Compensation effect of polyimide thin films on normally white twisted nematic liquid crystal displays

The disadvantages of Normally White Twisted Nematic Liquid Crystal Display (NW-TN-LCD) were discussed. The reason that the negative birefringent polyimide thin films were used to compensate NW-TN-LCD to decrease off-axis leakage, improve contrast ratios and enlarge viewing angles was explained in this paper. A certain polyimide thin film was taken as an example to show compensation effect on NW-TN-LCD.

渤海沉积物中氮的赋存形态及其在循环中的作用

为揭示渤海沉积物中氮的生物地球化学循环过程，本文应用自然粒度下的分级分离浸取方法首次对渤海沉积物中氮的形态进行了研究，获得了氮形态分布的地球化学特征；将沉积物氮中可转化和非转化部分定量区别开，并对可转化态中各形态氮对其循环贡献的大小进行了评估；结合底栖生物的分布初步探计了沉积物中氮与生物生产的关系及底栖生物对氮循环的影响。得到的主要结论包括：渤海沉积物中氮的形态分布特征及其控制因素。表层沉积物中IEF-N、CF-N、IMOF-N和OSF-N占TN的比例分别为3.67%，0.31%，0.42%和26.45%，OSF-N是可转化态氮的优势形态。IEF-N 中NH_4~+和NO_3~-具有不同的成岩机制：NH_2~+主要受OC、Es和粘土矿物性质影响，NO_3~-与水体分布密切相关。CF-N含量最小，主要受沉积环境pH值的影响。IMOF-N主要由NH_4~+在Fe~（3+）上的吸附形成，受沉积物的氧化还原环境控制。OSF-N除与物质来源有关外，受到粘土矿物性质及沉积物粒度的影响。Fe、Mn和Co对IEF-N和IMOF-N的成岩作用影响明显，Cu、Pb和Mo对OSF-N的分布产生影响，二者作用的机理不同。表层样中，约69.15%的氮经过早期成岩作用而埋藏，短期内不再参与循环。氮的埋藏通量与沉积物聚积速率呈显著正相关，同时受温度、Eh、OC、盐度、硫化物含量等因素影响。沉积物中C/N和N/P均呈现异常的低值，前者主要是由于沉积物中保留了大量的无机氮，后者主要因为陆地排放大量磷入海以及磷的埋藏效率高于氮所致。柱状样中，IEF-N基本随深度减小，IMOF-N随深度有突变现象，OSF-N随深度的变化表明了矿化作用进行的程度。对沉积物中生源要素分解速率常数有：N>P>C>Si。表层沉积物中可转化态氮占总氮的比例高于深层沉积物。OC/ON随深度减小表明沉积物通过某种机制富集了有机氮。各形态氮在氮循环中作用及渤海氮循环收支。对渤海沉积物中可转化态氮的量进行了估算，IEF-N、CF-N、IMOF-N和OSF-N分别为3.657 * 10~8kg，2.794 * 10~7 kg，3.832 * 10~7kg和2.372平共处* 10~9kg；结合室内模拟的氮的界面交换通量，估算其完全释放所需的时间分别为2.15a，0.16a，0.225a和13.94a。各形态氮释放的顺序与其结合牢固程度一致，即IEF-N>CF-N >IMOF-N>OSF-N，其对界面交换的贡献大小则随时间尺度大小发生变化：随时间尺度增加，IEF-N、CF-N、IMOF-N的贡献逐渐减小，OSF-N的贡献逐渐增大，当时间尺度大到足以使四态氮完全释放时，其贡献的大小与各形态氮的量一致即OSF-N（84.6%）>IEF-N（13.0%）>IMOF-N（1.4%）>CF-N（1.0%）。非转化态氮占总氮的 69.15%，其中由于颗粒物包裹导致的“非转化态”氮为49%，说明粒度的影响非常重要。IEF-N和OSF-N主要存在于颗粒物质外层，是循环的主要参与者，CF-N和IMOF-N绝大部分在内层，对循环的贡献很小。水体中再循环的氮对初级生产力的贡献（74.4%）比沉积物中再循环氮的贡献 （26.1）大得多，二者对生态系统的作用不同，水体再生的营养盐通常在较长的时间尺度上维持初级生产力的平衡，而沉积物中的再生则在很短的时间内通过强烈的混合作用提高初级生产力。沉积物中氮与生物生产的关系及底栖生物对沉积物氮循环的影响。IEF-N和OSF-N的分布均与初级生产力以及浮游植物个体数量的分布具有一定的相似性。沉积物中的IEF-N的作用相当于一个氮营养盐的“储存库”对初级生产力产生影响，其作用机制类似于水体富营养化的正反馈机制。IEF-N能对赤潮的发生起加速作用。底栖生物的分布与氮形态分布具有正的相关性：莱洲湾内IEF-N和OSF-N的分布与该区域高生物量和高密度的大型底栖动物分布一致，说明在底栖生物活动活跃的区域营养盐的再生和流动是高效而迅速的。生物扰动能加速矿化作用的进行，使沉积物在一定深度范围内NH_4~+含量增加，大型底栖动物的灌溉作用使NO_3~-在深层仍有较高的分布。底栖生物的不同种群对营养盐变化的响应不同。

