Understanding the Role of Low-Dose Polystyrene Microplastic in Copper Toxicity to Rice Seed (Oryza sativa L.).

There is still much to learn with respect to the potential for microplastics (MPs) to interact with environmental toxins and biota. In the present study, we investigated the effect of MPs on the toxicity of copper (Cu) to rice seeds (Oryza sativa L.). The 7-day median effective concentration (EC50) value of MPs on rice seed germination was 864 mg/L (95% confidence interval [CI] 839 to 897 mg/L). We found that MPs slightly reduced Cu toxicity to rice seeds. The 7-day EC50 of Cu on rice seed germination increased from 7.29 mg/L (95% CI 7.10-7.52 mg/L) to 7.93 mg/L (95% CI 7.58-8.08 mg/L) in the presence of 20 mg/L MPs. We examined this toxicity reduction phenomenon by investigating the role of MPs in the process of Cu transport, Cu accumulation, and metabolic responses. Further investigation found that the MPs used in the present study hardly adsorbed Cu, but these MPs accumulated on the coats of rice seeds and significantly reduced Cu accumulation in rice seedlings. When Cu concentration was 10 mg/L, the presence of MPs reduced the accumulation of Cu in rice seedlings by 34%. We also found that, compared with only Cu present, the addition of MPs resulted in lower reactive oxygen species accumulation and higher catalase activity and glutathione levels in rice seedlings, which also contributed to Cu toxicity reduction. Collectively, the present study shows that polystyrene MPs have the potential to form associations with plant structures which can ultimately impact heavy metal bioaccessibility and therefore toxicity. Environ Toxicol Chem 2024;43:1870-1879. © 2024 SETAC.

Occurrence and ecological risk assessment of organic micropollutants in the lower reaches of the Yangtze River, China: A case study of water diversion.

Water diversion has been increasingly applied to improve water quality in many water bodies. However, little is known regarding pollution by organic micropollutants (OMPs) in water diversion projects, especially at the supplier, and this pollution may threaten the quality of transferred water. In the present study, a total of 110 OMPs belonging to seven classes were investigated in water and sediment collected from a supplier of the Yangtze River within four water diversion projects. A total of 69 and 58 target OMPs were detected in water and sediment, respectively, at total concentrations reaching 1041.78 ng/L and 5942.24 ng/g dry weight (dw). Polycyclic aromatic hydrocarbons (PAHs) and pharmaceuticals were the predominant pollutants identified. When preliminarily compared with the pollution in the receiving water, the Yangtze River generally exhibited mild OMPs pollution and good water quality parameters, implying a clean water source in the water diversion project. However, in Zongyang and Fenghuangjing, PAHs pollution was more abundant than that in the corresponding receiving water in Chaohu Lake. Ammonia nitrogen pollution in the Wangyu River was comparable to that in Taihu Lake. These findings imply that water diversion may threaten receiving waters in some cases. In addition, the risks of all detected pollutants in both water and sediment were assessed. PAHs in water, especially phenanthrene and high-molecular-weight PAHs, posed high risks to invertebrates, followed by the risks to fish and algae. Pharmaceuticals, such as antibiotics and antidepressants, may also pose risks to algae and fish at a number of locations. To the best of our knowledge, this report is the first to describe OMPs pollution in water diversion projects, and the results provide a new perspective regarding the security of water diversion projects.

The effects of dissolved organic matter and feeding on bioconcentration and oxidative stress of ethylhexyl dimethyl p-aminobenzoate (OD-PABA) to crucian carp (Carassius auratus).

Bioconcentration of UV filters in organisms is an important indicator for the assessment of environmental hazards. However, bioconcentration testing rarely accounts for the influence of natural aquatic environmental factors. In order to better assess the ecological risk of organic UV filters (OUV-Fs) in an actual water environment, this study determined the influences of dissolved organic matter (DOM) (0, 1, 10, and 20 mg/L) and feeding (0, 0.5, 1, and 2% body weight/d) on bioconcentration of ethylhexyl dimethyl p-aminobenzoate (OD-PABA) in various tissues of crucian carp (Carassius auratus). Moreover, oxidative stress in the fish liver caused by the OD-PABA was also investigated by measuring activities of superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST), and levels of glutathione (GSH) and malondialdehyde (MDA). The bioconcentration of OD-PABA in the fish tissues was significantly decreased with the presence of DOM indicating a reduction of OD-PABA bioavailability caused by DOM. The bioconcentration factors (BCFs) decreased by 28.00~50.93% in the muscle, 72.67~96.74% in the gill, 37.84~87.72% in the liver, and 10.32~79.38% in the kidney at different DOM concentrations compared to those of the non-DOM treatments. Significant changes in SOD, CAT, GST, GSH, and MDA levels were found in the DOM- and OD-PABA-alone treatments. However, there were no significant differences in the SOD, CAT, GST, and MDA levels found when co-exposure to OD-PABA and DOM. Feeding led to lower OD-PABA concentrations in the fish tissues, and the concentrations were decreased with increasing feeding ratios. BCFs in various tissues reduced by 39.75~72.52% in the muscle, 56.86~79.73% in the gill, 66.41~87.50% in the liver, and 75.88~89.10% in the kidney, respectively. In the unfed treatments, the levels of SOD and MDA were significantly higher than those of the fed ones while GST and GSH levels were remarkably inhibited indicating the enhanced effect of starvation to oxidative stress. There was no markedly alternation of the biomarker levels observed between different fed treatments. In conclusion, our study indicated that both DOM and feeding reduced bioconcentration of OD-PABA and alleviated oxidative stress to some extent in the crucian carp.

