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
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
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
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）.
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.