浅海贝藻养殖水域沉积物再悬浮的发生机制及生态效应

沉积物再悬浮作为一个比较普遍的物理现象，对浅海生态系统污染物的生物地球化学循环具有强烈的干扰作用。本研究以我国北方重要养殖海湾——桑沟湾为研究对象，从物理、化学、生物三个角度出发，研究了沉积物再悬浮的发生过程以及再悬浮介质-沉积物的源汇转换角色及其与养殖藻类的关系，构建了波流耦合模型和再悬浮颗粒物浓度预测数学模型。主要研究结果如下： 1）桑沟湾的海湾动力比约为1.54，沉积物具有发生再悬浮的潜在动力条件；推导出波流耦合切应力的计算公式。 2）悬浮颗粒物浓度（SSC）与浊度（NTU）之间符合线性方程SSC=15.908×ln（NTU）+7.0888（n＝33，R2＝0.7209）；碎屑有机碳库是桑沟湾养殖生态系统中最大的有机碳库，占总POC库储量的81.87%。 3）沉积物再悬浮的临界切应力在0.059 N/m2左右，耦合切应力与悬浮颗粒物浓度符合方程= 238.06 SSC + 25.215（n=25，R2 = 0.7298）；最大剪切深度可达8.81 cm；桑沟湾沉积物再悬浮通量的数量级在10-5~10-6 kg·m-2·s-1之间，再悬浮临界风速约为5.51 m/s，全年约有171天沉积物处于再悬浮状态；构建了沉积物再悬浮颗粒物浓度预测数学模型。 4）桑沟湾表层沉积物总氮的含量范围313.09~1094.44µg/g，有机氮是总氮的主要形态，平均占总氮的60.86%；交换态氮是无机氮的主要形式，平均占无机氮的71.40%，交换态氮中NO3--N的含量最大；桑沟湾表层沉积物的TOC/TN比值为9.38，表明沉积物中有机质具有混合来源的特征；无机磷是桑沟湾表层沉积物中磷的主要形态，平均占总磷的73.33%，钙结合磷是无机磷的主要赋存形态；表层沉积物中潜在生物有效性磷的含量占总磷的86.54%，具有很强的释磷潜力。桑沟湾重金属的潜在生态危害指数RI约为36.17，表明重金属的潜在生态危害轻微。 5）再悬浮过程中沉积物春季表现为氮磷源，释放溶解无机氮和磷酸盐；夏、秋季表现为氮汇磷源，释放磷酸盐而吸附溶解无机氮；冬季表现为氮磷汇，吸附磷酸盐和溶解无机氮。

