Transport Model Results Research Articles

Effectiveness of Monitored Natural Attenuation (MNA) as a Groundwater Remedy for Arsenic in Phosphatic Wastes

AbstractA study was conducted to evaluate monitored natural attenuation (MNA) as a remedy for arsenic in groundwater at a former phosphate mining and manufacturing facility. The mineralogy, speciation, and lability of arsenic in phosphatic wastes present in soils were characterized using sequential extraction procedures, leaching experiments, batch adsorption tests, and microchemical speciation analysis. A PHREEQC‐based reactive transport model was also parameterized using these laboratory results, and it was used to evaluate the importance of identified attenuation mechanisms on arsenic concentrations along a vertical flow path from a shallow, alluvial aquifer to the underlying Floridan aquifer. Arsenic was found to occur in several chemical forms in phosphatic wastes, including unstable sulfide minerals, adsorbed surface complexes, and relatively insoluble phosphate and oxide minerals. Most arsenic was associated with stable minerals. The reactive transport model predicted that historical leaching of solid‐phase waste materials in soils would not have generated enough arsenic to explain the concentrations observed in downgradient groundwater; instead, the source of arsenic to groundwater was likely acidic and saline process water that infiltrated though unlined ponds and ditches during historical manufacturing operations. A key factor affecting the long‐term effectiveness of natural attenuation of arsenic in groundwater is the occurrence and stability of iron oxyhydroxides in aquifer sediments. According to laboratory and reactive transport model results, sufficient levels were found to be present at the site to effectively limit arsenic migration at concentrations exceeding drinking water standards in the future in the Floridan aquifer. This study presents the geochemical evaluations that are needed to satisfy EPA guidelines on determining whether or not MNA is an acceptable remedy for a site. It specifically details the characterization and modeling that were used to demonstrate effectiveness at a site where MNA was ultimately selected as the remedy for arsenic in groundwater.

Application of a Fusion Method for Gas and Particle Air Pollutants between Observational Data and Chemical Transport Model Simulations Over the Contiguous United States for 2005-2014.

Accurate spatiotemporal air quality data are critical for use in assessment of regulatory effectiveness and for exposure assessment in health studies. A number of data fusion methods have been developed to combine observational data and chemical transport model (CTM) results. Our approach focuses on preserving the temporal variation provided by observational data while deriving the spatial variation from the community multiscale air quality (CMAQ) simulations, a type of CTM. Here we show the results of fusing regulatory monitoring observational data with 12 km resolution CTM simulation results for 12 pollutants (CO, NOx, NO2, SO2, O3, PM2.5, PM10, NO3−, NH4+, EC, OC, SO42−) over the contiguous United States on a daily basis for a period of ten years (2005–2014). An annual mean regression between the CTM simulations and observational data is used to estimate the average spatial fields, and spatial interpolation of observations normalized by predicted annual average is used to provide the daily variation. Results match the temporal variation well (R2 values ranging from 0.84–0.98 across pollutants) and the spatial variation less well (R2 values 0.42–0.94). Ten-fold cross validation shows normalized root mean square error values of 60% or less and spatiotemporal R2 values of 0.4 or more for all pollutants except SO2.

From core-scale experiment to reservoir-scale modeling: A scale-up approach to investigate reaction-induced permeability evolution of CO2 storage reservoir and caprock at a U.S. CO2 storage site

Mineral dissolution and secondary mineral precipitation can cause porosity and permeability changes of CO2 storage reservoirs and caprocks after injection of CO2. In this paper, a 3-step approach (core-scale experiment →core-scale modeling →reservoir-scale modeling) is developed to simulate reservoir-scale porosity and permeability evolution of CO2 storage formation and caprock at a model CO2 storage site. The model site is based on characteristics of a real site in Mississippi, USA. Important chemical and permeability modeling parameters in the reservoir-scale model are validated by core-scale experimental and reactive transport modeling results. The reservoir-scale model predicts a maximum 3.2% permeability increase of the CO2 storage formation and a maximum 1.1% permeability increase of the caprock after 1000 years of exposure to CO2-rich brine, while the core-scale model predicts 7% permeability decrease for a small CO2 storage formation core and 296% permeability increase for a small caprock core after 180-day exposure to CO2-rich brine. The discrepancy between permeability results of reservoir-scale model and core-scale model is attributed to strong pH buffering effect of CO2 storage formation with large mass of H+-consuming minerals. Therefore, using core-scale experiments/models only is not sufficient to elucidate reservoir-scale permeability evolution. Variations of key model parameters have a small effect on permeability evolution of both CO2 storage formation and caprock, except for variations of Keq (SiO2 (am)) and the exponent n in permeability-porosity correlation. SiO2 (am) is a key mineral that governs permeability evolution of CO2 storage formation and caprock, given the characteristics of the model CO2 storage site.

