Long-term mass flux assessment of a DNAPL source area treated using bioremediation

Abstract Contributions of convective gravity waves (CGWs) and orographic gravity waves (OGWs) to the Brewer–Dobson circulation (BDC) are examined and compared to those from resolved waves. OGW drag (OGWD) is provided by NCEP Climate Forecast System Reanalysis (CFSR), while CGW drag (CGWD) is obtained from an offline calculation of a physically based CGW parameterization with convective heating and background data provided by CFSR. CGWD contributes to the shallow branch of the BDC regardless of the season, while OGWD contributes to both the shallow and deep branches except for the summertime, when OGWs hardly propagate into the stratosphere. At 70 hPa, the annual-mean tropical upward mass fluxes from Eliassen–Palm flux divergence (EPD), OGWD, and CGWD are 68%, 7%, and 4% of the total mass flux, respectively. The tropical upward mass flux at 70 hPa shows an increasing trend during the time period from 1979 to 1998, with 28%, 18%, and 6% of the trend driven by EPD, OGWD, and CGWD, respectively. The width of the turnaround latitudes tends to narrow for the streamfunctions induced by OGWD and CGWD but tends to widen for that induced by EPD. The contributions of GWD from MERRA (MERRA-2) to the climatology and long-term trend of the BDC are 7% (7%) and 13% (4%), respectively, somewhat smaller than the contributions of CGWD plus OGWD, which are estimated from CFSR to be 12% and 20%, respectively.

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A salt-rejecting anisotropic structure for efficient solar desalination via heat–mass flux decoupling

Journal of Materials Chemistry A ◽

10.1039/d0ta04326e ◽

2020 ◽

Vol 8 (24) ◽

pp. 12089-12096 ◽

Cited By ~ 2

Author(s):

Wei Zhang ◽

Xi Chen ◽

Gong Zhang ◽

Jianfei Li ◽

Qinghua Ji ◽

...

Keyword(s):

Mass Flux ◽

Anisotropic Structure ◽

Salt Rejection ◽

Solar Desalination

Heat–mass decoupling enabled by anisotropy can simultaneously ensure rapid salt rejection and enhanced heat localization, achieving long-term efficient solar desalination.

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On the factors influencing surface-layer energy closure and their seasonal variability over the semi-arid Loess Plateau of Northwest China

Hydrology and Earth System Sciences ◽

10.5194/hess-16-893-2012 ◽

2012 ◽

Vol 16 (3) ◽

pp. 893-910

Author(s):

X. Xiao ◽

H. C. Zuo ◽

Q. D. Yang ◽

S. J. Wang ◽

L. J. Wang ◽

...

Keyword(s):

Surface Layer ◽

Energy Balance ◽

Atmospheric Turbulence ◽

Loess Plateau ◽

Turbulence Intensity ◽

Source Area ◽

Northwest China ◽

The Impact ◽

Semi Arid

Abstract. The energy observed in the surface layer, when using eddy-covariance techniques to measure turbulent fluxes, is not balanced. Important progress has been made in recent years in identifying potential reasons for this lack of closure in the energy balance, but the problem is not yet resolved. In this paper, long-term data that include output of tower, radiation, surface turbulence flux and soil measurement collected from September 2006 to August 2010 in the Semi-Arid Climate Change and Environment Observatory, Lanzhou University, in the semi-arid Loess Plateau of Northwest China, were analysed, focusing on the seasonal characteristics of the surface energy and the factors that have impact on the energy balance closure (EBC). The analysis shows that (1) the long-term observations are successful; the interaction between the land and the atmosphere in semi-arid climates can be represented by the turbulent transport of energy. In addition, even though the residual is obvious, this suggests that the factors that impact the EBC are stable, and their seasonal variations are identical. The analysis also shows that (2) four factors have obvious impact on the EBC: the diverse schemes for surface soil heat flux, the flux contribution from the target source area, the low-frequency part of the turbulence spectra, and the strength of atmospheric turbulence motion. The impact of these four factors on the EBC are similar in all seasons. Lastly, the results indicate that (3) atmospheric turbulence intensity is a very important factor in terms of its impact on the EBC. The relative turbulence intensity, RIw, characterises the strength of atmospheric turbulence motion, and is found to exert a noticeable impact on the EBC; in all seasons, the EBC is increased when the relative turbulence intensity is enlarged.

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Long-Term Performance Evaluation of Groundwater Chlorinated Solvents Remediation Using Nanoscale Emulsified Zerovalent Iron at a Superfund Site

Applying Nanotechnology for Environmental Sustainability - Advances in Environmental Engineering and Green Technologies ◽

10.4018/978-1-5225-0585-3.ch005 ◽

2016 ◽

pp. 92-111

Author(s):

Chunming Su ◽

Robert W. Puls ◽

Thomas A. Krug ◽

Mark T. Watling ◽

Suzanne K. O'Hara ◽

...

