scholarly journals CHROTRAN 1.0: A mathematical and computational model for in situ heavy metal remediation in heterogeneous aquifers

2017 ◽  
Author(s):  
Scott K. Hansen ◽  
Sachin Pandey ◽  
Satish Karra ◽  
Velimir V. Vesselinov
Keyword(s):  
Heavy Metal ◽  
Reactive Transport ◽  
Transport Model ◽  
Three Dimensional ◽  
Chemical Species ◽  
Heterogeneous Aquifers ◽  
Heavy Metal Remediation ◽  
Full Coupling ◽  
Abiotic Reduction

Abstract. Groundwater contamination by heavy metals is a critical environmental problem for which in situ remediation is frequently the only viable treatment option. For such interventions, a three-dimensional reactive transport model of relevant biogeochemical processes is invaluable. To this end, we developed a model, CHROTRAN, for in situ treatment, which includes full dynamics for five species: a heavy metal to be remediated, an electron donor, biomass, a nontoxic conservative bio-inhibitor, and a biocide. Direct abiotic reduction by donor-metal interaction as well as donor-driven biomass growth and bio-reduction are modeled, along with crucial processes such as donor sorption, bio-fouling and biomass death. Our software implementation handles heterogeneous flow fields, arbitrarily many chemical species and amendment injection points, and features full coupling between flow and reactive transport. We describe installation and usage and present two example simulations demonstrating its unique capabilities. One simulation suggests an unorthodox approach to remediation of Cr(VI) contamination.

scholarly journals CHROTRAN 1.0: A mathematical and computational model for in situ heavy metal remediation in heterogeneous aquifers

2017 ◽  
Vol 10 (12) ◽  
pp. 4525-4538 ◽  
Author(s):  
Scott K. Hansen ◽  
Sachin Pandey ◽  
Satish Karra ◽  
Velimir V. Vesselinov
Keyword(s):  
Heavy Metal ◽  
Reactive Transport ◽  
Transport Model ◽  
Chemical Species ◽  
Heterogeneous Aquifers ◽  
Heavy Metal Remediation ◽  
Full Coupling ◽  
Abiotic Reduction ◽  
Viable Treatment

Abstract. Groundwater contamination by heavy metals is a critical environmental problem for which in situ remediation is frequently the only viable treatment option. For such interventions, a multi-dimensional reactive transport model of relevant biogeochemical processes is invaluable. To this end, we developed a model, chrotran, for in situ treatment, which includes full dynamics for five species: a heavy metal to be remediated, an electron donor, biomass, a nontoxic conservative bio-inhibitor, and a biocide. Direct abiotic reduction by donor–metal interaction as well as donor-driven biomass growth and bio-reduction are modeled, along with crucial processes such as donor sorption, bio-fouling, and biomass death. Our software implementation handles heterogeneous flow fields, as well as arbitrarily many chemical species and amendment injection points, and features full coupling between flow and reactive transport. We describe installation and usage and present two example simulations demonstrating its unique capabilities. One simulation suggests an unorthodox approach to remediation of Cr(VI) contamination.

scholarly journals Coupling a genome-scale metabolic model with a reactive transport model to describe in situ uranium bioremediation

2009 ◽  
Vol 2 (2) ◽  
pp. 274-286 ◽  
Author(s):  
Timothy D. Scheibe ◽  
Radhakrishnan Mahadevan ◽  
Yilin Fang ◽  
Srinath Garg ◽  
Philip E. Long ◽  
...  
Keyword(s):  
Reactive Transport ◽  
Transport Model ◽  
Metabolic Model ◽  
Reactive Transport Model ◽  
A Genome ◽  
Genome Scale

scholarly journals A Methodology for Estimating the Parameters in Three-Dimensional Cohesive Sediment Transport Models by Assimilating In Situ Observations with the Adjoint Method

2017 ◽  
Vol 34 (7) ◽  
pp. 1469-1482 ◽  
Author(s):  
Daosheng Wang ◽  
Jicai Zhang ◽  
Ya Ping Wang ◽  
Xianqing Lv ◽  
Yang Yang ◽  
...  
Keyword(s):  
Sediment Transport ◽  
Adjoint Method ◽  
Settling Velocity ◽  
Transport Model ◽  
Three Dimensional ◽  
Temporal Variations ◽  
Cohesive Sediment ◽  
Cohesive Sediment Transport ◽  
Resuspension Rate

