7 resultados para metal speciation

em Aquatic Commons


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The Alliance for Coastal Technologies (ACT) Workshop on Trace Metal Sensors for Coastal Monitoring was convened April 11-13, 2005 at the Embassy Suites in Seaside, California with partnership from Moss Landing Marine Laboratories (MLML) and the Monterey Bay Aquarium Research Institute (MBARI). Trace metals play many important roles in marine ecosystems. Due to their extreme toxicity, the effects of copper, cadmium and certain organo-metallinc compounds (such as tributyltin and methylmercury) have received much attention. Lately, the sublethal effects of metals on phytoplankton biochemistry, and in some cases the expression of neurotoxins (Domoic acid), have been shown to be important environmental forcing functions determining the composition and gene expression in some groups. More recently the role of iron in controlling phytoplankton growth has led to an understanding of trace metal limitation in coastal systems. Although metals play an important role at many different levels, few technologies exist to provide rapid assessment of metal concentrations or metal speciation in the coastal zone where metal-induced toxicity or potential stimulation of harmful algal blooms, can have major economic impacts. This workshop focused on the state of on-site and in situ trace element detection technologies, in terms of what is currently working well and what is needed to effectively inform coastal zone managers, as well as guide adaptive scientific sampling of the coastal zone. Specifically the goals of this workshop were to: 1) summarize current regional requirements and future targets for metal monitoring in freshwater, estuarine and coastal environments; 2) evaluate the current status of metal sensors and possibilities for leveraging emerging technologies for expanding detection limits and target elements; and 3) help identify critical steps needed for and limits to operational deployment of metal sensors as part of routine water quality monitoring efforts. Following a series of breakout group discussions and overview talks on metal monitoring regulatory issues, analytical techniques and market requirements, workshop participants made several recommendations for steps needed to foster development of in situ metal monitoring capacities: 1. Increase scientific and public awareness of metals of environmental and biological concern and their impacts in aquatic environments. Inform scientific and public communities regarding actual levels of trace metals in natural and perturbed systems. 2. Identify multiple use applications (e.g., industrial waste steam and drinking water quality monitoring) to support investments in metal sensor development. (pdf contains 27 pages)

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Surface- and bottom-water samples were collected from October 1996 to August 1997 to study levels of iron, copper, and cadmium species in their dissolved labile as well as non-labile and particulate forms in the waters of El-Mex Bay. The results showed that the non-labile concentration of the metals was generally more abundant than that of the labile form: its content reached more than 90% of the total dissolved metal for Cu and more than 80% for Fe. The particulate form was almost at the level of the labile form. The annual concentration of the trace metals of the labile form was 13 µglˉ¹ for Fe; 3µglˉ¹ for Cu, and 1.2 µglˉ¹ for Cd in the surface- and bottom-waters.

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ENGLISH: The thread herrings, genus Opisthonema, family Clupeidae, are marine fishes that occur only in tropical and subtropical waters off both coasts of the American continent. The genus is composed of one Atlantic species and four Pacific species. Opisthonema oglinum (LeSueur), the single species in the western Atlantic Ocean, occurs from Brazil to Massachusetts, at Bermuda, and throughout the West Indies. Opisthonema libertate (Günther), Opisthonema bulleri (Regan), and Opisthonema medirastre, new species, are Pacific coastal species which occur together from Peru to Mexico (with at least one occasionally in California). Opisthonema berlangai, new species, is confined to the vicinity of the Galapagos Islands. SPANISH: Los arenques de hebra, género Opisthonema, familia Clupeidae, son peces marinos que se encuentran sólo en aguas tropicales y subtropicales cerca a ambas costas del continente americano. El género está compuesto de una especie en el Atlántico y de cuatro en el Pacifico. Opisthonema oglinum (LeSueur), única especie que medra el Océano Atlántico occidental, se encuentra del Brasil a Massachusetts, en Bermuda, y las Indias Occidentales. Opisthonema libertate (Günther), Opisthonema bulleri (Regan), y Opisthonema medirastre, especie nueva, son especies costaneras del Pacífico que aparecen entremezcladas del Perú a México (ocasionalmente por lo menos una de ellas en California). Opisthonema berlangai, especie nueva, está confinada a la vecindad de las Islas Galápagos.

