Nitrite photolysis in seawater by sunlight

Nitrite is chemically stable but photochemically unstable in seawater. The net disappearance rate in abiotic low-nitrate seawater exposed to sunlight is ～ 10% per day. The primary products are the free radicals NO and OH. Quantitative aspects of the kinetics and secondary product formation are discussed in terms of a fourteen-step reaction scheme. Possible pathways explaining the results are suggested but not unequivocally identified.The rate of reaction in various marine environments is estimated from cruise data and extrapolations to vary between 0.2–60·10^?3 moles m^?2yr^?1, with a suggested global average for comparison purposes of 1–10·10³ moles m^?2yr^?1.These results confirm and quantify our previous suggestion that nitrite photolysis represents a source of OH radical in seawater. The reaction rate is large enough that significant impacts on the geochemical cycles of dissolved organic carbon and nitrogen and heavy metals may plausibly result. Effects on marine biota and atmospheric trace gas composition are also possible. However, specific reactions coupling the nitrite system to other processes have not yet been identified or demonstrated empirically.     

Determination of nitrate in seawater: Nitrate to nitrite reduction with copper-cadmium alloy

Determination of nitrate in seawater first requires its reduction to nitrite. Construction of a reductor column for use during continuous flow analysis at sea is described. Novel use is made of an alloy of cadmium and copper ($\text{50}\text{50}\text{w}\text{w}$) crushed to between 500 and 350 μm. Its performance is similar to that of the cadmium wire type of reductor but offers advantages of easier preparation and control of reductor volume.     

Todorokite formation in seawater by microbial mediation

Microbial manganese oxidation in seawater was carried out in enrichment cultures which were obtained from the seawater supply system at the Marine Science Museum, Tokai University (Shimizu-shi, Japan). The manganese oxide formed was well-crystallized todorokite. The major element composition was within the range of marine manganese concretions and the O/Mn molar ratio was 1.8. The conditions for formation of manganese oxide minerals in marine environments are discussed on the basis of these results.     

Nitrate assimilation by zooxanthellae maintained in laboratory culture

The ability of cultured zooxanthellae to use ammonium and nitrate was tested. The zooxanthellae were initially isolated from the anemone Aiptasia pulchella. The zooxanthellae were able to grow on media supplemented with either form of dissolved inorganic nitrogen (DIN) although ammonium was inhibitory above 300 μM. In accord with the intact symbiosis and freshly isolated algae, the cultured zooxanthellae took up ammonium. In contrast, the cultured algae demonstrated nitrate uptake and utilization. This was enhanced with DIN deprivation. Nitrate reductase was found in the algae and appeared to be inducible. Within the animal host, excretory ammonium may repress this induction.     

A high sensitivity method for the determination of nanomolar concentrations of Nitrate and Nitrite in seawater with a technicon autoanalyzer II

A high sensitivity manifold for the determination of trace quantities (nanomolar concentrations) of nitrate+nitrite and nitrite alone is described. The method uses a classical Technicon AutoAnalyzer II usually employed for shipboard analysis. A reproducibility of ± 1 nmol dm⁻³ for nitrate plus nitrite and nitrite alone was obtained, with an analytical rate of 40 samples h⁻¹.     

Analysis of Ac in seawater by delayed coincidence counting

The activity of ²²⁷Ac in seawater was determined using a delayed coincidence counting technique based on the measurement of the short-lived daughter ²²³Ra (half-life of 11 days). Two 180-l aliquots of Ac free seawater from surface waters of the California borderlands were spiked with Harwell Uraninite standard and the added Ac and Ra were extracted on Mn-fibers. The measured activities on the fibers agreed to within 5% of the equilibrium Ac activity of the spike addition, well within the 2σ counting error of 7% for the measurements. Thus, any recovery error was indistinguishable from counting error. Large volume samples were collected from the water column of the Eastern North Pacific in December of 1998 and processed through Mn-fiber columns. The ²²³Ra activities on the fibers were measured four or more times over a period of 2 months by the technique of [J. Geophys. Res. 101 (1996) 1321] to determine if the activity of ²²³Ra was wholly supported by ²²⁷Ac. In most cases, no significant differences in ²²³Ra activity were observed during repeated counting of the same sample, again implying that ²²³Ra was supported wholly by ²²⁷Ac. In samples where unsupported ²²³Ra were present, samples were counted beyond five half live of the ²²³Ra (>60 days). Two depth profiles of ²²⁷Ac in the Eastern North Pacific showed similar shape and activity to profiles in the Western and Central Pacific measured with alpha-spectrometry by [Nature 310 (1984) 486). Surface waters of the Southern Ocean were relatively enriched in ²²⁷Ac compared to Eastern North Pacific waters, possibly indicating export of the parent ²³¹Pa from Atlantic surface waters or upwelling.     

