Subterranean estuaries(STE)are important seawater-groundwater mixing zones with complex biogeochemical processes,which play a vital role in the migration and transformation of dissolved materials.In this study,we firs...Subterranean estuaries(STE)are important seawater-groundwater mixing zones with complex biogeochemical processes,which play a vital role in the migration and transformation of dissolved materials.In this study,we first investigated the spatial distributions of dissolved inorganic nitrogen(DIN),dissolved inorganic phosphorous(DIP),dissolved inorganic silicon(DSi)and metal elements(As,Ba,Cr,Cu,Fe,Mn,Ni,Pb,and Zn)in STE including upper intertidal,seepage face and subtidal zones.We then estimated submarine groundwater discharge(SGD)and associated nutrient and metal element fluxes.From the generalized Darcy’s law method,SGD was estimated to be 30.13 cm/d,which was about 7 times larger than the inflow(4.16 cm/d).The nutrient and metal fluxes from SGD were estimated to be(5.33±4.99)mmol/(m^(2)·d)for DIN,(0.22±0.03)mmol/(m^(2)·d)for DIP,(16.20±2.05)mmol/(m^(2)·d)for DSi,(1325.06±99.10)μmol/(m^(2)·d)for Fe,(143.41±25.13)μmol/(m^(2)·d)for Mn,(304.06±81.07)μmol/(m^(2)·d)for Zn,(140.21±13.33)μmol/(m^(2)·d)for Cu,(84.49±2.94)μmol/(m^(2)·d)for Pb,(37.38±5.51)μmol/(m^(2)·d)for Ba,(27.88±3.89)μmol/(m^(2)·d)for Cr,(10.10±6.33)μmol/(m^(2)·d)for Ni,and(6.25±3.45)μmol/(m^(2)·d)for As.The nutrient and metal fluxes from SGD were relatively higher than those from the inflow,suggesting that nearshore groundwater acted as the sources of nutrients and metal elements discharging into the sea.The environmental potential pollution of coastal seawater was evaluated by pollution factor index(Pi),comprehensive water quality index(CWQI),and ecological risk index(ERI).Pb mainly caused potential danger of nearshore environment with considerable contamination(Pi=5.78±0.19),heavy pollution(CWQI=4.09)and high ecological risk(ERI=18.00).This study contributed to better understanding the behavior of nutrients and metal elements and improving the sustainable management of STE under the pressure of anthropogenic activities and climate change.展开更多
Submarine groundwater discharge(SGD),which can be traced using naturally occurring radium isotopes,has been recognized as a significant nutrient source and land-ocean interaction passage for the coastal waters of the ...Submarine groundwater discharge(SGD),which can be traced using naturally occurring radium isotopes,has been recognized as a significant nutrient source and land-ocean interaction passage for the coastal waters of the Daya Bay,China.However,uncertainties in assessing SGD fluxes must still be discussed in detail.In this study,we attempted to utilize the Monte Carlo method to evaluate the uncertainties of radium-derived SGD flux in the northeast and entirety of the Daya Bay.The results show that the uncertainties of the SGD estimate in the northeast bay are very sensitive to variations in excess radium inventories as well as radium inputs from bottom sediments,while the uncertainties of the SGD estimate for the entire bay are strongly affected by fluctuations in radium inputs from bottom sediments and radium end-members of SGD.This study will help to distinguish the key factors controlling the accuracy of SGD estimates in similar coastal waters.展开更多
The response of zooplankton to the ecological environment in Daya Bay is unclear under the influence of both climate changes and anthropogenic activities on a seasonal to inter-annual scale.Based on monthly surveys an...The response of zooplankton to the ecological environment in Daya Bay is unclear under the influence of both climate changes and anthropogenic activities on a seasonal to inter-annual scale.Based on monthly surveys and historical data,we found the zooplankton community had changed temporally and spatially.A total of 134 species was recorded during the study,and copepods dominated numerically in terms of diversity and abundance.Both copepods and cladocerans were the main contributors to zooplankton abundance.The community structure of zooplankton was temporally classified into the warm and cold groups,and spatially into the three groups located in the marine cage-culture area(MCCA),the outflow of nuclear power plants(ONPP)and unpolluted waters(UPW).The zooplankton was characterized by low biomass(dry weight),high diversity and abundance in the warm period in contrast to that in the cold period.Compared with the other two groups,the MCCA group of zooplankton showed high abundance,low diversity and biomass.Variations in dominant species were closely related to temperature,salinity and chlorophyll a concentration.Species diversity and dry weight decreased in comparison with 30 years ago,while zooplankton abundance increased.The seasonal variation in zooplankton was affected mainly by temperature that was controlled by monsoon,while the spatial difference in the community structure was probably due to eutrophication in the MCCA and thermal water discharge from ONPP.The zooplankton community is undergoing great changes with the tendency of miniaturization and gelatinization in recent 30 years in Daya Bay.展开更多
The increase of water temperature, due to thermal discharges from two nuclear power stations, was one of the most significant environmental changes since 1982 in the Daya Bay, located in the north of the South China S...The increase of water temperature, due to thermal discharges from two nuclear power stations, was one of the most significant environmental changes since 1982 in the Daya Bay, located in the north of the South China Sea. This study investigates the long-term (1982-2012) environmental changes in Daya Bay in response to the increase of water temperature, via comprehensively interpreting and analyzing both satellite and in situ observations along with previous data. The results show that: 1) salinity, dissolved oxygen (DO), chemical oxygen demand (COD) and nutrients had been enhanced after the thermal discharges started in 1994;2) the concentration of Chl-a increased while the net-phytoplankton abundance decreased;3) diversity of the phytoplankton community had decreased;4) fishery production had declined;and 5) frequency of Harmful Algal Bloom occurrence had increased. Satellite images show clearly that a thermal plume from the power stations extended toward the interior of Daya Bay, and that surface temperature of the seawater increased as one approached the power stations. The analysis suggests that the thermal water discharged from the two power stations was a driver of the ecosystem’s change in Daya Bay. Several factors, including nutrients, salinity, DO, and COD, varied according to the increase of water temperature. These factors affected the water quality, Chl-a, and phytoplankton in the short term and impaired aquatic organisms and the whole ecosystem in the long term.展开更多
