Sixteen-year changes in hazardous metal(loid)s in urban topsoils: Land-use-specific enrichment and PM₁₀-based human health risk.
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Urban topsoils are persistent reservoirs of hazardous metal(loid)s, yet reassessments rarely integrate censoring-aware statistics, geochemical enrichment and updated exposure modelling. We reassessed 137 topsoils collected in 2001 and 94 in 2017 across Urban, Industrial and Garden land uses in Alcalá de Henares, Spain. Eleven elements were compared temporally using left-censored methods with false-discovery-rate correction; Hg was retained as a 2017 descriptive endpoint because of poor historical comparability and high censoring. Urban Pb declined by 43.3%, whereas Be, Cr, Mn, Tl and V showed FDR-robust shifts towards higher 2017 acid-recoverable concentrations; because the digestion workflows differed between campaigns, the magnitude of these increases cannot be attributed exclusively to environmental accumulation. Sn showed a significant distributional shift, while the apparent 16.4% Cd decline was not robust to conservative analytical-threshold sensitivity. Industrial soils likewise showed higher 2017 acid-recoverable concentrations of As, Cr, Mn, Tl, V and Zn. Integrated enrichment was lowest in Urban soils and highest at the four sampled Garden locations; because the 2017 Garden subset comprised only n = 4, these metrics are interpreted as site-specific screening indicators rather than municipality-wide Garden estimates. Using updated U.S. EPA toxicity parameters and the historical-comparability assumption Cr(VI) = total Cr/6, 2017 hazard indices were 1.214 for Urban children, 0.156 for Urban adults, 0.0997 for Industrial workers, 2.173 for children at the sampled Garden locations and 0.278 for Garden adults. Cancer risks ranged from 4.13 × 10⁻⁵ to 2.16 × 10⁻⁴, with As dominating both non-cancer and cancer risk. From 2001-2017, Urban-child HI increased from 0.949 to 1.214, crossing the screening benchmark of 1. Excluding inferred Cr(VI) did not change this or any other qualitative receptor-level interpretation. Alcalá topsoils therefore show divergent contaminant trajectories, with declining legacy Urban Pb coexisting with higher 2017 acid-recoverable multi-element signatures and persistent child-exposure screening priorities.