Degradation ofn-paraffin mixture by marine microorganisms in enriched seawater medium

The ability to degraden-paraffin mixture of two bacterial strains,Caulobacter sp. andFlavobacterium sp., isolated from sea water of Tokyo Bay was studied experimentally in the enriched seawater (ESW) medium. These bacteria degraded actively the mixture ofn-tridecane,n-tetradecane,n-pentadecane andn-hexadecane. The maximum rate of degradation was observed after a lag period of 2 to 8 day and these bacteria were found to degrade then-paraffin mixture at rates calculated to be in a range from 3.3×10^?12 to 3.4×10^?11 mg-oil cell^?1 h^?1 at 20°C. The maximum degradation rate,r _m mg-oil l^?1 h^?1, was correlated with the amount of the initial totaln-paraffin,S mg-oil l^?1, as expressed by the following equation: $$rm = (rm)\max \left( {\frac{S}{{S + Km}}} \right)$$ where (r _m )_max denotes the largest value ofr _m whenn-paraffin exists in large excess andK _m is a constant and represents the amount ofn-paraffin at which the degradation rate,r _m , reaches 1/2 of its largest value, (r _m )_max. The values of (r _m )_max andK _m were calculated to be as follows: In the case ofCaulobacter sp. (strain KM-1), (r _m )_max=6.0 mg-oil l^?1 h^?1 andK _m =191 mg-oillesw ^?1; in the case ofFlavobacterium sp., (r _m )_max=5.47 mg-oil l^?1 h^?1 andK _m =152 mg-oillesw ^?1.     

海南地热能海水淡化可行性探讨

为了解海南地区利用地热能进行海水淡化的可行性,阐述了海南缺水情况以及地热资源分布,并对使用地热能进行海水淡化作了技术和经济探讨,结果表明海南缺水地区可以从当地可用的地热资源中获益。同时,指出基于地热能的海水淡化仍面临一些问题,需要提高重视程度和科研投入,并试行推广积极的产业扶持政策,从而促进海南地热能海水淡化的研究和利用。     

Thallium concentrations in seawater

Measurements of the concentration of thallium in seawater collected from numerous ocean locations ranged from 12 to 16 ng kg⁻¹. Variations between the Atlantic and Pacific Oceans, between the northern and southern hemispheres of the Pacific Ocean, and between surface and deep waters of both the Pacific and Atlantic oceans were comparable with the precision of the analyses. This relatively constant distribution indicates that the element's cycle in seawater may be similar to those of the alkali metals which are its principal biogeochemical analogues.     

Silica-alumina interactions in seawater

Amorphous silica can polymerize in distilled water, in 0.6 N NaCl solution and in seawater to form a colloidal suspension that contains approximately 200 ppm Si. Solid amorphous alumina can prevent this polymerization in seawater and in 0.6 N NaCl, and can inhibit but not prevent it in distilled water. This prevention of polymerization may be an important factor in authigenic mineral formation.The presence of solid amorphous alumina with solid silica in the same solutions causes the final concentrations of dissolved silica to be lower than those attained by solid silica in the absence of solid alumina. The effects are similar whether the final levels are approached from above or below the saturation concentration for amorphous silica. This indicates that the observed concentration of dissolved silica will be a function of available alumina as well as of the silica solubility.The presence of solid amorphous alumina with quartz in seawater, 0.6 N NaCl solution and distilled water causes dissolved silica levels to remain below 0.7 ppm Si for at least 38 days. The same systems in the absence of alumina approach the solubility levels of quartz within that time period.     

Thorium speciation in seawater

Since the 1960s, thorium isotopes occupy a special place in the oceanographer's toolbox as tracers for determining rates and mechanisms of oceanic scavenging, particle dynamics, and carbon fluxes. Due to their unique and constant production rates from soluble parent nuclides of uranium and radium, their disequilibrium can be used to calculate rates and time scales of sinking particles. In addition, by ratio-ing particulate ²³⁴Th (as well, in principle, other Th-nuclides) to carbon (and other elements), and linking this ratio to the parent–daughter disequilibrium in the water column, it is possible to calculate fluxes of carbon and other elements. Most of these applications are possible with little knowledge of the dissolved chemical properties of thorium, other than its oxidation state (IV) and tendency to strongly sorb to surfaces, i.e., its “particle- or surface-activity”. However, the use of any tracer is hindered by a lack of knowledge of its chemical properties. Recent observations in the variability of carbon to ²³⁴Th ratios in different particle types, as well as of associations of Th(IV) with various marine organic biomolecules has led to the need for a review of current knowledge and what future endeavors should be taken to understand the marine chemistry of thorium.     

The determination of sulfide in seawater by flow-analysis with voltammetric detection

Preliminary measurements of sulfide in seawater using cathodic stripping voltammetry and a hanging mercury drop electrode (HMDE) in batch-mode showed that the sulfide peak decreased rapidly with time. This decrease was not caused by O₂, H₂O₂ or IO₃⁻, and the sulfide peak was not stabilised by trace metal additions. A home-made flow-cell was constructed to enable the determination of sulfide in seawater using voltammetry with an HMDE. A stable sulfide peak was obtained by flow-analysis with voltammetric detection, with a precision of 2.8% and detection limit of 0.5 nM at a 60 s adsorption time. Several thiol compounds were found to produce a peak at, or very close to, the peak potential for sulfide. Their interference was evaluated by allowing the sulfide peak in conventional (batch) voltammetry to decay. Comparative experiments showed that waste metallic mercury is responsible for removal of sulfide in batch-mode analysis due to formation of insoluble mercuric sulfide salts causing the rapid decay of the sulfide peak. The problem is circumvented by using flow-analysis to determine sulfide.     

