Origin and fate of nanoparticles in marine water - Preliminary results

Our plain-English summary of Origin and fate of nanoparticles in marine water - Preliminary results, by B. Graca, A. Zgrundo, D. Zakrzewska, et al (Chemosphere, 2018).

The study

• Authors: B. Graca, A. Zgrundo, D. Zakrzewska, M. Rzodkiewicz, J. Karczewski
• Journal: Chemosphere
• Published: 2018;206:359-368
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The number, morphology and elemental composition of nanoparticles (<100 nm) in marine water was investigated using Variable Pressure Scanning Electron Microscopy (VP-SEM) and Energy-dispersive X-ray spectroscopy (EDS). Preliminary research conducted in the Baltic Sea showed that the number of nanoparticles in seawater varied from undetectable to 380 (x102) cm-3. Wind mixing and density barriers (thermocline) had a significant impact on the abundance and distribution of nanoparticles in water. Many more nanoparticles (mainly nanofibers) were detected in periods of intensive primary production and thermal stratification of water than at the end of the growing season and during periods of strong wind mixing. Temporal and spatial variability of nanoparticles as well as air mass trajectories indicated that the analysed nanofibers were both autochthonous and allochthonous (atmospheric), while the nanospheres were mainly autochthonous. Chemical composition of most of analysed nanoparticles indicates their autochthonous, natural (biogenic/geogenic) origin. Silica nanofibers (probably the remains of flagellates), nanofibers composed of manganese and iron oxides (probably of microbial origin), and pyrite nanospheres (probable formed in anoxic sediments), were all identified in the samples. Only asbestos nanofibers, which were also detected, are probably allochthonous and anthropogenic.

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In plain English

This was an environmental sampling study, described by the authors as preliminary. In June and November 2014 they collected 35 water samples in total from stations in the southern Baltic Sea off Poland and, in November, the Vistula River. They filtered the water and counted nanoparticles (particles with at least one dimension smaller than 100 nm) by scanning electron microscopy. They used X-ray spectroscopy to identify the elements in particles occurring in clusters. Counts ranged from undetectable to 380 (×10²) per cubic centimetre. Nanofibers and nanotubes ranged from not detected to 360 (×10²) per cubic centimetre in June and to 17 (×10²) in November. Many more were seen during intensive primary production and thermal stratification. Most analysed particles appeared natural in origin. The authors also identified fibers whose composition was similar to asbestos, specifically chrysotile, but gave no separate count of them. Citing high asbestos consumption in European countries including those bordering the Baltic, the authors concluded that only the asbestos nanofibers were probably of human origin. They noted that elemental analysis covered only 25 samples and that fiber counts were approximate.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: Environmental field sampling study of seawater (preliminary results), with electron microscopy and elemental analysis of nanoparticles
• Who was studied: 35 water samples in total, taken from the surface and from thermocline and/or halocline depths at stations in the southern Baltic Sea (Polish Economic Zone) in June and November 2014. The total includes samples collected from the Vistula River in November 2014.
• Exposure: Not a human exposure study. The study looked at nanoparticles in seawater, defined as particles with at least one dimension smaller than 100 nm. These included fibers with a composition similar to asbestos, specifically chrysotile.
• Main results:
  • Across all samples, nanoparticle numbers ranged from undetectable to 380 (×10²) per cubic centimetre of seawater
  • Nanotubes and nanofibers ranged from not detected to 360 (×10²) per cubic centimetre in June, and from not detected to 17 (×10²) per cubic centimetre in November
  • Many more nanoparticles, mainly nanofibers, were detected during intensive primary production and thermal stratification than at the end of the growing season and during strong wind mixing
  • In November, nanospheres were found only in surface water of the Gdansk Deep (station P1)
  • Most analysed particles had a chemical composition indicating natural (biogenic and geogenic) origin. These were silica fibers probably from flagellates, manganese and iron oxide fibers probably of microbial origin, and pyrite nanospheres.
  • Some fibers had a composition similar to asbestos, specifically chrysotile; no separate count of these fibers was given
  • No nanoparticles were seen in laboratory blank samples used to check for contamination
• The authors' conclusion: The authors concluded that, of the particles identified, only the asbestos nanofibers were probably of human (anthropogenic) origin. They linked this to very high asbestos consumption in European countries, including those bordering the Baltic Sea.
• Limitations the authors state:
  • Elemental composition was analysed in only 25 samples, so it is not a complete overview of nanoparticle chemistry in seawater
  • Clustering of nanofibers hindered counting, so nanofiber numbers are approximate
  • Composition could be determined only for nanoparticles occurring in clusters, because of the resolution limits of the X-ray spectroscopy
  • Some nanoparticles could have been lost, or a sample contaminated, during analysis steps

Topics

Medical terms in this study, explained in our Lexicon: Scanning Electron Microscopy (SEM).

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