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101.
Fate of paralytic shellfish poisoning toxins in purple clam Hiatula rostrata,in outdoor culture and laboratory culture 总被引:1,自引:0,他引:1
Purple clams (Hiatula rostrata Lighttoot) accumulate paralytic shellfish poisoning (PSP) toxins produced by a toxic strain of the dinoflagellate Alexandriun minutum Halim. The results confirm the data of our previous study concerning the muscle and siphon that were not showing a gradual rise in toxicity when shellfish accumulated more A. minutum. However, muscle and siphon are intermittently toxic both in exposure and depuration period in laboratory cultured purple clams. PSP toxins were detected in outdoor cultured purple clams, whereas no A. minutum were found in the culture pond during most of the survey time. The outdoor cultured purple clams need longer time to decrease toxicity to allowable levels than laboratory cultured purple clams. It was shown that laboratory data may not predict times over which pond-cultured purple clams may prove toxic to consumers. 相似文献
102.
Wen-Chen Chou Gwo-Ching Gong Chun-Mao Tseng David D. Sheu Chin-Chang Hung Lo-Ping Chang Li-Wen Wang 《Marine Chemistry》2011,123(1-4):44-55
Measurements of dissolved inorganic carbon (DIC), pH, total alkalinity (TA), and partial pressure of CO2 (pCO2) were conducted at a total of 25 stations along four cross shelf transects in the East China Sea (ECS) in January 2008. Results showed that their distributions in the surface water corresponded well to the general circulation pattern in the ECS. Low DIC and pCO2 and high pH were found in the warm and saline Kuroshio Current water flowing northeastward along the shelf break, whereas high DIC and pCO2 and low pH were mainly observed in the cold and less saline China Coastal Current water flowing southward along the coast of Mainland China. Difference between surface water and atmospheric pCO2 (ΔpCO2), ranging from ~ 0 to ? 111 μatm, indicated that the entire ECS shelf acted as a CO2 sink during winter with an average flux of CO2 of ?13.7 ± 5.7 (mmol C m? 2 day? 1), and is consistent with previous studies. However, pCO2 was negatively correlated with temperature for surface waters lower than 20 °C, in contrast to the positive correlation found in the 1990s. Moreover, the wintertime ΔpCO2 in the inner shelf near the Changjiang River estuary has appreciably decreased since the early 1990s, suggesting a decline of CO2 sequestration capacity in this region. However, the actual causes for the observed relationship between these decadal changes and the increased eutrophication over recent decades are worth further study. 相似文献
103.
Leonardo Casini Stefano Andreucci Daniele Sechi Chun‐Yuan Huang Chuan‐Chou Shen Vincenzo Pascucci 《地学学报》2020,32(4):261-271
Precise dating of the activity of Late Pleistocene to Holocene neo‐tectonic structures is crucial to quantify the rate of deformation in low‐seismicity regions. Sardinia is a relatively stable continental fragment set in the middle of the tectonically active Western Mediterranean belt. This paper provides evidences of significant uplift of northwest Sardinia that support an ongoing tectonic activity since the Marine Isotopic Stage 7 (MIS 7; ca. 220 ka). In particular, it documents for the first time Late Pleistocene to Holocene tectonics based on luminescence dating of travertine sealing a major NNE‐SSW fault. 相似文献
104.
The Discovery of Natural Native Uranium and Its Significance 总被引:2,自引:0,他引:2
This study analyzed the composition and uranium valence of pitchblendes sampled from the hydrothermal Guidong and Zhuguang uranium deposits of the middle Nanling metallogenic belt, Southern China using X-ray photoelectron spectroscopy (XPS). A revolutionary discovery is that the uranium not only exists in the forms of tetravalent and hexavalent uranium oxides, but also occurs in the form of native uranium. This is the first discovery of the existence of native uranium in nature. It greatly helps to reveal the origin of hydrothermal mineralization of uranium, and also has great significance for studying the thermal energy, formation and evolution of the earth. 相似文献
105.
Analyses of extreme climate events over china based on CMIP5 historical and future simulations 总被引:1,自引:0,他引:1
Based on observations and 12 simulations from Coupled Model Intercomparison Project Phase 5 (CMIP5) models, cli- matic extremes and their changes over China in the past and under the future scenarios of three Representative Concentration Pathways (RCPs) are analyzed. In observations, frost days (FD) and low-temperature threshold days (TN10P) show a de- creasing trend, and summer days (SU), high-temperature threshold days (TX90P), heavy precipitation days (R20), and the contribution of heavy precipitation days (P95T) show an increasing trend. Most models are able to simulate the main char- acteristics of most extreme indices. In particular, the mean FD and TX90P are reproduced the best, and the basic trends of FD, TN10P, SU and TX90P are represented. For the FD and SU indexes, most models show good ability in capturing the spatial differences between the mean state of the periods 1986--2005 and 1961-80; however, for other indices, the simulation abilities for spatial disparity are less satisfactory and need to be improved. Under the high emissions scenario of RCP8.5, the century-scale linear changes of the multi-model ensemble (MME) for FD, SU, TN10P, TX90P, R20 and P95T are -46.9, 46.0, -27.1, 175.4, and 2.9 days, and 9.9%, respectively; and the spatial change scope for each index is consistent with the emissions intensity. Due to the complexities of physical process pararneterizations and the limitation of forcing data, great uncertainty still exists with respect to the simulation of climatic extremes. 相似文献
106.
