Preliminary risk assessment of metal contamination of urban soils in Taganrog, Russia

Long-term anthropogenic impact as a result of urbanization leads to environmental pollution by potentially toxic elements (PTEs). Soil metal contamination poses significant risks for the conjugated landscape components and for the public health. Taganrog is the second largest city in the Rostov Oblast with a population of 248,600 people, with a developed metallurgy and mechanical engineering. The aim of the study is to evaluate possible ecological and human health risks related to PTEs in urban topsoils of Taganrog.

Topsoil samples (0–20 cm deep) were collected in summer 2021. The total concentrations of Cr, Mn, Ni, Cu, Zn, Cd, and Pb were determined by X-ray fluorescence analysis using a Spectroscan MAX-GV spectrometer (Spectron, Russia). Individual environmental risks were assessed using the potential ecological risk factors (Er and MEr), integral risks were identified using the potential ecological risk indices (RI and MRI). Human health risk assessment was based on the US EPA model (1989). The noncarcinogenic risk, expressed as a hazard quotient (HQ), was evaluated by comparing the average daily dose of pollutant with a reference dose. To assess the cumulative noncarcinogenic risk, a total hazard index (HI) was used. The carcinogenic risk (CR) was calculated as lifetime average daily dose of a pollutant multiplied by the corresponding carcinogen slope factor. The total carcinogenic risk (TCR) of exposure to elements along all routes of intake was calculated as sum of CR.

The individual ecological risks of all elements were low (Er and MEr <40), with the exception of Cd. The environmental risk due to Cd pollution, assessed by Er, was moderate (55.8–70.1) in 27.3% of the samples and considerable (89.4–106.6) in 18.2% of the samples. In 36.4% of the samples was moderate Cd risk (MEr 41.6–71.1). According to RI, moderate risk was detected only in 9.1% of samples; the rest of the samples are characterized by a low risk. Values of RI ranged from 20.6 to 197.1 with a mean of 84.0. The integral environmental risk, assessed by MRI, was low in all studied samples and ranged from 13.7 to 131.4.

Noncarcinogenic risks were more likely caused by intake of As and Pb (HQ>1). For both children and adults, the risk associated with the oral intake of pollutants was the greatest. The HI values for children varied from 0.9 to 5.6, on average 2.3, for adults - from 0.1 to 0.7, on average 0.3. Most of the territory was characterized by a medium non-carcinogenic risk for children (90.9% of samples) and a low risk for adults (100%). Significant CR (>1 × 10−6) was associated with long-term exposure to As and Pb. The TCR values under the combined effect of PTEs ranged from 2.1 × 10-5 to 1.5 × 10-4, on average 5.5 × 10-5. In general, the level of carcinogenic risk in the city was assessed as moderate in 81.8% of samples and as unacceptable in 18.2% of samples.

This work was funded by the Council for Grants of the President of the Russian Federation, grant no. MK-4654.2022.1.5.