Research progress and perspective on sludge anaerobic digestion technology: A bibliometric analysis.

Rational disposal of sludge is an ongoing concern. This work is the first attempt for in-depth statistical analysis of anaerobic digestion (AD) research in recent three decades (1986-2022) using both quantitative and qualitative approaches in bibliometrics to investigate the research progress, trends and hot spots. All publications in the Web of Science Core Collection database from 1986 to April 4, 2022 were analyzed. Results showed that the research on AD started in 1999 and the number of papers significantly increased since 2012. The research about the disposal of sewage sludge mainly focuses on energy recovery (e.g. methane and short chain volatile organic acids) by AD. Besides, different pretreatment technologies were studied in this study to eliminate the negative effects on the disposal of sludge caused by hydrolysis (rate-limiting step of AD), water content (increasing the costs) and heavy metal (toxic to the environment) of sludge. Of those, the treatment technologies related to direct interspecies electron transfer were worth further studied in the future. Towards that end, iron conductive material, iron-based advanced oxidation and biological treatment were concluded as the prospective technologies and worth to further study.

Positively Charged Amino Acid-Modulated Interfacial Chemistry and Deposition Textures for Highly Reversible Zinc Anodes.

Interfacial active water molecule-induced parasitic reactions and stochastic Zn2+ transport-caused dendrite issue significantly impede the implementation of aqueous Zn-ion batteries. Herein, three positively charged amino acids, namely arginine, histidine, and lysine, were utilized as adsorption-type electrolyte additives to enhance the stability and reversibility of Zn anodes. Combined theoretical and experimental analyses verified that these amino acid cations can synergistically modulate the interfacial microenvironment and promote orientational Zn deposition. The adsorbed amino acid cations reconfigured the interfacial electric double layer structure, forming SO42-- and H2O-poor interfaces, thereby retarding hydrogen evolution and corrosion side reactions. Simultaneously, the preferential adsorption of the amino acid cations at specific facets induced crystallographic orientational Zn deposition along unterminated facets. Three deposition architectures, namely planar texture, subvertical alignment, and vertical erection, were obtained, all effectively inhibiting dendrite formation. Consequently, symmetric cells with the three amino acid cations exhibited high stripping/plating reversibility of over 2000 cycles at 5 mA cm-2. Moreover, MnO2-based full cells exhibited markedly improved stabilities compared with their additive-free counterparts.

Value of turbo spin echo-based diffusion-weighted imaging in the differential diagnosis of benign and malignant solitary pulmonary lesions.

To quantitatively assess the diagnostic efficacy of multiple parameters derived from multi-b-value diffusion-weighted imaging (DWI) using turbo spin echo (TSE)-based acquisition techniques in patients with solitary pulmonary lesions (SPLs). A total of 105 patients with SPLs underwent lung DWI using single-shot TSE-based acquisition techniques and multiple b values. The apparent diffusion coefficient (ADC), intravoxel incoherent motion (IVIM) parameters, and lesion-to-spinal cord signal intensity ratio (LSR), were analyzed to compare the benign and malignant groups using the Mann-Whitney U test and receiver operating characteristic analysis. The Dstar values observed in lung cancer were slightly lower than those observed in pulmonary benign lesions (28.164 ± 31.950 versus 32.917 ± 34.184; Z = -2.239, p = 0.025). The LSR values were significantly higher in lung cancer than in benign lesions (1.137 ± 0.581 versus 0.614 ± 0.442; Z = - 4.522, p < 0.001). Additionally, the ADC800, ADCtotal, and D values were all significantly lower in lung cancer than in the benign lesions (Z = - 5.054, -5.370, and -6.047, respectively, all p < 0.001), whereas the f values did not exhibit any statistically significant difference between the two groups. D had the highest area under the curve (AUC = 0.887), followed by ADCtotal (AUC = 0.844), ADC800 (AUC = 0.824), and LSR (AUC = 0.789). The LSR, ADC800, ADCtotal, and D values did not differ statistically significantly in diagnostic effectiveness. Lung DWI using TSE is feasible for differentiating SPLs. The LSR method, conventional DWI, and IVIM have comparable diagnostic efficacy for assessing SPLs.

