NEXT Plant data: Results of Quality Assurance and Quality Control - Supplementary material for publications based on this data set

<strong>Format:</strong> <em>HTML document (bookdown format)</em><br> <strong>Purpose:</strong> <em>This file provides a detailed description of the quality assurance and quality control (QA/QC) procedures applied to the plant concentration data collected during the study. It includes statistical analysis of reference materials, drift correction, uncertainty modeling, and evaluation of laboratory and field precision.</em> <strong>Description of the File Content</strong> This file is part of a larger data publication and serves as a supplementary document to the main dataset. It outlines the QA/QC procedures used to ensure the accuracy, precision, and reliability of the plant element concentration data. The file includes: <strong>Reference Material (RM) Analysis:</strong> Statistical summaries of standard reference materials (SRMs) such as UPDEEP_SPRU_BARK_DRY, UPDEEP_SPRU_TWIG_DRY, and UPDEEP_SPRU_NEED_DRY. Comparison of pre-analyzed SRM values with actual measurements. X-charts showing the performance of SRMs over time and across different batches. <strong>Drift and Offset Correction:</strong> Visualizations of raw and corrected data for routine samples, laboratory, and field replicates. Analysis of data trends and correction of analytical drift and offsets. <strong>Uncertainty Modeling:</strong> Calculation of relative standard deviation (RSD) from laboratory replicates. Identification of elements with high uncertainty (RSD &gt; 10%) that may be excluded from further analysis. Tables and visualizations showing the distribution of uncertainties across different plant tissues. <strong>Field Precision Assessment:</strong> Evaluation of field replicate data to assess variability in field sampling. Identification of elements with poor field precision (RSD &gt; 20%). <strong>Data Preparation and Processing:</strong> R code for data loading, cleaning, and transformation. Use of packages such as <code>data.table</code>, <code>ggplot2</code>, <code>dplyr</code>, and <code>kableExtra</code> for data manipulation and visualization. <strong>Summary of Key Findings and Data Included</strong> <strong>Reference Materials:</strong> The file provides statistical summaries (mean, median, SD, RMAD) of SRMs used to monitor analytical performance. These are compared with actual measurements to assess accuracy and precision. <strong>Drift Correction:</strong> The data shows the effect of drift correction on plant concentration measurements, improving the consistency of results across different batches. <strong>Uncertainty Analysis:</strong> The RSD of laboratory replicates is calculated, and elements with high variability are flagged for exclusion. <strong>Field Precision:</strong> Field replicates are used to assess the variability of sampling and analysis in the field, with some elements showing poor precision. <strong>Visualizations:</strong> The file includes numerous plots (e.g., X-charts, scatter plots) to illustrate data trends, comparisons, and uncertainty levels.