Evaluating the fate of hexabromocyclododecanes in the coastal environment: Fugacity analysis using field data

Abstract

Abundant use of plastic materials has increased the amount of microplastics (MPs) and related hazardous chemicals in the marine environment. Hexabromocyclododecanes (HBCDs), brominated flame retardants added to expanded polystyrene (EPS), have been detected in biotic and abiotic samples. In this study, the partition constants of HBCDs between plastics and seawater (K-Psw) were determined. Fugacities of HBCDs in EPS, seawater, sediment, and mussels were obtained to determine the directions of the diffusive flux. The fugacities in EPS (f(EPS)) were greater than those in seawater (f(sw)), sediment (f(sed)), and mussels (f(swmussel-EPS )and f(mussel-rock)) by three orders of magnitude, indicating that EPS plastics are a significant source of HBCDs. The f(mussel-rock) of alpha-HBCD in rock mussels was greater than f(sw) by factors of 1.7, whereas the f(mussel-rock) of gamma-HBCD was smaller than f(sw) by factors of 16, indicating the bioisomerization from gamma-to alpha-HBCD. The relatively constant concentration ratio of beta-HBCD to the total HBCDs indicated that beta-HBCD is a sufficient tracer for determining the diffusive flux. The Lei values of HBCDs were greater than f(sw) by factors of 17-28, implying a probable advective vertical flow of HBCDs from the EPS plastics, which requires further investigation.