刺参生态增养殖原理与关键技术

针对目前刺参养殖业中面临的问题，系统研究了刺参的基础生物学、组织学，生理生态学和呼吸生理学特征，评估了刺参的养殖容量，优化了养殖模式，以嵊泗列岛为例，系统研究了刺参南移后的存活和生长等特征。研究结果如下： 1．刺参体腔液细胞存在于刺参的体腔中，体腔液细胞行使免疫防御、营养贮存和运输的功能。根据形态和功能上的特征可分为小淋巴细胞、桑葚细胞、吞噬细胞、结晶细胞、纺缍细胞和振动细胞。体腔液细胞的形态和结构与其功能密切相关。不同特征的细胞可能是同一类型体腔液细胞的不同发育阶段。体腔液细胞平均密度为(3.79 ± 0.65)×106 cells /ml-1. 刺参的血淋巴细胞可分为小淋巴细胞、桑葚细胞、吞噬细胞和结晶细胞。刺参体腔液细胞可分为小淋巴细胞、桑葚细胞、吞噬细胞、结晶细胞、纺锤细胞和振动细胞。刺参吞噬细胞的吞噬率与温度呈正相关，并呈现出强烈的凝集现象。 2．刺参的血管、呼吸树、肌细胞和体腔内皮细胞的超微结构复杂，与其功能密切相关。夏眠前后刺参消化道明显萎缩，上皮细胞重吸收现象显著，结果显示组织结构的改变与外界环境相适应。刺参夏眠时体腔液pH和PO2升高，PCO2降低。连续取样对刺参体腔液血气指标没有显著性影响。刺参体腔液的%Extrw和%EwO2与体重呈负相关。 3．刺参的扰动导致底质中有机物含量、TOC、TN、叶绿素和细菌含量降低，刺参粪便中有机物含量高于周围底质，刺参对摄食底质具有选择性。刺参的扰动能增强底质的稳定性，与对照组相比，硫化物含量和氧化还原电位降低。 4．根据水体理化指标变化和自然沉积有机物的供饵力，结合不同温度下大规格刺参对自然生物沉积物的吸收率，计算刺参的养殖容量。浅海典型水域刺参的养殖容量约为109.40 g y-1m-2。 5．前三岛近岛水域底质有机物含量高于离岸深水水域，且粒度较离岸水域细，大多在0.20 mm以下。刺参的放流浓度和参礁的放置深度应选择在5-12m。刺参的放养规格宜为经人工越冬后体长在8-10厘米的参苗，体重超过30克。 6．研究了三种规格的刺参笼养殖存活和生长特征，初步建立了刺参筏式笼养技术。投喂海带，存活率达到83%以上。密度对刺参的生长有着显著的影响，随着实验的进行，放养密度增加，刺参的体重减小。4月后，随着温度的升高和海况的改变，刺参的生长率下降。刺参南移养殖模式的适宜放养密度应控制在3-5头，放养规格应在40g以上，经过5-6个月的生长能达到100g左右。

