^(234)Th-^(238)U disequilibria were applied to examine the particle dynamics in the euphotic zone of the central South China Sea during the spring 2002 cruise.The particulate organic carbon (POC),^(234)Th (including b...^(234)Th-^(238)U disequilibria were applied to examine the particle dynamics in the euphotic zone of the central South China Sea during the spring 2002 cruise.The particulate organic carbon (POC),^(234)Th (including both dissolved and particulate) and ^(238)U in the water column at three stations were determined. The profiles of ^(234)Th/^(238)U activity ratio at the three stations all showed consistent ^(234)Th deficit as compared to ^(238)U in the upper 100 m water column.Based on the profiles of the dissolved and particulate ^(234)Th and a steady state box model,the dissolved ^(234)Th scavenging rates,the particulate ^(234)Th removal rates and their resident times were quantified.It was found that the POC downward export fluxes out of the upper 100 m euphotic zone ranged from 9.40 to 14.78 mmol·m^(-2)·d^(-1).The results from this study provide new information for our understanding of carbon biogeochemical cycle in the South China Sea.展开更多
通过对我国西南地区3个洞穴9根大型石笋272个初始234U/238U数据的分析研究,发现石笋初始234U/238U值长尺度变化与海洋沉积SPECMAP曲线δ18O记录有一定的正相关关系,与北纬25°夏季太阳辐射能量变化曲线呈一定的负相关关系,石笋初始2...通过对我国西南地区3个洞穴9根大型石笋272个初始234U/238U数据的分析研究,发现石笋初始234U/238U值长尺度变化与海洋沉积SPECMAP曲线δ18O记录有一定的正相关关系,与北纬25°夏季太阳辐射能量变化曲线呈一定的负相关关系,石笋初始234U/238U值的变化在冰期时波动强烈,而在间冰期波动相对平缓,在间冰期和冰期(间冰阶和冰阶)转化阶段该值呈跳跃状态变化。末次冰期及全新世阶段石笋初始234U/238U变化记录了该时段内的BA暖期和YD突变冷事件;全新世8200 a BP、7200 a BP、5200 a BP、4200 a BP、2800 a BP、1400 a BP发生的几次较强冷事件在石笋初始234U/238U值都有相应记录,并且和长尺度的变化规律一致,冷事件发生时石笋初始234U/238U值偏重,暖期偏轻。封闭系统形成的洞穴石笋初始234U/238U变化类似于同地区洞穴石笋的δ18O对气候变化的记录特征,在我国西南地区两者与夏季风变化的强弱呈现一种负相关的关系,洞穴石笋初始234U/238U值可以作为一个有用的古气候替代指标来研究古降水的变化。展开更多
234Th is widely used to quantify the magnitude of upper ocean particulate organic carbon （POC） export in oceans. In the present work, the rates of particulate organic carbon export were measured based on the distrib...234Th is widely used to quantify the magnitude of upper ocean particulate organic carbon （POC） export in oceans. In the present work, the rates of particulate organic carbon export were measured based on the distribution patterns of 234Th/238U disequilibrium in the water column within the continental slope of the East China Sea （ECS） during May 2011. The profiles of particulate and dissolved 234Th activities at all three stations showed a relative deficit with respect to 238U in the upper 100 m of the water column. The dissolved 234Th scavenging rates and the particulate 234Th removal rates and their residence times were calculated by a one-dimensional steady state model. The results showed that the dissolved a34Th scavenging rates and the particulate 234Th removal rates ranged from 12.4-61.4 dpm/（m3.d） and from 3.8-21.8 dpm/（m3.d）, respectively. The residence times of dissolved and particulate 234Th were in the range of 3.4-158 d and 63.7- 96.5 d, respectively. Combined with the measurement of POC/Z34Th ratios of suspended particles, POC export flux （calculated by carbon） from the euphotic zone was estimated in the study region, which ranged from 4.14-14.7 mmol/（m2 .d）, with an average of 8.21 mmol/（m3.d）, occupying 35% of the prime productivity in the study area. The results of this study can provide new information for better understanding the carbon biogeochemical cycle within the continental slope of the ECS.展开更多
