Abstract: The rapid expansion and spread of Spartina alterniflora, a major invasive species in the estuarine wetlands of the Yellow River Delta, greatly affect the distribution pattern of heavy metal elements in the surface sediments of the estuarine wetlands. In this study, we collected surface sediments and measured the contents of Ca, Fe, Mg, Mn, Zn, Ni, Pb, Cr, Cd, Cu, and Li in Spartina alterniflora  wetlands with different invasion history (3, 5, 7, 10, 15 and 20 years), as well as in Phragmites australis wetland, Suaeda salsa wetland, Tamarix chinensis wetland, and bare land wetland. The enrichment coefficient and the geoaccumulation index were used to evaluate pollution level and analyze the influence of S. alterniflora invasion on nutrient distribution. The results showed that: (1) As the progress of S. alterniflora invasion, the organic carbon (SOC) and total nitrogen (TN) contents of the surface sediments of S. alterniflora wetlands were greater than those of native vegetation-covered wetlands. The contents of heavy metals in wetland sediments of native vegetations were higher than those in sediments of S. alterniflora invaded wetlands. (2) Ca was in moderate enrichment, while Cd pollution might be moderate in the region. (3) There were significant correlations among heavy metal elements. Fe and Mn contents were closely correlated with Mg, Zn, and Cu contents. Changes of contents of most elements in the S. alterniflora wetlands were mainly influenced by lithospheric bedrock weathering and sediment transport deposition.

Key words: Spartina alterniflora, heavy metal, pollution, biogeochemical cycle.