-9.85±0.62‰)had the most negativeδ15N, reflecting that vascular plants can be used as bio-indicator to monitor atmospheric nitrogen pollution source. Tissue nitrogen isotope and nitrogen content of leaves showed no correlation in Nanchang city,which also reflected the complexity of nitrogen sources in Nanchang city.To contrast N% andδ15N in camphor tree leaves of points in different distances from nitrogen point source:In Ammonia Plant and motorway area,The tissue nitrogen content in the nearer point to emission source was more than the further points,indicating that the nearer to the emission source,the more serious nitrogen deposition.In Ammonia Plant,the nearer to emission source,the more negativeδ15N in the leaves, and more negativeδ15N in leaves in the tree tops than that in the tree bottoms.It reflected that the negativeδ15N of ammonia were from Ammonia Plant. However, in the motorway area, the nearer to motorway, the more positiveδ15N in the leaves, and the more positveδ15N in leaves in the tree tops than the bottoms,indicating the positiveδ15N of nitrogen-containing compound from vehicles.Some influencing factors of using camphor tree leaves to monitor nitrogen deposition:some influencing factors such as the leaf area,the soil environment and the season were studied to get more information about using camphor tree leaves to monitor nitrogen deposition.It was found that there were larger specific leaf area(LSA) of leaves in industrial areas than that in residential area and the largest area(S) of leaves in Meiling,infecting that leaves in pollution area had larger LSA and smaller S.Tissue nitrogen and soil nitrogen showed a linear correlation y=0.27+5.60 x (R2=0.621,p<0.01)in Nanchang city. However,onlyδ15N of leaves and soil had linear correlation in no-pollution area, insteading of pollution area.It could be due to influence of the pollution atmosphere coming from the pollution area on the leaves.This study analysed leaves of Meiling packed in spring and fall. The analysis showed that there was no significantly difference in tissuse nitrogen content between two seasons,andδ15N of leaves in spring(-0.34±0.23%o) was significantly lower (p<0.05) than that in fall (0.31±0.23%o),possibly owing to the different sources in two seasons,which also needs more evidence.更多还原