The optimum multiparameter(OMP) method was often used to determine the percentages of water masses based on temperature, salinity and other parameters, like nutrient or dissolved oxygen(DO). There are a number of wate...The optimum multiparameter(OMP) method was often used to determine the percentages of water masses based on temperature, salinity and other parameters, like nutrient or dissolved oxygen(DO). There are a number of water masses in the East China Sea(ECS), a marginal sea of the western Pacific Ocean. However, it is difficult to clarify the proportion of water masses using traditional parameters, such as temperature, salinity, nutrient or DO because of the occurring of intensive biogeochemical processes in the near shore and shelf areas. Here, we reported the use of ^(234)U/^(238)Uactivity ratio embedded in the OMP method. The results indicate that seawater in the northern ECS mainly consisted of the estuarine water of Changjiang River(CEW), Kuroshio water(KW), and Yellow Sea Coastal Current(YSCC). In March 2017, the CEW only influenced the offshore waters shallower than30 m;the KW affected the east edge and the YSCC contributed more than 75% in the northern ECS.展开更多
The spatial and temporal distributions of new production vary largely in different sea areas. To understand the level of new production in the sea area studied better, an estimate of new production must be obtained in...The spatial and temporal distributions of new production vary largely in different sea areas. To understand the level of new production in the sea area studied better, an estimate of new production must be obtained in large spatial and temporal scales. The ~234Th/ ~238U disequilibrium is an effective method for the study of new production. Two sampling strategies, vertically integrated sampling ap proach based on trapezoidal integration principle and discrete layer sampling approach, were compared in the studies of the xiamen Bay and the northern South China Sea. The scavenging fluxes and removal fluxes of ~234Th and the residence times for dissolved and particulate ~234Th were calculated. The coinci dent results from two Sampling approach suggest that vertically integrated sampling approach is not only effective and reliable, but also significantly reduces the number and volume of samples. It allows us to study new production by ba ^(234)Th - ^(238)U disequilibria in large spatial scale.展开更多
Activities of 234Th and nutrient concentrations in the upper 500 m water column were measured at a time-series station in the South China Sea over a time span of 12.3 d. Results showed a reduction of dissolved 234Th a...Activities of 234Th and nutrient concentrations in the upper 500 m water column were measured at a time-series station in the South China Sea over a time span of 12.3 d. Results showed a reduction of dissolved 234Th and an overall increase of particulate 234Th during the period. Meanwhile, activities of total 234Th kept fairly constant, implying rapid transformation of 234Th between the dissolved and particulate forms. Vertical profiles of total 234Th showed evident deficit of 234Th relative to 238U in the upper 500 m water column. Using an irreversible steady-state model of thorium scavenging, export fluxes of particulateorganic carbon (POC) corresponding to time points T1 and T2 were estimated to be 46.5 and 13.1 mmolC .m-2. d-1. It was demonstrated that the estimation of POC export was greatly dependent on the POC/234Thp ratios and the bias caused by the different models of 234Th scavenging, however, was considered to be of minor importance.展开更多
A simple model is established to describe the fate of particle-reactive pollutants in the Xiamen Bay. Based on the conditional distribution coefficients (Kd ) of chemicals and residence times of particle and waters, t...A simple model is established to describe the fate of particle-reactive pollutants in the Xiamen Bay. Based on the conditional distribution coefficients (Kd ) of chemicals and residence times of particle and waters, the model can be used to predict the fractions of pollutants which would be scavenged to sediments and would escape from the system. The model is calibrated using scavenging data derived from 234 Th - 238U disequilibrium. The fate of a potential pollutant which will be scavenged is a function of the properties of the chemical, of the particle dynamics, and of the waters dynamics in the environment. It is inappropriate to overlook any factor.展开更多
