AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |
Back to Blog
Ag source lawrence ks12/3/2023 ![]() Thus for a limit of -5 ppm Cu (copper) the median may still be determined as 8, or perhaps even <5. When all "less than" values for an element are the same, users can still report percentiles such as the median. People argue over whether to use 1/2 the reported limit, or 0.7 times the limit, or some other multiplier. Replacement methods have no theoretical basis, and are dangerous. Or it may obscure a pattern that is present. The problem is that the value used to replace "less thans" may produce an artificial signal that is not in the original data. This is the next worst method, after deleting "less thans". The most commonly-used method is to replace all "less than" values with a replacement value. The best that can be said is that the concentration is =50 will not be affected by ignoring the "less than" values. Unfortunately, we don't know if that means that the sample contains 1.8 ppm Ag or 0.0001 ppm Ag. When the analytical method determined that a sample contained less than 2 ppm Ag, a value of "-2" was recorded in the Ag_ppm field. For example, one of the Oak Ridge Multielement Emission Spectrochemical Analysis methods could not detect concentrations of silver (Ag) that were less than 2 parts-per-million (ppm). Concentrations below this lower determination limit are too small to be detected by the method. All instrumental methods for analyzing the concentrations of various elements in sediments, waters, rocks, or plants have lower determination limits. Is there someone I can contact?Ī negative concentration value indicates that the sample was analyzed but that the concentration was below the determination limits of the analytical method. I don't see my problem listed here and I still need help.Where can I find copies of the NURE GJBX-series, PGJ/F-series, or GJQ-series publications listed in the bibliography?.I want to use these data in a report or to create a map.Can I still use the NURE HSSR data I obtained from earlier CD-ROMs or other sources? Why would I want to use these newly-reformatted data?. ![]() Is there a way to query a database and get just the data I need? I want to retrieve the reformatted NURE HSSR data from parts of several quadrangles or partial data from a large area.When will the data for this quadrangle be available? The link to the quadrangle I want isn't active.Where can I get it? Is there any more geochemical data coming? I can't find the NURE HSSR data I want for a certain quadrangle.Are the sample locations identified by site names or descriptions? How can I find the data records for just the samples I need? I need to locate samples along a certain stream or at a certain place.The latitude-longitude coordinates are expressed in decimal degrees but what datum was used?.Why do some of the latitude-longitude coordinates contain values of zero? Why not throw out those records without coordinates?.What about blank fields or values of zero for element concentrations?.How do I use the negative concentrations or "less than" values in calculations?. ![]() Why are there negative concentration values in the data? What do they mean?.Version 1.40 (2006) Frequently Asked Questions Concerning the National Uranium Resource Evaluation (NURE) Hydrogeochemical and Stream Sediment Reconnaissance (HSSR) Data and Reformatting Process ![]() National Geochemical Database-Reformatted Data from the National Uranium Resource Evaluation (NURE) Hydrogeochemical and Stream Sediment Reconnaissance (HSSR) Program ![]()
0 Comments
Read More
Leave a Reply. |