The role of organic and inorganic substituents of roxarsone determines its binding behavior and mechanisms onto nano-ferrihydrite colloidal particles.

The retention and fate of Roxarsone (ROX) onto typical reactive soil minerals were crucial for evaluating its potential environmental risk. However, the behavior and molecular-level reaction mechanism of ROX and its substituents with iron (hydr)oxides remains unclear. Herein, the binding behavior of ROX on ferrihydrite (Fh) was investigated through batch experiments and in-situ ATR-FTIR techniques. Our results demonstrated that Fh is an effective geo-sorbent for the retention of ROX. The pseudo-second-order kinetic and the Langmuir model successfully described the sorption process. The driving force for the binding of ROX on Fh was ascribed to the chemical adsorption, and the rate-limiting step is simultaneously dominated by intraparticle and film diffusion. Isotherms results revealed that the sorption of ROX onto Fh appeared in uniformly distributed monolayer adsorption sites. The two-dimensional correlation spectroscopy and XPS results implied that the nitro, hydroxyl, and arsenate moiety of ROX molecules have participated in binding ROX onto Fh, signifying that the predominated mechanisms were attributed to the hydrogen bonding and surface complexation. Our results can help to better understand the ROX-mineral interactions at the molecular level and lay the foundation for exploring the degradation, transformation, and remediation technologies of ROX and structural analog pollutants in the environment.

Nano-ferrihydrite colloidal particles mediated interfacial interactions of arsenate and cadmium: Implications for their fate under iron-rich geological settings.

Arsenic (As) and cadmium (Cd) often coexist in paddy soils. Nano-ferrihydrite colloidal particles (NFPs) are ubiquitous at redox active interfaces of the paddy system and are well-known to play a critical role in controlling the solubility and bio-availability of As and Cd. However, the mutual interaction between As and Cd on NFPs remains elusive. Herein, batch experiments and in-situ spectroscopic techniques were used to investigate the effects of the interaction pattern (sequential reaction) of Cd(II) and As(V) on their respective adsorption on the surfaces of NFPs. Two scenarios were designed: Cd(II) pre-saturated NFPs and As(V) pre-saturated NFPs. Adsorption of Cd(II) was increased by 1.67, 4.08, and 5.21 times in As(V)-saturated NFPs, but only by 1.05, 1.11, and 1.15 times for As(V) in Cd(II)-saturated NFPs. Further, we determined the pH-dependent mutually beneficial cooperation pathways as mediated by the surface of NFPs. At lower pH (5), As(V) tended to promote Cd(II) adsorption, whereas Cd(II) tended to enhance As(V) adsorption at higher pH (> 5.5). X-ray photoelectron spectroscopy (XPS) indicated that both pre-saturated Cd(II) and As(V) altered the local coordination environment of their counterpart ions. Furthermore, results from in-situ attenuated total reflection-Fourier-transform infrared spectroscopy (ATR-FTIR) and second derivative peak shape fitting revealed two types of ternary surface complexes, namely Cd(II)-bridged and As(V)-bridged complexes, which were responsible for the distinct Cd(II) and As(V) co-adsorption behavior on the surface of NFPs under different conditions. These findings help us understand how co-presence Cd and As behave in an iron-rich geological setting and will aid in the development of related restoration technologies.

The ignored risk: heavy metal pollution of medicine and food homologous substances.

A survey was conducted to investigate the effects of cadmium (Cd), arsenic (As), chromium (Cr), lead (Pb), and copper (Cu) in medicine and food homologous substances (MFHs) on human health. Nine common and typical MFHs (Dendrobium, Bulbus lilii, Poria, Semen nelumbinis, Radix puerariae, Gardenia jasminoides, Hordeum vulgare L, Semen coicis, and Ganoderma Karst) in the form of medicinal slices ready for decoction were purchased from pharmacies. Five among the MFHs (Dendrobium, Bulbus lilii, Poria, Semen nelumbinis, and Radix puerariae) were further obtained from a local field as raw materials for comparison. The results showed that raw materials of MFHs collected from the field had higher contents of heavy metal and greater health risks than medicinal slices purchased from pharmacy. Generally, the heavy metal residues in MFHs of different medicinal parts were different, and MFHs from roots or stems had significantly higher contents of heavy metals than those from fruits or seeds. Most importantly, the contents of Cd in Bulbus lilii and As in wild Poria from field were higher than the contents described in the Pharmacopoeia of the People's Republic of China (ChP). Non-carcinogenic and carcinogenic risk assessments revealed that Poria from field had larger non-carcinogenic and carcinogenic risks to human health; Bulbus lilii showed no non-carcinogenic risk but exhibited carcinogenic risks, whereas Cr showed carcinogenic risks in all samples. Given that MFHs are incorporated in regular foods, care should be taken to minimize health hazards caused by heavy metals to human. This study creates awareness on the safety issues associated with MFHs, and provides basic information for establishing the maximum allowable contents of medicinal and food substances in normal diets.

