Abstract:Recently, the rapid development of the Chinese coastal economy and the expansion of aquaculture have led to an increased reliance on plastic materials within marine aquaculture systems. These materials, such as impermeable membranes, fishing nets, buoys, cages, and ropes, are extensively used for their beneficial properties. They are lightweight, durable, and cost-effective. However, the large-scale production and extensive use of plastics in aquaculture have increased concerns about their potential environmental impacts, particularly regarding the pollution of the marine environment and the associated risks to ecosystems. The primary concern is the plastic additives that are incorporated into these materials. These additives, including organophosphate esters (OPEs), are often physically mixed into the polymer matrices rather than chemically bonded. This physical integration increases their susceptibility to release into the surrounding environment through various processes, such as volatilization, leaching, abrasion, and dissolution, during the product’s lifecycle. Despite these risks, the mechanisms and patterns of additive release, as well as the exposure risks presented to marine organisms, remain poorly understood. This study focused explicitly on OPEs, a common group of plastic additives, to investigate their presence and behavior in plastic impermeable membranes used in marine aquaculture ponds. The study aimed to (1) identify the types and concentrations of OPEs present in the plastic impermeable membranes collected from marine aquaculture ponds, (2) simulate the dynamic dissolution of these OPEs in artificial seawater, and (3) evaluate the bioaccumulation potential of these OPEs in aquatic organisms, using Artemia as a model species. We collected plastic impermeable membranes from wild marine aquaculture ponds and analyzed their OPE content using high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). Our analysis revealed the presence of seven different types of OPEs, which included three aliphatic OPEs (TnBP and TiBP), one aromatic OPE (TCP), and three chlorinated OPEs (TCEP, TDCPP, and TCPP). TCPP was the most abundant, with a concentration of (395.15±48.05) ng/g, accounting for 63.12% of the total OPEs detected in the membranes. TnBP followed, exhibiting concentration of (52.96±5.25) ng/g. In contrast, TCP had the lowest concentration, contributing only 0.33% to the total OPEs. To understand the dissolution behavior of OPEs in these membranes, we conducted a 240-h laboratory simulation. The impermeable membranes were submerged in artificial seawater with a salinity of 30, and water samples were collected every 48 h for analysis. The OPE concentrations in these water samples were determined using solid-phase extraction (SPE) followed by HPLC-MS/MS. At the end of the experiment, the total amount of OPEs dissolved from the membranes reached 12.24 ng/g. Chlorinated OPEs exhibited the highest dissolution rates, with TCEP showing a dissolution rate of 40.6%. The general dissolution order was chlorinated OPEs > aromatic OPEs > aliphatic OPEs. Notably, the dissolution rate was highest during the first 48 h of the experiment and then gradually decreased over time. By approximately day 6, the dissolution rate reached a near-equilibrium state, likely due to the depletion of OPEs from cracks and pores on the membrane surface. At this stage, the membranes had likely reached a dynamic equilibrium between the release and adsorption of OPEs. In addition to the dissolution experiments, we assessed the bioaccumulation potential of OPEs in Artemia, a species commonly used in marine studies. Plastic impermeable membranes were added to artificial seawater at concentrations that mimicked those typically found in marine aquaculture ponds. After exposure, Artemia and the surrounding water samples were collected, and the OPE concentrations were analyzed using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). Five OPEs—TCP, TDCPP, TnBP, TCPP, and TiBP—were detected in Artemia. We evaluated the degree of bioaccumulation using the bioaccumulation factor (BAF). The results indicated that TCP and TDCPP had significant bioaccumulation potential, with logBAF values greater than 3.7. TnBP exhibited a moderate bioaccumulation effect, with a logBAF between 3.3 and 3.7. However, TCPP and TiBP showed no significant bioaccumulation potential, as their logBAF values were below 3.3. In conclusion, our study identified six distinct OPEs in the plastic impermeable membranes used in marine aquaculture, with chlorinated OPEs being the most prevalent. The results of the dissolution experiments revealed that OPEs are initially released rapidly from surface cracks and pores of the membranes, followed by a slower release as equilibrium is reached. Furthermore, the bioaccumulation experiments demonstrated that certain OPEs, particularly TCP and TDCPP, present bioaccumulation risks to marine organisms such as Artemia. These findings underscore the importance of managing plastic additives in marine aquaculture systems to mitigate the potential environmental impacts of plastic waste and its associated contaminants. The study provides valuable insights that can inform future strategies for reducing the ecological risks of plastic additives in marine environments.
