Gasbench Ⅱ-IRMS升级NO预富集装置测定海水硝酸盐的氮氧同位素

本研究研制了由气压棒、气体控制阀、不锈钢管冷阱、石英毛细管冷阱、杜瓦瓶、化学阱等构成的NO预富集装置,通过扩展GasbenchⅡ功能控制冷阱的升降,改造气体回路、进样针和样品盘,实现NO的预富集以及GasbenchⅡ自动进样与IRMS联机测定.通过将海水中的硝酸盐经化学方法转化成NO,建立了海水硝酸盐氮、氧同位素的分析方法.研究表明,所建立方法对海水硝酸盐氮、氧同位素的分析具有很好的精度,硝酸盐δN、δO及峰面积的相对标准偏差分别小于1%、3%和5%.对采自南极普里兹湾海水样品中硝酸盐氮、氧同位素的分析结果与文献报道值吻合,也与海水硝酸盐氮、氧同位素组成的变化规律相一致,证明所建立的技术方法可成功运用于海水硝酸盐氮、氧同位素的分析.高等学校仪器设备和优质资源共享系统大型仪器示范机组建设资助项目(CERS-1-76)；国家重点基础研究发展计划资助项目(2015CB452903)；南北极环境综合考察与评估专项资助项目(CHINARE2016-01-04-03)；国家自然科学基金杰出青年基金资助项目(41125020)

白令海盆氮吸收速率的同位素示踪

于白令海中心海盆与陆坡区采集了四个站位真光层以浅的垂直水样,利用15N示踪法确定了研究海域NO3-和NH4+的吸收速率.结果表明,真光层中NO3-和NH4+绝对吸收速率的积分平均值分别为1.3和4.5mmol.m-2.d-1,中心海盆区的数值低于陆坡区.氨盐的绝对吸收速率、比吸收速率均较硝酸盐的相应值来得高,表明氨盐是研究海域浮游植物优先利用的氮营养盐,研究海域低的f比值(≤0.3)、NO3-和NH4+的相对优先指数数值(RPINO31)进一步证实了上述论断.将研究海域表层水营养盐、Chl.a,PON含量、氮的比吸收速率、绝对吸收速率与沿岸上升流、HNLC海域进行比较后发现,白令海中心海盆是一个高营养盐、低生物量、低新生产力、低f比值的海域,它与白令海陆架区以及其他上升流海域具有明显不同的生态特征,白令海中心海盆应属HNLC海域.国家自然科学基金(批准号:90411016);; 国家重点基础研究发展计划项目(批准号:2005CB422305);; 教育部新世纪优秀人才计划(批准号:NCET-04-0593)资助项

加拿大海盆河水组分的平均停留时间

通过对西北冰洋海水中18O,226Ra,228Ra的分析,应用δ18O-S-PO*示踪体系计算了水体中河水组分和海冰融化水组分的份额,并根据陆架区与深海盆228Ra/226Ra)A.R.与河水组分之关系的差异估算海盆区河水组分的平均停留时间.结果表明,加拿大海盆的河水份额明显高于陆架区,证实该海盆是陆架所输送河水的主要储存区.楚科奇陆架、波弗特陆架水体中的228Ra活度浓度介于0.16～1.22Bq/m3之间,比中、低纬度陆架区的数值来得低,反映出海冰融化水的影响.陆架水228Ra/226Ra)A.R.与河水组分份额之间具有良好的线性正相关关系,而加拿大海盆水体的228Ra/226Ra)A.R.落在该拟合线下方,反映出水体离开陆架区往深海盆运移过程中228Ra的放射性衰变损失.根据陆架水与海盆水228Ra/226Ra)A.R.与河水组分份额之关系的差异估算出加拿大海盆河水组分的平均停留时间为5.0～11.0a.该停留时间决定了北大西洋深层水形成区域上层水体淡化对北冰洋入海径流响应的滞后时间.教育部新世纪优秀人才基金(批准号:NCET-04-0593);; 中国首次北极科学考察专项基金资助项

Bacterial productivity in the Prydz Bay and its adjacent waters, Antarctic

Bacterial productivity was measured using 3H-thymidine methods in the Prydz Bay and its adjacent waters in the Southern Ocean during the 16th National Antarctic Research Expedition of China (CHINARE). The results showed that bacterial productivity in our study areas ranged from 4.5 to 191 ngC·dm -3·h -1, with an average of 50.4 ngC·dm -3·h -1. These values were comparable to those reported for the Ross Sea. The mean ratio of bacterial productivity to primary productivity in our study area..

