Sources of Soil Pollution

Introduction

Soil, though often overlooked, is a critical component of the earth and is essential for human existence. From an environmental fate perspective soil is clearly a well-defined, though highly variable, environmental compartment. It serves as the major source of food production for humans.

Compared to air or water pollution, soil pollution is much less apparent and its sources cannot be easily detected. These could be two of several reasons why it is much less frequently mentioned in the literature. However, concerns about soil pollution have increased in recent decades because of some famous cases in which soil pollution has caused detrimental impacts on populations and the environment. In fact, soil pollutants have decreased soil biodiversity and deteriorated large areas of agricultural land around the globe. Human health is also at risk due to the high concentration of pollutants found in soils and food produced in polluted lands. It is claimed that almost 25% of the soil worldwide is highly degraded, whereas 44% soil is moderately degraded (Tripathi et al., 2015).

Soil pollution is a broad term that refers to the accumulation of native or introduced substances in soil at a harmful level for the growth and health of organisms (micro-organisms, plants, animals and human beings). However, the term “soil contamination” describes only the introduction of a chemical substance that is not originally present in the soil (De Haan & Van Riemsdijk, 1986). However, many regulatory and non-regulatory programs and assessments use soil pollution and soil contamination as equivalent terms.

In this chapter we use the term soil pollution to mean the presence of a substance, either introduced or native, above the threshold level.

Some of the common types of wastes that lead to the development of soil pollution include municipal wastes, commercial wastes, ashes, non-biodegradable wastes, biodegradable wastes and animal wastes.

Soil pollution may arise from a wide range of sources that can be discrete point sources (commercial activities), or diffuse sources (sprayed pesticides and air deposition). The pollution process itself may be deliberate, as in the case of fertilization processes or following accidents such as oil spills in seawater. Each source has specific characteristics, briefly presented below.

Overall, pollutants find their way to the soil via the air path (dry deposition); the water path (sewage water, precipitation, irrigation water, surface water and wet deposition); and via organic solids, such as sewage sludges, composts and other agricultural inputs (fertilizers, manure or plant-protection agents) (Auerswald et al., 2000).

The most dangerous categories of soil pollutants are the persistent organic compounds such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyl (PCBs) and pesticides as well as heavy metals such as lead, cadmium, arsenic, mercury, zinc, copper and radionuclides. New soil pollutants, such as veterinary medicines and surfactants, have emerged with industrialization and globalization.

This chapter deals with sources of soil pollution, pollutants generated from these sources and their possible adverse effects on the environment.