长江口—东海内陆架磷的生物地球化学过程研究

发布时间：2018-03-22 16:13

本文选题：长江口-东海内陆架　切入点：磷　出处：《中国海洋大学》2015年博士论文　论文类型：学位论文

【摘要】：大河河口及大河影响下的陆架边缘海磷的生物地球化学过程是海洋磷循环的重要组成部分。本论文以长江口-东海内陆架为主要研究海域,采用现场调查与实验室模拟相结合的方法,借助颗粒物分级的手段,结合颗粒物粒度组成、比表面积(Specific surface area, SSA)、矿物组成、有机碳及其稳定同位素和磷酸盐中的氧同位素等多种参数,对水体、颗粒物、沉积物及间隙水中磷的形态分布、混合行为和迁移转化规律进行了较为系统的研究,以期加深对长江口-东海内陆架磷的生物地球化学过程的理解,丰富对高浑浊河口生源要素的生物地球化学循环的认识。获得的主要结果如下：1.沿长江口盐度梯度采集了表层水和悬浮颗粒物样品(2011年6月),对溶解磷和颗粒磷形态的分布、混合行为及迁移转化进行了研究。用水淘选法将颗粒物分为5个粒级,用改进的SEDEX (sequential extraction method)方法对不同形态的颗粒磷进行分析测定,发现不同形态磷之间、尤其是溶解磷和活性颗粒磷形态即可交换态磷(Exchangeable-P, Ex-P)、有机磷(Organic-P, Or-P)和铁结合态磷(Fe-bound P, Fe-P)之间存在强烈的相互转化。碎屑磷(Detrital-P,De-P)和Or-P是悬浮颗粒物中含量最为丰富的两种磷形态,分别占了总颗粒磷的43.9%和26.1%。De-P的含量随着颗粒物粒径的增大而升高,而Or-P及其它形态磷的含量随着颗粒物粒径的增大而降低。8μm组分被认为是“真正悬浮”的颗粒物,本研究表明,“真正悬浮”的颗粒物所携带的生物可利用磷(Bioavailable-P, BAP;为Ex-P、Or-P和Fe-P之和)的通量为0.21×104tPyr-1,占总生物可利用磷输送通量的29%。细粒径颗粒物中P/SSA值很低,表明这些颗粒物中磷的保存效率较低。长江口分级悬浮颗粒物中的De-P/SSA和Fe-P/SSA与长江口表层沉积物基本基本相当,Au-P(自生磷灰石磷,Authigenic-P)/SSA和Re-P(难分解有机磷,Refractory-P)/SSA从悬浮颗粒物到表层沉积物略有降低,而表层沉积物中Ex-P/SSA和Or-P/SSA显著低于悬浮颗粒物,进一步表明了不同形态的颗粒磷随悬浮颗粒物在河口沉降的过程中具有不同的行为特征。2.测定了沉积物分级样品的颗粒磷形态并用分级的沉积物样品进行吸附动力学实验、吸附特征受盐度影响的实验和等温吸附实验。结果表明,沉积物中De-P的含量最为丰富,其次为Or-P。细粒径沉积物中生物可利用磷的含量远高于砂质沉积物,表明细粒径颗粒物对磷从沉积物向上覆水或周围间隙水的释放发挥着主导作用。对从来自同一采样站位的分级沉积物获得的吸附等温线进行分析发现,不同粒径沉积物对应的零平衡磷酸盐浓度值(zero equilibrium phosphate concentration,EPCo)非常接近(细粉砂、中粉砂、粗粉砂和砂分别为55.0、54.9、51.7和49.0μgL-1)。沉积物对磷酸盐的吸附容量、吸附速率和本底吸附值(native adsorbed phosphorus, NAP)很大程度上受粒径的控制,粒径32μm沉积物的总吸附容量值是粒径32μm的沉积物的6倍。由于细粒径沉积物对磷酸盐具有较高的吸附容量,东海内陆架的泥质区对上覆水及间隙水中的磷酸盐浓度起着重要的调控作用,同时对长江输入的磷酸盐是一个有效的捕集器,可降低东海外陆架遭受富营养化的风险。3.通过对长江口及邻近的东海内陆架表层沉积物中的磷形态和沉积物基本特征进行分析,研究了磷的分布、生物可利用性和保存。结果表明,表层沉积物中总磷(Total phosphorus, TP)的变化范围为15.0-21.4 μmolg-1,最高值出现在口门附近。De-P、Re-P、Or-P、Au-P、Ex-P和Fe-P对TP的贡献分别为55.6%、17.8%、16.1%、5.5%、2.5%和2.5%。De-P含量最高的区域出现在长江口口门和河口外陆架区域。Or-P在长江口和浙闽沿岸泥质区含量较高,并与粉砂、SSA和TOC有相似的分布特点。Re-P主要分布在近河口和浙闽沿岸区域。De-P/SSA和TOC/SSA的比值随SSA的增大而逐渐减小,而Or-P/SSA的比值随SSA的增大基本不发生改变,表明Or-P在矿物表面已经达到吸附-解吸平衡。TOC与总有机磷(Total organic-P, TOP;为Re-P与Or-P之和)的比值(平均～84)低于Redfield比值,表明长江口及邻近的东海内陆架移动泥区的有机物已经进行了充分的再矿化。而TOC/Or-P的比值(72～422,平均值为188)则相对较高,表明在有机物再矿化的过程中Or-P优先于TOC发生分解。4.测定了采集于该研究海域泥质区和非泥质区的三根柱状沉积物样品中的磷的形态,并结合粒度组成、21oPb活度、TOC及其稳定同位素(813C)、间隙水中的Fe2+和Mn2+以及间隙水和上覆水中的PO43-和NH4+等参数,探讨了不同沉积环境下磷的迁移转化、成岩过程和保存特点。研究表明,受长江陆源输入的影响,处于长江口及东海内陆架泥质区的12和31号柱沉积物中的TP以及一些陆源磷形态尤其是De-P的含量远高于处于非泥质区的33号站位。由于移动泥层的混匀作用,31号柱沉积物中的210Pbexcess、中值粒径(Median grain size, MGS)以及多种磷形态(Ex-P、Or-P、Au-P、Re-P和De-P)的含量在沉积柱上层一定深度范围内几乎保持不变,而且与下层分布表现出明显的不同；而12号柱沉积物中210Pbcxcess及非活性磷形态(如De-P、Au-P和Re-P)的含量在整个深度范围内均保持不变。该区域柱状沉积物中的Or-P和Fe-P发生了向Au-P的转化。研究还发现,处于泥质区的31号柱的沉积物是间隙水中磷酸盐的源,而处于非泥质区的33号柱的沉积物充当了间隙水中磷酸盐的汇。5.通过对采集于东海内陆架柱状沉积物中的沉积物粒径、SSA、TOC、C/N比值、碳稳定同位素以及颗粒磷形态进行分析,探讨了用碎屑磷作为长江流域洪水历史重建指标的可行性。研究发现,De-P峰值出现在1850s、1860s、1900s、 1920s、1950s、1980s和2000s,与长江流域200年来发生的大洪水记录吻合。研究还发现,De-P与长江口1981年和1998年发生的两次由长江大洪水引发的极端缺氧事件有较好的对应关系,而这两次极端缺氧事件也已被Mo/Al所证实。进一步分析表明,De-P与长江流域1950s、1980s和2000s年发生的极端洪水事件以及与洪水相关的气候事件,如加强的厄尔尼诺-南方涛动(ENSO, El Nino-Southern Oscillation)、偏弱的东亚夏季风(EASM, East Asian summer Monsoon)以及太平洋十年际振荡(PDO, Pacific Decadal Oscillation)的暖位相均有较好的对应关系,表明De-P也可能成为指示与极端洪水事件相关的气候事件的替代指标。6.沿长江口盐度梯度共采集了7个站位的表层水样品(2013年7月),通过磷酸盐的氧同位素分析示踪长江口磷酸盐的循环状况。结果表明,长江口水团可以用长江淡水和东海海水两个端元的混合模型进行较好地描述。在此基础上,本研究建立了磷酸盐的818Op两端元混合线和混合平衡线,并对磷酸盐的循环情况进行研究,发现在长江淡水端,磷酸盐并未经历强烈的生物循环过程,主要受物理混合作用的影响；最大浑浊带磷酸盐的生物循环过程也较弱,较深水层其它来源的磷酸盐改变了该区域δ18Op原本的特征值；而在羽状前锋,δ18Op的测定值几乎等于其平衡值,表明磷酸盐已经进行了充分的生物循环过程。
