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(...) What is Dissolved Oxygen?
Some oxygen is dissolved in practically every liquid. For example, at a temperature of 68°F (20°C) and an atmospheric pressure of 1013mbar saturated water contains about 9mg/L oxygen. Ethanol can contain up to 40mg/L whereas glycerol only has about 2mg/L.
Each liquid takes up oxygen until the partial pressure of oxygen in the liquid is in equilibrium with the air or gas phase in contact with it. The actual oxygen concentration depends on a number of factors, such as temperature, air pressure, oxygen consumption by microorganisms in a biodegradation process or oxygen production by algae, etc.
The oxygen concentration is important for the:
• Living conditions for fish and microorganisms in waters;
• Degradation processes in wastewater treatment;
• Corrosion processes in pipelines;
• Shelf life of beverages, etc.
The determination of the dissolved oxygen concentration was formerly carried out by the WINKLER titration method. Today electrochemical measurement is a recognized method in numerous standard procedures.
In its simplest form a dissolved oxygen electrode contains a working electrode and a counterelectrode. Both dissolved oxygen electrodes are located in an electrolyte system which is separated from the sample by a gaspermeable membrane. The working dissolved oxygen electrode reduces the oxygen molecules to hydroxide ions. In this electrochemical reaction a current flows from the counterelectrode to the working dissolved oxygen electrode. The more dissolved oxygen present in the sample, the larger the current signal generated by the dissolved oxygen electrode. A meter connected to the dissolved oxygen electrode calculates the oxygen concentration in the sample from this signal.
Why Measure DO?
Dissolved oxygen (DO) is the amount of oxygen (O2) dissolved in water. Dissolved oxygen measurements provide one of the best indicators of the health of a water ecosystem, as oxygen is a necessary element for all forms of life, including aquatic life. Oxygen enters water at the water surface through direct exchanges with the atmosphere. It is also produced as a byproduct of plant and phytoplankton photosynthesis. A decrease in dissolved oxygen levelsis typically associated with an organic pollutant. Dissolved oxygen is used by plants and animals for respiration, and by aerobic bacteria in the process of decomposition. When organic matter (such as animal waste or improperly treated wastewater) enters a body of water, algae growth increases. As the plant material dies off and decomposes, dissolved oxygen levels decrease. If the water at the surface is not mixed with deeper water layers, the water's dissolved oxygen levels can become stratified. Dissolved oxygen levels can also vary according to the time of day, weather, and temperature. Dissolved oxygen in water can range from 0-18 parts per million (ppm), but most natural water systems require 5-6ppm to support a diverse population. As dissolved oxygen levels drop below 5.0mg/L, aquatic life is put under stress. As dissolved oxygen levels decrease, pollution-intolerant organisms are replaced by pollution-tolerant worms and fly larvae. If dissolved oxygen levels fall below 1- 2mg/L for a few hours, large fish kills can result. (...)
A análise da Concentração de Oxigênio Dissolvido (COD) é um dos melhores indicadores da saúde do ecossistema aquático. A partir dessa assertiva e da análise do texto exposto, é incorreto afirmar:
Provas
(...) What is Dissolved Oxygen?
Some oxygen is dissolved in practically every liquid. For example, at a temperature of 68°F (20°C) and an atmospheric pressure of 1013mbar saturated water contains about 9mg/L oxygen. Ethanol can contain up to 40mg/L whereas glycerol only has about 2mg/L.
Each liquid takes up oxygen until the partial pressure of oxygen in the liquid is in equilibrium with the air or gas phase in contact with it. The actual oxygen concentration depends on a number of factors, such as temperature, air pressure, oxygen consumption by microorganisms in a biodegradation process or oxygen production by algae, etc.
The oxygen concentration is important for the:
• Living conditions for fish and microorganisms in waters;
• Degradation processes in wastewater treatment;
• Corrosion processes in pipelines;
• Shelf life of beverages, etc.
The determination of the dissolved oxygen concentration was formerly carried out by the WINKLER titration method. Today electrochemical measurement is a recognized method in numerous standard procedures.
In its simplest form a dissolved oxygen electrode contains a working electrode and a counterelectrode. Both dissolved oxygen electrodes are located in an electrolyte system which is separated from the sample by a gaspermeable membrane. The working dissolved oxygen electrode reduces the oxygen molecules to hydroxide ions. In this electrochemical reaction a current flows from the counterelectrode to the working dissolved oxygen electrode. The more dissolved oxygen present in the sample, the larger the current signal generated by the dissolved oxygen electrode. A meter connected to the dissolved oxygen electrode calculates the oxygen concentration in the sample from this signal.
Why Measure DO?
