Concentrations and distribution of polycyclic aromatic hydrocarbons in surface sediments at western Xiamen Bay and assessment of their ecological risk

2004年11月30日至12月1日连续两天采集厦门西海域10个站位表层沉积物样品,参照美国EPA标准方法及采用气相色谱与质谱联用(GC/MS)技术,对表层沉积物样品中的多环芳烃(PAHs)进行测定分析。结果表明,厦门西海域表层沉积物样品中16种PAHs的总含量为198.2—1061.6 ng.g-1,平均值为723.51 ng.g-1,能检出的PAHs均以2—4环的芳香物为主;10个站位中X1、X2、X3、X6及M2站位的PAHs主要来源于化石燃料的不完全燃烧,其他站位以石油泄漏为主要来源。对PAHs的生态风险评价结果表明,厦门西海域表层沉积物中PAHs的环境毒性相对较低,说明该海域表层沉积物中PAHs对生物的危害程度较轻。Surface sediment samples at 10 sites of the western Xiamen Bay were collected on November 30 and December 1 of 2004.The U.S.EPA analytical methods were employed to examine polycyclic aromatic hydrocarbons(PAHs),and the concentrations of PAHs were determined by GC/MS.The results showed that the total concentrations of 16 PAHs varied from 198.2 to 1061.6 ng·g-1 dry weight,with an average of 723.51 ng·g-1.The dominant compositions are low molecular weight PAHs with 2—4 rings.The sources of PAHs in the sediments at X1,X2,X3,X6,and M2 sites were mostly from incomplete combustion of fossil fuel.The main possible sources of PAHs in the sediments at other sites were identified as oil spills.The toxicity of PAHs in the sediments at western Xiamen Bay was relatively low based on the assessment result of their ecological risk.福建省科技重点资助项目(2004I001

九龙江河口区水体中--（238）U、--（234）Th地球化学行为的研究

对采自九龙江河口区盐度介于0~21.97的10个表层水样，铀、钍同位素的测定结果表明，九龙江河口区水体中溶解态的（238）u含量与盐度之间存在着良好的相关关系，其相关系数可达0.972，表明九龙江河口区水体中的（238）u呈现保守行为。当S＝0时，溶解态（234）u/（238）u放射性比值为1.19和1.55（两份水样）；而当S＝0.90~21.97时，该比值＝1.02~1.14，分别呈现河水及河口水铀同位素组成的特征。对于颗粒态铀，其（238）u含量则介于0.50~9.83x10（-3）bQ/dM3，且随盐度的增大而呈逐步降低的趋势。九龙江河口区水体中（234）TH的地球化学行为属于非保守行为，不可逆稳态清除模型计算的结果表明，当盐度介于9.76~17.07时，（234）TH相对于化学清除的停留时间为6~19d，远低于盐度为0和21.97所对应的停留时间（分别为203d及117d），反映了在该盐度范围内，胶体絮凝沉降对溶解态234TH的快速清除作用国家自然科学基

Study on the Release Kinetics of Cr From Marine Dredged Materials With Oxalate Acid

采用恒温振荡实验装置,系统研究了有机酸草酸降解海洋疏浚物中重金属Cr的动力学过程。结果表明,恒温振荡6 H后,浓度为0.05--0.4 MOl/l的草酸可使Cr的释放百分率达到24%--44%。Cr的释放总体上可分为快速反应和慢速反应2个阶段,0--2 H为快反应阶段,解吸速率快,2--6 H后为慢反应阶段。草酸对Cr的释放动力学数据可用双常数方程很好的拟合,说明在草酸的存在下,疏浚物颗粒表面对Cr的释放可能更多表现出能量的不均匀性。温度升高时Cr的解吸量增加,反应速度加快,根据阿累尼乌斯公式估算出的活化能为26.53 kJ/MOl。The kinetic release behavior of heavy metal Cr from marine dredged material with oxalate acid solution is investigated by isotherm shaking device.The results show that the release percentage of Cr from dredged material with 0.05～0.4 mol/L oxalate acid in six hours reaches 24%～44%.The kinetic characteristics of heavy metal Cr is divided into two stage reactions of rapid and low desorption.When using oxalate acid as extracting solution,the data of release kinetics of Cr from dredged material conforms to the double constant equation,it implies that organic acid induced the energy uniformity of the release of Cr from dredged material.The amount of desorption increases and velocity of desorption speeds up with the increase of temperature.The activation energy calculated according to Arrhenius equation should be 26.53 kJ/mol.福建省科技重点资助项目(2004I001

