Three comprehensive surveys were performed in the Changjiang（Yangtze River） Estuary（CJE） to understand the biogenic silica（BSi） composition, behavior and budget. It is indicated that the BSi is composed of phyto...Three comprehensive surveys were performed in the Changjiang（Yangtze River） Estuary（CJE） to understand the biogenic silica（BSi） composition, behavior and budget. It is indicated that the BSi is composed of phytoliths,phytoplankton and sponges; phytolith BSi has 16 forms and account for 23% to 83% of the bulk BSi in the maximum turbidity zone. The budget shows that the major exogenous BSi source in the water column of the CJE is the riverine input, accounting for 95% of the total BSi input. Dominant processes that maintain BSi levels in the water column are the primary production（55 Gmol/a） and the subsequent BSi sedimentation（46 Gmol/a）; and the BSi pool produced by the primary production represents two point three times the BSi loading of the Changjiang River and 63% of the BSi output, respectively. The net export（26 Gmol/a） of BSi from the CJE to the East China Sea and Yellow Sea roughly equals the riverine BSi loading. The observed total accumulation of BSi is one point seven times larger than the loading of total BSi output, with 53% to 88% of phytolith BSi and their assemblage, indicating that there has already been a ＂filter＂ of terrestrial BSi. The reverse weathering in sediments is an important process for the reactive silica removal in the CJE due to authigenic alterations. It is indicated that the phytolith fluxes in the suspended load represent a significant BSi source in the estuary, and the CJE would act as a net BSi sink.展开更多
Eleven stations were occupied in the Tokyo-wan during a study on the distribution of methane in this eu trophic coastal environment in August of 1993. The principal features of the Observed methane included the follow...Eleven stations were occupied in the Tokyo-wan during a study on the distribution of methane in this eu trophic coastal environment in August of 1993. The principal features of the Observed methane included the following 6points: (1)Excess methane in the surface layer from 1. 5 times to greater than 25 times solubility equilibrium with the at mosphere. (2)The methane concentration in the upper ￣er displayed a maximum zone around Saution 5 and the secondhashest in bottom water at StationS 1 and 2, probably because there was the front resulting from the chemical processes.(3)Correlations between methane and other parameters exhibited correspondences and the methane distribution beingmainly controlled by physical processes. (4)In some stations, vertical profiles revealed associations between methane andChl a and the relationships between methane with Chl a or nitrite have shown good linear correlations. It is postulated thatsome methane is formed in situ (5)The calculated flux of methane across the air-sea interface was about 71 μmol/(m2· d). (6)Some methane might be produced along with the organic matter decomposition in bottom water. Others mightbe due to the methane fluxes into the bottom water from the anoxic sediment inside the bay, which are believed to be themain methane source.展开更多
Concentrations of suspended particle material(SPM), dissolved silicate(DSi), biogenic silica(BSi), phytoliths(plant produced siliceous microscopic structures), and other parameters were analyzed to examine the influen...Concentrations of suspended particle material(SPM), dissolved silicate(DSi), biogenic silica(BSi), phytoliths(plant produced siliceous microscopic structures), and other parameters were analyzed to examine the influence of both natural processes and human activities on silica delivery to the estuary of the Huanghe River(Yellow River). Our results indicate that the concentrations of DSi in the river decreased significantly since 1986. Approximately 34% of dissolved silica was trapped in the basin between 1986 and 2010 due to a reduction of soil erosion. Phytoliths comprised 67.2%–96.3% of BSi, with the smoothing bar type being the dominant form. Concentrations of BSi are significantly higher in the Huanghe River compared to other major rivers throughout the world due to its high sediment yield. We also found that the ratios of BSi/(BSi+DSi) and BSi/SPM were approximately 0.5 and 0.003 at Lijin near the river mouth, indicating that BSi carried in suspension by the Huanghe River was an important component of the rivers silica load. Significant amounts of BSi were also composed of phytoliths in Bohai Sea sediments near the Huanghe River estuary with the smoothing bar form again being the most abundant. The relatively high specific fluxes of BSi in the Huanghe River reflect its high turbidity and high erosion rates in the basin. The high sediment load originating on the Loess Plateau is likely responsible for the higher BSi flux, in agreement with a general trend of increasing BSi flux with increasing sediment flux in global river systems. This study demonstrates that BSi transported by rivers can be composed largely of phytoliths originating from the erosion of topsoils. The flux of phytoliths in river's suspended sediment load may therefore represent a significant contribution to the biogeochemical cycle of silica in coastal waters.展开更多
