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At least 1,297 records · Page 72
All sourcesNASA NTRSDOE OSTI
NASA NTRS2012

Hydrostatic Hyperbaric Chamber Ventilation System

The hydrostatic hyperbaric chamber (HHC) represents the merger of several technologies in development for NASA aerospace applications, harnessed to directly benefit global health. NASA has significant experience developing composite hyperbaric chambers for a variety of applications. NASA also has researched the application of water-filled vessels to increase tolerance of acceleration forces. The combination of these two applications has resulted in the hydrostatic chamber, which has been conceived as a safe, affordable means of making hyperbaric oxygen therapy (HBOT) available in the developing world for the treatment of a variety of medical conditions. Specifically, HBOT is highly-desired as a possibly curative treatment for Buruli Ulcer, an infectious condition that afflicts children in sub-Saharan Africa. HBOT is simply too expensive and too dangerous to implement in the developing world using standard equipment. The HHC technology changes the paradigm. The HHC differs from standard hyperbaric chambers in that the majority of its volume is filled with water which is pressurized by oxygen being supplied in the portion of the chamber containing the patient s head. This greatly reduces the amount of oxygen required to sustain a hyperbaric atmosphere, thereby making the system more safe and economical to operate. An effort was taken to develop an HHC system to apply HBOT to children that is simple and robust enough to support transport, assembly, maintenance and operation in developing countries. This paper details the concept for an HHC ventilation and pressurization system to provide controlled pressurization and adequate washout of carbon dioxide while the subject is enclosed in the confined space during the administration of the medical treatment. The concept took into consideration operational complexity, safety to the patient and operating personnel, and physiological considerations. The simple schematic, comprised of easily acquired commercial hardware, supports sustainability.

Sarguisingh, Miriam J.↗
DOE OSTI2022

Plasma‐driven biocatalysis: In situ hydrogen peroxide production with an atmospheric pressure plasma jet increases the performance of OleT JE when compared to adding the same molar amount of hydrogen peroxide in bolus

Abstract Enzymes like fatty acid peroxygenase OleT JE are desirable enzymes for the industry. While they require inexpensive hydrogen peroxide for activity, the same hydrogen peroxide also causes overoxidation of their reactive heme center. Here, we generate hydrogen peroxide slowly in situ using the Cooperation in Science and Technology (COST)‐Jet, an atmospheric pressure plasma jet, to avoid overoxidizing OleT JE . The COST‐Jet was operated in helium with a water admixture to provide hydrogen peroxide for OleT JE activity. This helium/water admixture produced the highest enzyme turnover numbers after 2 min of treatment. These turnover numbers were even superior to using an equimolar amount of hydrogen peroxide to treat the enzymes exogenously, showing that this plasma source can provide a reliable amount of reaction mediator to support OleT JE activity.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Precipitation and nitrogen application stimulate soil nitrous oxide emission

Precipitation and nitrogen (N) fertilization are the two most important drivers for soil nitrous oxide (N 2 O) emission. However, the effects of changes in N fertilization and precipitation patterns (i.e., precipitation intensity and frequency) on N 2 O emissions in agricultural fields are still unclear. In this study, we simulated soil N 2 O emission under different precipitation patterns (6 precipitation intensities, and 12 precipitation frequencies by either merging or splitting precipitation events) and N fertilization rates (low, typical, and high N fertilization) in a cornfield using the DeNitrification-DeComposition model. The model was parameterized and validated using meteorological data and N experimental measurements in Nashville, Tennessee, USA. Results showed that soil water filled pore space (WFPS) and simulated soil N 2 O emission increased as precipitation intensity increased. Less frequent but high intensity precipitation treatments reduced the soil WFPS by 25.2% and stimulated soil N 2 O emission by 45.3%, while more frequent but low intensity precipitation treatments increased soil WFPS by 9.0% and reduced soil N 2 O emission by 23.9%. Compared to typical N fertilization, the sensitivity of soil N 2 O emission to precipitation was higher under high N than low N fertilization treatments, and the response ratios were 50.0% and 40.1%, respectively. There was significant interactive effect of precipitation intensity and N fertilization on soil N 2 O emission. Furthermore, these findings improved our understanding of precipitation and N impacts on soil N 2 O emissions and provided useful knowledge for irrigation and N fertilizer management in agriculture to mitigate greenhouse gas emissions.

