Natural N-bearing nanoparticles in sediments of a shallow bay of the south china: A new N form in N-cycling

Abstract

Nitrogen (N) in sediments plays a significant role in N-cycling in the estuarine and coastal ecosystems. However, there is only limited information available on the N-bearing nanoparticles in the shallow-marine sediments. Here, we have found that N can occur as the nanoparticle in surface sediments (0–5 cm) of a shallow bay (Zhenhai Bay) in the South China. These particles are usually 50 to 200 nm in size and contain C, N, O, Si, Fe, K, and Na in composition reveled by energy dispersive X-ray spectrometry (EDS). According to the scanning electron microscopy and high-resolution transmission electron microscopy images, these N-bearing nanoparticles exhibit rod-shape, sheet-like particle, fibrillar, and spheroidal in morphology. These findings indicate that nanoparticels could be a transport form for N, and many elements could also accompany nanoparticles during the transportation. The biophile elements (C, N and Fe) within the N-bearing nanoparticles and fibrillar morphology of these nanopartilcles indicate that they may be biogenesis, which is consistent with the characteristics of δ14N (4.51–4.64‰), and C/N (11.2–11.9) in sediments. Therefore, N-bearing nanoparticles maybe take part in the local biotic interaction. In addition, since nanoparticles do not settle out of seawater rapidly and some N-bearing nanoparticles have potential to form the solid phase, a part of N-bearing nanoparticles may separate N from the biological N-cycling. Therefore, N-bearing nanoparticles could affect the local biological N-cycling.

Keywords

• N-bearing nanoparticles
• Transport form of N
• N-cycling
• Shallow-marine sediment