排序方式: 共有31条查询结果,搜索用时 343 毫秒
21.
John Rapaglia Christian Ferrarin Pere Masqué 《Journal of environmental radioactivity》2010,101(7):571-581
The four naturally-occurring isotopes of radium were coupled with a previously evaluated hydrodynamic model to determine the apparent age of surface waters and to quantify submarine groundwater discharge (SGD) into the Venice Lagoon, Italy.Mean apparent age of water in the Venice Lagoon was calculated using the ratio of 224Ra to 228Ra determined from 30 monitoring stations and a mean pore water endmember. Average apparent age was calculated to be 6.0 d using Ra ratios. This calculated age was very similar to average residence time calculated for the same period using a hydrodynamic model (5.8 d).A mass balance of Ra was accomplished by quantifying each of the sources and sinks of Ra in the lagoon, with the unknown variable being attributed to SGD. Total SGD were calculated to be 4.1 ± 1.5, 3.8 ± 0.7, 3.0 ± 1.3, and 3.5 ± 1.0 × 1010 L d−1 for 223,224,226, 228Ra, respectively, which are an order of magnitude larger than total mean fluvial discharge into the Venice Lagoon (3.1 × 109 L d−1). The SGD as a source of nutrients in the Venice Lagoon is also discussed and, though significant to the nutrient budget, is likely to be less important as the dominant control on SGD is recirculated seawater rather than freshwater. 相似文献
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湖泊水流运动和污染物的迁移路径对湖泊水质起着关键作用。采用水动力和粒子示踪耦合模型,并结合野外粒子示踪实验来调查鄱阳湖洪水季节空间水流运动和污染物迁移路径。模拟结果显示,流域五河点源入湖污染物和湖区空间面源分布污染物均会沿着不同方向迅速进入湖泊主河道,在快速水流推动下逐渐向北部湖区迁移,但部分污染物因东北部湖湾区存在顺时针方向环流而发生长时间滞留和富集。野外粒子示踪实验同样表明,东北部湖湾区污染物迁移路径随着该湖区水流运动表现得复杂多变,除了可以明显观察到顺时针方向的污染物运动,还可以发现污染物向湖岸边界和湖汊迁移,最终滞留在东北部湖湾区,而康山湖区污染物在快速水流推动下主要沿主河道向西北主湖区迁移,未发现污染物进入东北部湖湾区的迹象。鄱阳湖洪水季节水流运动和污染物迁移路径具有枯水期水流-污染物传输特性。模拟得出鄱阳湖洪水期的平均换水周期约89 d,表明其可能需要近3个月时间才能彻底完成一次换水。研究成果可为大型通江湖泊"江湖关系变化"研究提供参考,对保护"一湖清水"、保障长江中下游水环境安全具有重要现实意义。 相似文献
23.
Recharging from open-surface water resources is investigated as a method for remediation of over-produced and contaminated
aquifers. The hydraulic and contaminant modeling using the Modflow-2000 and MT3DMS simulation software are resorted for evaluation
of the available options. Methodology is developed and illustrated for reviewing the alternative remediation approaches for
optimal selection of the best remediation approach to aquifer recharging from surface waters. The effectiveness of the present
systematic approach is demonstrated by identifying the best choice among the multifunctional artificial recharge options available
for the Great Forest Park in Debrecen, Hungary. 相似文献
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介绍了水力空化作用机理,研究了水力空化作用对褐煤水煤浆粘度的影响,探讨了空化后浆体内存在气泡的形态及影响关系。试验结果表明:水力空化处理后的水煤浆浆体流动性变好,水煤浆的粘度特性已由假塑性流体变成了类似牛顿流体;速度梯度为100 s-1时的粘度指标由320 mPa·s提高到340 mPa·s,速度梯度为30 s-1时的粘度指标由420 mPa·s提高到850 mPa·s,30μm以下的细粒级含量明显高于空化前粒级的含量;水力空化作用在水煤浆中引入了大量不易消失的圆形微细气泡,气泡的占位作用提高了水煤浆粘度和稳定性,微细气泡的布朗运动破坏了颗粒之间的静电力吸附,圆形微细气泡成为水煤浆浆体流动过程中的润滑剂并改善水煤浆流变性能。 相似文献
27.
