RESUMO
Rare earth elements (REEs) are integral to numerous high-tech industries, yet their biogeochemical cycling within ecosystems remains inadequately characterized. Recently, phytoliths have been identified as potentially significant sinks for REEs; however, their role in the cycling of these elements has been underestimated. In this work, we investigate the accumulation of REEs in phytoliths (PhytREEs) within the Greater Khingan Mountains region, employing an optimized wet oxidation method combined with heavy liquid flotation to quantify PhytREEs contents in surface soils. The results revealed an elevation-dependent pattern of PhytREEs concentration, with heightened levels at higher altitudes and diminishing concentrations towards the eastern plains. The enrichment coefficient of PhytREEs (ECPhytREEs) was found to be approximately 2.7 %, indicative of a moderately selective sequestration process. The multivariate analysis indicated that terrain complexity, climatic patterns, soil texture, and organic matter significantly influence the uptake and storage of REEs in plants, subsequently affecting their partitioning in phytoliths. Among these factors, the complexation of REEs with organic matter emerged as a pivotal mechanism facilitating their immobilization within phytoliths. Soil characteristics also play a non-negligible role in modulating REEs dynamics. Our findings highlight the predominant influence of climate on PhytREE storage, suggesting that climatic variables are the primary drivers modulating the bioavailability and ultimate sequestration of REEs within phytoliths. This study enhances our understanding of the biotic-abiotic interplay in the sequestration of REEs and underscores the need to incorporate phytoliths into models of terrestrial REE cycling.
RESUMO
Fulvic acid (FA) and iron oxides often play regulating roles in the geochemical behavior and ecological risk of arsenic (As) in terrestrial ecosystems. FA can act as electron shuttles to facilitate the reductive dissolution of As-bearing iron (hydr)oxides. However, the influence of FA from different sources on the sequential conversion of Fe/As in As-bearing iron oxides under biotic and abiotic conditions remains unclear. In this work, we exposed prepared As-bearing iron oxides to FAs derived from lignite (FAL) and plant peat (FAP) under anaerobic conditions, tracked the fate of Fe and As in the aqueous phase, and investigated the reduction transformation of Fe(III)/As(V) with or without the presence of Shewanella oneidensis MR-1. The results showed that the reduction efficiency of Fe(III)/As(V) was increased by MR-1, through its metabolic activity and using FAs as electron shuttles. The reduction of Fe(III)/As(V) was closely associated with goethite being more conducive to Fe/As reduction compared to hematite. It is determined that functional groups such as hydroxy, carboxy, aromatic, aldehyde, ketone and aliphatic groups are the primary electron donors. Their reductive capacities rank in the following sequence: hydroxy> carboxy, aromatic, aldehyde, ketone> aliphatic group. Notably, our findings suggest that in the biotic reduction, Fe significantly reduction precedes As reduction, thereby influencing the latter's reduction process across all incubation systems. This work provides empirical support for understanding iron's role in modulating the geochemical cycling of As and is of significant importance for assessing the release risk of arsenic in natural environments.
Assuntos
Arsênio , Benzopiranos , Compostos Férricos , Oxirredução , Shewanella , Compostos Férricos/metabolismo , Compostos Férricos/química , Arsênio/metabolismo , Shewanella/metabolismo , Ferro/química , Ferro/metabolismoRESUMO
As a vital type of light-absorbing aerosol, brown carbon (BrC) presents inherent associations with atmospheric photochemistry and climate change. However, the understanding of the chemical and optical properties of BrC is limited, especially in some resource-dependent cities with long heating periods in northwest China. This study showed that the annual average abundances of Water-soluble BrC (WS-BrC) were 9.33±7.42 and 8.69±6.29 µg/m3 in Baotou and Wuhai and the concentrations, absorption coefficient (Abs365), and mass absorption efficiency (MAE365) of WS-BrC presented significant seasonal patterns, with high values in the heating season and low values in the non-heating season; while showing opposite seasonal trends for the Absorption Ångström exponent (AAE300-400). Comparatively, the levels of WS-BrC in developing regions (such as cities in Asia) were higher than those in developed regions (such as cities in Europe and Australia), indicating the significant differences in energy consumption in these regions. By combining fluorescence excitation-emission matrix (EEM) spectra with the parallel factor (PARAFAC) model, humic-like (C1 and C2) and protein-like (C3) substances were identified, and accounted for 61.40%±4.66% and 38.6%±3.78% at Baotou, and 60.33%±6.29% and 39.67%±4.17% at Wuhai, respectively. The results of source apportionment suggested that the potential source regions of WS-BrC varied in heating vs. non-heating seasons and that the properties of WS-BrC significantly depended on primary emissions (e.g., combustion emissions) and secondary formation.
Assuntos
Poluentes Atmosféricos , Carbono , Cidades , Carbono/análise , Água/química , Monitoramento Ambiental , Aerossóis/análise , Poluentes Atmosféricos/análise , Material Particulado/análiseRESUMO
HLA-G is a class I HLA that has gained much attention due to its multiple functions in the immune system. More important, some studies found HLA-G may be detrimental in tumors and viral infections, and the detection of HLA-G expression might serve as a clinical marker in the prediction of clinical outcomes for certain types of carcinoma. We assessed the association between the development of Kazakh esophageal squamous cell carcinoma (ESCC) harboring high-risk HPV infection and the expression of HLA-G. The expression of HLA-G was detected by S-P immunohistochemical staining in 60 cases of Kazakh ESCC tissues and 40 cases of Kazakh tumor adjacent normal tissues. HPV16 infection in ESCC was detected by genotype-specific polymerase chain reaction. HPV16 infection rate in Kazakh ESCC was 35.0%, significantly higher than that of the infection rate of the adjacent normal tissues 15% (p<0.05, OR=3.051; 95% CI: 1.103-8.438). The expression of HLA-G in Kazakh ESCC was 75.0% (45/60), significantly higher than that of tumor adjacent normal tissues (17.5%; p<0.05); expression of HLA-G was slightly higher in HPV16-positive than HPV16-negative ESCC, but the difference was not statistically significant (p>0.05). The positive expression rate of HLA-G was closely related to depth of invasion and clinical stage (p<0.05 for all), but was not related to age, sex, tumor location, histologic grade, and nodal status (p>0.05 for all). Overexpression of HLA-G was a characteristic feature of Kazakh ESCC; HLA-G may be involved in Kazakh ESCC carcinogenesis and HPV infection.