How conservative is arsenic in coastal marine environments? A study in Irish coastal waters     

Pinelopi Anninou  Rachel R. Cave 《Estuarine, Coastal and Shelf Science》2009

The conservative potential of arsenic in the relatively pristine waters of Galway Bay, an estuarine system in the west of Ireland, is examined through the inter-seasonal variations in the distribution of its total, hydride and non-hydride fractions. The arsenic concentrations in Galway Bay and local fresh water sources at all seasons were lower than what is considered the natural seawater concentration of 2 μg L⁻¹ (27 nM). The effects of physical mixing, biological uptake and regeneration of arsenic on its distribution are considered. The degree of biological uptake and regeneration of the element are determined by a first order speciation between total arsenic (a small part of which should be of organic origin) and hydride arsenic (mostly of inorganic origin). The structural similarity of arsenic species to phosphate in seawater causes arsenic to be taken up by biota, which then have to detoxify it, so results are presented against phosphate to determine the degree of biological transformation of arsenic at different seasons. An in-house, batch type system of hydride generation coupled to electro-thermal atomic absorption spectrometry is used for the analysis of arsenic; this is preceded by UV-digestion prior to the measurement of total arsenic. Results show only a small association of arsenic with phosphate but a near linear, positive distribution pattern between arsenic and salinity in Galway Bay (R² ∼ 0.6), which is reproducible among seasons, indicating that in this environment the biological uptake of arsenic is likely to be a much slower process than the physical mixing of the water masses.  相似文献   

Diatom succession and silicon removal from freshwater in estuarine mixing zones: From experiment to modelling   总被引：1，自引：0，他引：1  

Vincent Roubeix  Véronique RousseauChristiane Lancelot 《Estuarine, Coastal and Shelf Science》2008

Estuaries act as filters for land derived material reducing the river input to the coastal zone. Silicon (Si) removal from freshwater which is tightly linked to the growth of diatoms was studied in the estuarine mixing zone where the mixing of freshwater and seawater results in a salinity gradient. Three planktonic diatom species with different origin and salinity tolerance were grown in an artificial salinity gradient. Salinity stress and nutrient depletion led to a specific succession of the three diatoms along the salinity gradient. When available light was increased, diatoms reached higher biomass and the Si removal from water column was more efficient along the mixing. From this experiment, a conceptual model of Si transformations and removal from freshwater was build and applied to an idealized stratified estuary. Sensitivity analysis with varying initial conditions and parameter values pointed transit time of freshwater in the estuary, freshwater and seawater mixing rate and river turbidity as important interactive factors influencing Si removal from freshwater. Other factors like the total amount and the salinity tolerance of diatoms in the upstream river were shown to significantly affect riverine Si removal from the surface layer of an estuary. Finally it appears that Si removal from freshwater in estuarine mixing zones proceeds in two ways: a first rapid death and sedimentation of planktonic stenohaline diatoms imported from the river and second, the growth and subsequent settling of planktonic euryhaline diatoms of either freshwater or marine origin.  相似文献   

The effect of salinity on clearance rate in the suspension-feeding estuarine gastropod Crepipatella dilatata under natural and controlled conditions   总被引：2，自引：1，他引：1  

O.R. Chaparro  Y.A. Montiel  C.J. Segura  V.M. Cubillos  R.J. Thompson  J.M. Navarro 《Estuarine, Coastal and Shelf Science》2008,76(4):861-868

The suspension-feeding gastropod Crepipatella dilatata occurs in estuaries in southern Chile that experience considerable fluctuations in salinity, driven by tidal and atmospheric forces. In the Quempillén estuary salinities as low as 9 psu may occur after severe rainstorms, and persist for several hours. In this study salinity was the major factor influencing the clearance rate of C. dilatata. At salinities below 20 psu, filtration ceased, whereas at high salinities (>22 psu) mean clearance rate was 0.24 l h⁻¹ standard animal⁻¹ (S.D. 0.18) for actively filtering individuals. This was confirmed by laboratory experiments under controlled conditions. Endoscopic observations were consistent with measurements of clearance rate, and showed that at salinity 25–30 psu the rate of transport along the gill filaments of particulate material embedded in mucus was 759 μm s⁻¹ (S.D. 480), but particle transport ceased at and below salinity 20 psu. Complete or partial isolation of the mantle cavity from the environment may be a mechanism to protect soft tissues and/or incubated egg capsules from osmotic stress.  相似文献   