Distribution of PCBs Concentrations in Dredged Materials of Xiamen Western Bay and Ecological Hazard Assessment

对厦门西海域拟疏浚物中的PCBs含量及分布特征进行了调查,结果表明,厦门西海域拟疏浚物中PCBs为0.17 ng/g～30.3 ng/g,其中马銮湾2个站位PCBs的总含量高于《海洋沉积物质量》(GB 18668-2002)一类标准值。生态风险评价结果显示厦门西海域拟疏浚物中多氯联苯的环境毒性相对较低。The concentration and distribution of PCBs in the dredged materials on the western bay of Xiamen were investigated.The results indicated the concentrations of the dredged material samples varied from 0.17 ng/g to 30.3 ng/g.The PCBs concentrations of all sampling sites were lower than the value of Category Ⅰ of Quality Standards for Ocean Sediment(State Standard 18668-2002)except two in the Maluan bay.The ecological risk assessment showed the relative low PCBs level in the Xiamen dredged materials was relative low toxicity to the environment.福建省科技重点基金资助项目(2004I001

Mechanisms controlling POC /~(234)Th ratios in marine particles

通过测定南海北部A1站四季上层500 M分粒径(1~10μM,10~53μM,>53μM)颗粒物上POC、234TH和228TH活度,发现中等粒径与大粒径的POC、234TH、228TH值比小粒径的POC、234TH、228TH低约一个量级。3种粒径POC/234TH(POC/228TH)比值的垂直分布皆呈现随深度增加而降低的趋势。统计分析POC/234TH、POC/228TH、234TH/228TH比值随粒径的变化,结果表明POC优先再矿化是影响POC/234TH比值变化的主要控制因素。The controlling factor of the POC /234 Th ratios has been the focus of the research in the POC export flux.We measured the POC concentrations,234 Th,and228Th activities on size-fractionated class particles in the upper 500 m at station A1 during four cruises to the South China Sea.Results show that POC concentrations,234 Th and228Th activities on the medium and large particles were lower than those on the small particles by about an order of magnitude.The depth profiles of POC /234Th( POC /228Th) showed decreasing trend with depth.By analyzing the POC /234 Th,POC /228 Th,234Th /228 Th ratios versus particle sizethe,we concluded that preferential remineralization of POC is the main factor of controlling POC /234 Th ratio in marine particles.国家重点基础研究发展计划973项目(2009CB421203):中国近海碳收支、调控机理及生态效应研

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

大洋溶解铁的物质来源及其同位素示踪

铁(Fe)作为海洋初级生产所必需的微量和限制性营养元素影响着海洋生物群落结构、生态功能以及碳循环,理解溶解Fe的物质来源及其对气候变化的响应具有重要的科学意义。早期研究多强调风尘输入是维持大洋Fe循环的主要机制。近年来,随着海水Fe分析数据的积累,尤其是痕量元素及其同位素海洋生物地球化学循环研究计划(GEOTRACES)的开展,陆架沉积物和热液活动所释放Fe的贡献开始越来越受到重视。尽管如此,不同物源对开阔大洋溶解Fe的影响依然存在相当的不确定性。以海水溶解Fe的化学组分为出发点,强调有机配体对大洋Fe循环的决定性作用,综述了不同来源Fe的通量估计和第四纪大洋Fe来源的研究争议。铁同位素为理解大洋Fe的物源演变提供了新的工具。讨论了不同物源的Fe同位素特征,并提出结合沉积物的活动性Fe同位素和组分研究可能为理解过去陆架-热液活动-风尘输出与输运Fe的机制提供全新视角。西太平洋地球系统多圈层相互作用重大计划培育项目“上新世以来西太平洋沉积铁同位素演化研究”(91858105)国家海洋局海洋沉积与环境地质重点实验室开放基金资助项目“晚第四纪北太平洋深水铁同位素演化重建:对大洋铁循环的新约束”(MASEG201711)青岛海洋科学与技术试点国家实验室海洋地质过程与环境功能实验室创新团队资助项目“利用西太平洋铁锰结壳微量金属重建新生代火山喷气历史”(MGQNLM-TD201701

