Dong Cao

Restoring soil biota and dissolved organic matter (DOM) is essential for sustainable ecological restoration of coal mine sites. Protists, as key microbial predators, are recognized as regulators of multiple belowground processes, yet their roles in shaping DOM during ecological restoration remain poorly understood. Here, we investigated a field-scale coal mine ecological restoration chronosequence using vegetation surveys, ultrahigh-resolution Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR-MS), and high-throughput Illumina sequencing. Restoration increased plant diversity, coverage, and aboveground biomass, which are key resources for soil organic matter inputs. Soil DOM shifted toward more thermodynamically stable compounds, with enhanced chemodiversity during the restoration process. Protistan diversity, particularly of phagotrophic taxa, increased with restoration age, potentially exerting top-down control that increased bacterial diversity but suppressed fungal diversity. Co-occurrence network analysis and random forest modeling revealed that plant biomass was positively linked with phagotrophic diversity, which might influence DOM composition through direct transformation of organic matter (OM) or indirect regulation of bacterial transformation of OM, contributing to the accumulation of recalcitrant molecules with high stability. Together, these findings uncover a previously unrecognized trophic cascade linking protists to DOM chemodiversity at the molecular level, highlighting the importance of integrating protistan regulation into soil ecological restoration strategies for mine sites.

The partitioning and migration of per- and polyfluoroalkyl substances (PFAS) in soil may be regulated by active fractions such as dissolved organic matter (DOM), yet their role in this process has rarely been explored. Herein, the composition and distribution of PFAS and DOM between the soil–porewater phase in field soil were investigated to explore the interaction between PFAS and DOM. In the investigated areas, PFAS display significant spatial differences with the total concentration ranging from 3.14 to 50.92 ng/g. Under relatively high PFAS burden, DOM exhibits higher abundance of lipid/protein/amino-like compounds, indicative of its greater lability and bioavailability. Meanwhile, the relatively high Shannon index of DOM in those soils indicates that the chemodiversity of DOM may be related to the PFAS burden. Particularly, short-chain PFAS are more associated with these observed changes. Additionally, PFAS concentrations in porewater were associated with soil organic carbon content, whereas their soil–porewater partitioning showed no such correlation and was instead dictated by DOM components. Specifically, protein-like components facilitated the partitioning of PFAS into the porewater; in contrast, humic-like components promoted adsorption onto the soil phase. These findings suggest a potential link between PFAS and DOM, offering novel insights into the migration and fate of PFAS in soils.

Atmospheric fine particulate matter (PM_2.5) poses threats to the cardiovascular system. Red blood cells (RBCs) are the most abundant cells in blood, which are actively involved in multiple hematological diseases, such as blood clot formation and thrombosis. Exploring how PM_2.5 with spatiotemporal heterogeneity influences the hematological system by targeting RBCs would help gain insights into the deleterious effects of PM_2.5 and provide clues for finding the causative components therein. Herein, the PM_2.5 samples collected from 3 urban sites in Beijing (i.e., Chaoyang, Shunyi, and Yanqing districts) during 4 seasons of 2022 were studied for their toxicities to mouse RBCs, and the main contributing components were further explored through chemical analysis and correlation measure. The results showed that exposure to PM_2.5 samples decreased adenosine triphosphate (ATP) levels and increased phosphatidylserine (PS) externalization of RBCs, causing cell morphological deformity. The Pearson correlation analysis showed that the aromaticity of the dissolved organic matter (DOM) in PM_2.5 samples was positively correlated with PS exposure of RBCs, showing that the lignin-like compounds were the potential contributors. The negative correlation of zeta potentials of PM_2.5 samples with PS exposure of RBCs showed the particle-derived bioactivities of this airborne pollutant. The simulative test based on artificial nanomaterials of carbon black (CB) and oxidized CB (OCB) confirmed the crucial role of particulate carbon in PM_2.5-induced effects on RBCs, and soot with a certain oxidation degree was, thus, recognized as another contributor, given its ubiquitous existence in PM_2.5 samples. This study, for the first time, revealed PM_2.5-induced PS exposure of RBCs, and the causative components of DOM and soot were unraveled. Considering the inevitable contact of airborne PM_2.5 with RBCs in the blood circulatory system, the findings obtained herein would help bridge the gap between PM_2.5 exposure and the risk of cardiovascular diseases, like thrombogenesis.