Biological effects of citalopram in a suspended sediment-water system on Daphnia magna.

Suspended sediment (SPS) plays an important role in the aquatic ecosystems. Selective serotonin uptake inhibitors (SSRIs) are commonly used antidepressants and are frequently detected in aquatic environments. However, the biological effects of SSRIs in the presence of SPS are not well understood. To fill this gap, an SPS-water system was constructed to investigate the effects of citalopram (CIT) on Daphnia magna in the presence of SPS with different concentrations (0.1, 0.5, 1 g l-1) and organic carbon contents (0.5, 1, 1.5, 2%). A dialysis bag was applied in the exposure system to control the same dissolved concentration of CIT and prevent SPS from entering into the bag. The dissolved CIT concentration obviously decreased in the SPS-water system during the exposure period. The presence of SPS significantly increased the immobilization of D. magna, and the immobilization rates were positively correlated with the SPS concentration and negatively correlated with the organic carbon content in SPS. For a single exposure, CIT significantly increased superoxide dismutase (SOD) activity and inhibited acetylcholinesterase (AChE) activity in D. magna, while SPS itself did not change the SOD and AChE activities. In the SPS-water system, SOD activity was significantly suppressed, indicating that the SPS-CIT combination could result in oxidative damage. However, SPS did not enhance the neurotoxicity of D. magna that was induced by CIT. These results suggest that SPS exerts a vital role on the biological effects of CIT and the contaminants sorbed on SPS should be taken into consideration.

Influence of multi-walled carbon nanotubes on the effects of roxithromycin in crucian carp (Carassius auratus) in the presence of natural organic matter.

Carbon nanotubes are increasingly entering the aquatic environment and may interact with other co-existing contaminants, such as antibiotics. However, whether these interactions may affect their bioavailability in aquatic organisms is the subject of considerable debate. The primary objective of this study was to assess the risks arising from the coexistence of roxithromycin (ROX) and multi-walled carbon nanotubes (MWCNTs) in waters containing natural organic matter (NOM), focusing on the distribution and bioaccumulation of ROX in crucian carp (Carassius auratus), and the related biochemical status. There were no significant differences in ROX bioaccumulation in fish following exposure to ROX with and without NOM. However, the further addition of MWCNTs significantly facilitated the bioaccumulation of ROX in the liver (32-80%), gill (15-74%), intestine (51-113%), and bile (15-67%) in different exposure periods. Meanwhile, a 0.3-fold increase in the metabolic enzyme activity and oxidative stress in the liver were markedly accelerated by the co-exposed MWCNTs compared to ROX alone. The findings imply that the ROX adsorbed on MWCNTs may be a higher threat to fish than ROX alone. The high and fast release of ROX from MWCNTs in bile salts and serum albumin may contribute to the enhancement in bioaccumulation and bioactivity of ROX in fish with MWCNTs.

Bioconcentration and multi-biomarkers of organic UV filters (BM-DBM and OD-PABA) in crucian carp.

Organic UV filters (OUV-Fs) are increasingly used in sunscreens and personal care products. In the present work, the bioconcentration and multi-biomarker effects of butyl methoxydibenzoylmethane (BM-DBM) and ethylhexyl dimethyl p-aminobenzoate (OD-PABA) were investigated in crucian carp (Carassius auratus). The fish were exposed to various concentrations of BM-DBM (3.88, 35.61, 181.85 and 337.15µg/L), OD-PABA (4.66, 53.83, 264.22 and 459.32µg/L) and their mixture (2.31+2.79, 23.69+26.18, 97.37+134.81 and 193.93+246.08µg/L) for 28 days. The maximal concentrations of two OUV-Fs were detected in the fish liver, followed by the brain, kidney, gill and muscle in most cases. The maximal BCF values of OD-PABA calculated in various exposure concentrations were 0.37 - 101.21 in single exposure groups and 0.11 - 31.09 in mixed exposure groups. Acetylcholinesterase (AChE) activity was significantly inhibited by BM-DBM as well as the mixtures at all of the exposure concentrations and by OD-PABA at higher concentrations (≥264.22µg/L) during 28 days of exposure. The maximal inhibition rates of AChE activity reached 64.04% for BM-DBM, 41.05% for OD-PABA and 61.50% for the mixtures at the highest concentration, which indicated that these two OUV-Fs might damage the central nervous system. Concerning oxidative stress status, BM-DBM and the mixtures significantly increased superoxide dismutase (SOD) and glutathione reductase (GR) activities and inhibited catalase (CAT) activity, while OD-PABA caused a significant increase of GR and CAT activities. AChE and GR activities seemed to be more sensitive biomarkers for BM-DBM and OD-PABA.

