Seawater intrusion-triggered high fluoride groundwater development on the eastern coast of China.

High-fluoride groundwater is commonly found in coastal areas worldwide, while its formation mechanism remains elusive. Herein, a comprehensive study was performed to identify the major controlling factor of high-fluoride groundwater occurrence along the eastern coast of China. Hydrogeochemical methods were employed to examine the distribution patterns of seawater intrusion and fluoride concentration and the impact of seawater intrusion on the fluoride concentration. The results indicate that seawater intrusion significantly influences the groundwater evolution process in the study areas. The groundwater in Laizhou Bay was affected by brine, and the groundwater in Tianjin and Jiangsu was affected by seawater with a mixing ratio lower than 40% and 20%, respectively. And the fluoride concentration in groundwater from Tianjin, Laizhou Bay, and Jiangsu generally exceeded 1 mg/L, with the average of 2.3 mg/L, 24.9 mg/L, and 34.6 mg/L, respectively. Both the degree of seawater intrusion and the fluoride concentration exhibit a consistent pattern: Laizhou Bay > Tianjin > Jiangsu. Cl- concentration in groundwater varies positively with the F- concentration (y = 0.66x - 1.31). Moreover, the spatial distribution of areas with high-fluoride groundwater mirrors that of seawater intrusion. The high-fluoride groundwater varies spatially and is related to the degree, stage, and type of seawater intrusion. In other words, when seawater intrusion intensifies more or groundwater in the freshwater renewal phase with higher Na+/Ca2+ or the presence of paleo-seawater intrusion with higher fluoride concentration of brine, the concentration of fluoride in groundwater is higher. As seawater intrusion intensifies, the high-fluoride groundwater in the study areas generally poses a higher health risk to human. These findings enhance our comprehension of the mechanisms underpinning high-fluoride groundwater in coastal regions and the environmental ramifications of seawater intrusion.

Hydrochemical characteristics and quality assessment of groundwater in Guangxi coastal areas, China.

Groundwater is a main source of water supply in Guangxi Province, China. The urbanization expansion and ocean dynamic may change the groundwater quality, which is an important issue due to its effects on human health. In this paper, the influence of seawater intrusion and anthropogenic activity on the Guangxi coastal aquatic environment was assessed by geochemical and multivariate statistical methods. The result indicated that the chemical composition of groundwater in the study area is obviously associated with seawater and the main groundwater types were Ca·Na-Cl, Ca·Na-HCO3, and Ca-HCO3·Cl. The groundwater evolution path from land to sea in Guangxi is Ca-HCO3 â†’ Na·Mg-Cl. The origin of salts in the study area is mainly controlled by mineral weathering, the hydrogen and oxygen isotopes contents point to the aqueous source of atmospheric precipitation. According to the results of PCA, seawater intrusion and pollution caused by human activities play an increasingly important role in the evolution of groundwater characteristics. Seawater intrusion is the main factor for the increase of groundwater salinity in Guangxi, while domestic sewage, industrial waste, fertilizers, and pesticides may contribute to the nitrate pollution of groundwater, especially in Beihai. The degree of groundwater nitrate pollution is as follows: Fangchenggang < Qinzhou < Beihai, which is associated with the degree of urbanization in the coastal area. Finally, the results of the water quality index (WQI) assessment show that 82.8 % of the samples were classified as excellent, while there is still a need to be vigilant about groundwater pollution caused by seawater intrusion and groundwater pollution. The results will be valuable for sustainable groundwater resource management in Guangxi coastal zone.

Identifying the characteristics and potential risk of seawater intrusion for southern China by the SBM-DEA model.

