南海北部珠江口近海地质风险

南海是我国海洋灾害地质条件最为复杂、潜在地质灾害危险性最大的海区。南海北部尤其是珠江口地区的地理位置尤为重要，是我国经济开发的门户地区。本文使用GeoSwath Plus多波束系统对南海北部珠江口外海面进行了水深测量，通过系统配套软件对多波束数据的精细处理，得出高密度的水深数据以及旁扫声纳数据，经过对数据以及相关成图图件的分析，利用对灾害地貌的加权统计模型对该地区的地质灾害进行定量评定。目前国内使用的多波束型号较多，根据其频率的不同可分为浅水、中水、深水多波束系统。根据波束形成原理（数控法和相干法）的不同可分为传统多波束和具有相干特点的多波束系统，这两种多波束系统由于其原理的差异，在各种性能表现上都存在不同之处，本文从原理及其各种不同的性能表现上对该多波束系统与传统多波束系统进行了详细对比论证。 在对调查区区域地质、第四纪地质充分调研的基础上，通过对调查区地形的概况和相关影响因素的论述（诸如水动力条件、构造特征等），结合水深图、地形图和多条地形剖面的分析，得出该海域在工程施工方面海底地形上的影响因素。 通过对本区所发现的地貌类型，结合海洋地质灾害类型分析，通过对相关地质灾害类型的统计说明，得出该地区地质灾害的影响因素及其潜在危害程度。通过提取南海北部的灾害地质因素和对调查区灾害地质环境的充分研究，以灾害地质因素为评价因子，采用加权统计模型对研究区的海底稳定性进行分区定量评价。利用评价结果，确定了调查区基于地貌类型区划的海底稳定性级别。

长江口附近海域三维悬浮泥沙的数值模拟研究

本文构建了长江口外海域三维悬浮泥沙输运数值模型，其中水动力模型中主要考虑了潮汐潮流、出入径流及风浪等作用，输运模型中考虑了粘性泥沙的絮凝、粘性和非粘性泥沙的再悬浮等过程。并与2006年8月份在长江口外海域获得的定点连续站测流资料及悬浮泥沙的观测资料进行了比较。为了进一步提高模式结果的精确性，采用将动力模式与实测资料相结合的趋近同化方法，在连续方程和泥沙输运方程中分别增加一个松弛项，将模拟结果向已有实测调和常数的控制点推算潮高值和悬沙浓度观测值趋近。数值实验证明，将验潮站资料和泥沙观测资料引入到数值模式中去，可以有效的改善模式的模拟结果。将该方法运用到长江口外附近海域的悬浮泥沙数值模拟当中，并泥沙输运水平紊动扩散系数也做了合理的修改，其模拟结果也得到了不错的改进，所得结果适用于计算长江口外海域的水动力和泥沙输运情况。 可以大体得到泥沙在长江口内外分布规律：悬浮泥沙浓度自近岸向外海降低,长江口外123°E以东浓度一般不超过10mg/l，终年悬浮泥沙高值区见于河口区,一般超过300mg/l，以长江口、杭州湾悬浮泥沙浓度最高。悬浮泥沙浓度垂向剖面的计算值与观测数据符合良好。 在潮周期中，悬浮泥沙浓度的变化与