珠江口内伶仃洋河口湾盐度输运机理     

朱雅敏  陈子燊 《海洋通报》2008,27(1):29-34

为了评价物质入海通量对地区的影响,有必要对入海通量进行统计分析,并对其控制因子进行研究.由于机制分解方法物理概念清晰,采用此方法.从物质平衡入手,分析物质输运机理,描述不同类型河口的特点,并在实测资料的基础上,研究珠江口内伶仃洋河口湾的盐度输运,对比各动力因子对盐度贡献项的大小,结果表明盐度纵向净通量主要是由纵向净平流输运控制,斯托克斯漂移和垂向净环流引起的盐度输运也不容忽视.  相似文献   

黄河三角洲退化湿地微生物特性的研究   总被引：3，自引：0，他引：3  

王震宇  辛远征  李锋民  高冬梅 《中国海洋大学学报(自然科学版)》2009,39(5)

本研究通过DAPI染色法、FDA染色法和稀释平板法对黄河三角洲退化湿地微生物特性进行研究,在分析土壤盐度和植物根际效应对微生物特性影响的基础上,探讨了微生物群落的垂直分布特征,并对可培养耐盐微生物进行了初步分离。结果表明,土壤盐度与微生物数量、活性及多样性呈显著负相关性(P<0.01)。耐盐细菌在耐盐微生物中占绝对优势,放线菌次之,真菌最少;微生物群落具有明显的垂直分布特征,数量、活性和多样性均随土层深度的增加而下降。五种植物(碱蓬、柽柳、芦苇、白茅、茵陈蒿)根际微生物群落的数量、活性及多样性明显高于非根际微生物群落;与柽柳、芦苇、白茅、茵陈蒿相比,碱蓬的根际效应最强。这些结果可为进一步开发利用滨海湿地微生物资源,形成修复退化湿地盐碱化土壤的植物-微生物耦合系统提供必要的理论依据。  相似文献   

A study on retrieval algorithms in oceanic passive microwave remote sensing using 1.4 GHz and 10.7 GHz bands     

殷晓斌 《热带海洋学报》2009,28(5):18-28

To retrieve sea-surface salinity (SSS) from radiometer data at 1.4 GHz, auxiliary data of sea-surface temperature (SST), surface roughness and meteorological variables are needed. The authors study oceanic passive polarimetric microwave remote sensing using 1.4 GHz and 10.7 GHz bands. A set of algorithms are developed for 1.4 GHz and 10.7 GHz microwave polarimetric radiometer at 50° incidence angle to retrieve wind vector, as well as other geophysical parameters, such as SSS, SST, atmospheric volumes of water vapor and liquid water. Idealized retrievals are conducted using 2324 simulated brightness temperatures of full Stokes parameters at 1.4 GHz and 10.7 GHz. Results indicate that SSS, SST, sea-surface wind speed, direction, atmospheric volumes of water vapor and liquid water can be inversed at the same time. This suggests an alternative way for SSS remote sensing.  相似文献   

Groundwater mineralisation processes in Mediterranean semi‐arid systems (Cap‐Bon,North east of Tunisia): hydrogeological and geochemical approaches     

Adel Zghibi  Lahcen Zouhri  Jamila Tarhouni  Lamia Kouzana 《水文研究》2013,27(22):3227-3239

The groundwater of the Korba plain represents major water resources in Tunisia. The Plio‐Quaternary unconfined aquifer of the Cap‐Bon (north‐east Tunisia) is subject to the intensive agricultural activities and high groundwater pumping rates due to the increasing of the groundwater extraction. The degradation of the groundwater quality is characterized by the salinization phenomena. Groundwater were sampled and analysed for physic‐chemical parameters: Ca²⁺, Mg²⁺, Na⁺, K⁺, Cl^‐, SO₄^2‐, HCO₃^‐, NO₃^‐, pH, electrical conductivity (EC), and the temperature (T°). The hydrochemical analysis is coupled with the calculation of the saturation indexes (SI gypsum, SI halite, SI calcite and SI dolomite), ionic derivation and with the ion correlations compared to chloride concentrations: Na⁺/ Cl^‐, Ca²⁺/ Cl^‐ and Mg²⁺/ Cl^‐ ratios. Seawater fractions in the groundwater were calculated using the chloride concentration. Those processes can be used as indicators of seawater intrusion progression. EC methods were also conducted to obtain new informations on the spatial scales and dynamics of the fresh water–seawater interface of coastal groundwater exchange. The mixing zone between freshwater and saltwater was clearly observed from the EC profile in the investigated area where a strong increase in EC with depth was observed, corresponding to the freshwater and saltwater interface. Results of hydrochemical study revealed the presence of direct cation exchange linked to seawater intrusion and dissolution processes associated with cations exchange. These results, together with EC investigation, indicated that the groundwater is affected by seawater intrusion and is still major actor as a source of salinization of the groundwater in Korba coastal plain. Further isotopic and hydrological investigations will be necessary to identify and more understood the underlying mechanisms. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Discussion about the validity of sharp‐interface models to deal with seawater intrusion in coastal aquifers          下载免费PDF全文

