CROSS-REFERENCE TO RELATED APPLICATION

This is a continuation of copending U.S. provisional application Ser. No. 60/079,978, filed on Mar. 30, 1998.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to a method and system to facilitate phytoremediation, especially to permit phytoremediation to be conducted at depths beyond those traditionally employed.

2. Description of the Related Art

U.S. Pat. No. 5,829,192 utilizes a tree in order to have its root system aid in the remediation of contaminated soil and groundwater, which constitutes phytoremediation.

The only step in the process of that patent which differs from the normal planting of a tree is, however, is “providing a casing made of material which is impervious to water and nutrients for root growth, and lining the walls of the hole [in which the tree is planted] with such casing . . . ”

The purpose of the casing is stated to be “so that root growth is inhibited from growing outside of the prepared hole.”

However, no provision is made to encourage root growth below the depth at which roots are normally produced.

Phillip Craul wrote in

Urban Soil in Landscape Design

(1992) that “[m]ost roots occur within the surface 3 ft. (1 m) of . . . soils . . . as the result of . . . proximity of favorable root growth conditions . . . ”

But the critical need for rooting at depths below 3 feet for trees employed in phytoremediation is evident from the facts that contaminants often exist or extend below such depth and that the greatest potential for contamination of drinking water occurs at lower depths.

Previous attempts to encourage deep rooting have mistakenly only considered the need of trees for nutrients and water.

SUMMARY OF THE INVENTION

The present invention, however, recognizes that favorable growth of root systems requires aeration, gaseous exchange, and decreased soil compaction in addition to nutrients and water.

Besides providing the preceding, the present invention has appreciated the fact that the germination and growth of mycorrhizae spores not only creates macro pores through which root hair can pass, but the fungus resulting from such germination and growth also creates a pathway for nutrients to reach the root hair.

Furthermore, the present invention optionally directs forced air to deep areas where it is desired to establish root systems. Such forced air also opens macro pores in soil.

Additionally, to encourage root growth in desired areas, the trunk can be coated in those areas with either vitamin B1 or mycorrhizae spores or a combination of these substances. And in order to create optimal growing conditions in areas at various elevations along the trunk, these areas can be separated by horizontal clay layers. The clay layers preclude oxygen from drifting to the top of the hole in which the tree has been planted and preclude water nutrients from flowing to the bottom of the hole. (Of course, air, nutrients, and water will be supplied to each region between clay layers.)

Similarly, to prevent growth in specific areas, either (a) the trunk can be wrapped with epdm rubber or a biobarrier or (b) the region around the trunk in such areas can be backfilled with gravel so that it will contain no nutrients or water together with an overabundance of air or (c) both techniques can be implemented.

The preceding technologies enable the hole where the tree is planted to be deeper than previously possible and, therefore, enable the tree to perform phytoremediation much farther below grade than has been achieved prior to development of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1

depicts the basic system for facilitating deep phytoremediation.

FIG. 2

shows the trunk of a tree wrapped with material that is impermeable to roots in order to preclude the growth of roots where such roots are not desired within the hole in which the tree has been planted for photoremediation and also demonstrates the use of clay layers.

FIG. 3

is a cross-sectional view from above of the basic system for facilitating deep photoremediation.

FIG. 4A

is a lateral view of a drip irrigation tube.

FIG. 4B

shows an air compressor connected to the drip irrigation tube.

FIG. 5A

is a lateral view of a drip irrigation tube employing a valve or drain.

FIG. 5B

is an overhead view of a drip irrigation tube employing a valve or drain.

FIG. 6A

illustrates the use of malleable, porous material such as a sponge, around the apertures or, preferably, pressure-compensating emitters of the tube that supplies air and water, attached to the trunk of a tree to encourage root growth.

FIG. 6B

portrays a drain.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In order to enable a tree to be planted lower than traditional depths and, therefore, to enable the root system of such a tree to perform phytoremediation at such depths, the present invention provides water; air; nutrients; and, optionally, gaseous exchange at the depths where it is desired to establish root systems.

A hole

1

is established, for example by excavating or drilling, beyond traditional depths for planting a tree

2

. A tree

2

is then placed in the hole

1

, and backfill material

3

is inserted around the tree

2

in the hole

1

.

As illustrated in

FIG. 1

, a tube

4

, preferably a drip irrigation tube, transports water

5

from a source of water

6

to the locations where it is desired to provide water

5

. The tube

4

has apertures

7

or, preferably, pressure-compensating emitters at locations where it is desired to provide water

5

. Using any technique that is well known in the art, such as fertilizer injectors (e.g., the E-Z Grow No. 40010HF010C Automatic Fertilizer System manufactured by the E-Z Grow Company or the Dosmatic Model No. DP30-2 Fertilizer Injector made by the Dosmatic Company) nutrients are added to the water

5

prior to such water

5

entering the tube

4

.

Several options exist for aeration and gaseous exchange.

