Nickel (Ni) and manganese (Mn) are well known for the production of steel and alloys and are commonly found co-occurring in Ni ores. They are metals of environmental concern and contamination in the marine environment is problematic single exposures and in combination. Several studies have documented the effects of single metal exposure on the model anemone E. pallida, but research on the effects of metal mixtures is far less common. This novel study assesses the accumulation and stress effects of Ni and Mn over a 12-d exposure period. E. pallida were exposed in two separate experiments; Ni alone and Ni in combination with Mn, to assess accumulation, along with any effect on the density of symbionts and anemone tentacle length. Anemones were transferred to ambient seawater to assess depuration and recovery over 6 d. Anemone tissue accumulated Ni at a magnitude of five times higher in a mixture of 0.5 mg Ni/L with 2.5 mg Mn/L compared to the same concentration in a single Ni exposure experiment. In both experiments, Ni and Mn preferentially accumulated in the Symbiodinium spp. compared to the anemone tissue, but Ni depuration was more rapid in the mixture than Ni alone exposure. This study reveals a significant reduction in anemone Symbiodinium spp. density after exposure to Ni and Mn mixtures, but not with Ni exposure alone. A significant dose-dependent reduction in tentacle length was observed in anemones after 12 d of the Ni exposure both with and without Mn. The estimated sublethal concentration that causes tentacle retraction in 50% of test anemones (EC50) by Ni was 0.51 (0.25–0.73) mg/L, while in combination with Mn the EC50 was 0.30 mg Ni/L (confidence limits not calculatable). The present data reveals the importance of testing metal effects in combination before establishing safe limits for marine invertebrates.

Metal oxide-modified biochar showed excellent adsorption performance in wastewater treatment. Iron nitrate and potassium permanganate were oxidative modifiers through which oxygen-containing groups and iron–manganese oxides could be introduced into biochar. In this study, iron–manganese (Fe–Mn) oxide-modified biochar (BC-FM) was synthesized using rice straw biochar, and the adsorption process, removal effect, and the mechanism of cadmium (Cd) adsorption on BC-FM in wastewater treatment were explored through batch adsorption experiments and characterization (SEM, BET, FTIR, XRD, and XPS). Adsorption kinetics showed that the maximum adsorption capacity of BC-FM for Cd(II) was 120.77 mg/g at 298 K, which was approximately 1.5–10 times the amount of adsorption capacity for Cd(II) by potassium-modified or manganese-modified biochar as mentioned in the literature. The Cd(II) adsorption of BC-FM was well fit by the pseudo-second-order adsorption and Langmuir models, and it was a spontaneous and endothermic process. Adsorption was mainly controlled via a chemical adsorption mechanism. Moreover, BC-FM could maintain a Cd removal rate of approximately 50% even when reused three times. Cd(II) capture by BC-FM was facilitated by coprecipitation, surface complexation, electrostatic attraction, and cation-π interaction. Additionally, the loaded Fe–Mn oxides also played an important role in the removal of Cd(II) by redox reaction and ion exchange in BC-FM. The results suggested that BC-FM could be used as an efficient adsorbent for treating Cd-contaminated wastewater.

We aimed to explore the effects of mixtures of lead and various metals on blood pressure (BP) and the odds of pre-hypertension (systolic blood pressure (SBP) 120–139 mmHg, and/or diastolic blood pressure (DBP) 80–89 mmHg) and hypertension (SBP/DBP ≥140/90 mmHg) among Chinese adults in a cross-sectional study. This study included 11,037 adults aged 18 years or older from the 2017–2018 China National Human Biomonitoring. Average BP and 13 metals (lead, antimony, arsenic, cadmium, mercury, thallium, chromium, cobalt, molybdenum, manganese, nickel, selenium, and tin) in blood and urine were measured and lifestyle and demographic data were collected. Weighted multiple linear regressions were used to estimate associations of metals with BP in both single and multiple metal models. Weighted quantile sum (WQS) regression was performed to assess the relationship between metal mixture levels and BP. In the single metal model, after adjusting for potential confounding factors, the blood lead levels in the highest quartile were associated with the greater odds of both pre-hypertension (odds ratio (OR): 1.56, 95% CI: 1.22–1.99) and hypertension (OR:1.75, 95% CI: 1.28–2.40) when compared with the lowest quartile. We also found that blood arsenic levels were associated with increased odds of pre-hypertension (OR:1.31, 95% CI:1.00–1.74), while urinary molybdenum levels were associated with lower odds of hypertension (OR:0.68, 95% CI:0.50–0.93). No significant associations were found for the other 10 metals. WQS regression analysis showed that metal mixture levels in blood were significantly associated with higher SBP (β = 1.56, P < 0.05) and DBP (β = 1.56, P < 0.05), with the largest contributor being lead (49.9% and 66.8%, respectively). The finding suggests that exposure to mixtures of metals as measured in blood were positively associated with BP, and that lead exposure may play a critical role in hypertension development.