海洋沉积物中磷化氢的分布、释放与转化研究

磷化氢（PH3）是磷循环的气相载体，以气体自由态和基质结合态（MBP）两种形式存在于环境中。自然环境中磷化氢的发现是对磷生物地球化学循环的重要补充，它在磷循环中的地位和作用及产生机制开始成为人们关注的热点。目前国内外在湖泊、陆地土壤及大气中已开展了较为广泛的研究，但是关于海洋中的研究还较少。开展磷化氢在海洋沉积物中的分布特征，及其释放通量、与其它磷形态的转化、对微藻生长的影响等行为研究对弄清海洋环境中磷化氢的迁移转化机制及其在磷循环中的作用和地位具有重要的科学意义。 本论文以不同环境条件下的海洋沉积物为研究对象，采用野外实验与室内模拟相结合的方法，运用改进的柱前二次低温冷阱富集和气相色谱-氮磷检测器联用技术等分析手段，系统研究了海洋沉积物中磷化氢的分布特征、环境因子对其分布的影响、沉积物磷化氢向水体、大气中的释放、迁移、转化规律；初步了解了海洋沉积物中结合态磷化氢的分布特征及其释放通量；揭示了磷化氢对海洋环境的可能影响。主要研究结果如下： MBP广泛存在于海洋沉积物中。中国沿海表层沉积物中MBP的浓度范围为：0.89-25.86 ng/kg, dry，其分布也表现出一定的空间分布特征，在同一离岸断面上，有近岸浓度高，远岸浓度低的分布规律；在北黄海、南黄海、东海北部海域、东海南部海域和南海海域的平均浓度分别为：5.57±3.78、3.78±2.81、5.27±3.07、5.48±4.05 和 13.52±7.86 ng/kg dry，与其它海域相比，南海海域的MBP浓度要相对较高一些。长江口海域表层沉积物中MBP的浓度范围为：1.93-94.86 ng/kg, dry。其分布也表现出一定的空间和季节分布特征。上游河口沉积物中MBP的浓度要普遍高于下游河口，平均浓度分别为31.34和4.79 ng/kg, dry。靠近石洞口、竹园排污口以及黄浦江口的S3和S4站位处MBP的浓度要显著高于其它站位，季节平均浓度分别为43.01和61.54 ng/kg, dry。MBP浓度的季节差异并不显著，上游河口和下游河口MBP浓度表现出相似的季节变化特征，一般来说8月和11月要稍高于2月和5月。澳大利亚伊拉瓦拉海湾柱状沉积物中的MBP表现出一定的垂直分布特征。两个柱状沉积物样品均在中下层存在MBP的高值区，且该海湾MBP的含量要远高于中国近海及长江口海域MBP的含量，两个柱状沉积物中MBP的平均浓度分别为637.3和542.6 ng/kg, dry。 环境因子与MBP含量关系的研究结果表明：较高的TP、OP、IP、OC、TN含量均有利于高浓度MBP的产生；TP、OP、OC与MBP含量之间存在着较强的线性相关关系，是控制MBP分布的主要因素；氧化还原电位与MBP含量存在着显著的线性负相关，说明还原环境更有利于沉积物中高浓度MBP的存在；平均粒径与MBP含量存在着一定的线性负相关，说明小粒径有利于高浓度MBP的存在；水深、上升流引起的扰动等也是影响MBP分布的可能原因。并且，在本论文对中国沿海沉积物、长江口沉积物和澳大利亚海湾沉积物的研究中，均得到了MBP含量与OP存在着强烈的线性相关关系，而与IP的线性相关关系较弱或不相关的结论，说明海洋沉积物中的MBP更可能来源于微生物对有机磷成分的降解。另外，长江口海域沉积物中MBP含量与上层海水中活性磷酸盐、总磷、叶绿素a的含量也存在着一定的线性相关关系，说明沉积物中磷化氢的释放可能会对上层水环境产生影响。 静态箱法释放通量的研究结果显示，胶州湾海域沉积物存在着磷化氢的释放现象。沉积物-大气界面和水-大气界面磷化氢的释放通量分别为：27.77和17.37 ng/(m2•h)，该结果要高于Louisiana湿地、水稻田和太湖水体磷化氢的排放通量。并据此估算出胶州湾的磷化氢年排放量为75.75kg/y，高于太湖及比利时垃圾填埋场的磷化氢年排放量。不同底质沉积物释放磷化氢的顺序为：虾池沉积物>滩涂沉积物>海滩黑泥沉积物>海滩排污口旁的砂质泥；践踏能显著促进磷化氢的释放。磷化氢的释放通量与沉积物中MBP的含量有显著的线性相关关系；胶州湾养殖池、滩涂沉积物及海域水体是大气中磷化氢的重要来源，沉积物中的磷化氢可连续向上层水体或大气中释放。晴天，胶州湾近海海域空气中磷化氢的浓度范围为1.06-16.90 ng/m3，且表现出早上和傍晚高，中午时分相对较低的变化规律；空气中磷化氢的浓度与光照强度及释放源释放量的大小有关。 利用室内模拟方法，研究了磷化氢在海水中的转化过程及其对海洋微藻生长的影响，并得出了一些初步结论。日光灯照射条件下，通入海水中的磷化氢可部分转化为磷酸盐和总磷，并且转化后主要以磷酸盐的形式存在。环境条件会对该转化过程产生影响，避光条件下，磷化氢的转化率较低，日光灯照射和紫外灯照射均能促进该转化过程，特别是紫外灯照射，促进效果显著；添加氧气或三价铁离子氧化剂也能促进该转化过程。微藻生长实验结果表明，适量磷化氢气体的通入，能显著刺激并促进磷限制条件下东海原甲藻和赤潮异弯藻的生长，但这种刺激作用并不是无限制的，后期刺激生长作用会变弱或停止生长；低量磷化氢气体的通入，刺激作用不明显；高量磷化氢气体的通入，则会抑制两种海洋微藻的生长。东海原甲藻和赤潮异弯藻对通入磷化氢的响应略有差异，后者对磷化氢的反应更为灵敏； 次磷酸盐和亚磷酸盐也都能刺激两种海洋微藻的生长，但与磷化氢相比，其影响作用相对较小。 本论文的初步研究结果表明，在磷的海洋生物地球化学循环中，需要考虑磷化氢的作用，其长期、连续的释放对磷循环的贡献不可忽视，并可能是磷限制海域赤潮形成的补充机制。