Dissolved oxygen (DO) is the amount of oxygen (O2) dissolved in water. Dissolved oxygen measurements provide one of the best indicators of the health of a water ecosystem, as oxygen is a necessary element for all forms of life, including aquatic life. Oxygen enters water at the water surface through direct exchanges with the atmosphere. It is also produced as a byproduct of plant and phytoplankton photosynthesis. A decrease in dissolved oxygen levelsis typically associated with an organic pollutant. Dissolved oxygen is used by plants and animals for respiration, and by aerobic bacteria in the process of decomposition. When organic matter (such as animal waste or improperly treated wastewater) enters a body of water, algae growth increases. As the plant material dies off and decomposes, dissolved oxygen levels decrease. If the water at the surface is not mixed with deeper water layers, the water's dissolved oxygen levels can become stratified. Dissolved oxygen levels can also vary according to the time of day, weather, and temperature. Dissolved oxygen in water can range from 0-18 parts per million (ppm), but most natural water systems require 5-6ppm to support a diverse population. As dissolved oxygen levels drop below 5.0mg/L, aquatic life is put under stress. As dissolved oxygen levels decrease, pollution-intolerant organisms are replaced by pollution-tolerant worms and fly larvae. If dissolved oxygen levels fall below 1- 2mg/L for a few hours, large fish kills can result. (...)
A Concentração de Oxigênio Dissolvido (COD) é um importante parâmetro para determinar as características químicas e biológicas da água. A partir da análise do texto acima exposto, não é possível afirmar:
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Precautions for Instrument Inspection, Maintenance, Adjustment and Care: “Warning”
• Unplug the instrument before inspection, maintenance, or parts replacement. Otherwise, electrical shock or short-circuit accidents could occur;
• Never remove the main cover. This may cause injury or malfunction of the instrument. The main cover does not need to be removed for routine maintenance, inspection and adjustment;
• If the power cord plug gets dusty, remove the plug from the power outlet and wipe away the dust with a dry cloth. If dust is allowed to accumulate, fire could result;
• Replacement parts must be of the specifications given in "1.1 UV-1800 Configuration" and "6.2 Maintenance Parts" in the System User's Guide. Use of any other parts may result in instrument damage and malfunction;
• If any water gets onto the instrument, wipe it away immediately to prevent rust. Never use alcohol or thinner solvents for cleaning the instrument. They could cause discoloration;
• Dispose waste liquid properly and in accordance with the instructions of your administrative department.
A precaução e cuidado para utilização do equipamento que não consta da lista acima é:
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Care of the microscope
• Hold a microscope firmly by the stand, only. Never grab it by the eyepiece holder, for example;
• Hold the plug (not the cable) when unplugging the illuminator;
• Since bulbs are expensive, and have a limited life, turn the illuminator off when you are done;
• Always make sure the stage and lenses are clean before putting away the microscope;
• Never use a paper towel, a kimwipe, your shirt, or any material other than good quality lens tissue or a cotton swab (must be 100% natural cotton) to clean an optical surface. Be gentle! You may use an appropriate lens cleaner or distilled water to help remove dried material. Organic solvents may separate or damage the lens elements or coatings;
• Cover the instrument with a dust jacket when not in use;
• Focus smoothly; don't try to speed through the focusing process or force anything.
O cuidado com microscópios que não consta na lista acima é:
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(...) “GOOD PRACTICE GUIDELINES: The following general guidelines indicate the care and maintenance required:
1. After Use - Rinse thoroughly with distilled water. Short Term Storage – Immerse in storage solution (025 192) Long Term Storage – Fit wetting cap filled with storage solution (025 192) and replace in original packaging;
2. Electrodes should be stored: a) away from direct sunlight, b) in a vertical position, c) within their specified temperature range;
3. Always ensure the electrode is used within its specified temperature range. Ageing of electrodes used above their specified temperature is rapid and irreversible;
4. DO NOT touch the sensitive glass pH membrane or reference junction. Excess droplets of solution may be removed by gently blotting with filter paper or tissue. DO NOT rub the electrode as this may induce an electrostatic charge;
5. During use ensure the electrode is rinsed between each measurement to eliminate the contamination of solutions”. (...)
Nessa parte do Manual de Operação, com as orientações gerais de manutenção e cuidados indicados, a orientação que não está presente nos itens 1 a 5 é:
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(...) “Calibration is required to accurately weigh items with an electric balance. Calibration must be performed in these conditions:
• when the location of the installation site is changed (even when moved within the same room);
• when the room temperature changes;
• also, daily calibration before use is recommended”. (...)
De acordo com tais instruções, a calibração obrigatória da balança deve:
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Reflexos autonômicos são também conhecidos como reflexos viscerais por frequentemente envolverem órgãos internos. Sobre os reflexos viscerais, é incorreto afirmar:
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As subdivisões do Sistema Nervoso Autônomo, simpática e parassimpática, compartilham algumas características e distinguem-se por outras. Assinale a alternativa correta:
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A ativação do sistema nervoso simpático é muito mais ampla do que a do sistema nervoso parassimpático devido a quais condições?
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Em mamíferos, a termo-regulação é coordenada pelo:
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Caderno Container