54 ENVIRONMENTAL SCIENCES↗
DOE OSTI2022

The effects of SO 2 exposure on three-way catalysts for passive SCR operation

We report efficient lean-burn gasoline engines cannot employ traditional three-way catalysts (TWCs) to control NO X emissions due to excess oxygen. Passive selective catalytic reduction (pSCR) is a process designed to control NOx by generating NH 3 over the TWC during fuel-rich operation, storing it on a downstream SCR, and then converting NOx during fuel-lean operation. This work is focused on studying sulfur effects on this promising strategy. Two hydrothermally-aged commercial catalysts were studied for their effectiveness in the presence of SO 2 : a Pd-based TWC and a TWC with NO X storage. The sulfated samples were evaluated in a flow reactor under pSCR conditions and with targeted reactions. SO 2 inhibited the water gas shift and steam reforming reactions, decreasing (but not eliminating) NH 3 production; however, initial activity is recoverable after a simple thermal treatment at 650 °C. This work will prove valuable in understanding, mitigating, and even reversing the effects of SO 2 inhibition on real pSCR systems.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Controlled plasma–droplet interactions: a quantitative study of OH transfer in plasma–liquid interaction

Plasmas in contact with liquids are a rich source of OH radicals and have been extensively studied in the last decade to leverage the ability to generate chemically reactive species in gas phase plasmas to decompose organics. Multiphase transfer of OH radicals is highly transport limited and to overcome transport limits, the plasma activation of aerosols, small liquid droplets, interspersed in the plasma has been proposed. In this work, we report a combined experimental and modeling study of a controlled plasma–droplet interaction experiment using a diffuse RF glow discharge in He + 0.2% H 2 O with detailed plasma diagnostics, ex situ analysis of the plasma-induced chemistry in the droplet containing formate, droplet trajectory and size measurements. This enables a quantitative study of the reactivity transfer of OH from the gas phase plasma to the liquid phase and how its diffusion limitations impact formate decomposition in the water droplet. For a droplet with a diameter of 36 μm, we observed 50% reduction in formate concentration in the droplets after plasma treatment for droplet residence times in the plasma of ~10 ms. These short droplet residence times in the plasma allow in some cases for droplet size reductions of ~5% in spite gas temperatures of 360 K. A one-dimensional reaction–diffusion model was used to calculate the OH transport and formate oxidation inside the droplet and was able to predict the conversion of formate by plasma in a droplet without any fitting parameters. The model further shows that formate conversion is dominated by near-interfacial reactions with OH radicals and is limited by diffusion of formate in the droplet. Here, the results show that a controlled plasma–micro-droplet reactor as reported in this study might be an excellent tool for detailed quantitative plasma–liquid interaction studies.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2021

Minnesota peat viromes reveal terrestrial and aquatic niche partitioning for local and global viral populations

