共查询到20条相似文献，搜索用时 609 毫秒
1.
稀土元素已越来越多地应用于示踪各类地球化学体系的物质来源与岩石矿物形成等演化过程。但在进行海水样品的稀土元素检测时，由于样品的高盐特征和稀土元素的痕量特征又使得分析具有相当的挑战性。本研究旨在从高盐的海水基质中有效分离并富集痕量的稀土元素，同时结合电感耦合等离子体质谱（Inductively Coupled Plasma Mass Spectrometry, ICP-MS）技术对海水中的稀土进行定量分析。通过对海水样品稀土元素的定量限分析、加标回收实验和梯度加标回收实验，验证了方法的准确性，评估方法的分离富集效率。通过共沉淀过程中的pH比较、氢氧化钠与氨水作为共沉淀剂的比较，确定了富集过程中共沉淀剂用量、种类等影响因素。通过稀土元素配分曲线的绘制与类似样品结果进行比对，以及标准海水的检测结果，验证了方法在实际样品中的可行性。本研究探索了共沉淀富集法在分离富集海水中稀土元素的实验条件，实现高盐背景下痕量稀土的准确定量，并将其用于近岸海水与孔隙水的实际检测。 相似文献
2.
应用光学显微镜法对实验系统浮游植物进行了野外定量研究.测定了系统中浮游植物的种类组成和生物碳素变动,为模型有效性验证提供了野外数据;根据Ecopath能量平衡模型原理建立了海水养殖池塘浮游植物碳的计算机模型,初步确定了包括15个参数的浮游植物模块参数库,通过单因子分析法进行参数敏感性检验,确定了3个敏感性参数,并利用野外实际测定数据进行了模型验证.模拟结果表明本模型成功模拟了海水养殖系统浮游植物碳变动.在建模过程中,光限制因子与水温为影响浮游植物碳的主要内源因素,浮游动物捕食作用为外源影响因素. 相似文献
3.
海冰厚度是监测与研究渤海海冰的重要参数。为了获取更加可靠的渤海海冰厚度数据,本研究基于MODIS数据对海冰厚度反演中的冰水分离环节和冰厚计算方法都进行了改进。对于冰水分离环节,本文在Canny边缘检测算子提取海冰基础上,加入了二值化处理、阈值判别等步骤,实现了较高精度的渤海海冰范围自动化提取。通过试验确定了海冰厚度与反照率指数关系模型中的参数,包括海冰衰减系数和海水反照率参数,使其更加符合渤海海区的物理特征。将改进后算法的海冰厚度反演结果与渤海海上石油平台实测数据进行比较,并分析了误差来源。结果表明,经过对算法的改进,海冰厚度与反照率指数关系模型的反演结果与实测数据之间的平均绝对误差由7.05 cm缩小到2.74 cm,相关系数由0.434提高到0.485。 相似文献
4.
针对目前存在的海水水质受多因素影响、评价难的现状，提出了一种基于粒子群算法（PSO）优化误差反向传播（BP）神经网络的海水水质评价模型。该模型通过PSO得到BP神经网络最优的权值和阈值，结合青岛东部海域10个监测站点的数据得到水质评价结果。实验证明，该模型和单因子评价、传统的BP神经网络评价相比较，具有训练时间短、预测精度高的特点，在海水水质评价中具有良好的应用价值。 相似文献
5.
6.
7.
本研究以西太平洋表层海水为基质,制备了浓度为0.5～4.0μmol/L的海水活性磷酸盐系列标准物质。通过对所研制的4批次样品进行均匀性、稳定性评估,确定样品性能良好。对基于磷钼蓝分光光度法的气泡间隔连续流动分析系统的反应和操作条件进行优化,优化后的方法检出限低至0.03μmol/L。不同浓度样品的相对标准偏差为0.37%～2.45%(n=9);通过与国际已有有证标准物质比对,本研究方法测量误差小于0.05μmol/L。经6家具有中国计量认证资质且具备海水磷酸盐检测能力的实验室联合定值,确定了该系列标准物质的标准值,并对定值结果的不确定度进行了分析评价,相对扩展不确定度为2%～10%。 相似文献
8.
针对基于传统BP神经网络的海水水质评价模型存在易陷入局部极小等问题,提出了一种新的利用头脑风暴优化算法(BSO)优化BP神经网络的海水水质评价模型(BSO-BP)。该模型引入具有全局寻优特点的头脑风暴优化算法,用于模拟人类提出创造性思维解决问题的过程,具有强大的全局搜索和局部搜索的能力,同时利用BP神经网络所具有良好的非线性映射能力、学习适应能力和容错性,最大程度上考虑到海洋水质评价因素的非线性和非平稳的关系,得到BP神经网络的各层权值、阈值的最优解,使得海水水质评价结果准确合理。并以胶州湾海域的12个监测站位的监测数据作为评价样本进行水质评价,实验结果表明该评价模型能够克服局部极小问题,评价结果准确性较高,并具有一定的实用性。 相似文献
9.
10.