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The Alliance for Coastal Technology (ACT) convened a workshop on the in situ measurement of dissolved inorganic carbon species in natural waters in Honolulu, Hawaii, on February 16, 17, and 18, 2005. The workshop was designed to summarize existing technologies for measuring the abundance and speciation of dissolved inorganic carbon and to make strategic recommendations for future development and application of these technologies to coastal research and management. The workshop was not focused on any specific technology, however, most of the attention of the workshop was on in situ pC02 sensors given their recent development and use on moorings for the measurement of global carbon fluxes. In addition, the problems and limitations arising from the long-term deployment of systems designed for the measurement of pH, total dissolved inorganic carbon (DIC), and total alkalinity (TA) were discussed. Participants included researchers involved in carbon biogeochemistry, industry representatives, and coastal resource managers. The primary questions asked during the workshop were: I. What are the major impediments to transform presently used shipboard pC02 measurement systems for use on cost-eficient moorings? 2. What are the major technical hurdles for the in situ measurement of TA and DIC? 3. What specific information do we need to coordinate efforts for proof of concept' testing of existing and new technologies, inter-calibration of those technologies, better software development, and more precise knowledge quantzjjing the geochemistry of dissolved inoeanic carbon species in order to develop an observing system for dissolved inorganic carbon? Based on the discussion resulting from these three questions, the following statements were made: Statement No. 1 Cost-effective, self-contained technologies for making long-term, accurate measurements of the partial pressure of C02 gas in water already exist and at present are ready for deployment on moorings in coastal observing systems. Statement No. 2 Cost-effective, self-contained systems for the measurement of pH, TA, and DIC are still needed to both fully define the carbonate chemistry of coastal waters and the fluxes of carbon between major biogeochemical compartments (e.g., air-sea, shelf-slope, water column-sediment, etc.). (pdf contains 23 pages)

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In a semi-urbanized stretch of river Kubanni, Zaria, seasonal variations of some tree metals (copper, zinc and lead) in fish species (Clarias sp., Tilapia sp and Alestes sp) were investigated over a period of eight months. Water and fish were sampled monthly, pooled separately and seasonal analysis of each trace determined using atomic absorption method. The concentration of each of the elements in water higher in the dry season than during the rainy season. The dry and rainy season concentrations of copper, zinc and lead were 6.85~c10.66 mu gg super(-1)&1.45~c1.10 mu gg super(-1); 2.13~c1.68 mu gg super(-1)&0.1 5~c0.05 mu gg super(-1); and 0.52~c0.50 mu gg super(-1) & 0.31~c0.14 mu gg super(-1) respectively. Similarly, all the three accumulated more zinc and lead in the dry season than during the rainy season. Tilapia species and to some extent, Alestes species being pelagic had a higher concentration of trace metals than Clarias species which is a bottom dwelling fish Tilapia species may therefore be a better indicator species than Clarias species for monitoring trace metals in water bodies. Reasons for the observed variations in the trace metals were discussed

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The research was carried out to assess the trace metal concentration in sediments of ship breaking area in Bangladesh. The study areas were separated into Ship breaking Zone and Reference Site for comparative analysis. Metals like Iron ( Fe) was found at 11932 to 41361.71µg.g-1 in the affected site and 3393.37 µg.g-1 in the control site. Manganese (Mn) varied from 2.32 to 8.25 µg.g-1 in the affected site where as it was recorded as 1.8 µg.g-1 in the control area. Chromium(Cr), Nickel (Ni), Zinc(Zn) and Lead (Pb) were also varied from 22.89 to 86.72 µg.g-1; 23.12 to 48.6;83.78 to 142.85 and 36.78 to 147.83 µg.g-1 respectively in the affected site whereas these were recorded as 19; 3.98; 22.22 and 8.82 µg.g-1 in the control site. Copper (Cu); Cadmium (Cd) and Mercury (Hg) concentration were varied from 21.05 to 39.85; 0.57 to 0.94 and 0.05 to 0.11 µg.g-1 in the affected site and 33.0; 0.115 and 0.01 µg.g-1 in the control site. It may conclude that heavy metal pollution in sediments at ship breaking area of Bangladesh is at alarming stage.

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The chemical speciation of both metals and non-metals, the use of polarographic techniques, and application to the study of the chemistry of anoxic waters are considered. In the first part of the paper unfamiliar terminology is explained and then an example of simple lake chemistry is presented to illustrate why the concept of speciation is necessary.