Chemical and Isotopic Composition of Waters and Dissolved Gases in Some Thermal Springs of Sicily and Adjacent Volcanic Islands, Italy

Hydrochemical (major and some minor constituents), stable isotope ( and , δ13C_TDIC total dissolved inorganic carbon) and dissolved gas composition have been determined on 33 thermal discharges located throughout Sicily (Italy) and its adjacent islands. On the basis of major ion contents, four main water types have been distinguished: (1) a Na-Cl type; (2) a Ca-Mg > Na-SO₄-Cl type; (3) a Ca-Mg-HCO₃ type and (4) a Na-HCO₃ type water. Most waters are meteoric in origin or resulting from mixing between meteoric water and heavy-isotope end members. In some samples, δ¹⁸O values reflect the effects of equilibrium processes between thermal waters and rocks (positive ¹⁸O-shift) or thermal waters and CO₂ (negative ¹⁸O-shift). Dissolved gas composition indicates the occurrence of gas/water interaction processes in thermal aquifers. N₂/O₂ ratios higher than air-saturated water (ASW), suggest the presence of geochemical processes responsible for dissolved oxygen consumption. High CO₂ contents (more than 3000 cc/litre STP) dissolved in the thermal waters indicate the presence of an external source of carbon dioxide-rich gas. TDIC content and δ¹³C_TDIC show very large ranges from 4.6 to 145.3 mmol/Kg and from –10.0‰ and 2.8‰, respectively. Calculated values indicate the significant contribution from a deep source of carbon dioxide inorganic in origin. Interaction with Mediterranean magmatic CO₂ characterized by heavier carbon isotope ratios ( value from -3 to 0‰ vs V-PDB (CAPASSO et al., 1997, GIAMMANCO et al., 1998; INGUAGGIATO et al., 2000) with respect to MORB value and/or input of CO₂-derived from thermal decomposition of marine carbonates have been inferred.     

Opportunistic macroalgae metrics for transitional waters. Testing tools to assess ecological quality status in Portugal

Macroalgae communities constitute one of the ecological quality elements for the evaluation of the ecological quality status (EQS) of coastal and transitional waters, required to implement the WFD. While these algae are natural components of estuarine systems and play important roles in several estuarine processes, macroalgal blooms are of ecological concern because they can reduce the habitat quality. Several works are being carried out to set standard methods for monitoring macroalgae blooms, in order to develop tools to derive EQS based upon this biological quality element. The aim of this paper is to apply the methodology described by Scanlan et al. [Scanlan, C.M., Foden, J., Wells, E., Best, M.A., 2007. The monitoring of opportunistic macroalgal blooms for the water framework directive. Marine Pollution Bulletin 55, 162–171] to a series of data assembled in the south arm of the Mondego estuary (Atlantic coast of Portugal) considering two different ecological situations. Additionally, an alternative assessment method intended to be used when no biomass data are available was also tested. In general, both options captured the inter-annual variations in accordance with the system evolution. Option 2, less expensive and time-consuming, allowed an EQS evaluation with accurate results when biomass data were not available. The results suggest that sampling should be carried out from April to June.     

The effect of asymmetric dune roughness on tidal asymmetry in the Weser estuary

The bed of estuaries is often characterized by ripples and dunes of varying size. Whereas smaller bedforms adapt their morphological shape to the oscillating tidal currents, large compound dunes (here: asymmetric tidal dunes) remain stable for periods longer than a tidal cycle. Bedforms constitute a form roughness, that is, hydraulic flow resistance, which has a large-scale effect on tidal asymmetry and, hence, on hydrodynamics, sediment transport, and morphodynamics of estuaries and coastal seas. Flow separation behind the dune crest and recirculation on the steep downstream side result in turbulence and energy loss. Since the energy dissipation can be related to the dune lee slope angle, asymmetric dune shapes induce variable flow resistance during ebb and flood phases. Here, a noncalibrated numerical model has been applied to analyze the large-scale effect of symmetric and asymmetric dune shapes on estuarine tidal asymmetry evaluated by residual bed load sediment transport at the Weser estuary, Germany. Scenario simulations were performed with parameterized bed roughness of symmetric and asymmetric dune shapes and without dune roughness. The spatiotemporal interaction of distinct dune shapes with the main drivers of estuarine sediment and morphodynamics, that is, river discharge and tidal energy, is shown to be complex but substantial. The contrasting effects of flood- and ebb-oriented asymmetric dunes on residual bed load transport rates and directions are estimated to be of a similar importance as the controls of seasonal changes of discharge on these net sediment fluxes at the Lower Weser estuary. This corroborates the need to consider dune-induced directional bed roughness in numerical models of estuarine and tidal environments.     

