Four decades of actinide (U, Th, Pu, Am) analysis in environmental samples (1986–2026): evolution of measurement, detection and quantification, with a multivariate bibliometric assessment

Uranium, thorium, plutonium and americium are determined in soil, sediment, water and air for radiation protection and source attribution, but the change in measurement techniques since Chernobyl has not been quantified. This review combines a critical synthesis of method papers with a bibliometric data set of 32,181 OpenAlex records (1986–2026; 3254 naming a technique), analysed by trend tests, correspondence analysis, principal component analysis and Ward clustering and cross-checked in IAEA INIS, to test three hypotheses. H1, that mass spectrometry has replaced decay counting, was only partly supported: the share of analytical records naming inductively coupled plasma mass spectrometry (ICP-MS) rose from 19% in 1990–99 to 41% in 2016–25 (Mann–Kendall τ = +0.43, p < 0.001) and thermal ionisation mass spectrometry, neutron activation and fission track declined, but alpha spectrometry fell only from 21% to 15%, gamma spectrometry stayed near 29%, and the two families have shared mentions roughly equally since 2011. H2, that technique use is organised by the analytical problem, was supported: the only bootstrap-stable cluster grouped alpha spectrometry with sector-field ICP-MS and accelerator mass spectrometry (AMS) as a transuranic ultra-trace group, and correspondence analysis separated transuranic from natural-series methods (47.9% of inertia). H3, that the transition is not an artefact of one index, was supported (Spearman ρ = 0.83 between OpenAlex and INIS). Detection limits for 239 Pu range from 10 fg (alpha spectrometry) to 0.2 fg (AMS). Priorities are comparable detection-limit reporting, wider access to AMS and ICP-MS/MS, and monitoring of 241 Am ingrowth until the mid-2030s.