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1.
Algal blooms in Tolo Harbour, Hong Kong have received much attention and submarine groundwater discharge is speculated to be a significant pathway carrying nutrients into the constricted estuary. Plover Cove, a small cove in the Harbour, was selected for SGD analysis using 222Rn budget. The volumetric SGD rates are estimated to be about 8000 m3/day for neap tide and about 17,000 m3/day for spring tide. Result of nutrient analysis of the porewater indicates that the nutrient loading through this pathway is speculated to be crucial for eutrophication in Tolo Harbour. Current practice for the management of algal blooms in Hong Kong, in which nutrient loading through SGD was ignored, has to be reviewed and the control measures of groundwater contamination are obviously required.  相似文献   

2.
To investigate the impacts of nutrient concentrations and N:P:Si ratios on the ecosystem of the Huanghai Sea (Yellow Sea), the current status and long-term variation of nutrients concentrations and ratios as well as phytoplankton community structure in the Huanghai Sea were collected and analyzed. The results reveal great annual and seasonal fluctuations in the nutrient concentrations and N:P:Si ratios during 1998-2008 with no clear pattern observed in the whole region. Yet on a seasonal scale of spring and in the coastal regions such as the Jiaozhou Bay and Sanggou Bay, the increase of DIN concentration and N:P ratio as well as the decrease of phosphate and silicate concentrations and Si:N ratios were relatively significant. Many pelagic ecosystem changes have occurred concurrent with these changes of the nutrient regime, such as the recent increase of primary production, changes of phytoplankton chlorophyll a biomass and abundance, an increase of eutrophication, and occurrence of HABs. In addition, new trends in the variation of nutrients seem to be developing in some particular transect such as 36°N, which suggests that long-term and systematic ecosystem monitoring in the Huanghai Sea is necessary.  相似文献   

3.
Eight stations were chosen for this 14 month survey of Tolo Harbour in Hong Kong, four of them in the harbour proper and four in the estuaries of the major streams entering the harbour. Various chemical and physical factors were measured twice each month. Water samples were collected for nutrient, phytoplankton, chlorophyll and bacteriological analysis.The annual discharge of nutrients from the four streams into Tolo Harbour has been estimated, based on the nutrient analyses and computation of annual discharge (QA) values for these streams. The seasonal and spatial variations in nutrient content are discussed in relation to the increasing organic pollution of Tolo Harbour. Calculations of various ratios between SiO3, PO4, NO3 and total inorganic N reveal that excessive amounts of phosphate are entering the harbour and subsequently accumulating in the bottom waters and sediments, leading to changes in the trophic condition of this water body and the development of anoxic conditions in the bottom layer.Significant correlation has been demonstrated between standing crop and various environmental parameters in both estuarine and marine waters and similarly between chlorophyll a concentration and various environmental parameters. However, no significant correlation values were obtained between either standing crop or chlorophyll a concentrations, SiO3Si (the latter presumably due to the predominance of diatoms in the phytoplankton). Neither standing crop nor chlorophyll determinations reveal any evidence of alternating periods of high productivity and decomposition which could explain the deteriorating bottom water conditions. This again is taken as evidence that the high organic inputs are responsible for such deterioration.Increasing TC, FC and FS densities have been noted in Tolo Harbour as a direct result of the increasing organic pollution and ratios between FC and FS densities indicate that in 55% of the samples pollution was derived from human sewage. The bacterial levels well exceeded various international standards for bathing waters and shellfish collection for at least a part of the survey period and at a number of stations for the entire survey period. Pathogenic organisms were also present. This underlines the potential health risks in these waters.Finally, the future prospects for this harbour are discussed in relation to activities such as reclamation and the development of new towns and their impact on water quality.  相似文献   

