[Evaluation of Shallow Groundwater Quality and Optimization of Monitoring Indicators in Nanchang].

In the process of groundwater environmental monitoring, while ensuring the representativeness of groundwater quality evaluation, the number of monitoring indicators should be optimized as much as possible, which is of great significance to groundwater environmental management. Based on monitoring data of shallow groundwater in Nanchang in 2014 and 2019, the chemical characteristics of water and the changes in water quality were analyzed via statistical analysis, a Piper three-line diagram, and the entropy-weighted water quality index (EWQI). Furthermore, a key indicator optimization method based on water quality evaluation was constructed by coupling stepwise multiple linear regression analysis. The feasibility of this method was also evaluated. The results showed that the water chemistry type of groundwater in 2014 and 2019 was mainly HCO3-Ca, and the five abnormal indicators pH value, NO3-, I-, Fe, and Mn were the main influencing factors of water quality change. The water quality in 2019 was generally higher than that in 2014, which was considered as overall "moderate," and the average EWQI values of the two years were 53.72 and 82.34, respectively. The optimal model EWQImin-4 constructed based on the key indicator optimization method could better represent the actual EWQI; the key indicators included Mn, NO3-, TH, Fe, pH value, and I-; and the determination coefficient (R2) and percentage error (PE) values were 0.865 and 10.61%, respectively. Therefore, the optimization method of groundwater monitoring indicators based on entropy-weighted water quality evaluation could be used as an important reference for optimizing monitoring indicators and provide a method for regional groundwater environmental management.

[Effect of Er:YAG laser in pulp revascularization in miniature pigs].

PURPUSE: To compare the effectiveness of Er:YAG laser and Ca(OH)2 in pulp revascularization in miniature pigs. METHODS: The second and third premolars of three 14-15-month-old miniature pigs were randomly divided into three groups: laser group, medication group and negative control group. After establishment of pulp necrosis model in each group, the negative control group had no more procedures, while the laser group and medication group were treated with pulp revascularization. Intracanal antisepsis operation was conducted using Er:YAG laser in laser group and Ca(OH)2 in medication group. The maxillary first premolars, as a positive control group, were left untreated and grew naturally. Three months after surgery, X-ray and cone-beam CT(CBCT) were taken. The animals were sacrificed, and the teeth were used to make H-E staining sections. The development of the teeth and the histological manifestations in the root canals of both groups were compared and evaluated by radiographic and histological assessment. SPSS 24.0 software package was used for statistical analysis of the data. RESULTS: Radiographic results showed that 3 months after surgery, apical foramen was closed in the laser group and the medication group. It also showed that intracanal calcification, and some specimens manifested root absorption. There was no significant difference between the two groups in the aspects of increase of root length, root thickness, or decrease of apical foramen size(P>0.05). Histological results showed that there was dentin-like and cementum-like tissue deposition along the root canal walls; apical closure was apparent; and fibrous connective tissue and cementum-like tissue or bone-like tissue formation in the root canal space were evident in the laser group and the medication group 3 months after surgery. There was no significant difference in the histological findings between the two groups(P>0.05). CONCLUSIONS: Er: YAG laser can be applied to pulp revascularization in miniature pigs, and the effect is equivalent to that of intracanal medication using Ca(OH)2.

Risk-Based Prioritization Method for the Classification of Groundwater Pollution from Hazardous Waste Landfills.

Hazardous waste landfill sites are a significant source of groundwater pollution. To ensure that these landfills with a significantly high risk of groundwater contamination are properly managed, a risk-based ranking method related to groundwater contamination is needed. In this research, a risk-based prioritization method for the classification of groundwater pollution from hazardous waste landfills was established. The method encompasses five phases, including risk pre-screening, indicator selection, characterization, classification and, lastly, validation. In the risk ranking index system employed here, 14 indicators involving hazardous waste landfills and migration in the vadose zone as well as aquifer were selected. The boundary of each indicator was determined by K-means cluster analysis and the weight of each indicator was calculated by principal component analysis. These methods were applied to 37 hazardous waste landfills in China. The result showed that the risk for groundwater contamination from hazardous waste landfills could be ranked into three classes from low to high risk. In all, 62.2 % of the hazardous waste landfill sites were classified in the low and medium risk classes. The process simulation method and standardized anomalies were used to validate the result of risk ranking; the results were consistent with the simulated results related to the characteristics of contamination. The risk ranking method was feasible, valid and can provide reference data related to risk management for groundwater contamination at hazardous waste landfill sites.

Ischemic preconditioning attenuates brain injury induced by ischemia/reperfusion during moderate hypothermia low-flow procedures.

