Errors in sampling procedure for the determination of dissolved oxygen by Winkler method

Sources of systematic error in the sampling procedure by Winkler method were examined. In the laboratory experiment, the dissolution of atmospheric oxygen into oxygenfree sea water during sampling amounts to 0.022 ml/l, and the effect of dissolved oxygen in sea water remaining in oxygen bottle is 0.019 ml/l. The effect of reagents added amounts to 0.017 ml/l. In the sampling procedures aboard, the effect of dissolution became bigger, and the table is presented for the correction to the reported value of dissolved oxygen measured by the “Manual of Oceanographic Observation”. The corrected value of dissolved oxygen in the routine analysis may not be correct within 0.02 ml/l.     

Nutrient maximums related to low oxygen concentrations in the southern Canada Basin

The phenomenon of nutrient maximums at 70～200 m occurred only in the region of the Canada Basin among the world oceans. The prevailing hypothesis was that the direct injection of the low-temperature high-nutrient brines from the Chukchi Sea shelf (＜50 m) in winter provided the nutrient maximums. However, we found that there are five problems in the direct injection process. Formerly Jin et al. considered that the formation of nutrient maximums can be a process of locally long-term regeneration. Here we propose a regeneration-mixture process. Data of temperature, salinity, oxygen and nutrients were collected at three stations in the southern Canada Basin during the summer 1999 cruise. We identified the cores of the surface, near-surface, potential temperature maximum waters and Arctic Bottom Water by the diagrams and vertical profiles of salinity, potential temperature, oxygen and nutrients. The historical 129Ⅰ data indicated that the surface and near-surface waters were Pacific-origin, but the waters below the potential temperature maximum core depth was Atlantic-origin. Along with the correlation of nutrient maximums and very low oxygen contents in the near-surface water, we hypothesize that, the putative organic matter was decomposed to inorganic nutrients; and the Pacific water was mixed with the Atlantic water in the transition zone. The idea of the regeneration-mixture process agrees with the historical observations of no apparent seasonal changes, the smooth nutrient profiles, the lowest saturation of CaCO3 above 400 m, low rate of CFC-11 ventilation and 3H-3He ages of 8～18 a around the nutrient maximum depths.     

An automated precise Winkler titration for determining dissolved oxygen on board ship

An automated titration for the Winkler method is presented for measuring primary productivity in the ocean. The system is based on a microcomputer-controlled titration with potentiometric endpoint detection. By the use of 0.005-N sodium thiosulfate as a titrant and a program designed to shorten the time for measuring, the method achieves a precision of 0.04% coefficient of variation with a range of 0.01 to 0.10% for six replicates of samples at oxygen concentration of 70 to 250 M. It takes about four to five minutes to measure one sample.     

A chemiluminescent technique for the determination of nanomolar concentrations of nitrate and nitrite in seawater

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.     

Expendable ampoules for oxygen determination

A new technique for adding Winkler reagents to water samples at sea has been developed. Expendable ampoules containing the reagents replace syringes or pipettes. The main features of the ampoules are simpler handling and safer sampling with preserved accuracy.     

化学发光法测定天然水体中低浓度硝酸盐和亚硝酸盐的含量

传统分光光度法测定硝酸盐和亚硝酸盐含量时检测限较高,无法测定部分海洋表层及寡营养盐海域低含量的硝酸盐和亚硝酸盐浓度,急需采用一种新的测定低浓度硝酸盐和亚硝酸盐的方法.化学发光法用于测定水体中硝酸盐和亚硝酸盐含量,具有灵敏度高、检测限低、样品用量少,不受悬浮颗粒物、有色物质影响及样品批量测定等优点.本文通过探索载气流速、...     

Measuring low concentrations of Th in water and sediment

²³⁴Th/²³⁸U disequilibria have been used extensively in studies of particle dynamics and the fate and transport of particle-reactive matter in marine environments. Similar work in low salinity, estuarine, and freshwater systems has not occurred primarily because the lower concentrations of both parent and daughter nuclides that are typical of these systems often render established methods for the analysis of ²³⁴Th inadequate. The application of this radionuclide tracer technique to these systems, however, has great potential. To this end, we present a method for measuring low activities of ²³⁴Th in relatively small samples (<200 l) using low background gas-flow proportional counters, a ²²⁹Th yield monitor, and empirical corrections for the interferences from real and apparent betas that are emitted by other thorium isotopes and their progeny. For samples with low ²³⁴Th/²²⁸Th activity ratios, we improve upon current beta counting methodologies that rely on immediate sample counting, weak beta absorption, or multiple beta counts so that, using the analytical approach outlined here, it should be possible to measure ²³⁴Th activities (i) as low as 1.5 dpm/total sample, (ii) up to 2 weeks after radiochemical purification of thorium, and (iii) with only one sample count for alpha and beta activity.     

