Urban geochemical changes and pollution with potentially harmful elements in seven Russian cities

Area of Science:

• Environmental Geochemistry
• Urban Geochemistry
• Pollution Monitoring

Background:

• Urban surface deposited sediment (USDS) accumulates pollutants, reflecting environmental conditions.
• Potentially harmful elements (PHEs) like lead (Pb), zinc (Zn), and copper (Cu) pose risks.
• Establishing initial geochemical baselines is crucial for assessing urban pollution.

Purpose of the Study:

• To analyze PHE concentrations (Pb, Zn, Cu) and iron (Fe) in USDS from seven Russian cities.
• To reconstruct initial geochemical baselines for PHEs in urban environments.
• To develop and compare new criteria for assessing urban geochemical transformation and pollution.

Main Methods:

• Analysis of potentially harmful elements (PHEs) and conservative elements (CEs) in urban surface deposited sediment (USDS).
• Reconstruction of initial geochemical baselines using linear weighted fitting of PHEs as a function of CEs.
• Application of new criteria: percentage of polluted samples, average pollutant concentration, and weighting degree index (δ).
• Comparison with common criteria: PHE concentration and geo-accumulation index.

Main Results:

• Reconstructed average initial baseline concentrations for Pb, Cu, and Zn ranged from 17-52, 25-196, and 91-413 mg kg⁻¹, respectively.
• New criteria for assessing geochemical transformation and pollution were proposed and evaluated.
• The environmental ranking of cities varied significantly based on the assessment criteria used (total pollution vs. baseline change).

Conclusions:

• The study provides a robust method for reconstructing initial geochemical baselines in urban environments.
• New criteria offer a more nuanced assessment of urban geochemical transformation and pollution.
• Environmental rankings can differ substantially depending on the chosen pollution assessment method.