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1.
234Th-238u 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), 234Th (including both dissolved and particulate) and 238U in the water column at three stations were determined. The profiles of 234Th/238U activity ratio at the three stations all showed consistent 234Th deficit as compared to 238U in the upper 100 m water column. Based on the profiles of the dissolved and particulate 234Th and a steady state box model, the dissolved 234Th scavenging rates, the particulate 234Th 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. 相似文献
2.
To evaluate the particle dynamics and estimate the POC (particulate organic carbon) export flux from the euphotic zone in
the western Arctic Ocean, 234Th-238U 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 234Th/238U activity ratios and the POC/PTh ratios. The average residence times of the particulate and dissolved 234Th in the euphotic zone are 33 d and 121 d, and their average export fluxes are 480 dpm/m2d and 760 dpm/m2d, 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 234Th increases from shelf to basin, while the export fluxes of 234Th decrease. The estimated POC export fluxes from the euphotic zone vary from 2.1 to 20.3 mmol/m2d, indicating that the western Arctic Ocean is an important carbon sink in summer due to efficient biological pump. 相似文献
3.
^234Th-^238U 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）, ^234Th （including both dissolved and particulate） and ^238U in the water column at three stations were determined. The profiles of ^234Th/^238U activity ratio at the three stations all showed consistent ^234Th deficit as compared to ^238U in the upper 100 m water column. Based on the profiles of the dissolved and particulate ^234Th and a steady state box model, the dissolved ^234Th scavenging rates, the particulate ^234Th 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. 相似文献
4.
Size-fractionated 210Po and 210Pb, in the size fractions >0.4 μm, >2 μm and >10 μm, were examined to determine the seasonal variability of particulate fluxes
in Xiamen Bay. Good correlations between 210Po and particulate organic carbon (POC) or non-Particulate Organic Matter (nPOM) suggested that 210Po can be used to trace the export fluxes of POC and nPOM. Both steady-state (SS) model and nSS model were used to evaluate
fluxes of size-fractionated 210Po, results showed that nSS model was better than the SS model in coastal areas. Based on the nSS model, size-fractionated
POC fluxes decreased with increasing particle size. For the particle size studied, maximum POC fluxes occurred in autumn,
followed by spring, winter, and summer. Fluxes of nPOM were an order of magnitude higher than the corresponding size-fractionated
POC fluxes. Differences between size-fractionated nPOM fluxes indicated that hydrodynamic conditions were the main factor
regulating transportation of particulate out of the inner Bay. In winter most particulates, including >10 μm particles, were
transported under the strongest hydrodynamic conditions. In contrast, only a fraction of the <2 μm particulates were transported
from the inner Bay in spring. This study suggested that 210Po is a powerful tracer of seasonal particulate export in coastal seas. 相似文献
5.
A dynamic box model was applied to study the characteristics of biogeochemical cycling of PO_4-P,NO_3-N,AOU,POC and PON in the southern Taiwan Strait region based on field data of the"Minnan Taiwan Bank Fishing Ground Upwelling Ecosystem Study" during the period of Dec.1987-Nov.1988.According to the unique hydrological and topographical features of the region,six boxesand three layers were considered in the model.The variation rates and fluxes of elements induced by hor-izontal current,upwelling,by diffusion,sinking of particles and biogeochemical processes were estimatedrespectively.Results further confirmed that upwellings had important effects in this region.Thenearshore upwelling areas had net input fluxes of nutrients brought by upwelling water,also had high de-pletion rates of nutrients and production rates of particulate organic matter and dissolved oxygen.Theabnormal net production of nutrients in the middle layer(10-30m) indicated the important role of bacte-ria in this high production region.Th 相似文献
6.
Concentrations of dissolved and particulate organic carbon (DOC and POC) were documented in 1996–1997 at 4 different trophic
state stations in Donghu Lake, a typical shallow eutrophic lake along the Changjiang River's middle reaches. The mean concentrations
of DOC were 15.11±3.26, 15.19±4.24, 14.27±3.43, and 13.31±3.30 mg/L in Station I, II, III, and IV, respectively. The DOC concentrations
of the studied area were very similar to that in other lakes along the Changjiang River's middle reaches. The POC mean of
the whole lake was 5.01 mg/L due to the large amount of organic detritus of both allochthonous and autochthonous origin. Significant
linear relationship was found between POC and chlorophyll a at all 4 stations, which presumably reflect that phytoplankton,
its exudates and its metabolic products were the main contributors to the POC pool in the water column. The slope of such
linear relationship at Station IV was significantly steeper than that at Station I, II and III. In addition, the DOC/POC ratios
(mean value: 4.40) indicated that the organic detritus was the most important component of the particulate organic matter;
in other works, next to organic detritus, phytoplankton dominated the particulate organic matter in Donghu Lake.
