Page 161 - Soil Degradation, Conservation and Remediation

150 6 Soil Pollution

plants, animals, and humans. Soil pollution arises mainly from disposal of solid
and liquid wastes in the ground; disposal of chemical wastes from the industries
into the soil; indiscriminate use of agricultural chemicals, including fertilizers
and pesticides; application of sewage sludge and compost without judging
metal contamination; leakage of underground septic tanks into the soil; use of non-
decomposable materials; mining activity; and irrigation with polluted water.

6.2 Sources of Soil Pollutants

According to Alloway ( 1995 ), various wastes, industrial, municipal, agricultural,
domestic, and nuclear, are the chief sources of soil pollution. Wastes are materials
that have reached the end of their useful life (Hill 2010 ). All wastes are not necessarily
a pollutant. Many wastes can be recycled into useful materials again. Plastic and
paper wastes can be converted to newer products. Excreta of animals are excellent
manures. Crop residues can be effectively used for protection against erosion.
However, most wastes are considered useless and often disposed of carelessly.

6.2.1 Municipal Waste

The DOE ( 2002 ) defines municipal waste as waste from households, as well as
other waste, which, because of its nature or composition, is similar to waste from
households. Municipal wastes include domestic and kitchen wastes, market wastes,
hospital wastes, livestock and poultry wastes, slaughterhouse wastes, and metals,
glass, and ceramic wastes. Municipal wastes can be grouped into fi ve different
categories: biodegradable (food and kitchen waste such as meat trimmings or
vegetable peelings, yard or green waste, and paper), recyclable materials (glass,
plastic bottles, other plastics, metals, and aluminum cans), inert waste (construction
and demolition wastes; inert materials are those that are not necessarily toxic to
all species but can be harmful or toxic to humans. Therefore, construction and
demolition waste is often categorized as inert waste), composite waste (clothing
and plastics), and hazardous wastes (medicines, paint, batteries, light bulbs, fertilizer
and pesticide containers, and e-waste like old computers, printers, and cellular
phones). Some of these wastes are nonbiodegradable materials such as polyethylene
and plastic sheets, bags, and bottles. These materials clog soil pores and hamper
natural drainage, tillage, and planting operations.
Municipal wastes may contain nonbiodegradable organics and heavy metals.
There are a number of different ways in which cities dispose of their waste. The fi rst
and most well known, however, are dumps. These are disposal on open ground.
More commonly used today to protect the environment, however, are landfi lls.
These are areas that are specially created so waste can be put into the ground with
little or no harm to the natural environment through pollution. Today, landfi lls