Seawater intrusion (SWI) seriously affects the economic development of coastal areas in southern China, and understanding its mechanisms is the basis for effective control of SWI. Hydrogeochemical methods and slack-based measurement data envelopment analysis (SBM-DEA) are used to study the characteristics and potential risk of SWI in coastal cities of southern China. Types and distribution of SWI, coastal groundwater evolution, geological-geographic and economic threatens of SWI, potential SWI risk, and environmental management recommendations are explored. The results show that the intrusion areas of Zhejiang and Guangdong account for 94.1 % of the total intrusion area of southern China, and the intrusion degree in Zhejiang is the highest, followed by Guangdong and Fujian. SWI is prone to occur on the sandy and silty coasts of the plain area of southern China; it accelerates the groundwater evolution speed and shortens the evolution path. SBM-DEA can be well applied to evaluate the potential risk of SWI events, and the results indicate a noticeable difference in the environmental performance level of coastal cities in southern China. The low environmental performance level (<0.3) and severe SWI of Taizhou and Zhanjiang indicate that SWI gradually worsens with economic development. In contrast, the high environmental performance level (>0.7) and low SWI of Wenzhou, Fuzhou, Quanzhou, Shantou, and Beihai indicate that the potential risk of SWI is gradually decreasing. Moreover, this study confirms that the environmental Kuznets curve (EKC) phenomenon exists in SWI events for southern China, and SWI-EKC indicates that the urban development of south China is approaching maturity. The specific case of SWI and EPL in coastal cities of south China jointly indicates that optimizing industrial structure, implementing a resources management policy, and improving citizens' environmental awareness are fundamental measures to resolve the contradiction between economic development and environmental problems.

Vitreoscilla Hemoglobin Improves Sophorolipid Production in Starmerella Bombicola O-13-1 Under Oxygen Limited Conditions.

Sophorolipids (SLs) are homologous microbial secondary metabolites produced by Starmerella bombicola and have been widely applied in many industrial fields. The biosynthesis of SLs is a highly aerobic process and is often limited by low dissolved oxygen (DO) levels. In this study, the Vitreoscilla hemoglobin (VHb) gene was transformed into S. bombicola O-13-1 by homologous recombination to alleviate oxygen limitation. VHb expression improved the intracellular oxygen utilization efficiency under either oxygen-rich or oxygen-limited conditions. In shake flask culture, the production of SLs was higher in the recombinant (VHb+) strain than in the wild-type (VHb-) strain, while the oxygen uptake rate of the recombinant (VHb+) strain was significantly lower than that of the wild-type (VHb-) strain. In a 5 L bioreactor, the production of SLs did not increase significantly, but the DO level in the fermentation broth of the VHb+ strain was 21.8% higher than that of VHb- strain under oxygen-rich conditions. Compared to wide-type strains (VHb-), VHb expression enhanced SLs production by 25.1% in the recombinants (VHb+) under oxygen-limited conditions. In addition, VHb expression raised the transcription levels of key genes involved in the electron transfer chain (NDH, SDH, COX), TCA cycle (CS, ICD, KDG1) and SL synthesis (CYP52M1 and UGTA1) in the recombinant (VHb+) strains. VHb expression in S. bombicola could enhance SLs biosynthesis and intracellular oxygen utilization efficiency by increasing ATP production and cellular respiration. Our findings highlight the potential use of VHb to improve the oxygen utilization efficiency of S. bombicola in the industrial-scale production of SLs using industrial and agricultural by-products like molasses and waste oil as fermentation feedstock.

Hydrogeochemical processes and suitability assessment of groundwater in the Jiaodong Peninsula, China.

Groundwater is the primary source of water for domestic use and agricultural irrigation in Jiaodong Peninsula. This study collected 80 groundwater samples from Jiaodong Peninsula to characterize groundwater hydrogeochemical processes and the suitability of groundwater for domestic use and agricultural irrigation. The groundwater of Jiaodong Peninsula was categorized as slightly alkaline freshwater, with a Piper diagram classifying most samples as SO4·Cl-Ca·Mg and HCO3-Ca·Mg types. Major ions were Ca2+, Na+, SO42-, and HCO3-. The major processes driving the hydrochemistry of groundwater were identified as water-rock interactions as well as evaporation. The dissolution of silicate and cation exchange were the predominant hydrogeochemical processes responsible for groundwater chemistry. Four water samples showed seawater intrusion and some indicated pollution from anthropogenic activities such as industry, agriculture, and domestic sewage discharge. Overall, it was found that groundwater in most areas of Jiaodong Peninsula is suitable for domestic use and agricultural irrigation.

Evolution analysis and environmental management of intruded aquifers of the Dagu River Basin of China.