Project 39770146, 39430101 supported by NSFC and the State Key Laboratory of Freshwater Ecology and Biotechnology, affiliated
to the Institute of Hydrobiology, Chinese Academy of Sciences. 相似文献
7.
Investigation of dissolved organic carbon (DOC) and particulate organic carbon (POC) at 12 stations in Yantal Sishili Bay in May, August, and November of 1997 and March and May of 1998 showed that DOC concentrations varied from 1.14 mg/L to 5.35 mg/L; that the average values at all staticrLs ineach entise varied from 1.52 mg/L to 2.12 mg/L; that POC concentrafions varied from 0.049 mg/L to 1.411mg/L; and averaged 0.159 mg/L to 0.631 mg/L in each cruise. Horizontal distribution of DOC was influ-enced by factors such as continental input, organism activity, temperature, aquieulture environment, etc. The higher POC concentration occurred along the coast. The vertical distribution of DOC and POC changed obviously in spring and summer, but not obviously in autumn and winter. DOC concentration was highest in summer and POC in spring; both were lowest in winter. The seasonal change of DOC was con-sistent with primary productivity seasonal variation, and that of POC was consistent with ehlorophyll-a sea-sanal variation. The seasonal change trend of the C/N ratio of dissolved organic matter was obvious, but the C/N ratio of particulate organic matter had no such trend. 相似文献
8.
MOLAR RATIOS OF C, N, P OF PARTICULATE MATTER AND THEIR VERTICAL FLUXES IN THE YELLOW SEA 总被引：2，自引：0，他引：2
The vertical fluxes and molar ratios of carbon, nitrogen and phosphorus of suspended particulate matter in the Yellow Sea were studied based on the analysis of suspended particulate matter,sediments and sinking particles obtained by use of moored sediment traps. The POC ： PON ratios indicate that most of the particulate organic matter in the Yellow Sea water column comes from marine life rather than the continent. The vertical fluxes of SPM, POC, PON and POP in the Yellow Sea are much higher than those in other seas over the world, and present a typical pattern in shallow epicontinental seas. The estimated residence time of the bioactive elements showed that the speed of the biogeochemical process of materials in the Yellow Sea is much shorter than that in the open ocean as there was high primary productivity in this region. 相似文献
9.
The effects of estuarine processes on the fluxes of inorganic and organic carbon in the Yellow River estuary 总被引：1，自引：0，他引：1
Riverine carbon flux is an important component of the global carbon cycle. The spatial and temporal variations of organic
and inorganic carbon were examined during both dry and wet seasons in the Yellow River estuary. Concentrations of dissolved
organic carbon (DOC) and dissolved inorganic carbon (DIC) in the Yellow River during dry seasons were higher than those during
wet seasons. The effective concentrations of DOC (CDOC*) were higher than the observed DOC at zero salinity. This input of DOC in the Yellow River estuary was due to sediment desorption
processes in low salinity regions. In contrast to DOC, the effective concentrations of DIC were 10% lower than the DIC measured
at freshwater end, and the loss of DIC was caused by CaCO3 precipitation in low salinity region. Particulate organic carbon (POC) and particulate inorganic carbon (PIC) contents of
the particles stabilized to constant values (0.5%±0.05% and 1.8%±0.2%, respectively) within the turbidity maximum zone (TMZ)
and showed no noticeable seasonal variations. A rapid drop of PIC and rise of POC occurred simultaneously outside the TMZ
due to an intense dilution of riverine inorganic-rich particles being transported into a pool of aquatic organic-poor particles
outside the TMZ. Annually, the Yellow River transported 6.95×105 t of DIC, 0.64×105 t of DOC, 78.58×105 t of PIC and 2.29×105 t of POC to the sea. 相似文献
10.