Abstract Background Peatlands are expected to experience sustained yet fluctuating higher temperatures due to climate change, leading to increased microbial activity and greenhouse gas emissions. Despite mounting evidence for viral contributions to these processes in peatlands underlain with permafrost, little is known about viruses in other peatlands. More generally, soil viral biogeography and its potential drivers are poorly understood at both local and global scales. Here, 87 metagenomes and five viral size-fraction metagenomes (viromes) from a boreal peatland in northern Minnesota (the SPRUCE whole-ecosystem warming experiment and surrounding bog) were analyzed for dsDNA viral community ecological patterns, and the recovered viral populations (vOTUs) were compared with our curated PIGEON database of 266,125 vOTUs from diverse ecosystems. Results Within the SPRUCE experiment, viral community composition was significantly correlated with peat depth, water content, and carbon chemistry, including CH 4 and CO 2 concentrations, but not with temperature during the first 2 years of warming treatments. Peat vOTUs with aquatic-like signatures (shared predicted protein content with marine and/or freshwater vOTUs) were significantly enriched in more waterlogged surface peat depths. Predicted host ranges for SPRUCE vOTUs were relatively narrow, generally within a single bacterial genus. Of the 4326 SPRUCE vOTUs, 164 were previously detected in other soils, mostly peatlands. None of the previously identified 202,371 marine and freshwater vOTUs in our PIGEON database were detected in SPRUCE peat, but 0.4% of 80,714 viral clusters (VCs, grouped by predicted protein content) were shared between soil and aquatic environments. On a per-sample basis, vOTU recovery was 32 times higher from viromes compared with total metagenomes. Conclusions Results suggest strong viral “species” boundaries between terrestrial and aquatic ecosystems and to some extent between peat and other soils, with differences less pronounced at higher taxonomic levels. The significant enrichment of aquatic-like vOTUs in more waterlogged peat suggests that viruses may also exhibit niche partitioning on more local scales. These patterns are presumably driven in part by host ecology, consistent with the predicted narrow host ranges. Although more samples and increased sequencing depth improved vOTU recovery from total metagenomes, the substantially higher per-sample vOTU recovery after viral particle enrichment highlights the utility of soil viromics.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2024

Development and Commercialization of a Nanosegrated Oxygen Evolution Reaction Electrocatalyst (CRADA)

This collaborative project leverages advanced characterization tools, catalyst treatment and electrochemical testing capabilities at LBNL to help commercialize a bimetallic nanosegrated catalysts for oxygen evolution reaction in proton-exchange membrane water electrolyzers. This project also has three industrial partners who are involved in catalyst scale-up synthesis, large electrode fabrication and large electrode electrochemical testing. This project investigates a broad range of topics including electrocatalysis, ink rheology and electrode fabrication and testing. This knowledge could help bridge the performance and durability gap from laboratory-developed materials (such as electrocatalysts) to applications in commercial devices. The research results also bring fundamental understanding of possible degradation mechanisms that occur under extremely oxidative potentials including material and morphological changes. The project will help accelerate the deployment of proton-exchange membrane water electrolyzers. The public benefits could include creating jobs and increasing public awareness of potential clean technologies for green hydrogen production. Ultimately, the project will help national wide effort of flighting climate change and achieving carbon neutrality by 2050.

30 DIRECT ENERGY CONVERSION↗
NASA NTRS1972

Testing to determine the vacuum-ultraviolet degradation rate of thermal control coatings

Samples of S-13G that had been exposed to the salt air environment of Cape Kennedy, Florida were irradiated with simulated solar ultraviolet radiation after various cleaning treatments. In both of the the tests conducted two of the salt air exposed samples were not cleaned, two were lightly cleaned with water and detergent (i.e. rinsed), and two were vigorously scrubbed. Several other white thermal control coatings were also irradiated. The solar absorptance values of these coatings before and as a result of the ultraviolet irradiation are reported for exposure levels up to approximately 2000 ESH.

Gilligan, J. E.↗
NASA NTRS1975

CARETS: A prototype regional environmental information system. Volume 11: Potential usefulness of CARETS data for environmental impact assessment