The sources of the upper and lower halocline water in the Canada Basin derived from isotopic tracers

Seawater samples were collected in the water column from the Canada Basin aboard RV Xuelong in August 1999. Concentrations of d D, d 18O, nutrients (NO3-, PO43-, SiO32-) and dis-solved oxygen were measured, along with hydrographic parameters (salinity and temperature). Our results showed that the upper layer of the water column was characterized by the occurrence of the upper halocline water (UHW) and the lower halocline water (LHW). The UHW was associ-ated with a salinity of 33.1 (~150m depth) and maximum...This work was supported by the Chinese First Arctic Expedition Foundation

Distribution of ~(226)Ra in the Arctic Ocean and the Bering Sea and its hydrologic implications

Radium-226 (226Ra) activities were measured in the surface water samples collected from the Arctic Ocean and the Bering Sea during the First Chinese National Arctic Research Ex-pedition. The results showed that 226Ra concentrations in the surface water ranged from 0.28 to 1.56 Bq/m3 with an average of 0.76 Bq/m3 in the Arctic Ocean, and from 0.25 to 1.26 Bq/m3 with an average of 0.71 Bq/m3 in the Bering Sea. The values were obviously lower than those from open oceans in middle and low latitudes, indicating ...supported by the First Chinese National Arctic Research Expedi-tion Program

Biological nitrogen fixation in the upper water column in the south Taiwan Strait during summer 2011

2011年6—7月,利用15n2示踪法实测了台湾海峡南部海域的生物固氮速率,结合温度、盐度、天然颗粒物氮同位素组成的分布,分析并讨论了影响研究海域生物固氮速率的环境因素。结果表明,夏季台湾海峡南部海域的生物固氮速率介于168—1080 nMOl M-3d-1之间,平均为537 nMOl M-3d-1,较高的生物固氮速率大多出现在次表层水体中。研究站位的积分固氮速率变化范围为11—40μMOl M-2d-1,平均为23μMOl M-2d-1。积分固氮速率的空间变化与不同水团的影响有关,在受黑潮水影响的海域,生物固氮速率较高,而在上升流和受河流冲淡水影响的海域,生物固氮速率较低,说明较低的水温及较高的无机氮营养盐可能会抑制研究海域的生物固氮作用。研究海域天然颗粒物δ15n与生物固氮速率之间呈现良好的负相关关系,表明天然颗粒物氮同位素组成可定性指征研究海域生物固氮作用的强弱。Biological N2fixation in marine environments is a major component in the ocean nitrogen budget and plays an important role in global carbon cycles through the sequestration of atmospheric carbon dioxide and production of marine organic matter.N2fixation could be regulated by the abundance and chemical speciation of nutrients and many trace elements in seawater.Recent studies have revealed that N2fixation is much more widespread in marine environments than previously thought.However,little is known about the N2fixation in the Taiwan Strait,especially on N2fixation rates,and their relationship with environmental parameters.The major objectives of this study were to determine the N2fixation rates and their spatial distributions and to explore major physicochemical controlling factors in the south Taiwan Strait.During June and July 2011,seawater samples were collected from ten stations at two transects in the south Taiwan Strait for the measurements of N2fixation rate using the15N2tracer assay.Particulate nitrogen and its isotopic composition were measured with an elemental analyzer(Carlo Erba NC 2500) coupled with a Finnigan MAT DeltaplusXP isotope ratio mass spectrometer.Reproducibility of nitrogen isotope measurements(in terms of δ15N) was within 0.2‰.Our results showed that N2fixation rates in the south Taiwan Strait ranged from 168—1080 nmol m-3d-1with an average of 537 nmol m-3d-1.Most of the high rates were observed at subsurface layers.The depth-integrated N2fixation rates were 11—40 μmol m-2d-1with an average of(23±10) μmol m-2d-1.The distribution of the N2fixation rates showed regional variations with influence from water masses with distinctive temperature and salinity.Higher N2fixation rates were mostly observed in the regions influenced by the Kuroshio,with an average of 31 μmol m-2d-1,while lower rates occurred in the upwelling and river plume regions with an average of 15 μmol m-2d-1.This spatial distribution pattern indicated that biological N2fixation was largely impeded by the low temperature and the high concentration of dissolved inorganic nitrogen in the south Taiwan Strait.The contribution of N2fixation in the study area could be further quantified based on the δ15N signatures of suspended particles which could be significantly depleted during N2fixation.Indeed,a negative correlation between the δ15N signatures of suspended particles and N2fixation rates was observed regardless of using all data points or depth-averaged values within the water column.This indicated that15N-depleted particles were largely derived from the enhanced N2fixation,supporting the use of nitrogen isotopic composition(δ15N) of suspended particles as a potential indicator of N2fixation in the south Taiwan Strait.Further studies are needed to better elucidate the relationship between N2fixation rates and limiting elements and their chemical speciation,and thus the physical and biogeochemical controls on N2fixation in the south Taiwan Strait.国家自然科学基金资助项目(41125020;41076043;41206062); 国际海域资源调查与开发“十二五”项目(DY125-13-E-01

