In order to elucidate the regional export variation of participate organiccarbon in the western Arctic Ocean, samples vertically integrated between 0 and 100 m depth orbetween 0 and 30 m/40 m depth were collected for ...In order to elucidate the regional export variation of participate organiccarbon in the western Arctic Ocean, samples vertically integrated between 0 and 100 m depth orbetween 0 and 30 m/40 m depth were collected for total ^(234)Th measurements and those from 30 m/40m or 100 m depth were collected for paniculate ^(234)Th measurements during the Second ChineseArctic Expedition in July— September 2003. The removal fluxes and residence time of ^(234)Th in theupper water column were calculated by using irreversible steady-state scavenging model. The resultsshowed that, total ^(234)Th was deficit relative to its parent ^(238)U in the western Arctic Oceanexcept in the western Chukchi shelf and the slope regions around 160°W, indicating that scavengingand removal processes play an important role in element biogeochemical cycle in the Arctic Ocean. Inthe western Chukchi shelf and the slope regions around 160°W, total ^(234)Th was excess relativeto ^(238)U, ascribing to the horizontal input of ^(234)Th adsorbed by ice-rafted sediments.Thorium-234 removal fluxes decreased from the shelf to the deep ocean, while the residence time of^(234)Th increased from shelf to offshore, demonstrating that particle scavenging and removalprocesses are more active in the shelf regions. The estimated POC export fluxes from 40 m in theshelf regions and from 100 m in the slope and deep ocean varied between 1.6 and 27.5 mmol/(m^2·d),and between 1.8 and 14.4 mmol/(m^2·d), respectively. The averaged POC export fluxes over the entirewater column decreased from the shelf to the deep ocean, indicating that the Chukchi shelf is animportant region for organic carbon sequestration. The high ThE ratios (ratio of POC export fluxderived from ^(234)Th/^(238)U disequilibria to primary production) in the western Arctic Oceansuggested that the biological pump runs actively in high-latitudes.展开更多
To evaluate the particle dynamics and estimate the POC (particulate organic carbon) export flux from the euphotic zone in the western Arctic Ocean,234 Th238 U disequilibrium was applied during the second Chinese Natio...To evaluate the particle dynamics and estimate the POC (particulate organic carbon) export flux from the euphotic zone in the western Arctic Ocean,234 Th238 U disequilibrium was applied during the second Chinese National Arctic Research Expedition (July 15-September 26,2003).The POC export fluxes are estimated from the measured profiles of the 234 Th/238 U activity ratios and the POC/PTh ratios.The average residence times of the particulate and dissolved 234 Th in the euphotic zone are 33 d and 121 d,and their average export fluxes are 480 dpm/m 2 d and 760 dpm/m 2 d,respectively.The scavenging and removal processes of particle reactive elements are active in the upper layer of the Chukchi Sea.The average residence time of 234 Th increases from shelf to basin,while the export fluxes of 234 Th decrease.The estimated POC export fluxes from the euphotic zone vary from 2.1 to 20.3 mmol/m 2 d,indicating that the western Arctic Ocean is an important carbon sink in summer due to efficient biological pump.展开更多
210Po and 210Pb are increasingly used to constrain particle dynamics in the open oceans,however they are less used in coastal waters.Here,distributions and partitions of 210Po and 210Pb were examined in the Taiwan Str...210Po and 210Pb are increasingly used to constrain particle dynamics in the open oceans,however they are less used in coastal waters.Here,distributions and partitions of 210Po and 210Pb were examined in the Taiwan Strait,as well as their application to quantify particle sinking.Activity concentrations of dissolved 210Po and 210Pb(<0.6μm)ranged from 1.21 to 7.63 dpm/(100 L)and from 1.07 to 6.33 dpm/(100 L),respectively.Activity concentrations of particulate 210Po and 210Pb varied from 1.96 to 36.74 dpm/(100 L)and from 3.11 to 38.06 dpm/(100 L).Overall,particulate 210Po and 210Pb accounted for the