4.
The Mondego estuary, a shallow warm-temperate intertidal system located on the west coast of Portugal, has for some decades been under severe ecological stress, mainly caused by eutrophication. Water circulation in this system was, until 1998, mainly dependent on tides and on the freshwater input of a small tributary artificially controlled by a sluice. After 1998, the sluice opening was effectively minimised to reduce the nutrient loading, and the system hydrodynamics improved due to engineering work in the upstream areas. The objective of the present study was to evaluate the effect of the mitigation measures implemented in 1998. Changes to the hydrodynamics of the system were assessed using precipitation and salinity data in relation to the concentrations of dissolved inorganic nutrients, as well as the linkage between dissolved N:P ratios and the biological parameters (phytoplankton chlorophyll a concentrations, green macroalgal biomass and seagrass biomass). Two distinctive periods were compared, over a ten year period: from January 1993 to January 1997 and from January 1999 until January 2003. The effective reduction in the dissolved N:P atomic ratio from 37.7 to 13.2 after 1998 is a result of lowered ammonia, but not the oxidised forms of nitrogen (nitrate plus nitrite), or increased concentrations of dissolved inorganic phosphorus. Results suggest that the phytoplankton is not nutrient limited, yet maximum and mean biomass of green macroalgae was reduced by one order of magnitude after the mitigation measures. This suggests that besides lowering the water residence time of the system, macroalgal growth became nitrogen limited. In parallel to these changes the seagrass-covered area and biomass of Zostera noltii showed signs of recovery.  相似文献   

5.
Hong Kong waters receive high nutrient loading from year-round sewage effluent and Pearl River discharge during the summer wet season. We assessed the role of physical processes in reducing eutrophication by calculating a eutrophication reduction index for four different hydrographical areas and four seasons. We used outdoor incubation experiments to assess the response of phytoplankton when physical (mixing and dilution) processes and mesozooplankton grazing were reduced. The primary regulator of phytoplankton growth in low nutrient eastern waters (reference site) shifted from nutrients in the wet season to increased vertical mixing in the dry season. In the highly flushed western waters and Victoria Harbour, the majority (>86?%) of the eutrophication impacts were reduced by strong hydrodynamic mixing (turbulence, vertical mixing, and flushing effects) all year. In southern waters, eutrophication effects were severe (chlorophyll a of up to ~73?μg?L?1) and was regulated by the ambient phosphate (PO4) concentration (~0.1?μM) during summer. In contrast, 62–96?% of the potential eutrophication impacts were reduced by physical processes during other seasons. Bioassays also revealed that the yield of chlorophyll from dissolved inorganic nitrogen (DIN) that was taken up by phytoplankton [1.1–3.3?g?Chl (mol?N)?1] was not significantly different in both N- and P-limited cases. In contrast, the uptake ratios of DIN:PO4 (26:1–105:1) and Chl:P ratios [42–150?g?Chl (mol?P)?1] in the P-limited cases were significantly (p?<?0.05, t test) higher than the N-limited cases [~16DIN:1P and 22–48?g?Chl (mol?P)?1]. The C:Chl ratios ranged from 32 to 87?g?g?1. These potential ranges in ratios need to be considered in future nutrient models.  相似文献   

6.
The concentration and composition of nutrients, such as N, P, and Si, respond to biogeochemical processes and in turn, impact the phytoplanktons’ community structure and primary production. In this study, historical data was systematically analyzed to identify long-term variations in nutrient trends, red tide frequency, phytoplankton community abundance, and dominant species succession in the southern Yellow Sea(SYS). Results showed that N/P concentration ratios dramatically increased as a funct...  相似文献   

7.
渤黄海营养盐结构及其潜在限制作用的时空分布   总被引:7,自引:0,他引:7  
根据2006-2007年4个季节的现场调查资料,分析探讨了渤海和黄海营养盐结构分布变化特征及其对浮游植物生长的潜在的限制状况.结果表明,渤黄海水体 Si/N/P 比值均偏离 Redfield 比值,季节变化明显;春夏冬季 N/P和 Si/P比值由近岸向远岸海域递减,高值区主要分布在黄河口、鸭绿江口及苏北近岸,秋季上层水体N/P和Si/P比值的分布趋势有所不同,高值区主要分布在南黄海的中部海域.受陆源输入的影响,近岸特别是河口区 N/P和 Si/P比值均较高,温跃层的生消变化和生物活动调控着黄海中部海域营养盐结构的变化.渤黄海浮游植物生长主要受P的潜在限制,部分季节受N、Si的潜在限制;营养盐限制状况存在着明显的时空变化及不同营养盐的同时或交替限制的现象.  相似文献   