The National Environmental Policy Act of 1969 requires that Federal agencies prepare environmental impact statements (EIS) for all proposed actions that significantly affect the quality of the environment. The EIS builds a predictive model of beneficial or adverse changes resulting from an action. Environmental impact statement preparation requires identification of environmental, social, and economic conditions likely to change and also requires prediction of intensity and spatial dimensions of changes. The Central Atlantic Regional Ecological Test Site (CARETS) project has produced land use data that can be of value for such assessment. To ascertain the types of proposed actions requiring EIS's, all EIS's prepared for proposed actions in the test site between January 1970 and June 1974 were reviewed. The actions were divided into seven categories: (1) construction of transportation and communication facilities; (2) construction of power plant, powerline, and fuel line facilities; (3) urban renewal, new town development projects, and multistory building construction; (4) construction of facilities for watershed protection and development;, (5) construction of waste treatment and disposal facilities (6) maintenance dredging, navigation improvements, and beach erosion control and replenishment projects; and (7) establishing or enhancing land and water conservation areas. Examples of actions from each category were selected for more detailed study. In view of the types of projects being proposed, an approach to environmental impact assessment using land use and water data as central inputs was recommended. The viability of such an approach as well as other approaches depends upon the availability of quantitative data such as those produced by the CARETS project.

Environmental impact assessment↗
NASA NTRS1993

The role of the geothermal gradient in the emplacement and replenishment of ground ice on Mars

Knowledge of the mechanisms by which ground ice is emplaced, removed, and potentially replenished, are critical to understanding the climatic and hydrologic behavior of water on Mars, as well as the morphologic evolution of its surface. Because of the strong temperature dependence of the saturated vapor pressure of H2O, the atmospheric emplacement or replenishment of ground ice is prohibited below the depth at which crustal temperatures begin to monotonically increase due to geothermal heating. In contrast, the emplacement and replenishment of ground ice from reservoirs of H2O residing deep within the crust can occur by at least three different thermally-driven processes, involving all three phases of water. In this regard, Clifford has discussed how the presence of a geothermal gradient as small as 15 K/km can give rise to a corresponding vapor pressure gradient sufficient to drive the vertical transport of 1 km of water from a reservoir of ground water at depth to the base of the cryosphere every 10(exp 6) - 10(exp 7) years. This abstract expands on this earlier treatment by considering the influence of thermal gradients on the transport of H2O at temperatures below the freezing point.

Clifford, Stephen M.↗
NASA NTRS2007

Persistent Seroconversion after Accidental Eye Exposure to Calcifying Nanoparticles

Biosafety of nanomaterials has attracted much attention recently. We report here a case where accidental human eye exposure to biogenic nanosized calcium phosphate in the form of calcifying nanoparticles (CNP) raised a strong IgG immune response against proteins carried by CNP. The antibody titer has persisted over ten years at the high level. The IgG was detected by ELISA using CNPs propagated in media containing bovine and human serum as antigen. The exposure incident occurred to a woman scientist (WS) at a research laboratory in Finland at 1993. CNP, also termed "nanobacteria", is a unique self-replicating agent that has not been fully characterized and no data on biohazards were available at that time. Before the accident, her serum samples were negative for both CNP antigen and anti-CNP antibody using specific ELISA tests (Nanobac Oy, Kuopio, Finland). The accident occurred while WS was harvesting CNP cultures. Due to a high pressure in pipetting, CNP pellet splashed into her right eye. Both eyes were immediately washed with water and saline. The following days there was irritation and redness in the right eye. These symptoms disappeared within two weeks without any treatment. Three months after the accident, blood and urine samples of WS were tested for CNP cultures (2), CNP-specific ELISA tests, and blood cell counts. Blood cell counts were normal, CNP antigen and culture tests were negative. A high IgG anti-CNP antibody titer was detected (see Figure). The antibodies of this person have been used thereafter as positive control and standard in ELISA manufacturing (Nano-Sero IgG ELISA, Nanobac Oy, Kuopio, Finland).

