Measuring natural phytoplankton fluorescence and biomass: a case study of algal bloom in the Pearl River estuary

A moored optical buoy was deployed in the Pearl River estuarine waters for a 15-day period. A four-day algal bloom event occurred during this study period. Both chlorophyll a concentration and algal cell density (a proxy for biomass) changed dramatically before and after the event. The chlorophyll concentration at a 2.3 m depth rose from 5.15 mg/m⁻³ at 15:00 h on August 19 to 23.62 mg/m⁻³ at 9:00 h on August 21, and then decreased to 3.24 mg/m⁻³ at 15:00 h on August 24. The corresponding cell density ranged from 1.57 × 10⁵ to 1.76 × 10⁶ cells/L. We used normalized fluorescence line height (NFLH) and normalized fluorescence intensity (NFI) in order to determine fluorescence activity. Combined with the in situ sampling dataset, we were able to correlate natural fluorescence (NFLH and NFI) with chlorophyll a concentrations, and found correlation coefficients of 0.72 and 0.75, respectively. We also found correlations between natural fluorescence and cell density, with correlation coefficients of 0.71 and 0.65, respectively. These results indicate that applying continuous time series of natural fluorescence can reflect changes in biomass. This technique will prove extremely useful for in situ and real-time observations using an optical buoy. Although there are still problems to solve in the real-time observation of natural fluorescence in algal bloom events, we discuss the primary factors affecting fluorescence signals and suggest possible methods for mitigating these issues.     

Comprehensive assessment of heavy metal contamination in sediment of the Pearl River Estuary and adjacent shelf

Total metal concentrations (Cr, Ni, Cu, Zn, and Pb), acid volatile sulfide and simultaneously extracted metals (AVS-SEM), and heavy metal fractionation were used to assess the heavy metals contamination status and ecological risk in the sediments of the Pearl River Estuary (PRE) and adjacent shelf. Elevated concentrations at estuarine sites and lower concentrations at adjacent shelf sites are observed, especially for Cu and Zn. Within the PRE, the concentration of heavy metals in the western shore was mostly higher than that in the middle shore. The metals from anthropogenic sources mainly occur in the labile fraction and may be taken up by organisms as the environmental parameters change. A combination of total metal concentrations, metal contamination index and sequential extraction analysis is necessary to get the comprehensive information on the baseline, anthropogenic discharge and bioavailability of heavy metals.     

基于震源机制解反演应力场的一种改进方法

本文发展了基于震源机制解反演二维或三维背景应力场方位和主应力差比值R的一种可靠的、高精度的方法。所使用的震源机制解剔除了可能受到局部应力场的强烈影响、不能反映大尺度背景构造应力场信息的事件。去丛集后的数据利用k均值算法分为若干包含最少地震个数N_min到2N_min的组。人工实验测试表明,当R≈0.5时,N_min≈30才能保证不同应力体系包含不同噪声水平的情况下得到稳定的结果;当R接近于0或1时,则需要N_min≈45。另外的一个实验比较了两种从震源机制解中选择断层面方法的表现:(a)选择震源机制的滑动矢量和应力张量给出的剪应力矢量之间角度最小的那个节面;(b)给定应力场和摩擦系数,选择失稳系数最大的节面,它更接近最优断层。结果发现,失稳准则在所有试验的不同应力体系、主应力差比值、噪声水平的情况下得到的结果更准确。本文改进的方法将失稳准则迭代选择断层面和加入阻尼迭代反演各震源机制分组的应力场相结合。加入阻尼反演得到的各分区应力场结果中融合了相邻区域的应力场信息,能够得到不受分区影响的高精度结果。本文方法的...     

http://www.sciencedirect.com/science/article/pii/S1674987113000832

The Sinus Iridum region, the first choice for China＇s＂Lunar Exploration Project＂is located at the center of the lunar LQ-4 area and is the site of Chang＇e-3 （CE-3）＇s soft landing. To make the scientific exploration of Chang＇e-3 more targeted and scientific, and to obtain a better macro-level understanding of the geotectonic environment of the Sinus Iridum region, the tectonic elements in LQ-4 region have been studied and the typical structures were analyzed statistically using data from CE-1, Clementine, LRO and Lunar Prospector missions. Also, the mineral components and periods of mare basalt activities in the study area have been ascertained. The present study divides the tectonic units and establishes the major tectonic events and sequence of evolution in the study area based on morphology, mineral constituents, and tectonic element distribution.     