东海内陆架泥质区EC2005孔沉积特征及古环境记录

本论文通过对东海内陆架浙闽沿岸泥质沉积带EC2005孔沉积物岩性、粒度、AMS14C测年、粘土矿物以及全岩矿物衍射分析、沉积物常微量元素和稀土元素分析、总碳氮以及有机碳氮分析、磁化率测试和综合研究，以EC2005孔岩芯记录为依据分析了研究区的沉积环境演化、海平面升降、浙闽沿岸流形成历史以及蕴含的古气候信息，探讨了陆源物质矿物、地球化学成分与粒度的关系。 EC2005孔岩芯自底部至41.00 m（17.3~13.1 ka BP）为末次冰消期以来的湖泊三角洲沉积序列，物质来源主要是来自湖盆流域物质的输入。随着海平面逐渐上升，海水自13.1 ka BP开始侵入研究区，自12.3 ka BP开始海水深度加大，沿岸流的地位开始显现，7.3 ka BP以来，形成了高海平面以来主要受沿岸流控制的浅海沉积。稀土元素结果显示，东海内陆架EC2005孔12.3~9.8 ka BP是以湖盆流域近源物质为主向长江物质为主转变的过渡阶段，自大约10~9.8 ka BP开始，由于海水深度的进一步加大、沿岸流作用进一步增强，长江物质对研究区的物质供给成为主导。海平面的升高以及沿岸流的形成是物质来源发生变化的重要原因。 东海内陆架泥质沉积物中全新世期间长达700 a（5.9~5.2 ka BP）的高分辨率细粒敏感组分资料揭示的东亚冬季风增强，与GRIP冰芯δ18O揭示的冷期具有良好的对应关系。5500 a BP前后东亚冬季风突然增强，与世界范围内的5500 a BP强降温事件非常一致。功率谱分析揭示出62 a和11 a的太阳活动周期以及与现代ENSO周期相似的6 a和5 a周期，因此，中全新世东亚冬季风演化可能是太阳活动以及古ENSO事件对全球气候系统的影响所致。 东海内陆架区对末次冰消期至早全新世气候回暖的记录与该时期世界性的广泛记录相一致，应该是轨道时间尺度上太阳辐射增强与ITCZ北移以及太阳活动变化综合影响的结果。东海内陆架浙-闽沿岸泥质带EC2005孔存在的4个百年时间尺度上快速沉积事件：12.3~12.1 ka BP、7.5~7.3 ka BP、5.9~5.2 ka BP和1.5~1.3 ka BP，与新仙女木事件、7.3 ka BP冷事件、第二新冰期（5.5 ka BP强降温事件）以及北大西洋1.4 ka BP浮冰事件均有良好的对应，世界范围内广泛存在的8.2 ka冷事件对本钻孔沉积也形成了一定影响。 EC2005孔磁化率变化受到多种因素的制约，如岩性粗细、早期成岩作用以及人类活动等的影响。近3.6 ka以来，磁化率的剧烈波动可能是由于人类活动影响造成的。东海内陆架EC2005孔TOC、TN和TOC/TN的大小主要受控于岩性变化。 此外，根据陆源物质粒度和矿物成分之间的关系，建立了陆源物质平均粒径与主要矿物成分含量大小的函数模型。地球化学成分与其所赋存单种矿物的相关性分析则进一步表明，陆源矿物种类和含量控制着地球化学成分及其含量，矿物种类和含量对地球化学成分的控制是决定性的，而粒度对元素（化学成分）的“控制”实际上是由于不同粒度的矿物组分不同而造成。

Nutrient characteristics in the Yangtze River Estuary and the adjacent East China Sea before and after impoundment of the Three Gorges Dam

From November 2002 to 2006, five cruises were undertaken in the Yangtze River Estuary and the adjacent East China Sea to compare the nutrient concentrations, ratios and potential nutrient limitation of phytoplankton growth before and after impoundment (June 2003) of the Three Gorges Dam (TGD). Concentrations of dissolved inorganic nitrogen (DIN), soluble reactive phosphorus (SRP) and total nitrogen (TN) exhibited an increasing trend from 2002 to 2006. In contrast, total phosphorus (TP) concentration exhibited a decreasing trend. The mean concentrations of DIN, SRP, and TN in the total study area increased from 21.4 mu M, 0.9 mu M, and 41.8 mu M in 2002 to 37.5 mu M, 1.3 mu M. and 82.2 mu M in 2006, respectively. while TP decreased from 2.1 mu M to 1.7 mu M. The concentration of dissolved reactive silica (DRSi) had no major fluctuations and the differences were not significant. The mean concentration of DRSi in the total study area ranged from 52.5 to 92.3 mu M. The Si:N ratio decreased significantly from 2.7 in 2002 to 1.3 in 2006, while TN: TP ratio increased from 22.1 to 80.3. The area of potential P limitation of phytoplankton growth expanded after 2003 and potential Si limitation appeared in 2005 and 2006. Potential P limitation mainly occurred in an area of salinity less than 30 after 2003, while potential Si limitation occurred where the salinity was greater than 30. By comparison with historical data, the concentrations of nitrate and SRP in this upper estuary during November 1980-2006 increased obviously after impoundment of TGD but DRSi decreased. Meanwhile, the ratios of N:P, Si:N and Si:P decreased obviously. (c) 2009 Elsevier B.V. All rights reserved.

