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The “charcoal effect” on Pi detectors
Eric has given one explanation as to why charcoal or more particularly the effects of fire can result in underground burnt tree roots giving a signal on a Pi.
But there is another explanation too. Tree roots of course take up water and many minerals and anionic chemical species like Nitrates, Phosphates, Silicates, Halogens and anionic species of Fe, Cu, and Zn etc and in some cases even Au. All of these chemical species are concentrated in the tree roots up to 10,000 fold higher concentrations than the surrounding soil matrix. When the tree roots are burnt these CONDUCTIVE species are immobilized in the charcoal matrix of the former tree roots.
So what does all this mean as far as our Pi detectors go? These former roots now have a localized area of CONDUCTIVE salts that is very much more conductive than the surrounding soil matrix. When there is a change in soil resistively i.e. an increase in conductivity Em methods like TDEM can detect this change. It is the very basis for using EM methods for finding underground aquifers, salt affected lands or non metallic high sulphide ore bodies. Our Pi is no different and it responds appropriately by telling us it senses the presence of a conductive target in this case a non metallic conductive target. I am staggered that Paul is apparently unaware of this fact.
Here are some web sites for further reading:
http://www.hasgeo.com/tdem.htm
http://gsc.nrcan.gc.ca/mindep/method...cs/index_e.php
http://www.hgg.geo.au.dk/pdf/danielsen2002a.pdf
http://www.technos-inc.com/pdf/SurfaceTechnotes.pdf
http://www.cast.uark.edu/nadag/Educa.../EM/Dalan1.pdf
http://www.geophysics.dias.ie/mtnet/...ew_SG_2002.pdf
http://www.geoinfosol.com/Geoscience/TDEMArticle.htm
http://www.geo.vu.nl/users/swim/pdf/swim16/barrocu.pdf
http://www.cseg.ca/publications/jour..._modelling.pdf
http://www.geoexplo.com/Geophysics_links.html
http://www.beg.utexas.edu/staffinfo/...ageep03_em.pdf
http://www.st-andrews.ac.uk/~www_sgg...eb/GWATER1.pdf
http://www.balkangeophysoc.org/onlin...s_fin_1_11.pdf
http://www.enviro-net.com/main.asp?p...r=fl&year=1996
http://www.worleyparsonsgpx.com.au/SOPAC_TDEM-appl.pdf
http://www.cseg.ca/conferences/2004/..._Oil_Sands.pdf
http://www.itc.nl/library/Papers/msc...eg/tsiboah.pdf
http://www.skytem.dk/fileadmin/paper...ics_SkyTEM.pdf
http://www.skytem.dk/fileadmin/paper...esentation.pdf
http://www-geo.phys.ualberta.ca/~uns...424C6-2005.pdf
There are hundreds of other sites for TDEM geophysical exploration.
ElectroNovice
Eric has given one explanation as to why charcoal or more particularly the effects of fire can result in underground burnt tree roots giving a signal on a Pi.
But there is another explanation too. Tree roots of course take up water and many minerals and anionic chemical species like Nitrates, Phosphates, Silicates, Halogens and anionic species of Fe, Cu, and Zn etc and in some cases even Au. All of these chemical species are concentrated in the tree roots up to 10,000 fold higher concentrations than the surrounding soil matrix. When the tree roots are burnt these CONDUCTIVE species are immobilized in the charcoal matrix of the former tree roots.
So what does all this mean as far as our Pi detectors go? These former roots now have a localized area of CONDUCTIVE salts that is very much more conductive than the surrounding soil matrix. When there is a change in soil resistively i.e. an increase in conductivity Em methods like TDEM can detect this change. It is the very basis for using EM methods for finding underground aquifers, salt affected lands or non metallic high sulphide ore bodies. Our Pi is no different and it responds appropriately by telling us it senses the presence of a conductive target in this case a non metallic conductive target. I am staggered that Paul is apparently unaware of this fact.
Here are some web sites for further reading:
http://www.hasgeo.com/tdem.htm
http://gsc.nrcan.gc.ca/mindep/method...cs/index_e.php
http://www.hgg.geo.au.dk/pdf/danielsen2002a.pdf
http://www.technos-inc.com/pdf/SurfaceTechnotes.pdf
http://www.cast.uark.edu/nadag/Educa.../EM/Dalan1.pdf
http://www.geophysics.dias.ie/mtnet/...ew_SG_2002.pdf
http://www.geoinfosol.com/Geoscience/TDEMArticle.htm
http://www.geo.vu.nl/users/swim/pdf/swim16/barrocu.pdf
http://www.cseg.ca/publications/jour..._modelling.pdf
http://www.geoexplo.com/Geophysics_links.html
http://www.beg.utexas.edu/staffinfo/...ageep03_em.pdf
http://www.st-andrews.ac.uk/~www_sgg...eb/GWATER1.pdf
http://www.balkangeophysoc.org/onlin...s_fin_1_11.pdf
http://www.enviro-net.com/main.asp?p...r=fl&year=1996
http://www.worleyparsonsgpx.com.au/SOPAC_TDEM-appl.pdf
http://www.cseg.ca/conferences/2004/..._Oil_Sands.pdf
http://www.itc.nl/library/Papers/msc...eg/tsiboah.pdf
http://www.skytem.dk/fileadmin/paper...ics_SkyTEM.pdf
http://www.skytem.dk/fileadmin/paper...esentation.pdf
http://www-geo.phys.ualberta.ca/~uns...424C6-2005.pdf
There are hundreds of other sites for TDEM geophysical exploration.
ElectroNovice