majority of the bulk 210Po and 210Pb.210Po either in dissolved or particulate phases showed similar spatial patterns to 210Pb,indicating similar mechanisms for controlling the distributions of 210Po and 210Pb in the Taiwan Strait.The different fractionation coefficients indicated that particles in the Zhemin Coastal Current(ZCC)inclined to absorb 210Po prior to 210Pb while they showed an opposite effect in the Taiwan Warm Current(TWC).Based on the disequilibria between 210Po and 210Pb,the sinking fluxes of total particulate matter(TPM)were estimated to range from–0.22 to 3.84 g/(m2·d),showing an overall comparable spatial distribution to previous reported sediment accumulation rates.However,our sinking fluxes were lower than the sedimentation rates,indicating a sediment resuspension in winter and horizontal transport of particulate matter from the Taiwan Strait to the East China Sea.展开更多
^(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
A whole year analysis of riverine dissolved organic carbon (DOC) concentrations in the Xijiang River (XJR), South China, showed that the mean riverine DOC concentration (1.24 mg L-1) in the XJR was notably lower than ...A whole year analysis of riverine dissolved organic carbon (DOC) concentrations in the Xijiang River (XJR), South China, showed that the mean riverine DOC concentration (1.24 mg L-1) in the XJR was notably lower than the averaged value (5.75 mg L-1) of the global riverine DOC concentration in several major rivers. There is an inconspicuous monthly fluctuation of the DOC signal in the XJR, but on a semi-yearly time scale, however, the riverine DOC concentration had significant difference between hydrological seasons. The DOC level during the flood season (1.18 mg L-1) was less than that during the non-flood season (1.40 mg L-1). Owing to the concomitance of the flushing and dilution effects of the runoff during the high-water period, the variation of riverine DOC concentration with discharge in the XJR differed from that reported in many other major rivers. The DOC export flux above the city of Wuzhou was about 0.62× 106 g C km-2 yr-1. The DOC transported during the "056" Massive Flood period comprised 30.35% of the annual total, while the discharge accounted for 36.32% of the total annual flow. The characteristics in riverine DOC concentration in the XJR were attributed to the combined effect of the geomorphologic, monsoon climatic and hydrological processes as well as land-use within the drainage basin.展开更多
The coupling of upper ocean-benthic carbon dynamics in the ice-free western Arctic Ocean （the Chukchi Sea and the Canada Basin） was evaluated during the late July-early September 2003 using natural stable （13C） an...The coupling of upper ocean-benthic carbon dynamics in the ice-free western Arctic Ocean （the Chukchi Sea and the Canada Basin） was evaluated during the late July-early September 2003 using natural stable （13C） and radioactive （238U-234Th） isotope tracers. POC export flux estimated from 234Th/238U disequilibria and dissolved CO2 concentration （[CO2（aq）]） pointed out that the strengthened biological pump in the Chukchi Shelf have significantly lowered [CO2（aq）] and altered the magnitude of isotopic （12C/13C） fractionation during carbon fixation in the surface ocean. Further, δ13C signatures of surface sediments （δ13Csed） are positively correlated to those of weighted δ13Cp0C in upper ocean （δ13Csed =13.64＋1.56xδ13Cpoc, r2=0.73, p〈0.01）, suggesting that the POC isotopic signals from upper ocean have been recorded in the sediments, partly due to the rapid export of particles as evidenced by low residence times of the highly particle-reactive 234Th from the upper water column. It is suggested that there probably exists an upper ocean-benthic coupling of carbon dynamics, which likely assures the sedimentary δ13C record an indicator of paleo-CO2 in the western Arctic Ocean.展开更多