The time scale of transport and reaction processes in the ocean can be evaluated using natural radionuclides of different
half-lives. In the present study, we evaluated the residence times of particulate reactive radionuclides 7Be, 210Pbxs and 234Th in the Changjiang (Yangtze River) estuary, which is a high turbidity estuary, in June, 2006. The residence times of particulate
7Be, 234Thxs and 210Pbxs in the Changjiang estuary were calculated to be 0.7–20.4, 0.18–4.1 and 0.6–89.8 d, respectively. The obtained residence times
of those nuclides are comparable with those of other estuaries and bays. For 234Thxs and 7Be, the residence times decreased with increasing concentrations of suspended particulate matter (SPM); however, those of
210Pbxs increased. Moreover, scavenging residence times of 234Th and 7Be increased from coast to offshore, while those of 210Pbxs decreased. 相似文献
11.
《中国海洋湖沼学报》2021,(5)
The climate variability induced by the El Ni?o-Southern Oscillation(ENSO) cycle drives significant changes in the physical state of the tropical Western Pacific,which has important impacts on the upper ocean carbon cycle.During 2015-2016,a super El Ni?o event occurred in the equatorial Pacific.Suspended particulate matter(SPM) data and related environmental observations in the tropical Western Pacific were obtained during two cruses in Dec.2014 and 2015,which coincided with the early and peak stages of this super El Ni?o event.Compared with the marine environments in the tropical Western Pacific in Dec.2014,an obviously enhanced upwelling occurred in the Mindanao Dome region;the nitrate concentration in the euphotic zone almo st tripled;and the size,mass concentration,and volume concentration of SPM obviously increased in Dec.2015.The enhanced upwelling in the Mindanao Dome region carried cold but eutrophic water upward from the deep ocean to shallow depths,even into the euphotic zone,which disrupted the previously N-limited conditions and induced a remarkable increase in phytoplankton blooms in the euphotic zone.The se results reveal the mechanism of how nutrient-limited ecosystems in the tropical Western Pacific respond to super El Ni?o events.In the context of the ENSO cycle,if predicted changes in biogenic particles occur,the proportion of carbon storage in the tropical Western Pacific is estimated to be increased by more than 52%,ultimately affecting the regional and possibly even global carbon cycle.This paper highlights the prospect for long-term prediction of the impact of a super El Ni?o event on the global carbon cycle and has profound implications for understanding El Ni?o events. 相似文献
12.
ZHANG Man SMYTH Rebecca Ashley ZHU Weixia ZHANG Li LI Yuncong WANG Yifan LI Xuejun GU Qianhong GAO Yunni 《中国海洋湖沼学报》2019,(4)
Studies of Daphnia distribution and function could help people manage and protect water quality.We investigated how spatial distribution and filtering efficiency of Daphnia in the transition and lacustrine zones of the Nanwan Reservoir(China).Samplings were conducted seasonally for 2 years from six sites in the reservoir.Daphnia abundance and biomass were significantly higher in the lacustrine zone than in the transition zone.Similar composition and biomass of edible phytoplankton were found in the two zones,suggesting that food quantity could not explain high Daphnia distribution in the lacustrine zone.The variations of water velocity and food quality could help explaining Daphnia patchy distribution in the reservoir.On the one hand,rapid water velocity can cause the Daphnia decrement in the transition zone.On the other hand,the ratio of particulate organic carbon(POC)to chlorophyll a(chl a)concentration was significantly higher in the transition zone,indicating more allochthonous material constituted the food source for Daphnia.The lower quality food likely suppressed Daphnia development in the transition zone.A linear regression between Daphnia abundance and Secchi depth(SD)may suggest a cause-effect relationship where increased filtering efficiency was responsible for increased water clarity to some extent. 相似文献
13.
Effects of land management practices on labile organic carbon fractions in rice cultivation 总被引：1，自引：1，他引：0
SHAO Jing＇an LI Yangbing WEI Chaofu XIE Deti 《中国地理科学(英文版)》2009,19(3):241-248
A research trial with four land management practices, i.e., traditional tillage-fallow (TTF), traditional tillage-wheat (TTW),
conservation tillage-fallow (CTF) and conservation tillage-wheat (CTW), was sampled in the 15th year after its establishment
to assess the effects of different management practices on labile organic carbon fractions (LOCFs), such as easily oxidizable
organic carbon (EOC), dissolved organic carbon (DOC), particulate organic carbon (POC) and microbial biomass carbon (MBC)
in a typical paddy soil, Chongqing, Southwest China. The results indicated that LOCFs were significantly influenced by the
combination of no-tillage, ridge culture and crop rotation. And, different combination patterns showed different effectiveness
on soil LOCFs. The effects of no-tillage, ridge culture and wheat cultivation on EOC, DOC, POC and MBC mainly happened at
0–10cm. At this depth, soil under CTW had higher EOC, DOC, POC and MBC contents, compared to TTF, TTW and CTF, respectively.