Development of Intersection Management Strategy Due to Opening of Sumatra Toll Road

The main role of a transportation network is providing optimum services for transportation network. Over the time, the population is increasing and the needs of reliable transportation network also increased. Transportation network consists of node and connector. According to the condition, the provision of reliable transportation network facilities should be able to optimize the node and the link. In the real condition, there’s a gap between the existing transportation network conditions with the optimum transportation network conditions, as a result the existing transportation network is not able to serve the transportation movement that occurred. Based on this information, research entitled Development of Intersection Management Strategy Due to Opening of Sumatra Toll Road. The objective of this study are: a) Generating traffic flow through the Simpang Polsek Sukarame, Bandar Lampung. b) Evaluating the traffic composition through Simpang Polsek Sukarame, Bandar Lampung. c) Evaluating services intersection parameters needed in evaluating the intersection. d) Determining the intersection strategy of intersection due to the opening of the Sumatra Toll Road. The study is conducted by using Macroscopic Modeling approach using PTV Vissum application and microscopic evaluation using MKJI 1997. In the research, there are several types of data needed. These data are classified into primary and secondary data. Primary data required include: a) Traffic Counting Data, TC Data implemented at Simpang Polsek Sukarame. Traffic Counting data is used as a database for the validation of the transportation model. b) Road geometry data is taken at all connector of Simpang Polsek Sukarame. The Geometry consist of the road width and shoulder width. Geometry data is used for capacity calculation, delay, and saturation degree. From the results of transport modelling that will be evaluated the service level of the intersection based on the parameters of degree of saturation, delay, and speed of vehicles through the intersection. The Result of the model shows that The queue length increasing from 10.66 m to 16.64 m or increasing for around 60% and the average delay increasing from 7 s to 13.43 s or increasing around 95%. It will be concluded that the addition of toll road traffic is affecting the intersection performance.

Modelling the fate and transport of Cryptosporidium, a zoonotic and waterborne pathogen, in the Daning River watershed of the Three Gorges Reservoir Region, China

Oospores of Cryptosporidium, a waterborne pathogen of great concern, are widely distributed in surface waters in China and pose a threat to human health. This study seeks to explore the spatio-temporal patterns of Cryptosporidium concentrations. We focus on the Daning River watershed (4166 km2) of the Three Gorges Reservoir Region (TGR) during the period 2008 to 2013 and use the SWAT (Soil and Water Assessment Tool) model to test two mitigation scenarios. Based on data on animal husbandry, population, agriculture and WWTPs (wastewater treatment plants), Cryptosporidium transport in the Daning River watershed was simulated using a calibrated hydrological and sediment transport model. Our model results showed that the average annual concentration of oocysts in the whole watershed was 9.5 oocysts/10L, but high spatial variability occurred, ranging from 0.7 to 33.4 oocysts/10L. Highest monthly mean oocysts concentrations at the outlets of the sub-basins were found at high runoff and high fertilization or at the lowest flow, while minimum monthly mean oocysts concentrations were recorded at high runoff only. A model parameter sensitivity analysis showed that the Cryptosporidium soil partitioning coefficient (BACTKDQ) and the temperature adjustment factor for Cryptosporidium die-off (THBACT) were the only two sensitive parameters among the microbial parameters. The construction of multiple WWTPs throughout the watershed and composting of 50% of the feces from rural citizens and livestock up to 56 days before its application as fertilizer could significantly reduce the concentration of oocysts. Our Cryptosporidium transport model and simulation results may assist in the establishment of better pollution control countermeasures in the Daning River and other similar watersheds.