为得到适用于数值模拟的海底多金属硫化物材料本构模型,针对海底多金属硫化物试样进行了不同围压下的单/三轴压缩实验,得到物理力学特性参数,对比分析常用描述岩石物理力学行为的本构模型及岩石微元强度准则,选择了合适的材料本构模型并确定了相应参数,并通过单个单元的仿真验证了模型的正确性,且仿真结果表明当海水围压超过20~25MPa区间内的某特定值时,多金属硫化物将会产生明显的脆-延转化。进一步基于该模型开展了高围压条件下双截齿切削海底多金属硫化物数值模拟的动力学特性研究,仿真结果表明随着围压增大,截齿受到的截割阻力及进给阻力显著增大,载荷波动性降低。 相似文献
11.
建立了测定天然海水中硝酸盐氮同位素组成的蒸馏法,该方法主要是在碱性条件下利用戴氏合金将海水中的硝酸盐还原为氨,后利用稀盐酸吸收生产的氨,将得到的氨吸收液浓缩后干燥结晶,利用同位素比值质谱仪测定所得晶体的氮同位素组成。研究中开展了戴氏合金添加量及氨吸收溶液在不同条件下干燥结晶对氮同位素测值的影响研究。结果表明,戴氏合金添加量为3.0 g及60 ℃下直接干燥结晶为最佳的实验条件。所建立的氨蒸馏法氮空白值仅为(0.90±0.19) μmol,低于此前文献报道的氮空白值;氮同位素组成(δ15N)空白值为(-14.7±4.1)×10-3。运用所建立的氨蒸馏法实测得到的硝酸盐δ15N值与氨扩散法、硝酸盐直接测定法得到的数值非常吻合,进一步证明所建立氨蒸馏法的可靠性。改进后的氨蒸馏法适用于硝酸盐浓度在2~50 μmol/dm3内的天然海水硝酸盐氮同位素组成的测定,方法的标准偏差为±0.3×10-3。 相似文献
12.
The regeneration of pore water nutrients was studied and the contribution of benthic nutrient fluxes to the overlying water
was evaluated on the basis of field specific observations conducted in September–October 1998 and April–May 1999 in the Bohai
Sea. Nutrient concentrations in sediment pore waters were examined by incubating sediment core samples with overlying seawater
in air and/or nitrogen conditions. Nutrient diffusion fluxes calculated by diagenetic equations were within a factor of 2
during incubations. The factors affecting nutrient diffusion across sediment/water interface include bioturbation, nitrification,
denitrification, adsorption, and dissolution. The regeneration of nutrients from sediments will increase nutrient loads of
the Bohai Sea and affect nutrient atomic ratios in this region. Among nutrient sources from riverine input, atmospheric deposition
and sediment regeneration, ammonium and phosphate mainly came from atmospheric deposition (>50%); nitrate was mainly transported
by riverine input into the Sea, silicate from sediment regeneration accounts up to 60%. This demonstrates that nutrient regeneration
in sediments contributes more silicate than riverine input and atmospheric deposition together, but benthic flux contributes
very much less phosphate and nitrate relative to riverine input and atmospheric deposition. The benthic fluxes of nutrients
may lead to a decrease of the amount of nitrate, an increase of phosphate, ammonia and silicate in the water column. The release
of silicate from sediments may compensate the decrease of silicate due to the reduction of riverine discharge. Nutrient regeneration
in sediment may have an important influence on the eutrophic character of coastal waters in this region.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
13.
A direct, spectrophotometric method has been adapted for quantitative determination of nitrate concentrations in seawater. The method is based on nitration of resorcinol in acidified seawater, resulting in a color product. The absorption spectrum obtained for the reaction product shows a maximum absorption at 505 nm, with a molar absorptivity of 1.7 × 104 L mol− 1 cm− 1. This method has a detection limit of 0.5 μM and is linear up to 400 μM for nitrate. The advantage of this method is that all reagents are in aqueous solutions without involving cadmium granules as a heterogeneous reactant, as in conventional methods, and therefore is simple to implement. Application of the resorcinol to seawater analysis demonstrated that the results obtained are in good agreement with the conventional approach involving the reduction of nitrate by cadmium followed by diazotization. 相似文献
14.
A method has been developed for determination of15N isotope ratio in nitrate nitrogen, which is a major analytical step in tracer experiments for studies of nitrate metabolism
in the marine environment. The method is based on diazotization of nitrite with sulfanilic acid following reduction of nitrate
to nitrite by a cadmium-copper column. The diazonium compound is then subject to the azo coupling reaction with 2-naphthol,
and the azo dye formed is extracted by a solid phase extraction column. The dye eluted from the column is collected, and total
nitrogen and15N content of the dye are determined by mass spectrometry. Sulfanilic acid can also remove preexisting nitrite by heating the
sample under acidic conditions before passing through the cadmium-copper reduction column. The average recovery of nitrate
nitrogen was 86%. A procedure for reducing the background nitrogen that derives from the analytical operations has been developed;
background nitrogen was limited to about 0.25 μg-atomN. The variation in the background nitrogen levels reflects the range of error in15N determination of nitrate nitrogen by this method. Application of the present method to a15NO3
− isotope dilution experiment for determination of nitrification rate in sea water is demonstrated. 相似文献
15.
