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161.
Heavy metal is a main pollutant in the marine ecosystem, so study on the effect of heavy metal on phytoplankton is important.
Algae (Chaetoceros sp.,Dunaliella sp.,Dicrateria zhanjiangenis Hu. var. sp.) were laboratory cultured to observe the effect of heavy metals on their growth. The effect of different metal ion concentration,
the detoxication effect of complexation agents and the growth of algae in different media and different nutrition levels were
studied to evaluate the effect of metal speciation. It is proved that trace amount of heavy metals can stimulate the growth
of algae cells but that high concentration is lethal. The sequence of toxicity is Cd2+>Zn2+>Pb2+. In ordinary nutrition conditions, the detoxication sequence of complexation agents toChaetoceros sp. is EDTA >sodium salicylate>sodium oxalate >sodium citrate>sulfanilic acid>O-phenanthroline. This is in good conformity
with the stability constant sequence of these agents with copper and good evidence that toxicity of metal ion is related to
its activity and not to its total concentration.
Project supported by the Fund of Excellent Young Teachers of State Educational Commission of China. 相似文献
162.
??GNSS??????????У??轫GNSS?????????????????????????????????????????GNSS???????????????????????????????????????????????????????????????????????????????????????????????????????????????е???????????????????????е????λ???ó????????????????????????????????????????????????????????????????о???GNSS???????????????????????????????????????????????????????????????????????????????????????????????????????????? 相似文献
163.
Arctic sea-ice motion and its relation to pressure field 总被引:5,自引:0,他引:5
Daily Arctic sea-ice motion maps during the winter seasons (December–March) from December 1988 to March 2003 derived from
NSCAT, QuikSCAT, SSM/I, and AMSRE data by a wavelet analysis method have been merged with those derived from buoy data. These
merged sea-ice motion data have been used to study the circulation regimes and winter-to-winter variability of Arctic sea-ice
motion. The relation between sea-ice motion and the pressure field in the Arctic Ocean was also studied by applying Principal
Component Analysis (PCA) to the monthly merged sea-ice motion data and the monthly pressure field data from IABP. The mean
Arctic sea-ice motion map of the 15 winter seasons has two distinct features: the Beaufort Gyre and a cyclonic circulation
system in the Eurasian Basin, which moves ice from the Laptev Sea to Fram Strait. The strengths and sizes of the two features
change from one winter season to another. Seasons with a strong or normal Beaufort Gyre alternate with seasons with a weak
or no Beaufort Gyre every one to three seasons. The principal components of the first two modes of PCA of the monthly sea-ice
motion are closely correlated with their counterparts of the monthly pressure field in the Arctic Ocean. The mode-one components
of these two anomalies alternate between anticyclonic and cyclonic circulation systems. The correlation between Arctic Oscillation
indexes and the principal components of the first mode of PCA of the monthly Arctic sea-ice motion is low but statistically
significant. 相似文献
164.
Numerical study of baroclinic tides in Luzon Strait 总被引:5,自引:1,他引:5
The spatial and temporal variations of baroclinic tides in the Luzon Strait (LS) are investigated using a three-dimensional
tide model driven by four principal constituents, O1, K1, M2 and S2, individually or together with seasonal mean summer or winter stratifications as the initial field. Barotropic tides propagate
predominantly westward from the Pacific Ocean, impinge on two prominent north-south running submarine ridges in LS, and generate
strong baroclinic tides propagating into both the South China Sea (SCS) and the Pacific Ocean. Strong baroclinic tides, ∼19
GW for diurnal tides and ∼11 GW for semidiurnal tides, are excited on both the east ridge (70%) and the west ridge (30%).
The barotropic to baroclinic energy conversion rate reaches 30% for diurnal tides and ∼20% for semidiurnal tides. Diurnal
(O1 and K1) and semidiurnal (M2) baroclinic tides have a comparable depth-integrated energy flux 10–20 kW m−1 emanating from the LS into the SCS and the Pacific basin. The spring-neap averaged, meridionally integrated baroclinic tidal
energy flux is ∼7 GW into the SCS and ∼6 GW into the Pacific Ocean, representing one of the strongest baroclinic tidal energy
flux regimes in the World Ocean. About 18 GW of baroclinic tidal energy, ∼50% of that generated in the LS, is lost locally,
which is more than five times that estimated in the vicinity of the Hawaiian ridge. The strong westward-propagating semidiurnal
baroclinic tidal energy flux is likely the energy source for the large-amplitude nonlinear internal waves found in the SCS.
