Method for quantitative calibration of in situ optical chemical measurements in soils using soil class and characteristics

A method for the in situ quantification of chemicals of interest in a soil sample by optical methods comprising:

• determining optical chemical response factors for chemicals of interest which are added in known amounts to discrete soil matrices (types) and conditions (moisture content, for example) under controlled laboratory conditions to provide predetermined optical chemical response factor reference signals;
• coupling said predetermined optical chemical response factor reference signals to a processor having the capability to store said predetermined optical chemical response factor reference signals therein;
• providing a combination probe having an optical chemical sensor having the capability to produce chemical sensor signals representative of a chemical of interest in said soil sample and further having a strain gauge sensor having the capability to produce strain gauge signals representative of soil type of said soil sample;
• inserting said combination probe into said soil sample;
• producing said chemical sensor signals in said optical chemical sensor and said strain gauge signals in said strain gauge sensor, simultaneously and in parallel;
• transmitting said chemical sensor signals and said strain gauge signals to said processor;
• and
• correlating said chemical sensor signals and said strain gauge signals with said predetermined optical chemical response factor reference signals in said processor to provide said in situ quantification of said chemicals of interest in said soil sample, said correlating involving the use of said strain gauge signals representative of said soil type of said soil sample to select a chemical response factor from said predetermined optical chemical response factor reference signals, said chemical response factor being indicative of a chemical of interest in a particular soil type of said soil sample, to provide said in situ quantification of said chemicals of interest from said chemical sensor signals of said soil sample.