|关键词||胶州湾 沉积物-海水界面 营养盐 交换速率 影响因素|
胶州湾多数站位沉积物-海水界面无机氮主要以NO3-N和NH4-N的形式进行交换。在夏季，胶州湾多数站位沉积物表现为水体NO3-N的源，冬季则表现为汇，交换速率为-714~1 560 μmol /(m2·d)。NO2-N在胶州湾沉积物-海水界面的交换速率普遍较低，夏季沉积物多表现为水体NO2-N的源，冬季则表现为水体NO2-N汇，交换速率为-117~941 μmol /(m2·d)。夏季胶州湾沉积物表现为NH4-N的源，而在冬季多数站位沉积物表现为水体NH4-N的汇，交换速率在-1 334~26 064 μmol /(m2·d)范围内。夏季沉积物-海水界面PO4-P的迁移方向并不一致，而冬季沉积物则表现为水体PO4-P的汇，界面PO4-P的交换速率为-128~861 μmol /(m2·d)。夏、冬季胶州湾沉积物均表现为水体SiO3-Si的源，交换速率为43~4 889 μmol/(m2·d)。
夏季胶州湾沉积物海水界面间NO3-N、NO2-N和NH4-N的交换通量分别为2.35×108、6.35×107、1.34×109 mmol·d-1，能提供维持初级生产力所需N的39.3%，PO4-P的交换通量为3.69×107 mmol·d-1，能提供维持初级生产力所需P的14.1%。而冬季沉积物则表现为水体NO3-N、NO2-N、NH4-N和PO4-P的汇，其交换通量分别为-6.39×107、-1.49×107、-1.33×108、和-2.20×107mmol·d-1。夏、冬季胶州湾SiO3-Si的交换通量分别为6.50×108和1.32×108 mmol·d-1，分别提供维持初级生产力所需Si的15.6%和25.8%。
夏季胶州湾沉积物-海水界面NO3-N的交换速率仅与表层沉积物的含水率、底层NO3-N浓度和间隙水中NO3-N浓度相关，而NO2-N和NH4-N的交换速率与底质参数、底层水体和间隙水体中对应营养盐的浓度均无显著相关，由主成分回归分析可知，影响夏季NO3-N、NO2-N和NH4-N交换的主要环境因子是表层沉积物的Chl a、TOC、TN、含水率和底层无机氮浓度。由主要影响因子与营养盐交换速率的关系可推知沉积物中有机质的矿化作用和扩散可能是调控NO3-N交换的主要过程。沉积物中有机质的矿化、底栖藻类的同化作用、沉积物的吸附-解吸和扩散可能是调控夏季胶州湾沉积物-海水界面NH4-N交换的主要过程。NO2-N交换与界面NH4-N交换对环境因子变化的响应较为一致，因此NO2-N的交换可能主要受硝化作用调控。PO4-P的交换速率仅与表层沉积物的TOC和C/N相关，而影响其交换的主要环境因子是表层沉积物的Chl a、TOC和TP，有机质的矿化作用可能是影响夏季胶州湾沉积物-海水界面PO4-P交换的主要过程。夏季胶州湾沉积物-海水界面SiO3-Si的交换速率与间隙水中SiO3-Si浓度、底层SiO3-Si浓度差、表层沉积物的TOC、Chl a、BSi和含水率相关，表层沉积物的Chl a、TOC、BSi、含水率和间隙水中SiO3-Si浓度是主要影响因子，溶解和扩散过程可能是调控夏季SiO3-Si交换的主要过程，而有机质的矿化能通过改变沉积物性质促进夏季底层SiO3-Si的交换。
冬季沉积物-海水界面NO3-N的交换与底质参数、底层水体和间隙水体中NO3-N浓度均无显著相关，主要影响因子是表层沉积物中的Chl a含量和间隙水中DIN浓度，沉积物-海水界面NO3-N的交换受底栖藻类的同化作用和扩散共同调控。NO2-N和NH4-N的交换速率仅与表层沉积物中Chl a呈一定正相关，表层沉积物的Chl a、粘土含量和D50是影响NH4-N交换的主要环境因子，底层NH4-N的交换可能主要受海洋内源自生有机质的降解作用和吸附-解吸过程调控。与夏季一样，冬季胶州湾沉积物-海水界面NO2-N交换与界面NH4-N交换对环境因子变化的响应较为一致，因此NO2-N的交换可能受硝化作用调控。PO4-P的交换速率仅与表层TOC相关，主要影响因子有表层沉积物中的Chl a、TOC、含水率、底层PO4-P浓度和间隙水PO4-P浓度，有机质对PO4-P的吸附-解吸作用、底栖生物的同化作用和扩散可能是调控冬季底层PO4-P交换的主要过程。SiO3-Si的交换与间隙水中SiO3-Si浓度和表层沉积物中BSi含量相关，主要影响因子是表层沉积物中的Chl a含量和间隙水中SiO3-Si浓度，主要受底栖藻类的同化作用、溶解和扩散过程调控。
; Intatct sediment cores and the bottom seawater in the corresponding stations in Jiaozhou Bay was collected in July 2015 and Jaunary 2016, and the benthic exchange rates of NO3-N, NO2-N, NH4-N, PO4-P and SiO3-Si were measured by intact sediment cores incubation. Further, the benthic fluxes and its contributions to the primary productivity were estimated, and the impacts of relevant environmental factors on the benthic transport were discussed. The main results are as follows:
