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Marine and intertidal heavy metal pollution has been a major concern in recent years. Tachypleus tridentatus has existed on earth for more than 430 million years. It has suffered a sharp decline in population numbers caused by environmental pollution and anthropogenic disturbance for almost 40 years. However, the effects of heavy metal pollution on juvenile T. tridentatus have not been reported. Here we show the mechanism of cadmium (Cd) detoxification in juvenile T. tridentatus using integrated antioxidant indexes and transcriptomic and metabolomic analysis. High Cd2+ concentration caused oxidative stress in juvenile T. tridentatus. The hazards increase with increasing Cd2+ concentration in juvenile T. tridentatus. Transcriptomics and metabolomics analyses concluded that high Cd2+ concentration resulted in the imbalance of glycerophospholipid metabolism in juvenile T. tridentatus to detoxify Cd. Our results offer a rationale for protective measures and further studies of heavy metal stress in T. tridentatus. [Display omitted] • ARP5 was the best reference gene of juvenile T. tridentatus for qRT-PCR when challenged with heavy metal. • Juvenile T. tridentatus regulate detoxification and immune system to alleviate effect of heavy metal. • A novel cadmium detoxification pathway in Tri-spine horseshoe crab (Tachypleus tridentatus). [ABSTRACT FROM AUTHOR]

Rare earth elements (REEs) are increasingly used in the high-tech sectors in the world and are therefore called burgeoning contaminants. As diffusive gradients in thin films (DGT) can be used to assess the bioavailability of inorganic matters, in this paper, we evaluated, for the first time, the ecotoxicology risks of REEs and their mixtures in river sediments of China's old industrial base by DGT. During our research, taking the Songhua River system (SRS) as an example, we detected its surficial sediments, of which the DGT-labile concentration of REEs (∑REEs) was 2.07–8.76 μg/L. As for the single toxicity, the risk quotient (RQ) values of Y at all sites were significantly greater than 1; while the values of Nd and Pr in some upstream reaches were all significantly greater than the threshold (1), indicating that these adverse effects of single REEs were not neglected. In terms of the combined toxicity of REEs mixtures, we carried out an assessment of the risks of probabilistic ecotoxicology, which showed that the SRS superficial sediments had a low probability of toxicity to aquatic organisms (0.54%). • Rare earth elements (REEs) in sediments were assessed based on DGT. • Combined toxicity of REEs in sediments of an old industrial base were firstly studied. • Potential toxicities of individual REEs and mixtures have emerged. [ABSTRACT FROM AUTHOR]

Centralized vs. decentralized sewage treatment is one of the key issues in the planning of rural sewage treatment (RST) in China due to the country's diverse regional characteristics. There are very limited comprehensive evaluation models for selecting regionally suitable schemes and facilities, particularly for national or provisional scale planning. As a scenario-based multi-attribute decision-making (MADM) issue, this paper develops a novel RST suitability evaluation model by integrating the multi-attribute analytic hierarchy process (AHP) with the technique for order preference by similarity to an ideal solution (TOPSIS). The suitability evaluation model sets up 3 small-centralized and 4 decentralized RST facilities as candidates and includes 12 evaluation indicators that cover economic cost, life cycle environmental impacts, technical features and operations management. Eight generic scenarios are classified for Chinese rural areas based on differences in three major characteristic factors, i.e., population density (PD), the economic development level (EDL), and topographic slope (TS). The universal evaluation results show that a centralized sewage treatment scheme is more suitable for areas with a high PD/high EDL/low TS, while a decentralized scheme is more suitable for areas with a low PD/low EDL/high TS. Sensitivity analysis shows that in regions with a high PD/low EDL, the indicator weight of the construction investment cost in the model has a great influence on the facility suitability ranking. However, in regions with a high PD/high EDL, the ranking is the most sensitive to the indicator weights of the global warming potential and sewage treatment effect. Furthermore, as a spatial decision issue, an RST suitability map of Hunan Province in China is produced at the county level of resolution, and the map is generally consistent with our field knowledge of several counties in Hunan Province. The presented evaluation framework can be integrated into environmental decision support systems in the future to help local and central governments, water utilities, design institutes and other stakeholders scientifically plan RST projects. [Display omitted] • A new suitability evaluation framework of rural sewage treatment (RST) facilities. • Considering life-cycle environmental impacts and regional differences on a large scale. • Optimal RST facilities for each 8 types of regions in China were selected. • A suitability zoning map of optimal RST facility was produced for Hunan Province. • It can help to develop an environmental decision support system for RST planning. [ABSTRACT FROM AUTHOR]