We developed multiwavelength evanescent scattering microscopy (MWESM), which can acquire plasmonic nanoparticle images at the particle level using the evanescent field as the incident source and distinguish different LSPR (localized surface plasmon resonance) spectral peaks among four wavelengths. Our microscope could be easily and simply built by modifying a commercial total internal reflection fluorescence microscope (TIRFM) with the substitution of a beamsplitter and the addition of a semicircular stop. The ultrathin depth of illumination and rejection of the reflected incident source together contribute to the high sensitivity and contrast of single nanoparticle imaging. We first validated the capability of our imaging system in distinguishing plasmonic nanoparticles bearing different LSPR spectral peaks, and the results were consistent with the scattering spectra results of hyperspectral imaging. Moreover, we demonstrated high imaging quality from the aspects of the signal/noise ratio and point spread function of the single-particle images. Meaningfully, the system can be utilized in rapidly determining the concentration of toxic lead ions in environmental and biological samples with good linearity and sensitivity, based on single-particle evanescent scattering imaging through the detection of the alteration of the LSPR of silver nanoparticles. This system holds the potential to advance the field of nanoparticle imaging and foster the application of nanomaterials as sensors.

Natural organic matter (NOM) exhibits a distinctive electron-donating capacity (EDC) that serves a pivotal role in the redox reactions of contaminants and minerals through the transformation of electron-donating phenolic moieties. However, the ambiguity of the molecular transformation pathways (MTPs) that engender the EDC during NOM oxidation remains a significant issue. Here, MTPs that contribute to EDC were investigated by identifying the oxidized products of phenolic model compounds and NOM samples in direct or mediated electrochemical oxidation (DEO or MEO, respectively) using Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). It was found that the oxidation of newly formed phenolic-OH (ArOH) and the oxidative coupling reaction of the phenoxy radical are the main MTPs that directly contribute to EDC, in addition to the transformation of hydroquinones to quinones. Notably, the oxidative coupling reaction of ArOH contributed at least 22-42% to the EDC. Ferulic acid-like structures can also directly contribute to EDC by incorporating H₂O into their acrylic substituents. Furthermore, the opening of C rings can indirectly attenuate the EDC through structural alterations in the electron-donating process of NOM. Decarboxylation can either weaken or enhance the EDC depending on the structure of the phenolic moieties in NOM. These findings suggest that the EDC of NOM is a comprehensive result of multiple NOM MTPs, involving not only ArOH oxidation but also the addition of H₂O to olefinic bonds and bond-breaking reactions. Our work provides molecular evidence that aids in the comprehension of the multiple EDC-associated transformation pathways of NOM.

Glacier-retreated areas are ideal areas to study soil biogeochemical processes during vegetation succession, because of the limited effect of other environmental and climatic factors. In this study, the changes of soil dissolved organic matter (DOM) and its relationship with microbial communities along the Hailuogou Glacier forefield chronosequence were investigated. Both microbial diversity and DOM molecular chemodiversity recovered rapidly at the initial stage, indicating the pioneering role of microorganisms in soil formation and development. The chemical stability of soil organic matter enhanced with vegetation succession due to the retaining of compounds with high oxidation state and aromaticity. The molecular composition of DOM affected microbial communities, while microorganisms tended to utilize labile components to form refractory components. This complex relationship network between microorganisms and DOM components played an important role in the development of soil organic matter as well as the formation of stable soil carbon pool in glacier-retreated areas.