Analogue-dynamical prediction of monsoon precipitation in Northeast China based on dynamic and optimal configuration of multiple predictors 下载免费PDF全文
Based on the National Climate Center (NCC) of China operational seasonal prediction model results for the period 1983–2009
and the US National Weather Service Climate Prediction Center merged analysis of precipitation in the same period, together
with the 74 circulation indices of NCC Climate System Diagnostic Division and 40 climate indices of NOAA of US during 1951–2009,
an analogue-dynamical technique for objective and quantitative prediction of monsoon precipitation in Northeast China is proposed
and implemented. Useful information is extracted from the historical data to estimate the model forecast errors. Dominant
predictors and the predictors that exhibit evolving analogues are identified through cross validating the anomaly correlation
coefficients (ACC) among single predictors, meanwhile with reference of the results from the dynamic analogue bias correction
using four analogue samples. Next, an optimal configuration of multiple predictors is set up and compared with historical
optimal multi-predictor configurations and then dynamically adjusted. Finally, the model errors are evaluated and utilized
to correct the NCC operational seasonal prediction model results, and the forecast of monsoon precipitation is obtained at
last. The independent sample validation shows that this technique has effectively improved the monsoon precipitation prediction
skill during 2005–2009. This study demonstrates that the analogue-dynamical approach is feasible in operational prediction
of monsoon precipitation. 相似文献
107.
Jinfu Shu Xiaojia Chen I.-Ming Chou Wenge Yang Jingzhu Hu Russell J. Hemley Ho-kwang Mao 《地学前缘(英文版)》2011,2(1):93-100
The structural stability of methane hydrate under pressure at room temperature was examined by both in-situ single-crystal and powder X-ray diffraction techniques on samples with structure typesⅠ,Ⅱ,and H in diamond-anvil cells.The diffraction data for typesⅡ(sⅡ) and H(sH) were refined to the known structures with space groups Fd3m and P6_3/mmc,respectively.Upon compression,sⅠmethane hydrate transforms to the sⅡphase at 120 MPa,and then to the sH phase at 600 MPa.The sⅡmethane hydrate was found to coexist... 相似文献
108.
Sin Chan Chou Andr de Arruda Lyra Jorge Lus Gomes Daniel Andrs Rodriguez Minella Alves Martins Nicole Costa Resende Priscila da Silva Tavares Claudine Pereira Dereczynski Isabel Lopes Pilotto Alessandro Marques Martins Lus Felipe Alves de Carvalho Jos Luiz Lima Onofre Idalcio Major Manuel Penhor Adrito Santana 《Climate Dynamics》2020,54(9):4021-4042
Sao Tome and Principe is a small insular African country extremely vulnerable to rising sea levels and impacts such as inundation, shore line change, and salt water intrusion into underground aquifers. Projections of climate change have considered coarse model resolutions. The objective of this work is to dynamically downscale the global model projections to 4-km resolution and to assess the climate change in the Sao Tome and Principe islands. The global climate projections are provided by the Canadian Earth System Model under two Representative Concentration Pathways greenhouse gas scenarios, RCP4.5 and RCP8.5. The downscaling is produced by the Eta regional climate model. The baseline period is taken between 1971 and 2000, and the future climate period is taken between 2041 and 2070. The 2-m temperature simulations show good agreement with station data. The model simulates temperature more accurately than precipitation. The precipitation simulations systematically show underestimation and delay of the rainy and the dry seasons by about 1 month, a feature inherited from the global climate model. In the middle of the 21st century, projections show the strongest warming in the elevated parts of the Sao Tome Island, especially in February under RCP8.5. Warmer nights and warmer days become more frequent in the islands when compared with those in the present. While under RCP4.5, precipitation increases in the islands; under RCP8.5, it decreases everywhere in both islands. Heavy precipitation rates should increase, especially in the south-southwestern parts of the Sao Tome islands. Detailed spatial variability of the temperature and precipitation changes in the islands can only be revealed at very high spatial model resolution. Implications for the potential energy production from two major river basins are assessed in this work. 相似文献
109.
110.
Automatically extracting drainage networks from digital elevation models coupled with the constant stream threshold value is a regular method. These extracted networks can be verified by comparing the channel initiation points with those from real networks. From the results analysed, the differences in channel initiation points will affect the network geometries, geomorphological indices and hydrological responses. This paper develops two automatic algorithms, the headwater‐tracing method and the fitness index, to trace the flow paths from headwaters to the outlet and to calculate the reasonable stream threshold. Instead of the method determined by trial and error or field survey, the accurate channel initiation points can be obtained from airborne photographs coupled with high‐resolution SPOT images for suitable drainage network extraction. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献