Automatic colorimetric analyzer prototype for high frequency measurement of nutrients in seawater

This paper describes the characteristics of a prototype of a modular multiparametric analyzer (MicroMAC FAST MP3) for automatic monitoring of seawater and analytical methods for nutrients.The MicroMAC FAST reactor is an evolution of the basic LFA (Loop Flow Analysis) reactor. It has been conceived to assay ammonium, nitrate–nitrite and orthophosphate at low concentration in seawater samples. A sample analysis is 3–4 times faster than that obtainable with a standard LFA reactor. With respect to the previous analyzer a temperature control (30–52 °C) on the measurement cell has been added (only for modules NH₄ and PO₄), while the colorimeter and the related links for transporting the sample have been moved beyond the Loop and form a hydraulic-optical set almost completely independent from the main LFA. All the steps of a wet-chemical colorimetric analysis method are carried out in an analysis cycle sequentially. The hermetic closed Loop provides full protection against background interference, which is a basic requirement for stable trace analysis. At the start of a cycle the loop is washed and filled with sample. The sample color is measured for compensation. Small amounts of concentrated reagents are added and mixed with high intensity. This new technique allows the preparation of two products of reaction which can be introduced at intervals of 150 s in the measurement cell. The intensity of the color of the reaction product is measured on the colorimeter using a monochromatic light beam of specific wavelength. The statistical test shows that the results of automated and manual analyses agree for all the examined parameters. Precision of all three analyses is ≤ 4% RSD.Multiparametric online analyzer: it is possible to connect the analytical modules to a data logger with analogue and digital signals, in order to have online simultaneous analysis of the sample. A typical application is used during research at sea which vessel does not require an operator.     

中空纤维气态膜法回收稀氨水中氨制取硝酸铵的研究

针对合甲醇的稀氨水,用中空纤维气态膜法回收氨制取硝酸铵,甲醇对回收氨及制取硝酸铵的过程无不良影响。聚丙烯中空纤维在料液中长期浸泡强度无明显降低,物理性能是稳定的。     

Simulated Ground Deposition Of Fine Airborne Particles In An Array Of Idealized Tree Crowns

Wind-tunnel experiments were used to investigate the ground deposition of fine airborne particles in an array of idealized tree crowns. The particle ground deposition was modelled with a gaseous tracer instead of solid particles, which is an approach for very fine particles. A chemical method based on the reaction of ammonia and manganese chloride was used to quantify the mass transfer from the simulated atmospheric boundary-layer flow to the surface. Using a tracer gas instead of solid particles can be considered only if turbulent diffusion is the decisive deposition mechanism and effects of sedimentation, impaction, interception or molecular diffusion can be approximately ignored. These constraints are necessary due to scaling problems concerning particle modelling in the small-scale experiment. The intention was to determine the obstacle arrangement density in which the mean ground deposition is maximized for a defined crown form. A deposition amplification factor was defined as the quotient of deposition efficiencies for an area with tree crowns and an open ground with identical similarity parameters. Based on this calculation an increase of the ground deposition by up to 60% should be realistic through a favourable arrangement of tree crowns and tree number density. An increase in turbulence intensity in the flow leads to a significant amplification of the mean ground deposition.     

Development of guidelines for ammonia in estuarine and marine water systems

The water quality guideline trigger value for ammonia in estuarine and marine waters has been revised with the addition of 38 new results to the data set of 21 used in earlier guideline derivations. Using species sensitivity distributions, a new trigger value of 460 μg total NH₃-N/L was derived for slightly to moderately disturbed systems (95% protection concentration, PC95), with a value of 160 μg total NH₃-N/L applying to waters of high conservation value (PC99). For sediment pore waters, a guideline trigger value of 3.9 mg total NH₃-N/L, derived from the 80th percentile of background data from Sydney Harbour, is recommended. This value is likely to be exceeded in degraded sediments subject to dredging; however, ocean disposal of such sediments results in rapid decreases in porewater ammonia and a guideline trigger value for dissolved ammonia during disposal of dredged sediments of 1550 μg total NH₃-N/L is proposed.     