On the fate of oxygen in a spent fuel emplacement drift in Opalinus Clay

Persistence of aerobic conditions after backfilling of a spent fuel emplacement drift is of high relevance for the selection of canister material and canister design, as well as for the prediction of the onset of H2 production. This paper presents the results of the O2 monitoring during the backfilling and early heating phases of the Full-scale Emplacement Experiment at the Mont Terri underground laboratory (Switzerland), as well as the first results of laboratory experiments and 3D reactive transport modelling which aim at identifying the processes controlling O2 concentrations. The monitoring shows the disappearance of gaseous O2 and onset of anaerobic corrosion in sections not affected by O2 inflow from the access tunnel within weeks after backfilling, and even before closure of the drift for the deepest parts of the experiment. The laboratory experiments show that O2 can significantly adsorb on granular bentonite exposed to high temperatures and might in principle also adsorb at ambient temperature and relative humidity as low as 55%. Thus, gas sorption should be considered in the balance of O2 in the experiment. These results are consistent with the numerical model indicating that the excavation damaged zone but also the bentonite backfill are the main sinks for O2, whereas corrosion of metallic components seems to play a negligible role. Previous studies estimated the duration of aerobic conditions in an emplacement drift between a few years and several decades; our results show that anaerobic conditions may be reached within a few weeks up to maximum a few months after closure of an emplacement drift for spent fuel.

Linked Response of Aerosol Acidity and Ammonia to SO2 and NO x Emissions Reductions in the United States.

Large reductions of sulfur and nitrogen oxide emissions in the United States have led to considerable improvements in air quality, though recent analyses in the Southeastern United States have shown little response of aerosol pH to these reductions. This study examines the effects of reduced emissions on the trend of aerosol acidity in fine particulate matter (PM2.5), at a nationwide scale, using ambient concentration data from three monitoring networks-the Ammonia Monitoring Network (AMoN), the Clean Air Status and Trends network (CASTNET) and the Southeastern Aerosol Research and Characterization Network (SEARCH), in conjunction with thermodynamic (ISORROPIA-II) and chemical transport (CMAQ) model results. Sulfate and ammonium experienced similar and significant decreases with little change in pH, neutralization ratio ( f = [NH4+]/2[SO42-] + [NO3-]), or nitrate. Oak Grove, MS was the only SEARCH site showing statistically significant pH changes in the Southeast region where small increases in pH (0.003-0.09 pH units/year) were observed. Of the five regions characterized using CASTNET/AMoN data, only California exhibited a statistically significant, albeit small pH increase of +0.04 pH units/year. Furthermore, statistically insignificant (α = 0.05) changes in ammonia were observed in response to emission and PM2.5 speciation changes. CMAQ simulation results had similar responses, showing steady ammonia levels and generally low pH, with little change from 2001 to 2011.

Decision support system for transport corridors on the basis of a dynamic model of transport flow distribution

Abstract Traffic management in transport corridors of large cities requires the application of new methods and state-of-the-art information technologies for forecasting the current and future transport situation. Understanding of transport demand evolution processes under a dynamically changing transport situation is an extremely important and crucial task. Modern application tools for computer modeling can be used for improving the quality of decisions made in the course of traffic flow management in large cities. The new methods for forecasting the transport situation using the results of computer dynamic transport modeling increase the reliability and quality of transport decisions made. The article presents a decision support system for transport corridors, based on the use of dynamic modeling and distribution of traffic flows depending on the changing load of transport network elements. A scheme for evaluating the quality and efficiency of traffic management in a meso-level dynamic model is presented. Results of calculations for the main macro parameters of traffic flow, such as density and intensity, obtained on the basis of the developed model are presented. The article shows main indicators of modeling zone efficiency, which can be used in the practice of transport corridor management. Assumptions on the use of new transport data in decision support systems for transport corridors are made. A methodological framework for the deployment of such system through the example of Ryazan city is briefly described. Results of practical transport calculations based on a mesoscopic-level dynamic simulation model developed using the DTAlite/NEXTA software are presented. The presented system can be used in decision-making and forecasting of the transport situation in road networks operating under high load conditions.

