GB2521164A

GB2521164A - Method for remediation of arid soils

Info

Publication number: GB2521164A
Application number: GB1321871.4A
Authority: GB
Inventors: Enrico Dini
Original assignee: MONOLITE UK Ltd
Current assignee: MONOLITE UK Ltd
Priority date: 2013-12-10
Filing date: 2013-12-10
Publication date: 2015-06-17
Also published as: GB201321871D0

Abstract

A method for remediation of arid soils comprises enclosing a portion of arid soil 100 having a bottom surface 101 within embankments 102 forming a closed loop; providing in the enclosed portion at least a shading structure 103 configured to at least partly intercept and mitigate solar irradiation; waterproofing the bottom surface of the enclosed portion of arid soil and at least part of the embankments; filling the waterproofed enclosed portion of arid soil with landfill soil 107 to a predetermined height relative to the bottom surface, thereby forming a raised ground level of the enclosed portion of arid soil; supplying to the landfill soil an adjustable flow of water 111; and controlling the level reached by water relative to the waterproofed bottom surface by providing the embankments or the shading structures or both with adjustable overflow outlets for water at a depth between the bottom surface and the raised ground level.

Description

METHOD FOR REMEDIATION OF ARID SOILS

The present invention relates to a method for remediation of arid soils, particularly in desert areas.

There are several vast desert areas on our planet. Some of them formed naturally, yet many of them have progressively turned to desert because of human activities. Human activities have been causing desertification ever since ancient times, and their impact has grown more and more intense with the increase in population.

It is known that desertification contributes to generating major imbalances of both environmental and social nature, such as climate tropicalization and the generation of migration flows towards more rainy and fertile lands.

Several techniques are known for reclaiming desert areas. In general, they aim at making an arid soil suitable for farming. This goal can partly be achieved by intense irrigation, yet this practice does not lead to a permanent greening of a desert area.

Further, several methods are known for greening, recovery and preservation of a territory. Some of these methods aim at preventing soil erosion, whereas others attempt to retain moisture in the most superficial layers of the ground.

However, these methods have certain drawbacks. First of all, it may take quite a long time to attain the full greening of the territory. It may even take several decades to obtain acceptable results. Further, the territory thus revived has typically a low economic value.

Furthermore, it would be desirable to create a forest and obtain, accordingly, the shading of the soil. Shading would provide comfort for both animals and favourable conditions for many undergrowth plants, because it mitigates transpiration and perspiration. Therefore, shading represents an added value even in an open environment. However, shading cannot be achieved with conventional techniques of desert reclamation.

It would therefore be desirable to provide a method for permanent remediation of arid soils that can make an extensive intervention on a territory profitable. In particular, it would be desirable to provide one such method that aims not only at exploiting the territory to be remedied for farming, but also one that makes the territory appealing for other anthropic activities, thereby vastly increasing its value. Even more so, it would be desirable to provide a method for permanent remediation of arid soils that is compatible with the creation of infrastructures such as to make the territory suitable for the performance of human activities under comfortable conditions.

According to the present invention, there is. provided a method for remediation of arid soils, particularly in desert areas, the method comprising: -enclosing a portion of arid soil having a base ground level within embankments forming a closed loop, the base ground level defining a bottom surface of the enclosed portion of arid soil; -providing in the enclosed portion of arid soil at least a shading structure configured to at least partly intercept and mitigate solar irradiation; -waterproofing the bottom surface of the enclosed portion of arid soil and at least part of the embankments; -filling the waterproofed enclosed portion of arid soil with landfill soil to a predetermined height relative to the base ground level, thereby forming a raised ground level of the enclosed portion of arid soil; -supplying to the landfill soil an adjustable flow of water; and -controlling the level reached by water relative to the waterproofed bottom surface by providing the embankments or the shading structures or both with adjustable overflow outlets for water, the overflow outlets being placed at a depth between the base ground level and the raised ground level.

Throughout this specification, the term "arid soil" shall be used to mean that the soil is in a region characterised by a severe lack of available water, to the extent of hindering or preventing the growth and development of plant and animal life. In more detail, the water that is actu ally present in the environment may be sufficient for some species or usages, yet grossly insufficient for others. Aridity may thus also depend on the intended use of the land. As concerns the presence of life, even more important than the degree of rainfall is the fraction of precipitation that is not quickly lost through evaporation, percolation or runoff. In general, arid regions typically have more evapotranspiration than precipitation.

According to the method of the present invention, in an arid region, the ground level is locally raised above the original elevation of the region by forming a layer of landfill soil above ground. Evaporation of water from the layer of landfill soil is mitigated by local shading of portions of the area being remedied. Percolation of irrigation water and rainwater into deeper layers of the ground is prevented by waterproofing the original ground level surface of the area being remedied. At the same time, selective discharge of excess water from the landfill soil is attained by providing, and controlling operation of, adjustable overflow outlets arranged at a height relative to the original ground level that is below the artificially raised, new ground level.