1、SiO3-Si was directed out of sediment to the overlying water in Jiaozhou Bay，while the exchange of NO3-N、NO2-N、NH4-N and PO4-P varied with season. Sediment was an important source of DIN and PO4-P in summer, DIN and PO4-P transferred from water column to sediment in winter. Based on the exchange rates and the proportion of different sediments, the exchange fluxes of dissolved nutrient were estimated. The result showed that sediment could provide 39.3% and 14.1% of N and P required by the primary productivity respectively. Sediment was always the source of SiO3-Si, providing 15.6% SiO3-Si required for primary productivity in summer, and 25.8% SiO3-Si in winter.
The exchange of dissolved inorganic nitrogen at sediment-water interface in Jiaozhou Bay was mainly in forms of NO3-N and NH4-N. The exchange of NO3-N and NH4-N was in direction from sediment to overlying water in summer, while it became uncertain in winter. The exchange rates ranged from -714 to 1 560 μmol /(m2·d) for NO3-N and from -1 334 to 26 064 μmol /(m2·d) for NH4-N. The exchange rates of NO2-N and PO4-P varies in summer and winter, ranging from -117 to 941 μmol /(m2·d) for NO2-N and from -128 to 861 μmol /(m2·d) for PO4-P. The exchange rates of SiO3-Si were in the direction from sediment to overlying water, ranging from 43 to 4 889 μmol/(m2·d).
In summer, sediment was an important source of NO3-N、NO2-N and NH4-N,the fluxes at the sediment-water interface were 2.35×108、6.35×107 and 1.34×109 mmol·d-1 respectively, providing 39.3% N required for primary productivity. In winter, however, NO3-N、NO2-N and NH4-N transferred from water to sediment, and fluxes were -6.39×107、-1.49×107 and -1.33×108 mmol·d-1，respectively. PO4-P transferred from water to sediment with fluxes of 3.69×107 mmol·d-1 in summer， providing 14.1% P required for primary productivity. In winter, the transferring direction was reversed, and the flux was -2.20×107mmol·d-1. Sediment was always the source of SiO3-Si, and its fluxes were 6.50×108 mmol·d-1 in summer and 1.32×108 mmol·d-1 in winter，providing 15.6% and 25.8% Si required for primary productivity respectively.