Pangenome characterization and analysis of the NAC gene family reveals genes for Sclerotinia sclerotiorum resistance in sunflower (Helianthus annuus).

BACKGROUND: Sunflower (Helianthus annuus) is one of the most important economic crops in oilseed production worldwide. The different cultivars exhibit variability in their resistance genes. The NAC transcription factor (TF) family plays diverse roles in plant development and stress responses. With the completion of the H. annuus genome sequence, the entire complement of genes coding for NACs has been identified. However, the reference genome of a single individual cannot cover all the genetic information of the species. RESULTS: Considering only a single reference genome to study gene families will miss many meaningful genes. A pangenome-wide survey and characterization of the NAC genes in sunflower species were conducted. In total, 139 HaNAC genes are identified, of which 114 are core and 25 are variable. Phylogenetic analysis of sunflower NAC proteins categorizes these proteins into 16 subgroups. 138 HaNACs are randomly distributed on 17 chromosomes. SNP-based haplotype analysis shows haplotype diversity of the HaNAC genes in wild accessions is richer than in landraces and modern cultivars. Ten HaNAC genes in the basal stalk rot (BSR) resistance quantitative trait loci (QTL) are found. A total of 26 HaNAC genes are differentially expressed in response to Sclerotinia head rot (SHR). A total of 137 HaNAC genes are annotated in Gene Ontology (GO) and are classified into 24 functional groups. GO functional enrichment analysis reveals that HaNAC genes are involved in various functions of the biological process. CONCLUSIONS: We identified NAC genes in H. annuus (HaNAC) on a pangenome-wide scale and analyzed S. sclerotiorum resistance-related NACs. This study provided a theoretical basis for further genomic improvement targeting resistance-related NAC genes in sunflowers.

[Retracted] MicroRNA­19b promotes the migration and invasion of ovarian cancer cells by inhibiting the PTEN/AKT signaling pathway.

[This retracts the article DOI: 10.3892/ol.2018.8695.].

Research Progress in Pharmacological Effects and Mechanisms of Angelica sinensis against Cardiovascular and Cerebrovascular Diseases.

Angelica sinensis (Oliv.) Diels (A. sinensis) is a medicinal and edible values substance, which could promote blood circulation and enrich blood. It possesses rich chemical components and nutrients, which have significant therapeutic effects on cardiovascular and cerebrovascular diseases. It is commonly used for the prevention and treatment of cardiovascular and cerebrovascular diseases in the elderly, especially in improving ischemic damage to the heart and brain, protecting vascular cells, and regulating inflammatory reactions. This article reviews the main pharmacological effects and clinical research of A. sinensis on cardiovascular and cerebrovascular diseases in recent years, explores the effect of its chemical components on cardiovascular and cerebrovascular diseases by regulating the expression of functional proteins and inhibiting inflammation, anti-apoptosis, and antioxidant mechanisms. It provides a reference for further research on A. sinensis and the development of related drugs. It provides a new reference direction for the in-depth research and application of A. sinensis in the prevention, improvement, and treatment of cardiovascular and cerebrovascular diseases.

Clonal expansion of shared T cell receptors reveals the existence of immune commonality among different lesions of synchronous multiple primary lung cancer.