[Abstract]:The biogeochemical process of the River Estuary and river under the influence of marginal sea phosphorus is an important component of the marine phosphorus cycle. This paper takes the Yangtze Estuary and inner shelf of the East China Sea as the main study area, using field investigation and laboratory simulation combined with particulate fractions, the means of combining particle size composition the specific surface area (Specific, surface, area, SSA), mineral composition, particulate organic carbon and its stable isotopes and phosphate oxygen isotopes in various parameters of water, sediment and interstitial water, distribution of phosphorus, the mixing behavior of migration and transformation rules are studied systematically, in order to deepen biogeochemistry the process of Changjiang estuary and inner shelf of the East China Sea of phosphorus rich understanding of biogeochemical cycling of biogenic elements on high turbidity estuary. The main results are as follows: 1. along the Yangtze River Estuary salt Gradient of collected surface water and suspended particulate matter samples (June 2011), the distribution of dissolved phosphorus and particulate phosphorus, mixing behavior and migration were studied. Water elutriation particles are divided into 5 grade, with improved SEDEX (sequential extraction method) analysis method was used to determine the different particulate phosphorus form, was found between different forms of phosphorus, especially dissolved phosphorus and phosphorus can be activated particles of exchangeable phosphorus (Exchangeable-P, Ex-P), organic phosphorus (Organic-P, Or-P) and iron bound phosphorus (Fe-bound, P, Fe-P) has strong mutual transformation between detrital phosphorus. (Detrital-P, De-P) and Or-P is the most two kinds of phosphorus forms in suspended particulate matter, the content of total particulate phosphorus accounted for 43.9% and 26.1%.De-P increases with the diameter of the particle, and the content of Or-P and other forms of phosphorus with the increasing of the size of particles .8 decreased M component is considered to be the "real particle suspension", this study shows that "carry real floating" particles of bioavailable phosphorus (Bioavailable-P, BAP; Ex-P, Or-P and Fe-P and the flux is 0.21 * 104tPyr-1), the total biomass flux can be accounted for P/SSA the use of 29%. fine particles of phosphorus in value is very low, indicating that these particles of phosphorus in the preservation of low efficiency. The surface sediments of Yangtze Estuary grading of suspended particulate matter in the De-P/SSA and Fe-P/SSA and the mouth of the Yangtze River basic, Au-P (authigenic apatite, Authigenic-P / SSA (Re-P) and refractory organic phosphorus, Refractory-P /SSA) from suspended particulate matter to the sediments decreased slightly, while Ex-P/SSA and Or-P/SSA in surface sediments was significantly lower than that of suspended particles, further show that the particles of different forms of phosphorus with suspended particles in estuarine sedimentation in the process is different .2. determination of particle behavior of phosphorus form in the sediment samples and sediment samples grading grading of adsorption kinetics and isothermal adsorption experiments, experimental adsorption characteristics affected by salinity. The results showed that the content of De-P in sediments is the most abundant content, followed by biological Or-P. fine particle size in