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.     

Upwelling and river runoff as sources of dissolved nitrous oxide to the Alsea estuary,Oregon

Surface waters of Alsea Bay, an unpolluted estuary on the Oregon coast, were analysed for nitrous oxide, nitrate and nitrite on a weekly or biweekly basis during the summer of 1979. The estuary was found to be a variable source of N₂O to the atmosphere. Large and rapid increases in the concentrations of N₂O, NO₃^?, and NO₂^? occurred at the beginning of the sampling period and are attributed to the influx of nutrient-rich upwelling water into the estuary with the tide. The subsequent decline in concentrations of nitrate, nitrite and nitrous oxide over the remainder of the summer is attributed to a decrease in upwelling intensity, a decline in nitrification rates and to assimilatory nitrate reduction. Measurements of nitrous oxide at six stations along the Alsea River were also made in September and October before and after the onset of the rainy season. Samples taken after flood conditions were established were systematically 50% higher than pre-flood samples. The data suggest that soil runoff results in elevated concentrations of N₂O in rivers.     

Nitrogen uptake,ammonium oxidation and nitrous oxide (N2O) levels in the coastal waters of western Cook Strait,New Zealand

Vertical measurements of $\text{NH}{}_4{}^{\mathrm{+}}$, $\text{NO}{}_3{}^{\mathrm{?}}$ and N₂O concentrations, $\text{NO}{}_3{}^{\mathrm{?}}$ and $\text{NH}{}_4{}^{\mathrm{+}}$ uptake, and $\text{NH}{}_4{}^{\mathrm{+}}$ oxidation rates were measured at 5 sites in western Cook Strait, New Zealand, between 31 March and 3 April 1983. Nitrate increased with depth at all stations reaching a maximum of 10.5 μg-atom $\text{NO}{}_3{}^{\mathrm{?}}\text{N l}{}^{\mathrm{?1}}$ at the most strongly stratified station whereas $\text{NH}{}_4{}^{\mathrm{+}}$ was relatively constant with depth at all stations (～0.1 μg-atom $\text{NH}{}_4{}^{\mathrm{+}}\text{N l}{}^{\mathrm{?1}}$). The highest rates of $\text{NH}{}_4{}^{\mathrm{+}}$ oxidation generally occurred in the near surface waters and decreased with depth. N₂O levels were near saturation with respect to the air above the sea surface and showed no obvious changes during 24 h incubation. $\text{NH}{}_4{}^{\mathrm{+}}$ oxidation by nitrifying bacteria may account for about 30% of the total $\text{NH}{}_4{}^{\mathrm{+}}$ utilization (i.e. bacterial+agal) and, assuming oxidation through to $\text{NO}{}_3{}^{\mathrm{?}}$, may supply about 40% of the algal requirements of $\text{NO}{}_3{}^{\mathrm{?}}$ in the study area. These results suggest that bacterial nitrification is of potential importance to the nitrogen dynamics of the western Cook Strait, particularly with respect to the nitrogen demands of the phytoplankton.     

一种腐屑食性鱼类对生态系统氮循环的影响

研究表明 :腐屑食性鱼类——梭鱼对环境中有机氮的摄入能力随体重的增加而增加 ,随温度的升高 ,体重系数显著减少。摄入氮 (CN,mg/ d)与体重 (W,g)和温度 (T,℃ )的数值关系可用如下模型表示 :CN=0 .6 370 W1 .0 642 ln(3.70 0 8T)。体重为 1 0 0 g的梭鱼每日可消耗环境中 332 mg氮有机质。梭鱼氮的吸收效率主要受温度的影响 ,而氮的转化效率与体重呈显著的正相关关系。随体重的增加 ,排泄氮所占比例降低     

Nutrient budgets and trophic state in a hypersaline coastal lagoon: Lagoa de Araruama, Brazil

Lagoa de Araruama in the state of Rio de Janeiro, Brazil, is a hypersaline lagoon with salinity varying spatially from 45 to 56. We collected water samples during monthly cruises throughout the lagoon, and along the streams feeding the system, from April 1991 to March 1992. Nutrients and other water quality parameters exhibited great spatial and temporal variations. Mass balance calculations indicate large amounts of anthropogenic nutrient inputs. The data indicate that the lagoon currently is oligotrophic but is in a state of transition to become a mesotrophic system. Molar dissolved inorganic nitrogen:dissolved inorganic phosphorus (DIN/DIP) varied between 2.2:1 and 659:1 with a volume-weighted average of 22:1. The high DIN/DIP ratio contrasts with that found in nearby lagoons, suggesting that phytoplankton primary production is limited by phosphorus in Lagoa de Araruama. The major loss of DIP is apparently driven by biological assimilation and diagenic reactions in the sediments. Calculations indicate that the lagoon is slightly net autotrophic at +0.9 mol C m⁻² yr⁻¹. This suggests that the biomass of the primary producers is restricted by phosphorus availability. Phosphorus retention in the sediment and the hypersaline state of the lagoon prevent changes in autotrophic communities and the formation of eutrophic conditions.     

Nutrient attenuation in a shallow,gravel-bed river. II. Spatial and temporal changes in nitrogen dynamics and community metabolism

ABSTRACT

Instream processes alter the concentration and bioavailability of nutrients as they are transported downstream. By relating primary production and periphyton composition to changes in nutrient concentration in a gravel-bed river this study made inferences about recycling and attenuation. Where dissolved inorganic nitrogen (DIN) was abundant, concentrations decreased linearly with distance but by less than required to meet the nitrogen demand of primary production. Where DIN was barely measurable photosynthesis was reduced but only by 50%. We infer that recycling sustained primary production even when DIN concentrations were negligibly small. One implication is that DIN removal underestimates attenuation. Further experimental research on recycling and improved modelling is required to better quantify the length of streams adversely affected by nutrients.     

