Nutrient and chlorophyll a anomaly in red-tide periods of 2003-2008 in Sishili Bay, China     

郝彦菊  唐丹玲  喻龙  邢前国 《中国海洋湖沼学报》2011,29(3):664-673

Sishili Bay is the most important aquiculture and tourism area for the city of Yantai, China; however, red tides occurred frequently and have caused huge economic losses in this bay in recent years. To gain a better understanding of the local ecological environments in the bay, we conducted this research between 2003 and 2008 to analyze variations in nutrients and chlorophyll (chl-a) during high frequency red tide period (May to September). The results show that the chl-a concentration increased from 2.70 in 2003 to 7.26 mg/m3 in 2008, while the concentration of total inorganic nitrogen (TIN) and silicate (SiO3-Si) increased lineally from 5.18 and 1.45 μmol/L in 2003 to 18.57 and 9.52 μmol/L in 2008, respectively, and the annual phosphate (PO4-P) varied between 0.15 and 0.46 μmol/L. Special attention was given to a red tide in August 2007 occurred when water temperature was high and nutrient concentrations increased sharply because of a heavy rainfall. Overall, the results show the P limitation in Sishili Bay, and reveal that red tides were caused by eutrophication from terrestrial inputs and local warm weather, particularly during rainy periods. Therefore, to control red tide, greater efforts should be made to reduce sewage discharges into Sishili Bay, particularly during rainfall seasons.  相似文献   

Phytoplankton pigment patterns and community composition in the northern South China Sea during winter   总被引：1，自引：0，他引：1  

�Ժ��  ������  ��ѧ��  ����  �ַ��  �Ǿ� 《中国海洋湖沼学报》2011,29(2):233-245

Phytoplankton pigment patterns and community composition were investigated in the northern South China Sea using high-performance liquid chromatography and the CHEMTAX software from February 11 to 23, 2009. We recognized four different vertical distribution patterns of pigments: chlorophyll a (Chl a)-like type, divinyl chlorophyll a (DV Chl a) type, even distribution type, and surface type. The average value of ratios of accessory photo-protective pigments (APP) to accessory photo-synthetic pigments was 0.89±0.63 in the upper 50 m and 0.16±0.06 below 50 m depth. With increasing depth, APP decreased and photo-synthetically active radiation was attenuated. There was an obvious succession in the phytoplankton community from inshore to the open sea. Diatoms were dominant in the inshore region, while pelagophytes, Prochlorococcus, cyanobacteria and prymnesiophytes were dominant in the open sea. The vertical distribution of phytoplankton also differed greatly from inshore to the open sea. In the coastal and shelf region, diatoms were important components in the whole water column. Cyanobacteria also had a high abundance at the Subsurface Chlorophyll a Maxima (SCM) in the shelf region. In the slope and open sea, Prochlorococcus and cyanobacteria were important groups above the SCM, while pelagophytes dominated below the SCM.  相似文献   

基于土地利用分类模型和重力模型耦合的人口分布模拟——以武汉市人口数据为例     

丁文秀  赵伟  左德霖  张亦梅  王维维  杨志强 《大地测量与地球动力学》2011,31(Z1):127-131

将土地分类模型和重力模型耦合形成新模型,并以武汉市人口数据为例,用耦合后的新模型模生成武汉市人口网格数据.经数据验证表明,耦合后的新模型在计算精度方面有了较大的提高.  相似文献   

贵州省2020年5月极端性高温事件研究          下载免费PDF全文

莫乙冬  苟杨  唐红忠  潘启学 《中低纬山地气象》2023,47(4):65-69

2020年5月贵州省出现极端高温天气事件,本文利用贵州省84个气象观测站日平均气温和最高气温资料、美国气象环境预报中心的逐日再分析高度场资料以及美国海洋大气管理局的日平均海表面温度（SST）资料,利用超前滞后相关等方法对贵州省2020年5月“极端性高温事件”进行研究。得出如下结论：（1）2020年5月贵州省约有29%的站点极端日最高气温超过了1981年以来的历史极值,约58%的站点突破1981年以来5月同期历史极值,西太平洋副热带高压显示为异常西扩加强的态势,同时伴随南亚高压东伸增强,两个高压在不同高度上的配合导致深厚高压的异常出现,是此次贵州极端性高温事件发生的重要因素。（2） 2020年5月在欧亚大陆中高纬对流层上层有明显的Rossby波列结构,有利于贵州极端性高温事件出现。（3）热带西大西洋SST在月尺度内异常阶段性增暖,可作为贵州省极端性高温天气发生的重要前期信号,并且增暖过程比高温事件提前约14天,具有一定的前期指示意义。  相似文献   

