Improved chromatographic analysis of N:N ratios in ammonium or nitrate for isotope addition experiments

Estimating nitrogen transformation rates in aquatic ecosystems by isotope dilution techniques is simplified by directly measuring nitrogen isotopic ratios for NH₄⁺ in the water using high performance cation exchange liquid chromatography (HPLC). Modifications of HPLC conditions and implementation of a median-area method for retention time determination improved and linearized a previously reported sigmoid relationship between the retention time shift (RT_shift) of the NH₄⁺ peak and the ratio of [¹⁵NH₄⁺]: [Total NH₄⁺] in seawater fortified with ¹⁵NH₄⁺. Increasing the temperature of the HPLC column from 47 to 85 °C increased mobile phase buffer flow rate relative to column back pressure, decreased the retention time for NH₄⁺, and allowed the buffer pH to be optimized relative to the pK of NH₄⁺. The use of median-area rather than maximum-height to define the retention time of NH₄⁺ further improved the linearity (r > 0.995) of the relationship between the ratio [¹⁵NH₄⁺]: [Total NH₄⁺] and RT_shift over the range of isotope ratios. Reduction of NO₃⁻ to NH₄⁺ by adding zinc dust to acidified (pH 2) seawater or lakewater samples, followed by pH neutralization, and subsequent analysis of NH₄⁺ isotope ratios by HPLC, extended application of the method to isotope dilution experiments with NO₃⁻. Advantages of this direct-injection method over mass-measurement approaches traditionally used for isotope dilution experiments include small sample size and minimal sample preparation.     

Recovery of ammonium nitrogen by solvent extraction for the determination of relative 15N abundance in regeneration experiments

A new sample preparation method for ¹⁵N tracer measurement of ammonium regeneration in seawater is described. Ammonium nitrogen is incorporated into indophenol, extracted into dichloromethane and concentrated by evaporation. The isotopic ratio of the indophenol nitrogen is determined by emission spectroscopy. A small amount (0.2 μmol) of unlabeled nitrogen is introduced by reagents used during sample preparation. For samples of equal nitrogen content, the coefficient of variation is constant and the precision of the isotopic ratio determination is inversely related to the relative ¹⁵N abundance. Differences of 0.19 atom% ¹⁵N can be measured in 5.0 μM NH₄⁺ samples of 5.0 atom% ¹⁵N (SD = 0.07, n = 3, p = 0.05). Interface from forms of dissolved organic nitrogen prevalent in marine environments are negligible.     

A sampler for concentrating radionuclides from natural waters

A sampler which permits concentration of both particulate and dissolved radionuclides from large volumes of ocean and freshwater has been developed and tested. The water sample passes through a filtration section for particle removal, then through a sorption section where the radionuclides of interest are removed on sorption or ion exchange beds. Components of the sampler which contact the water are of polyvinyl chloride construction, and flow rates of about 40 l./min are employed. This sampler has been successfully employed in concentrating some twenty radionuclides from ocean and fresh waters.     

Water—rock partition coefficients and the composition of natural waters — A reassessment

Recent data on world average river water composition and global mean composition of crustal rocks have allowed a reconsideration of earlier work on the concept of a chemical steady-state in the world ocean system. In the light of these new data, initial statistical analyses have been reinterpreted or modified. This paper reports improved correlations between mean oceanic residence times ($\text{t}{}_{\mathrm{<mtext>Y</mtext>}}$) and water—rock partition coefficients (K_Y), and between K_Y and the electronegativity function (Q_YO). Such correlations support the concept that the average composition of seawater can be estimated, based on a simple dynamic model, using the electronegativities of elements and the rate of input of dissolved components.     

地下卤水中镭的富集与测定方法研究

以自配人工卤水,采用硫酸钡（镭）共沉淀法富集其中的镭,同时用γ谱仪同步测量^226Ra和^228Ra的含量。不同pH和共沉淀剂作用下的化学及放化回收率计算表明,该方法操作简单,回收率高,适用于地下卤水及其它水体较高含量^226Ra、^228Ra的同步测定。用该方法测定的莱州湾地下卤水^226Ra和^228Ra含量分别为0．341Bq／L和1．615Bq／L,远高于海水中镭的含量。     

Method for determining stable isotope ratios of dissolved organic carbon in interstitial and other natural marine waters