the sediment phosphorus availability is much higher than that of Sandy that fine sediment, particles of phosphorus from the sediment to the overlying water or surrounding interstitial water release plays a leading role. The analysis found from adsorption isotherms from the same sampling stations of the graded sediments obtained, zero equilibrium phosphate concentration in different particle size of sediment corresponds to the value of (zero equilibrium phosphate concentration, EPCo) is close (fine sand, silt and coarse silt and sand were 55.0,54.9,51.7 and 49 gL-1). The adsorption capacity of sediments to phosphate, adsorption rate The adsorption rate and the value (native adsorbed phosphorus, NAP) are largely controlled by the particle size, the adsorption capacity of the total size of 32 mu m sediment value is 6 times the sediment grain size of 32 m. The adsorption capacity of fine-grained sediments with high phosphate, Inner Shelf mud areas of the East China Sea plays an important role in the regulation of phosphate concentration in the overlying water and interstitial water of the Yangtze River at the same time, the input of phosphate is an effective collector, can reduce the East China Sea continental shelf suffered eutrophication risk.3. through the analysis of precipitation of phosphorus and sediment characteristics of sediments in the Changjiang Estuary and its adjacent the inner shelf of the East China Sea surface, the distribution of phosphorus, bioavailability and preservation. The results showed that the total phosphorus in the surface sediments (Total, phosphorus, TP) in the range of 15.0-21.4 molg-1, the highest value appeared in.De-P, near the entrance of Re-P, Or-P, Au- P, Ex-P and Fe-P's contribution to TP were 55.6%, 17.8%, 16.1%, 5.5%, appeared in the Yangtze River Estuary and Yangtze Estuary shelf region.Or-P in the Yangtze River Estuary and Zhejiang Fujian coastal mud area with high content of area 2.5% and the highest content of 2.5%.De-P, and SSA and TOC silt, similar ratio increases. The distribution characteristics of.Re-P are mainly distributed in the near estuary and Zhejiang Fujian coastal areas.De-P/SSA and TOC/SSA with SSA decreases, and the ratio of Or-P/SSA was increased with the SSA basic does not change, show that Or-P has reached the adsorption desorption equilibrium of.TOC and total organic phosphorus on the mineral surface (Total organic-P, Re-P and TOP; Or-P) and the ratio (average ~ 84) lower than the ratio of Redfield, showed that the organic matter in the Changjiang Estuary and adjacent to the inner shelf of the East China Sea mobile mud area has been fully remineralization. And the ratio of TOC/Or-P (72~422, average value is 188) is relatively high, that in organic The process of remineralization of Or-P prior to the TOC sample three column sediments collected from the study area determination of mud area and non mud area decomposition.4. in the form of phosphorus, and combined with the grain size composition, activity of 21oPb, TOC and stable isotope (813C), Fe2+ and Mn2+, and interstitial water the overlying water in the PO43- and NH4+ parameters such as pore water, discusses the migration under different sedimentary environment of phosphorus transformation, diagenetic processes and preservation characteristics. The results show that the Yangtze River affected by terrestrial input, in the Yangtze River Estuary