Weathered troughs are frequently encountered in granites. They can cause problems to tunneling in the rocks and have to be properly addressed. The structures or spatial shapes of weathered troughs were seldom clarifie...Weathered troughs are frequently encountered in granites. They can cause problems to tunneling in the rocks and have to be properly addressed. The structures or spatial shapes of weathered troughs were seldom clarified in the past. In this paper, four weathered troughs are identified by means of geophysical exploration, core drilling, logging, and in-situ stress measurement at Daya Bay reactor-neutrino experiment site in Shenzhen, China. The weathered troughs are exposed on the ground or partially covered by grass and soils, which will threaten the safety of horizontal tunneling at a shallow depth. High electrical resistivity (HER) method is adopted for its feasibility and practicality, in combination with field geological observation, ultrasonic televiewer in boreholes and in-situ stress measurement. By comparing the HER values of completely decomposed to fresh rocks, it is indicated that the HER values of weathered troughs in natural state are 0.4-100 D.m, and the in-situ stress is abnormally lower than those at upper and lower layers. Field investigations show that the depths of the four weathered troughs are 30-182 m, with bottom elevation over 10 m. The volume of each weathered trough is mostly over lx l 0^6 m3 in inverted conic form. The weathered troughs often occur in various kinds of landforms, such as ridges, gullies or gently dipping dish-like depression areas. Faults and boundaries of different granitic plutons as well as joints govern the formation, locations and strikes of these troughs under development.展开更多
In this study, the horizontal and vertical distribution of primary production(PP) and its monthly variations were described based on field data collected from the Daya Bay in January–December of 2016. The relationshi...In this study, the horizontal and vertical distribution of primary production(PP) and its monthly variations were described based on field data collected from the Daya Bay in January–December of 2016. The relationships between PP and environmental factors were analyzed using a general additive model(GAM). Significant seasonal differences were observed in the horizontal distribution of PP, while vertical distribution showed a relatively consistent unimodal pattern. The monthly average PP(calculated by carbon) ranged from 48.03 to 390.56 mg/(m~2·h),with an annual average of 182.77 mg/(m~2·h). The highest PP was observed in May and the lowest in November.Additionally, the overall trend in PP was spring>summer>winter>autumn, and spring PP was approximately three times that of autumn PP. GAM analysis revealed that temperature, bottom salinity, phytoplankton, and photosynthetically active radiation(PAR) had no significant relationships with PP, while longitude, depth, surface salinity, chlorophyll a(Chl a) and transparency were significantly correlated with PP. Overall, the results presented herein indicate that monsoonal changes and terrestrial and offshore water systems have crucial effects on environmental factors that are associated with PP changes.展开更多
Harmful algal blooms(HABs),such as dinoflagellate blooms,have adverse eff ects on coastal water environments,causing seafood contamination and aquaculture economic losses.Based on historical HAB records data(1983-2017...Harmful algal blooms(HABs),such as dinoflagellate blooms,have adverse eff ects on coastal water environments,causing seafood contamination and aquaculture economic losses.Based on historical HAB records data(1983-2017)and phytoplankton data(1982-2008),field investigation and laboratory experiments on frequently bloomed dinoflagellate species,we analyzed the possible mechanisms of high frequency dinoflagellate blooms in Daya Bay,South China Sea.The HAB records data show that the proportion of dinoflagellate blooms increased from 15% before 1994 to 77.27% after 2011.The bloom occurred mostly in summer(57.58%)in Yaling Bay(76.92%).The species inducing dinoflagellate blooms tended to be singular over time,with high proportion of Scrippsiella trochoidea(42.86%-88.88%).Laboratory experiment and field investigation of S.trochoidea bloom showed that this species grew rapidly at 30℃ and 32.1℃(r=0.47,P<0.05),respectively.Results indicate that temperature rise in Yaling Bay was aff ected by nearby nuclear plant effluent,which favored the S.trochoidea bloom.Coincidently,nearly 70% of S.trochoidea blooms occurred in about 7 days after local spring tide and strong wind(wind velocity>7 m/s),which disturbed the resting cysts in the sediment and bring them into surface layer.Taking into account of environmental parameters,algae source,and atmospheric conditions,the probable mechanism of S.trochoidea bloom could be explained.The cysts were resuspended by the spring tide or strong wind,germinated at the bottom layer,reproduced rapidly at higher temperature,and then aggregated in the inner bay(Yaling Bay),resulting the frequent S.trochoidea bloom.Considering the influences of global warming and human activities,it should be taken more attention that dinoflagellate blooms might increase along the coastal waters.展开更多
The purpose of this study is to detail the ecological characteristics of phytoplankton in waters around the Daya Bay Nuclear Power Station in Guangdong (GNPS) (Fig. 1) in spring, the bloom period of algae. The collect...The purpose of this study is to detail the ecological characteristics of phytoplankton in waters around the Daya Bay Nuclear Power Station in Guangdong (GNPS) (Fig. 1) in spring, the bloom period of algae. The collections with a small temporal scale of every three days were made during 30 cruises from March to May in 1987. Such an investigation has never been carried out before in China except that the seasonal distribution and composition of phytoplankton in these regions were reported in展开更多