The increase in the detection rate of synchronous multiple primary lung cancer (MPLC) has posed remarkable clinical challenges due to the limited understanding of its pathogenesis and molecular features. Here, comprehensive comparisons of genomic and immunologic features between MPLC and solitary lung cancer nodule (SN), as well as different lesions of the same patient, were performed. Compared with SN, MPLC displayed a lower rate of EGFR mutation but higher rates of BRAF, MAP2K1, and MTOR mutation, which function exactly in the upstream and downstream of the same signaling pathway. Considerable heterogeneity in T cell receptor (TCR) repertoire exists among not only different patients but also among different lesions of the same patient. Invasive lesions of MPLC exhibited significantly higher TCR diversity and lower TCR expansion than those of SN. Intriguingly, different lesions of the same patient always shared a certain proportion of TCR clonotypes. Significant clonal expansion could be observed in shared TCR clonotypes, particularly in those existing in all lesions of the same patient. In conclusion, this study provided evidences of the distinctive mutational landscape, activation of oncogenic signaling pathways, and TCR repertoire in MPLC as compared with SN. The significant clonal expansion of shared TCR clonotypes demonstrated the existence of immune commonality among different lesions of the same patient and shed new light on the individually tailored precision therapy for MPLC.

Molecular mechanism of abscisic acid signaling response factor VcbZIP55 to promote anthocyanin biosynthesis in blueberry (Vaccinium corymbosum).

A high content of anthocyanin in blueberry (Vaccinium corymbosum) is an important indicator to evaluate fruit quality. Abscisic acid (ABA) can promote anthocyanin biosynthesis, but since the molecular mechanism is unclear, clarifying the mechanism will improve for blueberry breeding and cultivation regulation. VcbZIP55 regulating anthocyanin synthesis in blueberry were screened and mined using the published Isoform-sequencing, RNA-Seq and qRT-PCR at different fruit developmental stages. Blueberry genetic transformation and transgenic experiments confirmed that VcbZIP55 could promote anthocyanin biosynthesis in blueberry adventitious buds, tobacco leaves, blueberry leaves and blueberry fruit. VcbZIP55 responded to ABA signals and its expression was upregulated in blueberry fruit. In addition, using VcbZIP55 for Yeast one hybrid assay (Y1H) and transient expression in tobacco leaves demonstrated an interaction between VcbZIP55 and a G-Box motif on the VcMYB1 promoter to activate the expression of VcMYB1. This study will lay the theoretical foundation for the molecular mechanisms of phytohormone regulation responsible for anthocyanin synthesis and provide theoretical support for blueberry quality improvement.

Prognostic Significance of Immune Cell Infiltration in Muscle-invasive Bladder Cancer Treated with Definitive Chemoradiation: A Secondary Analysis of RTOG 0524 and RTOG 0712.

Chemoradiation therapy (CRT) is a treatment for muscle-invasive bladder cancer (MIBC). Using a novel transcriptomic profiling panel, we validated prognostic immune biomarkers to CRT using 70 pretreatment tumor samples from prospective trials of MIBC (NRG/RTOG 0524 and 0712). Disease-free survival (DFS) and overall survival (OS) were estimated via the Kaplan-Meier method and stratified by genes correlated with immune cell activation. Cox proportional-hazards models were used to assess group differences. Clustering of gene expression profiles revealed that the cluster with high immune cell content was associated with longer DFS (hazard ratio [HR] 0.53, 95% confidence interval [CI] 0.26-1.10; p = 0.071) and OS (HR 0.48, 95% CI 0.24-0.97; p = 0.040) than the cluster with low immune cell content. Higher expression of T-cell infiltration genes (CD8A and ICOS) was associated with longer DFS (HR 0.40, 95% CI 0.21-0.75; p = 0.005) and OS (HR 0.49, 95% CI 0.25-0.94; p = 0.033). Higher IDO1 expression (IFNγ signature) was also associated with longer DFS (HR 0.44, 95% CI 0.24-0.88; p = 0.021) and OS (HR 0.49, 95% CI 0.24-0.99; p = 0.048). These findings should be validated in prospective CRT trials that include biomarkers, particularly for trials incorporating immunotherapy for MIBC. PATIENT SUMMARY: We analyzed patient samples from two clinical trials (NRG/RTOG 0524 and 0712) of chemoradiation for muscle-invasive bladder cancer using a novel method to assess immune cells in the tumor microenvironment. Higher expression of genes associated with immune activation and high overall immune-cell content were associated with better disease-free survival and overall survival for patients treated with chemoradiation.

