Seasonal content of Cu, Zn, and Pb in roadside soils on Olkhon Island (2023-2025)

Original Paper

Abstract

Relevance and problem formulation. The paper examines the impact of vehicle traffic from auto‑excursions on the territory of the Baikal National Park. The aim is to assess the accumulation of Pb, Zn, and Cu in roadside soils and to identify the mechanisms of their lateral migration. Identifying the leading pollution factors is necessary for developing measures to minimize anthropogenic pressure on the boundaries of the specially protected natural territory of federal significance. Materials and Methods. Between 2023 and 2025, 168 soil samples were collected in a 10‑meter zone from roads at a depth of up to 20 cm. Concentrations of Pb, Zn, and Cu were determined using the X‑ray fluorescence method. Based on average monthly data, the Clarke coefficient (C_c) and the regional background coefficient (C_b) were calculated. The spatio‑temporal dynamics were analysed taking into account the intensity of traffic, road works, the island’s relief, and lithology. Results and discussion. A pronounced seasonal variability in the geochemical profile was identified. During the summer period, based on the Clarke coefficient (C_c), the priority pollutants are Cu (0.98-3.70) and Zn (1.56-3.39), while when analyzing them relative to the regional background (Cb), the leading element becomes Pb (1.18-2.89), which was recorded in 100% of the samples. By October, Pb concentrations decrease, whereas Zn and Cu show a slight upward trend. High levels of accumulation on sandy soils with a low natural background indicate a predominantly anthropogenic origin of pollutants. The main sources may include exhaust gases, wear products of brake linings and tires, as well as dust generation during road repair work. The lateral distribution of metals along the cross‑section of the slope is asymmetric  and may be determined by a combination of air and water flows. Zn and Cu reach a maximum at the upper point of the slope, likely due to the deposition of airborne droplet fractions by dominant winds. Conversely, Pb accumulates at the lowest point, likely as a result of gravitational and rainfall runoff. At the same time, the peak in Cu in the upper part of the slope may be due to the superposition of modern anthropogenic pollution on the residual agrochemical background from land plowing during the Soviet period. The data obtained indicate a transformation of the soil cover at the park boundaries, where the contribution of excursion vehicles is comparable to the impact of historical land use. This requires a review of the regulations governing tourist routes to protect the ecosystems of the Baikal region.