不同温度和盐度对大竹蛏耗氧率和排氨率的影响

在实验室条件下,设置12、17、22、27和32℃五个温度梯度和12、17、22、27和32五个盐度梯度,研究了不同温度和盐度对大竹蛏(Solen grandis)耗氧排氨的影响。结果表明:随着温度的升高耗氧率先降低再逐渐升高,在温度为22℃时为最小值1.571 mg/(g·h);排氨率先降低后升高再降低,在温度17℃时为最小值0.127 mg/(g·h)。随着盐度增加耗氧率先升高后降低,在盐度22时达到最大值3.106 mg/(g·h),排氨率先降低再升高,在盐度为27时为最小值为0.145 mg/(g·h)。在盐度32时,不同温度的O:N范围是5.525~79.037。在温度12℃时,不同盐度下的O:N范围是4.378~16.755。不同温度下耗氧率Q_(10)变化范围为1.054~2.421,排氨率的Q_(10)变化范围是0.748~1.256。研究结果为进一步完善大竹蛏的人工养殖技术提供参考。     

皱纹盘鲍排氨率变化特征及代谢产物对水质的影响研究

为研究不同规格皱纹盘鲍(Haliotis discus hannai Ino)的排氨率变化特征和代谢产物对养殖水质的影响,于鲍摄食后的3、6、9、12、18、24 h时取水样对主要水质因子的变化情况进行测定,并根据总氨氮(TAN)浓度计算各规格组鲍的排氨率。实验结果表明,随着鲍体质量的增加,TAN浓度也随之增加(P0.05),大规格组和小规格组中TAN浓度均在9 h时出现第一个波峰。大、中、小规格组鲍的单位体质量排氨率最大值依次为16.79、29.96、48.56μg/(g·h)。且小规格组鲍的排氨率显著高于大、中等规格组(P0.05),各规格组中的NO_2~–-N和PO_4~(3–_-P浓度均在24 h时达到最大值,且除0 h外,大规格组中的NO_2~–-N和PO43–-P浓度均显著高于中、小规格组(P0.05)。9 h时,大规格组中的NO_3~–-N浓度达到最大值,而中等规格组则在24 h时达到最大值。18 h时,中等规格和小规格组COD均达到最大值,而大规格组则是在24 h时浓度达到最大。因此,基于皱纹盘鲍的排氨率变化特征和TAN等在水体中的累积情况,可以预测水质变化规律并根据实际情况及时采取换水等相关操作,对促进养殖生物健康生长、降低病害发生风险、提高养殖效益等均有借鉴意义。     

Modeling nitrogen–carbon cycling and oxygen consumption in bottom sediments

A model framework is presented for simulating nitrogen and carbon cycling at the sediment–water interface, and predicting oxygen consumption by oxidation reactions inside the sediments. Based on conservation of mass and invoking simplifying assumptions, a coupled system of diffusive–reactive partial differential equations is formulated for two-layer conceptual model of aerobic–anaerobic sediments. Oxidation reactions are modeled as first-order rate processes and nitrate is assumed to be consumed entirely in the anoxic portion of the sediments. The sediments are delineated into a thin oxygenated surface layer whose thickness is equal to the oxygen penetration depth, and a lower, but much thicker anoxic layer. The sediments are separated from the overlying water column by a relatively thin boundary layer through which mass transfer is diffusion controlled. Transient solutions are derived using the method of Laplace transform and Green’s function, which relate pore-water concentrations of the constituents to their concentrations in the bulk water and to the flux of decomposable settling organic matter. Steady-state pore-water concentrations are also obtained including expressions for the extent of methane saturation zone and methane gas flux. A relationship relating the sediment oxygen demand (SOD) to bulk water oxygen is derived using the two-film concept, which in combination with the depth-integrated solutions forms the basis for predicting the extent of oxygen penetration in the sediment. Iterative procedure and simplification thereof are proposed to estimate the extent of methane saturation zone and thickness of the aerobic layer as functions of time. Sensitivity of steady-state solutions to key parameters illustrates sediment processes interactions and synergistic effects. Simulations indicate that for a relatively thin diffusive boundary layer, d, oxygen uptake is limited by biochemical processes inside the sediments, whereas for a thick boundary layer oxygen transfer through the diffusive boundary layer is limiting. The results show an almost linear relationship between steady-state sediment oxygen demand and bulk water oxygen. For small d methane and nitrogen fluxes are sediment controlled, whereas for large d they are controlled by diffusional transfer through the boundary layer. It is shown that the two-layer model solution converges to the one-layer model (anaerobic layer) solution as the thickness of the oxygenated layer approaches zero, and that the transient solutions approach asymptotically their corresponding steady-state solutions.     