8.
Dilution experiments were conducted to investigate microzooplankton grazing impact on phytoplankton of different taxonomic groups and size fractions (< 5, 5–20, 20–200 μm) during spring and summer bloom periods at two different sites (inner Tolo Harbour and Tolo Channel) in the Tolo Harbour area, the northeastern coastal area of Hong Kong. Experiments combined with HPLC pigment analysis in three phytoplankton size fractions measured pigment and size specific phytoplankton growth rates and microzooplankton grazing rates. Pigment-specific phytoplankton growth rates ranged between 0.08 and 3.53 d 1, while specific grazing rates of microzooplankton ranged between 0.07 and 2.82 d 1. Highest specific rates of phytoplankton growth and microzooplankton grazing were both measured in fucoxanthin in 5–20 μm size fraction in inner Tolo Harbour in summer, which coincided with the occurrence of diatom bloom. Results showed significant correlations between phytoplankton growth and microzooplankton grazing rates. Microzooplankton placed high grazing pressure on phytoplankton community. High microzooplankton grazing impact on alloxanthin (2.63–5.13) suggested strong selection toward cryptophytes. Our results provided no evidence for size selective grazing on phytoplankton by microzooplankton.  相似文献   

9.
Tropical estuaries are under increasing pressure worldwide from human impacts, but are poorly studied compared with temperate systems. This study examined a tropical macrotidal estuary, Darwin Harbour, in northern Australia, using a combination of direct measurements and literature values to determine the main sources of primary production and the sources of nutrients supporting growth. The main source of primary production was calculated to be the extensive area of fringing mangroves and resulted in a net autotrophic system (PG:R = 2.1). Much of the carbon in the mangrove forests appears to be retained within the forests or respired, as the water column was also net autotrophic despite the carbon inputs. Phytoplankton were the second largest primary producer on a whole-of-harbour basis, with low biomass constrained by light and nutrient availability. The phytoplankton were likely to be nitrogen (N) limited, based on low N:phosphorus (P) ratios, low dissolved bioavailable N concentrations (ammonium (NH4+), nitrate (NO3), urea), and evidence that phytoplankton growth in bioassays was stimulated by NH4+ addition. The largest new source of N to the system was from the ocean due to higher N concentrations in the incoming tides than the outgoing tides. Atmospheric inputs via N fixation on the intertidal mudflats and subtidal sediments were substantially lower. The rivers feeding into the harbour and sewage were minor N inputs. Nitrogen demand by primary producers was high relative to available N inputs, suggesting that N recycling within the water column and mangrove forests must be important processes. Darwin Harbour is adjacent to the rapidly growing urban area of Darwin city, but overall there is no evidence of anthropogenic nutrient inputs having substantial effects on primary production in Darwin Harbour.  相似文献   

10.
The seasonal dynamics of nutrient ratios and abundance of phytoplankton cells from the central (CB) and western (WB) Bay of Bengal (BOB) were studied during the fall intermonsoon (FIM; September-October 2002) and spring intermonsoon (SpIM; April-May 2003). The nutrient molar ratios of macronutrients such as nitrate to phosphate (N:P), nitrate to silicate (N:Si) and silicate to phosphate (Si:P) in the top 120m were calculated for both FIM and SpIM. During both the seasons, the N:P ratios along the CB and WB were lower than 16, indicating nitrate deficiency. Whereas, along both transects the N:Si ratio was <1 and Si:P >3 in the top 20 and 40m during FIM and SpIM, respectively, indicating Si enrichment. Relatively greater nutrient concentrations along the WB than the CB appear to contribute to higher phytoplankton abundance. The preponderance of diatoms in the Bay could be attributed to rapid utilization of available nutrients in particular during FIM thus resulting in low N:Si ratios in the water column. Among diatoms, pennales were predominantly controlled by nutrients and their ratios. While, apart from nutrients, physical stratification, light and eddies also seem to influence the distribution and abundance of centrales.  相似文献   

11.
Total organic carbon and organic carbon stable isotope, biogenic silica, chlorin were measured from a high resolution sediment core to indicate the variation in paleoproductivity and the environmental implications over the past decades (1942 to 1997) in the Changjiang Estuary. Based on these biomarkers, the shift in the phytoplankton community structure in the past decades was discussed in response to the long-term variations in nutrient concentrations and nutrient ratios. The results showed that the δ 13 C values varied from –26.15‰ to –19.5‰, suggesting the combined organic carbon sources of riverine and marine organisms. Based on the biogenic proxies, paleoproductivity changes were categorized into three stages: low production before 1950; an increase in production with the dominance of diatoms during 1950 to 1980, consistent with increasing of nutrient concentrations; a decrease in production after 1980 when the diatom production decreased while the production of non-silicious phytoplankton increased due to high nutrient inputs, and high N/P and P/Si ratios in the Changjiang Estuary. The sedimentation records also indicated that the riverine organic carbon increased since 1980.  相似文献   

