Occurrence and bioaccumulation of organophosphate esters (OPEs) and degradation products in Korean coastal environments: New approach for environmental and biological monitoring

Abstract

The marine ecosystem has been served as the last repository for diverse pollutants originating from the land, which are distributed and accumulated based on their physio-chemical properties in seawater, sediment, and various organisms comprising the marine food-web. Environmental monitoring is of great concern for assessing health risks, establishing regulations, and evaluating hazardous compounds. However, recent studies have emphasized the significance of incorporating degradation products and particularly when considering relatively readily degradable substances, such as organophosphate esters (OPEs) and phthalates. As a result, a comprehensive evaluation is required for the feasibility of these compounds as markers for environmental and biological monitoring. Therefore, in the present study, simultaneous analytical methods were developed and validated for OPEs and their degradation products to assess contamination status, spatiotemporal trends, and a potential for bioaccumulation in multiple environmental matrices from highly industrialized coastal environments of Korea. Solid phase extraction (SPE) and LC-MS/MS with positive and negative ionization modes were employed to develop and validate the preparation and analytical method for 16 parent OPEs and 17 degradation products, including 11 OP diesters and six hydroxylated degradation products, in diverse environmental matrices. For the SPE treatment, the PRiME HLB was employed with ultra-sonication extraction for sediment and biota samples. The developed methods for OPEs and their degradation products were verified based on the acceptable accuracy, precision, and sensitivity. The OPEs and their degradation products were detected in wide range of concentrations in water and sediment form Korean coastal environment, ubiquitous contamination by parent and degradative products. The concentrations of ΣOPEs were approximately twice higher than those of ΣDPs in abiotic samples (water and sediments), whereas the concentrations of ΣOPEs were approximately 2-4 lower than those of ΣDPs in biological samples. This result suggests that biotransformation is a dominant process for OPEs to be degradation products. The highest concentrations of OPEs and their degradation products were found at creeks of Shihwa Lake, streams and rivers from Ulsan/Onsan Bays surrounding by industrial complexes, harbors, and WWTP outfall. This indicates that industrial activities are the major sources of OPE contamination in the coastal environments. Declining trends of chlorinated OPEs concentrations, such as TCIPP, and changed profiles were observed in sediments due to domestic and global regulations. Calculated logarithm Koc values for OPEs and their degradation showed that hydrophobic interaction was a primary driving force for the partitioning between water and sediment. The chemical structure of OPEs significantly affected the Koc values, which varied depending on the number of carbon and chlorine atoms and structural types of degradation products. The relative concentration ratios of degradation products in multiple environmental samples were calculated to assess the degradability of OPEs and the stability of degradation products. The findings suggest that some OPEs can rapidly degrade, whereas others showed slow transformation processes in the environments. It is possibly due to the differences in decomposition ability and/or environmental persistence. OPEs and their degradation products were bioaccumulated and biomagnified through the food chain from the Korean coasts. ΣOPEs showed the highest concentrations in fish, while their degradation products showed similar concentrations between fish, bivalves, Holothuroidea, and Polychaeta. Concentrations and compositions of OPEs and degradation products were different depending on the species, implying species-specific accumulation and degradation processes. The trophic magnification factors (TMFs) for almost all the OPEs and degradation products exceeded 1, suggesting the simultaneous biomagnification and biotransformation of OPEs in the marine food-webs.