AbstractThe model parameters in the suspended cohesive sediment transport model are quite important for the accurate simulation of suspended sediment concentrations (SSCs). Based on a three-dimensional cohesive sediment transport model and its adjoint model, the in situ observed SSCs at four stations are assimilated to simulate the SSCs and to estimate the parameters in Hangzhou Bay in China. Numerical experimental results show that the adjoint method can efficiently improve the simulation results, which can benefit the prediction of SSCs. The time series of the modeled SSCs present a clear semidiurnal variation, in which the maximal SSCs occur during the flood tide and near the high water level due to the large current speeds. Sensitivity experiments prove that the estimated results of the settling velocity and resuspension rate, especially the temporal variations, are robust to the model settings. The temporal variations of the estimated settling velocity are negatively correlated with the tidal elevation. The main reason is that the mean size of the suspended sediments can be reduced during the flood tide, which consequently decreases the settling velocity according to Stokes’s law, and it is opposite in the ebb tide. The temporal variations of the estimated resuspension rate and the current speeds have a significantly positive correlation, which accords with the dynamics of the resuspension rate. The temporal variations of the settling velocity and resuspension rate are reasonable from the viewpoint of physics, indicating the adjoint method can be an effective tool for estimating the parameters in the sediment transport models.

scholarly journals On the ability of chemical transport models to simulate the vertical structure of the N<sub>2</sub>O, NO<sub>2</sub> and HNO<sub>3</sub> species in the mid-latitude stratosphere

2005 ◽  
Vol 5 (6) ◽  
pp. 12373-12401
Author(s):  
G. Berthet ◽  
N. Huret ◽  
F. Lefèvre ◽  
G. Moreau ◽  
C. Robert ◽  
...  
Keyword(s):  
Transport Model ◽  
Three Dimensional ◽  
Chemical Transport ◽  
Chemical Transport Model ◽  
Transport Models ◽  
One Dimensional ◽  
Chemical Transport Models ◽  
Dimensional Version ◽  
The Impact

Abstract. In this paper we study the impact of the modelling of N2O on the simulation of NO2 and HNO3 by comparing in situ vertical profiles measured at mid-latitudes with the results of the Reprobus 3-D CTM (Three-dimensional Chemical Transport Model) computed with the kinetic parameters from the JPL recommendation in 2002. The analysis of the measured in situ profile of N2O shows particular features indicating different air mass origins. The measured N2O, NO2 and HNO3 profiles are not satisfyingly reproduced by the CTM when computed using the current 6-hourly ECMWF operational analysis. Improving the simulation of N2O transport allows us to calculate quantities of NO2 and HNO3 in reasonable agreement with observations. This is achieved using 3-hourly winds obtained from ECMWF forecasts. The best agreement is obtained by constraining a one-dimensional version of the model with the observed N2O. This study shows that modelling the NOy partitioning with better accuracy relies at least on a correct simulation of N2O and thus of total NOy.

scholarly journals Assimilation of TES CO into a global CTM: first results

2006 ◽  
Vol 6 (6) ◽  
pp. 11727-11743 ◽  
Author(s):  
N. A. D. Richards ◽  
Q. Li ◽  
K. W. Bowman ◽  
J. R. Worden ◽  
S. S. Kulawik ◽  
...  
Keyword(s):  
Transport Model ◽  
Model Simulation ◽  
Three Dimensional ◽  
Model Bias ◽  
Upper Troposphere ◽  
First Results ◽  
Assimilation Scheme ◽  
Co Observations ◽  
Good Agreement

Abstract. We present results from the first assimilation of carbon monoxide (CO) observations from the Tropospheric Emission Spectrometer (TES) into a global three-dimensional (3-D) chemistry and transport model (CTM). A sequential sub-optimal Kalman filter assimilation scheme (Khattatov et al., 2000) was applied to assimilate TES CO profiles during November 2004 into the GEOS-Chem global 3-D CTM. The assimilation results were compared with MOPITT and MOZAIC observations. The assimilation significantly improves model simulation of CO in the middle to upper troposphere, where the MOPITT versus model bias was reduced by up to two-thirds. Assimilation results show higher levels of CO in the southern tropics, consistent with MOPITT observations. We find good agreement between the TES assimilated model estimates of CO and in situ measurements from the MOZAIC program, which shows a negative bias of up to 10 ppbv in middle and upper tropospheric TES CO. The results demonstrate how assimilation can be used for non-coincident validation of TES CO profile retrievals.

scholarly journals A three-dimensional reactive transport model for sediments, incorporating microniches

2008 ◽  
Vol 5 (3) ◽  
pp. 218 ◽  
Author(s):  
Łukasz Sochaczewski ◽  
Anthony Stockdale ◽  
William Davison ◽  
Wlodek Tych ◽  
Hao Zhang
Keyword(s):  
Reactive Transport ◽  
Manganese Oxides ◽  
Transport Model ◽  
Measurement Techniques ◽  
Three Dimensional ◽  
Sediment Surface ◽  
Concentration Gradients ◽  
Reactive Iron ◽  
Context Modelling ◽  
D Model

