Chemistry 3 Marks Question

The environment around us is made up of chemical species which undergo chemical reactions constantly e.g., photosynthesis in plants, formation of ozone in stratosphere, etc. Environmental chemistry deals with the study of such reactions which take place in the origin, transport and life-cycle of chemical species in the environment.

While a compost pit can be a blessing for the agricultural field since it produces manure, it can also be source of trouble in the form of flies, foul odour and home for growth of bacteria, however, the negative effects can be done away with by making the pit at a place away from the residential area preferably somewhere in the field itself. Equally important is covering the pit with a suitable, lid to prevent foul odour. In such a way one can derive the benefits of a compost pit while negating the disadvantages.

Depending upon the nature of the waste, domestic waste can be segregated into two categories i.e., biodegradable and non–biodegradable. Biodegradable waste such as leaves, rotten food, etc. should be deposited in landfills, where they get decomposed aerobically and an aerobically into manure. Non-biodegradable waste (which cannot be degraded) such as plastic, glass, metal scraps etc. should be sent for recycling.

The amount of dissolved oxygen present in water is limited. The abundance of phytoplanktons causes depletion of this dissolved oxygen. This is because; phytoplanktons are degraded by bacteria present in water. For their decomposition, they require a large amount of oxygen. Hence, they consume the oxygen dissolved in water. As a result, the BOD level of water drops below 6 ppm, inhibiting the growth of fish and causing excessive fish-kill.

BOD is the measure of level of pollution caused by organic biodegradable material in terms of how much oxygen will be required to break down the organic material biologically. Clean water would have BOD values less than 5 ppm while highly polluted water could have a BOD value of 17 ppm or more.

1. Nutrients of many fertilizers like phosphates and nitrates are main cause of eutrophication. They usually enter lake through streams. In the presence of these nutrients, the population of algae increases. Since this algae provide food supply, the population of many aquatic animals increases which leads to decrease in dissolved oxygen.
2.  

1. It causes inhibition of enzymatic activity.
2. Lead effects impairment of kidney function and neurological disorder.

Water containing algae have a very less amount of oxygen as the algae consume most of the oxygen dissolved in the water, and thus deprive aquatic plants and oxygen of it, and hence kill them. This results in eventual loss of biodiversity and thus, the balance of nature is broke. This is a kind of pollution it makes happen.
This condition is called- Eutrophication.
Some algae even produce toxins that are harmful to higher forms of life.
P.S.- Algae are formed mostly by addition of chemical fertilisers containing phosphates, which enhance algae growth)

The improper disposal of wastes os one of the major caises of environment pollution. If domestic waste is not properly managed, it may go to sewers or may be eaten by cattle. Non-biodegradable wastes like, metals, glass, polythene etc, may choke the sewers or gut of the ruminants. Polythene bags if swallowed by cattle may result in their death. Similarly, if industrial waste is not properly managed it will lead to air, water and soil pollution.

Disposing of waste material and washing clothes in lake water makes the water rich in nutrients like phosphate. It enhances algae growth. Such profuse algal growth covers the water surface which reduces oxygen concentration in water. This leads to anaerobic conditions with accumulation of dead and decaying water animals, thus, leaving the water with stinking smell and making it unusable.

Oxygen reaches water either through atmosphere or from the process of photosynthesis carried out by many aquatic green plants during day light. However, during night, photosynthesis stops but the plants continue to respire, resulting in reduction of dissolved oxygen. The dissolved oxygen is also used by microorganisms to oxidize organic matter.
In brief, sources of dissolved oxygen in water are:

1. Photosynthesis by aquatic plants.
2. Due to the direct contact of water surface with air.
3. Mechanical aeriation.

1.  

1. Mercury inhibits the catalysis of general metabolic reaction because it combines with many enzymes.
2. It damages the neurons of nervous system in the brain.

2. Global warming leads to rise in seal level because with increase in temperature, melting of glaciers takes place. It is one of the outcome of global warming.

Pesticides are organic compounds which are used to protect plants from pests. These are mild poisons. These pesticides stick to the plants and also flow into lakes along with the rain water. Rearing fishes when consume these plants as their food the poisonous pesticides accumulate in the tissues of fishes. Thus, these fishes are not fit for human consumption.