1971—2020年江西暴雨预警信号等级时空分布特征          下载免费PDF全文

唐传师  许彬  雷星宇 《气象与减灾研究》2023,46(1):52-59

利用1971—2020年江西省83站国家气象观测站逐时降水资料,采用EOF分析、Mann-Kendall突变检验、滑动t检验、Morlet小波变换等方法,对江西暴雨预警信号等级的时空分布特征进行了分析。结果表明：1)江西暴雨蓝色、黄色和橙色预警信号年平均发布频次均呈“东北多、西南少”的地域分布,暴雨红色预警主要在鄱阳湖南侧存在多发区;上饶市和景德镇市是暴雨蓝色和黄色预警信号发布频次异常的敏感区,且在江西北部与中部表现出较明显的反位相变化特征。2)暴雨蓝色预警信号发布时间表现为单峰型,主要出现在13—16时,其他三种级别暴雨预警信号发布时间均表现为双峰型,主要有上午和傍晚两个易发时段。3)暴雨红色预警信号发布主要在6—8月,其他等级暴雨预警主要在5—8月,各等级暴雨预警信号均在6月发布最多。4)各等级暴雨预警信号发布频次均存在6—8 a的年际周期振荡,目前江西暴雨蓝色和黄色预警信号发布频次进入偏少期,而暴雨橙色和红色预警信号发布进入偏多期。5)暴雨红色预警信号发布频次呈0.70次/(10 a)的线性增加趋势,且在1992年发生明显由偏少转为偏多的突变,大部地区暴雨红色预警信号发布时降水极...  相似文献   

Monazite and xenotime U–Th–Pb geochronology by ion microprobe: dating highly fractionated granites at Xihuashan tungsten mine, SE China     

Q. L. Li  X. H. Li  Z. W. Lan  C. L. Guo  Y. N. Yang  Y. Liu  G. Q. Tang 《Contributions to Mineralogy and Petrology》2013,166(1):65-80

Zircon, monazite, and xenotime have proven to be valuable chronometers for various geological processes due to their commonly high-U–Th and low common Pb contents. However, zircons that have crystallized in highly fractionated granites often have such high-U contents that radiation damage can lead to scattered U–Pb ages when measured with secondary ion mass spectrometry (SIMS). In this study, monazite and xenotime were separated from a number of highly fractionated granites at the Xihuashan tungsten mine, Southeast China, for alternative dating methods by SIMS. For monazite analysis, obvious excess ²⁰⁴Pb signal (mainly from interference of ²³²Th¹⁴⁴Nd¹⁶O₂ ⁺⁺) was observed in high-Th (>2 wt%) monazite, which hinders ²⁰⁴Pb-based common Pb corrections. A ²⁰⁷Pb-based common Pb correction method was used instead. By employing power law relationships between Pb⁺/U⁺ versus UO₂ ⁺/U⁺, Pb⁺/Th⁺ versus ThO₂ ⁺/Th⁺ and suitable exponentials, monazites with ThO₂ contents in the range of ~3–19 % do not exhibit this matrix effect. Independent SIMS U–Pb ages and Th–Pb ages of three phases of Xihuashan granite samples were consistent with each other and yielded dates of 158.7 ± 0.7, 158.0 ± 0.7, and 156.9 ± 0.7 Ma, respectively. Xenotime does show marked matrix effects due to variations of U, Th, and Y [or total rare earth element (REE), referred as ΣREE hereafter] contents. Suitable correction factors require end-member standards with extremely high or low U, Th, and Y (or ΣREE) contents. No excess ²⁰⁴Pb was observed, indicating that the ²⁰⁴Pb-based common Pb correction method is feasible. Independent ²⁰⁷Pb/²⁰⁶Pb ages can be obtained, although multi-collector mode is necessary to improve precision. The main difficulties with dating xenotime are when high-Th (U) mineral inclusions are ablated. We can identify when this occurs, however, by comparing the measured UO₂ ⁺/U⁺ and ThO₂ ⁺/Th⁺ with those in xenotime standards. Three xenotime samples from the first phase of Xihuashan granite yielded a weighted mean ²⁰⁷Pb/²⁰⁶Pb date of 159.5 ± 4.4 Ma (MSWD = 1.0) and a ²⁰⁶Pb/²³⁸U date of 159.4 ± 0.9 Ma (MSWD = 1.6), which are consistent with monazite U–Pb and Th–Pb ages from the same granites. This study demonstrates that monazite and xenotime are better SIMS chronometers for highly fractionated granites than zircon, which can yield doubtful ages due to high-U contents.  相似文献   

Vulnerability of population and transportation infrastructure at the east bank of Delaware Bay due to coastal flooding in sea-level rise conditions   总被引：1，自引：1，他引：0  

Han Song Tang  Steven I-Jy Chien  Marouane Temimi  Cheryl Ann Blain  Qu Ke  Liuhui Zhao  Simon Kraatz 《Natural Hazards》2013,69(1):141-163

