Application of Waste to Soils

Definition of Waste

"Wastes are materials that are not prime products (that is productsproduced for the market) for which the generator has no further usein terms of his/her own purposes of production, transformation orconsumption, and of which he/she wants to dispose. Wastes maybe generated during the extraction of raw materials, theprocessing of raw materials into intermediate and final products, the consumption of final products, and other human activities. Residuals recycled or reused at the place of generation areexcluded."

United Nations Statistics Division (UNSD)

• municipal solid waste (MSW)

• construction waste and demolition waste (C&D)

• institutional waste, commercial waste,

and industrial waste (IC&I)

• medical waste (also known as clinical waste)

• hazardous waste, radioactive waste, and electronic waste

• biodegradable waste

The European Union defines waste as an object the holder discards, intends to discard or is required to discard his waste under the Waste Framework Directive

Schematic illustration of the EU Legal definition of waste

Whenever humans act in any kind of productionwaste in any kind will be produced.

This waste can be of a solid, liquid or gaseous phase.

What can we do with waste?

• Prevent it• Re-use it• Recycle it• Incinerate it and use the energy and heat• Landfill it

The aim of this course is to study the possibleconsequences of the application of waste to soils.

In order to fully understand the mode of action of waste to soils we need to understand the nature and the functions of soils.

?Functions and related processesdepend on thevarying nature of diffrent soils

Waste rock piles

Radionuclides

Liquid manures Compost application

Nitrogen input

The world

is a heterogeneous place and so

are the diffe

rent soils

and their p

roperties!

ftp://ftp.fao.org/agl/agll/faomwsr/wsavcl.jpg

It depends on the kind of waste if we need to think:

local(e.g. wanted application of liquid manure)

or supra-regional(e.g. unwanted application of radio nuclides)

Soils are natural bodies.

Soils form a part of the uppermost living crust of the earth.

Soils are in the center of the sphere-concept

A soil is a natural body consisting of layers (horizons) of mineral and/or organic constituents of variable thicknesses, which differ from the parent materials in their morphological, physical, chemical, and mineralogical properties and their

biological characteristics.

(Joffe 1949, after Birkland 1999)

Definitions

Observations and much careful subsequent field and laboratory research led to the recognition of five major factors that control the formation of soils.

1. Parent materials (geological or organic precursors to the soil)

2. Climate (primarily precipitation and temperature)

3. Biota (living organisms, especially native vegetation, microbes, soil animals and human beings)

4. Topography (slope, aspect and landscape position)

5. Time (the period of time since the parent materials became exposed to soil formation)

S = pm * c * b * to * ti (Dokutschajew 1883)

Soil, the relatively thin organic-mineral entity at the Earth's surface, forms at the interface between the atmosphere and lithosphere by the assimilation of energy. The sun not only warms the Earth's surface which increases the rate of chemical reactions, but also drives the photosynthetic production of biomass. Death and decay of biomass results in the accumulation of humus in the upper horizon(s) of soil. Soil formation is also driven by the weathering of minerals in the lithosphere which releases energy utilized in soil development and nutrients that are essential for the growth of plants. Gravitational energy provides the driving force for the infiltration and percolation of water into and through the Earth's surface. The magnitude of humus accumulation, mineral weathering, and translocation or leaching of solutes and colloids by water moving through the lithosphere plays a major role in differentiating the great diversity of soils that cover the face of the Earth.

Soils vary greatly in their characteristics and potential to meet human needs. The most essential function of soil from a human perspective is that soil serves as the reservoir of water and nutrients essential for sustained plant growth. Plants serve as our food, either via direct production of fruit, vegetables, and grain, or indirectly as feed for livestock. Soils also serve as the foundation for societal infrastructure and as a medium for the disposal and amelioration of wastes. The regional and global differences in soil characteristics and potentials for use are due to differences in energy fluxes in the various ecosystems of the world. The objective of this chapter is to discuss the evolution of soils as a function of time and factors that result in the

Definitions

Additions

Inputs of materials to the developing soil profile from outside sources are considered additions. A very common example is the input of organic matter from fallen plant leaves and sloughed-off roots (the carbon having originated in the atmosphere). Another ubiquitous addition is dust particles falling on the surface of the soil (wind may have blown these particles from a source just a few meters away, or across the ocean). Still another example, common in arid regions, is the addition of salts or silica dissolved in the groundwater and deposited near or at the soil surface when the rising water evaporates.

LossesMaterials are lost from the soil profile by leaching to groundwater, erosion of surface materials or other forms of removal. Evaporation and plant use causes losses of water. Leaching and drainage causes the loss of water, dissolved substances such as salts or silica weathered from parent minerals or organic acids produced by microorganisms or plant roots. Erosion, a major loss agent, often removes the finer particles (humus, clay and silt), leaving the surface horizon relatively sandier and less rich in organic matter than before. Organic matter is also lost by microbial decomposition.Grazing by animals or harvest by people can remove large amounts of both organic matter and nutrient elements. Of course, animals and people can also contribute additions, such as manure and fertilizers.

Translocations involve the movement of inorganic and organic materials laterally within a horizon or vertically from one horizon up or down to another. Water, either percolating down with gravity or rising up by capillary action (see Section 5.2), is the most common translocation agent. The materials moved within the profile include dispersed fine clay particles, dissolved salts, and dissolved organic substances. Translocations of materials by soil organismsalso have a major influence on soil genesis. Important examples include incorporation of surface organic litter into the A and B horizons by certain earthworms, transport of B and C horizon material to the surface by mound-building termites, and the widespread burrowing actions of rodents.

Transformations occur when soil constituents are chemically or physically modified or destroyed and others are synthesized from the precursor materials. Many transformations involve weathering of primary minerals, disintegrating and altering some to form various kinds of silicate clays. As other primary minerals decompose, the decomposition products recombine into new minerals that include additional types of silicate clays and hydrous oxides of iron and aluminum. Other important transformations involve the decomposition of organic residues and the synthesis of organic acids, humus and other products. Still other transformations change size (e. g., physical weathering to smaller particles) or arrangement (e. g., aggregation) of mineral particles.

Birkeland 2003

33

• Brady, N. C. and Weil, R. (2002): The Nature and Properties of Soils. Prentice Hall, New Jersey/USA. (ISBN 0-13-852444-0)