Reactive Nitrogen Compounds at Spitsbergen in the Norwegian Arctic

Simultaneousindependent measurements of NO_y and NO_x(NO_x= NO + NO₂) by high-sensitivitychemiluminescence systems and of PAN (peroxyacetylnitrate) and PPN (peroxypropionyl nitrate) by GC-ECDwere made at Spitsbergen in the Norwegian Arcticduring the first half year of 1994. The average mixingratio of the sum of PAN and PPN (denoted PANs)increased from around 150 pptv in early winter to amaximum of around 500 pptv in late March, whereasepisodic peak values reached 800 pptv. This occurredsimultaneously with a maximum in ozone which increasedto 45–50 ppbv in March–April. The average NO_xmixing ratio was 27 pptv and did not show any cyclethrough the period. The NO_y mixing ratio showeda maximum in late March, while the difference betweenNO_y and PAN decreased during spring. This is anindication of the dominance of PAN in the NO_ybudget in the Arctic, but possible changes in theefficiency of the NO_y converter could alsocontribute to this. Although most PAN in theArctic is believed to be due to long range transport,the observations indicate local loss and formationrates of up to 1–2 pptv h^-1 in April–May.Measurements of carbonyl compounds suggest thatacetaldehyde was the dominant, local precursor ofPAN.Now at 1.     

An invariance in the carbazoles of petroleum

A remarkable invariance in the ratio of 1,3-dimethylcarbazole （DMC） to 1,6-DMC was discovered in crude oils from the Pearl River Mouth Basin, South China Sea. The remarkably invariant ratio is kept at a constant of about unity regardless of their concentrations, sources or maturities for the sampies. In combination with the molecular structures of 1,3- and 1,6-DMCs, the invariance might indicate that the nitrogen compounds share a common precursor with a skeleton of 1-methylcarbazole and are formed through methylation at C3 and C6 with an essentially identical rate.     

中国近海沉积物氮和有机碳标准物质的研制

我国海洋沉积物的研究近几年发展较快,但是缺少有定值的氮、有机碳标准物质。本文针对及其匮乏的氮、有机碳国家二级标准物质进行了我国近海沉积物总氮(TN)、总碳(TC)、总有机碳(TOC)含量的分析标准参考物质的研制。研究样品采自"我国近海海洋综合调查与评价"专项提供的表层沉积物,经过冷冻干燥、研磨至74μm,使用元素分析仪和氧化热解-气相色谱法分析总氮和总碳的含量;使用元素分析仪和氧化热解-电位法分析总有机碳的含量,制备了一系列16个有定值的总氮、总碳、总有机碳含量的近海沉积物标准物质。样品在均匀性检验中,F的实测值小于临界值,相对偏差较小,样品的均匀性较好。在稳定性检验方面,两年内多次测定的分析结果无方向性变化,统计计算结果显示稳定性良好。本文研制的这16个近海沉积物标准物质在3家实验室进行了联合定值,按照ISO导则35和国家一级标准物质研制规范,给出了该系列标准物质总氮、总碳、总有机碳含量的标准值和不确定度。这批标准物质分为不同海区,不同海区的标准物质又分为不同的沉积物类型,研制的不同海区不同沉积物类型的标准物质对现有的海洋沉积物标准物质进行了有效的补充。     

Analytical perspective on trace element species of interest in exploration

Analysis of soil and sediment samples, using selective extraction methods to distinguish different phases, is of particular interest in exploration geochemistry to locate deeply buried mineral deposits. There are various mechanisms of binding labile elements in the secondary environment, including physical and chemical sorption, precipitation, chelation and complexation. Phases present in soils and sediments which are likely to scavenge ‘free' elements include amorphous Mn and Fe oxides, the humic and fulvic components of humus, and clays. This paper reviews these forms of trace elements and the methods in current use to quantify them. Examples of precision data, both for control and survey samples, are given with respect to trace elements dissolved from the ‘soluble organic' component of humus, Mn oxides and amorphous Fe oxides. The high sensitivity of inductively coupled plasma mass spectrometry (ICP–MS) is required to measure accurately and precisely a large suite of trace elements, especially where only small fractions of elements are dissolved by such leaches as the commercially available Enzyme and MMI (Mobile Metal Ion) extractions. The relative standard deviations (RSD) obtained for 33 elements (e.g. Ag, Cd, In, I) in the standard reference sample (SRM), TILL-2, are in the range 0.5–8% for the hydroxylamine hydrochloride (NH₂OH·HCl) leach designed to extract hydrous Fe and Mn oxides. The corresponding RSDs for elements in the reactive Mn oxide phase extracted by the Enzyme leach are in the range 3–19% except for some trace elements at levels close to detection limit (e.g. Cd, Bi). The RSDs obtained for field duplicates are inferior to those for analytical replicates (i.e. sample splits), probably a reflection of different concentrations of the host phase. In one soil survey, the Fe extracted by a 0.25 M NH₂OH·HCl leach ranged conservatively from 0.2 to 1.7% whereas the Mn extracted by the Enzyme leach varied extensively, from 0.3 to >999 ppm. In contrast, precision, at 1–7% RSD, for field duplicates was found to be comparable with that for both analytical duplicates and the SRM, LKSD-4, for elements associated with the humic and fulvic component of humus samples sieved to <177 μm.