UGC-NET (NTA) Environmental Sciences, June-2019

The wind rose is the time honoured method of graphically presenting the wind conditions, direction and speed, over a period of time at a specific location. To create a wind rose, average wind direction and wind speed values are logged at a site, at short intervals, over a period of time, e.g. 1 week, 1 month, or longer.

The collected wind data is then sorted by wind direction so that the percentage of time that the wind was blowing from each direction can be determined.

Acid rain has many baneful effects. It upsets chemical balance in water bodies, releasing toxic metals. This causes serious health problems to people. Acid rain also triggers leaching of important nutrients from the soil, affecting plants.

When snow with acid deposit melts, higher concentration of acid gets released, affecting fish. Acid rains also cause corrosion in buildings-the Taj Mahal being a case in point. The occurrence of acid rain over the Indian landmass is extremely rare because the alkaline dust and ammonia produced from agricultural areas neutralizes the acid formation in the atmosphere.

The species level is highly embedded in current ecological theory and practice. It is widely accepted that within- and betweenspecies interactions are different in kind. Niche theory is usually conjoined with a view that the species level provides a fundamental break.

Gause's theory of competitive exclusion talks about the ability of species needing to differentiate in order to live in the same environment. The species level is likewise highly embedded in studies of population genetics. The species is thought to be the largest unit in which gene flow is possible, thus the largest group that can actually evolve as a unit.

Disturbance, defined here as any process that removes biomass from the community, has long been recognized as influencing species coexistence and the maintenance of biodiversity. As a result, there is a considerable body of research examining the effects of disturbance on species diversity, much of which focuses on testing the intermediate disturbance hypothesis.

In ecology. a disturbance is a temporary change in environmental conditions that causes a pronounced change in an ecosystem. Disturbances often act quickly and with great effect, to alter the physical structure or arrangement of biotic and abiotic elements.

Disturbance can also occur over a long period of time and can impact the biodiversity within an ecosystem. Major ecological disturbances may include fires, flooding, storms, insect outbreaks and trampling.

Earthquakes, various types of volcanic eruptions, tsunami, firestorms, impact events, climate change, and the devastating effects of human impact on the environment (anthropogenic disturbances) such as clearcutting, forest clearing and the introduction of invasive species can be considered major disturbances.

Olivine has a very high crystallization temperature compared to other minerals. That makes it one of the first minerals to crystallize from a magma. During the slow. Olivine has a very high crystallization temperature compared to other minerals. That makes it one of the first minerals to crystallize from a magma. During the slow

Magma changes as crystallization takes place
along the two branches

The electromagnetic spectrum covers electromagnetic waves with frequencies ranging from below one hertz to above 1025 hertz, corresponding to wavelengths from thousands of kilometers down to a fraction of the size of an atomic nucleus.

This frequency range is divided into separate bands, and the electromagnetic waves within each frequency band are called by different names; beginning at the low frequency (long wavelength) end of the spectrum these are: radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays at the high-frequency (short wavelength) end.

The biogas production decreased with temperature decrease in winter, while acetate and propionate were accumulated. The lower biogas production in winter might be explained by poor degradation of organic matter and higher solubility of biogas at a lower temperature.

The optimum mesophilic temperature of biogas production from blends of agro-based wastes was determined under constant supply of heat. Methanogenesis occurs at mesophilic temperature.

lectrostatic precipitators are widely used to trap fine particulate matter in applications where a large amount of gas needs treatment and where use of a wet scrubber is not appropriate. Coal-burning electric generating plants and incinerators often use electrostatic precipitators.

In an electrostatic precipitator particles are removed when the dirty gas stream passes across high-voltage wires carrying a large negative voltage. The particles are electrically charged on passage past these electrodes and then migrate through the electrostatic field to a grounded positively charged collection electrode.

The collection electrode can be either a cylindrical pipe surrounding the high-voltage charging wire or a flat plate, like that shown in Figure.

The major drivers for the development of fuel cell technology are efficiency and low emissions. The efficiency of fuel cells versus the internal combustion engine is often misrepresented. These two technologies are intrinsically different and have different efficiency-power characteristics.

While an internal combustion engine has the maximum efficiency at or near its maximum power, the fuel cell system has its maximum efficiency at partial load. Because of that, the efficiency of a hydrogen-fuelled fuel cell propulsion system in a typical driving schedule, where an automobile engine operates most of the time at partial load, is approximately twice that of an internal combustion engine.

If another fuel is used (such as methanol or gasoline) and reformed onboard, the efficiency of a fuel cell propulsion system is lower than the efficiency of a hydrogen fuel cell system, although still higher than the efficiency of the internal combustion engine.