Characteristics of nitrogen forms in the southern Huanghai Sea surface sediments

The distributions of different forms of nitrogen in the surface sediments of the southern Huanghai Sea are different and affected by various factors. The contents of IEF-N, SOEF-N and TN gradually decrease eastward, and those of SAEF-N northward, while those of WAEF-N westward. Around the seaport of the old Huanghe (Yellow) River, the contents of both SOEF-N and TN are the highest. Among all the factors, the content of fine sediment is the predominant factor to affect the distributions of different forms of nitrogen. The contents of IEF-N, SOEF-N, and TN have visibly positive correlation with the content of fine sediments, and the correlative coefficient is 0.68, 0.58 and 0.71 respectively, showing that the contents of the three forms of nitrogen increase with those of fine sediments. The content of WAEF-N is related to that of fine sediments to a certain extent, with a correlative coefficient of 0.35; while the content of SAEF-N is not related to that of fine sediments, showing that the content of SAEF-N is not controlled by fine grain-size fractions of sediments. In addition, the distributions of different forms of nitrogen are also interacted one another, and the contents of IEF-N and SOEF-N are obviously affected by TN, while those of inorganic nitrogen (WAEF-N, SAEF-N and IEF-N) are not affected by SOEF-N and TN obviously, although they are interacted each other.

A nitrogen budget of the Changjiang river catchment

Based on 1997-1998 field investigations in the Changjiang river mouth, rain sampling from the river's upper reaches to the mouth, historical data, and relevant literature, the various sources of Total Nitrogen (TN) and Dissolved Inorganic Nitrogen (DIN) in the Changjiang river catchment and N transport in the Changjiang river mouth were estimated. The export fluxes of various form of were mainly controlled by the river runoff, and the export fluxes of NO3-N, DIN and TN in 1998 (an especially heavy flood year) were 1438 103 tonnes (t) yr(-1) or 795.1 kg km(-2) yr(-1) 1746 10(3) t yr(-1) or 965.4 kg km(-2) yr(-1) and 2849 10(3) t yr(-1) or 1575.3 kg km(-2) yr(-1), respectively. The TN and DIN in the Changjiang river came mainly from precipitation, agricultural nonpoint sources, N lost from fertilizer and soil, and point sources of industrial waste and residential sewage discharge, which were about 56.2% and 62.3%, 15.4% and 18.5%, 17.1% and 14.4%, respectively, of the N outflow at the Changjiang river mouth; maximum transport being in the middle reaches.

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.

Seasonal and spatial distribution of matrix-bound phosphine and its relationship with the environment in the Changjiang River Estuary, China

Sediment is commonly considered as a source of phosphine, which is a highly toxic and reactive atmospheric trace gas. This study aims to investigate the seasonal and spatial distribution of matrix-bound phosphine (MBP) and its relationship with the environment in the Changjiang River Estuary. A total of 43 surface sediments were collected in four seasons of 2006, and concentrations of MBP and relative environmental factors were analyzed. MBP ranged from 1.93 to 94.86 ng kg(-1) dry weight (dw) with an average concentration of 17.14 ng kg(-1) dw. The concentrations of MBP in the tipper estuary were, higher than those in the lower estuary, which could be attributed to greater pollutant inputs in the upper estuary. The concentrations of MBP also varied with season, with November > August > May > February. Significant correlations existed between MBP and total phosphorus (TP), organic phosphorus (OP), inorganic phosphorus (W), organic carbon (OC), total nitrogen (TN), the grain size, and redox potential (Eh), suggesting that these sedimentary environmental characteristics played an important role in controlling the MBP levels in the sediments. Notably, there were positive linear relationships between the concentrations of soluble reactive phosphorus (SRP), TP, and chlorophyll a (Chl a) in bottom water and MBP in sediments. These relationships might be very complicated and need further exploration. This work is the first comprehensive study of the seasonal and spatial distribution of MBP in sediments and its relationships with environmental factors in a typical estuary, and will lead to deeper understanding of the phosphorus (P) biogeochemical cycle. (C) 2008 Elsevier Ltd. All rights reserved.