OBJECTIVE: We determined the effects of ischemic preconditioning (IP) on apoptosis in a rat model of brain injury induced by cerebral ischemia/reperfusion following a moderate hypothermic low-flow (MHLF) procedure. METHODS: A total of 180 rats were randomly divided into three groups. The surgery group was subjected to body temperature reduction and bilateral common carotid artery occlusion for 120 min at 25 ± 0.5°C, followed by artery reopening and rewarming. The sham-surgery group underwent the same procedure, but common carotid arteries were not occluded. The ischemic preconditioning-treated surgery group was pretreated with four cycles of 2 min occlusion of bilateral common carotid arteries and 5 min reperfusion, before 120 min of cerebral ischemia. Regional cerebral blood flow was measured continuously in 10 rats per group using laser Doppler flowmetry. We investigated brain cell apoptosis levels and mitochondrial apoptosis signaling pathway components at various time points following reperfusion. RESULTS: The ischemic preconditioning-treated surgery group displayed decreases in apoptotic cell numbers and apoptotic protein expression levels after the procedure at 6 h, 24 h, 72 h, and 7 d. Ischemic preconditioning inhibited cytochrome c release, caspase-3 activation, and mitochondrial apoptosis signaling pathway activation. CONCLUSION: The protective effects of ischemic preconditioning were associated with a reduction of DNA fragmentation, and inhibition of mitochondrial cytochrome c release and caspase-3 activation, which alleviated cerebral ischemia/reperfusion injury after moderate hypothermic low flow in rats. These findings highlight the potential of ischemic preconditioning as a neuroprotective therapy for surgery involving MHLF.

[Simulation on contamination forecast and control of groundwater in a certain hazardous waste landfill].

On the basis of site investigation and data collection of a certain hazardous waste landfill, the groundwater flow and solute transport coupled models were established by applying Visual Modflow software, which was used to conduct a numerical simulation that forecast the transport process of Cr6+ in groundwater and the effects of three control measures (ground-harden, leakage-proof barriers and drainage ditches) of contaminants transport after leachate leakage happened in impermeable layer of the landfill. The results show that the contamination plume of Cr6+ transports with groundwater flow direction, the contamination rang would reach the pool's boundary in 10 years, and the distance of contamination transport is 1 450 m. But the diffusion range of contamination plume would not be obviously expanded between 10 and 20 years. While the ground is hardened, the contamination plume would not reach the pool's boundary in 20 years. When the leakage-proof barrier is set in the bottom of water table aquifer, the concentration of Cr6+ is higher than that the leakage-proof barrier is unset, but the result is just opposite when setting the leakage-proof barrier in the bottom of underlying aquifer. The range of contamination plume is effectively controlled by setting drainage ditches that water discharge is 2 642 m3 x d(-1), which makes the monitoring wells would not be contaminated in 20 years. Moreover, combining the ground-harden with drainage ditches can get the best effect in controlling contaminants diffusion, and meanwhile, the drainage ditches' daily discharge is reduced to 1 878 m3 x d(-1). Therefore, it is suggested that the control measure combining the ground-harden with drainage ditches should apply to prevent contamination diffusion in groundwater when leachate leakage have happened in impermeable layer of the landfill.

[Degradation effect and mechanism of 2,4-DNT by reduction-ZPF catalytic oxidation].

ZPF(zeoliteartificial pillared by alpha-FeOOH) which prepared in the laboratory and characterized by FTIR and XRD was used as catalyst, and was tested for its activity in catalytic H2O2, of 2,4-DNT, which is persistent and difficult to be degraded in groundwater. The degradation of 2,4-DNT was examined at different pHs in the reduction, catalytic oxidation and combination technology of reduction-catalytic oxidation reaction systems. Moreover, the removal effect of 2,4-DNT was compared by these three approaches and the catalytic oxidation mechanism was analyzed. The results demonstrated that the removal effect of 2,4-DNT reduced to 2,4-DAT was up to 96.6% in 120 min at pH = 5, which was 1.2, 2.0 times of the rate at pH 7, pH 9 respectively. The catalytic effect was various at different pHs and more significant when the pH close to the zero point of charge of alpha-FeOOH. The order of removal effect of 2,4-DNT at different pHs was pH = 7 > pH = 9 > pH = 5. Compared to single reduction or catalytic oxidation, the removal effect of combination technology was 57.4%, which was evidently improved on the base of 2,4-DNT reduced to 2,4-DAT. The degradation of 2,4-DNT in the presence of ZPF/H2O2 follows a first-order kinetic model and the k(obs) was 0.002 7 min(-1). Due to the concentration of dissolved Fe ion was far less than 0.07 mmol/L, the mechanism was heterogeneous Fenton reaction acting on the surface of the catalyst. Therefore the combination technology was superior to the single treatment of reduction or catalytic oxidation.