The seawater intrusion in the Dagu River Basin, China, has attracted intensive attention from the government and scholars. Increasing data have become available with the development of data acquisition technology. This situation brings unprecedented opportunities and challenges to the hydrochemical evolution analysis and improvement of seawater intrusion. The hydrochemical evolution process of groundwater is studied on the basis of our collected data in the Dagu River Basin by using mathematical statistics, end-element mixing, Durov, and Gibbs. The negative influencing factors of the groundwater environment are determined. Results show that the groundwater on the north side of the cutoff wall is mainly affected by residual saltwater, sulfuric acid leakage, and NO- 3 pollution. The groundwater on the south side of the cutoff wall is seriously affected by seawater invasion, followed by NO- 3 pollution. Meanwhile, the groundwater on the west bank of the Dagu River Basin is mainly affected by NO- 3 pollution. The groundwater on the north side of the cutoff wall must be discharged on a large scale for its improvement. Meanwhile, unpolluted water is recharged to renew the groundwater resources. Groundwater exploitation should be reduced, and the exploitation area should be dispersed to mitigate seawater intrusion and increase the recharge of the groundwater resources. NO- 3 pollution mainly comes from the sowing of chemical fertilizers and pesticides and domestic waste. Therefore, we should reduce the use of pesticides and fertilizers to control the generation, storage, and treatment of domestic pollutants strictly.

Effect of aminoglycosides on the pathogenic characteristics of microbiology.

Infections caused by pathogen remain to be one of the most important global health issues, and scientists are devoting themselves to seeking effective treatments. Aminoglycoside antibiotics are one kind of widely used antibiotics because of the good efficiency and broad antimicrobial-spectrum. However, it causes some unexpected effects on the pathogenic characteristics of microbiology during the treatment, such as drug resistance and biofilm promotion. Drug resistance is partly due to antibiotics abuse. Simultaneously, aminoglycoside is documented to make divergent effects on biofilm based on their concentrations. Here, we review the mechanism of drug resistance caused by long-term use of aminoglycoside antibiotics, the effects of antibiotic concentration on biofilm formation and the negative effects on intestinal flora to provide theoretical supports for rational use of antibiotics.

Plio-Pleistocene evolution of Bohai Basin (East Asia): demise of Bohai Paleolake and transition to marine environment.

The Bohai Basin was transformed to an inner shelf sea hundreds of thousands years ago. This youngest land-sea transition participated in the significant modification of the distribution of fresh water, sediment fluxes and climate in East Asia, and played an important role in the origin of the Asian marginal seas. Here we present the results of a magnetostratigraphic investigation and propose a conceptual model for the land-sea transition. Our findings indicate that the transition probably started several million years ago, from a fluvial system during the late Miocene and early Pliocene, to a lacustrine environment between the late Pliocene and Middle Pleistocene, and finally to a marine system in the late Pleistocene. Comparison of our results with previous research suggests that the Bohai Paleolake was initiated from the late Pliocene, was fully developed prior to ~1.0 Ma, and terminated around the late Middle Pleistocene. The Miaodao Islands formed the eastern "barrier" of the basin and since the Pliocene or earlier they played a significant role in blocking the lake water and sediments. They deformed from ~1.0 Ma, subsided significantly at ~0.3 Ma and completely by ~0.1 Ma, resulting in the maturation of the basin as an inner shelf sea.

A novel protocol for covalent immobilization of thionine on glassy carbon electrode and its application in hydrogen peroxide biosensor.

A novel protocol for effectively covalent immobilization of thionine (Th) was proposed, which was based on Schiff-base reaction between -NH(2) of Th and -COH which was in situ generated on glassy carbon electrode (GCE) via simple potentiostatic activation in diluted nitric acid. GCE pretreated by potentiostatic activation possessed CHO-riched surface and microporous structure with high distribution density of electron transfer sites, and thus it became a good candidate for effective immobilization of Th through imine bond with high stability. The application of the resulting Th modified electrode in hydrogen peroxide biosensor was also investigated and it exhibited rapid response to H(2)O(2) within 3s. The linear calibration ranged from 5.0x10(-7) to 5.8x10(-3)M with a detection limit of 1.0x10(-7)M. The effective immobilization of Th on potentiostatically activated GCE surface has deep significance in mediator immobilization, on which further researches based are under way.