【作者】 姚东京；

【导师】 贺宝根； 温家洪；

【作者基本信息】 上海师范大学 ， 自然地理学， 2009， 硕士

【摘要】 河口潮滩是海陆交互作用的重要环境界面,其水动力作用强烈、泥沙输移和冲淤变化复杂、生物多样丰富,具有独特的环境功能和生态价值,尤其在清除河口陆源氮污染方面起着十分重要的作用。长江口滨岸带人口密集、城市化进程迅速,尤其是近20a来,经济快速增长伴随的巨大开发强度,严重影响了长江口滨岸潮滩环境系统内部物质的自然循环过程,对河口潮滩生态系统及近岸水体环境造成了直接和潜在的危害。开展长江口滨岸潮滩氮、磷营养盐的生物地球化学循环研究,具有全球性环境学意义,为滨岸潮滩可持续发展和保护提供科学依据。在国家自然科学基金项目“长江口崇明东滩高潮滩盐沼水—沉积物—植物界面泥沙输移机制研究”(编号:40571012)和河口海岸国家重点实验室开放基金项目“崇明东滩生源要素在潮流作用下输移过程”(编号:SKLEC0510)支撑下,于2007年春季(5月)和2007年夏季(7、8月)在崇明东滩盐沼前缘带进行野外监测和样品采集,系统研究了该区域上覆水氮、磷营养盐潮周期变化和大小潮周期变化及其时空变化特征,并探讨了水环境因子和水动力条件——流速对氮、磷营养盐的影响机制,取得了以下主要成果:崇明东滩盐沼前缘带上覆水溶解态总无机氮(DIN)浓度平均值达到4.86mg·L-1。个别潮汐中三态氮含量高达9.79mg·L-1(NH4+-N)、3.02mg·L-1(NO2--N)和9.15mg·L-1(NO3--N)。春季三态氮比为NO3--N: NH4+-N: NO2--N = 11: 1.6: 1,夏季三态氮比为NO3--N: NH4+-N: NO2--N = 14: 4: 1,显然NH4+-N在夏季时占溶解态无机氮的比例有所提高。TDP的浓度介于0.000~0.374mg·L-1之间,平均浓度为0.056mg·L-1。崇明东滩盐沼前缘带上覆水三态氮、DIN和TDP浓度在整个潮周期变化过程中不具有明显的分层现象。三态氮、DIN和TDP浓度在垂向上的变化较为复杂,大潮时其垂向浓度变化没有一致性,且在潮平阶段其波动性表现的更为复杂和剧烈;小潮时,随着潮位降低其垂向浓度变化越来越趋于简单,甚至其垂向浓度趋于相同。崇明东滩盐沼前缘带上覆水不同潮汐三态氮、DIN和TDP浓度潮周期变化不存在一致性。三态氮、DIN和TDP在潮周期变化过程中出现“单峰型”和“双峰型”的变化过程,甚至在个别潮汐出现“多峰型”变化,且大多数潮汐无机氮在涨潮阶段和落潮阶段均出现极大值。崇明东滩盐沼前缘带上覆水三态氮、DIN和TDP浓度大小潮周期变化表现为:NO2--N的大小潮周期变化在盐沼区和光滩区变化趋势基本一致;NO3--N大小潮周期变化均具有增加的变化趋势;DIN的大小潮周期变化在盐沼区和光滩区具有明显的差异性;NH4+-N和TDP大小潮周期变化均具有明显波动减少的变化趋势,光滩区减少的速率比盐沼区的快,且光滩区的波动强度高于盐沼区。崇明东滩盐沼前缘带上覆水三态氮、DIN和TDP时空分异明显。盐沼区夏季NH4+-N、NO3--N、DIN和TDP平均浓度高于春季相对应潮汐的浓度;NO2--N则恰好相反,表现为春季高于夏季;三态氮、DIN和TDP的潮周期变化表现出较大的差异性,其中TDP潮周期变化幅度表现为夏季强于春季,随着潮位逐渐减少,二者之间的差异也逐渐减少。盐沼区和光滩区NH4+-N、NO3--N和DIN平均浓度在各个潮汐间的差异表现非常复杂,NO2--N和TDP基本上表现为光滩区大于盐沼区或相差不大。盐沼区和光滩区的三态氮、DIN和TDP的潮周期变化存在差异,其中TDP潮周期变化范围相对较小。相关分析表明,崇明东滩盐沼前缘带水环境因子(温度、盐度、电导率、pH、溶解氧、悬沙浓度和悬沙粒径等)对上覆水三态氮、DIN和TDP的影响大多不具有直接的作用,但是在2007年5月18日夜潮盐度和电导率分别与NH4+-N呈显著正相关,即NH4+-N随着盐度和电导率增加而增加。在个别潮汐中,流速与氮、磷营养盐变化呈显著性相关,其余潮汐流速对三态氮、DIN和TDP浓度在沉积物—水界面氮、磷营养盐迁移和转化及水平输移的影响存在较为复杂的关系。潮汐的涨潮阶段、潮平阶段、落潮阶段及潮平均流速与三态氮、DIN和TDP均没有显著性相关。潮汐平均流速与NO2--N变异系数呈显著正相关,潮汐平均流速越大,NO2--N潮周期波动性越大。更多还原