长江口水文、泥沙过程与圆桩冲刷的数值模拟

本文主要利用ECOMSED模式对长江口及邻近海域的水文、泥沙过程进行三维数值模拟，并结合实测资料分析其水动力、泥沙输运、底床冲淤等特征；然后利用欧拉二相流模型模拟小尺度条件下长江口底床上圆桩周围的水流和泥沙冲刷、输运规律。 通过资料分析和ECOMSED数值模拟结果比较，我们得出：长江口口门内为非正规半日潮流区，潮流运动形式多为往复流，落潮流占优。落潮流速大于涨潮流速，流速垂向分布从表层到底层递减。悬沙浓度与流速关系密切，一般来说，流速越大，悬沙浓度越高；一个潮周期过程中会出现两次、三次或四次泥沙再悬浮，分别是涨急、落急、涨转落、落转涨时刻；盐水楔结构对粘性与非粘性悬沙浓度的分布起决定性作用，转流时泥沙再悬浮主要是由于这时会出现盐水楔，并形成垂向环流，使床面大量未被固结的泥沙再悬浮，形成峰值。悬浮泥沙垂向分布可分为垂线型，斜线型，抛物线型和L型。流场和底床冲淤变化与水深关系密切：深水区，流速较大，底床冲淤变化也较大。其中，受径流影响区表现为淤积，受潮流影响区表现为冲刷；浅水区基本表现为淤积。 从模式运行结果和实测资料比较可以看出，该模型可以较好的模拟长江口水流、悬浮泥沙分布与变化；能够再现在径流入海口处，盐水楔结构及其诱生的垂向环流从形成到发展，又到消失的完整过程；也能够展示底床的冲淤变化。对于我们模拟长江口背景流场，了解该区域内水动力变化、悬浮泥沙输运、底床冲淤等有重要意义。 在欧拉二相流模型对长江口底床上圆桩周围的水流和局部冲刷数值模拟过程中，我们不仅考虑水流和泥沙之间的作用，还引入泥沙颗粒之间的相互影响。模拟结果较合理的展示了圆桩周围的流场类型和底床冲刷变化：在圆桩前方，流速减小并形成垂向涡旋，从而产生局部冲刷；在圆桩两侧，水流加速，挟带上游泥沙向下输送，并在内侧堆积；而在圆桩后面，存在流速分离区。在该分离区内流速很小，并且当流速较大时，会产生回流，形成两个对称的漩涡。流速越大，圆桩前由垂向涡旋引起的局部冲刷就越明显；而当底床泥沙粒径变小时，泥沙临界起动流速变小，底床也更容易被冲刷。悬浮泥沙浓度分布受流场的影响，并且当粒径小而流速大时，能悬浮到更高的深度。

长江口邻近海域缺氧区营养盐及痕量金属的生物地球化学过程研究

长江口邻近海域夏季底层水体存在世界上面积最大的缺氧带。这为研究河口区氧化还原敏感元素的生物地球化学过程提供了天然的实验场所。为了理解长江河口缺氧带存在的生物地球化学过程，本文以长江口邻近海域缺氧带上覆水体、沉积物及间隙水为研究对象，并对其营养盐及重金属进行研究，目的在于揭示长江口邻近海域缺氧带可能存在的生物地球化学过程，为理解长江河口区的物质循环提供科学证据。通过研究得出如下结论：（1）在水体中盐度是影响营养盐分布的主要因素，在高浊度带存在营养盐释放的现象；（2）底层水存在两种显著不同的生物地球化学过程：当盐度<33 PSU时，营养盐与AOU之间为负相关，影响底层海水营养盐分布的主要因素可能为流场；而当盐度>33 PSU时，营养盐与AOU之间存在正相关，影响营养盐分布的主要因素为颗粒有机质的矿化；（3）溶解态痕量金属存在保守型（Mo、U、Ni）和混合型(Fe、Mn、Cu、Pb、Zn)的分布规律，盐度、浮游生物及溶解氧都是影响溶解态痕量金属分布的重要因素；剔除浊度大于20 NTU的数据，分配系数与浊度为显著正相关；（4）间隙水Fe、Mn剖面表明，长江河口表层沉积物存在剧烈的Fe、Mn还原现象；成岩模型模拟结果显示间隙水Mn的模拟剖面与实际观测剖面吻合较好。间隙水U剖面显示，控制U分布的主要因素与Fe有关，但是其它因素如有机质含量对U、Mo的分布也有影响；（5）间隙水营养盐剖面显示近岸与远岸存在两种不同的生物地球化学过程：远岸海域，间隙水营养盐部面主要受早期成岩的控制；而在近岸海域其它过程如氨化及吸附可能是控制间隙水氮剖面分布的主要因素；模拟剖面与NH4+的实测剖面趋于一致，但是同时暗示表层沉积物受到生物扰动；通量计算结果显示，Si、N、P分别占浮游生物每日所需要营养盐数量的15%、10%及0.1%；（6）对痕量金属的黄铁矿化程度进行了分析，发现长江河口痕量金属的黄铁矿化程度异常低，黄铁矿不是影响痕量金属分布的主要因素；导致低黄铁矿化度的原因与长江河口高沉积速率、贫硫、低有机质有关。

