b'Environmental geophysics Environmental geophysicsto create tomographically-deriveddistribution over farmshis examples images of density contrast based on thewere taken from work he and his group passage of muons through the earth indid over land irrigated by some of the vicinity of the detectors.the huge irrigation pivots in the vast farmlands of Nebraska. His talk was Muon particles originate from thetitled Opportunities and challenges interactions of cosmic rays with thetowards integration of hydro-atoms of the upper atmosphere; they aregeophysical sensors in agriculture. partially absorbed as they pass throughAs with the talk on muon-based the atmosphere, and then the rocks, etc.techniques, much of the innovation of the near- surface; absorption increaseson which Trenton reported relates to with water content and rock density (andthe use of cosmically-sourced particles in the case of the pyramids less absorbedthat end up as fast-neutrons at the Mike Hatchby the air in hidden voids). Most of usend of cosmic ray cascades, many of Associate Editor for would have heard about an early successwhich interact with the soil. Much of the Environmental geophysicsof the technique when muons were usedfollowing, overly-simplified description michael.hatch@adelaide.edu.au to find at least one hidden room insideof the technique is based on a the Great Pyramid of Giza (Morishimapublication put out by the International etal., 2017an absolutely fascinatingAtomic Energy Agency (https://www.Webinars worth watching article in its own right).iaea.org/publications/11097/cosmic-ray-Leon mostly concentrated on theneutron-sensing-use-calibration-and-Welcome readers to this issuesvalidation-for-soil-moisture-estimation). column on geophysics applied to thepotential of the technique for mappingAnother interesting paper on the environment. In this months column I amdensity distributions in and under tailingssubject is Stevanato etal. (2019). reporting on a fascinating webinar thatdams and other mining infrastructure I saw recently. This webinar was run byin order to locate potentially lethalFast-neutrons are scattered in the top the EEGS (the US-based Environmentalvoids that would be prone to collapsemetre or two of the soil, with most and Engineering Geophysical Society) asat some time in the future. Much ofof the energy lost when the fast-part of their Talking About Geophysicsthe innovation in this space is in theneutron encounters water. The relative series (TAG: https://www.eegs.org/ development of mobile sensors that canconcentration of heavy to light neutrons tag-webinars). This is an approximatelybe used to collect this type of data (stillat the instrument is measured, and this monthly series of webinars scheduledrelatively slowly) along, for example, aratio used to estimate soil moisture over through to at least July of this year (I amhorizontal borehole. areas up to several hundred hectares sure that it will go past this date andIsobel Barton, a geometallurgist from(these fast-neutrons cover some it looks as if they are looking for newthe University of Arizona, spoke aboutdistance). In his talk he reported on contributors - in case anyone is interestedthe use of drone-based hyperspectralcombining this type of data with more in presenting). imaging in the mine environment totraditional towed-DualEM conductivity The webinar I watched featured threeassist with the determination of oredata to characterise soil moisture in speakers talking about their work ongrade, as well as the identificationareas that were pivot-irrigated to allow cutting-edge aspects of near-surfaceof potential mining issues (impurityfarmers to use their limited water geophysics. All three covered subjectsdistribution, etc.), all in somethingsupplies more efficiently.within our science that I may have heardapproaching real-time. Her biggestOverall, I found that these three talks of, but have certainly not seen applied (orissues involved the size of her data setswere well worth watching. I am hoping even contemplated applying). I am pretty(potentially collected on a nearly dailyto see this webinar come out soon as a sure that this webinar will eventuallybasis), the difficulty in processing thesepodcastand will keep you posted.be available as a webcast, but so farhuge data sets and then integrating there has been no sign of it on the EEGSand presenting the results in the mine website. context so that the images are useful toReferencesthe mine engineers. Her talk was titled Leon du Plessis, an independentMineral mapping using drone-basedMorishima K., etal. 2017 Discovery of consulting engineer, until recentlyhyperspectral imaging. a big void in Khufus Pyramid by working for Freeport McMoRan, withobservation of cosmic-ray muons, an abiding interest in using muonsTrenton Franz, a researcher workingNature, 552 (7685), pp. 386-390.as an imaging tool, gave a talk titledin the hydro-geophysics space at theStevanato L., etal. 2019. A novel Subsurface density mapping usingUniversity of Nebraska, is combiningcosmic-ray neutron sensor for soil muon technology. He spoke about thesome interesting technologies to (nearlymoisture estimation over large areas, use of extra-terrestrially sourced muonspractically) measure soil moistureAgriculture, 9 (202), pp. 1-14.JUNE 2021 PREVIEW 42'