Keyword(s):

Performance Evaluation ◽

Mass Flux ◽

Direct Injection ◽

Field Tests ◽

Source Zone ◽

Zerovalent Iron ◽

Superfund Site ◽

Nitrogen Gas ◽

Environmental Nanotechnology

This chapter addresses a case study of long-term assessment of a field application of environmental nanotechnology. Dense Non-Aqueous Phase Liquid (DNAPL) contaminants such as Tetrachloroethene (PCE) and Trichloroethene (TCE) are a type of recalcitrant compounds commonly found at contaminated sites. Recent research has focused on their remediation using environmental nanotechnology in which nanomaterials such as nanoscale Emulsified Zerovalent Iron (EZVI) are added to the subsurface environment to enhance contaminant degradation. Such nanoremediation approach may be mostly applicable to the source zone where the contaminant mass is the greatest and source removal is a critical step in controlling the further spreading of the groundwater plume. Compared to micro-scale and granular counterparts, NZVI exhibits greater degradation rates due to its greater surface area and reactivity from its faster corrosion. While NZVI shows promise in both laboratory and field tests, limited information is available about the long-term effectiveness of nanoremediation because previous field tests are mostly less than two years. Here an update is provided for a six-year performance evaluation of EZVI for treating PCE and its daughter products at a Superfund site at Parris Island, South Carolina, USA. The field test consisted of two side-by-side treatment plots to remedy a shallow PCE source zone (less than 6 m below ground surface) using pneumatic injection and direct injection, separately in October 2006. For the pneumatic injections, a two-step injection procedure was used. First, the formation was fluidized by the injection of nitrogen gas alone, followed by injection of the EZVI with nitrogen gas as the carrier. In the pneumatic injection plot, 2,180 liters of EZVI containing 225 kg of iron (Toda RNIP-10DS), 856 kg of corn oil, and 22.5 kg of surfactant were injected to remedy an estimated 38 kg of chlorinated volatile compounds (CVOC)s. Direct injections were performed using a direct push rig. In the direct injection plot, 572 liters of EZVI were injected to treat an estimated 0.155 kg of CVOCs. Visual inspection of collected soil cores before and after EZVI injections shows that the travel distance of EZVI was dependent on the method of delivery with pneumatic injection achieving a greater distance of 2.1 m than did direct injection reaching a distance of 0.89 m. Significant decreases in PCE and TCE concentrations were observed in downgradient wells with corresponding increases in degradation products including significant increases in ethene. In the pneumatic injection plot, there were significant reductions in the downgradient groundwater mass flux values for chlorinated ethenes (>58%) and a significant increase in the mass flux of ethene (628%). There were significant reductions in total CVOCs mass (78%), which was less than an estimated 86% decrease in total CVOCs made at 2.5 years due to variations in soil cores collected for CVOCs extraction and determination; an estimated reduction of 23% (vs.63% at 2.5 years) in the sorbed and dissolved phases and 95% (vs. 93% at 2.5 years) reduction in the PCE DNAPL mass. Significant increases in dissolved sulfide, volatile fatty acids (VFA), and total organic carbon (TOC) were observed and dissolved sulfate and pH decreased in many monitoring wells. The apparent effective destruction of CVOC was accomplished by a combination of abiotic dechlorination by nanoiron and biological reductive dechlorination stimulated by the oil in the emulsion. No adverse effects of EZVI were observed for the microbes. In contrast, populations of dehalococcoides showed an increase up to 10,000 fold after EZVI injection. The dechlorination reactions were sustained for the six-year period from a single EZVI delivery. Repeated EZVI injections four to six years apart may be cost-effective to more completely remove the source zone contaminant mass. Overall, the advantages of the EZVI technology include an effective “one-two punch” of rapid abiotic dechlorination followed by a sustained biodegradation; contaminants are destroyed rather than transferred to another medium; ability to treat both DNAPL source zones and dissolved-phase contaminants to contain plume migration; ability to deliver reactants to targeted zones not readily accessible by conventional permeable reactive barriers; and potential for lower overall costs relative to alternative technologies such as groundwater pump-and-treat with high operation and maintenance costs or thermal technologies with high capital costs. The main limitations of the EZVI technology are difficulty in effectively distributing the viscous EZVI to all areas impacted with DNAPL; potential decrease in hydraulic conductivity due to iron corrosion products buildup or biofouling; potential to adversely impact secondary groundwater quality through mobilization of metals and production of sulfides or methane; injection of EZVI may displace DNAPL away from the injection point; and repeated injections may be required to completely destroy the contaminants.