Genomic Evidence for the Complex Evolutionary History of Macaques (Genus Macaca).

The genus Macaca is widely distributed, occupies a variety of habitats, shows diverse phenotypic characteristics, and is one of the best-studied genera of nonhuman primates. Here, we reported five re-sequencing Macaca genomes, including one M. cyclopis, one M. fuscata, one M. thibetana, one M. silenus, and one M. sylvanus. Together with published genomes of other macaque species, we combined 20 genome sequences of 10 macaque species to investigate the gene introgression and genetic differences among the species. The network analysis of the SNV-fragment trees indicates a reticular phylogeny of macaque species. Combining the results from various analytical methods, we identified extensive ancient introgression events among macaque species. The multiple introgression signals between different species groups were also observed, such as between fascicularis group species and silenus group species. However, gene flow signals between fascicularis and sinica group were not as strong as those between fascicularis group and silenus group. On the other hand, the unidirect gene flow in M. arctoides probably occurred between the progenitor of M. arctoides and the common ancestor of fascicularis group. Our study also shows that the genetic backgrounds and genetic diversity of different macaques vary dramatically among species, even among populations of the same species. In conclusion, using whole genome sequences and multiple methods, we have studied the evolutionary history of the genus Macaca and provided evidence for extensive introgression among the species.

Soil metabolomics: Deciphering underground metabolic webs in terrestrial ecosystems.

Soil metabolomics is an emerging approach for profiling diverse small molecule metabolites, i.e., metabolomes, in the soil. Soil metabolites, including fatty acids, amino acids, lipids, organic acids, sugars, and volatile organic compounds, often contain essential nutrients such as nitrogen, phosphorus, and sulfur and are directly linked to soil biogeochemical cycles driven by soil microorganisms. This paper presents an overview of methods for analyzing soil metabolites and the state-of-the-art of soil metabolomics in relation to soil nutrient cycling. We describe important applications of metabolomics in studying soil carbon cycling and sequestration, and the response of soil organic pools to changing environmental conditions. This includes using metabolomics to provide new insights into the close relationships between soil microbiome and metabolome, as well as responses of soil metabolome to plant and environmental stresses such as soil contamination. We also highlight the advantage of using soil metabolomics to study the biogeochemical cycles of elements and suggest that future research needs to better understand factors driving soil function and health.

Predicting the bioavailability of polycyclic aromatic hydrocarbons in rhizosphere soil using a new novel in situ solid-phase microextraction technique.

In situ measurement of the bioavailability of organic pollutants in soil is crucial for understanding their environmental behavior and assessing health risks. Due to the high heterogeneity of soil, microscale determination is crucial for achieving high accuracy, but few methods are available. In this study, microsized probes coated with polydimethylsiloxane (PDMS) were used to measure the bioavailability of polycyclic aromatic hydrocarbons (PAHs) in soil in situ. The concentrations of PAHs enriched by the PDMS-coated probes correlated well with the results of bioassays using earthworms (R2 = 0.92-0.99) and ryegrass roots (R2 = 0.92-0.99). Compared with other chemical extraction methods, such as n-butanol extraction, the proposed method has advantages such as in situ operation, microvolume analysis, and negligible interference to the soil environment. In the soil rhizosphere zone, PAHs bioavailability decreased in the following order: rhizosphere > near-rhizosphere > far-rhizosphere. The bioavailability of PAHs in soil amended with biochar was also successfully characterized by the proposed method. Thus, this study developed an in situ and microscale method to predict the bioavailability of organic pollutants in contaminated soils and provides new insight into migration and transformation processes in rhizosphere soil.

CdgB Regulates Morphological Differentiation and Toyocamycin Production in Streptomyces diastatochromogenes 1628.