Moreover, the contents of LOCFs for different practices generally decreased when the soil depth increased. Our findings suggest
that the paddy soil in Southwest China could be managed to concentrate greater quantities of EOC, DOC, POC and MBC.
Foundation item: Under the auspices of Key Project of National Natural Science Foundation of China (No. 40231016) 相似文献
14.
Variations of the suspended matter and the particulate organic carbon in the entry of the Gironde Estuary,France 总被引：1，自引：0，他引：1
The effects of using different types of glass fiber filters (GF/F, GF/C) and of sample treatments were evaluated. Studies
on the variation of suspended matter (SM) and particulate organic carbon (POC) showed that: 1) the transversal and day to
night variations are important and must be taken into account in order to get a correct river flux; 2) no regular seasonal
variations of SM and POC were observed, as they are controlled essentially by the climatological, hydrologic, physiochemical,
biological, and geological conditions of the drainage area.
Contribution No 2246 from the Institute of Oceanology, Chinese Academy of Sciences. 相似文献
15.
The effects of using different types of glass fiber filters (GF/F, GF/C) and of sample treatments evaluated. Studies on the variation of suspended matter (SM) and particulate organic carbon (POC) showed that: 1) the transversal and day to night variations are important and must be taken into account in order to get a corrcet river flux; 2) no regular seasonal variations of SM and POC observed, as they are controlled essentially by the climatological, hydrologic, physiochernical, biological, and geological conditions of the drainage area. 相似文献
16.
A WRF-Chem model including a comprehensive gas-phase nitrogen chemistry module was used to simulate a severe dust event appearing in the eastern China on 19-25 March, 2002. The modeling result well reproduced PM10 concentrations in various distances from the dust sources and the transport pathway of the dust strom. The results showed that both the concentrations and the dry deposition fluxes of PM10 increased over the China seas during the dust event following the passage of a cold front system. The maximum fluxes of PM10 in the Yellow Sea and the East China Sea during the dust event were 5.5 and 8.4 times of those before the event, respectively. However, the temporal variations of the dry deposition fluxes of particulate inorganic nitrogen differed over the Yellow Sea from those over the East China Sea. Nitrate and ammonium in the whole northern China rapidly decreased because of the intrusion of dust-loaded air on 19 March. The dust plume arrived in the Yellow Sea on 20 March, decreasing the particulate inorganic nitrogen in mass concentration accordingly. The minimum dry deposition fluxes of nitrate and ammonium in the Yellow Sea were about 3/5 and 1/6 of those before the dust arrival, respectively. In contrast, when the dust plume crossed over the Yangtze Delta area, it became abundant in nitrate and ammonium and increased the concentrations and dry deposition fluxes of particulate inorganic nitrogen over the East China Sea, where the maximum dry deposition fluxes of nitrate and ammonium increased approximately by 4.1 and 2.6 times of those prior to the dust arrival. 相似文献
17.
A field observation was carried out in the Changjiang （Yangtze） River Estuary from May 19 to 26, 2003. A total of 29 stations, including 2 anchored stations, were occupied through almost the whole salinity gradient. Based on the observation data, biogeochemistry of chemical oxygen demand （COD） was examined. Spatial distribution pattern of COD shows that it decreased downstream. The COD concentration varied generally within a narrow range of 1.24-1.60 mg/L in the zone around the river mouth, beyond which it decreased rapidly to 0.20 mg/L. In the mixed water zone, the fluctuation in COD was smaller at 2 m above the bottom layer than at the surface layer in 48 h. In the seawater zone, the 48-h fluctuation at the surface was the largest, followed by that of 5 m below the surface and 2 m above the bottom layers in a range of from 2.50 to 0.55 mg/L. Freshwater discharge was the dominant source of COD in the estuary. The average COD beyond the river mouth was 2.7 mg/L, which accorded with the Chinese seawater quality Grade I. Relationships between dissolved oxygen and biogeochemical parameters such as suspended particulate matter, dissolved organic matter and chlorophyll-a were also discussed. 相似文献
18.