Forecast of Reactive CO2 Injection into a Carbonate Formation, Middle East

This paper describes the results of reservoir and reactive transport modelling using MoReS-PHREEQC to study the long-term fate of CO2 injection in a carbonate aquifer. The heterogeneous model is based on a geological model built in Petrel, contains faults, various rock types, and various porosity-permeability relationships. The mineralogy of the target formation is dominated by calcite, but also contains dolomite. The results show that CO2 predominantly migrates along the high permeability zones at the top and the bottom of the target formation where CO2 is injected into. Impermeable layers (aquitards) on top of the target formation effectively block upwards migration. However, the plume reaches a conductive fault at the end of the injection (after 30 years), causing upward migration of CO2. Migration of CO2 into the fault appeared to be sensitive to the injection well location and different realizations of the geological model. Accurate mapping of faults and choice of injection well locations are therefore important for controlling CO2 conformance with time. Dissolution and dissociation of CO2 lowers the pH, leading to buffering by calcite and dolomite dissolution, as well as precipitation of anhydrite and celestine. The mineral amounts that dissolved or precipitated are relatively small and lead to porosity increase up to 0.03% within the impacted zone after 1,000 years. The geochemical impact of CO2 injection into the carbonate aquifer is therefore relatively low.

Solute transport in porous media during drying: The chlorine isotopes point of view

Drying-out phenomena during injection of dry gas (CO2, CH4, H2, …) in geological reservoirs can be damaging for industrial processes as it can alter the transport properties and the injectivity of a reservoir due to salt precipitation. The distribution of salt precipitate, which may result in clogging of the formation, depends on two competing transport processes. Brine capillary-driven flows, which provide a continuous supply of dissolved salt towards the drying zone, and molecular diffusion, which tends to rehomogenize dissolved salt concentrations. In this study, we experimentally investigated the possibility that chlorine isotopes could be used as a geochemical tool to constrain the interplay of salt precipitation and solute transports process in drying saline porous media. Drying experiments were carried out on Lavoux carbonate plugs initially saturated with a 100gL−1 NaCl brine and dried in an oven at controlled temperature (60°C) with vapor evacuation. Cl-content and δ37Cl profiles along the length of the plugs were obtained for different evaporation stages (Sw=1; Sw=0.82; Sw=0.68). The results show a clear Cl-ion redistribution during drying, with Cl-accumulation near the plug evaporative surface together with the growth of salt efflorescence on the surface. A “u”-shaped profile of δ37Cl values is observed in the drying porous media. After 30h of drying, salt crystals as well as the upper and lower parts of the plug present higher isotope ratios than the initial brine, while the center of the plug presents lower ratios. These experimental results suggest, as predicted by previous experimental and theoretical studies, that 35Cl and 37Cl are transported without fractionation by upward capillary flow to the evaporative surface, where salt precipitation occurs with a small preference for the heavier isotope. The resulting concentration gradient drives backward diffusion. Because 35Cl moves faster than 37Cl by diffusion this leads to more negative δ37Cl towards the center of the plug. Cl-isotopes transport modeling results suggest that backward advection may also have occurred, as indicated by a relatively high effective diffusion coefficient and a low Cl-isotope fractionation factor. This study provides new insights regarding the use of Cl-isotopes to characterize drying of porous media.

A modeling study of the impact of major storms on seabed shear stress and sediment transport on the Grand Banks of Newfoundland

AbstractWaves, current, and sediment transport processes in major storms on the Grand Banks of Newfoundland were simulated using integrated wave, three‐dimensional tide and circulation, and combined‐flow sediment transport models. While the tidal and nontidal currents are generally low and cause little sediment transport, storm‐induced waves and currents enhance bed shear velocity by more than 5 times and cause significant sediment transport over the entire Grand Banks. The impact of storms on shear stress and transport strongly depends on water depths and the greatest impact occurs over the bathymetric highs on southeastern Grand Bank where the maximum shear velocity reaches 15 cm s−1 and the maximum transport rates are >5 kg m−1 s−1. The direction of sediment transport rotates clockwise progressively through nearly 360° during the passage of a storm. Although peak transport typically occurs on central and southeastern Grand Bank with a southeastward direction, the magnitude, direction, and timing of peak transport show strong spatial and temporal variability. The variability of the peak transport largely depends on the timing and relative intensity of the waves and the total bottom currents which in turn depends on the addition of the storm‐induced and tidal currents. The calculation of the maximum transport potential suggests that sediments as coarse as small pebbles are mobile in water depths <80 m under 1:1 year storms and that medium sand is transported in water depths as deep as 200 m during major storms. Results of the sediment transport models corroborate the observed sediment erosion and accretion patterns.

