Abstract: This technique for detecting underground contamination by organic fluids employs a plurality of spaced-apart boreholes adjacent a region to be tested for contamination. A neutron backscatter gauge is introduced into each of the boreholes for measuring the concentration of hydrogen in the soil surrounding the borehole. Such measurements are made at a plurality of spaced elevations along such a borehole and the distribution of hydrogen concentration as a function of elevation is compared with the expected distribution of hydrogen from underground sources of hydrogen, for distinguishing organic fluid contamination from other sources of hydrogen. For example, one can distinguish buried concrete or underground water from organic contamination. Measurements can also be made using chemical analysis methods. In another embodiment, the invention is used to profile and affect biodegradation. A plurality of spaced apart boreholes are provided in the buried material (for example, dump site).