In the western part of the South Baikal Basin,spatial-temporal distribution of earthquake epicenters shows quasi-periodic seismic reactivation.The largest earthquakes that occurred in 1999(M_(W)=6.0)and 2008(M_(W)=6.3...In the western part of the South Baikal Basin,spatial-temporal distribution of earthquake epicenters shows quasi-periodic seismic reactivation.The largest earthquakes that occurred in 1999(M_(W)=6.0)and 2008(M_(W)=6.3)fall within seismic intervals of 1994-2003 and 2003-2012,respectively.In the seismic interval that began in 2013,the ^(234)U/^(238)U activity ratio(AR)in groundwater was monitored assuming its dependence on crack opening/closing that facilitated/prevented water circulation in an active boundary fault of the basin.Transitions from disordered,high-amplitude fluctuations of AR values to consistent,low-amplitude fluctuations in different monitoring sites were found to be sensitive indicators of both small seismic events occurring directly on the observation area,and of a large remote earthquake.The hydroisotopic responses to seismic events were consistent with monitoring data on deformation and temperature variations of rocks.The hydroisotopic effects can be applied for detecting a seismically dangerous state of an active fault and prediction of a large future earthquake.展开更多
During the Second Chinese National Arctic Expedition （CHINARE） from July to September 2003, depth profiles of dissolved and particulate 234Th in upper water columns were collected at two stations of BR03 and BR24 in...During the Second Chinese National Arctic Expedition （CHINARE） from July to September 2003, depth profiles of dissolved and particulate 234Th in upper water columns were collected at two stations of BR03 and BR24 in the Bering Sea. 234Th was sampled by using a traditional Fe （OH） 3 co-precipitation technique, which is a reliable approach to 234Th measurement. We observed 234 Wh excess at station BR03 below the euphotic zone, which was possibly due to the intensive remineralization of particulate matter. Particulate organic carbon （POC） export fluxes were estimated from a one-dimensional irreversible steady state model of ^234Th fluxes together with measurements of the POC/^234 Th ratio on the suspended particles. The POC export fluxes from the euphotic zone were II. 66 and I1.69 mmol C m^-2 d^- 1 at BR03 and BR24 stations, respectively. The ratios of POC fluxes to primary production at the two stations were about 0.5 and 0.59, respectively, probably due to the presence of large phytoplankton （in particular diatoms）.展开更多
基金Supported by the NSFC (key program No.40531007) and general Programs (No.40406014,40276001 and 10705019)the State Social Commonweal Grant (No.2004DIB5178)+1 种基金and the commonweal project sponsored by the Scientific Research Foundation of the Ministry of Science and Technology of China (No.2007050228)Chinese IPY Campaign found by MOF
文摘^(234)Th-^(238)U disequilibria were applied to examine the particle dynamics in the euphotic zone of the central South China Sea during the spring 2002 cruise.The particulate organic carbon (POC),^(234)Th (including both dissolved and particulate) and ^(238)U in the water column at three stations were determined. The profiles of ^(234)Th/^(238)U activity ratio at the three stations all showed consistent ^(234)Th deficit as compared to ^(238)U in the upper 100 m water column.Based on the profiles of the dissolved and particulate ^(234)Th and a steady state box model,the dissolved ^(234)Th scavenging rates,the particulate ^(234)Th removal rates and their resident times were quantified.It was found that the POC downward export fluxes out of the upper 100 m euphotic zone ranged from 9.40 to 14.78 mmol·m^(-2)·d^(-1).The results from this study provide new information for our understanding of carbon biogeochemical cycle in the South China Sea.
