With the widespread occurrence and accumulation of plastic waste in the world, plastic pollution has become a serious threat to ecosystem and ecological security, especially to estuarine and coastal areas. Understanding the impacts of changing nanoplastics concentrations on aquatic organisms living in these areas is essential for revealing the ecological effects caused by plastic pollution. In the present study, we revealed the effects of exposure to gradient concentrations (0.005, 0.05, 0.5 and 50 mg/L) of 75 nm polystyrene nanoplastics (PS-NPs) for 48 h on metabolic processes in muscle tissue of a bivalve, the razor clam Sinonovacula constricta, via metabolomic and transcriptomic analysis. Our results showed that PS-NPs caused dose-dependent adverse effects on energy reserves, membrane lipid metabolism, purine metabolism and lysosomal hydrolases. Exposure to PS-NPs reduced energy reserves, especially lipids. Membrane lipid metabolism was sensitive to PS-NPs with contents of phosphocholines (PC), phosphatidylethanolamines (PE) and phosphatidylserines (PS) increasing and degradation being inhibited in all concentrations. High concentrations of PS-NPs altered the purine metabolism via increasing contents of guanosine triphosphate (GTP) and adenine, which may be needed for DNA repair, and consuming inosine and hypoxanthine. During exposure to low concentrations of PS-NPs, lysosomal hydrolases in S. constricta, especially cathepsins, were inhibited while this influence was improved transitorily in 5 mg/L of PS-NPs. These adverse effects together impacted energy metabolism in S. constricta and disturbed energy homeostasis, which was manifested by the low levels of acetyl-CoA in high concentrations of PS-NPs. Overall, our results revealed the effects of acute exposure to gradient concentrations of PS-NPs on S. constricta, especially its metabolic process, and provide perspectives for understanding the toxicity of dynamic plastic pollution to coastal organisms and ecosystem.

Strategies to prevent cadmium (Cd) mobilization by crops under salinity conditions differs among distinct genotypes, but the biological mechanisms of Cd accumulation in different genotype crops promoted by salinity have remained scarce. In this study, we investigated the biological mechanisms of Cd accumulation in two quite different amaranth cultivars of low-Cd accumulator Quanhong (QH) and high-Cd accumulator Liuye (LY) in response to salt stress. Transcriptomes analysis was carried out on leaves and roots tissues of LY and QH grown with exchangeable Cd 0.27 mg kg⁻¹ and salinity 3.0 g kg⁻¹ treatment or control conditions, respectively. A total of 3224 differentially expressed genes (DEGs) in LY (1119 in roots, 2105 in leaves) and 848 in QH (207 in roots, 641 in leaves) were identified. Almost in each fold change category (2-2⁵, 2⁵-2¹⁰, >2¹⁰), the numbers of DEGs induced by salinity in LY treatments were much more than those in QH treatments, indicating that LY is more salt sensitive. Gene ontology (GO) analysis revealed that salinity stress promoted soil acidification and Cd mobilization in LY treatments through the enhancive expression of genes related to adenine metabolism (84-fold enrichment) and proton pumping ATPase (50-fold enrichment) in roots, and carbohydrate hydrolysis (2.5-fold enrichment) in leaves compared with that of whole genome, respectively. The genes expression of organic acid transporter (ALMT) was promoted by 2.71- to 3.94-fold in roots, facilitating the secretion of organic acids. Salt stress also inhibited the expression of key enzymes related to cell wall biosynthesis in roots, reducing the physical barriers for Cd uptake. All these processes altered in LY were more substantially compared with that of QH, suggesting that salt sensitive cultivars might accumulate more Cd and pose a higher health risk.

This work forwards new insights into the risk-assessment of multi-walled carbon-nanotubes (MWCNTs) while analysing the role of quantum-mechanical interactions between the electrons in the adsorption of probe compounds and biomolecules by MWCNTs. For this, the quantitative models are developed using quantum-chemical descriptors and their electron-correlation contribution. The major quantum-chemical factors contributing to the adsorption are found to be mean polarizability, electron-correlation energy, and electron-correlation contribution to the absolute electronegativity and LUMO energy. The proposed models, based on only three quantum-chemical factors, are found to be even more robust and predictive than the previously known five or four factors based linear free-energy and solvation-energy relationships. The proposed models are employed to predict the adsorption of biomolecules including steroid hormones and DNA bases. The steroid hormones are predicted to be strongly adsorbed by the MWCNTs, with the order: hydrocortisone > aldosterone > progesterone > ethinyl-oestradiol > testosterone > oestradiol, whereas the DNA bases are found to be relatively less adsorbed but follow the order as: guanine > adenine > thymine > cytosine > uracil. Besides these, the developed electron-correlation based models predict several insecticides, pesticides, herbicides, fungicides, plasticizers and antimicrobial agents in cosmetics, to be strongly adsorbed by the carbon-nanotubes. The present study proposes that the instantaneous inter-electronic interactions may be quite significant in various physico-chemical processes involving MWCNTs, and can be used as a reliable predictor for their risk assessment.