12.
依据改革开放40 a来胶州湾营养盐状况历史资料以及2018—2019年的现场调查,对胶州湾营养盐历史变化过程及其生态效应进行了系统分析。结果表明:营养盐的浓度变化大致以2008年为分界节点,在2008年前胶州湾溶解无机氮(DIN)浓度呈现持续上升趋势,而溶解无机磷(DIP)、活性硅酸盐(DSi)浓度则先略有减少后快速增加;2008年后胶州湾3种营养盐浓度均快速减少。营养盐限制状况由20世纪80年代初期的氮限制、20世纪90年代的硅限制转变为目前的磷限制。胶州湾Chl a年均质量浓度一直在3μg·L^-1上下波动但近年来则呈下降趋势,浮游动物生物量1994年后大幅度增加。分析发现,入湾营养盐通量的增加和海域面积缩小是2008年前胶州湾营养盐浓度增加的主要原因,而近十几年来胶州湾环境综合整治措施的大力实施则是氮、磷营养盐浓度减少的主要原因。2010年以前贝类养殖是控制胶州湾浮游植物生物量的主要因素,但近年来溶解无机磷浓度的减少和浮游动物生物量的增加是Chl a质量浓度呈下降趋势的主要原因。  相似文献   

13.
Biologically important nutrient concentrations in Dokai Bay have declined as a result of reductions in anthropogenic inputs of total nitrogen and total phosphorus. A decrease in nutrient concentrations affects phytoplankton growth, thereby changing the biochemical characteristics of autochthonous particulate matter. We therefore investigated changes in the C/N/P molar ratio of suspended particulate matter (SPM) in the summer, when phytoplankton growth is vigorous, before environmental quality standards (EQSs) were attained (1995–1998) and afterward (2006–2009). We found that the ratio of particulate organic nitrogen (PON) to particulate phosphorus (PP) changed in conjunction with changes in the ratio of dissolved inorganic nitrogen to dissolved inorganic phosphorus (DIP) that resulted from reductions in nutrient loading. Furthermore, we suggest that because the DIP concentration in seawater was high before EQSs were attained, inorganic phosphorus was possibly adsorbed onto SPM. After the attainment of EQSs, however, the DIP concentration fell, and PON/PP was high. Phosphorus limitation of phytoplankton growth in the mouth of the bay may explain the high PON/PP ratios after EQS attainment.  相似文献   

14.
Historic changes in flux of matter and nutrient budgets in the Bohai Sea   总被引:1,自引:0,他引:1  
Over the past four periods ( 1959--1960, 1982--1983, 1992--1993, and 1998--1999), the ecosystem of the Bohai Sea changed due to both a significant decrease of river water discharge from the Huanghe River and a reduction of precipitation. The shifts in nutrient chemistry could result in changes in the phytoplankton composition with an increased potential for non-diatom algal blooms. Simple box model was used to estimate the water - mass balance and nutrient budgets for the Bohai Sea. Water budgets indicate that the residual flow changed from out of the Bohai Sea before 1993, but became inflow to the Bohai Sea after then. The nutrient budgets developed indicate that the Bohai Sea was a sink for nutrients except for phosphate in 1959--1960 and 1982-- 1983 and for silicate in 1982--1983. Net water flow transports nutrients out of the Bohai Sea in 1959--1960, 1982--1983 and 1992--1993, but into the sea in 1998--1999 due to climate changes, such as precipitation and subsequent freshwater discharge. The residual fluxes of nutrients are minor relative to atmospheric deposition and riverine inputs. Conversions of phosphate values to carbon by stoichiometric ratios were used to predict that the system was net heterotrophic before 1982--1983 and net autotrophic after then. Nutrient budgets can explain the change of nutrient concentrations in the Bohai Sea except nitrates, which should include the surface runoff.  相似文献   

