Progress in research of hypoxia in estuaries and coastal areas in China

对长江、珠江等河口及其近海水域缺氧现象与影响因素进行研究,结果表明,主要分布于长江与珠江河口及其邻近海域的缺氧现象,夏季(6-8月)达到最盛,秋; 冬季消失;长江口的缺氧区域主要位于30.75°N~32°N,122.5°E~123.25°E附近海域,具有南北2个缺氧中心;珠江口缺氧程度相对较; 轻,缺氧区域主要在广州黄埔区河段至虎门水域和伶仃洋;辽河、钱塘江、海河等河口区域也时而出现零星的缺氧现象;水体缺氧受控于多项环境要素,物理层化作; 用是缺氧产生的最初诱因之一,陆源污染物的分解则是重要的耗氧负荷;各河口区特征各异,潮汐、洋流、营养盐、叶绿素a等要素对缺氧区的范围、程度和持续时; 间影响程度不一。In order to study hypoxia in the main estuaries and adjacent coastal; areas in China, we compared the hypoxia in the estuaries of the Yangtze; River, the Pearl River, and other rivers, and analyzed the factors. We; found that hypoxia mainly occurred in the estuaries of the Yangtze; River, the Pearl River, and the adjacent coastal areas; it had the most; significant increase in the summer (from June to August) and disappeared; in the autumn and winter. The hypoxia zone in the Yangtze River Estuary; was mainly located in the area with latitudes from 30.75°N to 32°N and; longitudes from 122.5°E to 123.25°E, and there were two hypoxia centers; in the south and north, respectively. The degree of hypoxia in the Pearl; River Estuary was relatively moderate, and hypoxia mainly occurred from; the Huangpu section to Humen waters in Guangzhou and in the Lingdingyang; Channel. In addition, hypoxia occasionally occurred in the estuaries of; the Liaohe River, Qiantang River, and Haihe River. We also found that; hypoxia was subjected to many environmental factors, of which the; stratification of water was one of the initial factors and the; decomposition of terrigenous pollutants was a major factor of oxygen; consumption. Tides, upwellings, nutrients, and chlorophyll-a had; different influences on the scale, degree, and duration of hypoxia, due; to the various characteristics of the estuaries

Duct Segmentation Method Based on Seed Region Growing Algorithm

目的:对CT片中的胆管进行分割。方法:采用图像分割技术中的种子区域增长法,首先,选取种子点,得到种子点所对应CT值和相邻26个点均值,然后以种子点所在位置为起点往其临近26点扩散。若其临近点CT值与种子点CT值差值在正负10个Hu或者均值满足相同要求则该点为同类点,依次类推,直到不再有同类点时算法结束。结果:自动分割的准确率>80%,计算误差 80%,computation error < 10%.Condusions:seed region growing method can be used to automatically segment bile duct in the film CT.国家自然科学基金项目资助(编号:61271336;61327001)~

Characters of magnetic susceptibility of surface sediments and their significance in the lower reach and estuary of Minjiang River

闽江是中国东南沿海最大的河流,具有落差大、水动力强等典型的山溪型河流特征.本研究对采自闽江流域的43个表层沉积物样品进行了磁学参数分析,结果显示,低频磁化率(χ_(lf))、高频磁化率(χ_(hf))分别为0.79×10~(-8)~24.97×10~(-8)、0.74×10~(-8)~24.80×10~(-8)m~3/kg,与长江、黄河相比低一个数量级;频率磁化率(χ_(fd))为0.06%~7.20%,大多小于5.00%,沉积物中超顺磁颗粒含量较低.χ_(lf)和χ_(fd)总体呈现从下游到河口增长的趋势,并在北港、南港、闽侯、大樟溪等人口密集区域受到不同程度的人为影响,分析表明研究区磁化率受控于源岩特征、水动力条件、沉积作用和人为活动等因素.在p<0.01时,χ_(lf)与Al2O3、Fe2O3、Na2O、Mg O、Ti O_2、Ca O等氧化物显著正相关,与Si O_2显著负相关,说明其受控于源岩成分.此外,χ_(lf)与Si/Al值显著负相关,与化学风化指数(CIA)正相关,表明磁化率可以作为现代沉积物风化程度的替代指标.χ_(lf)与溶解态As含量、χ_(fd)与溶解态Cd含量均在p<0.05时相关,表明磁学参数可作为指示研究区水体的As和Cd污染的参考指标.Minjiang River is the largest river in South-east coastal area of China and it is,as a mountain river,characteristic of large elevation gradient and strong hydrodynamics. Low frequency magnetic susceptibility( χ_(lf)),high frequency magnetic susceptibility( χ_(hf)) and frequency magnetic susceptibility( χ_(fd)) of 51 surface sediment samples collected from the Minjiang River were measured with Bartington MS2. The results shows that χ_(lf)ranges from 0. 79× 10~(-8)to 24. 97 × 10~(-8)m~3·kg~(-1),which is an order less than those of the Changjiang River and Huanghe River sediment. Most of the value of χ_(fd)are lower than 5. 0%,indicating that the content of superparamagetism particles in surface sediment samples are low. In general,the values of χ_(lf)and χ_(fd)progressively increase from low reach to estuary,with significant influence of anthropogenic impact in densely populated areas of the North and the South port,Minhou Country and Dazhangxi Brook. It suggests that magnetic susceptibility is controlled by the source rock differences,hydrodynamics,sedimentation and anthropogenic impact. Magnetic susceptibility can be taken as indicators of source rock differences and weathering intensity,considering its remarkable correlation with major element abundance and ratios of Si / Al( p < 0. 01). χ_(lf)and χ_(fd)are also positively correlated with As and Cd abundance in water,which it means that χ_(lf)and χ_(fd)could be used as a simple proxy of As and Cd contamination in water.国家自然科学基金资助项目(41076122,40976037,41376050