Effects of urbanization on soil heavy metal accumulation and improvement using Glomalin-related soil protein

Glomalin-related soil protein (GRSP) exhibits strong adsorption and sequestration capacities for heavy metals. However, the contribution rate of GRSP to the sequestration of soil heavy metals under rapid urbanization remains unclear. Therefore, 184 soil samples from the green spaces in a built-up area of Nanchang, China were selected as the research site according to the urbanization intensity levels and the impervious surface area rates. The GRSP, soil heavy metal (V, Ni, Cr, Cu, Pb, Co, As, Cd, and Zn), and GRSP-bound heavy metal contents were determined to analyze the adsorption potential and differences of GRSP for heavy metals. With increasing urbanization intensity, the Pb, Cd, and Cr contents decreased by 28-66%, and GRSP contents declined by 19-24% (P < 0.05). The contribution rates of GRSP-Cd, GRSP-Pb, and GRSP-Cr to Cd, Pb, and Cr sequestration were 1.98-3.35-fold higher in low urbanization areas than that in heavy urbanization areas (P < 0.05). The adsorption potential of GRSP-Cu was the highest (14.71-23.77%). The findings showed that GRSP could enhance the capability of heavy metals adsorbed by urban soil, while urbanization decreased the content and sequestration potential of GRSP-bound heavy metals, thereby contributing to the improvement of the urban soil environment.