夏季长江口外海区域上升流现象的数值研究

中国沿岸海域是上升流的多发区. 渤、黄海域，东海陆架区，台湾海峡，以及南海沿岸都存在众多的上升流区. 上升流有利于穿越陆架的物质输运，可以把下层海水中的营养物质带至真光层，促进浮游植物生长，为赤潮爆发提供有利条件. 长江口外和浙江沿岸上升流区连续几年爆发大规模赤潮，该海域已成为我国近海赤潮严重的区域之一. 同时上升流也是该海域海洋渔场形成的重要动力因子. 因此，对长江口外及浙江沿岸上升流的研究具有重要的意义. 本文基于Blumberg等（1996）的ECOMSED模式，对长江口外海区域夏季的上升流现象进行了数值模拟研究. 为了提高对长江口外海区域上升流模拟的准确性和可靠性，模式综合考虑了径流，风应力，环流，热通量和M2，S2，K1，O1四个主要分潮的作用. 本文首先进行控制实验，综合考虑各种动力因子，模拟长江口外南部冷水区的上升流现象，再单独考虑各个动力因子做数值实验，并对各种数值实验结果进行分析对比来研究产生该区域上升流现象的主要原因. 我们设计了3个数值实验：不考虑风应力和热通量、不考虑环流、仅考虑温盐和潮因子. 方便起见，将综合考虑各种动力因子的数值模拟称作控制实验. 各种实验结果的分析表明，长江口外水下河谷的南边（杭州湾口门中心东侧），上升流主要是由向北流动的台湾暖流通过底Ekman效应和陆坡的抬升共同作用产生的. 夏季偏南风对长江口外水下河谷西侧上升流的产生有一定影响，但作用不大. 此外，潮汐潮流对上升流的产生也起着一定的作用，但在本文关注的上升流区潮作用影响不大.

海洋微藻产生溶解有机物及东海溶解有机物三维荧光特征研究

本文通过胶州湾围隔实验、微藻培养实验研究了海洋微藻产生溶解有机物的三维荧光特性，并初步利用经验正交函数对三维荧光光谱图进行了主成分分析，通过东海取样研究了东海荧光溶解有机物的时空分布特征，并对荧光溶解有机物的来源进行了分析。得到了一些初步结论： 胶州湾围隔实验中不同营养盐培养结果表明浮游植物可产生类蛋白和类腐殖质荧光，类蛋白荧光峰由类酪氨酸(tyrosine-like)荧光峰和类色氨酸(tryptophan-like)荧光峰组成，主要位置为Exmax/Emmax=270nm/290~310nm，Exmax/Emmax= 270~290/320~350的荧光峰强度比较弱；在Exmax/Emmax=250~260/380~480nm(A峰)、Exmax/Emmax=310~320/380~420nm(C峰)和Exmax/Emmax=330~350/420~480nm(M峰)位置均出现零散的类腐殖质荧光峰，其中以A峰为主。类酪氨酸荧光强度明显高于类腐殖质荧光强度。浮游植物量降低时，类酪氨酸荧光强度与叶绿素a浓度呈明显的负相关。硅藻和甲藻产生的类酪氨酸和类色氨酸荧光强度之间具有较好的相关性，两者来源相似, 并且甲藻与硅藻相比能够产生更多的类蛋白荧光物质。不同环境下类腐殖质混合物的组分比例不同，甲藻生长环境下相对于硅藻具有较低的A:C比值。 在实验室培养中肋骨条藻（Skeletonema costatum）、塔玛亚历山大藻（Alexandrium tamarense）、微小亚历山大藻（Alexandrium mimutum）、锥状斯氏藻（Scrippsiella trochoidea）、东海原甲藻（Prorocentrum donghaiense）及海洋原甲藻（Prorocentrum micans）的实验结果表明，微藻在生长过程中产生出荧光溶解有机物，中肋骨条藻为代表的硅藻主要产生类腐殖质荧光物质，而甲藻在指数增长期主要产生类蛋白荧光物质。进入消亡期后类蛋白荧光和类腐殖质荧光强度迅速增大，原因可能是衰老、死亡藻细胞的破碎释放出大量的荧光有机物质所致，此外还有细菌对非荧光有机物进一步降解。塔玛亚历山大藻、微小亚历山大藻、东海原甲藻及海洋原甲藻的类蛋白荧光强度在消亡后期由于细菌降解或光降解等因素而降低。同属微藻产生的荧光物质相似，例如塔玛亚历山大藻与微小亚历山藻、东海原甲藻与海洋原甲藻，但具体荧光峰位置有所不同。利用经验正交函数能够对三维荧光光谱谱图进行主成份分析。 在利用三维荧光光谱法研究长江口海域台风前后不同站位荧光溶解有机物荧光特性及分布特征的结果表明，长江口海区主要的荧光溶解有机物荧光峰为T峰、S峰和A峰。风前和风后的类色氨酸分别来源于相似物质。风前，在表层浮游植物能够产生类蛋白荧光物质，而底层类蛋白荧光物质不受浮游植物的影响，长江冲淡水能够带来部分类蛋白荧光物质；表层的类腐殖质不受浮游植物的影响，而底层的浮游植物在降解过程中能够产生一部分类腐殖质，并且长江冲淡水对表层和底层的类腐殖质来源均有很大贡献。风后，表层的类色氨酸与叶绿素a浓度不呈相关性，而底层却呈正相关，另外表层和底层的类色氨酸均受到长江冲淡水的影响；表层和底层的类腐殖质与叶绿素a均没有相关性，但受陆源影响显著，长江冲淡水能带来类腐殖质。