[Objective] The paper was to quantitatively evaluate the maintenance effect of summer fishing moratorium (SFM) in Daya Bay. [Method]Based on satellite remote sensing and trawl surveys, the changes in sea surface tem...[Objective] The paper was to quantitatively evaluate the maintenance effect of summer fishing moratorium (SFM) in Daya Bay. [Method]Based on satellite remote sensing and trawl surveys, the changes in sea surface temperature (SST) , chlorophyll a (Chla) concentration, catchper unit effort (CPUE), biodiversity, species composition, body length and weight of total catch in Daya Bay before SFM (May 2015) and after SFM(August 2015) were comparatively analyzed. [Result] The CPUE of total catch mainly distributed from 0-10 kg/h before SFM to 0-40 kg/h afterSFM. The average body length and weight of catches increased, indicating that the growth rate of catches was accelerated. The indices of ShannonWiener diversity index (H忆) and Pielou evenness index(J忆) increased by 0.36 and 0.14, respectively, indicating that the community structure wasimproved. The biomass spectra of fishery resources community suggested that the slopes of normalized biomass spectra after SFM was greater than-1, and the biomass of fishery resources increased with the increase of individual body weight after SFM. SFM reduced offshore fishing intensity,recovered and conserved the fishery resources in Daya Bay. [Conclusion] In order to improve the SFM system and promote the sustainable development of coastal fishery resources, it is suggested to prolong the time of SFM appropriately, reduce the number of coastal fishing boats, and strengthen the conservation of fish resources.展开更多
The marine environment, productivity and potential biotic resources in the waters of the Daya Bay were investigated by South China Sea Institute of Oceanology, Academia Sinica from 1984 to 1986. The present paper deal...The marine environment, productivity and potential biotic resources in the waters of the Daya Bay were investigated by South China Sea Institute of Oceanology, Academia Sinica from 1984 to 1986. The present paper deals mainly with the annual variation and distribution characteristics in chlorophyll a and with some of the ecological factors involved in chlorophyll distribution within the bay. Correlation models are established and discussed. The results could be helpful for further probing into ecosystem and for the exploitation-utilization of aquatic resources in this region.展开更多
The surface sediment samples were collected month by month at nine stations in the Daya Bay from January to December 1987, and the number of anaerobic sulfite reducing bacteria and their spores and the regularity of s...The surface sediment samples were collected month by month at nine stations in the Daya Bay from January to December 1987, and the number of anaerobic sulfite reducing bacteria and their spores and the regularity of seasonal change were determined. The effect of environmental factors, water temperature and the resoluble oxygen concentration in the bottom of seawater on the number of them were discussed. The results show that the number of anaerobic su|fite reducing bacteria were low in sediment of the Daya Bay, indicating that the hay was less contaminated.展开更多
The Daya Bay Nuclear Power Plant in South China’s Guangdong Province began its second refueling and maintenance work for its Unit 1 on March 31, 1996. Apart from the regular work required by the plant’s annual check...The Daya Bay Nuclear Power Plant in South China’s Guangdong Province began its second refueling and maintenance work for its Unit 1 on March 31, 1996. Apart from the regular work required by the plant’s annual check- up plan, all of the present guide tubes of the control rods in Unit I will be replaced by the type of state-of-the-art tubes used in Unit 2, to make the dropping-time of the tubes more accurate. The annual check may take 80 days, thus the unit will probably re-connect with the power grid in mid June. As for Unit 2, the "exciter" of generator malfunctioned during the start of the reactor on March 6, when the second refueling and maintenance neared completion.展开更多
Objective:To investigate the radioactivity levels of seawater,sediments,and biota in the Daya Bay sea area,China,in order to establish the radioactivity baseline values,and provide basic data for the assessment of pot...Objective:To investigate the radioactivity levels of seawater,sediments,and biota in the Daya Bay sea area,China,in order to establish the radioactivity baseline values,and provide basic data for the assessment of potential radiological risks that might result from the application of nuclear technology or human activities.Methods:Samples of seawater,sediments,and biota were collected from the Daya Bay sea area and analyzed.Their radioactivity baseline data were then compared with information from other regions in China and around the world reported in related literature.Results:For the seawater samples,the activity concentrations of natural radionuclide ^(40)K were 9.9-10.4 Bq/L,while ^(238)U,226Ra,^(210)Pb,^(137)Cs,and ^(110)Ag^(m) were below the minimum detectable activity(MDA).Regarding the sediment samples,the activity concentrations of ^(238)U,^(228)Ra,^(226)Ra,^(210)Pb,^(40)K,and ^(137)Cs were 38.1-40.4,49.1-53.7,32.6-38.6,59-95,590-650,and 0.48-0.88 Bq/(kg dry weight),respectively,while ^(110)Agm was below the MDA.For the marine shrimps in the biota samples,the activity concentrations of ^(228)Ra,^(226)Ra,^(40)K,and ^(137)Cs were 1.14-2.75,0.17-0.43,63-76,and 0.038-0.045 Bq/(kg wet weight),respectively,while ^(238)U,^(210)Pb,and ^(110)Agm were all below the MDA.Furthermore,for the marine fishes in the biota samples,the activity concentrations of ^(228)Ra,^(226)Ra,^(210)Pb,^(40)K,and ^(137)Cs were 2.1-19.7,0.32-3.78,<2.2-2.8,59-70,and<0.007-0.026 Bq/(kg wet weight),respectively,while ^(238)U and ^(110)Ag^(m) were all below the MDA.^(228)Ra was found to be concentrated in Osteomugil ophuyseni with 19.7 Bq/(kg wet weight).Conclusions:The radioactivity levels of seawater and marine sediments in the Daya Bay sea area are within the range of the normal background values.Osteomugil ophuyseni exhibited higher concentrations of ^(228)Ra than other species in this study,while the other species in the biota show no significant difference in the radioactivity levels from data in relevant literature.展开更多
We report an improved measurement of the neutrino mixing angle θ13 from the Daya Bay Reactor Neutrino Experiment. We exclude a zero value for sin22θ13 with a significance of 7.7 standard deviations. Electron antineu...We report an improved measurement of the neutrino mixing angle θ13 from the Daya Bay Reactor Neutrino Experiment. We exclude a zero value for sin22θ13 with a significance of 7.7 standard deviations. Electron antineutrinos from six reactors of 2.9 GWm th were detected in six antineutrino detectors deployed in two near (flux-weighted baselines of 470 m and 576 m) and one far (1648 m) underground experimental halls. Using 139 days of data, 28909 (205308) electron antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to the expected number of antineutrinos assuming no oscillations at the far hall is 0.944± 0.007(stat.) ± 0.003(syst.). An analysis of the relative rates in six detectors finds sin22θ13=0.089± 0.010(stat.)±0.005(syst.) in a three-neutrino framework.展开更多