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Long-Term Performance Evaluation of Groundwater Chlorinated Solvents Remediation Using Nanoscale Emulsified Zerovalent Iron at a Superfund Site

Waste Management ◽

10.4018/978-1-7998-1210-4.ch061 ◽

2020 ◽

pp. 1352-1371

Author(s):

Chunming Su ◽

Robert W. Puls ◽

Thomas A. Krug ◽

Mark T. Watling ◽

Suzanne K. O'Hara ◽

...

Keyword(s):

Performance Evaluation ◽

Mass Flux ◽

Direct Injection ◽

Field Tests ◽

Source Zone ◽

Zerovalent Iron ◽

Superfund Site ◽

Nitrogen Gas ◽

Environmental Nanotechnology

This chapter addresses a case study of long-term assessment of a field application of environmental nanotechnology. Dense Non-Aqueous Phase Liquid (DNAPL) contaminants such as Tetrachloroethene (PCE) and Trichloroethene (TCE) are a type of recalcitrant compounds commonly found at contaminated sites. Recent research has focused on their remediation using environmental nanotechnology in which nanomaterials such as nanoscale Emulsified Zerovalent Iron (EZVI) are added to the subsurface environment to enhance contaminant degradation. Such nanoremediation approach may be mostly applicable to the source zone where the contaminant mass is the greatest and source removal is a critical step in controlling the further spreading of the groundwater plume. Compared to micro-scale and granular counterparts, NZVI exhibits greater degradation rates due to its greater surface area and reactivity from its faster corrosion. While NZVI shows promise in both laboratory and field tests, limited information is available about the long-term effectiveness of nanoremediation because previous field tests are mostly less than two years. Here an update is provided for a six-year performance evaluation of EZVI for treating PCE and its daughter products at a Superfund site at Parris Island, South Carolina, USA. The field test consisted of two side-by-side treatment plots to remedy a shallow PCE source zone (less than 6 m below ground surface) using pneumatic injection and direct injection, separately in October 2006. For the pneumatic injections, a two-step injection procedure was used. First, the formation was fluidized by the injection of nitrogen gas alone, followed by injection of the EZVI with nitrogen gas as the carrier. In the pneumatic injection plot, 2,180 liters of EZVI containing 225 kg of iron (Toda RNIP-10DS), 856 kg of corn oil, and 22.5 kg of surfactant were injected to remedy an estimated 38 kg of chlorinated volatile compounds (CVOC)s. Direct injections were performed using a direct push rig. In the direct injection plot, 572 liters of EZVI were injected to treat an estimated 0.155 kg of CVOCs. Visual inspection of collected soil cores before and after EZVI injections shows that the travel distance of EZVI was dependent on the method of delivery with pneumatic injection achieving a greater distance of 2.1 m than did direct injection reaching a distance of 0.89 m. Significant decreases in PCE and TCE concentrations were observed in downgradient wells with corresponding increases in degradation products including significant increases in ethene. In the pneumatic injection plot, there were significant reductions in the downgradient groundwater mass flux values for chlorinated ethenes (>58%) and a significant increase in the mass flux of ethene (628%). There were significant reductions in total CVOCs mass (78%), which was less than an estimated 86% decrease in total CVOCs made at 2.5 years due to variations in soil cores collected for CVOCs extraction and determination; an estimated reduction of 23% (vs.63% at 2.5 years) in the sorbed and dissolved phases and 95% (vs. 93% at 2.5 years) reduction in the PCE DNAPL mass. Significant increases in dissolved sulfide, volatile fatty acids (VFA), and total organic carbon (TOC) were observed and dissolved sulfate and pH decreased in many monitoring wells. The apparent effective destruction of CVOC was accomplished by a combination of abiotic dechlorination by nanoiron and biological reductive dechlorination stimulated by the oil in the emulsion. No adverse effects of EZVI were observed for the microbes. In contrast, populations of dehalococcoides showed an increase up to 10,000 fold after EZVI injection. The dechlorination reactions were sustained for the six-year period from a single EZVI delivery. Repeated EZVI injections four to six years apart may be cost-effective to more completely remove the source zone contaminant mass. Overall, the advantages of the EZVI technology include an effective “one-two punch” of rapid abiotic dechlorination followed by a sustained biodegradation; contaminants are destroyed rather than transferred to another medium; ability to treat both DNAPL source zones and dissolved-phase contaminants to contain plume migration; ability to deliver reactants to targeted zones not readily accessible by conventional permeable reactive barriers; and potential for lower overall costs relative to alternative technologies such as groundwater pump-and-treat with high operation and maintenance costs or thermal technologies with high capital costs. The main limitations of the EZVI technology are difficulty in effectively distributing the viscous EZVI to all areas impacted with DNAPL; potential decrease in hydraulic conductivity due to iron corrosion products buildup or biofouling; potential to adversely impact secondary groundwater quality through mobilization of metals and production of sulfides or methane; injection of EZVI may displace DNAPL away from the injection point; and repeated injections may be required to completely destroy the contaminants.