Bis (3',5')-cyclic diguanylic acid (c-di-GMP) is a ubiquitous second messenger that controls several metabolic pathways in bacteria. In Streptomyces, c-di-GMP is associated with morphological differentiation, which is related to secondary metabolite production. In this study, we identified and characterized a diguanylate cyclase (DGC), CdgB, from Streptomyces diastatochromogenes 1628, which may be involved in c-di-GMP synthesis, through genetic and biochemical analyses. To further investigate the role of CdgB, the cdgB-deleted mutant strain Δ-cdgB and the cdgB-overexpressing mutant strain O-cdgB were constructed by genetic engineering. A phenotypic analysis revealed that the O-cdgB colonies exhibited reduced mycelium formation, whereas the Δ-cdgB colonies displayed wrinkled surfaces and shriveled mycelia. Notably, O-cdgB demonstrated a significant increase in the toyocamycin (TM) yield by 47.3%, from 253 to 374 mg/L, within 10 days. This increase was accompanied by a 6.7% elevation in the intracellular concentration of c-di-GMP and a higher transcriptional level of the toy cluster within four days. Conversely, Δ-cdgB showed a lower c-di-GMP concentration (reduced by 6.2%) in vivo and a reduced toyocamycin production (decreased by 28.9%, from 253 to 180 mg/L) after 10 days. In addition, S. diastatochromogenes 1628 exhibited a slightly higher inhibitory effect against Fusarium oxysporum f. sp. cucumerinum and Rhizoctonia solani compared to Δ-cdgB, but a lower inhibition rate than that of O-cdgB. The results imply that CdgB provides a foundational function for metabolism and the activation of secondary metabolism in S. diastatochromogenes 1628.

Reprogramming Chromosome Ends by Functional Histone Acetylation.

Cancers harness embryonic programs to evade aging and promote survival. Normally, sequences at chromosome ends called telomeres shorten with cell division, serving as a countdown clock to limit cell replication. Therefore, a crucial aspect of cancerous transformation is avoiding replicative aging by activation of telomere repair programs. Mouse embryonic stem cells (mESCs) activate a transient expression of the gene Zscan4, which correlates with chromatin de-condensation and telomere extension. Head and neck squamous cell carcinoma (HNSCC) cancers reactivate ZSCAN4, which in turn regulates the phenotype of cancer stem cells (CSCs). Our study reveals a new role for human ZSCAN4 in facilitating functional histone H3 acetylation at telomere chromatin. Next-generation sequencing indicates ZSCAN4 enrichment at telomere chromatin. These changes correlate with ZSCAN4-induced histone H3 acetylation and telomere elongation, while CRISPR/Cas9 knockout of ZSCAN4 leads to reduced H3 acetylation and telomere shortening. Our study elucidates the intricate involvement of ZSCAN4 and its significant contribution to telomere chromatin remodeling. These findings suggest that ZSCAN4 induction serves as a novel link between 'stemness' and telomere maintenance. Targeting ZSCAN4 may offer new therapeutic approaches to effectively limit or enhance the replicative lifespan of stem cells and cancer cells.

Chemical Plasma Membrane Perforation Generated by a Microfluidic Probe for Single-Cell Intracellular Protein Delivery.

Efficient and convenient delivery of exogenous molecules into cells is important for cell biology research. However, many intracellular delivery methods require carrier-mediated or physical field assistance, complicating the delivery process. Here, a general, simple, and effective method for in situ single-cell intracellular delivery is reported. A solution containing digitonin and cargo is precisely applied to single cells using a microfluidic probe. Digitonin binds to cholesterol in the plasma membrane to induce perforation, and the cargo enters the cell through the pore. By optimizing parameters, propidium iodide (0.67 kDa) and FITC-dextran (10, 40, and 150 kDa) can be successfully introduced into single cells within 3 min while maintaining cell viability. To prove the potential of this method for cell research, we delivered cytochrome C (13 kDa) and cyclophilin A (18 kDa) into cells by this method. The delivered cytochrome C successfully induces cell apoptosis by activating the caspase pathway, and cyclophilin A performs an antioxidant effect in the cells, which may enhance the drug resistance of glioma cells. It is believed that this method will be an attractive tool for single-cell intracellular delivery.