Reduction of Ammonia and Hydrogen Sulfide Emission from Swine Manure Using Aqueous Foams Amended with Microorganisms and Chemical Additives

Aqueous foam, in combination with microorganisms and chemical additives, was tested for the reduction of the emissions of odorous compounds from swine manure. Ammonia and hydrogen sulfide were selected as test compounds. Aqueous foam decreased the ammonia and hydrogen sulfide emissions by about 33.2 and 66.2%, respectively, after application for 1,800 min. With the application of aqueous foam, amended with 1% of monocalcium phosphate or Yucca extracts, about 81.4 and 51.6%, respectively, of the ammonia emissions were suppressed over the same time period. However, the chemical additives were found to be ineffective in the suppression of hydrogen sulfide. Finally, the aqueous foam, containing microorganisms and the two chemical additives, attained about 88.3 and 70% ammonia and hydrogen sulfide emissions suppression, respectively. The data show that the aqueous foam was effective in the control ammonia and hydrogen sulfide emissions, and the suppression capacity can be markedly enhanced by the addition of appropriate microorganisms and chemical additives.     

盐度、pH和规格对尖紫蛤(Soletellina acuta) 耗氧率和排氨率的影响

采用室内实验生态学方法,进行了尖紫蛤的耗氧率和排氨率的研究.结果表明,盐度和pH对不同规格尖紫蛤的耗氧率和排氨率影响明显.尖紫蛤的耗氧率和排氨率与盐度之间的关系可分别用二次多项式OR=-c1+d2S-d3S2,NR=C2+ d4S-d5S2表示,在盐度10时耗氧率和排氨率达到最大值,当盐度超过10时反而下降;pH 6.4-8.4时,3种规格尖紫蛤的单位体质量耗氧率和排氨率随pH升高而增强,pH大于8.4时耗氧率和排氨率降低.盐度2-18时,不同规格的尖紫蛤个体O∶N值为:8.319-14.840,平均为11.476,在14时O∶N出现峰值;pH 6.4-9.4时,不同大小的尖紫蛤个体O∶N值为:2.377-11.502,平均为8.547,在8.4时O∶N出现峰值.     

Role of atmospheric ammonia in the formation of inorganic secondary particulate matter: A study at Kanpur,India

Levels of fine Particulate Matter (PM_fine), SO₂ and NO_x are interlinked through atmospheric reactions to a large extent. NO_x, NH₃, SO₂, temperature and humidity are the important atmospheric constituents/conditions governing formation of fine particulate sulfates and nitrates. To understand the formation of inorganic secondary particles (nitrates and sulfates) in the atmosphere, a study was undertaken in Kanpur, India. Specifically, the study was designed to measure the atmospheric levels of covering winter and summer seasons and day and night samplings to capture the diurnal variations. Results showed are found to be significantly high in winter season compared to the summer season. In winter, the molar ratio of to was found to be greater than 2:1. This higher molar ratio suggests that in addition to (NH₄)₂SO₄, NH₄NO₃ will be formed because of excess quantity of present. In summer, the molar ratio was less than 2:1 indicating deficit of to produce NH₄NO₃. The nitrogen conversion ratio (NO₂ to NO₃) was found to be nearly 50% in the study area that suggested quick conversion of NO₂ into nitric acid. As an overall conclusion, this study finds that NH₃ plays a vital role in the formation of fine inorganic secondary particles particularly so in winter months and there is a need to identify and assess sources of ammonia emissions in India.