Influences of microbial communities on groundwater component concentrations during managed artificial recharge

Managed aquifer recharge is one of the most popular methods for dealing with local water shortage issues, and the bacterial community could be a vital factor influencing groundwater quality during this process. In this study, analysis of variations in groundwater components during artificial recharge revealed three stages at a text site in China. During stage I, total iron and dissolved organic carbon levels are stable basically, dissolved oxygen and SO₄ ^2? levels have rising trends, NO₃ ^? curve varied not obviously. Variation curves show increases in dissolved oxygen, NO₃ ^?, SO₄ ^2? and stabilization in dissolved organic carbon and total iron at stage II. During stage III, dissolved oxygen and NO₃ ^? have rising trends, dissolved organic carbon, total iron, and SO₄ ^2? keep stable. At 25 and 70 days the Simpson and Shannon–Wiener indices show that microbial community richness and population diversity underwent a gradual dynamic change after recharge water arrived. Correlation analysis shows that the Simpson index was mainly affected by dissolved oxygen and NO₃ ^?. PCR-DGGE confirmed these findings. Overall, the results revealed that the main bacterial communities reduce total nitrogen, total phosphorous, and chemical oxygen demand, which corresponded to the calculated correlation index.     

Three-dimensional numerical modeling of land subsidence in Shanghai,China

Shanghai, in China, has experienced two periods of rapid land subsidence mainly caused by groundwater exploitation related to economic and population growth. The first period occurred during 1956–1965 and was characterized by an average land subsidence rate of 83 mm/yr, and the second period occurred during 1990–1998 with an average subsidence rate of 16 mm/yr. Owing to the establishment of monitoring networks for groundwater levels and land subsidence, a valuable dataset has been collected since the 1960s and used to develop regional land subsidence models applied to manage groundwater resources and mitigate land subsidence. The previous geomechanical modeling approaches to simulate land subsidence were based on one-dimensional (1D) vertical stress and deformation. In this study, a numerical model of land subsidence is developed to simulate explicitly coupled three-dimensional (3D) groundwater flow and 3D aquifer-system displacements in downtown Shanghai from 30 December 1979 to 30 December 1995. The model is calibrated using piezometric, geodetic-leveling, and borehole extensometer measurements made during the 16-year simulation period. The 3D model satisfactorily reproduces the measured piezometric and deformation observations. For the first time, the capability exists to provide some preliminary estimations on the horizontal displacement field associated with the well-known land subsidence in Shanghai and for which no measurements are available. The simulated horizontal displacements peak at 11 mm, i.e. less than 10 % of the simulated maximum land subsidence, and seems too small to seriously damage infrastructure such as the subways (metro lines) in the center area of Shanghai.     

Identification and characterization of a DnaJ gene from red alga <Emphasis Type="Italic">Pyropia yezoensis</Emphasis> (Bangiales,Rhodophyta)

Members of the DnaJ family are proteins that play a pivotal role in various cellular processes, such as protein folding, protein transport and cellular responses to stress. In the present study, we identified and characterized the full-length DnaJ cDNA sequence from expressed sequence tags of Pyropia yezoensis (PyDnaJ) via rapid identification of cDNA ends. This cDNA encoded a protein of 429 amino acids, which shared high sequence similarity with other identified DnaJ proteins, such as a heat shock protein 40/DnaJ from Pyropia haitanensis. The relative mRNA expression level of PyDnaJ was investigated using real-time PCR to determine its specific expression during the algal life cycle and during desiccation. The relative mRNA expression level in sporophytes was higher than that in gametophytes and significantly increased during the whole desiccation process. These results indicate that PyDnaJ is an authentic member of the DnaJ family in plants and red algae and might play a pivotal role in mitigating damage to P. yezoensis during desiccation.     

Optimization of four types of antimicrobial agents to increase the inhibitory ability of marine <Emphasis Type="Italic">Arthrobacter oxydans</Emphasis> KQ11 dextranase mouthwash

We adopted the response surface methodology using single factor and orthogonal experiments to optimize four types of antimicrobial agents that could inhibit biofilm formation by Streptococcus mutans, which is commonly found in the human oral cavity and causes tooth decay. The objective was to improve the function of marine Arthrobacter oxydans KQ11 dextranase mouthwash (designed and developed by our laboratory). The experiment was conducted in a three-level, four-variable central composite design to determine the best combination of ZnSO₄, lysozyme, citric acid and chitosan. The optimized antibacterial agents were 2.16 g/L ZnSO₄, 14 g/L lysozyme, 4.5 g/L citric acid and 5 g/L chitosan. The biofilm formation inhibition reached 84.49%. In addition, microscopic observation of the biofilm was performed using scanning electron microscopy and confocal laser scanning microscopy. The optimized formula was tested in marine dextranase Arthrobacter oxydans KQ11 mouthwash and enhanced the inhibition of S. mutans. This work may be promoted for the design and development of future marine dextranase oral care products.     