Developing efficient catalysts for oxytetracycline (OTC) degradation is an ideal strategy to tackle environmental pollution, and advanced oxidation processes (AOPs) have been widely used for its degradation. However, the studies on the activation of periodate (PI) by biochar and its composites in recent years have been scarcely reported. In this study, we focused on the degradation of OTC by PI activation with manganese oxide/biochar composites (MnₓOy@BC). Experimental results showed that the OTC degradation rate of MnₓOy@BC/PI system reached almost 98%, and the TOC removal efficiency reached 75%. Various characteristic analysis proved that PI could be activated efficiently by surface functional groups and manganese-active species (Mn(II), Mn(III), and Mn(IV)) on biochar, and various reactive species such as singlet oxygen (¹O₂), hydroxyl radical (∙OH), and superoxide radical (O₂∙⁻) can be observed via radical quenching experiments. Based on this, three degradation pathways were proposed. Furthermore, MnₓOy@BC and PI were combined to degrade environmental pollutants, which achieved excellent practical benefits and had great practical application potential. We hope that it can provide new ideas for advanced oxidation processes (AOPs) applying for wastewater treatment in the future.

Phosphorus (P) cycling present in sediments associated with iron (Fe), manganese (Mn) and sulfur (S) geochemical processes may cause secondary pollution in overlying water. Understanding the mechanisms of P release from sediments should help to restore water quality. This study used the diffusive gradients in thin film (DGT) technique to investigate the seasonal variation in the lability, remobilization mechanisms, and release characteristics of sediment P in the uncontaminated Xizhi River and the severely contaminated Danshui River, South China. P accumulation in sediments contributed to higher DGT-labile P concentrations in contaminated reaches, and the highest labile P concentrations were generally observed in summer season at each site. The significant positive relationships (p < 0.05) between labile Fe and P confirmed the Fe–P coupling release mechanism in uncontaminated sediments. Stronger relationships between labile Mn and P at contaminated sites indicated that Mn oxides played an important role in P remobilization. However, sulfate reduction associated with microbial activities (crucial genera: Desulfobulbus, Desulfomicrobium and Desulforhabdus) was considered to decouple the Fe & Mn–P cycling relationship, promoting P release at contaminated sites. The effluxes of sediment P were much higher in the Danshui River (mean 0.132 mg cm⁻²·d⁻¹) than in the Xizhi River (mean 0.038 mg cm⁻²·d⁻¹). And hot season led to growth in P effluxes that was much greater in contaminated river.

In this work, we prepared nanocomposites of nickel-decorated manganese oxynitride on graphene nanosheets and demonstrated them as photocatalysts for degradation of acetylsalicylic acid (ASA). The catalyst exhibited a high degradation efficiency over ASA under visible light irradiation and an excellent structural stability after multiple uses. Compared to manganese oxide (MnO) and manganese oxynitride (MnON) nanoparticles, larger specific surface area and smaller band gap were observed for the nanocomposite accounting for the enhanced photocatalytic efficiency. Besides the compositional effect of the catalyst, we also examined the influence of various experimental parameters on the degradation of ASA such as initial concentration, catalyst dose, initial pH and additives. The best performance was obtained for the nanocomposite when the catalyst dose was 10 mg/mL and the initial pH 3. Detection of intermediates during photocatalysis showed that ASA undergoes hydroxylation, demethylation, aromatization, ring opening, and finally complete mineralization into CO₂ and H₂O by reactive species. For practical applications as a photocatalyst, cytotoxicity of the nanocomposite was also evaluated, which revealed its insignificant impact on the cell viability. These results suggest the nanocomposite of nickel-decorated manganese oxynitride on graphene nanosheets as a promising photocatalyst for the remediation of ASA-contaminated water.