Soil Pollution - Pesticides and Industrial Waste - UNSOLVED PRACTICE SET

Q7. What are persistent organic pollutants (POPs)? Why is DDT still found in soil decades after being banned?

Q8. Differentiate between bioaccumulation and biomagnification with reference to pesticide residues in soil and food chains.

Q9. Why does excessive use of nitrogen fertilisers lead to soil acidification and water pollution?

Q10. What is soil remediation? Name two physical/chemical methods and two biological methods for cleaning polluted soil.

Q11. Your uncle is a farmer in Punjab who has been using the same pesticides for 20 years. He notices that pest attacks are increasing despite higher pesticide doses. Explain this phenomenon and suggest alternatives.

Q12. Why are heavy metals in industrial waste particularly dangerous when they contaminate agricultural soil?

Q13. Discuss soil pollution caused by pesticides:

(a) Types of pesticides — insecticides, herbicides, fungicides, rodenticides

(b) Classification based on chemical nature — organochlorines (DDT, BHC), organophosphates, carbamates, pyrethroids

(c) The mechanism of action of organochlorines and organophosphates

(d) Persistence and bioaccumulation of pesticides in soil

(e) Effects on soil microorganisms, earthworms, and soil fertility

Q14. Explain industrial waste and its impact on soil:

(a) Types of industrial waste — fly ash, slag, chemical residues, heavy metals

(b) Sources in India — tanneries (chromium), textile dyes, mining operations, smelters

(c) The Bhopal gas tragedy and its long-term soil contamination

(d) Effects of heavy metals (Cd, Pb, Hg, As, Cr) on soil properties and crop quality

(e) Case study: The lead contamination in Kolar Gold Fields, Karnataka

Q15. Soil pollution threatens India's food security and farmer livelihoods. Discuss:

(a) Why Punjab, Haryana, and western Uttar Pradesh face severe soil degradation from the green revolution model

(b) The crisis of stubble burning — why farmers burn crop residue and its impact on soil carbon

(c) India's National Policy for Management of Crop Residues and initiatives like the Happy Seeder

(d) The Zero Budget Natural Farming (ZBNF) movement in Andhra Pradesh and its potential for soil restoration

Q16. A farmer applies 100 kg of urea (CO(NH₂)₂) per hectare to his wheat field. Urea contains 46% nitrogen.

(a) Calculate the mass of nitrogen applied per hectare.

(b) If only 30% of this nitrogen is taken up by crops and 20% leaches into groundwater, calculate the mass of nitrogen entering groundwater per hectare.

(c) If the groundwater recharge is 500 m³ per hectare, calculate the nitrate concentration in groundwater and compare with the WHO limit of 50 mg/L as NO₃⁻.

Q17. Soil in an industrial area contains 50 mg/kg of lead (Pb). The safe limit for agricultural soil is 100 mg/kg, but for children's play areas it is 400 mg/kg.

(a) Assess whether this soil is safe for agriculture and for a school playground.

(b) If a child ingests 200 mg of soil daily while playing, calculate the daily Pb intake. Compare with the WHO provisional tolerable daily intake of 3.6 μg/kg body weight for a 30 kg child.

(c) If phytoremediation using sunflower plants removes 5 mg Pb per kg of plant biomass, and each plant produces 2 kg biomass, calculate how many plants are needed per hectare to reduce Pb to safe levels in 5 years. (Soil mass per hectare to 15 cm depth = 2 × 10⁶ kg)

Q18. A pesticide factory in Gujarat discharged 500 tonnes of DDT-contaminated waste into soil over 20 years. DDT has a half-life of 15 years in soil.

(a) Calculate the mass of DDT remaining after 30 years.

(b) If the contaminated area is 10 hectares and soil depth is 20 cm, calculate the DDT concentration in mg/kg. (Soil density = 1.3 g/cm³)

(c) The safe limit for DDT in soil is 1 mg/kg. Assess whether the soil meets this standard after 30 years.