A method for creating a gradient of aerobic, denitrifying, and methanogenic degradation sequences in a soil formation which increases overall biodegradation efficiency, and thus provides an improved method for the bioremediation of non-naturally occurring, subsurface, liquid contaminants from one or more soil formations, comprising:
- a) pneumatically fracturing the soil formation, comprising:
- i) inserting a tubular probe partially into the soil such that at least one orifice of a nozzle fluidly connected with the tubular probe is positioned at a predetermined height;
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- ii) supplying a pressurized gas into the tubular probe such that the pressurized gas travels through the at least one orifice into the soil to produce a fracture network in said soil formation;
- and simultaneously with creation of said fracture network, or subsequently thereafter:
- b) inserting into said fracture network and thereby throughout adjacent portions of said soil formation, a pressurized gas stream, and introducing a mixture of one or more liquid amendments, selected from the group consisting of nutrients for growth of aerobic and other microorganisms, buffering compounds, and inoculum comprising aerobic and other microorganisms which are able to degrade said contaminants, and optionally water, into said pressurized gas stream, wherein said pressurized gas, in conjunction with said liquid amendments and optionally water, has an oxygen or other electron acceptor content sufficient to promote the growth of aerobic or other microorganisms in said fracture network and adjacent portions of said soil formation, and wherein said pressurized gas stream has a sufficiently high gas to liquid ratio to atomize said liquid amendments, whereby said amendments are distributed throughout said fracture network and adjacent soil formation;
- c) as necessary, repeating steps a) and b) on a sequential basis in order to treat additional portions of the soil formation(s), and on a periodic basis in order to replenish said liquid amendments and oxygen or other electron acceptor to said fracture network and adjacent portions of said soil formation(s);
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- d) maintaining a low volume flow of a pressurized gas throughout said fracture network and adjacent portions of said soil formation(s) by means of reduced pressure exerted thereon, wherein said pressurized gas has an oxygen content sufficient to promote the growth of aerobic microorganisms, whereby the gradient of microbial degradation is promoted, increasing the overall efficiency thereof.