干湿交替驱动下沉积物—水界面N形态的变化规律

发布时间：2018-03-12 20:22

本文选题：东洞庭湖　切入点：洲滩湿地　出处：《中国环境科学研究院》2017年硕士论文　论文类型：学位论文

【摘要】：湖泊的洲滩湿地由于季节性水位变化,处于淹没和出露交替(干湿交替)的状态,进而影响沉积物和上覆水中氮的形态分布,从而影响湖泊的水质和营养状态。为探究干湿交替影响下洲滩湿地沉积物-水界面各个形态氮的变化规律,识别干湿交替区域氮素营养的迁移转化主要影响因素,为湖泊的区域保护提供理论依据,本文选取了洞庭湖受人类活动影响较小的东洞庭湖洲滩湿地作为研究区域,对枯水期、平水期各研究区域从陆域到水域(岸上点位、交界处点位、水下点位)的洲滩湿地沉积物进行了采样调查。通过对洲滩湿地氮形态等指标进行分析后,得到了洞庭湖洲滩湿地沉积物的基本性质,并对洞庭湖洲滩湿地沉积物中氮形态在干湿交替驱动下的变化情况有了初步推断;在此基础上通过室内模拟实验,探寻沉积物-水界面中氮形态在水位变化下的迁移转化规律。通过对洲滩湿地沉积物的野外实地调查研究结果表明,枯水期洲滩湿地沉积物中总氮的平均值为0.920g/kg,变异系数为0.335;硝氮的平均值为1.379mg/kg,变异系数为1.036;氨氮平均值为10.506mg/kg,变异系数为0.861。在平水期洲滩湿地沉积物中总氮的平均值为1.084g/kg,变异系数为0.230;硝氮的平均值为3.141mg/kg,变异系数为1.797;氨氮平均值为15.397mg/kg,变异系数为0.843。平水期总氮、硝氮及氨氮的平均值和枯水期相比都有所增大,除了硝氮的变异系数显著增大外,总氮、氨氮的变异系数都有不同程度地减小。分别对枯水期和平水期的各变量作Pearson相关性分析,在枯水期,含水率与粉粒呈显著正相关(r=0.296,p0.05),在平水期,含水率与黏粒呈极显著负相关(r=-0.466,p0.01)。表明在枯水期时,沉积物中水分主要与粉粒结合,在平水期时,沉积物含水率越高越容易造成黏粒的流失。含水率在平水期与氨氮呈正相关,与硝氮呈负相关,在枯水期时,含水率与这些变量均没有显著相关性。这表明含水率对氮形态的影响在不同水期是不同的。在两个水期中总氮与硝氮均显著正相关(r=0.420,p0.05;r=0.389,p0.05)。在枯水期时,总氮与黏粒、粉粒呈正相关,与砂粒呈负相关;在平水期时,总氮与黏粒呈正相关。表明总氮尤其是有机氮主要赋存在黏粉粒中。以覆水状态对样品进行分组,分为岸上样品和水下样品两组,进行非参数检验发现,在枯水期时含水率、氨氮、总氮均有极显著的差异性,而在平水期时含水率、硝氮有着极显著的差异性。不同水情下的覆水状态对沉积物中氮形态的影响不同,平水期沉积物的生物活性较强,有助于氮的形态转化,平水期的总氮、硝氮、氨氮等指标的平均值都大于枯水期。覆水后沉积物中总氮、氨氮的变异系数减小,空间差异性缩小;但覆水后沉积物中硝氮的变异系数增大,空间差异性增大。室内模拟在不同水位变化速率下,沉积物中氮形态的迁移转化,模拟的水位变化速率分别为8cm/d、2.6cm/d及1.3cm/d(A-5、A-15及A-30)。模拟结果表明:沉积物在经历出露期再覆水后,上覆水中的无机氮在第一周会迅速增大,然后开始缓慢下降;在模拟的水位变化速率下,上覆水中的氮素均以硝态氮为主,所占比例从大到小依次为硝氮氨氮亚硝氮,且随着水位变化速率的减慢,上覆水中总氮、硝氮和亚硝氮逐渐增大,氨氮没有变化;沉积物中的氮素以有机氮为主,无机氮中以铵态氮为主,所占比例从大到小依次为氨氮硝氮亚硝氮,且随着水位变化速率的减慢,沉积物中铵态氮逐渐增多,硝态氮逐渐减小;温度、pH、DO(沉积物中为温度、pH、ORP)作为重要的理化参数对上覆水(沉积物)中的氮形态的迁移转化产生重要影响。在一定范围内,温度的升高对硝化作用有强烈的促进作用,碱性环境有利于氨氧化作用的进行,而氨氧化作用会使环境中的pH降低,DO和ORP直接决定了环境中氮素的好氧转化和厌氧转化;在A-5(水位变化速率为8 cm/d)中,沉积物中的氮素以铵态氮的形式迅速向上覆水中迁移,氨氧化作用迅速且强烈。在A-15(水位变化速率为2.6cm/d)中,在淹水初期沉积物中的TDN(溶解性总氮)大量向上覆水中释放,随后由于上覆水DO的消耗,上覆水中的氨氮逐渐又被沉积物吸附。在A-30(水位变化速率为1.3 cm/d)中,覆水三周后,上覆水中的所有氮素几乎都已硝态氮的形式存在。
[Abstract]:The lake wetland due to seasonal changes in the water level, flooded and exposed alternately (alternating wet and dry state, thereby affecting) distribution of sediment and overlying water nitrogen, thus affecting the lake water quality and the nutritional status. As the change law of water interface to the various forms of nitrogen on alternating wet and dry under the influence of wetland sediment - identification, alternate migration regional nitrogen nutrition into the main factors, and provide a theoretical basis for the protection of the lake area, the Dongting Lake is affected by human activities the smaller East Dongting Lake wetland as the research area, the research area of the dry season, water from land to water (shore point, junction point a water point) bottomland wetland sediments were sampled. Through the analysis of the wetland nitrogen and other indicators, the sediments of Dongting Lake wetland basic Nature, and nitrogen forms on Dongting Lake wetland sediments have concluded that changes in driving under the drying wetting; on the basis of the indoor simulation experiment, to explore the sediment water interface in the form of nitrogen migration in the water level change and transformation law. Through the study of field investigation in the wet sediments on the results show that the average the value of dry season in wetland sediment total nitrogen was 0.920g/kg, the coefficient of variation was 0.335; the average value of nitrate nitrogen was 1.379mg/kg, the coefficient of variation was 1.036; the average value of ammonia nitrogen is 10.506mg/kg, the coefficient of variation is the average value of 0.861. in water and wetland sediment total nitrogen was 1.084g/kg, the coefficient of variation was 0.230; average value the nitrate nitrogen is 3.141mg/kg, the coefficient of variation was 1.797; the average value of ammonia nitrogen is 15.397mg/kg, the coefficient of variation for total nitrogen 0.843. nitrate nitrogen and ammonia water, the average and the dry season are compared In addition to the increase of the coefficient of variation of nitrate nitrogen increased significantly, the total nitrogen, the coefficient of variation of ammonia nitrogen with different degree decreased respectively. The variables of the common water period and low water period for Pearson correlation analysis, in the dry season, water content and powder