The contribution of glomalin-related soil protein to Pb and Zn sequestration in polluted soil

The distribution of lead and zinc in glomalin-related soil protein (GRSP), a widespread glycoprotein presumably produced by arbuscular mycorrhizal fungi (AMF) in soil, and in some other soil fractions (soil organic matter — [SOM], carbonates, phosphates, etc.) was studied in soils from an area near a lead smelter that differed in SOM, carbonates and heavy metal (HM) content. Total GRSP represented 5.4–21.2% of the SOM and was positively correlated with the soil Pb and Zn concentrations (r = 0.57 and 0.66, p = 0.007 and p = 0.001 for Pb and Zn, respectively). Pb and Zn were predominantly bound to carbonates and organic matter. The amount of lead bound to GRSP varied between 0.69 and 23.4 mg g− 1 DW GRSP which is 0.8–15.5% of the total soil Pb. The amount of GRSP-bound metal was positively correlated with the total concentration in the case of Pb (r = 0.90, p = 0.000) but the opposite was found for Zn (r = − 0.41, p = 0.048), indicating that GRSP predominantly binds Pb. The percentages of HM-GRSP in HM-SOM were variable and were not correlated with SOM content.