The baroclinic tidal energy generation, energy fluxes, and energy dissipation rates in the spring tide are about five times
those in the neap tide; while there is no significant seasonal variation of energetics, but the propagation speed of baroclinic
tide is about 10% faster in summer than in winter. Within the LS, the average turbulence kinetic energy dissipation rate is
O(10−7) W kg− 1 and the turbulence diffusivity is O(10−3) m2s−1, a factor of 100 greater than those in the typical open ocean. This strong turbulence mixing induced by the baroclinic tidal
energy dissipation exists in the main path of the Kuroshio and is important in mixing the Pacific Ocean, Kuroshio, and the
SCS waters. 相似文献
165.
166.
Biogeochemical records of paleoenvironmental changes in Nainital Lake,Kumaun Himalayas,India 总被引:1,自引:0,他引:1
Preetam Choudhary Joyanto Routh Govind J. Chakrapani Bhishm Kumar 《Journal of Paleolimnology》2009,42(4):571-586
Rapid urbanization and increased tourism around Nainital Lake in the Kumaun Himalayan region in north India has raised concerns
about sediment and water pollution. Lead-210 dated sediment cores from the lake represent ~95 years of accumulation and yield
a mean sedimentation rate of ~4.7 mm year−1. Total organic carbon (TOC), percent N and S and their atomic C/N and C/S ratios, stable isotopes (δ13C, δ15N, and δ34S), and specific biomarkers (n-alkanes and pigments) were measured in the core. Organic matter is primarily derived from in-lake algal production and TOC
flux varies from 1.0 to 3.5 g m−2 year−1. Sediments are anoxic (Eh −328 to −187 mV) and have low (0.10–0.30 g m−2 year−1) N, but high (0.37–1.0 g m−2 year−1) S flux. Shifts in δ13C, δ15N, and δ34S suggest in-lake microbial processes dominated by denitrification and sulfate reduction. The sediments are dominated by short-chain
hydrocarbons with low Carbon Preference Index values. The pigments indicate a gradual shift to cyanobacterial domination of
the phytoplankton community in recent years. Despite an increase in external input of nutrients, the trophic state of the
lake has remained largely unchanged, and the perceived human-induced impacts are limited. 相似文献
167.
Stress Responses to Rapid Temperature Changes of the Juvenile Sea Cucumber (Apostichopusjaponicus Selenka) 总被引:2,自引:0,他引:2
DONG Yunwei JI Tingting DONG Shuanglin 《中国海洋大学学报(英文版)》2007,6(3):275-280
Activities of hexokinase (HK), pyruvate kinase (PK), superoxide dismutase (SOD) and catalase (CAT) and Hsp70 level were measured to evaluate the response of the commercially important sea cucumber (Apostichopus japonicus Selenka) to rapid temperature changes in laboratory. Animals were subjected to a higher temperature (from 10 to 20℃) (Tinc treatment) or to a lower temperature (from 20 to 10℃) (Tddec treatment) for 72 h. At 1, 3, 12, 24, 72 h of exposure, animals were removed and prepared for further analysis. Results showed that the effect of acute temperature changes on enzyme activities was significant. In Tinc treatment, activities of SOD and CAT increased immediately. The significant enhancement of SOD and CAT activities suggested that oxidative stress increases significantly when ambient temperature increasing from 10 to 20℃. The up-regulation of Flsp70 in Tinc and Tdec treatments indicated that Hsp70 was a bioindicator of thermal stress in the sea cucumber, and the expression pattern depended on the thermal treatment. 相似文献
168.
