【作者】 柳林；

【导师】 陈振楼；

【作者基本信息】 华东师范大学 ， 环境科学， 2016， 博士

【摘要】 近年来全球变暖的趋势得到了广泛的关注,环境中碳氮的元素循环也成为了研究的热点。自然湿地由于面积巨大且具有显著的碳汇和脱氮作用而在全球变化研究中具有重要的地位。长江口作为世界上最重要的河口之一,在区域碳氮元素循环的控制中具有重要的作用,研究长江口的碳汇和脱氮作用以及植被对该作用的影响已经成为一个重要研究方向和研究热点。在本研究中,主要开展了以下四方面的工作。1、在长江口崇明东滩区域对沉积物进行采样,分析了不同植被类型下沉积物中有机碳(SOC)含量随深度和时间的变化规律,并与本课题组前期积累成果进行比较研究；2、在崇明岛的农田区域进行土壤采样,分析不同耕作制度下土壤中有机碳含量的变化；3、在崇明东滩的海三棱蔗草区域进行长石粉实验和埋管实验,研究该区域沉积物短期沉积速率和沉积后植被对于不同深度沉积物有机碳含量的影响,并结合13C同位素来判别该区域沉积物中有机碳的来源；4、在长江口的潮滩选择典型植被区域进行采样,研究了沉积物的反硝化脱氮作用,分析了不同植被类型下沉积物反硝化速率的时间和空间变化及环境因子对反硝化速率的影响,估算了长江口潮间带沉积物对上覆水体的脱氮能力以及对河口水源地氮负荷去除能力。取得了以下主要结论：(1)长江河口湿地潮间带的植被区域面积与年份具有一定的相关关系,主要与长江年输沙量存在显著的相关关系；采用长石粉标记法测定潮滩平均沉积速率为11.6 cm/yr。崇明东滩植被区碳存储量达到5.70×104t/yr,碳埋藏通量为1.09kgC/m2/yr,具有显著的碳汇效应。(2)在崇明岛东部地区,土壤和沉积物中有机碳的含量呈现从中部核心地区向四周地区逐渐降低的马鞍状变化趋势,特别是在东部地区中心的农田区域出现土壤有机碳含量的峰值,而在崇明东滩的光滩地带出现有机碳含量的低值；同时,水田耕作部分含量也要显著高于旱作蔬菜地,而在潮间带区域随着植被类型(芦苇/互花米草——海三棱蔗草/互花米草——光滩)的更迭,潮间带沉积物中有机碳含量逐渐降低,至光滩含量最低。(3)近年来,海三棱蔗草群落和光滩表层沉积物中有机碳年平均含量基本上呈现随年份增加含量上升的变化趋势,具有明显的累积效应。崇明东滩各不同植物群落表层沉积物中有机碳含量具有明显的差异,其中光滩最低,而互花米草最高；各植被类型沉积物中的有机碳含量呈现随深度的增加而降低,有机碳的最大值往往出现在表层0-5 cm的沉积物中；在各季节,三种植被类型下沉积物中有机碳均呈现出夏季含量较低,而秋冬春季节较高的变化趋势。(4)2011年海三棱蔗草带沉积物中有机碳平均含量要显著高于2004年该植被类型下沉积物中的含量,随时间的变化规律基本一致；0-60 cm深度沉积物中有机碳含量呈现波动变化趋势,但整体呈现随深度增加含量降低的变化趋势；崇明东滩沉积物各月柱样的有机碳含量变化在海三棱藤草的生长期变化显著。(5)埋管实验的结果很好说明了海三棱蔗草对沉积物有机碳的影响；采用同位素方法发现崇明东滩沉积物中有机碳的来源为江水携带来的颗粒物和本地植被生长,外源泥沙和悬浮物堆积埋藏是长江口潮间带湿地沉积物有机碳库的主要来源,但海三棱蔗草产生的有机碳作为内源输入也占有一定比重。在丰水期海三棱蔗草输入的有机碳为0.65 mg/g,内源贡献率为7.35%,而在枯水期海三棱蔗草输入的有机碳为2.06 mg/g,贡献率上升至31.20%。(6)长江口潮滩湿地0～10cm深度沉积物反硝化速率为043～415.8 μmol·m-2·h-1,平均值为35.5μmol·m-2·h-1,在世界范围内河口区域基本上处于中等水平。光滩沉积物平均反硝化速率为16.2μmol·m-2·h-1,植被带沉积物平均反硝化速率为45.2μmol·m-2·h-1,青草沙水源地库区总脱氮能力达到2.00×108g N每年,可以有效去除大气沉降输入的氮负荷,对控制库区水体氮累积和富营养化具有重要意义。(7)海三棱蔗草带沉积物反硝化速率与芦苇带、光滩间均存在着极显著的差异(p<0.01),而芦苇和光滩间不存在显著的差异(p>0.05)。虽然部分点位沉积物反硝化速率发现具有显著的季节差异(p<0.05),但在长江口各点没有发现一致的沉积物反硝化速率时间变化规律；在深度上基本上呈现随深度增加反硝化速率有降低的趋势,长江口区域沉积物表层部分反硝化速率多高于较深深度的沉积物；长江口沉积物反硝化速率受区域、深度和月份等因素的综合影响显著,但反硝化速率与沉积物理化性质、温度等单一环境因素均不具有显著性相关关系。(8)本研究表明长江口潮间带湿地具有明显的碳汇和脱氮等环境效应,在相对海平面上升与长江来沙减少的背景下,建议加强河口湿地保护,降低围垦强度,建立湿地系统监测系统和基础数据的共享机制,在加强科学研究的基础上,尽快将湿地纳入中国碳排放权交易清单。同时在条件成熟时,在污染物排放总量控制实施中适时引入氮排放权交易制度。更多还原