Ciftcioglu, Neva↗
NASA NTRS2000

GCSS Cirrus Parcel Model Comparison Project

The Cirrus Parcel Model Comparison Project, a project of GCSS Working Group on Cirrus Cloud Systems (WG2), involves the systematic comparison of current models of ice crystal nucleation and growth for specified, typical, cirrus cloud environments. The goal of this project is to document and understand the factors resulting in significant inter-model differences. The intent is to foment research leading to model improvement and validation. In Phase 1 of the project reported here, simulated cirrus cloud microphysical properties are compared for situations of "warm" (-40 C) and "cold" (-60 C) cirrus subject to updrafts of 4, 20 and 100 cm/s, respectively. Five models participated. These models employ explicit microphysical schemes wherein the size distribution of each class of particles (aerosols and ice crystals) is resolved into bins. Simulations are made including both homogeneous and heterogeneous ice nucleation mechanisms. A single initial aerosol population of sulfuric acid particles is prescribed for all simulations. To isolate the treatment of the homogeneous freezing (of haze drops) nucleation process, the heterogeneous nucleation mechanism is disabled for a second parallel set of simulations. Qualitative agreement is found for the homogeneous-nucleation-only simulations, e.g., the number density of nucleated ice crystals increases with the strength of the prescribed updraft. However, non-negligible quantitative differences are found. Detailed analysis reveals that the homogeneous nucleation formulation, aerosol size, ice crystal growth rate (particularly the deposition coefficient), and water vapor uptake rate are critical components that lead to differences in predicted microphysics. Systematic bias exists between results based on a modified classical theory approach and models using an effective freezing temperature approach to the treatment of nucleation. Each approach is constrained by critical freezing data from laboratory studies, but each includes assumptions that can only be justified by further laboratory data. Consequently, it is not yet clear if the two approaches can be made consistent. Large haze particles may deviate considerably from equilibrium size in moderate to strong updrafts (20-100 cm/s) at -60 C when the commonly invoked equilibrium assumption is lifted. The resulting difference in particle-size-dependent solution concentration of haze particles may significantly affect the ice nucleation rate during the initial nucleation interval. The uptake rate for water vapor excess by ice crystals is another key component regulating the total number of nucleated ice crystals. This rate, the product of ice number concentration and ice crystal diffusional growth rate, which is sensitive to the deposition coefficient when ice particles are small, partially controls the peak nucleation rate achieved in an air parcel and the duration of the active nucleation time period. The effects of heterogeneous nucleation are most pronounced in weak updraft situations. Vapor competition by the nucleated (heterogeneous) ice crystals limits the achieved ice supersaturation and thus suppresses the contribution of homogeneous nucleation. Correspondingly, ice crystal number density is markedly reduced. Definitive laboratory and atmospheric benchmark data are needed for the heterogeneous nucleation process. Inter-model differences are correspondingly greater than in the case of the homogeneous nucleation process acting alone.

Lin, Ruei-Fong↗
DOE OSTI2021

Ultraviolet radiation pre-treatment of wastewater, improving its utility for algal cultivation

The present invention relates to a process of remediating wastewaters, preferably agricultural wastewaters resulting from animal production or contained animal feeding operation sites. The water is treated to promote assimilation of nutrients into algal biomass, which can be harvested and sold, and the resultant wastewater is then purified. According to the invention, short wavelength UV radiation (less than 280 nm wavelength) is used to pretreat wastewater, with the dose determined by absorbance of the water, not by bacterial load. Pretreated water exhibits changes in chromophoric dissolved organic matter that allows for improved and increased algae production by as much as 88%.

Feris, Kevin↗
NASA NTRS1999

Effects of CO2 on stomatal conductance: do stomata open at very high CO2 concentrations?