Dissolved organic carbon （DOC） is an important component for both carbon cycle and energy balance. The concentration, UV absorbance, and export flux of DOC in the natural environment dominate many important transpor...Dissolved organic carbon （DOC） is an important component for both carbon cycle and energy balance. The concentration, UV absorbance, and export flux of DOC in the natural environment dominate many important transport processes. To better understand the temporal and spatial variation of DOC, 7 sites along the Lower Dagu River were chosen to conduct a comprehensive measure- ment from March 2013 to February 2014. Specifically, water samples were collected from the Lower Dagu River between the 26th and 29th of every month during the experimental period. The DOC concentration （Cooc） and UV absorbance were analyzed using a total organic carbon analyzer and the ultraviolet-visible absorption spectrum, and the DOC export flux was estimated with a simple empirical model. The results showed that the CDoc of the Lower Dagu River varied from 1.32 to 12.56 mg/L, consistent with global rivers. The CDoc and UV absorbance showed significant spatial variation in the Dagu River during the experiential period because of the upstream natural processes and human activities in the watershed. The spatial variation is mainly due to dam or reservoir constructions, riverside ecological environment changes, and non-point source or wastewater discharge. The seasonal variation of CDoc was mainly related to the source of water DOC, river runoff, and temperature, and the UV absorbance and humification degree of DOC had no obvious differences among months （P〈 0.05）. UV absorbance was applied to test the CDOC in Lower Dagu River using wave lengths of 254 and 280 nm. The results revealed that the annual DOC export flux varied from 1.6 to 3.76x 105 g C^rn2/yr in a complete hydrological year, significantly lower than the global average. It is worth mentioning that the DOC export flux was mainly concentrated in summer （-90% of all-year flux in July and August）, since the runoff in the Dagu River took place frequently in summer. These observations implied environment change could bring the temporal-spatial variation of DOC and the exports, which would further affect the land-ocean interactions in the Lower Dagu River and the global carbon cycle.展开更多
基金supported by the Program for New Century Excellent Talents in University of China under contract No.NCET-04-0593 and the Chinese Second Arctic Expedition Foundation.
文摘In order to elucidate the regional export variation of participate organiccarbon in the western Arctic Ocean, samples vertically integrated between 0 and 100 m depth orbetween 0 and 30 m/40 m depth were collected for total ^(234)Th measurements and those from 30 m/40m or 100 m depth were collected for paniculate ^(234)Th measurements during the Second ChineseArctic Expedition in July— September 2003. The removal fluxes and residence time of ^(234)Th in theupper water column were calculated by using irreversible steady-state scavenging model. The resultsshowed that, total ^(234)Th was deficit relative to its parent ^(238)U in the western Arctic Oceanexcept in the western Chukchi shelf and the slope regions around 160°W, indicating that scavengingand removal processes play an important role in element biogeochemical cycle in the Arctic Ocean. Inthe western Chukchi shelf and the slope regions around 160°W, total ^(234)Th was excess relativeto ^(238)U, ascribing to the horizontal input of ^(234)Th adsorbed by ice-rafted sediments.Thorium-234 removal fluxes decreased from the shelf to the deep ocean, while the residence time of^(234)Th increased from shelf to offshore, demonstrating that particle scavenging and removalprocesses are more active in the shelf regions. The estimated POC export fluxes from 40 m in theshelf regions and from 100 m in the slope and deep ocean varied between 1.6 and 27.5 mmol/(m^2·d),and between 1.8 and 14.4 mmol/(m^2·d), respectively. The averaged POC export fluxes over the entirewater column decreased from the shelf to the deep ocean, indicating that the Chukchi shelf is animportant region for organic carbon sequestration. The high ThE ratios (ratio of POC export fluxderived from ^(234)Th/^(238)U disequilibria to primary production) in the western Arctic Oceansuggested that the biological pump runs actively in high-latitudes.
