Soil organic matter mineralization rate and metal contamination of the main soil types in central part of Yamal region (West Siberia, Russia)

This study investigates soil organic matter (SOM) mineralization rates and ecotoxicological state of major soil types in the Yamal region of West Siberia, Russia. Soil samples were collected from three sites: Lower Ob Basin, Rai-Iz mountain massif (Polar Urals), and southern Yamal Peninsula. SOM mineralization was assessed through 90-day incubation experiments at 10 and 25 °C, determining potentially mineralizable organic carbon (PMC) and basal respiration rates. Ecotoxicological assessment included analyses of heavy metals (Sr, Pb, Zn, Co, Ni, Cr, V, As, MnO) and the calculation of the total soil pollution index (Zc). The content of PMC varied from 279.50 mg/kg to 37,254.15 mg/kg, constituting 11.59%-2.74% of total soil organic carbon at 25 °C. Maximum mineralization occurred in upper organogenic horizons of Histosols and Podzols, while mineral and cryoturbated horizons showed lower rates. Temperature dependence was evident, with higher mineralization rates at 25 °C in most samples, though some mineral horizons showed the opposite pattern. Regarding ecotoxicological state, 32 of 47 soil samples showed low (acceptable) contamination levels (Zc < 16), 13 samples demonstrated moderate (moderately hazardous) levels, and only 2 samples showed high (hazardous) contamination. Priority pollutants were lead (Pb), vanadium (V), and cobalt (Co), with spatial patterns indicating vehicle emissions as a major contamination source near transport arteries. The radial differentiation coefficient revealed distinct redistribution patterns of elements across soil profiles. Overall, the soil cover of northern Western Siberia exhibits generally low anthropogenic contamination, though moderate to high contamination levels were found in areas associated with oil and gas production facilities and roadside territories. The integrative analysis suggests that areas of high anthropogenic pressure coincide with significant carbon stocks, warranting further investigation into the interplay between pollution and carbon cycle feedbacks.