Potential interaction mechanisms between PAHs and glomalin related-soil protein (GRSP)

Abstract

Glomalin-related soil protein (GRSP) has gained widespread attention because of its benefits to carbon sequestration, improving soil quality and fixing heavy metals. However, studies on how GRSP affects the environmental fate of organic contaminants are scarce. In this study, different types of GRSPs were isolated from forest soils and characterized to study the binding of GRSPs and PAHs under different environmental conditions. The results indicated that GRSPs contain abundant functional groups (such as –NH, –COOH, and CO) and material composition, like humic acid, proteins, and lipids. For the tested GRSPs, EE-GRSP has lower DOC, SUVA260 and SUVA280 values, as well as higher E2/E3 values, indicating that EE-GRSP has lower hydrophobicity and molecular weight. These properties can lead to strong interactions between GRSP and PAHs, especially with benzopyrene, which has a high Kow and Ksw and a large molecular size, with binding constants ranging from 16,119 to 163,697 L·kg−1. Furthermore, low pH (pH = 3) and temperature (15 °C) could increase GRSP's aggregation, enhance the GRSP binding ability with PAHs, whose binding constants were 11,595 and 5067.3 L·kg−1. Therefore, the binding between GRSP and PAHs may lead to changes in the fate of PAHs in the soil and affect the environmental risk of PAHs. The results presented here will deepen our understanding of the environmental function of GRSPs and provide a theoretical basis to further elucidate the mechanisms of GRSPs and organic pollutants.