【Abstract】 In the past few years, the global warming trend has been widely concerned. The cycling of carbon and nitrogen in the ecosystems has become a research hot spot. Natural wetland occupies an important position in global change due to the large area and the role as carbon sink and denitrification. As one of the world’s most important estuary, the Yangtze River Estuary acts a significant part in the control of carbon and nitrogen cycling in this region. It has become a widely acknowledged research direction to study the carbon sink function, denitrification, and the influence of vegetation on denitrification of Yangtze River Estuary.In this study, we carried out the following works:1.Collected sediment samples in Chongming Dongtan of Yangtze River Estuary, and analyzed the variation of soil organic carbon (SOC) content in different vegetation types with depth and time and compared with the results of previous tudies of our team; 2. Collected soil samples in the farmland area of Chongming Island, and analyzed the variation of SOC content under different cropping system; 3. Feldspar powder was sprinkled on the sediment and pipes were buried in Scirpus mariqueter growth area in Chongming Dongtan, to study the sedimentation rate and the effect of vegetation on SOC content in different depth, and analyze the source of SOC in the region using 13C isotope; 4. Selected typical vegetation regions in Yangtze River Estuary wetland and collected sediment samples to study the denitrification, analyzed the spatio-temportal difference of sediment denitrification rate in different vegetation types and the effects of environmental factors, and estimated the ability of intertidal sediments to remove nitrogen from the overlying water and the water source in Yangtze River Estuary. The major conclusions are as the following:(1) Vegetation area along the Yangtze River Estuary wetland intertidal zone had a certain relationship with the year, and it was significantly correlated with annual sediment discharge. Average sedimentation rate in this region was 11.6 cm/yr, measured by the feldspar powder labeling method. The annual carbon storage in the vegetation area of Chongming Dongtan reached 5.70×104t/yr, and the buried carbon flux was 1.09 kgC/m2/yr, which represented the significant carbon sink effect.(2) In the eastern of Chongming Island, the SOC content in the soil and sediment decreased from the central region to the surrounding areas, just like a saddle trend. It was especially high in the central farmland region and lowest in mudflat of Chongming Dongtan. In addition, the SOC content in paddy cultivation area was significantly higher than in dry vegetable area. In the intertidal zone, SOC content in the sediment gradually decreased with the change of vegetation types(Phragmites/ Spartina alterniflora-Scirpusmariqueter/ Spartina alterniflora-mudflat), which was lowest in the mudflat.(3) In recent years, the annual average SOC content increased with the year that’s in the Scirpus mariqueter community sediment and mudflat surface sediment. There was obvious difference of SOC content in the surface sediment between various vegetation communities, which was lowest in the mudflat, and highest in Spartina alterniflora area. The SOC contents of all the vegetation communities decreased with the depth, the maximum SOC often appears in the surface 0-5 cm sediments. From the seasonal variation, the SOC contents of all the vegetation communities was lower in summer, and higher in the autumn, winter and spring.(4) The average SOC content in Scirpusmariqueter sediment was significantly higher in 2011 than in 2004, but the seasonal variations were basically identical. SOC content fluctuated from 0 cm to 60 cm in the depth, but it showed a trend of decreasing from the top to the bottom on the whole. The SOC content in the sediment that collected every month in Chongming Dongtan varied greatly in Scirpus mariqueter growing season.(5) The results of pipe burying experiment well illustrated the influence of Scirpus mariqueter on SOC. It was found through isotope tracer method that the source of SOC in sediment of Chongming Dongtan was the particulate matter carried by river and the local vegetation growth. Exogenous particles sedimentation was the main source of the sediment carbon library in Yangtze River Estuary wetland. The input rate of SOC from Scirpus mariqueter as endogenous contribution also occupied a certain proportion. It was 0.65 mg/g and 2.06 mg/g in the flood season and dry season, respectively, which accounted for 7.35% and 31.20% of the SOC library approximately.(6) The denitrification rate in the surface sediment (0-10 cm) in Yangtze River Estuary wetland was 0.43-415.8 μmol·m-2·h-1, with an average of 35.5μmol·m-2·h-1. It was in the middle level when compared with most estuaries around the world. The average denitrification rates were 16.2 μmol·m-2·h-1 and 45.2 μmol·m-2·h-1 in mudflat sediment and vegetation area sediment, respectively. The annual total denitrification in Qingcaosha reservoir zone reached 2.00×108 g N, which effectively removed the nitrogen input from atmospheric deposition. It’s of great significance for controlling of the nitrogen accumulation in water and eutrophication in the reservoir.(7) Denitrification rate in Scirpus mariqueter had significantly difference with them in Phragmites and mudflat (p<0.01), but there was no significant difference between in Phragmites and mudflat sediment (p>0.05). In the Yangtze River Estuary wetland, the denitrification rates in sediment didn’t show consistent time-varying pattern for all sites, although significant seasonal difference was found in some of them (p<0.05). The denitrification rate in the surface sedimentwas generally higher than the deeper. The denitrification rate in the sediment was significantly influenced by sampling sites, depth and month, but it had no correlation with single physicochemical properties of sediment, temperature and other environmental factors.(8) In this study, we demonstrated that intertidal zone of the Yangtze River estuary wetland has obvious ecological environment effect such as carbon sinks and removing the nitrogen. Under the background of relative sea level rise and decline in riverine sediment supply, it suggested that we should foster weland protection, reduce the intensity of land reclamation, and establish a wetland system monitoring system and the basic data sharing mechanism. On the basis of strengthening scientific research, wetland should be included into China’s carbon emissions trading list as soon as possible. At the same time, once conditions get mature, nitrogen emissions trading system should also be introduced into the apply of total amount control of pollutant discharge.更多还原