Environmental Engineering (Part-2) (General Engineering) (SSC JE)

An octave band is a frequency band with upper and lower cutoff frequencies having a ratio of 2.

• The cut of frequencies of 707 and 1414 Hz define an octave band, whose band center frequency is 1000 Hz and would be referred to as the 1000 Hz octave band.

The CO₂ concentration in the atmosphere was 355 ppm in 1990 that is increasing at a rate of 1.5 ppm. In the 1960s, the annual growth averaged about 0.8 ppm per year. It doubled to 1.6 ppm per year in the 1980s.

The gaseous mixture of the troposphere is called air containing oxygen, nitrogen and carbon dioxide, all of which cycle in nature through biogeochemical cycles.

• Most of the organisms make use of these gases not only to liberate chemical energy from food during respiration, but in different ways, eg. Plants use CO₂ in photo synthesis and nitrogen is used by nitrogen fixing bacteria of the roots of some plants.

Alkalinity is a measure of the ability of water to neutralize acids. It is due to the presence of weak acids, weak and strong bases. The major portion of the alkalinity in natural water is caused by hydroxyl, carbonate and bicarbonate ions.

• The alkalinity results are presented in terms of mg/l CaCO₃. It can be evaluated by the titration curves of strong bases and sodium carbonate.

A most parabola number method is practised for the qualitative and quantitative water to determine microorganisms presence (mainly coliform) "MPN" is an acronym for most probable number, multiple tube fermentation test or MPN method determines the quality of water by quantifying the number of coliforms in 100 ml of the water sample.

The air pollution sources can be classified mainly as physical, chemical and biological sources, secondly as natural and anthropogenic sources further on climate change relevant or not. The physical pollution of the atmosphere is a consequence energy input like sound and heat energy.

• The most relevant physical pollution sources are the direct thermal pollution natural or anthropogenic.

• The local climate is changes by heat (caloric input) generated by industry, household, agricultural and transportation and the air from the lower atmosphere will have an increased local temperature.

• The sound pressure level is expressed in decibel. Sound pressure becomes 0 dB when the pressure level is the same as that of the reference pressure level. • Sound loudness is commonly measured in units of dB SPL (Sound pressure level) instead of sound power.
• The sensitivity of the human ear to sound level depends on the frequency.

• The green house effect is the natural warming of the earth that results when gases in the atmosphere trap heat from the sun that would otherwise escape into space.

• The main gases responsible for the green house effect include Carbon dioxide, Methane, Nitrous oxide and Water vapor in addition to these natural compounds synthesis fluorinated gases also function as green house gases.

• It is the solid component of the earth consisting of soil, rocks, mountains etc. The outer most (8-40 km) thick solid part of the earth is called the crust.

• The uppermost part of the earth's crust contains weathered rocks as well as organic matter and is called soil. This is the most important part of lithosphere because we grow plants on this part it is also a storehouse of minerals.

Photochemical smog–

• Which is also known as 'Los Angles smog' occurs most prominently in urban areas that have large numbers of automobiles.

• A type of air pollution derived from vehicular emission from internal combustion engines and industrial fumes reacted in the atmosphere with sunlight to form secondary pollutants that combination with primary emissions to form photochemical smog.