A procedure is described for the analysis of the stable carbon isotopic composition of dissolved organic carbon (DOC) in natural waters from marine and higher-salinity environments. Rapid (less than 5 min) and complete oxidation of DOC is achieved using a modification of previous photochemical oxidation techniques. The CO₂ evolved from DOC oxidation can be collected in less than 10 min for isotopic analysis. The procedure is at present suitable for oxidation and collection of 1–5 μmol of carbon and has an associated blank of 0.1–0.2 μmol of carbon.Complete photochemical oxidation of DOC standards was demonstrated by quantitative recovery of CO₂ as measured manometrically. Isotopic analyses of standards by photochemical and high-temperature sealed-tube combustion methods agreed to within 0.3.. Photochemical oxidation of DOC in a representative sediment pore-water sample was also quantitative, as shown by the excellent agreement between the photochemical and sealed-tube methods. The δ¹³C values obtained for pore-water DOC using the two methods of oxidation were identical, suggesting that the modified photochemical method is adequate for the isotopically non-fractionated oxidation of pore-water DOC.The procedure was evaluated through an analysis of DOC in pond and pore waters from a hypersaline microbial mat environment. Concentrations of DOC in the water column over the mat displayed a diel pattern, but the isotopic composition of this DOC remained relatively constant (average δ¹³C = −12.4.). Pore-water DOC exhibited a distinct concentration maximum in the mat surface layer, and δ¹³C of pore-water DOC was nearly 8. lighter at 1.5–2.0-cm depth than in the mat surface layer (0–0.5-cm depth). These results demonstrate the effectiveness of the method in elucidating differences in DOC concentration and δ¹³C over biogeochemically relevant spatial and temporal scales. Carbon isotopic analysis of DOC in natural waters, especially pore waters, should be a useful probe of biogeochemical processes in recent environments.     

海水中溶解态铵盐氮同位素分析的预处理方法

以蒸馏法为基础, 研究了适合海水中铵盐稳定氮同位素分析的预处理方法。对蒸馏法预处理过程中的最佳蒸馏时间、沸石的选取、铵盐最适浓度范围等分别进行改进和优化, 获得稳定、高效的海水中铵盐氮稳定同位素分析预处理方法。结果表明: 最佳蒸馏时间为50 min, 铵盐的回收率为(97±5.8)%。测定了不同沸石对不同浓度氨氮的吸附率, 筛选出酸性条件下铵氮吸附效率较高且稳定的康华科技沸石; 确定铵盐的最佳适用浓度范围为2～10 μmol/L, 在该浓度范围内氮回收率94%～99%,氮分馏系数为0.1‰～0.8‰。将此方法应用于长江口海域水样分析, 结果表明, 这一方法可以应用于河口中铵盐的氮同位素分析, 能够为河口中溶解态氮的来源及循环机理等研究提供有效信息。     

An improved gas chromatographic method for the measurement of hydroxylamine in marine and fresh waters

We present here an improved method for the analysis of hydroxylamine at nanomolar levels, which involves oxidation by Fe(III) and the subsequent measurement of nitrous oxide by electron-capture gas chromatography. The relationship between the pH and salinity of natural waters and the conversion of hydroxylamine to nitrous oxide by Fe(III) is defined, the rates of the reaction are evaluated, and the effects of dissolved O₂, Cu(II), and Hg(II) on the reaction are investigated. The method is linear to more than 300 nM and the standard deviation for a single measurement is 1 nM in the 0–40 nM range, thus exceeding the sensitivity of the spectrophotometric methods by almost an order of magnitude. This method eliminates the effects of pH and salinity that have burdened an earlier gas chromatographic approach, making possible the investigation of this labile substance not only in seawater, but in fresh and brackish waters as well.     

Redescription of the planktonic calanoid copepodAcartia hudsonica from Atlantic and Pacific waters: A new record from Japanese waters

The neritic planktonic copepodAcartia hudsonica is redescribed from the Atlantic and Pacific coasts of North America and newly from Japanese waters. This species formerly has been identified asA. clausi in the Northwest Pacific. The Atlantic and Pacific populations cannot be morphologically separated even in fine ornamentation; the variations found in the two populations overlap each other. Prosome length/width ratio of the female is negatively correlated with the body size and the ratio is not significantly different between Atlantic and Pacific females of the same size. The length/width ratio of the genital segment of Pacific females is positively correlated with their body size, and the mean value of the ratio for Atlantic females is smaller than that expected for Pacific females of the same size. The size-temperature relationship differs among localities but it is uncertain whether there is a genetic difference in copepod size between the Atlantic and Pacific populations.     

A rapid method for recovery of data from expendable surface current probes

A sighting device, called a “probe sight”, is described which simplifies the measurement, taken, from a helicopter, of the float separations from a deployed expendable surface current probe. The separation distance between the floats (along with a known time release) is a measure of the surface current speed. The sighting device can be used at any altitude. Comparisons of the readings using the probe sight and the “normal” measurements taken from aerial photographs for 180 stations in the Chukchi Sea, show that the difference between the two methods is less than 10% when the current speed is greater than 10 cm sec⁻¹. The largest difference (15%) occurs at those stations where the current speed is less than 10 cm sec⁻¹.     

Variations in the natural abundance of 15N in estuarine suspended particulate matter: A specific indicator of biological processing

In this study, the ¹⁴N:¹⁵N ratio of suspended particulate material collected from the Tamar river estuary, south-west England, is described. Three populations of particles, distinguishable by their ¹⁵N content, were observed. This investigation has shown that populations of estuarine particles are generated by biological transformations in situ and that the ¹⁵N content of estuarine particles does not merely reflect hydrodynamic mixing of the freshwater and seawater source particulate material.     