基金Supported by the National Natural Science Foundation of China (No.40531007)the China Action Plan of the International Polar Year (Nos.2009DFA22920 and 2008Po5040014-03)+1 种基金the International Science and Technology Cooperation (Nos. 2008DFA20420 and 2009DFA22920)the Polar Atmospheric Environment Remote Sensing Monitoring Technique of the National High Technology Research and DevelopmentProgram of China (863 Program) (No. N2008DFA20420)
文摘To evaluate the particle dynamics and estimate the POC (particulate organic carbon) export flux from the euphotic zone in the western Arctic Ocean,234 Th238 U disequilibrium was applied during the second Chinese National Arctic Research Expedition (July 15-September 26,2003).The POC export fluxes are estimated from the measured profiles of the 234 Th/238 U activity ratios and the POC/PTh ratios.The average residence times of the particulate and dissolved 234 Th in the euphotic zone are 33 d and 121 d,and their average export fluxes are 480 dpm/m 2 d and 760 dpm/m 2 d,respectively.The scavenging and removal processes of particle reactive elements are active in the upper layer of the Chukchi Sea.The average residence time of 234 Th increases from shelf to basin,while the export fluxes of 234 Th decrease.The estimated POC export fluxes from the euphotic zone vary from 2.1 to 20.3 mmol/m 2 d,indicating that the western Arctic Ocean is an important carbon sink in summer due to efficient biological pump.
基金The National Natural Science Foundation of China under contract Nos 41076043 and 51608142the Guangxi Young and Middle-aged Teachers’ Basic Ability Upgrading Project under contract No.2019KY0298the Guangxi Science and Technology Planning Project under contract No.Gui Ke-AD18126018
文摘210Po and 210Pb are increasingly used to constrain particle dynamics in the open oceans,however they are less used in coastal waters.Here,distributions and partitions of 210Po and 210Pb were examined in the Taiwan Strait,as well as their application to quantify particle sinking.Activity concentrations of dissolved 210Po and 210Pb(<0.6μm)ranged from 1.21 to 7.63 dpm/(100 L)and from 1.07 to 6.33 dpm/(100 L),respectively.Activity concentrations of particulate 210Po and 210Pb varied from 1.96 to 36.74 dpm/(100 L)and from 3.11 to 38.06 dpm/(100 L).Overall,particulate 210Po and 210Pb accounted for the majority of the bulk 210Po and 210Pb.210Po either in dissolved or particulate phases showed similar spatial patterns to 210Pb,indicating similar mechanisms for controlling the distributions of 210Po and 210Pb in the Taiwan Strait.The different fractionation coefficients indicated that particles in the Zhemin Coastal Current(ZCC)inclined to absorb 210Po prior to 210Pb while they showed an opposite effect in the Taiwan Warm Current(TWC).Based on the disequilibria between 210Po and 210Pb,the sinking fluxes of total particulate matter(TPM)were estimated to range from–0.22 to 3.84 g/(m2·d),showing an overall comparable spatial distribution to previous reported sediment accumulation rates.However,our sinking fluxes were lower than the sedimentation rates,indicating a sediment resuspension in winter and horizontal transport of particulate matter from the Taiwan Strait to the East China Sea.
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.
基金supported by the Natural Science Foundation of China (Grant Nos. 40871143 and 41071054)funds of China Geological Survey (karst[2011] Geo-surveying 01-01-23)+1 种基金the Fundamental Research Funds for the Central Universitiesthe Guangdong Provincial Natural Science Foundation of China (Grant No. 7003669)
文摘A whole year analysis of riverine dissolved organic carbon (DOC) concentrations in the Xijiang River (XJR), South China, showed that the mean riverine DOC concentration (1.24 mg L-1) in the XJR was notably lower than the averaged value (5.75 mg L-1) of the global riverine DOC concentration in several major rivers. There is an inconspicuous monthly fluctuation of the DOC signal in the XJR, but on a semi-yearly time scale, however, the riverine DOC concentration had significant difference between hydrological seasons. The DOC level during the flood season (1.18 mg L-1) was less than that during the non-flood season (1.40 mg L-1). Owing to the concomitance of the flushing and dilution effects of the runoff during the high-water period, the variation of riverine DOC concentration with discharge in the XJR differed from that reported in many other major rivers. The DOC export flux above the city of Wuzhou was about 0.62× 106 g C km-2 yr-1. The DOC transported during the "056" Massive Flood period comprised 30.35% of the annual total, while the discharge accounted for 36.32% of the total annual flow. The characteristics in riverine DOC concentration in the XJR were attributed to the combined effect of the geomorphologic, monsoon climatic and hydrological processes as well as land-use within the drainage basin.