长江口海域氮的同位素特征及其环境意义

本论文以稳定氮同位素（δ15N）技术为基础，对长江口海域氮的同位素特征及其环境意义进行了研究。确立了一套完整的水体中氮的稳定同位素分析预处理方法，并运用该方法对2006年长江干流以及长江口海域表层水体中的溶解态硝酸盐和悬浮颗粒物的δ15N特征进行分析，根据不同季节、不同区域内其δ15N值的变化研究水体中氮的迁移、转化等生物地球化学过程，揭示其环境行为，从而对该海域的氮循环机制进行探索。主要结果如下： 稳定氮同位素的分析准确与否，预处理过程是关键。不同形态、不同水体中氮的预处理方法不同。本文以传统的蒸馏法为基础，对适合海水中溶解态硝酸盐的氮同位素分析预处理方法进行研究并改进，并进行了不同实验条件的验证，效果较好。此外，对淡水体系中溶解态硝酸盐的氮同位素分析预处理方法以及悬浮颗粒物的氮同位素分析方法也进行了研究，确立了一套完整的水体中氮的稳定同位素分析方法，对δ15N技术在河口氮循环研究中的广泛应用提供了基础。 依据上述方法，对2006年2、5、8、11月份长江口海域表层水体中的溶解态硝酸盐δ15N值（δ15N-NO3-）进行分析。研究发现，δ15N-NO3-分布范围在0.4‰到6.5‰之间，平均为3.5‰，具有明显的时空分布特点，在不同季节不同区域内所受的物理、生物地球化学作用不同。口门内，δ15N-NO3-的季节变化主要受长江径流输入影响，来源单一。最大浑浊带，δ15N-NO3-的分布规律不明显，保守混合行为较差，说明该区域的影响作用复杂，不同季节水体中发生的生物地球化学作用存在差异。外海区，δ15N-NO3-的季节变化明显，春季>秋季>夏季>冬季，与生物对硝酸盐的吸收程度变化相一致，反映了生物作用在该区域的影响显著。 同样在2006年2、5、8、11月份本文对长江口海域表层水体中悬浮颗粒物的δ15N（δ15Np）组成进行了研究。δ15Np值分布在0.6-8.2‰之间，同样具有明显的时空分布特点，其变化趋势与陆源输入和水体中氮的生物地球化学过程有关。口门内，表层水体中δ15Np的变化主要受长江径流的陆源输入影响，生物地球化学作用影响较弱；最大浑浊带，水体中的悬浮颗粒有机氮受微生物的降解活动影响明显，各季节均存在不同程度的颗粒物分解作用；外海区，陆源输入减弱，悬浮颗粒物的δ15Np值主要受微藻的同化吸收作用以及一定程度的颗粒物分解作用影响。 长江口海域水体中溶解态硝酸盐和悬浮颗粒有机氮之间存在重要的相互转化作用，二者之间δ15N的变化及其相互关系反映了一定的生物地球化学变化和环境信息。总体而言，长江口海域表层水体中δ15N-NO3-的分布水平较δ15Np略低，二者之间的分馏ε总体偏正。其中，δ15N-NO3-与δ15Np的最低值均出现在2月份，说明该季节水体溶解态硝酸盐和悬浮颗粒物都可能受到一致的外源输入影响，其内部生物地球化学作用较弱。5月份和11月份水体中的δ15N-NO3-值和δ15Np值均各自水平相近，说明在这两个季节溶解态硝酸盐和悬浮颗粒物都可能受到程度相近的外源输入或生物吸收作用的影响，分馏ε偏负程度较大。8月份δ15N-NO3-值较低而δ15Np值较高，分馏ε在四个季节中最大，可能是该季节程度较大的颗粒物分解作用影响所致。 2006年长江干流表层水体中溶解态硝酸盐及悬浮颗粒物的δ15N组成也具有明显的时空分布特点，二者季节变化规律相近，丰水期（5、8月份）δ15N值较高，而枯水期（2、11月份）较低。δ15N-NO3-与δ15Np之间呈现明显的正向相关关系，其空间分布趋势相同，自长江上游至下游δ15N值逐渐升高，说明二者均受到相似的氮来源影响；长江上游氮的来源均以大气沉降和农业源（无机化肥和土壤有机氮）为主，而中、下游水体氮的来源则都偏重于工业及生活排污的贡献，随着人类活动程度以及工业化、城市化程度的升高，硝酸盐及悬浮颗粒有机氮的来源发生变化，其δ15N值相应增加。

