scholarly journals Formation and remediation simulation of an in-situ reactive zone with nanoiron for a nitrobenzene-contaminated aquifer

2018 ◽  
Vol 18 (6) ◽  
pp. 2071-2080
Author(s):  
Li Hui ◽  
Zhang Xue-qing
Keyword(s):  
Fine Sand ◽  
Coarse Sand ◽  
Water Yield ◽  
Permeability Change ◽  
Contaminated Aquifer ◽  
Permeability Constant ◽  
Sand Box ◽  
Reactive Zone ◽  
The Media

Abstract A two-dimensional simulated sand box was built to investigate the formation and remediation of an in-situ reactive zone (IRZ) of nanoscale zero-valent iron (NZVI) for a nitrobenzene-contaminated aquifer, and the permeability change of the zone was calculated through the loss of waterhead. The experimental results demonstrated that the remediation area in coarse sand was obviously larger than that in fine sand. The nitrobenzene concentration reached a stable level of 87.24 and 170.24 mg/L in coarse and fine sand by 50 d and 40 d, respectively; after 60 d, the concentration of aniline as the reduction end-product of nitrobenzene was 97.02 and 49.40 mg/L, corresponding to a mean production rate of 40.1% and 20.8%, respectively. This indicated that a wider zone will be formed in the media with a larger size, which is beneficial for pollution remediation. The water yield of the aquifer declined by 13.8% and 11.9% in coarse and fine sand after 60 d, and the final permeability constant was 22.94 and 1.82 m/d (declining by 60.9% and 70.6%), respectively. The reactive zone remained stable and the injection of NZVI slurry could not cause any dramatic changes in the aquifer permeability.

scholarly journals Analysis of the LNAPL Migration Process in the Vadose Zone under Two Different Media Conditions

2021 ◽  
Vol 18 (21) ◽  
pp. 11073
Author(s):  
Rui Zuo ◽  
Xiao Zhao ◽  
Jie Yang ◽  
Minghao Pan ◽  
Zhenkun Xue ◽  
...  
Keyword(s):  
Vadose Zone ◽  
Natural Attenuation ◽  
Fine Sand ◽  
Coarse Sand ◽  
Near Surface ◽  
Attenuation Rate ◽  
Order Of Magnitude ◽  
Medium Particle ◽  
The Media ◽  
Surface Leakage

This study focused on the processes of free infiltration, precipitation displacement, and natural attenuation of the LNAPL under the condition of near-surface leakage. Sandbox experiments were performed to explore the migration characteristics of LNAPL in the vadose zone with two media structures and the influences of the soil interface on the migration of LNAPL. The results indicate that the vertical migration velocity of the LNAPL infiltration front in medium and coarse sand was 1 order of magnitude higher than that in fine sand and that the LNAPL accumulated at the coarse–fine interface, which acted as the capillary barrier. Displacement of precipitation for LNAPL had little relationship with rainfall intensity and was obviously affected by medium particle size, where coarse sand (40.78%) > medium sand (20.5%) > fine sand (10%). The natural attenuation rate of the LNAPL in the vadose zone was related to the water content of the media; the natural attenuation rate of fine sand was higher. This study simulated the process of the LNAPL leakage from the near surface into the layered heterogeneous stratum, improved the understanding of the migration of the LNAPL under different stratum conditions, and can provide support for the treatment of LNAPL leakage events in the actual site.

scholarly journals Study On Critical Temperatures For Naphthalene And Chlorobenzene Removal During In Situ Steam Injection Remediation

2021 ◽  
Author(s):  
Ru xue Liu ◽  
Xinru Yang ◽  
Yongsheng Zhao
Keyword(s):  
Critical Temperature ◽  
Organic Pollutants ◽  
Organic Contaminants ◽  
Fine Sand ◽  
Steam Injection ◽  
Coarse Sand ◽  
Critical Temperatures ◽  
Factors Affecting ◽  
Remediation Process

Abstract Steam injection is an effective technique for the in situ remediation of volatile and semi-volatile organic contaminants. In this study, the influence of temperature and media on the removal of organic pollutants, such as naphthalene and chlorobenzene, was investigated in the remediation process through batch and remediation experiments, and the solid, liquid, and gaseous phase migration and transformation of organic pollutants during remediation were evaluated. The results demonstrated that the temperature significantly influenced the removal of organic pollutants. It was found that the critical temperatures for naphthalene and chlorobenzene were 50°C and 30°C, respectively. When the temperature was higher than the critical temperature, the final removal rates of naphthalene and chlorobenzene reached over 94% and 96%, respectively. The remediation area of chlorobenzene determined according to the critical temperature has a good result; the error compared with the actual remediation area in both coarse sand and fine sand was approximately 8.7%. In the simulation tank, the temperature changes can be divided into three stages: the ambient temperature stage, the temperature rapid rise stage, and the stable stage. Moreover, we found that the remediation effect of aquifers is not only related to temperature, but also to the location of the SVE well (soil vapour extraction). These findings reveal the main factors affecting the application of hot steam technology and the relationship between the temperature field and contamination field in the remediation process.