A study of metal ion adsorption at low suspended-solid concentrations

A procedure for conducting adsorption studies at low suspended solid concentrations in natural waters (<50 mg l⁻¹) is described. Methodological complications previously associated with such experiments have been overcome. Adsorption of zinc ion onto synthetic colloidal titania (TiO₂) was studied as a function of pH, supporting electrolyte (NaCl) concentration (0·1-0·002 m) and particle concentration (2–50 mg l⁻¹). The lack of success of the Davis Leckie site bonding model in describing Zn(II) adsorption emphasizes the need for further studies of adsorption at low suspended-solid concentrations.     

海水中低浓度亚硝酸盐和硝酸盐测定方法综述

海水中低浓度的亚硝酸盐和硝酸盐的测定方法主要有4种,即分光光度法(富集分光光度法和液芯波导分光光度法)、高效液相色谱法、荧光法和化学发光法。这些测定方法比传统的分光光度测定法有更高的灵敏度和更低的检测限,可以对海水中纳摩尔级低浓度的亚硝酸盐和硝酸盐进行测定。化学发光法和液芯波导分光光度法的自动化程度高,测定时对样品的需求量少,后者还实现了多个参数的实时现场测定,因而成为目前海水中低浓度亚硝酸盐和硝酸盐测定的主流方法,具有广阔的应用前景。     

Colorimetric determination of nanomolar concentrations of ammonium in seawater using solvent extraction

A solvent extraction method for measuring nanomolar concentrations of ammonium in seawater is described. The procedure is based on formation of indophenol in alkaline solution by reaction of phenol, hypochlorite and ammonia using sodium aquopentacyanoferrate as a coupling agent. Indophenol is then concentrated by extraction into n-hexanol at low pH and re-extraction into aqueous alkaline buffer. The concentration of indophenol blue is determined colorimetrically. The molar absorbance is 2.08 × 10⁵ absorbance units per molar NH₄⁺ in seawater with a precision of ± 1.9 nM NH₄⁺ (95% Cl) for concentrations ≤ 50 nanomolar. This represents a 12-fold improvement in sensitivity and a 26-fold improvement in precision over standard aqueous analyses. Calibration curves are linear to at least 2 μM NH₄⁺. Sensitivity in seawater is 97% of that found in deionized distilled water due to a slight salt effect.     

A low sidelobe technique for the direct measurement of scatteringfunctions

Effective communication and echolocation depends strongly upon the coherence of the channel through which the signal is propagated. Under certain conditions, the average coherence or equivalently, the spreading of a random channel may be described by a scattering function (SF). This represents a second order (energy) measure of the average delay, Doppler, and more generally, the spatial (azimuthal) spread that the signal experiences. The SF is analogous to the point spread function (PSF) discussed in the image processing literature and likewise describes the amount of “blurring” imposed upon the signal or scene transmitted. The SF will be briefly reviewed and its measurement by both direct (high resolution channel probing) and indirect (deconvolution) methods will be discussed. A new direct method using specially designed waveform pairs and a twin or uncertainty product (UP) receiver structure is introduced. Unlike high resolution matched filter implementations for direct probing that are limited by the fixed volume constraint of ambiguity functions, the UP receiver produces vanishing sidelobes and hence more nearly approximates a desirable two-dimensional delta characteristic. The improvement gained in SF measurement is illustrated by the results of an experiment in which the UP receiver and traditional matched filter implementations were used to directly probe an ocean multipath channel     

Possible reasons for low climate-model sensitivity to increased carbon dioxide concentrations

The sensitivities of two climate-model versions—INMCM4 which participated in the Coupled Model Intercomparison Project, Phase 5 (CMIP5), and a new INMCM5 version with increased vertical and horizontal resolutions in its atmospheric block—to the quadrupled concentration of CO₂ are studied. When the CO₂ concentration is quadrupled, the equilibrium increase in surface temperature amounts to about 4.2 K for INMCM4, which is lower than that for other models that participated in the CMIP5. When the CO₂ concentration increases, the cloud radiative forcing in the model decreases; in this case, one portion of this decrease occurs during the first year after the concentration of CO₂ is quadrupled and the other portion almost linearly depends on the value of global warming. The results of additional numerical experiments with the model show that a rapid decrease in cloud-radiative forcing results from variations in stratification in the atmospheric surface boundary layer and associated increased cloudiness. The portion of a linear decrease in cloud-radiative forcing with increased temperature is associated with an increase in the water content of model clouds at higher temperatures. The elimination of these two mechanisms allows one to increase the model sensitivity to the quadrupled concentration of CO₂ up to 5.2 K.     