Detailed measurements of Hamamatsu R5912 photomultiplier signals are presented, including the single photoelectron charge response, waveform shape, nonlinearity, saturation, overshoot, oscillation, prepulsing, and aft...Detailed measurements of Hamamatsu R5912 photomultiplier signals are presented, including the single photoelectron charge response, waveform shape, nonlinearity, saturation, overshoot, oscillation, prepulsing, and afterpulsing. The results were used to build a detailed model of the PMT signal characteristics over a wide range of light intensities. Including the PMT model in simulated Daya Bay particle interactions shows no significant systematic effects that are detrimental to the experimental sensitivity.展开更多
A new measurement of the reactor antineutrino flux and energy spectrum by the Daya Bay reactor neutrino experiment is reported. The antineutrinos were generated by six 2.9 GWth nuclear reactors and detected by eight a...A new measurement of the reactor antineutrino flux and energy spectrum by the Daya Bay reactor neutrino experiment is reported. The antineutrinos were generated by six 2.9 GWth nuclear reactors and detected by eight antineutrino detectors deployed in two near(560 m and 600 m flux-weighted baselines) and one far(1640 m flux-weighted baseline) underground experimental halls. With 621 days of data, more than 1.2 million inverse beta decay(IBD) candidates were detected. The IBD yield in the eight detectors was measured, and the ratio of measured to predicted flux was found to be 0.946±0.020(0.992±0.021) for the Huber+Mueller(ILL+Vogel) model. A 2.9σ deviation was found in the measured IBD positron energy spectrum compared to the predictions. In particular, an excess of events in the region of 4–6 MeV was found in the measured spectrum, with a local significance of 4.4σ. A reactor antineutrino spectrum weighted by the IBD cross section is extracted for model-independent predictions.展开更多
GPS-based surface drifters were used to investigate the surface currents in Daya Bay and along the eastern Guangdong coast in China.Surface current vectors were measured based on the GPS location and corresponding tim...GPS-based surface drifters were used to investigate the surface currents in Daya Bay and along the eastern Guangdong coast in China.Surface current vectors were measured based on the GPS location and corresponding time information sent by drifters through the mobile phone network.The analysis of data from 120 drifters,deployed in late spring 2018 in the case-study region,shows that the drifters are generally capable of capturing the surface(tidal and residual)currents.The drifter trajectories suggest an anticlockwise surface current inside Daya Bay and a north-eastward current along the eastern Guangdong coast,where the coastal current along the eastern Guangdong coast is faster than that inside Daya Bay.The surface currents in the investigated region follow an irregular semidiurnal cycle due to the influence of the tidal current,while the currents inside Daya Bay are strongly affected by the topography.According to the harmonic analysis,an irregular semidiurnal type of tidal current is evident at a study grid inside Daya Bay,with an Eulerian residual current speed of 9.0 cm/s and a direction of 276°.The Lagrangian residual current outside Daya Bay moves north-eastward with a mean speed of 22 cm/s along the eastern Guangdong coast,while the current inside Daya Bay moves northward to the bay head with a mean speed of about 8.0 cm/s,which agrees well with the one reported in other literatures.展开更多
The impact on the environment ofradionuclide release from nuclear power plants has attracted increased attention, especially after the accident at Fukushima Daiichi Nuclear Power Plant in Japan. Based on the mechanism...The impact on the environment ofradionuclide release from nuclear power plants has attracted increased attention, especially after the accident at Fukushima Daiichi Nuclear Power Plant in Japan. Based on the mechanisms of adsorption/desorption at solid/liquid interfaces and a surface micromorphology model of sediments, a theoretical expression of the distribution coefficient Kd is derived. This coefficient has significant effects on the distribution of radionuclide in seawater, suspended sediment and seabed sediment. Kd is then used to simulate ^90Sr transport in the sea near the Daya Bay Nuclear Power Plant. The simulation results are compared with field measurements of tidal level, current velocity, suspended sediment concentration and ^90Sr concentrations in the same period. Overall, the simulated results agree well with the field measured data. Thus, the derived expression for Ka is capable of interpreting realistic adsorption/desorption processes. What's more, conclusion is drawn that about 40% ^90Sr released by Daya Bay Nuclear Power Plant will be adsorbed by suspended sediment and 20% by seabed sediment, only about 40% ^90St will remain in the sea near Daya Bay Nuclear Power Plant in South China Sea.展开更多
The Daya Bay Reactor Neutrino Experiment started running on September 23, 2011. The offiine computing environment, consisting of 11 servers at Daya Bay, was built to process onsite data. With the current computing abi...The Daya Bay Reactor Neutrino Experiment started running on September 23, 2011. The offiine computing environment, consisting of 11 servers at Daya Bay, was built to process onsite data. With the current computing ability, onsite data processing is running smoothly. The Performance Quality Monitoring system (PQM) has been developed to monitor the detector performance and data quality. Its main feature is the ability to efficiently process multiple data streams from the three experimental halls. The PQM processes raw data files from the Daya Bay data acquisition system, generates and publishes histograms via a graphical web interface by executing the userdefined algorithm modules, and saves the histograms for permanent storage. The fact that the whole process takes only around 40 minutes makes it valuable for the shift crew to monitor the running status of all the sub-detectors and the data quality.展开更多
基金The National Key R&D Program of China under contract No.2021YFC3200501the National Natural Science Foundation of China under contract Nos 42107055 and 42130703the Fund of Shenzhen Science and Technology Innovation Committee under contract No.20200925174525002.