Organic carbon source and burial during the past one hundred years in Jiaozhou Bay, North China

Organic carbon (OC), total nitrogen (TN), and Pb-210 in core sediment were measured to quantify the burial of organic carbon and the relative importance of allochthonous and autochthonous contributions during the past one hundred years in Jiaozhou Bay, North China. The core sediment was dated using Pb-210 chronology, which is the most promising method for estimation of sedimentation rate on a time scale of 100-150 years. The variation of the burial flux of organic carbon in the past one hundred years can be divided into the following three stages: (1) relatively steady before 1980s; (2) increasing rapidly from the 1980s to a peak in the 1990s, and (3) decreasing from the 1990s to the present. The change is consistent with the amount of solid waste and sewage emptied into the bay. The OC:TN ratio was used to evaluate the source of organic carbon in the Jiaozhou Bay sediment. In the inner bay and bay mouth, the organic carbon was the main contributor from terrestrial sources, whereas only about half of organic carbon was contributed from terrestrial source in the outer bay. In the inner bay, the terrestrial source of organic carbon showed a steady change with an increase in the range of 69%-77% before 1990 to 93% in 2000, and then decreased from 2000 because of the decrease in the terrestrial input. In the bay mouth, the percentage of organic carbon from land reached the highest value with 94% in 1994. In the outer bay, the sediment source maintained steady for the past one hundred years.

Characteristics of nitrogen forms in the surface sediments of southwestern Nansha Trough, South China Sea

The area of the southwestern Nansha Trough is one of the most productive areas of the southern South China Sea. It is a typical semi-deep sea area of transition from shoal to abyssal zone. To understand distributions and roles of nitrogen forms involved in biogeochemical cycling in this area, contents of nitrogen in four extractable forms: nitrogen in ion exchangeable form (IEF-N), nitrogen in weak acid extractable form (WAEF-N), nitrogen in strong alkali extractable form (SAEF-N) and nitrogen in strong oxidation extractable form (SOEF-N), as well as in total nitrogen content (TN) in surface sediments were determined from samples collected from the cruise in April-May 1999. The study area was divided into three regions (A, B and C) in terms of clay sediment (< 4 mu m) content at < 40%, 40%-60% and > 60%, respectively. Generally, region C was the richest in the nitrogen of all forms and region A the poorest, indicating that the finer the grain size is, the richer the contents of various nitrogen are. The burial efficiency of total nitrogen in surface sediments was 28.79%, indicating that more than 70% of nitrogen had been released and participated in biogeochemical recycling through sediment-water interface.

Metagentiana, a new genus of Gentianaceae

The evidence from cross morphology, floral anatomy, chromosomes, palynology, and embryology all indicates that sect. Stenogyne is discordant within the genus Gentiana and is as distinct from the other sections of Gentiana as are other genera, such as Tripterospermum and Crawfurdia. In light of these characters, sect. Stenogyne is removed from Gentiana and given generic rank as the new genus Metagentiana. It is more related to Tripterospermum and Crawfurdia than to Gentiana, though it is more primitive than the first two genera. Together with Tripterospermum and Crawfurdia the new genus forms a monophyletic group, which is the sister group to the genus Gentiana. Fourteen new combinations required at specific rank are proposed.

Karyological studies on the Sino-Himalayan genus, Cremanthodium (Asteraceae : Senecioneae)

Twenty-two populations of seven species of Cremanthodium from high altitude regions of western China were observed karyologically. C. ellisii, C. microglossum, C. brunneo-pilosum, C. stenoglossum, C. discoideum and C. lineare all had the same chromosome number of 2n=58 whereas C. humile had 2n=60. All chromosome numbers of these species are documented here for the first time. The basic number of x=30 is new for this genus. The karyotypes of all species belong to 2A type according to Stebbins' asymmetry classification of karyotypes. Two basic chromosome numbers, x=30 and x=29 in Cremanthodium, correspond exactly to two branching patterns in this genus, sympodial versus monopodial. The systematic and taxonomic statuses of the sympodial species need further study. The karyomorphological data provide no support to the sectional subdivision in Cremanthodium. (C) 2001 The Linnean Society of London.