Relationships between nitrogen and phosphorus forms and ratios and the development of dinoflagellate blooms in the East China Sea

During late spring and early summer of 2005, large-scale (> 15 000 km(2)), mixed dinoflagellate blooms developed along the the coast of the East China Sea. Karenia mikimotoi was the dominant harmful algal bloom species in the first stage of the bloom (late May) and was succeeded by Prorocentrum donghaiense approximately 2 wk later. Samples were collected from different stations along both north-south and west-east transects, from the Changjiang River estuary to the south Zhejiang coast, during 3 cruises of the Chinese Ecology and Oceanography of Harmful Algal Blooms Program, before and during the bloom progression. Nitrogen isotope tracer techniques were used to measure rates of NO3-, NH4+, urea, and glycine uptake during the blooms. High inorganic nitrogen (N), but low phosphorus (P) loading from the Changjiang River led to high dissolved inorganic N:dissolved inorganic P ratios in the sampling area and indicate the development of P limitation. The rates of N-15-uptake experiments enriched with PO43- were enhanced compared to unamended samples, suggesting P limitation of the N-uptake rates. The bloom progression was related to the change in availability of both organic and inorganic N and P. Reduced N forms, especially NH4+, were preferentially taken up during the blooms, but different bloom species had different rates of uptake of organic N substrates. K mikimotoi had higher rates of urea uptake, while P. donghaiense had higher rates of glycine uptake. Changes in the availability of reduced N and the ratios of N:P in inorganic and organic forms were suggested to be important in the bloom succession. Nutrient ratios and specific uptake rates of urea were similar when compared to analogous blooms on the West Florida Shelf.