不同高分辨率遥感图像融合技术特征比较

简要回顾了图像融合技术的起源和发展情况。对图像融合的概念与基础理论作了阐述,剖析了其优缺点和使用领域。通过6种融合方法对杭州市滨江区QuickBird正射影像及数字化地形图进行了融合,并对融合图像进行了效果评价,结果表明,所有融合图像的方差和熵都大于配准后的图像,融合后图像的信息量大为增加。     

一种改进的温克勒海水溶氧分析方法

本文推荐了一种改进的温克勒（Winkler1888)海水溶解氧的分析方法，并介绍了该方法的基本原理、仪器设备、分析和计算方法等。由于这种改进的分析方法在六个方面作了较大的技术改进，其分析精密度与分析准确度都有了较大的提高。大量的实验数据表明，改进方法的海水溶氧测定精密度约为经典方法精密度的3－5倍，溶氧测量准确度也比经典方法提高了0．8％。本方法可以作为海水溶氧观测仪器计量校准的标准分析方法使用。     

海水中低含量铵氮的高灵敏度荧光法测定

提出了一种改进的、可测定海水中低含量铵氮的高灵敏度荧光分析方法。其原理是在硼酸缓冲溶液的作用下,海水中的铵氮与邻苯二甲醛(OPA)发生衍生化反应,通过测定生成的荧光产物来确定水体中铵氮的浓度。方法的检测限极低(0.002 5μmol/L),重现性好,且水样用量少(10 mL),适用于海水中溶解有机物的光铵化研究及其他低铵含量水样的测定。     

Preliminary research on dissolved oxygen maximum of seawater in low latitude of China

-During the multi-disciplinary investigations on the waters of Nansa Islands for three cruises respectively in 1985. 1986. 1987. it is found that the dissolved oxygen maximum (DOmax) in its vertical distribution usually exists between 20m and 75m deep. The deep position of O2 maximum is near the thermocline below and above the deep chlorophyll maximum, as well as above the light-beam attenuation coefficient maximum. In the parts of O2 maximum occurring, the minimum of CO2 partial pressure and the maximum of pH value are also found at the same depth. It is still difficult to explain the features exactly by using the published research results about the oxygen maximum in its vertical distribution on the waters of middle and high latitude.In the present paper, the dissolved oxygen maximum in its vertical distribution on the waters of low latitude is described. It is made by an internal wave which holds eddy mixture. The feature appears to arise from the biological photosynthesis with stratification, from t     

Mesozooplankton of the Arabian Sea: Patterns influenced by seasons, upwelling, and oxygen concentrations

The intensive study of the Arabian Sea during the 1990s included mesozooplankton investigations by the Netherlands, United Kingdom, Pakistan, India, Germany and the United States. Several major discoveries resulted. First, the high biomass of mesozooplankton observed during the Northeast Monsoon season is sustained by primary productivity stimulated by convective mixing and by an active microbial loop. The apparent ‘paradox’ of high standing stocks of mesozooplankton coinciding with low standing stocks of phytoplankton thus was resolved. Second, the Southwest Monsoon (upwelling) season supports a burst of mesozooplankton growth, much of which is exported to the interior of the Arabian Sea by strong currents and eddy activity and to depth at the end of the season when diapause causes at least one very abundant copepod to leave the epipelagic zone. Third, the oxygen minimum zone severely restricts the vertical distribution of mesozooplankton in the eastern region of the Arabian Sea. The copepod that withstands conditions in the OMZ most readily, Pleuromamma indica, has increased in abundance over the past thirty years suggesting the OMZ may have grown in size and/or intensity in that time. Fourth, the Fall Intermonsoon and Northeast Monsoon seasons are characterized everywhere by increased abundance of the cyclopoid copepod genus, Oithona. Abundances of Oithona measured in the 1990s are much higher than those of the 1930s, suggesting food web alterations over the past half-century.