我国近岸海域富营养化评价新方法及应用

参考目前国际上被广泛应用的第2代富营养化评价方法体系,结合我国近岸海域生态环境特点和监测资料现状,建立了一种以压力-状态-响应模式为基本框架、以富营养化症状为主的第2代近岸海域富营养化评价体系。实际应用结果表明,应用本方法得出的长江口海域富营养化状况评价结论,与目前国外主流评价方法的评价结论一致,而且本方法具有评价指标代表性强、数据资料易得、评价标准有据、方法简便易行等优点。     

我国近岸海域富营养化评价新方法及应用

参考目前国际上被广泛应用的第2代富营养化评价方法体系,结合我国近岸海域生态环境特点和监测资料现状,建立了一种以压力-状态-响应模式为基本框架、以富营养化症状为主的第2代近岸海域富营养化评价体系。实际应用结果表明,应用本方法得出的长江口海域富营养化状况评价结论,与目前国外主流评价方法的评价结论一致,而且本方法具有评价指标代表性强、数据资料易得、评价标准有据、方法简便易行等优点。     

Assessment of dissolved nutrients dispersal derived from offshore fish-farm using nitrogen stable isotope ratios (δ15N) in macroalgal bioassays

In this study, the dispersal of wastes from offshore fish farms was evaluated by analyzing nitrogen stable isotope ratios (δ¹⁵N) in macroalgae incubated in the water column at sites located at an increasing distance from the fish cages. Bioassays were performed at three fish farms situated in separate localities with different nutritional conditions (Canary Islands, Murcia and Catalonia) and varying in size, species of fish reared and annual production. Macroalgal bioassays were carried out in two different directions (DI and DII) and they were replicated at each distance in order to evaluate the effect of small-scale variability on the spatial extent of fish farm wastes. The results obtained with δ¹⁵N contribute to a better understanding of the application of nitrogen stable isotopes ratios in macroalgae as an effective bioindicator for tracing the dispersion of offshore fish farm wastes, and demonstrate that fish farm wastes can be traced even over distances of some km from the pollution source. In the Canary Islands, the maximum distance obtained for detection of fish farm wastes was between 450 and 700 m. Of the three installations studied, Murcia presented the greatest distance for detection of fish farm waste influence, ranging from between 1550 and 2450 m, whilst in Catalonia this distance was less than 120 m. In Catalonia, the results were masked by the influence of other sources of nitrogen, and thus fish farm wastes were detected at more reduced distances than expected. These results confirm that fish farm wastes can be traced using the nitrogen stable isotope ratios of macroalgae and that this method can also be useful for identifying areas of potential risk to some sensitive ecosystems, and as an early signal that changes in the community structure might occur.     

A simple fractionation method for determination of phosphorus components in phytoplankton: Application to natural populations of phytoplankton in summer surface waters of Tokyo Bay

A simple procedure for fractionation of phosphorus components in natural populations of phytoplankton has been developed. By a combination of a trichloroacetic acid (TCA) extraction, a hot dilute acid treatment, a charcoal treatment and an organic solvent extraction, cellular phosphorus was divided into orthophosphate, nucleotide phosphorus, sugar phosphates, acid-soluble polyphosphates, lipid phosphorus, nucleic acid phosphorus, acid-insoluble polyphosphates, and residual phosphorus. The recovery of phosphorus was 94±5%. This technique was applied to natural populations of phytoplankton in summer surface waters of Tokyo Bay. Nucleic acid phosphorus and orthophosphate were most abundant, and accounted for 30 to 50% of total phytoplankton phosphorus. The nucleic acid phosphorus was proportional to the biomass of phytoplankton, irrespective of ambient nutrient concentrations. The orthophosphate showed the largest change in association with the change in cellular phosphorus content as well as in ambient phosphate. The orthophosphate serves as a phosphorus reserve in the natural populations of phytoplankton in summer surface waters of Tokyo Bay whereSkeletonema costatum was dominant. Acid-insoluble polyphosphates tended to increase when ambient concentration of phosphate was high, but their amounts were almost one order of magnitude lower than that of orthophosphate.     

北戴河养殖海域浮游植物的种类组成和时空分布特征

于2007年5-10月对北戴河养殖海域的浮游植物进行了网采调查,共鉴定浮游植物31属67种,其中硅藻门占绝对优势,计有23属54种,其次是甲藻6属11种,定鞭藻和绿藻各1属1种。统计分析结果显示,浮游植物种类组成及其优势种类的季节变化比较明显。浮游植物数量高峰出现在8月初,低谷出现在6月中旬,平均丰度为1135.10×104cell/m3。浮游植物多样性指数变化范围为0.088~2.332,平均为1.162;均匀度变化范围为0.034~0.788,平均为0.333。