2、The most important environmental factors and processes controlling the nutrient exchange rates varied with season and the type of nutrients. In summer, mineralization was an controlling processes for all kinds of nutrients. The exchange of NH4-N in summer was also controlled by assimilation and adsorption-desorption, while the exchange of SiO3-Si was mainly controlled by dissolution and diffusion. In winter, mineralization became weak and the exchange of NO3-N, PO4-P and SiO3-Si were mainly influenced by assimilation and diffusion. The exchange of PO4-P in winter was also influenced by the process of adsorption-desorption caused by organic matter mattered, and the exchange of SiO3-Si in winter was also influenced by dissolution process. Same as summer, the exchange of NH4-N in winter was probably significantly influenced by mineralization and adsorption-desorption at sediment-water interface.
The exchange rates of NO3-N were correlated to water ratio of surface sediment and bottom-water NO3-N concentration and pore-water NO3-N concentration, while the exchange rates of NO2-N and NH4-N were not correlated to any factor of surface sediment or the concentration of corresponding nutrient. Based on principal component regression analysis, the result revealed that total organic carbon (TOC), chlorophyll a (Chl a), total nitrogen (TN), water ratio and concentration of dissolved nitrogen (DIN) were the the most important factors influencing the exchange of NO3-N、NO2-N and NH4-N. As a result, mineralization and diffusion might be the controlling processes for the exchange of NO3-N. Mineralization, assimilation, adsorption-desorption and diffusion, however, might be the most controlling processes for the exchange of NH4-N in summer. Exchange of NO2-N varied in the same pattern with NH4-N in summer, so that nitrification may be the key process controlling the exchange of NO2-N.
The exchange rates of PO4-P in summer were positively related to TOC and negatively correlated to C/N in surface sediment, and the major factors influcing the exchange of PO4-P were Chl a、TOC and TP. As a result, mineralization might be the most controlling processes for the exchange of PO4-P in summer.
The exchange rates of SiO3-Si in summer were significantly related to TOC and Chl a in surface sediment, and also positively related to biogenic silicate (BSi), content of clay, water ratio, SiO3-Si concentration in pore water and the concentration difference of SiO3-Si at the interface, and TOC, Chl a, biogenic silicate (BSi), content of clay, water ratio of surface sediment and SiO3-Si concentration in pore water were the most important relevant factors. As a result, the exchange of SiO3-Si at sediment-water interface in summer was a consequence of dissolution-diffusion process which was dominantly controlled by biological activity.
The exchange rates of NO3-N in winter were not correlated to any factor of surface sediment or the concentration of corresponding nutrient. Considering that Chl- a in the surface sediment and the DIN concentration in pore water were the most important factors, assimilation and diffusion might be the controlling processes for the exchange of NO3-N. The exchange rates of NO2-N in winter were only related to Chl- a in the surface sediment and the mechanism was not clear yet. The exchange rates of NH4-N in winter were positively related to Chl a, and Chl a in surface sediment, content of clay and medium diameter (D50) had significant effects on the exchange of NH4-N , so the degradation of marine endogenous organic matter and adsorption- desorption at sediment-water interface might be the controlling processes for the exchange of NH4-N in winter.
The exchange rates of PO4-P in winter were only related to TOC in surface sediment, and Chl a, TOC, water ratio and PO4-P concentration in bottom water and pore water were the major relevant factors influencing the exchange of PO4-P, so assimilation, dilution and adsorption-desorption caused by the organic matter might be the controlling processes for the exchange of PO4-P in winter.
The exchange rates of SiO3-Si in winter were significantly positively related to BSi in surface sediment and SiO3-Si concentration in pore water, and the Chl a in surface sediment and pore-water SiO3-Si concentration had major effects on the exchange of SiO3-Si at sediment-water interface, so the exchange of SiO3-Si in winter was controlled by assimilation, diffusion and dissolution.
|学科领域||地球化学 ; 海洋科学|
|汪雅露. 胶州湾沉积物-海水界面营养盐的迁移特征及其影响因素解析[D]. 北京. 中国科学院大学,2016.|