Nitrate transboundary heavy pollution over East Asia in winter

Abstract. High PM2. 5 concentrations of around 100 µg m−3 were observed twice during an intensive observation campaign in January 2015 at Fukuoka (33.52° N, 130.47° E) in western Japan. These events were analyzed comprehensively with a regional chemical transport model and synergetic ground-based observations with state-of-the-art measurement systems, which can capture the behavior of secondary inorganic aerosols (SO42−, NO3−, and NH4+). The first episode of high PM2. 5 concentration was dominated by NO3− (type N) and the second episode by SO42− (type S). The concentration of NH4+ (the counterion for SO42− and NO3−) was high for both types. A sensitivity simulation in the chemical transport model showed that the dominant contribution was from transboundary air pollution for both types. To investigate the differences between these types further, the chemical transport model results were examined, and a backward trajectory analysis was used to provide additional information. During both types of episodes, high concentrations of NO3− were found above China, and an air mass that originated from northeast China reached Fukuoka. The travel time from the coastline of China to Fukuoka differed between types: it was 18 h for type N and 24 h for type S. The conversion ratio of SO2 to SO42− (Fs) was less than 0.1 for type N, but reached 0.3 for type S as the air mass approached Fukuoka. The higher Fs for type S was related to the higher relative humidity and the concentration of HO2, which produces H2O2, the most effective oxidant for the aqueous-phase production of SO42−. Analyzing the gas ratio as an indicator of the sensitivity of NO3− to changes in SO42− and NH4+ showed that the air mass over China was NH3-rich for type N, but almost NH3-neutral for type S. Thus, although the high concentration of NO3− above China gradually decreased during transport from China to Fukuoka, higher NO3− concentrations were maintained during transport owing to the lower SO42− for type N. In contrast, for type S, the production of SO42− led to the decomposition of NH4NO3, and more SO42− was transported. Notably, the type N transport pattern was limited to western Japan, especially the island of Kyushu. Transboundary air pollution dominated by SO42− (type S) has been recognized as a major pattern of pollution over East Asia. However, our study confirms the importance of transboundary air pollution dominated by NO3−, which will help refine our understanding of transboundary heavy PM2. 5 pollution in winter over East Asia.

Comparison of the results of 85Kr transport modeling with the ACURATE field experiment data

Currently the Nuclear Safety Institute of the Russian Academy of Sciences (NSI RAS) jointly with the Hydrometcenter of Russia is developing the system for forecasting the transfer of radio-active substances in the atmosphere in case of radiation accidents at Russian nuclear power plants. The operation of the system is based on the numerical hydrodynamic model which allows forecasting meteorological parameters and is coupled with the mesoscale dispersion model of the transfer ofradioactive substances in the atmosphere. The results are presented of 85Kr transport modeling under the conditions of the ACURATE experiment with three transport models: FLEXPART, HYSPLIT, and the model from the NOSTRADAMUS software package. It is demonstrated that all three Lagrangian models can give a qualitative description of concentration fields from the ACURATE experiment with the best value of the RANK metric (2.5) based on three statistics.

Applying numerical modeling for designing strategies of effective groundwater remediation

Selection of effective groundwater remediation scenarios is a complex issue that requires understanding of contaminants’ transport processes. The effectiveness of cleanup measures may be verified by fate and transport numerical modeling. The goal of this work was to present the usefulness of fate and transport modeling for planning, verification and fulfillment of effective groundwater remediation methods. Selection methodology was developed, which is based on results of numerical flow and transport modeling. A field site located in south-east Poland was selected as a case study, in which groundwater contamination of trichloroethene and tetrachloroethene was detected. The results indicated that “pump and treat” was the most effective among the studied remediation methods, followed by permeable reactive barrier and in situ chemical oxidation. Natural attenuation-based remediation was demonstrated to be the least suitable, as it requires the longest time to reach predefined remediation goals, principally due to low sorption capacity and unfavorable hydrogeochemical conditions for biodegradation. Fate and transport numerical modeling allowed simulating different remediation strategies, and thus the decision-making process was facilitated.

