Question 11. Exposure to SO₂ containing chimney gases results in the

Question 12. The type of bacteria which is active in trickling filter during biological treatment of sewage is the __________ bacteria.

Question 13. The main type of sludge gas evolved during sewage treatment in Imhoff tank is

Question 14. There are five concentric layers within the atmosphere which is differentiated on the basis of temperature. The atmospheric layer which lies close to the earth's surface in which human being along with other organisms live is called troposphere. The rate at which air temperature in the troposphere gradually decreases with height is about __________ °C/km.

Question 15. Global warming may result in

Question 16. Ambient noise level can be reduced by __________ decibels by planting trees (like coconut, neem etc.) near public utility buildings (like hospitals & schools).

Question 17. Lead exhausted in the atmosphere by automobiles using leaded petrol (i.e. tetraethyl lead for improving octane number) is a lethal air pollutant which causes

Question 18. Which of the following industries discharge mercury as a pollutant?

Question 19. Which of the following is the most severe air pollutant?

Question 20. Pick out the one which is not a chemical coagulant.