全波形反演是一种利用地震波传播的动力学特征来获取地下介质物性参数的反演方法,可为揭示地下精细结构提供重要依据。本文以弹性波方程作为数学模型来模拟地震波传播规律并进行相应的反演方法研究。为提高计算效率与反演结果的准确性,可将近似解析离散化(NAD)算子用于频率域弹性波方程的正演模拟。本文在频率域NAD离散的基础上推导阻抗矩阵的稀疏分块结构与反演目标函数对模型参数的梯度计算公式,由此建立基于NAD算子的频率域弹性波全波形反演方法。为验证该方法的有效性,文中通过数值实验对多种典型介质模型进行反演计算,均得到了理想的反演结果。
相似文献169.
Janice Brahney John J. Clague Brian Menounos Thomas W. D. Edwards 《Journal of Paleolimnology》2008,40(1):489-505
The level of Kluane Lake in southwest Yukon Territory, Canada, has fluctuated tens of metres during the late Holocene. Contributions
of sediment from different watersheds in the basin over the past 5,000 years were inferred from the elemental geochemistry
of Kluane Lake sediment cores. Elements associated with organic material and oxyhydroxides were used to reconstruct redox
fluctuations in the hypolimnion of the lake. The data reveal complex relationships between climate and river discharge during
the late Holocene. A period of influx of Duke River sediment coincides with a relatively warm climate around 1,300 years BP.
Discharge of Slims River into Kluane Lake occurred when Kaskawulsh Glacier advanced to the present drainage divide separating
flow to the Pacific Ocean via Kaskawulsh and Alsek rivers from flow to Bering Sea via tributaries of Yukon River. During periods
when neither Duke nor Slims river discharged into Kluane Lake, the level of the lake was low and stable thermal stratification
developed, with anoxic and eventually euxinic conditions in the hypolimnion. 相似文献
170.
Climate condition over a region is mostly determined by the changes in precipitation, temperature and evaporation as the key climate variables. The countries belong to the Belt and Road region are subjected to face strong changes in future climate. In this paper, we used five global climate models from the latest Sixth Phase of Coupled Model Intercomparison Project (CMIP6) to evaluate future climate changes under seven combined scenarios of the Shared Socioeconomic Pathways and the Representative Concentration Pathways (SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0, SSP4-3.4, SSP4-6.0 and SSP5-8.5) across the Belt and Road region. This study focuses on undertaking a climate change assessment in terms of future changes in precipitation, air temperature and actual evaporation for the three distinct periods as near-term period (2021-2040), mid-term period (2041-2060) and long-term period (2081-2100). To discern spatial structure, K?ppen-Geiger Climate Classification method has been used in this study. In relative terms, the results indicate an evidence of increasing tendency in all the studied variables, where significant changes are anticipated mostly in the long-term period. In addition to, though it is projected to increase under all the SSP-RCP scenarios, greater increases will be happened under higher emission scenarios (SSP5-8.5 and SSP3-7.0). For temperature, robust increases in annual mean temperature is found to be 5.2 °C under SSP3-7.0, and highest 7.0 °C under SSP5-8.5 scenario relative to present day. The northern part especially Cold and Polar region will be even more warmer (+6.1 °C) in the long-term (2081-2100) period under SSP5-8.5. Similarly, at the end of the twenty-first century, annual mean precipitation is inclined to increase largely with a rate of 2.1% and 2.8% per decade under SSP3-7.0 and SSP5-8.5 respectively. Spatial distribution demonstrates that the largest precipitation increases are to be pronounced in the Polar and Arid regions. Precipitation is projected to increase with response to increasing warming most of the regions. Finally, the actual evaporation is projected to increase significantly with rate of 20.3% under SSP3-7.0 and greatest 27.0% for SSP5-8.5 by the end of the century. It is important to note that the changes in evaporation respond to global mean temperature rise consistently in terms of similar spatial pattern for all the scenarios where stronger increase found in the Cold and Polar regions. The increase in precipitation is overruled by enhanced evaporation over the region. However, this study reveals that the CMIP6 models can simulate temperature better than precipitation over the Belt and Road region. Findings of this study could be the reliable basis for initiating policies against further climate induced impacts in the regional scale. 相似文献