Development and validation of in-situ and laboratory X-ray fluorescence (XRF) spectroscopy methods for moss biomonitoring of metal pollution

Abstract

Metals are among the pollutants of highest concern in urban areas due to their persistence, bioavailability and toxicity. High concentrations of metals threaten aquatic ecosystem functioning and biodiversity, as well as human health. High-resolution estimates of pollutant sources are required to mitigate exposure to toxic compounds by identifying the specific locations and associated site characteristics where the deposition of metals is greatest. Mosses have been widely used as low-cost biological monitors of metal pollution for decades, because they readily accumulate pollutants over time, reflecting long term pollution levels. However, spectroscopic techniques to determine the concentration of metal pollutants in moss samples still require expensive instrumentation and involve time consuming sample preparation protocols with heavy use of reagents. Here we present protocols to perform in-situ and laboratory X-ray fluorescence (XRF) spectroscopy of epiphytic moss as rapid, low-cost, and accurate alternatives to conventional metal pollution biomonitoring. We also report on a preliminary validation of the measurements using mass fractions determined by inductively coupled plasma atomic emission spectroscopy (ICP-OES) as reference.•XRF measurements are taken from moss directly on tree trunks in less than five minutes.•Grinding and pelletizing of moss enables definitive quantitation (R2>0.90) of metals through portable XRF.