文摘通过对我国西南地区3个洞穴9根大型石笋272个初始234U/238U数据的分析研究,发现石笋初始234U/238U值长尺度变化与海洋沉积SPECMAP曲线δ18O记录有一定的正相关关系,与北纬25°夏季太阳辐射能量变化曲线呈一定的负相关关系,石笋初始234U/238U值的变化在冰期时波动强烈,而在间冰期波动相对平缓,在间冰期和冰期(间冰阶和冰阶)转化阶段该值呈跳跃状态变化。末次冰期及全新世阶段石笋初始234U/238U变化记录了该时段内的BA暖期和YD突变冷事件;全新世8200 a BP、7200 a BP、5200 a BP、4200 a BP、2800 a BP、1400 a BP发生的几次较强冷事件在石笋初始234U/238U值都有相应记录,并且和长尺度的变化规律一致,冷事件发生时石笋初始234U/238U值偏重,暖期偏轻。封闭系统形成的洞穴石笋初始234U/238U变化类似于同地区洞穴石笋的δ18O对气候变化的记录特征,在我国西南地区两者与夏季风变化的强弱呈现一种负相关的关系,洞穴石笋初始234U/238U值可以作为一个有用的古气候替代指标来研究古降水的变化。
基金The National Key Basic Research Program from the Ministry of Science and Technology of China under contract Nos 2011CB409801 and 2010DFA24590the National Natural Science Foundation of China under contract No.41240038
文摘234Th is widely used to quantify the magnitude of upper ocean particulate organic carbon （POC） export in oceans. In the present work, the rates of particulate organic carbon export were measured based on the distribution patterns of 234Th/238U disequilibrium in the water column within the continental slope of the East China Sea （ECS） during May 2011. The profiles of particulate and dissolved 234Th activities at all three stations showed a relative deficit with respect to 238U in the upper 100 m of the water column. The dissolved 234Th scavenging rates and the particulate 234Th removal rates and their residence times were calculated by a one-dimensional steady state model. The results showed that the dissolved a34Th scavenging rates and the particulate 234Th removal rates ranged from 12.4-61.4 dpm/（m3.d） and from 3.8-21.8 dpm/（m3.d）, respectively. The residence times of dissolved and particulate 234Th were in the range of 3.4-158 d and 63.7- 96.5 d, respectively. Combined with the measurement of POC/Z34Th ratios of suspended particles, POC export flux （calculated by carbon） from the euphotic zone was estimated in the study region, which ranged from 4.14-14.7 mmol/（m2 .d）, with an average of 8.21 mmol/（m3.d）, occupying 35% of the prime productivity in the study area. The results of this study can provide new information for better understanding the carbon biogeochemical cycle within the continental slope of the ECS.
基金The National Natural Science Foundation of China under contract Nos 41876077 and 41530965the National Key Research and Development Program of China under contract No.2016YFA0601300。
文摘The optimum multiparameter(OMP) method was often used to determine the percentages of water masses based on temperature, salinity and other parameters, like nutrient or dissolved oxygen(DO). There are a number of water masses in the East China Sea(ECS), a marginal sea of the western Pacific Ocean. However, it is difficult to clarify the proportion of water masses using traditional parameters, such as temperature, salinity, nutrient or DO because of the occurring of intensive biogeochemical processes in the near shore and shelf areas. Here, we reported the use of ^(234)U/^(238)Uactivity ratio embedded in the OMP method. The results indicate that seawater in the northern ECS mainly consisted of the estuarine water of Changjiang River(CEW), Kuroshio water(KW), and Yellow Sea Coastal Current(YSCC). In March 2017, the CEW only influenced the offshore waters shallower than30 m;the KW affected the east edge and the YSCC contributed more than 75% in the northern ECS.
基金National Natural Science Foundation of China! 49676296National Scientific and Technical Project! 97-926-04-02.
文摘The spatial and temporal distributions of new production vary largely in different sea areas. To understand the level of new production in the sea area studied better, an estimate of new production must be obtained in large spatial and temporal scales. The ~234Th/ ~238U disequilibrium is an effective method for the study of new production. Two sampling strategies, vertically integrated sampling ap proach based on trapezoidal integration principle and discrete layer sampling approach, were compared in the studies of the xiamen Bay and the northern South China Sea. The scavenging fluxes and removal fluxes of ~234Th and the residence times for dissolved and particulate ~234Th were calculated. The coinci dent results from two Sampling approach suggest that vertically integrated sampling approach is not only effective and reliable, but also significantly reduces the number and volume of samples. It allows us to study new production by ba ^(234)Th - ^(238)U disequilibria in large spatial scale.