had a significant positive correlation (r=0.296, P0.05), in the flat water period, the water content and the clay was negatively correlated (r=-0.466, P0.01). The results indicated that in the dry season, the main water sediment in combination with powder, in water, sediment water content is likely to cause the loss of clay. The moisture content in water and nitrogen were positively correlated with negative correlation with nitrate, in the dry season, water content and these variables were not significant correlation. It is shown that the influence of water content on nitrogen in different water periods is different. In total nitrogen and nitrate nitrogen in two water seasons were significantly correlated (r=0.420, P0.05; r=0.389, P0.05). During the dry season, and total nitrogen Clay and silt are positively correlated, negatively correlated with sand; in water, total nitrogen and clay showed that the total nitrogen content positively. Especially in the presence of organic nitrogen mainly occurs in clay particle. The samples were grouped by state of overlying water, divided into shore under water samples and samples of two groups were non parametric test showed that in the dry season when water content, ammonia nitrogen, total nitrogen had extremely significant difference, while in the normal water period when water content, nitrate nitrogen has a very significant difference. The overlying water state and different water under different influence on nitrogen speciation in sediment, water sediment biological live strong, contribute to the transformation of nitrogen, total nitrogen level, nitrogen water period, the average value of ammonia and other indicators are greater than in dry season. Total nitrogen in overlying water after sediments, reduce the coefficient of variation of ammonia nitrogen, spatial difference decreased; but the coefficient of variation of nitrate nitrogen in sediments increased after water covered the spatial difference, room increases. In the simulation of changes in the rate of migration under different water levels, nitrogen forms in the sediments of transformation, the rate of change of the water level simulation are respectively 8cm/d, 2.6cm/d and 1.3cm/d (A-5, A-15 and A-30). The simulation results show that the sediments after exposed period overlying water, inorganic nitrogen in overlying water will increase rapidly in the first week and then began to slow down; in the simulation of water level change rate, nitrogen in overlying water were dominated by nitrate nitrogen, the proportion is from big to small in turn Ammonia Nitrate Nitrite, and with the change of water level rate slowed down, the total nitrogen in the overlying water, nitrate nitrogen and nitrite nitrogen increased gradually no change, ammonia nitrogen; nitrogen in sediments with organic nitrogen and inorganic nitrogen in ammonium nitrogen, the proportion is from big to small in turn Ammonia Nitrate Nitrite, and as the water level change rate decreased in the sediments of ammonium nitrogen gradually increased, nitrate nitrogen decreased gradually; Temperature, pH, DO (temperature, sediments pH, ORP) as the important physicochemical parameters of overlying water (sediments) in the migration of nitrogen forms affect transformation. In a certain range, temperature has a strong effect on nitrification, alkaline environment favorable for ammonia oxidation the ammonia oxidation will make the environment in lower pH, DO and ORP directly determines the environment of nitrogen in the aerobic and anaerobic conversion transformation; in A-5 (water level change rate is 8 cm/d), nitrogen in sediments with ammonium nitrogen form rapidly to overlying water migration, ammonia oxidation quickly and strongly. In A-15 (water level change rate of 2.6cm/d), at the beginning of waterlogging in the sediments of TDN (total dissolved nitrogen) to the overlying water release, then the DO of the overlying water consumption of ammonia nitrogen in overlying water and sediment adsorption gradually. In A-30 (water level change rate is 1.3 In cm/d), after three weeks of water coating, almost all nitrogen in the overlying water existed in the form of nitrate nitrogen.

【学位授予单位】：中国环境科学研究院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：X524

【参考文献】