Estuarine nutrient loading affects phytoplankton growth and microzooplankton grazing at two contrasting sites in Hong Kong coastal waters

To investigate the effects of enhanced nutrient loading in estuarine waters on phytoplankton growth and microzooplankton grazing, we conducted monthly dilution experiments at 2 stations in Hong Kong coastal waters with contrasting trophic conditions. The western estuarine station (WE) near the Pearl River estuary is strongly influenced by freshwater discharge, while the eastern oceanic station (EO) is mostly affected by the South China Sea. Growth rates of phytoplankton were often limited by nutrients at EO, while nutrient limitation of phytoplankton growth seldom Occurred at WE due to the high level of nutrients delivered by the Pearl River, especially in the summer rainy season. Higher chlorophyll a, microzooplankton biomass, phytoplankton growth and microzooplankton grazing rates were found at WE than at EO. However, the increase in chlorophyll greatly exceeded the increase in phytoplankton growth rate, reflecting different response relationships to nutrient availability. Strong seasonality was observed at both stations, with temperature being an important factor affecting both phytoplankton growth and microzooplankton grazing rates. Picophytoplankton, especially Synechococcus, also exhibited great seasonality at EO, with summer abundances being 2 or 3 orders of magnitude higher than those during winter, Our results confirm that in eutrophic coastal environments, microzooplankton grazing is a dominant loss pathway for phytoplankton, accounting for the utilization of >50%, of primary production on average.

Pretreatment Method for Nitrogen Isotopic Analysis of Nitrate in Seawater

A suitable method for the pretreutment of dissolved nitrate samples in seawaters for nitrogen isotopic analysis was established. First, the seawater samples were processed by removing nitrite and amonium. Then Devard's alloy was added in sample for conversion of dissolved nitrate to ammonium. The sample was distilled, and then the ammonium condensate was collected with zeolite. after distillation, the collected condensate was filtered and prepared for determining nitropic values. Some tests of the method were conducted. The distillation condition, the influence of salinity on nitrogen isotopic analysis, absorption of ammonium onto zeolite and an improved method on a large volume of seawater were discussed in this study. The results showed that the distillation step had an average recovery of (104.9 +/- 4.2) % (n = 6) when distillating every 300 mL aliquot of the sample under a strong alkaline condition with 0.5 g devard's alloy and a distillation time of 30 min. The nitrogen isotopic fractionation decreased markedly when salinity was increased from 0% to 0.5%; further increase(1% - 3.5%) showed little effect. The adsorption rate of ammonium onto zeolite had a high yield of (95.96 +/- 1.08) % (n = 6) in average. An improved collection method was used to process a large volume of seawater with several distillations, and had good effect on analysis. The method had been applied to analyze water samples collected from Changjiang estuary. The analytical results indicate that the method is suitable for delta N-15 analysis of dissolved nitrate in seawaters. The present method could provide valuable information about the source and cycle mechanism of dissolved nitrogen in estuary waters.

Nutrients in the Changjiang River

N, P and SiO3-Si in the Changjiang mainstream and its major tributaries and lakes were investigated in the dry season from November to December, 1997, and in the flood season in August and October, 1998. An even distribution of SiO3-Si was found along the Changjiang River. However, the concentrations of total nitrogen, total dissolved nitrogen, dissolved inorganic nitrogen, nitrate and total phosphorus, total particulate phosphorus increased notably in the upper reaches, which reflected an increasing impact from human activities. Those concentrations in the middle and lower reaches of the Changjiang River were relatively constant. Dissolved N was the major form of N and the particulate P was the major form of P in the Changjiang River. The molar ratio of dissolved N to dissolved P was extremely high (192.5-317.5), while that of the particulate form was low (5.6-37.7). High N/P ratio reflected a significant input of anthropogenic N such as N from precipitation and N lost from water and soil etc. Dissolved N and P was in a quasi-equilibrium state in the process from precipitate to the river. In the turbid river water, light limitation, rather than P limitation, seemed more likely to be a controlling factor for the growth of phytoplankton. A positive linear correlationship between the concentration of dissolved N and the river's runoff was found, mainly in the upper reaches, which was related to the non-point sources of N. Over the past decades, N concentration has greatly increased, but the change of P concentration was not as significant as N. The nutrient fluxes of the Changjiang mainstream and tributaries were estimated, and the result showed that the nutrient fluxes were mainly controlled by the runoff, of which more than a half came from the tributaries. These investigations carried out before water storage of the Three Gorges Dam will supply a scientific base for studying the influences of the Three Gorges Dam on the ecology and environment of the Changjiang River and its estuary.