Interspecific competition and allelopathic interaction between <Emphasis Type="Italic">Karenia mikimotoi</Emphasis> and <Emphasis Type="Italic">Dunaliella salina</Emphasis> in laboratory culture

Algal allelopathy is a manifold ecological/physiological phenomenon that is focused on chemical interactions and autotoxicity. We investigated the allelopathic interactions between Karenia mikimotoi and Dunaliella salina in laboratory cultures based on diff erent temperature (15°C, 20°C, and 25°C) and lighting (40, 80, and 160 μmol/(m²·s)) conditions. The growth of D. salina in bi-algae culture (1:1 size/density) was significantly restrained. The results of cell-free filtrate culture indicate that direct cell-tocell contact was not necessary in interspecific competition. Further experimental results demonstrated that allelochemicals released from K. mikimotoi were markedly influenced by both temperature (P =0.013) and irradiance (P =0.003), resulting in diff erent growth characteristics of D. salina in filtrate mediums. Compared with the plateau period, K. mikimotoi exudates in the exponential phase had a stronger short-term inhibition effect on D. salina in normal conditions. A clear concentration-dependent relationship was observed in the effect of allelochemicals released from K. mikimotoi with low-promoting and high-repressing effects on D. Salina in a short time-scale. In addition, allelopathic substances remain stable and effective under high temperature and pressure stress. Many flocculent sediments adhering with D. salina cells were observed in all filtrate mediums, while the quantity and color depended on the original culture conditions.     

成都经济区不同地貌景观区土壤有机碳分布特征及储量估算

利用四川省成都经济区多目标区域地球化学调查获得的土壤有机碳含量数据,探讨了成都经济区不同地貌景观区土壤有机碳的分布特征。山区表层土壤有机碳含量(SOC)最高(22 g/kg左右),较平原区、丘陵区高一倍以上,丘陵区最低(9.49 g/kg)。成都平原区和东部丘陵区深层土壤碳含量相差不大,且均低于研究区深层土壤碳含量均值(6.99 g/kg)。利用指数模型对单位土壤平均碳量(USCATOC)、有机碳储量(USCATOC,h)、有机碳丰度指数(R)进行了估算。结果表明:各地貌单元土壤碳含量、单位土壤平均碳量、有机碳储量、有机碳丰度指数(R)分布具有山区高于平原区、丘陵区最低的一致性特征。龙门山区、西南山区面积约占全区的42%,土壤有机碳储量约占全区的59%;成都平原区、丘陵区面积占58%,土壤有机碳储量约占全区的41%。单位土壤平均碳量、有机碳储量在不同地貌单元中分布的差异主要与不同地貌单元的土壤有机碳含量有关,此外还可能与成土母质、植被发育情况、土地利用方式有关。     

塔里木盆地寒武纪构造演化研究

对塔里木盆地寒武纪早、中、晚3个时期的古水深、沉积速率、构造沉降速率和拉伸系数计算结果表明,塔里木盆地在早寒武世为深度裂陷阶段,中寒武世为裂陷迁移阶段,晚寒武世为台内裂陷阶段,早寒武世与中-晚寒武世的构造差异性十分明显。早寒武世伸展引起的裂陷作用发生在塔东地区,伸展促使该区构造沉降速率远远大于台地相区,形成半深海盆地相环境。中-晚寒武世伸展向台地内部迁移,使台地内部的构造沉降速率远大于盆地相区,而台地内部较高构造沉降速率被更高的沉积速率所补偿,使得这里始终未能出现地貌上的凹地。     

根据试桩成果反分析灌注桩的设计参数

利用钻孔灌注桩试桩报告中的静载荷试验原始数据和地层资料,结合规范,利用反分析的方法确定各地层的极限端阻力标准值qpk和极限侧阻力标准值qsik。可将试桩成果推广应用到场地附近任意桩长和桩径的桩型设计中。     

冰冻圈变化的可预测性、不可逆性和深度不确定性

IPCC第六次评估报告(AR6)第一工作组报告对气候系统各要素的可预测性(predictability)、不可逆性(irreversibility)和深度不确定性(deep uncertainty)给出了新认识.文中基于此对全球冰冻圈变化的上述三方面加以总结和归纳.总体来看,无论何种排放情景,半球和全球尺度上冰冻圈各要...