Distribution and potential provenance of metal nanoparticles in sediment core from Daya Bay, northeastern South China Sea

The widespread use of metal nanoparticles (MNPs) and their adverse effects on aquatic ecosystems have raised significant concerns. However, a comprehensive understanding of factors influencing the environmental occurrence and distribution of MNPs in anthropogenically impacted bay environments remains limited. Hence, we examined the concentration, distribution, and sources of Ag-based NPs, Zn-based NPs, Ce-based NPs, and Ti-based NPs in sediment cores from Daya Bay. The results showed that the order of the average particle concentrations of four types of MNPs in the sediments was Ti-based NPs (5.18–10.9 ×10 9 particles/g) > Ce-based NPs (2.72–9.82 ×10 9 particles/g) > Zn-based NPs (7.37–82.7 ×10 7 particles/g) > Ag-based NPs (3.11–26.0 ×10 7 particles/g). Their concentrations decreased from the inner to the outer bay (linked to terrigenous emissions) and increased from deeper to surface sediments. Sediment depth and organic matter (OM) were core environmental factors governing vertical distribution of MNPs. From the 1900s to the 1980s, the average concentrations of the four types of MNPs were approximately 44–83% of the overall average in the sediment cores, indicating limited anthropogenic influence. Since the 1980s, MNP pollution has intensified, likely stemming from multiple potential influencing factors, including anthropogenic activities (such as industrial/domestic sewage, daily products, fuel combustion) and natural sources. This study has provided solid evidence on the critical but overlooked factors that have shaped the occurrence and distribution of MNPs, providing new insights for sources and accumulation processes of MNPs in typical coastal bays.