基金The Basic Scientific Fund for National Public Research Institutes of China under contract No.GY0216Q03the National Science Foundation of China under contract Nos 41776089 and 41576084
文摘Three comprehensive surveys were performed in the Changjiang（Yangtze River） Estuary（CJE） to understand the biogenic silica（BSi） composition, behavior and budget. It is indicated that the BSi is composed of phytoliths,phytoplankton and sponges; phytolith BSi has 16 forms and account for 23% to 83% of the bulk BSi in the maximum turbidity zone. The budget shows that the major exogenous BSi source in the water column of the CJE is the riverine input, accounting for 95% of the total BSi input. Dominant processes that maintain BSi levels in the water column are the primary production（55 Gmol/a） and the subsequent BSi sedimentation（46 Gmol/a）; and the BSi pool produced by the primary production represents two point three times the BSi loading of the Changjiang River and 63% of the BSi output, respectively. The net export（26 Gmol/a） of BSi from the CJE to the East China Sea and Yellow Sea roughly equals the riverine BSi loading. The observed total accumulation of BSi is one point seven times larger than the loading of total BSi output, with 53% to 88% of phytolith BSi and their assemblage, indicating that there has already been a ＂filter＂ of terrestrial BSi. The reverse weathering in sediments is an important process for the reactive silica removal in the CJE due to authigenic alterations. It is indicated that the phytolith fluxes in the suspended load represent a significant BSi source in the estuary, and the CJE would act as a net BSi sink.
文摘Eleven stations were occupied in the Tokyo-wan during a study on the distribution of methane in this eu trophic coastal environment in August of 1993. The principal features of the Observed methane included the following 6points: (1)Excess methane in the surface layer from 1. 5 times to greater than 25 times solubility equilibrium with the at mosphere. (2)The methane concentration in the upper ￣er displayed a maximum zone around Saution 5 and the secondhashest in bottom water at StationS 1 and 2, probably because there was the front resulting from the chemical processes.(3)Correlations between methane and other parameters exhibited correspondences and the methane distribution beingmainly controlled by physical processes. (4)In some stations, vertical profiles revealed associations between methane andChl a and the relationships between methane with Chl a or nitrite have shown good linear correlations. It is postulated thatsome methane is formed in situ (5)The calculated flux of methane across the air-sea interface was about 71 μmol/(m2· d). (6)Some methane might be produced along with the organic matter decomposition in bottom water. Others mightbe due to the methane fluxes into the bottom water from the anoxic sediment inside the bay, which are believed to be themain methane source.
基金financially supported by the National Natural Science Foundation of China(Grant Nos.41106072,41376093,41206064)Natural Science Foundation of Shandong(Grant No.ZR2010DM006)
文摘Concentrations of suspended particle material(SPM), dissolved silicate(DSi), biogenic silica(BSi), phytoliths(plant produced siliceous microscopic structures), and other parameters were analyzed to examine the influence of both natural processes and human activities on silica delivery to the estuary of the Huanghe River(Yellow River). Our results indicate that the concentrations of DSi in the river decreased significantly since 1986. Approximately 34% of dissolved silica was trapped in the basin between 1986 and 2010 due to a reduction of soil erosion. Phytoliths comprised 67.2%–96.3% of BSi, with the smoothing bar type being the dominant form. Concentrations of BSi are significantly higher in the Huanghe River compared to other major rivers throughout the world due to its high sediment yield. We also found that the ratios of BSi/(BSi+DSi) and BSi/SPM were approximately 0.5 and 0.003 at Lijin near the river mouth, indicating that BSi carried in suspension by the Huanghe River was an important component of the rivers silica load. Significant amounts of BSi were also composed of phytoliths in Bohai Sea sediments near the Huanghe River estuary with the smoothing bar form again being the most abundant. The relatively high specific fluxes of BSi in the Huanghe River reflect its high turbidity and high erosion rates in the basin. The high sediment load originating on the Loess Plateau is likely responsible for the higher BSi flux, in agreement with a general trend of increasing BSi flux with increasing sediment flux in global river systems. This study demonstrates that BSi transported by rivers can be composed largely of phytoliths originating from the erosion of topsoils. The flux of phytoliths in river's suspended sediment load may therefore represent a significant contribution to the biogeochemical cycle of silica in coastal waters.