Anaerobic ammonium oxidation (Anammox) has become a promising method for biological nitrogen removal. However, this biotechnology application is always limited due to the low growth rate and biomass yield of Anammox bacteria. This study investigated the process of fast reactivation of an Anammox consortium idled for 2 years uia hydrodynamic stress control. The results showed that the Anammox system was efficiently and quickly reactivated by shortening of the hydraulic retention time (I-IRT) of the reactor from 12 to 6 hr within 68 days of operation. Moreover, at a 4-hr HRT with an influent total nitrogen loading rate of 1.2 kg N/(m3.day), the reactor maintained high biological performance with an ammonium removal loading rate of 0.52 kg N/(m3.day) and a nitrite removal rate of 0.59 kg N/(m3.day). In the reactivated Anammox reaction, the stoichiometric coefficients of NH4-N to NOE-N and NH4-N to NO4-N were 1:1.04± 0.08 and 1:0.31 ± 0.03, respectively. The specific Anammox activity and hydrazine oxidoreductase activity, both of which represent the degree of Anammox bacteria present, increased as the hydrodynamic stress increased and were maximally (125.38 ± 3.01 mg N/(g VSS.day) and 339.42 ± 6.83 μmol/(min.g VSS), respectively) at 4-hr HRT. Microbial response analysis showed that the dominant microbial community was obviously shifted and the dominance of Anammox bacteria was enhanced durinR the hydrodynamic selection. 相似文献
28.
Hailong Yin Yiyuan Lin Huijin Zhang Ruibin Wu Zuxin Xu 《Frontiers of Environmental Science & Engineering》2023,17(7):85
29.
Vera I. Slaveykova Konstantin Startchev 《Environmental pollution (Barking, Essex : 1987)》2009,157(12):3445-3450
The influence of pH, ionic strength, presence of humic or alginic acids, extracellular polymeric substances (EPS), or freshwater microalga Chlorella kesslerii on the stability and transformation of carboxyl-PEG-CdSe/ZnS core/shell quantum dots (QDs) in terms of number, hydrodynamic size and fluorescence of individual particles, was studied by fluorescence correlation spectroscopy. Obtained results demonstrated that QDs form stable dispersions at nanomolar concentrations under conditions typical for freshwaters. The presence of 5 or 15 mg C L−1 of humic acid or 50 mg C L−1 EPS did not significantly affect these parameters. In contrast, 5 or 50 mg C L−1 alginate at ionic strength of 10 mM shifted the hydrodynamic radius toward larger values, suggesting a possible capture of QDs by the linear alginate chains. The addition of microalga to the QD dispersions resulted in a slight reduction of the number of QDs and a significant decline in the fluorescence of individual QDs. 相似文献
30.
Polybrominated diphenyl ethers in sediments of the Daliao River Estuary, China: levels, distribution and their influencing factors 总被引:2,自引:0,他引:2
The concentrations, compositional profiles, possible sources of polybrominated diphenyl ethers (PBDEs) in sediments of the Daliao River Estuary as well as the factors influencing the distribution of PBDEs were investigated. The total concentrations of PBDEs ranged from 0.13 to 1.98 ng g−1 d.w. BDE209 was the dominating congener in all sediment samples, indicating the pollution of PBDEs in the Daliao River Estuary mainly came from the use of deca-BDE commercial mixtures. The intrusion of sea waters promoted the deposition of the colloid-associated PBDEs in the estuary. There were significantly negative correlations between PBDE concentration in sediment with pH value and salinity in the bottom water. The higher river flow in the flood season (summer) obviously accelerated the transport of PBDEs, and thereby increased the risk of PBDE contamination to the deep ocean. Moreover, a positive correlation between TOC and PBDE distributions was observed, suggesting that TOC regulated the distributions of PBDEs in sediments of Daliao River Estuary. 相似文献