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Geomorphic imprint of dynamic topography and intraplate tectonism in central Australia

10.5194/egusphere-egu2020-20252 ◽

2020 ◽

Author(s):

John Jansen ◽

Mike Sandiford ◽

Toshiyuki Fujioka ◽

Timothy Cohen ◽

Martin Struck ◽

...

Keyword(s):

Source Area ◽

Plate Motion ◽

Dynamic Topography ◽

Vertical Movements ◽

Sediment Dispersal ◽

Drainage Patterns ◽

First Case ◽

Central Australia ◽

To Come

The mantle convection accompanying plate motion causes vertical movements of up to a few hundred metres at Earth&#8217;s surface over wavelengths of 102&#8211;103 km. This dynamic topography appears to come and go at ~ 1&#8211;10 Myr timescales in areas that are often well away from plate margins, although its spatial and temporal characteristics are subject to ongoing debate. Since such motions are small and transient, discriminating convective signals from other drivers of relief generation and/or sediment dispersal remains tricky. An outstanding challenge is to detect these elusive, transient undulations from a tell-tale geomorphic imprint preserved in either drainage patterns or the stratigraphic record.In the intra-plate setting of central Australia, a 30 km long sinuous gorge is developed where the major regional drainage, Finke River, dissects a band of low hills. Remarkably, this gorge is intertwined with an abandoned and less deeply incised gorge that forms hanging junctions and shares similar width and sinuosity. This unusual overprinting of the two gorges remains unexplained.With an aim to investigate the history of the intertwined gorges, we measured cosmogenic 10Be and 26Al in fluvial gravels stored in the palaeovalley cutoffs. The gravels are remnants of major alluviation episodes that we surmise result from ongoing vertical motions associated with dynamic topography. We use a Markov chain Monte Carlo-based inversion model to test two hypotheses to explain the nuclide inventory contained within the stored fluvial gravels. In the first case, rapid alluviation and erosion since 1 Ma preserves the nuclide memory of the source area; in the second, the nuclide memory is erased during long-term fluvial storage (> 5 Myr) and is restored during exhumation of the palaeovalley gravel-pile. The two hypotheses are therefore limiting-case scenarios that constrain overall fast versus slow landscape evolution, respectively. Our model results suggest that long-term burial decouples the source-area signal from nuclide abundances measured in the palaeovalley gravels. This casts events into a Miocene timescale.

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Local Perceptions Of Migration From North-West Ghana

Africa ◽

10.3366/afr.2010.0404 ◽

2010 ◽

Vol 80 (4) ◽

pp. 595-619 ◽

Cited By ~ 10

Author(s):

Kees van der Geest

Keyword(s):

Return Migration ◽

Source Area ◽

Northern Ghana ◽

Holistic View ◽

North West ◽

Home Community ◽

Household Heads ◽

The Impact ◽

At Home

ABSTRACTThe Upper West Region in northern Ghana is a major source area of migrants who travel to southern Ghana seasonally or for longer periods. This has important implications for the lives and livelihoods of the migrants themselves and their relatives at home. Almost invariably the impact of out-migration on sending areas has been studied using ‘Western’ academic parameters. Little is known about how the people hemselves value the profound changes that migration causes in their societies. In this article, findings are presented from interviews with 204 rural household heads who were asked to express their opinion about the consequences of seasonal, long-term and return migration. A quantitative approach to qualitative data was adopted to differentiate between collective perceptions and individual opinions. It was found that almost all respondents were positive about the consequences of seasonal labour migration. They applauded its contribution to food security and considered it one of the few ways of gaining access to money and goods. The respondents were much more ambivalent about the consequences of long-term migration and return migration. On the positive side, they emphasized that out-migration reduced the pressure on farmland, and that some migrants attain higher living standards, both for themselves and for their relatives at home. On the negative side, many long-term migrants are not able to improve their livelihoods or lose their interest in the home community. The lack of support of some migrants is greatly lamented, especially if they later return empty-handed and become a burden on their relatives at home. The methodology used in this study yielded a holistic view of the consequences of migration on the source area as seen through the eyes of the home community

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Long-term hydrologic simulation using storage and source area concepts

Hydrological Processes ◽

10.1002/hyp.5735 ◽

2005 ◽

Vol 19 (14) ◽

pp. 2845-2861 ◽

Cited By ~ 14

Author(s):

S. K. Mishra ◽

K. Geetha ◽

A. K. Rastogi ◽

R. P. Pandey

Keyword(s):

Source Area ◽

Hydrologic Simulation

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