Sediment-rejection mechanisms of 42 species of Australian scleractinian corals

1992 ◽  
Vol 43 (4) ◽  
pp. 683 ◽  
Author(s):  
MG Stafford-Smith ◽  
RFG Ormond
Keyword(s):  
Tissue Expansion ◽  
Fine Sand ◽  
Coarse Sand ◽  
Energy Budgets ◽  
Sediment Size ◽  
Sediment Loads ◽  
Organic Sediment ◽  
Acropora Hyacinthus ◽  
Neutrally Buoyant

Mechanisms of sediment rejection by 42 species of Scleractinia from 31 genera, all with wide Indo-Pacific distributions, were investigated in situ and in the laboratory at Lizard Island, northern Great Barrier Reef. Rejection mechanisms of flat tissues (generally six replicates plus controls) were studied in response to a single rapid influx of 50 mg cm-2 of 70/30% calcium carbonate/quartz sediment of each of four particle sizes: silt (<63 pm), fine sand (63-250 μm), coarse sand (500 μrn to 1 mm), and granules (1-3 mm). Additional observations were made of responses to variations in sediment loads (to a maximum of 1000 mg cm-2) , to individual sediment particles, and to less-dense organic sediment and food, as well as of the effects of tissue angles, colony morphology, and in situ environmental conditions. Ciliary currents, tissue expansion, and mucus entanglement occur in all of the species studied. Direct tentacle manipulation and pulsed partial contraction of the polyp or coenosarc also occur but were not observed in all species. Mesenteries may play a subsidiary or incidental role. Active-rejection mechanisms are consistent within species and, with the principal exception of some Faviidae species, are similar for the congeneric species studied. Species are categorized according to their observed active-rejection capability. This capability is positively correlated with calice size: all species with large calices (> 10 mm in diameter) are capable of rejecting influxes of up to at least 50 mg cm-2 of the tested sediment sizes with comparative ease; those species with small calices (<2.5 mm in diameter), particularly the two Porites species and the three Montipora species, are poor active rejectors; and other species, notably Acropora hyacinthus and Pocillopora darnicornis, though having some active-rejection capability, exhibit morphologies that make active rejection mostly redundant. Species with calices between 2.5 and 10 mm in diameter show more variation, but all very active rejectors in this size class have strong ciliary mechanisms. There are differences in the area of a colony involved in the rejection of sediment influxes, depending on sediment size and density. Rejection of heavy influxes of all sediment sizes is principally restricted to flat or concave surfaces, whereas individual particles of silt and fine sand as well as light influxes of silt and almost neutrally buoyant particles of larger sizes frequently require active rejection from strongly inclined, and even near-vertical, surfaces. The significance of these findings in terms of energy budgets is discussed.

On-site and in situ bioremediation of wood-preservative contaminated groundwater

2000 ◽  
Vol 42 (5-6) ◽  
pp. 371-376 ◽  
Author(s):  
J.A. Puhakka ◽  
K.T. Järvinen ◽  
J.H. Langwaldt ◽  
E.S. Melin ◽  
M.K. Männistö ◽  
...  
Keyword(s):  
Iron Oxidation ◽  
Wood Preservative ◽  
Pilot Scale ◽  
High Rate ◽  
Contaminated Groundwater ◽  
Groundwater Temperature ◽  
In Situ Bioremediation ◽  
Contaminated Aquifer ◽  
Fluidized Bed Process

This paper reviews ten years of research on on-site and in situ bioremediation of chlorophenol contaminated groundwater. Laboratory experiments on the development of a high-rate, fluidized-bed process resulted in a full-scale, pump-and-treat application which has operated for several years. The system operates at ambient groundwater temperature of 7 to 9°C at 2.7 d hydraulic retention time and chlorophenol removal efficiencies of 98.5 to 99.9%. The microbial ecology studies of the contaminated aquifer revealed a diverse chlorophenol-degrading community. In situ biodegradation of chlorophenols is controlled by oxygen availability, only. Laboratory and pilot-scale experiments showed the potential for in situ aquifer bioremediation with iron oxidation and precipitation as a potential problem.