Historical trends of organic pollutants in sediment cores from Hong Kong

Recent studies have indicated the occurrence of a wide range of trace organic contaminants, including polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs) in the Hong Kong environment. These contaminants are potentially harmful to ecological systems, particularly in coastal areas. In this study, two sediment cores (4m) were collected from southern waters of Hong Kong in 2004 to study the historical trends, distribution patterns, and potential sources of trace organic contaminants. DDTs (p,p'-DDT, o,p'-DDT, p,p'-DDD, o,p'-DDD and p,p'-DDE), hexachlorohexanes (HCHs) (alpha and gamma), hexachlorobenzene (HCB), and PCBs were detected in the samples, whereas other target compounds were all below detection limits. Many OCPs have not been produced or used for many years due to toxicological or environmental concerns and PCB use is prohibited in Hong Kong. However, some compounds were still detectable in recent years, and were found to be widely distributed in the environment, likely because of pollutant inputs from the highly industrialized Pearl River Delta region. These results provide important information on current and historical contamination in Hong Kong, and help to reconstruct the pollution history of these trace organic pollutants in Hong Kong coastal waters.     

On Verification of the New Criterion of Adiabaticity by Numerical Simulation of Acoustic Propagation through the Polar Front

To assess the adiabaticity of acoustic propagation in the ocean is very important for acoustic field calculation(forward problem) and tomographic retrieving (inverse problem). A new criterion of adiabaticity is proposed recently (Shang et al., 2001). In this paper, numerical simulation has been conducted for acoustic propagation through the Polar Front to verify the new criterion. Numerical results on the f (frequency) -rn (mode number) plan demonstrate that the new criterion works very well for this extremely non-gradual ocean structure.     

降雨影响下基坑开挖施工对邻近基桩变形响应分析

目前关于基坑开挖对邻近基桩变形响应的简化理论解研究,还较少考虑基坑开挖中支护作用的影响,尤其是没有考虑降雨环境带来的土工影响。基于一种适用于不同降雨工况的分层假定Green-Ampt模型来模拟降雨入渗过程,采用两阶段分析方法,研究了降雨影响下基坑开挖与邻近基桩相互作用的问题。首先,考虑基坑开挖土体卸荷、围护结构及支撑结构的影响,采用Mindlin基本解,分析降雨影响下基坑开挖施工导致邻近基桩位置的土体附加应力;然后,基于Pasternak双参数地基模型,探讨基桩与土体之间的相互作用,求得降雨影响下单桩和群桩随降雨历时变化的水平变形响应。通过工程监测数据与理论计算结果进行对比,获得了较好的一致性。此外,也针对降雨敏感参数（降雨强度、饱和渗透系数、初始含水率、基质吸力）与基桩敏感参数（边界条件、支撑刚度、桩径、开挖深度、桩与基坑间距）进行了影响因素分析。分析结果表明,所提出的理论方法可较好地反映降雨影响下基坑开挖施工对邻近基桩的变形响应;降雨对邻近基桩变形影响显著,降雨参数敏感程度依次为：降雨强度>初始含水率>饱和渗透系数>基质吸力;随着降雨历时的增长,湿润层发展深度不断...     

Transition-Zone Mineral Assemblages in Peridotite Massifs, Tibet: Implications for Collision-zone Dynamics and Orogenic Peridotites

<正>Diamonds have been reported from Tibetan"ophiolites"for≥30 years,but have been widely dismissed as contaminants,because their unusual morphology and light C(δ~(13)C=-18 to–27)are unlike those of kimberlitic diamonds.However,the diamonds have now been found in situ in both the chromitites and the peridotites of     

Diamonds and Highly Reduced Minerals from Chromitite of the Ray-Iz Ophiolite of the Polar Urals: Deep Origin of Podiform Chromitites and Ophiolitic Diamonds

<正>The Uralide orogenic belt is a major early Paleozoic suture zone extending more than 3000 km in a N-S direction,and geographically divides Europe from Asia(Chemenda et al.,1997).Ophiolites,podiform chromitites and high pressure metamorphic rocks are well developed in the orogenic belt(Leech and Ernst,2000).The Ray-Iz     

Jack Hills锆石的安山质源区支持板块构造始于冥古代北大核心CSCD

地球最老的地壳组成和构造属性是地球科学研究中两个最基本的问题,但是由于缺乏合适年龄的岩石,难以进行约束。很多研究主要集中于西澳Jack Hills变质沉积岩中4.4~4.3 Ga的碎屑锆石,但是对其原岩性质的认识依然缺乏共识。对其原岩成分的推断主要基于锆石的Hf同位素组成,研究者普遍认为这些碎屑锆石来源于火成岩源区。