Analyzing the soil PM10 fraction complements total-soil geochemical analysis to distinguish transport-related trace element contributions from natural lithogenic inputs in urban soils, according to an investigation of transport corridors in Ulan-Ude and Severobaikalsk.
The study compared total element concentrations in soil with concentrations measured in the soil PM10 fraction across transport-affected zones, addressing the challenge of overlapping road, railway, and lithogenic inputs that occur when whole-soil samples integrate fine particles and coarser mineral components.
Cadmium, antimony, and lead exhibited the most consistent accumulation across the evaluated transport-affected areas. In Ulan-Ude, roadside and railway zones showed comparable patterns of elemental accumulation, with several transport-associated elements concentrating preferentially within the PM10 fraction.
In Severobaikalsk, cadmium, antimony, and lead showed the clearest anthropogenic accumulation, whereas heavy rare earth elements were more strongly associated with the coarser mineral fraction of the soil.
Evaluations based on local background levels, North American Shale Composite normalization patterns, and Positive Matrix Factorization indicated that rare earth elements were predominantly of lithogenic origin, with a possible contribution from mineral material related to railway infrastructure. Four Positive Matrix Factorization models demonstrated that source profiles differed between total soil concentrations and the soil PM10 fraction, linking several rare earth elements to lithogenic components and transport-related factors to mechanical wear metal associations.
A screening-level health risk assessment indicated that non-carcinogenic risks for adults remained below the screening threshold in all samples, with mean Hazard Index values ranging from 0.163 to 0.263. Mean carcinogenic risks were characterized as moderate, reaching 3.66 × 10–5 in Severobaikalsk and ranging between 3.94 × 10–5 and 5.18 × 10–5 in Ulan-Ude.
The analytical framework addressed the challenge of resolving overlapping road-related, railway-related, and lithogenic inputs in transport-affected soils. In both Ulan-Ude and Severobaikalsk, source apportionment of trace elements is complicated when total soil concentrations integrate fine particles alongside coarser mineral components. By directly comparing total element concentrations in soil against concentrations measured in the soil PM10 fraction, the study evaluated the distribution of trace elements across different soil components. This comparative approach provided geochemical indices to distinguish transport-related contributions from natural lithogenic material in areas where road and railway influences intersect.
Elemental measurements showed that cadmium, antimony, and lead exhibited the most consistent accumulation across the transport-affected areas examined in both cities. Within Ulan-Ude, roadside zones and railway zones demonstrated comparable patterns of elemental accumulation, showing that both transport corridors experienced similar elemental enrichment. Furthermore, several transport-associated elements in Ulan-Ude were preferentially concentrated in the soil PM10 fraction rather than distributed uniformly through the soil. In contrast, observations from Severobaikalsk identified cadmium, antimony, and lead as the elements with the clearest anthropogenic accumulation, while heavy rare earth elements exhibited a different distribution pattern, showing stronger associations with the coarser mineral fraction of the soil.
To determine the sources of rare earth elements, the study evaluated their distribution relative to the local background alongside North American Shale Composite normalized patterns and Positive Matrix Factorization results. These geochemical analyses indicated that rare earth elements were predominantly of lithogenic origin in the study areas. In addition to baseline geological contributions, the observed patterns pointed to a possible contribution from mineral material associated with railway infrastructure. The findings showed that heavy rare earth elements were more strongly linked with the coarser mineral fraction in Severobaikalsk, confirming that their presence was governed primarily by mineral material rather than the factors linked to transport wear.
A central methodological result emerged from the comparison of four Positive Matrix Factorization models applied to the dataset. The modeling demonstrated that source profiles differed systematically between total soil concentrations and the soil PM10 fraction. In the PM10-based models, several rare earth elements were more strongly associated with lithogenic components. At the same time, transport-related factors in the models were characterized by metal associations consistent with mechanical wear. These modeling outcomes indicate that analyzing the soil PM10 fraction provides complementary information to total-soil geochemistry, improving the ability to differentiate transport-related inputs from natural lithogenic contributions in urban environments.
The health risk assessment evaluated potential non-carcinogenic and carcinogenic risks to adults resulting from elemental exposures across all collected samples. Non-carcinogenic risks to adults remained below the established screening threshold in every sample analyzed, with mean Hazard Index values ranging between 0.163 and 0.263 across the transport-affected areas. In terms of long-term health outcomes, mean carcinogenic risks were characterized as moderate. The estimated mean carcinogenic risk reached 3.66 × 10–5 in Severobaikalsk, whereas in Ulan-Ude the mean carcinogenic risk values ranged from 3.94 × 10–5 to 5.18 × 10–5, establishing quantitative risk levels for the investigated transport zones.
Subject of Research: Source apportionment of trace elements and rare earth elements in transport-affected urban soils
Article Title: Metal(loid) and rare earth element patterns in road- and railway-affected urban soils: comparative source apportionment using total soil concentrations and the PM10 fraction
Article References: Sycheva, D. G., Kosheleva, N. E., Dubchak, I. A., Rosenberg, I. N., & Kasimov, N. S. (2026). Metal(loid) and rare earth element patterns in road- and railway-affected urban soils: comparative source apportionment using total soil concentrations and the PM10 fraction. Environmental Geochemistry and Health, 48(17), Article 691. https://doi.org/10.1007/s10653-026-03586-x
Image Credits: AI Generated
DOI: 10.1007/s10653-026-03586-x
Keywords: soil geochemistry, PM10 fraction, source apportionment, Positive Matrix Factorization, trace elements, rare earth elements, cadmium, antimony, lead, Ulan-Ude, Severobaikalsk, health risk assessment, carcinogenic risk, hazard index, lithogenic origin, railway infrastructure, roadside soils, NASC normalization
News Source: Bethany Barker. (November 12, 2026). Soil PM10 Analysis Helps Distinguish Transport Contamination From Lithogenic Soil Elements. Scienmag.