文摘Subterranean estuaries(STE)are important seawater-groundwater mixing zones with complex biogeochemical processes,which play a vital role in the migration and transformation of dissolved materials.In this study,we first investigated the spatial distributions of dissolved inorganic nitrogen(DIN),dissolved inorganic phosphorous(DIP),dissolved inorganic silicon(DSi)and metal elements(As,Ba,Cr,Cu,Fe,Mn,Ni,Pb,and Zn)in STE including upper intertidal,seepage face and subtidal zones.We then estimated submarine groundwater discharge(SGD)and associated nutrient and metal element fluxes.From the generalized Darcy’s law method,SGD was estimated to be 30.13 cm/d,which was about 7 times larger than the inflow(4.16 cm/d).The nutrient and metal fluxes from SGD were estimated to be(5.33±4.99)mmol/(m^(2)·d)for DIN,(0.22±0.03)mmol/(m^(2)·d)for DIP,(16.20±2.05)mmol/(m^(2)·d)for DSi,(1325.06±99.10)μmol/(m^(2)·d)for Fe,(143.41±25.13)μmol/(m^(2)·d)for Mn,(304.06±81.07)μmol/(m^(2)·d)for Zn,(140.21±13.33)μmol/(m^(2)·d)for Cu,(84.49±2.94)μmol/(m^(2)·d)for Pb,(37.38±5.51)μmol/(m^(2)·d)for Ba,(27.88±3.89)μmol/(m^(2)·d)for Cr,(10.10±6.33)μmol/(m^(2)·d)for Ni,and(6.25±3.45)μmol/(m^(2)·d)for As.The nutrient and metal fluxes from SGD were relatively higher than those from the inflow,suggesting that nearshore groundwater acted as the sources of nutrients and metal elements discharging into the sea.The environmental potential pollution of coastal seawater was evaluated by pollution factor index(Pi),comprehensive water quality index(CWQI),and ecological risk index(ERI).Pb mainly caused potential danger of nearshore environment with considerable contamination(Pi=5.78±0.19),heavy pollution(CWQI=4.09)and high ecological risk(ERI=18.00).This study contributed to better understanding the behavior of nutrients and metal elements and improving the sustainable management of STE under the pressure of anthropogenic activities and climate change.
基金The Project of Key Laboratory of Marine Environmental Survey Technology and Application,Ministry of Natural Resources under contract No.MESTA-2021-D006the China Ocean Development Foundation under contract No.CODF-002-ZX-2021+5 种基金the Science and Technology Plan Projects of Guangdong Province under contract No.2021B1212050025the Director’s Foundation of South China Sea Bureau of Ministry of Natural Resources under contract No.230201the Research Fund Program of Guangdong Provincial Key Laboratory of Applied Marine Biology under contract No.LAMB20221007the Natural Science Foundation of Guangdong Province of China under contract No.2017A030310592the Key Program of Bureau Director of State Oceanic Administration under contract No.180104the Open Project of State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences under contract No.LTO1709.
文摘Submarine groundwater discharge(SGD),which can be traced using naturally occurring radium isotopes,has been recognized as a significant nutrient source and land-ocean interaction passage for the coastal waters of the Daya Bay,China.However,uncertainties in assessing SGD fluxes must still be discussed in detail.In this study,we attempted to utilize the Monte Carlo method to evaluate the uncertainties of radium-derived SGD flux in the northeast and entirety of the Daya Bay.The results show that the uncertainties of the SGD estimate in the northeast bay are very sensitive to variations in excess radium inventories as well as radium inputs from bottom sediments,while the uncertainties of the SGD estimate for the entire bay are strongly affected by fluctuations in radium inputs from bottom sediments and radium end-members of SGD.This study will help to distinguish the key factors controlling the accuracy of SGD estimates in similar coastal waters.
基金This work was supported by the National Natural Sci-ence Foundation of China(Nos.31971432,41976112)the Key Special Project for Introduced Talents Team of Southern Marine Science and Engineering Guangdong Laboratory(Guangzhou)(Nos.GML2019ZD0401,GML 2019ZD0405)+1 种基金the Science and Technology Basic Re-sources Investigation Program of China(No.2017FY201404)the Science and Technology Planning Project of Guangdong Province,China(No.2020B1212060058).
文摘The response of zooplankton to the ecological environment in Daya Bay is unclear under the influence of both climate changes and anthropogenic activities on a seasonal to inter-annual scale.Based on monthly surveys and historical data,we found the zooplankton community had changed temporally and spatially.A total of 134 species was recorded during the study,and copepods dominated numerically in terms of diversity and abundance.Both copepods and cladocerans were the main contributors to zooplankton abundance.The community structure of zooplankton was temporally classified into the warm and cold groups,and spatially into the three groups located in the marine cage-culture area(MCCA),the outflow of nuclear power plants(ONPP)and unpolluted waters(UPW).The zooplankton was characterized by low biomass(dry weight),high diversity and abundance in the warm period in contrast to that in the cold period.Compared with the other two groups,the MCCA group of zooplankton showed high abundance,low diversity and biomass.Variations in dominant species were closely related to temperature,salinity and chlorophyll a concentration.Species diversity and dry weight decreased in comparison with 30 years ago,while zooplankton abundance increased.The seasonal variation in zooplankton was affected mainly by temperature that was controlled by monsoon,while the spatial difference in the community structure was probably due to eutrophication in the MCCA and thermal water discharge from ONPP.The zooplankton community is undergoing great changes with the tendency of miniaturization and gelatinization in recent 30 years in Daya Bay.
文摘The increase of water temperature, due to thermal discharges from two nuclear power stations, was one of the most significant environmental changes since 1982 in the Daya Bay, located in the north of the South China Sea. This study investigates the long-term (1982-2012) environmental changes in Daya Bay in response to the increase of water temperature, via comprehensively interpreting and analyzing both satellite and in situ observations along with previous data. The results show that: 1) salinity, dissolved oxygen (DO), chemical oxygen demand (COD) and nutrients had been enhanced after the thermal discharges started in 1994;2) the concentration of Chl-a increased while the net-phytoplankton abundance decreased;3) diversity of the phytoplankton community had decreased;4) fishery production had declined;and 5) frequency of Harmful Algal Bloom occurrence had increased. Satellite images show clearly that a thermal plume from the power stations extended toward the interior of Daya Bay, and that surface temperature of the seawater increased as one approached the power stations. The analysis suggests that the thermal water discharged from the two power stations was a driver of the ecosystem’s change in Daya Bay. Several factors, including nutrients, salinity, DO, and COD, varied according to the increase of water temperature. These factors affected the water quality, Chl-a, and phytoplankton in the short term and impaired aquatic organisms and the whole ecosystem in the long term.