【Abstract】 The estuarine tidal flat is widely identified as an important interface between land and sea, the environmental functions and ecological values of which are unique because of its powerful tidal and riverine hydrodynamic processes, frequent sediment transportation and various organism species, especially known as a natural barrier in purifying terrigenous nitrogen input. Yangtze estuarine littoral zone is densely polluted with fast development of urbanization. Especially in recent two decades, rapid economic growth accompanied by tremendous development has gravely affected the progress of natural circle in the entrails material of Yangtze estuarine environmental system, causing direct and potential hazards to estuarine tidal flat ecosystem and water environment. Thus, it is meaningful to carry out the research on the biology geochemistry cycle of nitrogen and phosphorus nutrients.Supported by National Nature Foundation of China(NO. 40571012) and Open foundation of State Key Laboratory of Estuarine and Coastal Research(NO. SKLEC0510), we did scientific surveys and collected samples in the margin of Chong Ming salt marsh in spring (May) and summer (July and August), 2007. We studied the nitrogen and phosphorus nutrients characters of tidal cycle variation, variation between spring tides and neap tides and spatio-temporal tides. We also discussed how the water environment factors and the hydrodynamic factors (velocity) did an impact on nitrogen and phosphorus nutrients. Several major conclusions are concluded as follows:The average of dissolved inorganic nitrogen(DIN) concentration was 4.86mg·L-1 in the margin of Chong Ming salt mash. In some badly contaminated stations, the ammonia, nitrite, nitrate concentrations reached 9.79mg·L-1,3.02mg·L-1 and 9.15mg·L-1 respectively. In spring, the ratio of NO3--N: NH4+-N: NO2--N was 11: 1.6: 1. In summer, the ratio of NO3--N: NH4+-N: NO2--N was 14:4:1. It’s obvious that the ammonia concentration in summer was higher than that in spring. The Dissolved total phosphorous(TDP) concentration varied from 0.000 to 0.374mg·L-1, with an average TDP concentration of 0.056mg·L-1.On all accounts, there existed no obvious delamination phenomenon in nitrogen and phosphorus nutrients concentration throughout tides. The vertical variation of nitrogen and phosphorus nutrients concentration was complex. In spring tides (water height exceeded 0.7m), there were no coherence variation in vertical direction, with a more complex and severe fluctuation in the middle tides. In neap (water height was lower than 0.7m), the lower the tides were, the simpler the variation was, even the concentration tended to be the same.There was no tidal cycle variation coherence in different tides. Concentration variation curves of nitrogen and phosphorous nutrients shaped single-peak or bimodal. In some tides, even multi-peak occurred. The maximum nitrogen concentration always appeared in flood tide and ebb tide period in most tides。In the period of observation, with tides subrogation, nitrite concentration variation was almost the same in margin of salt marsh with that of the bald field. nitrate concentration varied with gradual incresed fluctuation. DIN concentration variation varied rather differently. Ammonium concentration varied with gradual reduced fluctuation, so did TDP concentration. However, with the TDP concentration, the slope of reduction in bare flat was quicker than that of salt marsh and the fluctuation in bare flat was more intense than salt marsh too.There were apparent spatio-temporal variation of nitrogen and phosphorus nutrients concentration in Chong Ming slat marsh. Nitrogen and phosphorous nutrients concentration in summer was higher than that in spring in salt marsh, but nitrite was just the opposite. The tidal variation of nitrogen and phosphorous nutrients concentration showed much difference between spring and summer in salt marsh. Take TDP as an example, the range of tidal variation in summer was more severe than that in spring, and the range became smaller and smaller with the tides drawdown. The otherness of ammonium, nitrate and TIN between salt marsh and bare flat was complicated in summer, and nitrate and TDP concentration in bare flat was higher than that in salt marsh or in the same level. The tidal variation of nitrogen and phosphorous nutrients between salt marsh and bare flat was also different, but the range of TDP variation changed in a relatively small scope.The linear relationship between nitrogen and phosphorous nutrients and water environment factors (such as water temperature, salinity, electrical conductivity, pH, dissolved oxygen, suspended sediment concentration, suspended sediment grain-size, and so on) indicated that water environment factors had no direct impact on them. However, on the night on 18th May, 2007, there was positive correlation between ammonium and salinity and electrical conductivity respectively, which meant ammonium increased with the raise of salinity and electrical conductivity.DIN and TDP had a linear correlation with velocity in some tides, but it was quite complex with how velocity had impacted on nitrogen and phosphorous nutrients in sediment–water interface when they transferred and transformed or transported between salt marsh and bare flat in most tides. The flood tide, middle tide, ebb tide and average velocity had no direct impact on nitrogen and phosphorous nutrients. The variation coefficient of nitrate had a linear positive correlation with average velocity. The higher velocity was, the more severe the fluctuant nitrate variation was.更多还原