TMEM9 promotes lung adenocarcinoma progression via activating the MEK/ERK/STAT3 pathway to induce VEGF expression.

Abnormal Transmembrane protein 9 (TMEM9) expression has been identified in various human tumors. However, the prognostic potential and mechanistic role of TMEM9 in lung adenocarcinoma (LUAD) remain unclear. Here, we first found a significant upregulation of TMEM9 in LUAD tissues, and TMEM9 expression was positively correlated with microvessel density (MVD), T stage, and clinical stage. Survival analysis demonstrated TMEM9 was an independent indicator of poor prognosis in LUAD patients. In addition, downregulation of TMEM9 suppressed tumor growth and metastasis in vitro and in vivo models, and reduced HUVEC proliferation, migration, and tube formation in a cancer cell/HUVEC coculture model. Furthermore, TMEM9 upregulated VEGF expression, and VEGF-neutralizing antibodies reversed HUVEC angiogenesis and cancer cell migration ability caused by overexpression of TMEM9. In contrast, recombinant VEGF (rVEGF) abolished the inhibitory effect of TMEM9-knockdown LUAD cells on HUVEC angiogenesis and tumor cell migration. Moreover, we showed that TMEM9 upregulated VEGF expression by activating the mitogen-activated protein kinase/extracellular signal-regulated kinase/STAT3 (MEK/ERK/STAT3) pathway. Together, our study provides mechanistic insights into the role of TMEM9 in LUAD and highlights the potential of targeting the TMEM9/MEK/ERK/STAT3/VEGF pathway as a novel therapy for preventing LUAD progression.

Hybrid dual mean-teacher network with double-uncertainty guidance for semi-supervised segmentation of magnetic resonance images.

Semi-supervised learning has made significant progress in medical image segmentation. However, existing methods primarily utilize information from a single dimensionality, resulting in sub-optimal performance on challenging magnetic resonance imaging (MRI) data with multiple segmentation objects and anisotropic resolution. To address this issue, we present a Hybrid Dual Mean-Teacher (HD-Teacher) model with hybrid, semi-supervised, and multi-task learning to achieve effective semi-supervised segmentation. HD-Teacher employs a 2D and a 3D mean-teacher network to produce segmentation labels and signed distance fields from the hybrid information captured in both dimensionalities. This hybrid mechanism allows HD-Teacher to utilize features from 2D, 3D, or both dimensions as needed. Outputs from 2D and 3D teacher models are dynamically combined based on confidence scores, forming a single hybrid prediction with estimated uncertainty. We propose a hybrid regularization module to encourage both student models to produce results close to the uncertainty-weighted hybrid prediction to further improve their feature extraction capability. Extensive experiments of binary and multi-class segmentation conducted on three MRI datasets demonstrated that the proposed framework could (1) significantly outperform state-of-the-art semi-supervised methods (2) surpass a fully-supervised VNet trained on substantially more annotated data, and (3) perform on par with human raters on muscle and bone segmentation task. Code will be available at https://github.com/ThisGame42/Hybrid-Teacher.

Viscoelastic Extracellular Matrix Enhances Epigenetic Remodeling and Cellular Plasticity.

Living tissue and extracellular matrices possess viscoelastic properties, but understanding how viscoelastic matrix regulates chromatin and the epigenome is limited. Here, we find that the regulation of the epigenetic state by the viscoelastic matrix is more pronounced on softer matrices. Cells on viscoelastic matrices exhibit larger nuclei, increased nuclear lamina ruffling, loosely organized chromatin, and faster chromatin dynamics, compared to those on elastic matrices. These changes are accompanied by a global increase in euchromatic marks and a local increase in chromatin accessibility at the cis -regulatory elements associated with neuronal and pluripotent genes. Consequently, viscoelastic matrices enhanced the efficiency of reprogramming fibroblasts into neurons and induced pluripotent stem cells, respectively. Together, our findings demonstrate the key roles of matrix viscoelasticity in the regulation of epigenetic state, and uncover a new mechanism of biophysical regulation of chromatin and cell reprogramming, with implications for the design of smart materials to engineer cell fate.

