Shanshan Guo

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Small urban and rural rivers usually face heavy metal pollution as a result of urbanization and industrial and agricultural activities. To elucidate the metabolic capacity of microbial communities on nitrogen and phosphorus cycle in river sediments under different heavy metal pollution backgrounds, this study collected samples in situ from two typical rivers, Tiquan River and Mianyuan River, with different heavy metal pollution levels. The microbial community structure and metabolic capacity of nitrogen and phosphorus cycles of sediment microorganisms were analyzed by high-throughput sequencing. The results showed that the major heavy metals in the sediments of the Tiquan River were Zn, Cu, Pb, and Cd with the contents of 103.80, 30.65, 25.95, and 0.44 mg/kg, respectively, while the major heavy metals in the sediments of the Mianyuan River were Cd and Cu with the contents of 0.60 and 27.81 mg/kg, respectively. The dominant bacteria Steroidobacter, Marmoricola, and Bacillus in the sediments of the Tiquan River had positive correlations with Cu, Zn, and Pb while are negatively correlated with Cd. Cd had a positive correlation with Rubrivivax, and Cu had a positive correlation with Gaiella in the sediments of the Mianyuan River. The dominant bacteria in the sediments of the Tiquan River showed strong phosphorus metabolic ability, and the dominant bacteria in the sediments of the Mianyuan River showed strong nitrogen metabolic ability, corresponding to the lower total phosphorus content in the Tiquan River and the higher total nitrogen content in the Mianyuan River. The results of this study showed that resistant bacteria became dominant bacteria due to the stress of heavy metals, and these bacteria showed strong nitrogen and phosphorus metabolic ability. It can provide theoretical support for the pollution prevention and control of small urban and rural rivers and have positive significance for maintaining the healthy development of rivers.

An abstract is unavailable. This article is available as a PDF only.

An abstract is unavailable. This article is available as a PDF only.

An abstract is unavailable. This article is available as a PDF only.

Purpose: To analyze the clinical outcomes of patients with regional persistent/recurrent nasopharyngeal carcinoma (NPC) who received neck dissection, and to evaluate the clinical benefit of postoperative adjuvant therapy (PAT) based on patients’ positive lymph node counts (PLNs), extracapsular spread (ECS) and preoperative plasma EBV DNA levels. Methods: From 2003 to 2017, 342 patients with regional persistent/recurrent NPC were included in this study. All patients were treated with neck dissection and 76 patients received PAT. Progression-free survival (PFS), overall survival (OS), distant metastasis-free survival (DMFS) and locoregional relapse-free survival (LRFS) were compared between groups using propensity score matching (PSM). Results: 152 patients without PAT treatment and 76 patients with PAT treatment were selected by the PSM. There was no significant difference in 2-year PFS (52.4% vs. 61.3%, P = 0.371), 2-year OS (91.9% vs. 90.5%, P = 0.097) or 2-year LRFS (66.3% vs. 67.9%, P = 0.872) between the two groups. However, the application of PAT brought survival benefits to patients in terms of 2-year DMFS (76.5% vs. 84.7%, P = 0.020). PLN, ECS and preoperative EBV DNA level remained independent risk factors for poorer PFS. Accordingly, patients were divided into low-risk and high-risk groups using receiver operating characteristic (ROC) curve; the 2-year PFS rates for two risk groups were 73.4% and 59.1% (P < 0.0001) respectively. The results showed that low-risk patients didn’t benefit from the addition of PAT. However, the 2-year DMFS rate was significantly improved in high-risk PAT-treated patients than those treated by neck dissection alone (83.7% vs. 71.7%, P = 0.023). Conclusions: PLNs, ECS and preoperative EBV DNA level are associated with the prognosis of patients with regional persistent/recurrent NPC. High-risk patients identified by PLNs, ECS and preoperative EBV DNA level may benefit from the addition of PAT after neck dissection.