Measurements of nitrogen fixation (acetylene reduction) showed greatest rates in the saltmarsh pans with a benthic layer of cyanobacteria present. The smallest amount of nitrogen fixation occurred on the marsh surface where a Puccinellia maritima/Halimione portulacoides plant association shaded the underlying sediment. Phototrophic nitrogen fixation was always greater than dark, chemotrophic, bacterial fixation.Only a small proportion of the total amount of ammonium, which was formed during detrital breakdown, was nitrified to nitrate. Although there is a high capacity for bacterial nitrate reduction in these sediments, the process is limited by low nitrate availability and most nitrate upon reduction is converted to ammonium rather than being denitrified to gaseous products. Denitrification does not, therefore, result in any great loss of nitrogen from the saltmarsh.There was little net import or export of nitrogen on an annual basis, although nitrate and organic-N in small particulate material was removed from tidal water by the marsh, and there was net annual export of ammonium, dissolved organic-N and organic-N in large particulate material. Losses of nitrogen by the small net tidal export and by denitrification were approximately balanced by nitrogen fixation. It was concluded that the nitrogen cycle of the Colne Point saltmarsh was balanced on an annual basis, with most nitrogen being recycled within the marsh. The saltmarsh did not apparently act as a net source of nitrogen for the adjacent estuary, although it may act as an important processor of nitrogen, removing some forms of nitrogen such as nitrate from tidal water while exporting other forms of nitrogen such as dissolved organic-N. 相似文献
16.
An automatic flow analysis system with on-line liquid nitrogen trap, hydride generation and flame-less atomic absorption spectrophotometry was presented for the determination of inorganic arsenic and antimony in seawater. The experimental conditions such as acidity of reduction reaction, the amount of sodium borohydride , the flow rate of carry gas (high purity of nitrogen) were tested and selected optimally. The limit detection of the method presented was 0. 15 ug/L for arsenic and 0. 24 μ/L for antimony . During the determination of seawater samples with levels microgram arsenic and antimony pa litre th?variation coefficient would be ±4% for arsenic and ±10% for antimony. The volume needed for one measurement was 9 mL for arsenic and 12 mL for antimony. The frequency of sample determination reached 20 times per hour for arsenic and 15 times per hour for antimony. 相似文献
17.
18.
离子色谱-电感耦合等离子体质谱联用测定海水中的IO3^-和I^- 总被引：1，自引：0，他引：1
研究了离子色谱-电感耦合等离子体质谱（IC-ICPMS）联用技术直接进样测定海水中IO3^-和I^-的方法．采用IonPacAG23离子色谱保护柱分离IO3^-和I^-，以浓度4．0mmol／dm3的KOH为流动相，流量为1．0cm3／min，每个样品的分析时间为2．5min．采用2．5×10^-3cm^3的进样量，IO3^-和I^-的检出限分别达到0．6和0．4nmol／dm2，可满足海水中碘形态的定量分析．该方法的IO3^-和I^-浓度范围在2．0nmol／dm3～2．0μmol／dm3． 相似文献
19.
A chemiluminescent technique for the determination of nanomolar concentrations of nitrate and nitrite in seawater 总被引：1，自引：0，他引：1
C. Garside 《Marine Chemistry》1982,11(2):159-167
A chemiluminescent analysis technique for the determination of nanomolar quantities of nitrate, nitrate plus nitrite or nitrite alone in seawater is described. The method depends on the selective reduction of these species to nitric oxide which is then determined by its chemiluminescent reaction with ozone, using a commercial nitrogen oxides analyzer. The necessary equipment is compact and sufficiently sturdy to allow shipboard use. A precision of ±2 nM is claimed with analytical rates of 10–12 samples h?1, and modifications are discussed to allow doubling the analytical rate. 相似文献
20.
Modified Method for the Analysis of Nitrogen Isotopic Composition of Oceanic Nitrate at Low Concentration 总被引：1，自引：0，他引：1
A method for the determination of the δ15N of nitrate in seawater described by Cline and Kaplan (1975) has been modified for application to low-level nitrate samples.
We have minimized the reagent blank problem by replacing the Devarda's alloy with an aluminum reagent, and have also established
a procedure that yields quantitative (93 ± 2%) extraction of nitrogen even at low nitrate levels. Though the amounts and the
δ15N of the blank N varied from one reagent set to another, with these modifications, an overall N blank was reduced to approximately
0.80 ± 0.33 μmole N having an estimated δ15N value of −1.8‰. After blank and yield corrections, the measured isotopic composition of nitrate differed by approximately
0.1‰ from the actual value while the precision was within ±0.2‰ at the 1.25 μM level. The modified procedure was applied to
seawater samples collected from the equatorial Pacific in order to compare the N blanks in field samples with those derived
from laboratory experiments. The results support the suitability of the modified approach for isotopic analysis of oceanic
nitrate in shallow water.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献