In practice, by varying the flow rate of water supplied into the landfill soil and by adjusting the flow rate of water discharged via the overflow outlets, the height of the water table relative to the original elevation of the region may conveniently be regulated. Thus, farming and other human activities in the remedied region can advantageously be performed in an environment that. provides sufficiently comfortable conditions for plants. animals and human beings.

It shall be understood that, especially in areas where desert storms are frequent, it may be possible to collect a portion of the sand transported by the wind and use it to form the layer of landfill soil. For example, this may be achieved by intercepting wind-borne sand by means of droplets of water sprayed from a given height. Accordingly, the amount of landfill soil that needs to be delivered to the site being remedied may advantageously be reduced.

Advantageously, the height of the embankments is such that the embankments contribute to mitigating evaporation of water dispersed in the landfill soil. Depending on the latitude of the portion of arid soil being remedied and on the local availability of water, the height of the embankments is preferably from about I m to about 3 m relative to the base ground level of the portion of arid soil.

The shading structure preferably comprises a support element extending transversal to bottom surface of the enclosed portion and a plurality of shading elements projecting from the support element. The size and spatial arrangement of the shading elements are preferably such as to intercept at least 20% of the average daily solar radiation. Thus, the shading structure advantageously mitigates evaporation of water from the soil and plant transpiration, thus reducing the amount of water that needs to be actively supplied to the landfill soil for maintenance of plant life. Further, by shading the area, the shading structure advantageously reduces perspiration of animals and human beings inhabiting the portion of arid soil being remedied, thereby increasing their overall comfort level. More preferably, the size and spatial arrangement of the shading elements are such as to intercept at least 25% of the average daily solar radiation, even more preferably such as to intercept at least 30% of the average daily solar radiation.

The height of the shading structure(s) is preferably from about 20 m to about 40 m relative to the base ground level of the portion of arid soil. The cross section of the support element may have a large diameter, preferably from about 300 cm to about 600 cm. Thus, the overall shading effect is advantageously increased. I Advantageously,' the support element of the shading structure may be built using the locally available sand by means of three-dimensional printing techniques.

Advantageously, the shading structure may be provided, for example at its top end, with water diffusing means in order to create artificial rains. Thus, the underlying portion of soil may advantageously be humidified and cooled down. Advantageously, the water diffusing means may further be selectively activated on windy days to abate to the ground any solid particles carried by the wind. Thus, the amount of landfill soil that needs to be transported to the site to form the raised ground level may advantageously be reduced.

Advantageously, the shading structure can be used for supporting lights. Preferably, the shading elements are equipped with photovoltaic panels. Even more preferably, the shading elements are fitted with photovoltaic panels made of flexible material(s).

Further, the shading elements may be movable so as to assume different spatial positions relative to the support element or to the bottom surface of the enclosed portion of arid soil or relative to both. To this purpose, the shading elements may be motorised. Thus, the shading elements may be able to intercept and mitigate solar irradiation for a longer time during the day or over a larger area or both.

Further, the shading elements may be retractable into the support element of the shading structure in case of intense meteorological events such as desert storms.

Advantageously, the support element of the shading structure may be hollow. Thus, the support element of a shading structure may be employed as an inhabitable space or for storage or for accommodating pieces of equipment. Further, the support element of the shading structure may be configured to function as a cooling chimney.

Preferably, the method further comprises planting trees in the enclosed portion of desert, so that their roots extend into the portion of landfill above the depth of the overflow outlets.

Thus, real trees and plants may contribute to further reducing solar irradiation at the raised ground level, as well as to preserving the humidity content of the landfill soil.

By waterproofing the base ground level of the enclosed portion of arid soil, percolation of water into the deeper layers of the ground is advantageously prevented. Accordingly, the plant roots can easily access humid soil at all times. The amount of water necessary for irrigation is thus advantageously reduced. Further, the landfill soil provided over the waterproofed base ground level may advantageously be enriched with an organic fertiliser.

Advantageously, the degree of opening of the overflow outlets can be adjusted so as to selectively vary, on a localised basis, the height of the raised water table. In practice, by varying the local water discharge rate, more or less water can be retained in the higher layers of the landfill soil. Thus, roots of different plants having different size and properties can stock up water in an optimal manner.

Advantageously, for irrigation purposes, water coming from civil wastewater depuration plants can be supplied to the landfill soil. This also has the advantage that the organic fraction of the landfill soil can be enriched in inexpensive fashion.