基金Supported by the National Natural Science Foundation of China (40972198)the National Key Basic Research and Development Program of China(2010CB732001)
文摘Weathered troughs are frequently encountered in granites. They can cause problems to tunneling in the rocks and have to be properly addressed. The structures or spatial shapes of weathered troughs were seldom clarified in the past. In this paper, four weathered troughs are identified by means of geophysical exploration, core drilling, logging, and in-situ stress measurement at Daya Bay reactor-neutrino experiment site in Shenzhen, China. The weathered troughs are exposed on the ground or partially covered by grass and soils, which will threaten the safety of horizontal tunneling at a shallow depth. High electrical resistivity (HER) method is adopted for its feasibility and practicality, in combination with field geological observation, ultrasonic televiewer in boreholes and in-situ stress measurement. By comparing the HER values of completely decomposed to fresh rocks, it is indicated that the HER values of weathered troughs in natural state are 0.4-100 D.m, and the in-situ stress is abnormally lower than those at upper and lower layers. Field investigations show that the depths of the four weathered troughs are 30-182 m, with bottom elevation over 10 m. The volume of each weathered trough is mostly over lx l 0^6 m3 in inverted conic form. The weathered troughs often occur in various kinds of landforms, such as ridges, gullies or gently dipping dish-like depression areas. Faults and boundaries of different granitic plutons as well as joints govern the formation, locations and strikes of these troughs under development.
基金The National Natural Science Foundation of China under contract No.41506136the Scientific Research Foundation of Third Institute of Oceanography,SOA under contract No.2015005
文摘In this study, the horizontal and vertical distribution of primary production(PP) and its monthly variations were described based on field data collected from the Daya Bay in January–December of 2016. The relationships between PP and environmental factors were analyzed using a general additive model(GAM). Significant seasonal differences were observed in the horizontal distribution of PP, while vertical distribution showed a relatively consistent unimodal pattern. The monthly average PP(calculated by carbon) ranged from 48.03 to 390.56 mg/(m~2·h),with an annual average of 182.77 mg/(m~2·h). The highest PP was observed in May and the lowest in November.Additionally, the overall trend in PP was spring>summer>winter>autumn, and spring PP was approximately three times that of autumn PP. GAM analysis revealed that temperature, bottom salinity, phytoplankton, and photosynthetically active radiation(PAR) had no significant relationships with PP, while longitude, depth, surface salinity, chlorophyll a(Chl a) and transparency were significantly correlated with PP. Overall, the results presented herein indicate that monsoonal changes and terrestrial and offshore water systems have crucial effects on environmental factors that are associated with PP changes.
基金Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Nos.XDA13020102,XDA13020104)the National Key Research and Development Project of China(Nos.2016YFC0502800,2017YFC0506302)+1 种基金the National Natural Science Foundation of China(No.41806188)the Science and Technology Planning Project of Guangdong Province,China(Nos.2015A020216013,2017B0303014052)。
文摘Harmful algal blooms(HABs),such as dinoflagellate blooms,have adverse eff ects on coastal water environments,causing seafood contamination and aquaculture economic losses.Based on historical HAB records data(1983-2017)and phytoplankton data(1982-2008),field investigation and laboratory experiments on frequently bloomed dinoflagellate species,we analyzed the possible mechanisms of high frequency dinoflagellate blooms in Daya Bay,South China Sea.The HAB records data show that the proportion of dinoflagellate blooms increased from 15% before 1994 to 77.27% after 2011.The bloom occurred mostly in summer(57.58%)in Yaling Bay(76.92%).The species inducing dinoflagellate blooms tended to be singular over time,with high proportion of Scrippsiella trochoidea(42.86%-88.88%).Laboratory experiment and field investigation of S.trochoidea bloom showed that this species grew rapidly at 30℃ and 32.1℃(r=0.47,P<0.05),respectively.Results indicate that temperature rise in Yaling Bay was aff ected by nearby nuclear plant effluent,which favored the S.trochoidea bloom.Coincidently,nearly 70% of S.trochoidea blooms occurred in about 7 days after local spring tide and strong wind(wind velocity>7 m/s),which disturbed the resting cysts in the sediment and bring them into surface layer.Taking into account of environmental parameters,algae source,and atmospheric conditions,the probable mechanism of S.trochoidea bloom could be explained.The cysts were resuspended by the spring tide or strong wind,germinated at the bottom layer,reproduced rapidly at higher temperature,and then aggregated in the inner bay(Yaling Bay),resulting the frequent S.trochoidea bloom.Considering the influences of global warming and human activities,it should be taken more attention that dinoflagellate blooms might increase along the coastal waters.
文摘The purpose of this study is to detail the ecological characteristics of phytoplankton in waters around the Daya Bay Nuclear Power Station in Guangdong (GNPS) (Fig. 1) in spring, the bloom period of algae. The collections with a small temporal scale of every three days were made during 30 cruises from March to May in 1987. Such an investigation has never been carried out before in China except that the seasonal distribution and composition of phytoplankton in these regions were reported in
基金Supported by Natural Science Foundation of Guangdong Province(2018A030313120)Basal Research Fund of Central Public-interest Scientific Institutions in Chinese Academy of Aquatic Sciences(2018HY-ZD0104)+1 种基金State Key Laboratory of Tropical Oceanography,South China Sea Institute of Oceanology,Chinese Academy of Sciences(LTO1806)National Key Technology R&D Program(2012BAD18B01)
文摘[Objective] The paper was to quantitatively evaluate the maintenance effect of summer fishing moratorium (SFM) in Daya Bay. [Method]Based on satellite remote sensing and trawl surveys, the changes in sea surface temperature (SST) , chlorophyll a (Chla) concentration, catchper unit effort (CPUE), biodiversity, species composition, body length and weight of total catch in Daya Bay before SFM (May 2015) and after SFM(August 2015) were comparatively analyzed. [Result] The CPUE of total catch mainly distributed from 0-10 kg/h before SFM to 0-40 kg/h afterSFM. The average body length and weight of catches increased, indicating that the growth rate of catches was accelerated. The indices of ShannonWiener diversity index (H忆) and Pielou evenness index(J忆) increased by 0.36 and 0.14, respectively, indicating that the community structure wasimproved. The biomass spectra of fishery resources community suggested that the slopes of normalized biomass spectra after SFM was greater than-1, and the biomass of fishery resources increased with the increase of individual body weight after SFM. SFM reduced offshore fishing intensity,recovered and conserved the fishery resources in Daya Bay. [Conclusion] In order to improve the SFM system and promote the sustainable development of coastal fishery resources, it is suggested to prolong the time of SFM appropriately, reduce the number of coastal fishing boats, and strengthen the conservation of fish resources.