基金This work was supported by YPH from the National Science and Technology Research Program of China (Grant No. 97-926-04-02) and the National Natural Science Foundation of China (Grant No. 49676296).
文摘Activities of 234Th and nutrient concentrations in the upper 500 m water column were measured at a time-series station in the South China Sea over a time span of 12.3 d. Results showed a reduction of dissolved 234Th and an overall increase of particulate 234Th during the period. Meanwhile, activities of total 234Th kept fairly constant, implying rapid transformation of 234Th between the dissolved and particulate forms. Vertical profiles of total 234Th showed evident deficit of 234Th relative to 238U in the upper 500 m water column. Using an irreversible steady-state model of thorium scavenging, export fluxes of particulateorganic carbon (POC) corresponding to time points T1 and T2 were estimated to be 46.5 and 13.1 mmolC .m-2. d-1. It was demonstrated that the estimation of POC export was greatly dependent on the POC/234Thp ratios and the bias caused by the different models of 234Th scavenging, however, was considered to be of minor importance.
文摘A simple model is established to describe the fate of particle-reactive pollutants in the Xiamen Bay. Based on the conditional distribution coefficients (Kd ) of chemicals and residence times of particle and waters, the model can be used to predict the fractions of pollutants which would be scavenged to sediments and would escape from the system. The model is calibrated using scavenging data derived from 234 Th - 238U disequilibrium. The fate of a potential pollutant which will be scavenged is a function of the properties of the chemical, of the particle dynamics, and of the waters dynamics in the environment. It is inappropriate to overlook any factor.
基金The work has been prepared with the financial support of Russian Science Foundation(grant 18-77-10027).
文摘In the western part of the South Baikal Basin,spatial-temporal distribution of earthquake epicenters shows quasi-periodic seismic reactivation.The largest earthquakes that occurred in 1999(M_(W)=6.0)and 2008(M_(W)=6.3)fall within seismic intervals of 1994-2003 and 2003-2012,respectively.In the seismic interval that began in 2013,the ^(234)U/^(238)U activity ratio(AR)in groundwater was monitored assuming its dependence on crack opening/closing that facilitated/prevented water circulation in an active boundary fault of the basin.Transitions from disordered,high-amplitude fluctuations of AR values to consistent,low-amplitude fluctuations in different monitoring sites were found to be sensitive indicators of both small seismic events occurring directly on the observation area,and of a large remote earthquake.The hydroisotopic responses to seismic events were consistent with monitoring data on deformation and temperature variations of rocks.The hydroisotopic effects can be applied for detecting a seismically dangerous state of an active fault and prediction of a large future earthquake.
基金supported by the Natural Science Foundation of China (NSFC) through grants 40531007,40676062,10705019by National Key Technology R &D Program for the 11th Five-year Plan Grant(2006BAB18B04)+1 种基金by the commonweal project sponsored by the scientific research foundation of the ministry of science and technology of the people's republic of china(No.2007050228)Chinese IPY Campaign found by MOF and Open Fund of the Key Laboratory of Global Change and Marine-Atmospheric Chemistry(GCMAC),SOA
文摘During the Second Chinese National Arctic Expedition （CHINARE） from July to September 2003, depth profiles of dissolved and particulate 234Th in upper water columns were collected at two stations of BR03 and BR24 in the Bering Sea. 234Th was sampled by using a traditional Fe （OH） 3 co-precipitation technique, which is a reliable approach to 234Th measurement. We observed 234 Wh excess at station BR03 below the euphotic zone, which was possibly due to the intensive remineralization of particulate matter. Particulate organic carbon （POC） export fluxes were estimated from a one-dimensional irreversible steady state model of ^234Th fluxes together with measurements of the POC/^234 Th ratio on the suspended particles. The POC export fluxes from the euphotic zone were II. 66 and I1.69 mmol C m^-2 d^- 1 at BR03 and BR24 stations, respectively. The ratios of POC fluxes to primary production at the two stations were about 0.5 and 0.59, respectively, probably due to the presence of large phytoplankton （in particular diatoms）.
