To extract or not to extract? Influence of chemical extraction treatment of wood samples on element concentrations in tree-rings measured by X-ray fluorescence

Abstract

In micro-densitometry of wood it is standard procedure to extract resin and other soluble compounds before X-ray analysis to eliminate the influence of these extractives on wood-density. Dendrochemical studies using X-ray fluorescence analysis on the other hand are commonly conducted without previous extraction. However, it is well known that translocation processes of elements during heartwood formation in trees or (temporal) differences in sap content of wood samples can influence dendrochemical element profiles. This might bias environmental signals stored in time series of element concentrations in wood proxies. We hypothesize that metals tightly bound to cell walls show a more robust proxy potential for environmental conditions than easily translocated ones. To eliminate the noise of these soluble substances in wood elemental time series, their extraction prior to analysis might be necessary. In our study we tested the effect of different solvents (water, alcohol, and acetone) and different extraction times on elemental time series of three tree species with differing wood structure (Pinus sylvestris; Quercus robur and Populus tremula). Micro-XRF analysis was conducted on nine replicates per species using an ITRAX-Multiscanner. A set of elements commonly detected in wood (S, Cl, K, Ca, Ti, Mn, Fe, and Ni) was analysed at high resolution before and after several extraction runs. Besides lowering their levels, extraction did not significantly change the temporal trends for most elements. However, for some elements, e.g., Potassium, Chlorine or Manganese, especially the water extraction led to significant decreases in concentrations and altered temporal trends. Apparently the dipole effect of water produced the strongest extraction power of all three solvents. In addition we observed a dependency of extraction intensity from wood density which differed between wood types. Our results help in interpreting and evaluating element profiles and mark a step forward in establishing dendrochemistry as a robust proxy in dendro-environmental research.

Wood decomposers on six community timber species in two different locations

“…Pine and acacia have the highest wood density (0.60), while sengon has the lowest (0.32). The density of wood is influenced by the level of density and the content of natural chemicals (Scharnweber et al 2023). Wood with a high wood density generally has a denser structure and lower moisture content.…”

Critical Analysis of the Past, Present, and Future of Dendrochemistry: A Systematic Literature Review

“…However, if a paper had a roughly equal number of co-authors from two different counties, each country was considered a primary representative of that paper [67][68][69]. Recently, there have been several publications with co-authors affiliated with institutions from around the world; these studies were considered multinational (Figure 2a) [13,70,71]. The United States and Canada have published by far the majority of dendrochemistry studies (Figure 2a).…”

“…Other studies focused on specific isotopes and tracer elements [83][84][85][86][87][88][89][90]. Many studies focused on a handful of elements to identify environmental changes, either through acidification or the addition of heavy metals [71,[91][92][93][94][95][96][97][98]. However, most studies looked at the general elemental profile of tree samples to identify elements of interest or of higher concentration than expected [22,68,99].…”

11th Hardwood Conference Proceedings

“…Among the available methods, the followings were employed in the cited literature: energy dispersive (EDXRF) and portable (PXRF) X-ray fluorescence (Pereira Junior. et al 2016, Ghavidel et al 2020, total reflection X-ray fluorescence (TXRF) spectrometry (De La Calle et al, 2013, Wobrauschek 2007), Micro-XRF (μXRF) (Scharnweber et al 2023). Wood, as an organic, multi-polymeric composite material, with a complex chemical composition, containing only small amounts of inorganic compounds (often less than 1%), alongside its complex microscopic and macroscopic structural features, generating anisotropic properties and variability among and within wood species, presents challenges for XRF investigations.…”