Tackling soil pollution through a multidisciplinary approach

Introduction

Soil is a thin cover over the land, a mixture of minerals, organic matter, living organisms, air and water that supports plant life. Soil pollution occurs when chemicals, salts or wastes build up in it and damage that capacity. Environmental Studies is multidisciplinary by design, as the DU course states at its opening, and this suits soil pollution well.

Why soil pollution needs many disciplines

The harm is at once chemical (what is in the soil), biological (what it does to living things) and human (why farmers and cities put it there). A chemist alone can measure a pesticide but cannot change a farmer's reasons for spraying it; an economist can explain those reasons but cannot say how long the residue lasts. Addressing the problem therefore means joining their findings into one plan: identify the pollutant, trace its effects, change the practice, and enforce the change.

What each discipline contributes

Chemistry identifies the pollutant and how long it stays. Persistent pesticides do not break down easily, so they accumulate in soil and also attach to fine particles that wind and water carry elsewhere. DDT's half-life is 10 to 15 years in temperate regions and may be as short as six months in the tropics, and it varies with soil type, temperature and soil organisms. Such data show which chemicals most need restricting.

Ecology and biology show what is being damaged. Bacteria, fungi and earthworms in the upper soil layers form food webs that recycle nutrients. Most pesticides kill useful species along with pests, including the predators that keep pests down, so pests can rebound, and insects can become resistant within a couple of generations. Residues also build up in animals and concentrate further up the food chain, which is biomagnification. Biology also offers biopesticides such as neem and Bacillus thuringiensis.

Agricultural science changes the practice on the field. Crop rotation raises fertility and controls pests, and working crop residue back into the soil adds organic matter and reduces erosion. It also tackles salinization, in which irrigation water evaporates in dry climates and leaves salts such as sodium chloride in the topsoil, stunting crops and eventually making the land useless.

Health sciences measure the human cost and so set priorities. Small exposures to pesticides over several years can cause mutations and cancers, and both the people who spray and the people who eat the food are at risk.

Economics explains the behaviour and tests the remedies. Farmers use pesticides because higher yields more than repay the cost. Critics say organic farming pays only in some conditions; supporters reply that it pays once the hidden costs of erosion and pollution are counted, and that organic farmers save on inputs and earn a premium price. An incentive that ignores these numbers will fail.

Engineering keeps waste out of the soil. For example, a landfill taking processing residues, mixed waste or waste contaminated with hazardous materials must have a composite liner of 1.5 mm HDPE geo-membrane (or geo-synthetic liners, or equivalent) over 90 cm of low-permeability soil, with leachate collected and treated.

Law and public administration make these findings binding. The same engineering requirement is a legal standard in the Solid Waste Management Rules, 2016, so a local body cannot treat it as optional.

Conclusion

No single subject can clean a polluted field. Chemistry finds the pollutant, ecology and health sciences show the harm, agricultural science and engineering supply the remedies, and economics and law make them last. That combination is what the multidisciplinary approach means in practice.