Soil n-alkane δD vs. altitude gradients along Mount Gongga, China

The altitude effect on the isotopic composition of precipitation and its application to paleoelevation reconstruction using authigenic or pedogenic minerals have been intensively studied. However, there are still no studies on variations in biomarker δD along altitude transects to investigate its potential as a paleoelevation indicator, although it has been observed that δD of higher plant lipid may record changes in precipitation δD (δD_p). Here, we present δD values of higher plant-derived C₂₇, C₂₉, and C₃₁n-alkanes from surface soil along the eastern slope of Mount Gongga, China with great changes in physical variables and vegetation over a range from 1000 to 4000 m above sea level. The weighted-mean δD values of these n-alkanes (δD_wax) show significant linear correlations with predicted δD_p values (R² = 0.76) with an apparent isotopic enrichment (ε_wax-p) of −137 ± 9‰, indicating that soil δD_wax values track overall δD_p variation along the entire altitudinal transect. Leaf δD_wax is also highly correlated with mountain altitude by a significant quadratic relationship (R² = 0.80). Evapotranspiration is found declining with altitude, potentially lowering δD_wax values at higher elevations. However, this evapotranspiration effect is believed to be largely compensated by the opposing effect of vegetation changes, resulting in less varied ε_wax-p values over the slope transect. This study therefore confirms the potential of using leaf δD_wax to infer paleoelevations, and more generally, to infer the δD of precipitation.     

粤西沿海一次赤潮事件的三维观测

From November 24 to 26, 2014, a red tide event occurred in the offshore water off the Hailing Island located at the western Guangdong coast. The red tide appeared as pink strips distributed within 3 km in the offshore water and extended for about 10 km along the shoreline. During the flood tide, the pink seawater rushed to the beach with breaking waves, forming foam strips on the beach. Guangdong Province Key Laboratory for Coastal Ocean Variation and Disaster Prediction Technologies, Guangdong Ocean University, emergently responded to the event and organized three-dimensional observations from the air, onboard and on beach. The preliminary analyses of the cruise data and water samples indicate that the event was induced by nontoxic Noctiluca scintillans, of which the concentration reaches as high as 4 200 cells/L near the surface and 2 600 cells/L at the bottom.     

Influence of sequential tropical cyclones on phytoplankton blooms in the northwestern South China Sea

Upper ocean responses to the passage of sequential tropical cyclones over the northwestern South China Sea(SCS) in 2011 were investigated using satellite remote sensing data,Argo reanalysis data,and an array of mooring data.We found that the sea surface low temperature region lasted for more than 38 days and two phytoplankton blooms occurred after the passage of sequential tropical cyclones.The upper ocean cooling reached 2-5℃ with a right-side bias was observed along the typhoon track to about 200 km.The maintenance of low temperature region and the two phytoplankton blooms were mainly driven by upwelling and near-inertial turbulence mixing induced by the sequential tropical cyclones.The first phytoplankton bloom appeared on the 7~(th) day after the passage of the three tropical cyclones,and the chlorophyll-a(chl-a) concentration increased by 226%,which may be mainly driven by typhoons induced upwelling.The second phytoplankton bloom occurred on the 30~(th) day,the chl-a concentration increased by290%.Further analysis suggested that only the typhoons with similar characteristics as Nesat and Nalgae can induce strong near-inertial oscillation(NIO).Strong turbulent mixing associated with the near-inertial baroclinic shear instability lasted for 26 days.The measured mean eddy diffusivity in the upper ocean was above 10~(-4) m~2/s after typhoon Nesat.Enhancement of the turbulent mixing in the upper ocean helped to transport nutrient-rich cold waters from the deep layer to the euphotic layer,and is a maj or mechanism for the long-term maintenance of low temperature region as well as the second phytoplankton bloom.     

2013年夏季琼东海域营养盐与叶绿素a的周日波动及其影响因素

基于2013年8月琼东海域两个连续站的观测资料,对比分析了近岸站位和陆架站位的营养盐和叶绿素a浓度周日变化特征及其影响因素。结果表明:在垂直分布上,近岸站位S1与陆架站位S2的温跃层减弱了营养盐的向上输运;在时间变化上,S1站底层硅酸盐、硝酸盐和磷酸盐浓度具有半日波动的特点,而S2站的营养盐则不具有周日波动的现象,这说明近岸站位的营养盐受到潮汐作用的影响更显著。S1站的叶绿素a分层不明显,夜间的低值可能体现浮游动物的摄食作用,S2站位的叶绿素a分层明显,夜间没体现浮游动物的摄食作用。总体上,琼东海域近岸站位S1和陆架区站位S2叶绿素a和营养盐周日波动都受到温跃层、潮汐、生物作用和光照的影响,但S1站受潮汐作用影响更显著,且S1站叶绿素a浓度还受到浮游动物摄食作用影响。由于叶绿素a和营养盐受到多种环境要素的影响,使得两者相关性不显著。     

