Distribution characteristics and ecological risk analysis of microplastics in sediments and effluents related to offshore oil and gas activities in the Bohai Sea, China.

Oil and gas activities are sources of marine microplastics (MPs) but have received less attention globally. This study assessed the distribution characteristics and ecological risks of MPs in 31 sediment samples and effluent samples of 5 oil and gas platforms related to offshore oil and gas activities in the Bohai Sea. The results showed that the mean abundance of MPs in sediment, produced water, and domestic sewage was 205.7 ± 151.5 items/kg d.w., 18 ± 11 items/L, and 26 ± 39 items/L, respectively. The MPs in sediments and effluents were dominated by transparent, rayon, and fibers <1 mm. Oil and gas activities may influence the abundance of MPs in the sediments. The sediments in the area were at a low level of risk, but some samples exhibited indexes beyond low levels. The mass of MPs carried by the effluents from oil and gas platforms in the Bohai Sea was less than that of other sources.

Ferrate (IV) synthesis using derived persulfate during treatment of oil recovery wastewater.

Using oil recovery wastewater as the target material, the degradation of organic matter in oilfield wastewater was studied in an anodic oxidation system using Ti/Ru-Ir oxide-coated anode and 0.7mMNa2SO4 as the electrolyte. The TOC of the wastewater was 210 mg/L at the beginning of the electrolysis in the electrolysis system, and it decreased from 210 to 93.6 mg/L after 50 min of electrolysis. Under the action of this system, sulfate was oxidized to persulfate, and the apparent concentration of persulfate was 15.02 mM, oxidation and degradation of organic matter in wastewater by the action of newly generated persulfate.. Afterwards, NaOH and Fe2(SO4)3 were added to the electrolyzed wastewater, and the TOC in the wastewater was further reduced to 25.1 mg/L due to the coagulation effect of the newly generated Fe(OH)3 precipitate. The TOC removal rate of the wastewater treated by this process reached 88.0%, which meets the discharge requirements. At the same time, the derived persulfate oxidized Fe(OH)3 to generate a green substance, which was identified as Na2FeO3 by IR, UV, and XRD analyses. Na2FeO3 served as a highly effective water-purifying agent, demonstrating superior performance when compared to FeO42-. The method reported in this study not only provides a strategy for waste resource recycling but also offers the potential for mass production of ferrate (IV).