15.
1998年11月在长江口及周围海域进行了一个航次的环境调查,并在室内以中肋骨条藻为实验藻种,应用营养加富生物测定法对本海域浮游植物的营养需求状况进行了研究.结果表明,可大致根据离河口的远近将此海域分为3个部分:近河口光限制区、过渡带光和磷酸盐限制区、远河口氮盐限制区.P与N分别为潜在营养限制因子的界线大致沿盐度为31的等盐线.并指出,以溶解无机氮磷比的判断标准,在悬浮物浓度较高的区域会高估磷的限制作用.  相似文献   

16.
The seasonal dynamics of inorganic nutrients and phytoplankton biomass (chlorophyll a), and its relation with hydrological features, was studied in the NW Alboran Sea during four cruises conducted in February, April, July and October 2002. In the upper layers, the seasonal pattern of nutrient concentrations and their molar ratios (N:Si:P) was greatly influenced by hydrological conditions. The higher nutrient concentrations were observed during the spring cruise (2.54 μM NO3, 0.21 μM PO43− and 1.55 μM Si(OH)4, on average), coinciding with the increase of salinity due to upwelling induced by westerlies. The lowest nutrient concentrations were observed during summer (<0.54 μM NO3, 0.13 μM PO43− and 0.75 μM Si(OH)4, on average), when the lower salinities were detected. Nutrient molar ratios (N:Si:P) followed the same seasonal pattern as nutrient distribution. During all the cruises, the ratio N:P in the top 20 m was lower than 16:1, indicating a NO3 deficiency relative to PO43−. The N:P ratio increased with depth, reaching values higher than 16:1 in the deeper layers (200–300 m). The N:Si ratio in the top 20 m was lower than 1:1, excepting during spring when N:Si ratios higher than 1:1 were observed in some stations due to the upwelling event. The N:Si ratio increased with depth, showing a maximum at 50–100 m (>1.5:1), which indicates a shift towards Si-deficiency in these layers. The Si:P ratio was much lower than 16:1 throughout the water column during the four cruises. In general, the spatial and seasonal variation of phytoplankton biomass showed a strong coupling with hydrological and chemical fields. The higher chlorophyll a concentrations at the depth of the chlorophyll maximum were found in April (2.57 mg m−3 on average), while the lowest phytoplankton biomass corresponded to the winter cruise (0.74 mg m−3 on average). The low nitrate concentrations together with the low N:P ratios found in the upper layers (top 20 m) during the winter, summer and autumn cruises suggest that N-limitation could occur in these layers during great part of the year. However, N-limitation during the spring cruise was temporally overcome by nutrient enrichment caused by an intense wind-driven upwelling event.  相似文献   

17.
Nutrients, chlorophyll-a, particulate organic carbon (POC), and environmental conditions were extensively investigated in the northern East China Sea (ECS) near Cheju Island during three seasonal cruises from 2003 to 2005. In spring and autumn, relatively high concentrations of nitrate (2.6~12.4 μmol kg-1) and phosphate (0.17~0.61 μmol kg-1) were observed in the surface waters in the western part of the study area because of the large supply of nutrients from deep waters by vertical mixing. The surface concentrations of nitrate and phosphate in summer were much lower than those in spring and autumn, which is ascribed to a reduced nutrient supply from the deep waters in summer because of surface layer stratification. While previous studies indicate that upwellings of the Kuroshio Current and the Changjiang (Yangtze River) are main sources of nutrients in the ECS, these two inputs seem not to have contributed significantly to the build-up of nutrients in the northern ECS during the time of this study. The lower nitrate:phosphate (N:P) ratio in the surface waters and the positive correlation between the surface N:P ratio and nitrate concentration indicate that nitrate acts as a main nutrient limiting phytoplankton growth in the northern ECS, contrary to previous reports of phosphate-limited phytoplankton growth in the ECS. This difference arises because most surface water nutrients are supplied by vertical mixing from deep waters with low N:P ratios and are not directly influenced by the Changjiang, which has a high N:P ratio. Surface chlorophyll-a levels showed large seasonal variation, with high concentrations (0.38~4.14 mg m-3) in spring and autumn and low concentrations (0.22~1.05 mg m-3) in summer. The surface distribution of chlorophyll-a coincided fairly well with that of nitrate in the northern ECS, implying that nitrate is an important nutrient controlling phytoplankton biomass. The POC:chlorophyll-a ratio was 4~6 times higher in summer than in spring and autumn, presumably because of the high summer phytoplankton death rate caused by nutrient depletion in the surface waters.  相似文献   

