A Review of Microplastics Risk Assessment in the Coastal Environment

Pollution from microplastics has recently become a prevalent threat to the ecosystem. Microplastics with a dimension less than or equal to 5 mm are smaller. There are many ways that microplastics can reach the atmosphere. By various mechanisms, the breakdown of macro plastics will happen. Chemical degradation, tire abrasion, is the most common forms of degradation. Microplastics (MPs) pollution in the coastal and marine ecosystem is currently a global problem. Transferring MPs from land to sea and allowing them to enter the food chain has a direct negative impact on marine life and human health. The combined toxicity effects of MicroPlastics (MPs) and other contaminants in marine environments, as well as their toxicity effects and mechanisms based on a variety of environmentally important test organisms, were also covered in this study.

Toxicity Effects of Microplastics and Nanoplastics with Cadmium on the Alga Microcystis Aeruginosa

The objective of this paper is to present a thorough analysis of the toxicity of microplastics (MPs) and nanoplastics (NPs) with the heavy metal cadmium (Cd). These components were studied separately and combined to determine how these environmental toxins affect Microcystis aeruginosa (M. aeruginosa) in fresh water. The combined toxicity of MPs or NPs and Cd to M. aeruginosa showed an aggressive and negative effect after 96 h of exposure. Due to the higher adsorption ability of NPs, the accumulation of Cd inside cells with NPs was lower than that found inside the cells with MPs. But the difference in toxicity between the MPs and NPs was not significant. Meanwhile, the more produce of the extracellular polymeric substance (EPS) in the presence of NPs, the more complex effect of EPS bonded to heavy metals, which reduce the toxic effect on the algal cells. Notably, the production of microcystin-LR (MC-LR) under different treatments has demonstrated that the presence of combined MPs/NPs with Cd can potentially raise some of the toxin risks harming the aquatic environment. Our findings highlight the great potential ecological risks of the combined Cd and MPs/NPs in the aquatic system.

Separate and Combined Effects of Chlortetracycline and Oxytetracycline on Growth and Antioxidant Enzymes in Myriophyllum Aquaticum

As two typical tetracyclines, chlortetracycline (CTC) and oxytetracycline (OTC) coexist widely in water. In the experiment, Myriophyllum aquaticum (Vell.) Verdc was exposed to the orthogonal hydroponic environment with the concentrations of CTC and OTC at 1, 10, and 50 mg/L for 7 days (7 D) and 14 days (14 D). The results showed that the plant height, relative growth rates (RGR), and photosynthetic pigment contents of M. aquaticum decreased significantly after 14 D of CTC/ OTC, which was stronger than that after 7 D, and the toxicity of CTC was stronger than OTC. The combined toxicity of the two on the RGR and total chlorophyll content was mainly synergistic or additive after 7 D. After 14 D, the interaction changed to antagonism or addition, and the response of total chlorophyll content was more obvious than that of RGR. After 7 D of combined treatments, the malondialdehyde (MDA) content decreased significantly, superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD) activities responded to different combined concentrations, respectively, and CAT was the main protective enzyme of M. aquaticum. After 14 D of combined treatments, the hydrogen peroxide (H2O2) content increased significantly, the MDA content increased first and then decreased, and POD was the main protective enzyme among the three antioxidant enzymes. Overall, this study provided the first insight into the single and combined toxicity of CTC and OTC on the growth and physiology of M. aquaticum at different time periods, revealing the reversal of the combined toxicity with time of exposure.

Study on the Joint Toxicity of Multi-component Mixtures of Quaternary Ammonium Compounds

Pollutants generally exist as mixtures in the environment. Their cumulative toxicity and toxicity interactions are potential risks. Therefore, this study aimed to examine the variation of joint toxicity of a multi-component mixture system, which consisted of six common quaternary ammonium salt surfactants in the environment, on Vibrio qinghaiensis sp.-Q67 (Q67). Vibrio qinghaiensis sp. -Q67 (Vqin-Q67) is a freshwater luminescent bacterium that continuously emits blue-green light (485 nm). The bacterium has been widely used for detecting toxic contaminants. In the mixture system, the luminescent toxicity of each component of the mixture to Q67 was determined by the microplate toxicity analysis method, and the toxicity interaction of the mixture was determined by the toxicity unit method (TU). The combined toxicity of the mixture system was investigated from four aspects, including the number of components, key components, concentration (toxicity) ratio, and exposure time. The results showed that the combined toxic effect of the same mixture system tends to be an additive effect with the increase of the number of components. The combined toxicity of the mixture system was close to that of the key components. Antagonism was presented in the equal toxicity mixture, while synergism was presented in the non-equal toxicity mixture. The combined toxic effect of the multi-component mixture system was not only related to the concentration of the pollutant but also related to the exposure time of the pollutant.

Combined Toxicity and Toxicity Persistence of Antidepressants Citalopram and Mirtazapine to Zooplankton Daphnia Magna

Citalopram (CTP) and mirtazapine (MTP) are two typical psychoactive drugs used for the depression treatment. As emerging pollutants, CTP and MTP has been given widely concern because they are active substances for organisms. Therefore, the ecotoxicological risks of aquatic organisms should be paid more attention to. In this study, the effects of CTP and MTP on the feeding behavior, heartbeat, nutritional enzymes and related gene transcriptions of Daphnia magna were investigated under single and mixed environmental stress. Meanwhile, the recovery of exposed D. magna was studied to analyze the toxic persistence of those pollutants. After 24-hexposure, the ingestion rate decreased by 34.2% and 21.5%, in the group of C-H and Mix-H respectively. After 24-h recovery, the feeding behavior of D. magna was stimulated by compensatory stimulation. In exposure period, the heartbeat rate of D. magna increased by 132.3%, 69%, 111.9%, 139.4%, and 92.4%, in the group of C-L, C-H, M-L, M-H and Mix-L respectively, and was recovered during the recovery period. The activity of α-amylase (AMS) and trypsin were significantly changed in most of the exposed daphnia, both in the exposure period and recovery period. CTP/MTP exposure stimulated transcription of the α-amylase gene. M-H and Mix-H exposure inhibited transcription of the trypsin gene and other stimulated transcriptions. After 24-h recovery, the stimulative or inhibitory effects were alleviated. There were different responses between gene transcription and enzyme activity. In conclusion, our results highlighted the toxic effects of single and mixed pollution of CTP and MTP on feeding, heartbeat, enzymes and genes of D. magna.