A novel AgNPs spongy trap coupled with portable XRF: a field-ready strategy for sensitive mercury analysis in soils

Rapid and sensitive on-site detection of mercury in soil is crucial for environmental monitoring, however, current methods generally involve lengthy and complex sample digestion procedures thereby hindering true field deployment. While portable energy-dispersive X-ray fluorescence spectrometry (ED-XRF) offers field compatibility, which is often limited by insufficient sensitivity and spectral interference. Consequently, an effective pre-concentration method to enhance sensitivity and accuracy for rapid soil Hg analysis remains a significant challenge.

A rapid field method for soil mercury analysis was developed by coupling a portable ED-XRF with a novel silver nanoparticle sponge trap. The trap was fabricated by functionalizing a melamine sponge with polyethyleneimine and dopamine, followed by in situ reduction of silver nitrate to form a three-dimensional porous structure capable of efficiently capturing gaseous Hg⁰ through amalgamation. A major advantage is the clear separation between the characteristic XRF peaks of Ag and Hg, which minimizes spectral interference and ensures accurate quantification. The method achieved a detection limit of 12 ng/g, excellent linearity (r > 0.995), and recoveries of 86-111%. Without any digestion, the entire analysis can be completed within 10 min, demonstrating strong potential for fast on-site application.

This work introduces a digestion-free, field-deployable strategy that overcomes the sensitivity and interference constraints of portable XRF in Hg detection. By integrating a tailored nanomaterial trap, it establishes a rapid and efficient framework for on-site environmental Hg monitoring.