离子色谱法测定海水中氯离子和硫酸根离子

氯离子和硫酸根离子是海水中重要的无机阴离子,在研究海洋生态变化、海洋循环作用过程与海洋全球气候变化等领域具有重要的指示意义。其测定方法较多,但缺少相应的测试方法。本文对测定海水中Cl^–,SO₄^2–的离子色谱方法进行了优化,选用IonPacAS14碳酸盐选择性离子色谱柱,以3.5mmol/L Na₂CO₃+1 mmol/L NaHCO₃为流动相,可消除海水样品中碳酸盐及其他阴离子的干扰。该方法对Cl^–检出限为0.29mg/L,线性相关系数r²=0.999 2,对SO₄^2–检出限为0.42mg/L,线性相关系数r²=0.997 9。样品的加标回收率在95%～102%,Cl^–和SO₄^2–的相对标准偏差分别为1.92%和4.18%。该方法简便、迅速、灵敏、准确度高,可满足批量海水样品中Cl<...     

海水中腐殖质对溶解态铁的络合及其影响因素

腐殖质(humic substances,简称HS)是地表普遍存在的天然有机物,对海洋中重要的微量营养元素-铁(Fe)的分布及生物地球化学循环具有重要的影响作用。本文对腐殖质的来源、分布及对海水中溶解态铁的迁移转化的影响做了总结,特别论述了其在河口及沿岸水域的行为。大量研究表明河口、沿岸及开放海水中溶解态铁分布的变化可以用腐殖质的浓度及其铁结合能力的变化来解释。腐殖质的络合作用不仅能够阻止溶解态铁(DFe)在河口、沿岸等水域被去除,而且能够通过洋流将DFe迁移至外海及大洋区域,此外还能增加铁的溶解度及对海水中浮游植物的生物可利用性,并且促进铁的氧化还原循环。研究还发现两者之间的络合强度受到盐度、pH等理化因素的影响。盐度是影响HS与DFe配合能力的重要影响因素,盐度增加,导致HS中可以与Fe配合的位点数量降低,配合总量呈现指数降低,而pH的增加可以增加HS与DFe的配合量。另外HS还能影响海水中DFe的氧化还原,并以此影响浮游植物对DFe的吸收利用。因此腐殖质对溶解态铁的有机络合作用是影响其海洋生物地球化学循环的一个重要参数,对进一步研究海水中腐殖质的浓度和分布具有重要的意义。     

Release and uptake of dissolved silica in seawater by marine sediments

Natural marine sediments can release dissolved silica to silica-poor seawater and can remove silica from seawater enriched with dissolved silica. These are fast reactions, with sufficient reaction occurring within the first 48 hours to indicate clearly the direction of the reaction. The relative importance of these two processes varies with the ratio of clays to biogenic silica in the sediment. Both the release and the uptake reactions approach the interstitial water concentration of dissolved silica as an end point, which suggests that these reactions may influence this concentration. No change in sediment reactivity with respect to silica uptake or release reactions was observed with increasing depth in core for the three sediment cores investigated; this indicates that uptake sites are not saturated, and silica is available for dissolution for a long time after deposition.     

ICP-OES标准加入法准确测定海水中的硼

硼作为海水中的重要组分,其准确测定对海洋环境生物地球化学过程研究具有重要意义。海水中硼的常用测定方法具有前处理步骤繁琐、耗时长、样品易被污染、灵敏度低等缺点,不适于大批量海水样品的准确测定。为剔除海水高盐基体效应及干扰,本文运用电感耦合等离子体发射光谱法(ICP-OES),将海水样品进行稀释,采用标准加入法建立工作曲线,对海水中硼含量进行准确测定。正交实验显示,ICP-OES最佳工作条件为射频功率1400 W,雾化气流量0.7 L/min,观测高度14 mm,进样泵速1.5 m L/min。标准加入法标准曲线相关系数大于0.999,相对标准偏差为0.76%~1.27%,加标回收率为94.6%~101.8%,方法检出限为1.073μg/L。实际的海水样品分析表明,该方法可消除海水基体干扰,减少测定误差,并且前处理操作简单快速,化学试剂用量少,回收率高,精密度好,灵敏度高,可用于海水及其它高盐样品中硼含量的准确测定。     

海水化学需氧量烘箱加热测定方法的研究

在海水化学需氧量(COD)测定中, 利用烘箱代替海洋监测规范中的电炉对样品进行加热; 探讨了烘箱加热测定法所需的加热条件及其测定范围, 并通过实际水样测定了解此法的精确度和准确度。结果表明, 烘箱加热测定法具有与海洋监测规范方法同等水平的精确度和准确度, 并且在大批量样品测定中具有省时、省电、省力的优点, 具有较好的应用价值。