Catastrophic flooding associated with sea-level rise and change of hurricane patterns has put the northeastern coastal regions of the United States at a greater risk. In this paper, we predict coastal flooding at the east bank of Delaware Bay and analyze the resulting impact on residents and transportation infrastructure. The three-dimensional coastal ocean model FVCOM coupled with a two-dimensional shallow water model is used to simulate hydrodynamic flooding from coastal ocean water with fine-resolution meshes, and a topography-based hydrologic method is applied to estimate inland flooding due to precipitation. The entire flooded areas with a range of storm intensity (i.e., no storm, 10-, and 50-year storm) and sea-level rise (i.e., current, 10-, and 50-year sea level) are thus determined. The populations in the study region in 10 and 50 years are predicted using an economic-demographic model. With the aid of ArcGIS, detailed analysis of affected population and transportation systems including highway networks, railroads, and bridges is presented for all of the flood scenarios. It is concluded that sea-level rise will lead to a substantial increase in vulnerability of residents and transportation infrastructure to storm floods, and such a flood tends to affect more population in Cape May County but more transportation facilities in Cumberland County, New Jersey.  相似文献   

川中东北部中-下侏罗统湖相碳酸盐岩碳氧同位素特征及其古环境意义   总被引：1，自引：1，他引：0       下载免费PDF全文

张葳  李智武  冯逢  翟中华  孙玮  汤聪  丁一  刘树根 《古地理学报》2013,15(2):247-260

在钻井岩心观察和岩石学分析的基础上,对川中东北部龙岗地区中-下侏罗统自流井组和凉高山组典型钻井取心段碳酸盐岩样品进行了碳氧同位素分析。40余件样品的测试结果表明,δ¹³C_PDB值在-1.24‰～4.59‰之间,除了1个负值外,都为正值。δ¹⁸O_PDB值在-15.7‰～-9.83‰之间,都为负值。与海相和陆相碳酸盐岩同位素值对比显示,自流井期和凉高山期古湖泊均表现出内陆开放性淡水湖泊的特点,没有经过明显的海水入侵。在中-下侏罗统广泛存在的碳同位素正偏移是由湖泊初级生产力提高所导致的。岩相和同位素变化显示了古湖平面经历了2次主旋回和6次次级旋回变化,湖平面变化总体表现为东岳庙段沉积期＞大一三亚段沉积期＞大一亚段沉积期＞凉高山期＞马鞍山段沉积期。古湖泊初级生产力的变化表现为大一三亚段沉积期＞东岳庙段沉积期＞大一亚段沉积期＞凉高山期＞马鞍山段沉积期。  相似文献   

http://www.sciencedirect.com/science/article/pii/S1674987113000297   总被引：1，自引：0，他引：1  

Haoshu Tang  Yanjing Chen 《地学前缘(英文版)》2013,4(5):583-596

This paper compiles lithostratigraphic and geochronological data obtained for the Palaeoproterozoic glacial diamictite-bearing successions,and thereby provides insights into understanding the geological processes causing the Huronian Glaciation Event.The majority of evidence for appearances of this glaciation event can be related to the Kenorland supercontinent breakup,allied to significant atmospheric change,as well as blooms of biogeochemical oxygenic photosynthesis.In this paper,the Huronian Glaciation Event is constrained to have occurred synchronously during 2.29-2.25 Ga,accompanied by dramatic environmental changes characteristic of the Great Oxidation Event which includes the pre- 2.3 Ga hydrosphere oxidation and the post-2.3 Ga atmosphere oxygenation.  相似文献   

Levels, seasonal variations, and health risks assessment of ambient air pollutants in the residential areas     

W. C. Zhao  J. P. Cheng  Z. Y. Yu  Q. L. Tang  F. Cheng  Y. W. Yin  W. H. Wang 《International Journal of Environmental Science and Technology》2013,10(3):487-494

People living in the urban area and the surrounding suburban area have disparities in exposure and health risks due to different levels of ambient air pollutants. The main objective of this study is to investigate the concentrations, seasonal variations, and related health risks of ambient air pollutants (PM₁₀, NO₂, and SO₂) in urban and suburban areas of Ningbo, China. The results showed that the average PM₁₀, NO₂, and SO₂ concentrations in the urban area were 85.2, 49.3, and 37.4 μg/m³, which were 1.13, 1.25, and 1.41 times the values of the suburban area during the period of March 2009 to February 2010. For the potential health risk analysis, the residents have been divided into four age categories namely, infants, children (1 year), children (8–10 years), and adults. The analysis took into account age-specific breathing rates, body weights for different age categories. The results showed that the potential health risks to respiratory disease for all age categories living in urban area were higher than those in suburban area.  相似文献