文摘The marine environment, productivity and potential biotic resources in the waters of the Daya Bay were investigated by South China Sea Institute of Oceanology, Academia Sinica from 1984 to 1986. The present paper deals mainly with the annual variation and distribution characteristics in chlorophyll a and with some of the ecological factors involved in chlorophyll distribution within the bay. Correlation models are established and discussed. The results could be helpful for further probing into ecosystem and for the exploitation-utilization of aquatic resources in this region.
文摘The surface sediment samples were collected month by month at nine stations in the Daya Bay from January to December 1987, and the number of anaerobic sulfite reducing bacteria and their spores and the regularity of seasonal change were determined. The effect of environmental factors, water temperature and the resoluble oxygen concentration in the bottom of seawater on the number of them were discussed. The results show that the number of anaerobic su|fite reducing bacteria were low in sediment of the Daya Bay, indicating that the hay was less contaminated.
文摘The Daya Bay Nuclear Power Plant in South China’s Guangdong Province began its second refueling and maintenance work for its Unit 1 on March 31, 1996. Apart from the regular work required by the plant’s annual check- up plan, all of the present guide tubes of the control rods in Unit I will be replaced by the type of state-of-the-art tubes used in Unit 2, to make the dropping-time of the tubes more accurate. The annual check may take 80 days, thus the unit will probably re-connect with the power grid in mid June. As for Unit 2, the "exciter" of generator malfunctioned during the start of the reactor on March 6, when the second refueling and maintenance neared completion.
基金supported by the Medical Scientific Research Foundation of Guangdong province(B2020012,C2019062,C2023023,C2023022,C2021023,and B2023283),China.
文摘Objective:To investigate the radioactivity levels of seawater,sediments,and biota in the Daya Bay sea area,China,in order to establish the radioactivity baseline values,and provide basic data for the assessment of potential radiological risks that might result from the application of nuclear technology or human activities.Methods:Samples of seawater,sediments,and biota were collected from the Daya Bay sea area and analyzed.Their radioactivity baseline data were then compared with information from other regions in China and around the world reported in related literature.Results:For the seawater samples,the activity concentrations of natural radionuclide ^(40)K were 9.9-10.4 Bq/L,while ^(238)U,226Ra,^(210)Pb,^(137)Cs,and ^(110)Ag^(m) were below the minimum detectable activity(MDA).Regarding the sediment samples,the activity concentrations of ^(238)U,^(228)Ra,^(226)Ra,^(210)Pb,^(40)K,and ^(137)Cs were 38.1-40.4,49.1-53.7,32.6-38.6,59-95,590-650,and 0.48-0.88 Bq/(kg dry weight),respectively,while ^(110)Agm was below the MDA.For the marine shrimps in the biota samples,the activity concentrations of ^(228)Ra,^(226)Ra,^(40)K,and ^(137)Cs were 1.14-2.75,0.17-0.43,63-76,and 0.038-0.045 Bq/(kg wet weight),respectively,while ^(238)U,^(210)Pb,and ^(110)Agm were all below the MDA.Furthermore,for the marine fishes in the biota samples,the activity concentrations of ^(228)Ra,^(226)Ra,^(210)Pb,^(40)K,and ^(137)Cs were 2.1-19.7,0.32-3.78,<2.2-2.8,59-70,and<0.007-0.026 Bq/(kg wet weight),respectively,while ^(238)U and ^(110)Ag^(m) were all below the MDA.^(228)Ra was found to be concentrated in Osteomugil ophuyseni with 19.7 Bq/(kg wet weight).Conclusions:The radioactivity levels of seawater and marine sediments in the Daya Bay sea area are within the range of the normal background values.Osteomugil ophuyseni exhibited higher concentrations of ^(228)Ra than other species in this study,while the other species in the biota show no significant difference in the radioactivity levels from data in relevant literature.
基金Supported by the Ministry of Science and Technology of Chinathe United States Department of Energy+15 种基金the Chinese Academy of Sciencesthe National Natural Science Foundation of Chinathe Guangdong provincial governmentthe Shenzhen municipal governmentthe China Guangdong Nuclear Power GroupShanghai Laboratory for Particle Physics and Cosmologythe Research Grants Council of the Hong Kong Special Administrative Region of ChinaUniversity Development Fund of The University of Hong Kongthe MOE program for Research of Excellence at NTU, NCTUNSC fund support from Taipeithe U.S. National Science Foundationthe Alfred P. Sloan Foundationthe Ministry of EducationYouth and Sports of the Czech Republicthe Czech Science Foundationthe Joint Institute of Nuclear Research in Dubna,Russia
文摘We report an improved measurement of the neutrino mixing angle θ13 from the Daya Bay Reactor Neutrino Experiment. We exclude a zero value for sin22θ13 with a significance of 7.7 standard deviations. Electron antineutrinos from six reactors of 2.9 GWm th were detected in six antineutrino detectors deployed in two near (flux-weighted baselines of 470 m and 576 m) and one far (1648 m) underground experimental halls. Using 139 days of data, 28909 (205308) electron antineutrino candidates were detected at the far hall (near halls). The ratio of the observed to the expected number of antineutrinos assuming no oscillations at the far hall is 0.944± 0.007(stat.) ± 0.003(syst.). An analysis of the relative rates in six detectors finds sin22θ13=0.089± 0.010(stat.)±0.005(syst.) in a three-neutrino framework.