Reactive transport model of the formation of oxide-type Ni-laterite profiles (Punta Gorda, Moa Bay, Cuba)

Oxide-type Ni-laterite deposits are characterized by a dominant limonite zone with goethite as the economically most important Ni ore mineral and a thin zone of hydrous Mg silicate-rich saprolite beneath the magnesium discontinuity. Fe, less soluble, is mainly retained forming goethite, while Ni is redeposited at greater depth in a Fe(III) and Ni-rich serpentine (serpentine II) or in goethite, where it adsorbs or substitutes for Fe in the mineral structure. Here, a 1D reactive transport model, using CrunchFlow, of Punta Gorda oxide-type Ni-laterite deposit (Moa Bay, Cuba) formation is presented. The model reproduces the formation of the different laterite horizons in the profile from an initial, partially serpentinized peridotite, in 106 years, validating the conceptual model of the formation of this kind of deposits in which a narrow saprolite horizon rich in Ni-bearing serpentine is formed above peridotite parent rock and a thick limonite horizon is formed over saprolite. Results also confirm that sorption of Ni onto goethite can explain the weight percent of Ni found in the Moa goethite. Sensitivity analyses accounting for the effect of key parameters (composition, dissolution rate, carbonate concentration, quartz precipitation) on the model results are also presented. It is found that aqueous carbonate concentration and quartz precipitation significantly affects the laterization process rate, while the effect of the composition of secondary serpentine or of mineral dissolution rates is minor. The results of this reactive transport modeling have proven useful to validate the conceptual models derived from field observations.

Nitrate reduction and its effects on trichloroethylene degradation by granular iron

Laboratory column experiments and reactive transport modeling were performed to evaluate the reduction of nitrate and its effects on trichloroethylene (TCE) degradation by granular iron. In addition to determining degradation kinetics of TCE in the presence of nitrate, the columns used in this study were equipped with electrodes which allowed for in situ measurements of corrosion potentials of the iron material. Together with Raman spectroscopic measurements the mechanisms of decline in iron reactivity were examined. The experimental results showed that the presence of nitrate resulted in an increase in corrosion potential and the formation of thermodynamically stable passive films on the iron surface which impaired iron reactivity. The extent of the decline in iron reactivity was proportional to the nitrate concentration. Consequently, significant decreases in TCE and nitrate degradation rates and migration of degradation profiles for both compounds occurred. Furthermore, the TCE degradation kinetics deviated from the pseudo-first-order model. The results of reactive transport modeling, which related the amount of a passivating iron oxide, hematite (α-Fe2O3), to the reactivity of iron, were generally consistent with the patterns of migration of TCE and nitrate profiles observed in the column experiments. More encouragingly, the simulations successfully demonstrated the differences in performances of three columns without changing model parameters other than concentrations of nitrate in the influent. This study could be valuable in the design of iron permeable reactive barriers (PRBs) or in the development of effective maintenance procedures for PRBs treating TCE-contaminated groundwater with elevated nitrate concentrations.

Hydrothermal Dissolution of Deeply Buried Cambrian Dolomite Rocks and Porosity Generation: Integrated with Geological Studies and Reactive Transport Modeling in the Tarim Basin, China

The burial dissolution of carbonate rocks has long been an interesting topic of reservoir geologists. Integrated with geological studies and reactive transport modeling, this study investigated the Cambrian dolomites that were buried at depths up to 8408 m and still preserved a large amount of unfilled dissolution vugs from the borehole TS1 in the northern Tarim Basin. Studies indicate that these vugs were formed in association with fault-channeled hydrothermal fluids from greater depth through “retrograde dissolution” as the fluid temperature dropped during upward migration. The reactive transport modeling results suggest an important control of the vertical permeability of wall-rock on fluid and temperature patterns which, in turn, would control the spatial distribution of dissolving-originated porosity. The hydrothermal dissolution mainly occurred in dolomite wall-rocks with higher vertical permeability (extensive development of tensional fractures and connected pore spaces), producing additional dissolved porosity there during deep burial. This study implicates the importance of multidisciplinary approaches for understanding the burial/hydrothermal dissolution of dolomite rocks and predicting favourable deep/ultradeep carbonate reservoirs.

Sediment chemistry and toxicity in Barnegat Bay, New Jersey: Pre- and post-Hurricane Sandy, 2012–13

Hurricane Sandy made landfall in Barnegat Bay, October, 29, 2012, damaging shorelines and infrastructure. Estuarine sediment chemistry and toxicity were investigated before and after to evaluate potential environmental health impacts and to establish post-event baseline sediment-quality conditions. Trace element concentrations increased throughout Barnegat Bay up to two orders of magnitude, especially north of Barnegat Inlet, consistent with northward redistribution of silt. Loss of organic compounds, clay, and organic carbon is consistent with sediment winnowing and transport through the inlets and sediment transport modeling results. The number of sites exceeding sediment quality guidance levels for trace elements tripled post-Sandy. Sediment toxicity post-Sandy was mostly unaffected relative to pre-Sandy conditions, but at the site with the greatest relative increase for trace elements, survival rate of the test amphipod decreased (indicating degradation). This study would not have been possible without comprehensive baseline data enabling the evaluation of storm-derived changes in sediment quality.