基金Chinese Polar Environment Comprehensive Investigation and Assessment Programs under contract Nos CHINARE 2014-03-04-03 and CHINARE 2014-04-03-05the National Natural Science Foundation of China under contract Nos 41125020 and 41206062+2 种基金a special scientific research project for public welfare under contract No.201105022-4the research project supported by the State Oceanic Administration under contract No.GASI-03-01-02-02the Natural Science Foundation of Fujian Province of China under contract No.2014J05049
文摘The coupling of upper ocean-benthic carbon dynamics in the ice-free western Arctic Ocean （the Chukchi Sea and the Canada Basin） was evaluated during the late July-early September 2003 using natural stable （13C） and radioactive （238U-234Th） isotope tracers. POC export flux estimated from 234Th/238U disequilibria and dissolved CO2 concentration （[CO2（aq）]） pointed out that the strengthened biological pump in the Chukchi Shelf have significantly lowered [CO2（aq）] and altered the magnitude of isotopic （12C/13C） fractionation during carbon fixation in the surface ocean. Further, δ13C signatures of surface sediments （δ13Csed） are positively correlated to those of weighted δ13Cp0C in upper ocean （δ13Csed =13.64＋1.56xδ13Cpoc, r2=0.73, p〈0.01）, suggesting that the POC isotopic signals from upper ocean have been recorded in the sediments, partly due to the rapid export of particles as evidenced by low residence times of the highly particle-reactive 234Th from the upper water column. It is suggested that there probably exists an upper ocean-benthic coupling of carbon dynamics, which likely assures the sedimentary δ13C record an indicator of paleo-CO2 in the western Arctic Ocean.
文摘Dissolved organic carbon （DOC） is an important component for both carbon cycle and energy balance. The concentration, UV absorbance, and export flux of DOC in the natural environment dominate many important transport processes. To better understand the temporal and spatial variation of DOC, 7 sites along the Lower Dagu River were chosen to conduct a comprehensive measure- ment from March 2013 to February 2014. Specifically, water samples were collected from the Lower Dagu River between the 26th and 29th of every month during the experimental period. The DOC concentration （Cooc） and UV absorbance were analyzed using a total organic carbon analyzer and the ultraviolet-visible absorption spectrum, and the DOC export flux was estimated with a simple empirical model. The results showed that the CDoc of the Lower Dagu River varied from 1.32 to 12.56 mg/L, consistent with global rivers. The CDoc and UV absorbance showed significant spatial variation in the Dagu River during the experiential period because of the upstream natural processes and human activities in the watershed. The spatial variation is mainly due to dam or reservoir constructions, riverside ecological environment changes, and non-point source or wastewater discharge. The seasonal variation of CDoc was mainly related to the source of water DOC, river runoff, and temperature, and the UV absorbance and humification degree of DOC had no obvious differences among months （P〈 0.05）. UV absorbance was applied to test the CDOC in Lower Dagu River using wave lengths of 254 and 280 nm. The results revealed that the annual DOC export flux varied from 1.6 to 3.76x 105 g C^rn2/yr in a complete hydrological year, significantly lower than the global average. It is worth mentioning that the DOC export flux was mainly concentrated in summer （-90% of all-year flux in July and August）, since the runoff in the Dagu River took place frequently in summer. These observations implied environment change could bring the temporal-spatial variation of DOC and the exports, which would further affect the land-ocean interactions in the Lower Dagu River and the global carbon cycle.