Environmental context. Modelling of discrete sites of diagenesis in sediments (microniches) has typically been performed in 1-D and has involved a limited set of components. Here we present a new 3-D model for microniches within a traditional vertical sequence of redox reactions, and show example modelled niches of a range of sizes, close to the sediment–water interface. Microniche processes may have implications for understanding trace metal diagenesis, via formation of sulfides. The model provides a quantitative framework for examining microniche data and concepts. Abstract. Most reactive transport models have represented sediments as one-dimensional (1-D) systems and have solely considered the development of vertical concentration gradients. However, application of recently developed microscale and 2-D measurement techniques have demonstrated more complicated solute structures in some sediments, including discrete localised sites of depleted oxygen, and elevated trace metals and sulfide, referred to as microniches. A model of transport and reaction in sediments that can simulate the dynamic development of concentration gradients occurring in 3-D was developed. Its graphical user interface allows easy input of user-specified reactions and provides flexible schemes that prioritise their execution. The 3-D capability was demonstrated by quantitative modelling of hypothetical solute behaviour at organic matter microniches covering a range of sizes. Significant effects of microniches on the profiles of oxygen and nitrate are demonstrated. Sulfide is shown to be readily generated in microniches within 1 cm of the sediment surface, provided the diameter of the reactive organic material is greater than 1 mm. These modelling results illustrate the geochemical complexities that arise when processes occur in 3-D and demonstrate the need for such a model. Future use of high-resolution measurement techniques should include the collection of data for relevant major components, such as reactive iron and manganese oxides, to allow full, multicomponent modelling of microniche processes.

Analysis of the impact of biomass burning emissions on global ozone production in the upper troposphere with MOCAGE CTM and IAGOS airborne data.

2020 ◽  
Author(s):  
Martin Cussac ◽  
Virginie Marécal ◽  
Valérie Thouret ◽  
Béatrice Josse
Keyword(s):  
Significant Role ◽  
Biomass Burning ◽  
Transport Model ◽  
Chemical Species ◽  
Ozone Production ◽  
In Situ Observation ◽  
Transport Pathway ◽  
Upper Troposphere ◽  
The Impact

&lt;p&gt;The UTLS (Upper Troposphere/Lower Stratosphere) is a key layer of the atmosphere as its chemical composition impacts both the troposphere and the stratosphere, and therefore plays a significant role in the climate system. Ozone at this altitude for instance plays a great role on surface temperature. Unlike in the stratosphere; it can be produced from the photolysis of precursors originating in the troposphere; mainly nitrous oxides (NO&lt;sub&gt;x&lt;/sub&gt;) and carbon monoxide (CO) at this pressure range. Biomass burning emissions in particular are likely to play a significant role in the quantities of these species in the upper troposphere and thus impacting ozone balance. This effect is investigated thanks to the global chemistry transport model MOCAGE. Because of the strong vertical gradients in this layer of the atmosphere, well resolved in-situ observation dataset are valuable for model evaluation. As of measurements used to validate MOCAGE results, IAGOS in-situ measurements from equipped commercial aircraft were chosen for their fine vertical resolution as well as their wide geographical coverage. Using both of these tools, upper tropospheric air composition is studied, with a focus on ozone precursors and production linked to biomass burning emissions.&lt;/p&gt;&lt;p&gt;Firstly is investigated the direct impact of biomass burning emissions on CO concentration in the upper troposphere, as it is both a good tracer of wildfire plumes in the atmosphere and it plays a role in the upper troposphere chemical balance. For this purpose MOCAGE simulations spaning over the year of 2013 where biomass burning emissions were turned on and off are compared to estimate a contribution to upper tropospheric CO. These simulations were validated using all the available data from the IAGOS database. It was found that biomass burning impacted CO levels globally, with the strongest enhancement happening above the most emitting areas (equatorial Africa and the Boreal forests). The importance of a fast vertical transport pathway above the fires was also highlighted with the possible occurrence of pyroconvection in addition to deep convection. Secondly, other chemical species related to ozone production were looked upon. Peroxyacetyl Nitrates (PAN) for instance were found to be impacted by biomass burning as it is a product of NOx oxidation as well as the main &quot;reservoir&quot; specie for NOx in the upper troposphere. Ultimately, ozone production resulting from biomass burning emissions is investigated, both in biomass burning plumes encountered by IAGOS aircraft, and on a more global scale using the MOCAGE simulations.&lt;/p&gt;

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