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Edelvang, Karen; Larsen, Michael; Pejrup, Morten: Tidal Variation in Field Settling Velocities of Suspended Sediment in a Tidal Channel. Geografisk Tidsskrift 92:116–121. Copenhagen 1992.

Particles of silt and clay may form large, low density floes when suspended in salt water. The sediment floes have settling velocities much higher than the single small particles constituting them and therefore, the flocculation process may strongly influence the transport of cohesive sediment in estuarine environments. will be described in this paper, the field settling velocities of suspended sediment were investigated in a large tidal channel with tidal current velocities up to 1.3 m/s and depths of about 10 m. The analyses of suspended sediment were made on both bottom and surface samples. For the bottom samples, equivalent median fall diameters in the range 26–98 μm were measured. For surface samples, the range was 15–40 μm. During most of the tidal period, the occurrence of much larger settling diameters near the bottom was due to the suspension of individual sand and silt particles. For the investigated periods, high-tide was the only possible time to observe flocculation influencing the vertical distribution of finegrained sediment in the water column.     

九龙江河口湾高浓度悬沙水体的分布与扩散特征

通过对九龙江河口湾洪水期和枯水期含沙量等值线的分析,描述了河口湾内悬浮泥沙的时空分布特征及其在涨潮和落潮期间的变化情况,并对洪水期大潮湾内水质点的滞流点位置作了计算.结果表明,水流运动和水体含沙量沿入海方向均呈现有规律的变化,河口湾内存在两个主要水流滞流区,一处位于海门岛北部,一处位于鸡屿东侧.悬浮泥沙的分布和水流运动间呈现明显的相关性.     

厦门海域秋、冬季溶解有机氮时空分布及总溶解态氮的组成

根据2015年10月(秋季)和2016年1月(冬季)对厦门海域开展的2次水质调查,研究了该海域中溶解有机氮(DON)的时空分布特征及总溶解态氮(TDN)的组成,并探讨了DON与环境要素的相关性及其来源.结果表明:厦门海域DON浓度平均值冬季大于秋季,表层高于底层,整体呈内湾、河口区较高,湾口区低的分布格局.秋季DON浓度的空间分布为同安湾西海域九龙江口邻近海域东南海域大嶝海域,冬季为西海域同安湾九龙江口邻近海域东南海域大嶝海域.该海域秋、冬季DON浓度占比(CDON/CTDN)分别为56%和53%,DON浓度占比整体呈湾口区大、河口区及内湾小的分布特征.相关性分析表明,该海域秋、冬季表、底层DON浓度与盐度均呈极显著负相关,与磷酸盐、硅酸盐含量为极显著正相关,与叶绿素a、溶解氧、p H值存在一定相关性.厦门海域DON的来源主要有九龙江河流、城市生活污水、工农业废水等陆源输入和浮游植物活动等海源生成.     

河口盆地非线性地震效应及设计地震动参数

针对基岩明显起伏、土层非均匀分布的典型河口盆地场地,考虑土体非线性特征,采用黏弹性人工边界模拟无限域对地震波动的影响,建立大尺度精细化二维有限元模型,分析了盆地地表地震动幅值、频谱、持时、传递函数特征,探讨了基岩起伏土层的地震动聚集效应及盆地边缘效应。结果表明：（1）盆地近地表土层表现出不同程度的地震动放大效应,且随土层深度增加呈非单调递减特征,基岩突变处地震动聚集效应明显,盆地两侧产生较为显著的边缘效应;场地中、长周期地震动的放大作用显著;（2）多遇地震、偶遇地震和罕遇地震水平时,场地卓越周期依次介于0.35～0.65 s、0.40～0.75 s和0.50～1.05 s之间;给出了盆地地表PGA（地表峰值加速度）、卓越周期均值等值线图及地表加速度反应谱放大因子建议值,地表设计地震动参数amax（地震影响系数）与Tg（特征周期）明显大于现行《建筑抗震设计规范》取值;（3）盆地特殊位置地表地震动持时得到不同幅度增长,且与输入地震动特性相关;（4）该盆地对0.5～2.0 Hz频段基岩地震动的放大效应比较显著,对小于0.2 Hz或大于2.5 Hz的基岩地震动,该盆地地震动放大效应不明显;（5）福州城区及其邻近区域地震动放大效应普遍较大。大尺度二维非线性分析一定程度上能合理反映微地形起伏、土层分布及土体非线性对地震波传播过程的影响。     