Based on the observed data in monitored drainage areas and GIS spatial analysis tools, watershed basic database of Shitoukoumen Reservoir Basin was built. The multivariate analysis and redundancy analysis (RDA) were used to analyze the spatial and temporal variations of water quality, identify the key environmental factors and their patterns influencing the spatial variation of water quality, and determine the main types and forms of the non-point source (NPS) pollutant export controlled by the key environmental factors. The results show that different patterns of environmental factors lead to great changes in water quality at spatial and seasonal scales. All selected environmental factors explain 64.5% and 68.2% of the spatial variation of water quality over dry season and rainy season, respectively, which shows clear seasonal difference. Over dry season, residential land is the most important environmental factor, which possesses 35.4% of the spatial variation, and drainage area is the second key environmental factor, which possesses 17.0% of spatial variation in the total variance. Over rainy season, slope length and drainage area are the key environmental factors, which possess 29.3% of the spatial variation together. Residential land influences nitrogen export by changing NH4 +-N and particulate organic nitrogen (PON) discharge over dry season, and drainage area controls phosphorus export by regulating dissolved phosphorus (DP) drainage over dry season and phosphorus associated particulate (PAP) loss over rainy season, respectively. Although slope length is an important environmental factor, it does not influence NPS pollutant export. It is interesting that soil organic matter, as a minor environmental factor, highly determines phosphorus and nitrogen export by enhancing the DP, PAP and PON loss. 相似文献
19.
Wind-sand movement characteristics and erosion mechanism of a solar photovoltaic array in the middle of the Hobq Desert,Northwestern China 总被引：1，自引：0，他引：1
《山地科学学报》2021,(5)
The operation and power generation of utility-scale solar energy infrastructure in desert areas are affected by changes in surface erosion processes resulting from the construction of solar photovoltaic(PV) power stations. However, few studies have addressed the interactions between solar PV arrays and aeolian erosion processes. In this study, wind flow field characteristics and the vertical distribution of sediments were investigated in the near-surface transport layer at three different locations with respect to the solar PV arrays in a 200 WM-p PV power station in the central Hobq Desert, northwestern China. The results indicate that the sediment transport varied around the panels, with the greatest transport occurring between the panels, followed by behind and in front of the panels. The sediment fluxes of all of the observation sites obey an exponential function. The secondary flow field zones formed around the PV panels: the conflux accelerating zone between the panels, the resistance decelerating zone of the under panels, and the transition zone of the rapid velocity increase in front of and behind the panels. This resulted in a greater shear force in front of the panels under the downward flow diversion effect of PV panels, and the wind erosion depressions were finally formed here. The results of this study provide information for planning better technical schemes for wind-sand hazards at solar PV power stations, which would ensure operational stability and safety in desert areas. 相似文献
20.
A marine survey was conducted from 18 May to 13 June 2014 in the East China Sea(ECS)and its adjacent Kuroshio Current to examine the spatial distribution and biogeochemical characteristics of dissolved oxygen(DO) in spring. Waters were sampled at 10-25 m intervals within 100 m depth, and at 25-500 m beyond 100 m. The depth, temperature, salinity, and density(sigma-t) were measured in situ with a conductivity-temperature-depth(CTD) sensor. DO concentrations were determined on board using traditional Winkler titration method. The results show that in the Kuroshio Current, DO content was the highest in the euphotic layer, then decreased sharply with depth to about 1 000 m, and increased with depth gradually thereafter. While in the ECS continental shelf area, DO content had high values in the coastal surface water and low values in the near-bottom water. In addition, a low-DO zone of f the Changjiang(Yangtze) River estuary was found in spring 2014, and it was formed under the combined influence of many factors, including water stratification, high primary productivity in the euphotic layers, high accumulation/sedimentation of organic matter below the euphotic layers, and mixing/transport of oceanic current waters on the shelf. Most notable among these is the Kuroshio intruded water, an oceanic current water which carried rich dissolved oxygen onto the continental shelf and alleviated the oxygen deficit phenomenon in the ECS, could impact the position, range, and intensity, thus the formation/destruction of the ECS Hypoxia Zone. 相似文献