[Effect and Mechanism of Foliar Application Nano-MnO2 on Cadmium Enrichment of Rice].

Cadmium (Cd) is easily enriched in rice, resulting in an excessive Cd content in the grain, which seriously threatens human health. Manganese (Mn) is an essential element of plants. In a field experiment on Cd-contaminated acid soils, we investigated the effectiveness and mechanism of Mn in minimizing Cd accumulation in rice via foliar spraying using 0.1%, 0.3%, and 0.5% nano-MnO2 solutions at an early stage of heading. Compared with a control treatment, foliar spraying effectively reduced the Cd content of rice leaves, husks, and brown rice; increased the Mn content of all rice organs; but had no effect on rice yield. Foliar application of nano-MnO2 alleviated the plant stress induced by Cd by improving leaf photosynthesis, inhibiting lipid peroxidation, and increasing the content of the oxidative stress protein kinase. In addition, foliar application of nano-MnO2 limited the absorption of Cd by roots by increasing the content of iron-manganese plaque on the surfaces of rice roots and strengthening its adsorption/co-precipitation of Cd. Therefore, foliar application of nano-MnO2 during the early stages of rice heading is an effective measure to increase the Mn content and reduce the Cd content of brown rice.

Calcitonin-negative neuroendocrine tumor of the thyroid with metastasis to liver-rare presentation of an unusual tumor: A case report and review of literature.

BACKGROUND: Neuroendocrine tumors mainly occur in the stomach, intestine, pancreas, and lung and are rarely detected in the thyroid. Thyroid neuroendocrine tumors, designated medullary thyroid carcinoma, generally present with elevated calcitonin. Calcitonin-negative neuroendocrine tumors of the thyroid are extremely rare. CASE SUMMARY: Here, we present a case report of a 56-year-old female patient with a neck pain complaint. Total thyroidectomy was conducted after comprehensive evaluation, and diagnosis was confirmed as calcitonin-negative neuroendocrine tumor of the thyroid. Two months later, liver metastasis was detected, and transcatheter arterial chemoembolization was subsequently performed to control growth. However, the curative effect was unsatisfactory and multiple intrahepatic metastases occurred after 3 mo. CONCLUSION: Owing to the rarity of this disease, no clear guidelines are available for treatment. In addition to reporting this rare case, we have reviewed and summarized associated medical literature with an aim to provide a comprehensive reference platform for subsequent research.

Enrichment of cadmium in rice (Oryza sativa L.) grown under different exogenous pollution sources.

In order to unravel the cadmium (Cd) enrichment patterns in rice (Oryza sativa L.) grown under different exogenous exposure pathways, the pot experiment was conducted in a greenhouse. Cd was added to the soil-rice system via mixing soil with Cd-containing solution, irrigating the pots with Cd-containing water and leaf-spraying with Cd solution to simulate soil pollution (SPS), irrigation water pollution (IPS), and atmospheric deposit pollution sources (APS), respectively. No significant (p > 0.05) differences in plant height and rice grain yield were observed among all treatments including three different Cd pollution sources and control. The contents of Cd in rice plants significantly (p < 0.05) increased with increase in Cd concentrations in three pollution sources. The distribution pattern of Cd in the rice plant organs treated with SPS and IPS followed the order: roots > stems > leaves > husk > brown rice, while it was leaves > roots > stems > husk > brown rice treated with APS. At the same level of treatment, the highest concentration of Cd was observed in rice organs (except for middle and high concentrations treatment roots) grown under APS, followed by IPS and SPS, suggesting that the Cd bioavailability from different pollution sources followed the order of APS > IPS > SPS. It is concluded that the atmospheric pollution contributed more enrichment of rice with Cd. Therefore, in field environment, air deposits should also be analyzed for toxic metals during assessment of food chain contamination and health risk.