18.
The importance of dissolved organic phosphorus(DOP) as a potential nutrient source for primary producers in marine systems has been recognized for up to eight decades, but currently, the understanding of the biogeochemistry of DOP is in its infancy. In the present study, monthly data between 2000 and 2014 were used to analyze the temporal and spatial distributions of DOP in the Mir Bay, the northern South China Sea. The DOP residence time(T_(DOP)) was also investigated using a simple regression analysis in combination with chlorophyll a(Chl a) measurements while excess DOP(ΔDOP), produced by the biogeochemical processes of autotrophic production and heterotrophic removal, was determined using a two-component mixing mass-balance model in combination with salinity measurements. The results showed that the DOP concentration was(0.017±0.010) mg/L higher in the surface-water compared with the bottom-water and higher in the inner Tolo Harbour and waters adjacent to Shatoujiao compared with the main zone of the bay. Although seasonal changes and annual variability in the DOP were small, the surface DOP concentration was higher in the wet season(April–September)than in the dry season(October–March) due to the impacts of seaward discharges and atmospheric deposition into the bay. Measurement and regression results showed that the DOP release rate from phytoplankton production was about 1.83(gP)/(gChl a) and the T_(DOP) was about 7 d, which implied that the DOP cycle in the bay was rapid. The ΔDOP was calculated from the model to be about 0.000 mg/L in the main zone of the bay and about 0.002 mg/L in the inner Tolo Harbour and waters adjacent to Shaotoujiao, suggesting that the autotrophic production of DOP was almost balanced by the heterotrophic removal in the main zone of the bay and dominated in the inner Tolo Harbour and waters adjacent to Shaotoujiao. In conclusion, the Mirs Bay is very productive and fairly heterotrophic.  相似文献   

19.
营养盐因子对龙须菜和菊花江蓠氮磷吸收速率的影响   总被引:17,自引:0,他引:17  
本文在实验室条件下,研究了营养盐因子对龙须菜和菊花江蓠N、P吸收速率的 影响,分别对不同氮和磷的浓度、氮磷比及不同化合态氮对这两种藻类氮、磷吸收速 率的影响进行了实验与分析.结果表明:在适宜范围内,两种海藻对氮、磷的吸收速率 随介质中氮、磷浓度的增加而增加;不同氮磷对两种海藻N吸收速率的影响不存在 显著差异,但对磷吸收速率的影响非常显著,最高对磷吸收速率在介质的氮磷比为 10:1时;海藻对NH4-N的吸收速率随着NO3-N/NH4-N比的降低而增加,对PO43-P的 吸收速率与对NH4-N的吸收相似,而对NO3-N的吸收速率与对NH4-N的吸收相反.  相似文献   

20.
于2010年8月和10月对厦门海域营养盐和浮游植物等开展了两个航次的调查,目的在于研究该海域营养盐含量和比率变化及其对水采浮游植物群落的影响.各化学和生物要素的采集、保存和分析按照《海洋调查规范》或《海洋监测规范》的相关方法进行.研究结果表明,厦门海域浮游植物生长的营养盐限制性因子与1998年的研究结果比较,依然为PO4-P,而SiO3-Si含量和DIN含量相对充足.各项营养盐含量与盐度都有较明显的负相关性,其中保守性最明显的是DIN,而PO4-P与盐度的相关性相对最低.此外,8月份鉴定到的甲藻门种类和生物量明显高于10月份.本文认为,目前厦门海域营养盐比率变化的主要压力为N/P摩尔比率失衡.随着人为输入氮源的增加,在富氮的九龙江口及其邻近海域,极易发生中肋骨条藻赤潮,该藻的生物量与NO3-N和SiO3-Si含量的相关性十分明显.研究发现,厦门甲藻/硅藻生物量的比值与NO3-N和N/P摩尔比率有一定的正相关性,可能预示着该海域无机氮含量的增加及其引起的N/P摩尔比率增大会促进甲藻门种类的生长.并且浮游植物Shannon生物多样性指数可作为反映厦门海域富营养化较好的生物指标.  相似文献   

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