Carlos Llopis‐Albert  David Pulido‐Velazquez 《水文研究》2014,28(10):3642-3654

Analytical models have been exhaustively used to study simple seawater intrusion problems and the sustainable management of groundwater resources in coastal aquifers because of its simplicity, easy implementation, and low computational cost. Most of these models are based on the sharp‐interface approximation and the Ghyben–Herzberg relation, and their governing equations are expressed in terms of a single potential theory to calculate critical pumping rates in a coastal pumping scenario. The Ghyben–Herzberg approach neglects mixing of fresh water and seawater and implicitly assumes that salt water remains static. Therefore, the results of the analytical solutions may be inaccurate and unacceptable for some real‐complex case studies. This paper provides insight into the validity of sharp‐interface models to deal with seawater intrusion in coastal aquifers, i.e. when they can be applied to obtain accurate enough results. For that purpose, this work compares sharp‐interface solutions, based on the Ghyben–Herzberg approach, with numerical three‐dimensional variable‐density flow simulations for a set of heterogeneous groundwater flow and mass transport parameters, and different scenarios of spatially distributed recharge values and spatial wells placement. The numerical experiment has been carried out in a 3D unconfined synthetic aquifer using the finite difference numerical code SEAWAT for solving the coupled partial differential equations of flow and density‐dependent transport. This paper finds under which situations the sharp‐interface solution gives good predictions in terms of seawater penetration, transition zone width and critical pumping rates. Additionally, the simulation runs indicate to which parameters and scenarios the results are more sensitive. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

马氏珠母贝水通道蛋白基因AQP4 cDNA克隆和表达分析     

潘肖兰  刘惠茹  许濛  许瀚之  张华  何毛贤 《热带海洋学报》2020,39(3):66-75

水通道蛋白4(aquaporin4, AQP4)是一类被动运输水的通道蛋白。本研究根据转录组测序获得的马氏珠母贝AQP4片段, 采用RACE技术获得了AQP4的全长cDNA, 命名为PfAQP4, 其5′非翻译区(untranslated region, UTR)为114bp, 3′UTR为839bp, 开放阅读框(open reading frame, ORF)为858bp, 编码285个氨基酸。PfAQP4含有6个α螺旋跨膜区、5个环、1个主要内嵌蛋白(major intrinsic protein, MIP)结构域、2个NPA(Asn-Pro-Ala)基序, 属于AQP1-like型。利用qPCR技术分析PfAQP4在不同组织、不同发育时期以及盐度胁迫条件下的mRNA表达模式。结果显示: (1) PfAQP4在所有被检测组织中均表达, 其中在闭壳肌、足和鳃中表达量较高; (2) PfAQP4在不同的发育时期均有表达, 其表达量整体呈现先升高后降低的趋势, 其中在2—4细胞期表达量最高, 在眼点幼虫期表达量最低; (3) 在高盐度组(36‰)盐度胁迫24、72、120h后, PfAQP4表达量显著上升, 在168h降至对照组水平; 在低盐(16‰)组, PfAQP4表达量在24h显著上调, 在72h恢复至对照组水平, 说明盐度影响鳃组织中PfAQP4的表达量, 也表明PfAQP4在马氏珠母贝渗透压调节中起着非常重要的作用。  相似文献   

乐清湾海域真刺唇角水蚤在盐度梯度下的生态阈值研究          下载免费PDF全文

李轶  杨旖祎  叶属峰 《应用海洋学学报》2019,38(3):393-398

基于2016年5月乐清湾海域的海洋调查资料,分析了浮游动物真刺唇角水蚤(Labidocera euchaeta)的优势度及其与海水盐度(S)的相关性,并利用高斯模型研究了在盐度梯度下真刺唇角水蚤丰度的生态阈值(Ecological Threshold,ET)。结果表明:真刺唇角水蚤是乐清湾海域春季浮游动物优势种之一,优势度为0. 061;其丰度与盐度呈极显著负相关关系(p 0. 01),盐度是影响真刺唇角水蚤水平分布的主要因素之一;其最适盐度值为21. 36,最适盐度生态阈值区间为[20. 17,22. 55],真刺唇角水蚤在盐度梯度下的生态阈值区间为[18. 99,23. 73]。此外,还探讨了盐度对真刺唇角水蚤生长的影响,以及此生态阈值研究在乐清湾海域资源环境承载能力监测预警中的作用。  相似文献