First, passive aeration and gaseous exchange may be achieved by installing in the tube

4

above ground a valve or drain

8

. The drain is constructed so that it is open to the atmosphere when no water

5

is in the tube

4

and is automatically closed when water

5

is in the tube

4

; such drains are well known in the irrigation industry. The valve is opened manually or electrically; the electrical opening can be controlled by a timer. When the valve or drain

8

is open, air can then flow down and pass outward from the apertures or emitters

7

; and other gases can flow into the apertures or emitters

7

and proceed to the valve or drain

8

and into the atmosphere.

Second, active aeration may be achieved by connecting an air compressor

9

to the tube when it is not desired to supply water

5

. Although gases could not flow into the apertures or emitters

7

during active aeration, forced air leaving the apertures or emitters

7

also opens macro pores in soil, as discussed above, thereby creating spaces termed “macro pores” which root hairs can penetrate and which facilitate aeration.

But, whether, active or passive aeration is desired, a separate tube

10

can be provided for the air if it is not desired to have a dual purpose for tube

4

.

And, third, a U-shaped tube

11

having both its first end

12

and its second end

13

open can be installed with both ends

12

,

13

above ground and with some of the intermediate portion

14

between the ends

12

,

13

below ground and in the vicinity of the tree

2

. In the areas where it is desired to establish root systems, the U-shaped tube

11

contains apertures

15

to permit air to flow from such apertures

15

into the surrounding backfill material

3

and to permit other gases to flow into such apertures

15

from the backfill material

3

, thereby providing gaseous exchange as well as aeration.

Optionally, flow through the U-shaped tube

11

can be augmented by placing an attic circulation vent

16

, i.e., the type of vent which rotates in the wind and thereby draws air into the U-shaped tube

11

, on the first end

12

of the U-shaped tube

11

.

And a preferred option to enhance root growth and to facilitate the absorption of nutrients by the root systems is adding mycorrhizae spores

17

to the backfill material

3

. As explained above, the germination and growth of mycorrhizae spores

17

not only creates macro pores through which root hair can pass, but the fungus resulting from such germination and growth also creates a pathway for nutrients to reach the root hair. Moreover, aeration of the backfill material

3

enhances the growth of the mycorrhizae spores

17

.

Additionally, as discussed above, to encourage root growth in desired areas, the trunk

18

of the tree

2

preferably coated in those areas with either vitamin B1 or mycorrhizae spores

17

or a combination of vitamin B1 and mycorrhizae spores

17

.

Also preferably and as portrayed in

FIG. 2

, to enhance root growth even further, a malleable, porous material such as a sponge

19

is placed around the apertures or, preferably, pressure-compensating emitters

7

of the tube

4

and attached to the trunk

18

of the tree

2

. The sponge

19

aids in retaining and dispersing air as well as water

5

and, consequently, nutrients in the areas where it is desired to establish root growth. Moreover, the sponge

19

minimizes the possibility that the apertures or, preferably, pressure-compensating emitters

7

may become clogged and aids in gaseous exchange by increasing the volume available for the gathering of gases.

And one final technique is preferably employed in order to create optimal growing conditions for roots in areas at various elevations along the trunk

18

.

Also preferably and as portrayed in

FIG. 6A

, to enhance root growth even further, a malleable, porous material such as a sponge

19

is placed around the apertures or, preferably, pressure-compensating emitters

7

of the tube

4

and attached to the trunk

18

of the tree

2

. The sponge

19

aids in retaining and dispersing air as well as water

5

and, consequently, nutrients in the area where it is desired to establish root growth. Moreover, the sponge

19

minimizes the possiblity that the apertures or, preferably, pressure-compensating emitters

7

may become clogged and aids in gaseous exchange by increasing the volume available for the gathering of gases.

To retain all the elements essential for enhanced root growth within selected areas

21

where such growth is desired at various elevations along the trunk

18

clay layers

22

are inserted above all such selected areas

21

except, optionally, for the uppermost such selected area

23

and below all such selected areas except for the lowest such selected area

24

. Of course, within each such selected area

21

, there must be the means discussed above for aeration, gaseous exchange, and the supply of water and nutrients.

Conversely to the primary emphasis of the preceding discussion, there can be areas

25

around the trunk

18

in the hole

1

where root growth is not desired.

Two techniques are employed to preclude root growth. In the first technique, the trunk

18

is wrapped, as illustrated in

FIG. 3

, with material that is impermeable to roots

26

, such as epdm rubber or a biobarrier. The second technique comprises, as illustrated in

FIG. 4

, placing gravel, preferably gravel having a diameter of approximately 1.5 inches, as the backfill material

3

in the areas

25

so that the water

5

and, consequently, the nutrients will drain from such areas

25

and so that such areas

25

will have an overabundance of air to the extent that such density of air actually deters the growth of roots. Of course, if desired, these two techniques can be employed concurrently.