and East China Sea Mud Area on the inner shelf of the 12 and 31 columns in TP and terrigenous sediments phosphorus forms especially the content of De-P is much higher than in the non Mud Area No. 33 stations. Because the mixing effect of the mobile mud layer, column 31, 210Pbexcess in the sediment, the median diameter (Median grain, size, MGS) and various forms of phosphorus (Ex-P, Or-P, Au-P, Re-P and De-P) The content remained almost unchanged in the upper sediment column within a certain depth range, and lower distribution are obviously different; and 210Pbcxcess 12 column sediments and non active phosphorus forms (such as De-P, Au-P and Re-P) were kept constant throughout the depth range. The domain sediments in this area Or-P Fe-P and the transformation to Au-P. The study also found that the sediment in the mud area No. 31 cylinder is the gap of phosphate in water source, while in the non Mud Area No. 33 column sediments act as pore water phosphate sink.5. of the collected in the East China Sea shelf sediments sediments the particle size, SSA, TOC, C/N ratio, carbon isotope and particulate phosphorus analysis, discusses the feasibility of detrital phosphorus as Yangtze River flood historical reconstruction index. The study found that the peak value of De-P appeared in 1850s, 1860s, 1900s, 1920s, 1 950s, 1980s and 2000s, consistent with the flood recorded in Yangtze River Basin in 200 years. The study also found that there is a good corresponding relationship between the De-P and the mouth of the Yangtze River in 1981 and 1998 occurred in two caused by large floods of the Yangtze River and the two extreme anoxic events, extreme anoxic events also has been confirmed by Mo/Al further. The analysis shows that the 1950s De-P and the Yangtze River Basin, the extreme flood events occurred in 2000s and 1980s and flood related climatic events, such as the strengthening of the El Nino Southern Oscillation (ENSO El, Nino-Southern Oscillation), the weakness of the East Asian summer monsoon (EASM, East Asian summer Monsoon) and Pacific interannual oscillation (PDO, Pacific ten Decadal Oscillation) the warm phase has a better correlation, indicating that De-P might become an alternative index.6. indicator associated with extreme flood events and climate events along the long river estuary salinity gradient were collected The surface water samples at 7 stations (July 2013), the circulation status of oxygen isotope tracer analysis of phosphate phosphate in the Changjiang Estuary. The results show that the mouth of the Yangtze River water can be mixed with the model of two end of the Yangtze River water and the East China Sea were well described. On this basis, this study established phosphate across 818Op yuan mixed line and mixed equilibrium line, and circulation of phosphate was studied, found in the Yangtze River water end, phosphate cycling process has not experienced strong, mainly affected by physical mixing effect; biological cycle process with phosphate turbidity maximum is also weak, deep water from other sources of phosphate changed the region originally 18Op. The characteristic value; and in the feather striker, 5 18Op measured value is almost equal to its equilibrium value, has been showed that phosphate cycling process fully.

【学位授予单位】：中国海洋大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：P736.4

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