12. Care should be taken to prevent cross contamination between adjacent samples (within groups) before and during the process of taking FIDLER readings and collecting the soil samples. Record whether each soil sample is taken from: a) b) c) d) e) desert pavement blow sand mound wash area rodent mound other (describe) 14, Sample should always be collected unless prevented by a physical obstruc- 15. If a sample cannot be collected due to a physical obstruction then skip that group of four samples and add an additional group of four at the eastern end of the line, maintaining the appropriate spacing (20 or 150 ft for Lines 1 or 2, respectively. 16. Record the weights of the soil samples: tion (concrete pad, lumber, old animal pens, etc.). a) b) Dry weight before ball-milling Weight of the total ball-milled fraction 17. Dry and ball-mill samples according to established NAEG procedures. Do not sieve. 18. Assign unique library numbers to each of the 120 samples. 19. Take two 70-g aliquots from each ball-milled sample. aliquot numbers to all 240 aliquots. 20. Store remaining ball-milled soil from each sample. number and aliquot number. 21. Count for 241 (GeLi) on each aliquot. Assign unique Label with library Counting time should be sufficient to attain a 2% counting error (100 x lo/count = 2.0) or up to 1000 minutes, whichever occurs first. 23. Design a data sheet to be used in the field and in the lab that provides space for all pertinent field parameters and laboratory sample preparation parameters. Any other information deemed important or pertinent to the study should be recorded perhaps as remarks. The following information should be recorded on the data sheet and in a peripheral data base: 443 ne ne tee 13.