Organic UV Filters in the Surface Water of Nanjing, China: Occurrence, Distribution and Ecological Risk Assessment.

Organic UV filters (OUV-Fs) are increasingly used for protection against UV irradiation. The widespread occurrence of OUV-Fs residues in aquatic systems has been reported, but little is known regarding their distribution and potential impact to the surface water in China. This study reports the occurrence, distribution and risk assessment of eight widely used OUV-Fs in the surface water of Nanjing. The results indicated butyl-methoxydibenzoylmethane, octyl-dimethyl-PABA and benzophenone-types (BP3, BP4 and BP1) were the most frequently detected compounds at concentrations of 3.63-104 ng/L. In general, the concentrations of OUV-Fs were decreased along the rivers; however, due to a substantial pollution load from the tributaries, higher concentrations of OUV-Fs were observed near the tributary inlet, compared to the other study areas. The risk assessment based on the calculated risk quotients (RQs) demonstrated that all OUV-Fs posed at least low risks to certain sensitive aquatic organisms, and BP3 posed high risk with RQ values of 1.64. It should be noted that the exclusion of adsorbed OUV-Fs might have contributed to an underestimation of the risk, therefore, it's necessary to assess both adsorbed and dissolved OUV-Fs in further studies.

Occurrence, bioaccumulation, and trophic magnification of pharmaceutically active compounds in Taihu Lake, China.

The occurrence, bioaccumulation, and trophic magnification of pharmaceutically active compounds, (PhACs) including antibiotics (roxithromycin and erythromycin), non-steroidal anti-inflammatory drugs (ibuprofen and diclofenac), a non-selective ß-adrenoceptor blocker (propranolol), an antiepileptic drug (carbamazepine), and steroid estrogens (17ß-estradiol and 17α-ethynylestradiol), were investigated in Taihu Lake, China. All eight PhACs were widely detected in surface water and sediment samples with maximal concentrations in the range of 8.74-118 ng L(-1) and 0.78-42.5 ng g(-1) dry weight (dw), respectively. The investigated organisms in the natural freshwater food web in Taihu Lake included phytoplankton, zooplankton, zoobenthos, and fish, and the maximal concentrations of target compounds in these biota samples ranged from 0.65 to 132 ng g(-1) dw. Bioaccumulation factors (BAFs) for all target PhACs were lower than 1000 L kg(-1), suggesting their low bioaccumulation potential in aquatic organisms from Taihu Lake. Trophic magnification factors (TMFs) were estimated at 1.11 for roxithromycin, 0.31 for propranolol, and 1.06 for diclofenac, indicating none of these PhACs underwent trophic magnification in this freshwater food web.

Behavioral and biochemical responses in freshwater fish Carassius auratus exposed to sertraline.

Sertraline is one of the most commonly prescribed selective serotonin reuptake inhibitors and is frequently detected in the aquatic environment. However, knowledge regarding relationships among molecular or biochemical endpoints involved in modes of action (MOAs) of sertraline and ecologically important behavioral responses of fish is insufficient. The present study aimed to investigate the bioconcentration and possible adverse outcomes pathways (AOPs) in crucian carp (Carassius auratus) exposed to various concentrations of sertraline (4.36, 21.3 and 116 µg L(-1)) for 7 d. Bioconcentration factor values were in the range of 19.5-626 in liver, 6.94-285 in brain, 4.01-146 in gill and 0.625-43.1 in muscle during the entire period of exposure. Liver superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) activities and brain acetylcholinesterase (AChE) activity were selected as biochemical endpoints associated with MOAs. Swimming activity, shoaling, feeding rate and food consumption were determined to assess behavioral responses. Fish plasma levels of sertraline exceeding human therapeutic doses were also predicted from external exposure concentrations. Significant enhancements in CAT, GPx, AChE and swimming activities and decreases in shoaling tendency, feeding rate and food consumption were observed when fish plasma levels exceeded human therapeutic thresholds. Shoaling, feeding rate and food consumption were correlated with the activities of SOD, CAT and GST. A significant positive correlation between swimming activity and AChE activity was also observed. As such, our study provides important AOPs linking biochemical responses with ultimate ecologically relevant behavioral endpoints.