How accurate are Th-234 measurements in seawater based on the MnO2-impregnated cartridge technique?

In the past decade, a MnO2-impregnated cartridge technique has been widely used to extract Th-234 from seawater. One of the inherent assumptions associated with this technique is that all Th species in the dissolved phase are subject to extraction by the MnO2 cartridges. In this study, an intercalibration between the cartridge technique and a small-volume MnO2 coprecipitation technique was carried out to test this assumption. We demonstrated that the collection efficiency for Th-234 could be substantially overestimated by the MnO2 cartridge technique. This may be the result of organic complexation of a significant portion of Th-234 in seawater, causing this fraction of Th to pass through the MnO2 cartridges. The overestimate in collection efficiency may explain the deep-water Th-234 deficit observed in some oceanographic settings (e.g., the Gulf of Mexico, the Middle Atlantic Bight, and the Gulf of Maine). Sensitivity tests show that using the cartridge technique can yield Th-234-based particulate organic carbon export rates that are overestimated by factors of up to 10. Furthermore, the frequent observed disagreements between Th fluxes recorded by shallow sediment traps and estimated using the cartridge method may be ascribed, at least partially, to this methodological issue

Glacial meltwater and sea ice meltwater in the Prydz Bay, Antarctica

Measurements of d D and salinity were carried out in the Prydz Bay during two Antarctic cruises, the 13th and the 14th Chinese National Antarctic Research expeditions (CHINARE). Mass balance calculations based on d D and salinity showed that during the 13th CHINARE cruise, per- centages of glacial meltwater and sea ice meltwater in the study region ranged from 0% to 3.82% and from 3.19% to 4.78%, respectively. Meanwhile, the percentages were 1.53%—3.98% and 3.80%—4.52% during the 14th CHINARE cruise. We dep..

A high-resolution study of particle export in the southern South China Sea based on Th-234 : U-238 disequilibrium

During a spring intermonsoon cruise in 2004, depth profiles of total and particulate Th-234 in the upper 100 m were collected at 36 stations in the southern South China Sea (SCS), covering a surface area of similar to 1.0 x 10(6) km(2). Thorium-234 was sampled by using a modified small-volume MnO2 co-precipitation technique, which allows mapping the Th-234 distribution with a high spatial resolution. A stratified structure of Th-234/U-238 disequilibria was generally observed in the upper 100 m water column, suggesting that the euphotic zone of the southern SCS in this season can be separated into two layers: an upper layer with low export production rates and a lower layer with high export production rates. At the same time, we observed extensive zones of Th-234 excess within the euphotic layer, which is possibly due to intense remineralization of particulate matter. Particulate organic carbon (POC) export was estimated from a three-dimensional steady state model of Th-234 fluxes combined with measurements of the POC/Th-234 ratio on suspended particles. The POC export for this region varied from a low of -10.7 +/- 1.5 mmolC m(-2) d(-1) to a high of 12.6 +/- 1.1 mmolC m(-2) d(-1), with an average of 3.8 +/- 4.0 mmolC m(-2) d(-1). A negative flux of POC export is interpreted as the result of lateral input of particulate matter from nearby waters. Regional patterns in POC export show enhanced fluxes along the western and southern boundaries of the study region, and a "tongue'' of low export extending northwestward from similar to 7 degrees N 116 degrees E to similar to 10 degrees N 111 degrees E. This geographic distribution is consistent with the overall surface circulation pattern of the southern SCS in this season