Identification and distribution of microplastics in the sediments and surface waters of Anzali Wetland in the Southwest Caspian Sea, Northern Iran.

The occurrence, abundance and distribution of microplastics (MPs) were studied in sediments and surface waters of the Anzali coastal wetland, southwest of the Caspian Sea. Sediment and surface water samples were taken at 11 and 6 stations in June 2018 and January 2019 respectively. The abundances of MPs in sediment samples were 140-2820 and 113-3690 items/kg dry weight while in surface waters were 0.40-4.41 and 0.19-2.85 items/m3 in June and January respectively. Fiber was the most common shape, followed by fragment and film. Red, black and blue were the most frequent colors. Particles 1-2 mm were the dominant size. SEM/EDS and ATR-FTIR analyses were used to identify MPs. Polypropylene, polyethylene and polyester were the most frequently found polymers. Our results highlighted the widespread dispersion of MPs in Anzali Wetland which in turn might be a pathway of MPs pollution transporter to the adjacent and connected Caspian Sea.

Distribution and Characterization of Microplastics in Surface Waters and the Southern Caspian Sea Coasts Sediments.

The Caspian Sea is the largest enclosed aquatic ecosystem in the world. The combinations of the toxic pollutants with microplastics endanger the Caspian Sea ecosystem. In this work, the distribution of microplastics was studied in surface waters and southern Caspian Sea coasts sediments. The samples were collected from eight stations, including the Tonakabon, Chalos, Nowshahr, Noor, Mahmood Abad, Babolsar, Sari, and Neka coasts. The average concentrations of microplastics in the coastal waters and sediments were 34,490 particles per km2 and 210 particles per kg, respectively. Isolated microplastics were characterized using ATR-FTIR and energy dispersive X-ray (EDS) techniques. The samples exhibited a strong carbon peak in the EDS spectra, which was screened as microplastic particles. The microplastics were mainly fragments and foams and identified as polyethylene, polypropylene, and polystyrene by means of ATR-FTIR spectra. This is the first study to determine the distribution of microplastics in southern Caspian coastal regions.

Arsenolipids in oil from blue whiting Micromesistius poutassou--evidence for arsenic-containing esters.

Arsenic-containing lipids in the oil from the blue whiting fish (Micromesistius poutassou) were separated into three broad polarity groups and investigated by HPLC and mass spectrometry. A total of 11 arsenolipids including 4 new compounds were identified. The polar lipid fraction constituting 24% of the total arsenolipid content (which totalled 2.16 µg As/g) contained four known dimethylarsinoyl fatty acids and three known dimethylarsinoyl hydrocarbons. The less polar fraction (ca 30% of the total arsenolipids) contained four new dimethylarsinoyl hydrocarbons with chain lengths 22-30 carbons, in addition to more complex arsenicals that hydrolysed to known dimethylarsinoyl fatty acids suggesting they were conjugated carboxylic acids, presumably esters. The rest of the lipid-soluble arsenic (ca 45% of the total) remained in the non-polar fraction together with the bulk of the fish oil lipids, a complex mixture of compounds that precluded identification of the small amounts of arsenolipids.

In vitro intestinal bioavailability of arsenosugar metabolites and presystemic metabolism of thio-dimethylarsinic acid in Caco-2 cells.

Whereas inorganic arsenic is classified as a human carcinogen, risks to human health related to the presence of arsenosugars in marine food are still unclear. Since studies indicate that human inorganic arsenic metabolites contribute to inorganic arsenic induced carcinogenicity, a risk assessment for arsenosugars should also include a toxicological characterization of their respective metabolites. Here we assessed intestinal bioavailability of the human arsenosugar metabolites oxo-DMAA(V), thio-DMAA(V), oxo-DMAE(V), thio-DMAE(V) and thio-DMA(V) in relation to arsenite in the Caco-2 intestinal barrier model. Whereas arsenite and thio-DMA(V) caused barrier disruption at concentrations ≥10 µM, all other metabolites did not cause a barrier leakage, even when applied at 50 times higher concentrations than arsenite and thio-DMA(V). The transfer studies point to a strong intestinal bioavailability of thio-DMA(V) and thio-DMAE(V), whereas oxo-DMAA(V), thio-DMAA(V) and oxo-DMAE(V) passed the in vitro intestinal barrier only to a very small extent. Detailed influx and efflux studies indicate that arsenite and thio-DMA(V) cross the intestinal barrier most likely by passive diffusion (paracellular) and facilitated (transcellular) transport. LC-ICP-QMS based arsenic speciation studies during the transfer experiments demonstrate transfer of thio-DMA(V) itself across the intestinal barrier and suggest metabolism of thio-DMA(V) using the in vitro intestinal barrier model to its oxygen-analogue DMA(V). In the case of arsenite no metabolism was observed. In summary the two arsenosugar metabolites thio-DMA(V) and thio-DMAE(V) showed intestinal bioavailability similar to that of arsenite, and about 10-fold higher than that reported for arsenosugars (Leffers et al., Mol. Nutr. Food Res., 2013, DOI: 10.1002/mnfr.201200821) in the same in vitro model. Thus, a presystemic metabolism of arsenosugars might strongly impact arsenic intestinal bioavailability after arsenosugar intake and should therefore be considered when assessing the risks to human health related to the consumption of arsenosugar-containing food.

Arsenic-containing hydrocarbons: natural compounds in oil from the fish capelin, Mallotus villosus.

Arsenic-containing hydrocarbons have been identified for the first time as natural components of fish oil.