Investigation of the pan-cancer property of FNDC1 and its molecular mechanism to promote lung adenocarcinoma metastasis.

BACKGROUND: Fibronectin type III domain containing 1 (FNDC1) has been associated with the metastasis of many tumors, but its function in lung cancer remains uncertain. METHODS: FNDC1 expression was analyzed in The Cancer Genome Atlas (TCGA) and Genotype-Tissue Expression (GTEx), evaluate its prognostic value. Gene Set Enrichment Analysis (GSEA) enrichment analysis of differential expression of FNDC1 in lung cancer. The expression of FNDC1 was detected in five types of lung cancer cells, and screened to establish FNDC1 stable knockdown cell strains. To observe the migration and invasion ability of lung cancer cells after FNDC1 knockdown. Finally, we used rhIL-6 to interfere with the stable knockdown of FNDC1 in A549 cells and observed the recovery of migration and invasion. RESULT: Our results showed that FNDC1 expression was increased in 21 tumor tissues, including lung cancer, and was associated with poor prognosis in five cancers, including lung adenocarcinoma (LUAD) (P < 0.05). GSEA enrichment analysis showed that FNDC1 was related to the pathways involved the JAK-STAT signaling pathway. Stable knockdown of FNDC1 in A549 and H292 cells resulted in decreased migration and invasion ability of both cells, accompanied by decreased expression of MMP-2 and Snail, and a significant decline in the expression of p-JAK2 and p-STAT3. The suppressive effect of FNDC1 knockdown on lung cancer cell metastasis counteracted by the JAK-STAT agonist rhIL-6 were presented in the nude mouse metastatic tumor model. CONCLUSION: FNDC1 is implicated in poor prognosis of a diverse range of malignant tumors, which can promote metastasis and invasion of lung cancer through the JAK2-STAT3 signaling pathway.

Occurrence of organophosphorus flame retardants in Xiangjiang River: Spatiotemporal variations, potential affecting factors, and source apportionment.

The environmental occurrence of organophosphorus flame retardants (OPFRs) is receiving increasing attention. However, their distribution in the Xiangjiang River, an important tributary in the middle reaches of the Yangtze River, is still uncharacterized, and the potential factors influencing their distribution have not been adequately surveyed. In this study, the occurrence of OPFRs in the Xiangjiang River was comprehensively investigated from upstream to downstream seasonally. Fourteen OPFRs were detected in the sampling area, with a total concentration (∑OPFRs) ranging from 3.16 to 462 ng/L, among which tris(1-chloro-2-propyl) phosphate was identified as the primary pollutant (ND - 379 ng/L). Specifically, ∑OPFRs were significantly lower in the wet season than in the dry season, which may be due to the dilution effect of river flow and enhanced volatilization caused by higher water temperatures. Additionally, Changsha (during the dry season) and Zhuzhou (during the wet season) exhibited higher pollution levels than other cities. According to the Redundancy analysis, water quality parameters accounted for 35.7% of the variation in the occurrence of OPFRs, in which temperature, ammonia nitrogen content, dissolved oxygen, and chemical oxygen demand were identified as the potential influencing factors, accounting for 28.1%, 27.2%, 24.1%, and 11.5% of the total variation, respectively. The results of the Positive Matrix Factorization analysis revealed that transport and industrial emissions were the major sources of OPFRs in Xiangjiang River. In addition, there were no high-ecological risk cases for any individual OPFRs, although tris(2-ethylhexyl) phosphate and tributoxyethyl phosphate presented a low-to-medium risk level. And the results of mixture risk quotients indicated that medium-risk sites were concentrated in the Chang-Zhu-Tan region. This study enriches the global data of OPFRs pollution and contributes to the scientific management and control of pollution.