Persistent organic pollutant residues in the sediments and mollusks from the Bohai Sea coastal areas, North China: An overview

The Bohai Sea costal area is one of the most developed zones of China and the sewage water from populous and developed cities, including Beijing, Tianjin. Qinhuangdao and Dalian is discharged into the Bohai Sea. Additionally, its semi-enclosed characteristic restricts water exchange, which leads to high accumulation of pollutants in the environment. This overview presents the residues of 6 classes of Persistent Organic Pollutants (POPs). including PAHs, DDTs. HCHs, PCBs and PCDD/Fs. in the sediments and mollusks of the Bohai Sea through analyzing previous literatures. In the sediments. the highest PAH concentrations were detected in the vicinities of Qinhuangdao, while the northeast corner of the Bohai Bay possessed the highest levels of DDTs and PCBs. The investigations on HCHs and PCDD/Fs distributions on the whole sea scale have not been reported. In mollusks, PAH concentrations were in the same order of magnitude in the whole Bohai Sea, so were DDTs. HCHs and PCBs, while the outlier maximum values of PCDDs and PCDFs occurred in Yingkou. In general, the POPs residues in mollusks collected from Shandong Province were higher than the other areas. The compositions of DDTs, HCHs and PCBs in sediments indicated their recent usage. By comparing POP concentrations in sediments with the recommended criterions, it was shown that some individual PAH compounds occasionally associated with adverse biological effects in the vicinities of the Liaodong Bay and Qinhuangdao, and the Liaohe River Estuary were heavily contaminated with DDTs, but PCBs were all below the thresholds. In order to reveal the transference and transformation of POPs in the environment, further studies concerning with their behavior, fate and bioaccumulation in the different trophic levels should be programmed. Moreover, laws and regulations should be enforced to ban the illegal usage of POPs-containing pesticides to guarantee health of the environment and human. (C) 2008 Elsevier Ltd. All rights reserved.

Stable carbon and nitrogen isotopic compositions of high molecular weight dissolved organic matter from four US estuaries

High molecular weight dissolved organic matter (HMW-DOM) represents an important component of dissolved organic carbon (DOC) in seawater and fresh-waters. In this paper, we report measurements of stable carbon (delta(13)C) isotopic compositions in total lipid, total hydrolyzable amino acid (THAA), total carbohydrate (TCHO) and acid-insoluble "uncharacterized" organic fractions separated from fourteen HMW-DOM samples collected from four U.S. estuaries. In addition, C/N ratio, delta(13) C and stable nitrogen (delta(15)N) isotopic compositions were also measured for the bulk HMW-DOM samples. Our results indicate that TCHO and THAA are the dominant organic compound classes, contributing 33-46% and 13-20% of the organic carbon in HMW-DOM while total lipid accounts for only <2% of the organic carbon in the samples. In all samples. a significant fraction (35-49%) of HMW-DOM was included in the acid-insoluble fraction. Distinct differences in isotopic compositions exist among bulk samples, the compound classes and the acid-insoluble fractions. Values of delta(13)C and delta(15)N measured for bulk HMW-DOM varied from -22.1 to -30.1parts per thousand and 2.8 to 8.9parts per thousand, respectively and varied among the four estuaries studied as well. Among the Compound classes, TCHO was more enriched in C-13 (delta(13)C = -18.5 to -22.8parts per thousand) compared with THAA (delta(13)C = -20.0 to -29.6parts per thousand) and total lipid (delta(13)C = -25.7 to -30.7parts per thousand). The acid-insoluble organic fractions, in general, had depleted C-13 values (delta(13)C = -23.0 to -34.4parts per thousand). Our results indicate that the observed differences in both delta(13)C and delta(15)N were mainly due to the differences in sources of organic matter and nitrogen inputs to these estuaries in addition to the microbial processes responsible for isotopic fractionation among the compound classes. Both terrestrial sources and local sewage inputs contribute significantly to the HMW-DOM pool in the estuaries studied and thus had a strong influence on its isotopic signatures. Copyright (C) 2004 Elsevier Ltd.

