Assessment of distributional characteristics and ecological risks of cyclic volatile methylsiloxanes in sediments from urban rivers in northern Vietnam.

Abstract

In this report, four cVMSs including hexamethylcyclotrisiloxane (D3), octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5), and dodecamethylcyclohexasiloxane (D6) were determined in 85 sediment samples collected from three rivers in northern Vietnam during the period from May to November 2020. Total mean concentrations of cVMSs ranged from 75.4 to 15,000ng/g-dw. The highest levels of cVMS were found in sediment samples collected from the To Lich River (range, 260-15,000ng/g-dw; median, 2840ng/g-dw), followed by the Nhue River (range, 188-6800ng/g-dw; median, 1370ng/g-dw), and the Day River (range, 75.4-4600ng/g-dw; median, 666ng/g-dw). Among cVMSs, decamethylcyclopentasiloxane (D5) was found at the highest levels in all samples and ranged from 9.00 to 11,000ng/g-dw. Significant correlations exist between the concentrations of D4/D6 and D5/D6 pairs in river sediment samples. Although the calculated ecological risk was not high, the presence of cVMSs in the sediment raises concerns about the impact on aquatic life because of their long-term accumulation capacity.