基金Supported by Chinese Academy of Sciences,National Natural Science Foundation of China(Project 10225524,10475086,10535050 and 10575056)Ministry of Science and Technology of China
文摘Detailed measurements of Hamamatsu R5912 photomultiplier signals are presented, including the single photoelectron charge response, waveform shape, nonlinearity, saturation, overshoot, oscillation, prepulsing, and afterpulsing. The results were used to build a detailed model of the PMT signal characteristics over a wide range of light intensities. Including the PMT model in simulated Daya Bay particle interactions shows no significant systematic effects that are detrimental to the experimental sensitivity.
基金Supported in part by the Ministry of Science and Technology of Chinathe United States Department of Energy,the Chinese Academy of Sciences+11 种基金the CAS Center for Excellence in Particle Physicsthe National Natural Science Foundation of Chinathe Guangdong provincial governmentthe Shenzhen municipal governmentthe China General Nuclear Power Groupthe Research Grants Council of the Hong Kong Special Administrative Region of Chinathe MOST and MOE in Taiwanthe U.S.National Science Foundationthe Ministry of Education,Youth and Sports of the Czech Republicthe Joint Institute of Nuclear Research in Dubna,Russiathe NSFC-RFBR joint research programthe National Commission for Scientific and Technological Research of Chile
文摘A new measurement of the reactor antineutrino flux and energy spectrum by the Daya Bay reactor neutrino experiment is reported. The antineutrinos were generated by six 2.9 GWth nuclear reactors and detected by eight antineutrino detectors deployed in two near(560 m and 600 m flux-weighted baselines) and one far(1640 m flux-weighted baseline) underground experimental halls. With 621 days of data, more than 1.2 million inverse beta decay(IBD) candidates were detected. The IBD yield in the eight detectors was measured, and the ratio of measured to predicted flux was found to be 0.946±0.020(0.992±0.021) for the Huber+Mueller(ILL+Vogel) model. A 2.9σ deviation was found in the measured IBD positron energy spectrum compared to the predictions. In particular, an excess of events in the region of 4–6 MeV was found in the measured spectrum, with a local significance of 4.4σ. A reactor antineutrino spectrum weighted by the IBD cross section is extracted for model-independent predictions.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.91958203,41776027,and 41606009)the Xiamen University Fundamental Research Funds for the Central Universities(Nos.20720180103,20720180099)+1 种基金the Laboratory for Regional Oceanography and Numerical Modeling,Pilot National Laboratory for Marine Science and Technology(Qingdao)(No.2017A02)the municipal project of Huizhou City(No.F2017-01-1)
文摘GPS-based surface drifters were used to investigate the surface currents in Daya Bay and along the eastern Guangdong coast in China.Surface current vectors were measured based on the GPS location and corresponding time information sent by drifters through the mobile phone network.The analysis of data from 120 drifters,deployed in late spring 2018 in the case-study region,shows that the drifters are generally capable of capturing the surface(tidal and residual)currents.The drifter trajectories suggest an anticlockwise surface current inside Daya Bay and a north-eastward current along the eastern Guangdong coast,where the coastal current along the eastern Guangdong coast is faster than that inside Daya Bay.The surface currents in the investigated region follow an irregular semidiurnal cycle due to the influence of the tidal current,while the currents inside Daya Bay are strongly affected by the topography.According to the harmonic analysis,an irregular semidiurnal type of tidal current is evident at a study grid inside Daya Bay,with an Eulerian residual current speed of 9.0 cm/s and a direction of 276°.The Lagrangian residual current outside Daya Bay moves north-eastward with a mean speed of 22 cm/s along the eastern Guangdong coast,while the current inside Daya Bay moves northward to the bay head with a mean speed of about 8.0 cm/s,which agrees well with the one reported in other literatures.
基金Acknowledgements This research was supported by the National Natural Science Foundation of China (Gram No. 51139003). We thank the China Institute for Radiation Protection and China Institute of Water Resources and Hydropower Research for their valuable input.
文摘The impact on the environment ofradionuclide release from nuclear power plants has attracted increased attention, especially after the accident at Fukushima Daiichi Nuclear Power Plant in Japan. Based on the mechanisms of adsorption/desorption at solid/liquid interfaces and a surface micromorphology model of sediments, a theoretical expression of the distribution coefficient Kd is derived. This coefficient has significant effects on the distribution of radionuclide in seawater, suspended sediment and seabed sediment. Kd is then used to simulate ^90Sr transport in the sea near the Daya Bay Nuclear Power Plant. The simulation results are compared with field measurements of tidal level, current velocity, suspended sediment concentration and ^90Sr concentrations in the same period. Overall, the simulated results agree well with the field measured data. Thus, the derived expression for Ka is capable of interpreting realistic adsorption/desorption processes. What's more, conclusion is drawn that about 40% ^90Sr released by Daya Bay Nuclear Power Plant will be adsorbed by suspended sediment and 20% by seabed sediment, only about 40% ^90St will remain in the sea near Daya Bay Nuclear Power Plant in South China Sea.
基金Supported by NSFC(11105168)973 Program(2013CB834303)
文摘The Daya Bay Reactor Neutrino Experiment started running on September 23, 2011. The offiine computing environment, consisting of 11 servers at Daya Bay, was built to process onsite data. With the current computing ability, onsite data processing is running smoothly. The Performance Quality Monitoring system (PQM) has been developed to monitor the detector performance and data quality. Its main feature is the ability to efficiently process multiple data streams from the three experimental halls. The PQM processes raw data files from the Daya Bay data acquisition system, generates and publishes histograms via a graphical web interface by executing the userdefined algorithm modules, and saves the histograms for permanent storage. The fact that the whole process takes only around 40 minutes makes it valuable for the shift crew to monitor the running status of all the sub-detectors and the data quality.