基于Crossbar的多通道DMA控制器设计与实现

本文给出了一种基于Crossbar的多通道DMA控制器的设计方案,它能有效地提高DMA数据传输的效率和减少系统CPU的中断次数,保证多核SOC系统的任务执行效率及传输接口的通信实时性。经FPGA验证表明,所设计的多通道DMA控制器比传统的DMA有更好的效能及性价比

上颌骨内埋伏正中多生牙的生长特征与影像表现

【目的】分析上颌骨内埋伏正中多生牙的生长特征与影像学特点, 探讨其早期诊断与术前三维定 位的方法。【方法】对216 例上颌骨埋伏正中多生牙患者进行系统的临床检查与X 线定位摄影, 对埋伏正中牙 的生长特征( 方向、类型、形态、大小) , 影像定位诊断及其对邻近恒牙的干扰情况分类统计分析。【结果】该类 多生牙最常表现为圆锥型小牙, 平均长度为1.6 cm, 平均直径为0.6 cm; 其在上颌骨内常呈倒置向( 83.5%) , 并居于恒中切牙的腭侧为主( 76.5%) 。对邻近切牙的干扰主要为造成恒中切牙的间隙过大( 36.6%) 、扭转移位 (33.3%)和萌出受阻(19.9%)。位于恒牙根侧方的多生牙对中切牙生长的干扰远大于恒牙根上方的多生牙( P< 0.01) 。【结论】上颌骨埋伏正中牙多为圆锥型小牙, 常紧贴于恒中切牙的腭侧或近中倒置生长, 其对中切牙的 生长干扰较大; 用X 线视差定位法可作出准确的三维定位诊断, 对制订早期手术摘除方案有重要意义

禁止底拖网作业对珠江口香港海域底层鱼类的影响

【目的】研究禁止底拖网作业对珠江口香港海域底层鱼类的影响。【方法】根据2007-2009年及2014-2016年在珠江口香港海域进行的定点底拖网调查数据,分析该海域在禁止底拖网捕捞实施前后鱼类种类组成及生物量和生态多样性指数,评估5种典型底层鱼类资源的变化。【结果与结论】该海域捕获鱼类种类数在禁止底拖网作业后明显增加,鱼类种类数量从44种升至73种。种类丰富度指数D变化范围为:2007至2009年,4.937～5.711,2014至2016年,6.559～7.074;多样性指数H’变化范围为:2007至2009年,1.945～2.841,2014至2016年,2.220～2.381;均匀度指数J变化范围为:2007至2009年,0.539～0.776,2014至2016年,0.557～0.600。卵鳎Solea ovata、韦式羊舌鮃Arnoglossus waitei、尖嘴魟Dasyatis zugei这3种底层鱼类禁止底拖网实施后在数量(number)和生物量(biomass)上都增幅明显。不同站位数量和生物量的数值在“禁拖令”实施后也都有所增加,其中以站位2(大屿山以北,较靠近香..