Advantageously, the decrease in temperature caused by the shading structure and the presence of real trees or plants provide the basis for the performance of all human activities. In particular, it shall be appreciated that buildings may advantageously be built over the raised ground level in a portion of arid soil remedied according to the invention.

The invention will be further described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a schematic side view of a portion ofarid soil remedied according to the method of the present invention; and Figure 2 is a schematic side view of a shading structure for use in a method according to the present invention.

Figure 1 illustrates a portion 100 of arid soil having a base ground level 101 that defines its bottom surface. Embankrnents 102 forming a closed loop enclose the portion 100 of arid soil. Shading structures 103 are provided in the enclosed portion 100 to at least partly intercept solar irradiation. Each shading structure 103 comprises a support element 104 extending substantially vertically and a plurality of shading elements 105 projecting from the support element 104. The number and spatial arrangement of the shading elements 105 are selected such that the shading structures 103 intercept 20% of the daily solar radiation in the enclosed portion 100.

The bottom surface or the portion 100 and the embankments 102 are waterproofed by means of a water impermeable liner 106. Percolation of irrigation water and rainwater into layers below the base ground level is thus substantially prevented.

Landfill soil 107 fills the waterproofed enclosed portion of arid soil up to a raised ground level 108. As illustrated in greater detail in Figure 2. controlled overflow outlets 109 are provided in the embankments 102 and/or in the vicinity of support elements 104 of the shading structures 103 to regulate the level of water, including irrigation water and rainwater, that accumulates in the landfill soil 107. The overflow outlets 109 are placed ata depth between the base ground level 101 and the raised ground level 108, so as to define a raised water table 110.

By adjusting the degree of opening of the overflow outlets over time, the height of the raised water table 110 relative to the base ground level can be selectively varied in different portions of the landfill soil 107, so as to be able to meet different localised farming requirements.

Adjustable means 111 for supplying irrigation water to the landfill soil 107 are provided (see Figure 1). By adjusting the flow rate of irrigation water supplied to the landfill soil 107 and the flow rate of water discharged via the overflow outlets 109, the overall content of water in the landfill soil 107 may be maintained within a predetermined range. It will be appreciated that, because the shading structures 103 mitigate evaporation of water from the landfill soil, the amount of irrigation water that needs to be supplied by adjustable means 111 to the landfill soil 107 is reduced.

As illustrated in Figure 2, the shading elements 105 of the shading structure 103 are movable relative to the support element 104. More particularly, the shading elements 105 are retractable so as to at least partly fit inside the support element 104. Further, the shading elements 105 are equipped with photovoltaic panels 112 made from flexible materials.

The shading structure 103 further comprises water diffusing means 113. In the embodiment shown, water diffusing means 113 are incorporated in the shading elements 105.

Claims

CLAIMS1. A method for remediation of arid soils, particularly in desert areas, the method comprising: -enclosing a portion of arid soil having a base ground level within embankments forming a closed loop, the base ground level defining a bottom surface of the enclosed portion of arid soil; -providing in the enclosed portion of arid soil at least a shading structure configured to at least partly intercept and mitigate solar irradiation; -waterproofing the bottom surface of the enclosed portion of arid soil and at least part of the embankments; -filling the waterproofed enclosed portion of arid soil with landfill soil to a predetermined height relative to the base ground level, thereby forming a raised ground level of the enclosed portion of arid soil; -supplying to the landfill soil an adjustable flow of water; and -controlling the level reached by water relative to the waterproofed bottom surface by providing the embankments or the shading structures or both with adjustable overflow outlets for water, the overflow outlets being placed at a depth between the base ground level and the raised ground level.
2. A method according to claim 1, wherein the shading structure comprises a support element extending transversal to the base ground level and a plurality of shading elements projecting from the support element, the size and spatial arrangement of the shading elements being such as to intercept at least 20% of the average daily solar radiation.
3. A method according to claim 2, comprising moving the shading elements so as to vary their spatial positions relative to the support element or to the bottom surface of the enclosed portion of arid soil or relative toboth
4. A method according to claim 2 or 3, wherein the support element of the shading structure is built from sand by means of three-dimensional printing techniques.
5. A method according to any of claims 2 to 4, wherein the height of the at least a shading structure is from about 20 m to about 40 m relative to the base ground level of the portion of arid soil.
6. A method according to any of claims 2 to 5, wherein the support element of the shading structure has a diameter from about 300 to about 600 cm.
7. A method according to any of claims 2 to 6, wherein the shading structure comprises means for spraying devices for delivering adjustable flows of water over at least a portion of the underlying soil.
8. A method according to any preceding claim, comprising enriching the landfill soil with an organic fertiliser.
9. A method according to any preceding claim, further comprising planting trees in the landfill soil.
10. A method according to any preceding claim, further comprising building inhabitable structures on the landfill soil.