Laser Trimming Tree-Ring Cores for Dendrochemistry of Metals

Abstract

This article discusses the application of laser to trim the outer surface from tree-ring increment cores in preparation for dendrochemistry of certain metals. A source of contamination specific to dendrochemistry of metals is metal constituents, such as iron, tungsten, chromium, nickel, and cobalt, coming off tools used to collect and process cores and adhering to the sample surface. One method to eliminate this contamination is to trim off the outer surface of cores using laser. To test this application of laser, three tree-ring increment cores were collected from each of three trees. For each tree, one core was trimmed using a CO2 laser, one core was trimmed using a stainless steel razor blade, and one core was left untrimmed. The resultant cores were measured for metals using acid dissolution inductively coupled plasma mass spectroscopy. Trimmed cores had on average one-third the content of iron, tungsten, and chromium than that of untrimmed cores. Laser-trimmed cores had less of these metals than razor-trimmed cores. Razor-trimmed cores also had measurable nickel, but laser-trimmed cores had no nickel. Laser trimming is an ideal solution to potential contamination of cores with metals from increment borers without imparting other contamination from tools such as razor blades.