Low-Thrust Geostationary Transfer Orbit (LT2GEO) Radiation Environment and Associated Solar Array Degradation Modeling and Ground Testing

Low-thrust geostationary transfer orbits (LT2GEO) are found to offer significant low cost options thus making them very attractive for GEO missions. However, LT2GEOs increase the transfer orbit time from days to months, thereby causing a significant increase in the time that satellites traverse the most intense trapped particle radiation belts. This paper describes the LT2GEO radiation environment and provides some practical implications using new solar cell technologies and materials. New solar cell and coverglass testing protocols are established using Monte Carlo transport modeling and experimental results are given for Qioptiq CMG borosilicate coverglass.

Impacts of different plant functional types on ambient ozone predictions in the Seoul Metropolitan Areas (SMAs), Korea

Abstract. Plant functional type (PFT) distributions affect the results of biogenic emission modeling as well as O3 and particulate matter (PM) simulations using chemistry-transport models (CTMs). This paper analyzes the variations of both surface biogenic volatile organic compound (BVOC) emissions and O3 concentrations due to changes in the PFT distributions in the Seoul Metropolitan Areas, Korea. The Fifth-Generation NCAR/Pennsylvania State Meso-scale Model (MM5)/the Model of Emissions of Gases and Aerosols from Nature (MEGAN)/the Sparse Matrix Operator Kernel Emissions (SMOKE)/the Community Multiscale Air Quality (CMAQ) model simulations were implemented over the Seoul Metropolitan Areas in Korea to predict surface O3 concentrations for the period of 1 May to 31 June 2008. Starting from a performance check of CTM predictions, we consecutively assessed the effects of PFT area deviations on the MEGAN BVOC and CTM O3 predictions, and we further considered the basis of geospatial and statistical analyses. The three PFT data sets considered were (1) the Korean PFT, developed with Korea-specific vegetation database; (2) the CDP PFT, adopted from the community data portal (CDP) of US National Center for Atmospheric Research in the United States (NCAR); (3) MODIS PFT, reclassified from the NASA Terra and Aqua combined land cover products. Although the CMAQ performance check reveals that all of the three different PFT data sets are applicable choices for regulatory modeling practice, noticeable primary data (i.e., PFT and Leaf Area Index (LAI)) was observed to be missing in many geographic locations. Based on the assessed effect of such missing data on CMAQ O3 predictions, we found that this missing data can cause spatially increased bias in CMAQ O3. Thus, it must be resolved in the near future to obtain more accurate biogenic emission and chemistry transport modeling results. Comparisons of MEGAN biogenic emission results with the three different PFT data showed that broadleaf trees (BTs) are the most significant contributor, followed by needleleaf trees (NTs), shrub (SB), and herbaceous plants (HBs) to the total BVOCs. In addition, isoprene from BTs and terpene from NTs were recognized as significant primary and secondary BVOC species in terms of BVOC emissions distributions and O3-forming potentials in the study domain. A geographically weighted regression analysis with locally compensated ridge (LCR-GWR) with the different PFT data (δO3 vs. δPFTs) suggests that addition of BT, SB, and NT areas can contribute to O3 increase, whereas addition of an HB area contributes to O3 decrease in the domain. Assessment results of the simulated spatial and temporal changes of O3 distributions with the different PFT scenarios reveal that hourly and local impacts from the different PFT distributions on occasional inter-deviations of O3 are quite noticeable, reaching up to 13 ppb. The simulated maximum 1 h O3 inter-deviations between different PFT scenarios have an asymmetric diurnal distribution pattern (low in the early morning, rising during the day, peaking at 05:00 p.m., and decreasing during the night) in the study domain. Exponentially diverging hourly BVOC emissions and O3 concentrations with increasing ambient temperature suggest that the use of different PFT distribution data requires much caution when modeling (or forecasting) O3 air quality in complicated urban atmospheric conditions in terms of whether uncertainties in O3 prediction results are expected to be mild or severe.