Project 1: Determining maximum loading limit for copper in agricultural land

Project 1: Determining maximum loading limit for copper in
agricultural land

Introduction:
Copper is used for various purposes like utensils, electric wiring, fungicides etc. Repeated application of copper containing fungicides for long time, particularly in orchards has been found to enhance copper concentration to a toxic level. This element is known to have significant adverse effect on plant growth and soil beneficial microorganisms. Excessive copper can make people ill when ingested. Copper toxicity in humans takes the form of stomach upset, nausea, and diarrhea. Generally, metals are strongly immobilized (or inactivated) by soil constituents and thereby, their toxic effects are not expressed. However, each soil has a definite metal immobilizing capacity, depending on their characteristics; which is therefore, considered as an important soil quality indicator. Once, this immobilizing capacity limit (commonly known as, loading limit) is exceeded, metals start showing their toxicity effect and have potential to contaminate food and groundwater. Through this activity, children can estimate the loading limits of metal for the land area nearby their locality.
Objectives:
1. To estimate the loading limit of copper for a land
2. To understand symptoms of copper toxicity in spinach plant
3. To compare clayey soil and sandy soil for loading limit of copper
Materials required:
Pots of uniform sizes (4 – 5 litre capacity), spinach seeds, balance, wooden log, copper sulphate, data sheet, pencil
Methodology:
1. Collect about two bags of soil each from a cultivated land (preferably clayey or any heavy textured soil) and a sandy soil (or any light textured soil) from a river bank
2. Dry the soils under sun
3. Pulverize the soils with wooden log
4. Fill 10 pots with 3 kg of same type of soil. Apply graded doses of copper sulphate (ranging from 80 to 1200 mg/kg). So there will be a total of 20 pots.
5. Add sufficient amount of water to moisten the soil and keep the pots in shade for 3 days.
6. Mix the soil of the pot thoroughly on a polythene sheet and then refill the pot
7. Sow 15 to 20 seeds of spinach on each pot and apply water slowly with sprinkler to moisten the soil.
8. After a week of germination of seeds, keep only 5 seedlings and remove the rests.
9. Observe the seedlings growth and note down the yellowing of leaves if they appear.
10. The preceding dose of copper application where toxicity symptoms appears on the spinach plant is considered as maximum loading capacity of the soil
11. Compare the loading limits of these two soils and explain the reasons for the difference.
Relevance:
Knowledge on metal loading limits will help in decision making by policy makers for giving permission for new industries known to generate metal containing effluents and also for deciding upon waste disposal sites so that the metal does not contaminate food and water