Potential P limitation leads to excess N in the pearl river estuarine coastal plume

There is excess nitrate (NO3) in the Pearl River coastal plume in the southern waters of Hong Kong in summer. We hypothesize that phosphorus (P) limitation controls the utilization of excess NO3 due to the high N:P ratio in the Pearl River. To test this hypothesis, we conducted two 1-day cruises on July 13 and 19, 2000 to examine the response of the phytoplankton to P additions with respect to changes in biomass, uptake of nutrients and nutrient uptake ratios using a batch incubation of natural water samples collected from the Pearl River estuary and adjacent coastal waters. At a station (E1, salinity =5) in the Pearl River estuary, the N/P ratio at the surface was 46:1, (64 muM DIN: 1.3 muM PO4) and decreased to 24:1 (12 muM DIN: 0.5 muM PO4) downstream at a station (Stn 26, salinity =26) in the coastal plume south of Hong Kong. Without a P addition, NO3 in the water samples collected at E1 could not be depleted during a 9 day incubation (similar to20 muM NO3 remaining). With a P addition, NO3 disappeared completely on day 6 with the depletion of the added PO4 (2-3 muM). This was also true for a station, E4 (salinity= 15) further downstream, but within the estuary. At Stn 26, in the coastal plume south of Hong Kong, NO3 (similar to11.5 muM) was eventually depleted without the addition of PO4, but it took 8 days instead of 5 days for Stn E4. The uptake ratio of dissolved inorganic nitrogen (DIN) to PO4, without a P addition was 51:1, 43:1 and 46:1 for Stns E1, E4 and 26, respectively. With a P addition, the DIN/PO4 uptake ratio decreased to 20:1, 14:1 and 12:1, respectively, for the 3 stations. These results clearly indicate potential P limitation to utilization of NO3 in the Pearl River estuary, resulting in excess NO3 in waters of the coastal plume downstream of the estuary, some of which would eventually be transported offshore. High uptake ratios of N:P without a P addition (43N:1P) suggest that phytoplankton have a nitrogen uptake capacity in excess of the Redfield ratio of 16N: 1P by 2.5-3 times. The value of 2.5-3 times was likely a maximum that should have contained a contribution of P released from desorption of P from sediments or from regeneration by zooplankton grazing and bacterial activity during the incubation of natural water samples. Without a P addition, however, phytoplankton biomass did not increase. This means that P turnover rates or regeneration may allow phytoplankton to take up additional N in excess of the Redfield ratio and store it, but without increasing the algal biomass. Therefore, high ambient N:P ratios in excess of the Redfield ratio do indicate potential P limitation to phytoplankton biomass in this estuarine coastal ecosystem. (C) 2004 Elsevier Ltd. All rights reserved.

Sources and preservation of organic matter in Plum Island salt marsh sediments (MA, USA): long-chain n-alkanes and stable carbon isotope compositions

Elemental (TOC, TN, C/N) and stable carbon isotopic (delta(13)C) compositions and n-alkane (nC(16-38)) concentrations were measured for Spartina alterniflora, a C-4 marsh grass, Typha latifolia, a C-3 marsh grass, and three sediment cores collected from middle and upper estuarine sites from the Plum Island salt marshes. Our results indicated that the organic matter preserved in the sediments was highly affected by the marsh plants that dominated the sampling sites. delta(13)C values of organic matter preserved in the upper fresh water site sediment were more negative (-23.0+/-0.3) as affected by the C-3 plants than the values of organic matter preserved in the sediments of middle (-18.9+/-0.8) and mud flat sites (-19.4+/-0.1) as influenced mainly by the C4 marsh plants. The distribution of n-alkanes measured in all sediments showed similar patterns as those determined in the marsh grasses S. alterniflora and T. latifolia, and nC(21) to nC(33) long-chain n-alkanes were the major compounds determined in all sediment samples. The strong odd-to-even carbon numbered n-alkane predominance was found in all three sediments and nC(29) was the most abundant homologue in all samples measured. Both delta(13)C compositions of organic matter and n-alkane distributions in these sediments indicate that the marsh plants could contribute significant amount of organic matter preserved in Plum Island salt marsh sediments. This suggests that salt marshes play an important role in the cycling of nutrients and organic carbon in the estuary and adjacent coastal waters. (C) 2003 Elsevier Ltd. All rights reserved.