西北太平洋楚科奇海沉积物-水界面营养盐输送通量估算

陆架区沉积物间隙水的营养盐再生是水体营养盐补充的重要途径之一。楚科奇海陆架区中部沉积物间隙水中的营养盐分布,是物理和生物扰动较弱状态下的沉积物-水界面的典型分布。本文对中国第4次北极科学考察采集的4个多管短柱沉积物样品及多管样站位的上层水样进行分析,得到沉积物间隙水、上覆水以及水柱中营养盐数据。结果表明,沉积物间隙水各营养盐浓度均先随沉积深度增加而呈指数快速升高,记为Ⅰ层;然后进入沉积物再矿化作用与营养盐移出速率相互抵消的稳定变化层,营养盐浓度在该阶段基本不变,记为Ⅱ层;最后是营养盐缓慢递减层,记为Ⅲ层,由于该层有机质降解作用耗尽氧气,NO-3和PO3-4被还原细菌利用而失去氧离子。通过双层模式和Fick第一扩散定律,计算得出楚科奇海沉积物-水界面硅酸盐、磷酸盐和硝酸盐的扩散通量分别为1.660mmol/(m2·d)(以Si计量)、0.008mmol/(m2·d)(以P计量)、0.117mmol/(m2·d)(以N计量)(以R06站为例)。四个调查站位沉积物中硅酸盐的扩散通量分别为3.101mmol/(m2·d)(以Si计量,CC1站)、1.660mmol/(m2·d)(以Si计量,R06站)、1.307mmol/(m2·d)(以Si计量,C07站)、0.243mmol/(m2·d)(以Si计量,S23站),含量呈现明显的纬度分布特征。沉积物间隙水N*的分布表明,楚科奇海沉积环境具有很强的反硝化过程,沉积物脱氮作用是硝酸盐一个重要的汇。     

Review on Researches of Legacy POPs and Emerging POPs in the Arctic Regions

The specific geographic location and natural conditions of the Arctic region play a significant role in the global climate change. As a result of perennial low temperature, simple ecological structure, and fragile ecosystem and weak stability in the Arctic, Persistent Organic Pollutants (POPs) accumulating from the region of middle and low latitudes may cause tremendous pressure in the arctic ecological environment. Therefore, the research of POPs in the Arctic region is not only conducive to more in-depth understanding of POPs distribution and transformation process in the global range, but to reasonably assess the harm of human activities on the arctic ecological environment. Thus, in the past 40 years, especially after nine new kinds of emerging organic contaminants being added to the list of Stockholm Convention in 2009, more and more scientific community and general public have pay attention to the research of POPs in the Arctic region. At present, the understanding of legacy POPs in the Arctic is limited, and the research of emerging POPs is in the initial stage. This paper aimed to summarize some conclusions and implications of the research, and focused on the occurrence level, historical evolution, bioaccumulation and source of POPs in atmosphere, waters, sediments and organisms in the Arctic region. Finally, the future changes and key scientific problems of POPs in the Arctic region were proposed.     

磨玻璃病灶影像检查技术应用对比的体模研究

目的:借助嵌有磨玻璃病灶的胸部体模研究X线摄影、计算机断层扫描(CT)和数字断层融合(DTS)3种检查技术在新型冠状病毒肺炎筛查中的应用价值.方法:将19枚与新型冠状病毒肺炎的典型影像表征相似的类椭圆形磨玻璃影磨玻璃病灶置入体模内各肺叶处,分别用低剂量CT扫描、DTS扫描和X线摄影方法检查,更换病灶位置后再次检查,对3...     

Nitrate δ15N and δ18O evidence for active biological transformation in the Changjiang Estuary and the adjacent East China Sea

The Changjiang Estuary has been considered as one of the most polluted estuaries in the world due to high nitrate (NO-3) input, especially in spring and summer. In this study, δ15N and δ18O of NO-3 , along with other chemical parameters in this area, were measured in spring to evaluate NO-3 biogeochemical processes. A simple two end-members mixing model was used to examine the relative contribution of the Changjiang River Diluted Water and marine water to NO-3 sources in the Changjiang Estuary and the adjacent East China Sea. The isotopic signals show that NO-3 behaved relatively and conservatively in Transect F and Transect P where assimilation was weak possibly due to vertical mixing, while active assimilation and weak nitrification occurred in Transect D. Spatial difference in assimilation was indicated by the～1:1 enrichment of δ15N and δ18O in the three transects, while spatial difference in nitrification was reflected by deviations of δ15 N and δ18O from assimilation line. Our results suggest that the input of the Changjiang River Diluted Water promoted NO-3 assimilation possibly by stratifying the water column which favored the phytoplankton growth.