Which of the following is a major pollutant found in contaminated soil ?

Nitrogen oxides

Solution

The correct answer is (c).

Introduction

While heavy metals are certainly significant soil pollutants, total petroleum Hydrocarbons (TPH) are often cited in specific regulatory frameworks as the most ubiquitous major pollutant in contaminated soils, primarily resulting from leaking underground storage tanks, pipeline ruptures, and industrial spills.

Information Booster

Hydrocarbons include a vast array of organic compounds composed of carbon and hydrogen, such as benzene, toluene, ethylbenzene, and xylene (BTEX), as well as polycyclic aromatic hydrocarbons (PAHs).
These pollutants strongly adsorb to soil particles and are notoriously persistent, severely altering the soil's microbial ecology and physical properties.
Hydrocarbon contamination poses a severe threat of leaching down into underground aquifers, contaminating drinking water reserves.
Remediation of hydrocarbon-contaminated soil often employs bioremediation techniques, where specialized microbes degrade the organic pollutants.
Historically, the rapid global expansion of the petroleum industry in the 20th century led to thousands of 'brownfield' sites saturated with these compounds.

Additional Knowledge

Nitrogen oxides (NOx) are primarily atmospheric pollutants (gases) contributing to smog and acid rain; they are not typically classified as soil contaminants, though they can deposit as nitrates.
Heavy metals (like Lead, Arsenic, Cadmium) are indeed major, highly toxic soil pollutants (often from mining and smelting); however, depending on the specific exam key context, hydrocarbons represent the massive bulk volume of industrial petrochemical soil contamination globally.
Mineral oil is a specific, narrower sub-category of hydrocarbons (distillates of petroleum); 'Hydrocarbons' is the correct, comprehensive scientific category encompassing all such organic contaminants.
Historically, events like the Exxon Valdez oil spill demonstrated how catastrophic hydrocarbon contamination is, heavily influencing modern soil protection legislation.