Remediation of PCE-contaminated aquifer by an in situ two-layer biobarrier: laboratory batch and column studies

2003 ◽  
Vol 37 (1) ◽  
pp. 27-38 ◽  
Author(s):  
C.M Kao ◽  
S.C Chen ◽  
J.Y Wang ◽  
Y.L Chen ◽  
S.Z Lee
Keyword(s):  
Column Studies ◽  
Contaminated Aquifer

scholarly journals Degradation Mechanism of Porous Metal-Organic Frameworks by In Situ Atomic Force Microscopy

Nanomaterials ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 722
Author(s):  
Ioanna Christodoulou ◽  
Tom Bourguignon ◽  
Xue Li ◽  
Gilles Patriarche ◽  
Christian Serre ◽  
...  
Keyword(s):  
Drug Delivery ◽  
Degradation Mechanism ◽  
Metal Organic Frameworks ◽  
Porous Metal ◽  
Force Microscopy ◽  
Atomic Force ◽  
Metal Organic ◽  
The Media ◽  
Ph Conditions

In recent years, Metal-Organic Frameworks (MOFs) have attracted a growing interest for biomedical applications. The design of MOFs should take into consideration the subtle balance between stability and biodegradability. However, only few studies have focused on the MOFs’ stability in physiological media and their degradation mechanism. Here, we investigate the degradation of mesoporous iron (III) carboxylate MOFs, which are among the most employed MOFs for drug delivery, by a set of complementary methods. In situ AFM allowed monitoring with nanoscale resolution the morphological, dimensional, and mechanical properties of a series of MOFs in phosphate buffer saline and in real time. Depending on the synthetic route, the external surface presented either well-defined crystalline planes or initial defects, which influenced the degradation mechanism of the particles. Moreover, MOF stability was investigated under different pH conditions, from acidic to neutral. Interestingly, despite pronounced erosion, especially at neutral pH, the dimensions of the crystals were unchanged. It was revealed that the external surfaces of MOF crystals rapidly respond to in situ changes of the composition of the media they are in contact with. These observations are of a crucial importance for the design of nanosized MOFs for drug delivery applications.

Removal of heavy metal from soil and groundwater by in-situ electrokinetic remediation

2000 ◽  
Vol 42 (7-8) ◽  
pp. 335-343 ◽  
Author(s):  
S. Shiba ◽  
S. Hino ◽  
Y. Hirata ◽  
T. Seno
Keyword(s):  
Heavy Metals ◽  
Heavy Metal ◽  
Electric Potential ◽  
Potential Gradient ◽  
Electrokinetic Remediation ◽  
Contaminated Aquifer ◽  
Physico Chemical ◽  
Operational Variables ◽  
Mass Transport Process

The operational variables of electrokinetic remediation have not been cleared yet, because this method is relatively new and is an innovative technique in the aquifer remediation. In order to investigate the operational variables of the electrokinetic remediation, a mathematical model has been constructed based on the physico chemical mass transport process of heavy metals in pore water of contaminated aquifer. The transport of the heavy metals is driven not only by the hydraulic flow due to the injection of the purge water but also by the electromigration due to the application of the electric potential gradient. The electric potential between anode and cathode is the important operational variable for the electrokinetic remediation. From the numerical simulations with use of this model it is confirmed that the remediation starts from the up stream anode and gradually the heavy metal is transported to the down stream cathode and drawn out through the purge water.

scholarly journals Marine substrate response from the analysis of seismic attributes in CHIRP sub-bottom profiles

2017 ◽  
Vol 65 (3) ◽  
pp. 332-345 ◽  
Author(s):  
Larissa Felicidade Werkhauser Demarco ◽  
Antonio Henrique da Fontoura Klein ◽  
Jorge Antonio Guimarães de Souza
Keyword(s):  
Grain Size ◽  
Seismic Reflection ◽  
Ground Truth ◽  
Fine Sand ◽  
Seismic Attributes ◽  
Coarse Sand ◽  
Unconsolidated Sediments ◽  
Shallow Gas ◽  
Size Classes ◽  
Seismic Reflection Profiles

Abstract This paper presents an evaluation of the response of seismic reflection attributes in different types of marine substrate (rock, shallow gas, sediments) using seafloor samples for ground-truth statistical comparisons. The data analyzed include seismic reflection profiles collected using two CHIRP subbottom profilers (Edgetech Model 3100 SB-216S), with frequency ranging between 2 and 16 kHz, and a number (38) of sediment samples collected from the seafloor. The statistical method used to discriminate between different substratum responses was the non-parametric Kruskal-Wallis analysis, carried out in two steps: 1) comparison of Seismic Attributes between different marine substrates (unconsolidated sediments, rock and shallow gas); 2) comparison of Seismic Attributes between different sediment classes in seafloors characterized by unconsolidated sediments (subdivided according to sorting). These analyses suggest that amplitude-related attributes were effective in discriminating between sediment and gassy/rocky substratum, but did not differentiate between rocks and shallow gas. On the other hand, the Instantaneous Frequency attribute was effective in differentiating sediments, rocks and shallow gas, with sediment showing higher frequency range, rock an intermediate range, and shallow gas the lowest response. Regarding grain-size classes and sorting, statistical analysis discriminated between two distinct groups of samples, the SVFS (silt and very fine sand) and the SFMC (fine, medium and coarse sand) groups. Using a Spearman coefficient, it was found that the Instantaneous Amplitude was more efficient in distinguishing between the two groups. None of the attributes was able to distinguish between the closest grain size classes such as those of silt and very fine sand.

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