Chemical weathering in the drainage basin of a tropical watershed (Nsimi-Zoetele site, Cameroon) : comparison between organic-poor and organic-rich waters

This study deals with the weathering processes operating at the scale of a small catchment (Nsimi-Zoetele, Cameroon) and is focused on the role of organic colloids on mineral weathering and transport of elements in natural waters. Samples of river, spring and groundwaters from Nsimi-Zoetele were filtered through membranes of decreasing pore size (0.22 μm, 0.025 μm, or: 300,000 Da, 5000 Da) to separate colloidal fractions from the truly dissolved one. Major and trace elements and dissolved organic carbon (DOC) were analysed in each fraction. Two kinds of waters can be distinguished in the catchment: clear and coloured waters. Clear waters exhibit low concentrations of major and trace elements and DOC. Elements are carried in these solutions in a true dissolved form except Al and rare earth elements (REEs). By contrast, the higher abundances of Al, Fe and trace elements in coloured waters are controlled by the colloidal fraction. Thermodynamic equilibrium calculations show that clear waters are in equilibrium with kaolinite and iron oxi-hydroxide which are major minerals in the weathered soil. For coloured waters, the aqueous speciation of Ca, Mg, Cu, Fe, Al, La and Th was calculated taking into account the complexes with humic acids. Speciation calculations for Cu, Fe, Al, La, Th show a strong complexation with humic acids, in good agreement with the results of the filtration experiments. By contrast, although filtration experiments show a strong control of major cations by organic matter (for example 75% for Ca), speciation calculations reveal that their complexes with humic ligands do not exceed a few percent of total dissolved elements. This discrepancy is explained as an artefact induced by the organic colloids and occurring during the filtration procedure. Finally, both filtration experiments and speciation calculations show that organic matter plays an important role in natural DOC-rich waters. Organic acids increase significantly the dissolution rates of silicates and oxi-hydroxides and thus the amounts of solutes and of complexed elements leaving the catchment.     

Iron speciation and biogeochemistry in different nearshore waters

Different environmental conditions in various nearshore waters dynamically determine the speciation of iron, its solubility, removal and hence bioavailability to phytoplankton. The iron speciation, the impact of phytoplankton blooms and the effects of organic matter on iron speciation and transformation were studied in four different coastal systems: the Trondheim Fjord, Norway, which is a coastal system that is open to a vast riverine impact; Hopevågen, Norway, a pristine coastal basin, which has negligible river and anthropogenic impact; zmir Bay, Turkey, a Mediterranean embayment with heavily polluted eutrophic inner–middle section, and the oligotrophic outer section. In this paper, we compare iron speciation in these different coastal systems. While colloidal iron (ColFe) was the predominant species especially in the Trondheim Fjord and to some degree also in Hopavågen, Chelex labile iron (ClxLFe) and hydrophobic organic-iron complex (HpOFe) were predominate species in both the inner–middle and the outer section of zmir Bay. The impact of phytoplankton blooms on the ClxLFe was significant especially in the Trondheim Fjord, in the inner–middle section of zmir Bay and in Hopevågen.     

许氏平鲉Sebastes schlegeli(Hilgendorf)及欧氏六线鱼Hexagrammos otakii Jordan et Starks核型研究

采用PHA体内注射肾细胞直接制片法研究青岛近海常见的许氏平鲉和欧氏六线鱼的核型,核型公式分别为2n=48,2m+46t,NF=50和2n=48,6m+16sm+20st+6t,NF=70。许氏平鲉的t组的第20对(t20)染色体和欧氏六线鱼t组第3对(t3)染色体分别为各自核型中具随体的特征性染色体。此外,在两种鱼中均未发现有异形性杂色体存在。