Potato and wheat plants were grown for 50 d at 400, 1000 and 10000 micromoles mol-1 carbon dioxide (CO2). and sweetpotato and soybean were grown at 1000 micromoles mol-1 CO2 in controlled environment chambers to study stomatal conductance and plant water use. Lighting was provided with fluorescent lamps as a 12 h photoperiod with 300 micromoles m-2 s-1 PAR. Mid-day stomatal conductances for potato were greatest at 400 and 10000 micromoles mol-1 and least at 1000 micromoles mol-1 CO2. Mid-day conductances for wheat were greatest at 400 micromoles mol-1 and least at 1000 and 10000 micromoles mol-1 CO2. Mid-dark period conductances for potato were significantly greater at 10000 micromoles mol-1 than at 400 or 1000 micromoles mol-1, whereas dark conductance for wheat was similar in all CO2 treatments. Temporarily changing the CO2 concentration from the native 1000 micromoles mol-1 to 400 micromoles mol-1 increased mid-day conductance for all species, while temporarily changing from 1000 to 10000 micromoles mol-1 also increased conductance for potato and sweetpotato. Temporarily changing the dark period CO2 from 1000 to 10000 micromoles mol-1 increased conductance for potato, soybean and sweetpotato. In all cases, the stomatal responses were reversible, i.e. conductances returned to original rates following temporary changes in CO2 concentration. Canopy water use for potato was greatest at 10000, intermediate at 400, and least at 1000 micromoles mol-1 CO2, whereas canopy water use for wheat was greatest at 400 and similar at 1000 and 10000 micromoles mol-1 CO2. Elevated CO2 treatments (i.e. 1000 and 10000 micromoles mol-1) resulted in increased plant biomass for both wheat and potato relative to 400 micromoles mol-1, and no injurious effects were apparent from the 10000 micromoles mol-1 treatment. Results indicate that super-elevated CO2 (i.e. 10000 micromoles mol-1) can increase stomatal conductance in some species, particularly during the dark period, resulting in increased water use and decreased water use efficiency.

NASA Discipline Life Support Systems↗
DOE OSTI2022

Milestone 1.2.11: H 2 Production from Surrogate Non-Native Corrosion Plumes on Aluminum 6061-T6 Fuel Cladding Surrogates

Thick, localized, “non-native” corrosion plumes have been identified on Advanced Test Reactor fuel elements, raising concern on their impact on the radiolytic formation of molecular hydrogen gas (H 2 ) from aluminum-clad spent nuclear fuel (ASNF) under proposed extended (> 50 years) dry storage conditions. Here, we report our findings on H 2 generation from the gamma irradiation (up to 52 MGy) of surrogate “non-native” corrosion plume coupons: ambient-temperature-corroded (~350 days in water) aluminum alloy 6061 (AA6061) coupons in helium gas environments with ~0% added relative humidity. Additionally, we provide a comparison of proposed ASNF drying techniques— vacuum drying only, vacuum drying + 100 °C for 4 hr, and vacuum drying + 220 °C for 4 hr—on the yield of H 2 from these surrogate systems. The presented data indicates that similar amounts of H 2 (~2 × 10–3 µmol J–1) are formed from gamma irradiated AA6061 coupons corroded under different temperature regimes, i.e., ambient/350 days vs. 90 C/30 days. These findings validate current, complimentary modelling predictions based on high-temperature-corrosion irradiation data only. Further, the application of a heat treatment procedure (100 and 220 °C), in conjunction with vacuum drying, accelerated the rate at which a steady-state H 2 yield was attained, in comparison to vacuum only, due to the removal of H 2 precursors in the form of adsorbed waters. Interestingly, within the confidence limits of our measurements, negligible difference in total H 2 yield was found between the two investigated heat treatment procedures.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗
DOE OSTI2020

Drought and plant litter chemistry alter microbial gene expression and metabolite production

Drought represents a significant stress to microorganisms and is known to reduce microbial activity and organic matter decomposition in Mediterranean ecosystems. However, we lack a detailed understanding of the drought stress response of microbial decomposers. Here we present metatranscriptomic and metabolomic data on the physiological response of in situ microbial communities on plant litter to long-term drought in Californian grass and shrub ecosystems. We hypothesised that drought causes greater microbial allocation to stress tolerance relative to growth pathways. In grass litter, communities from the decade-long ambient and reduced precipitation treatments had distinct taxonomic and functional profiles. The most discernable physiological signatures of drought were production or uptake of compatible solutes to maintain cellular osmotic balance, and synthesis of capsular and extracellular polymeric substances as a mechanism to retain water. The results show a clear functional response to drought in grass litter communities with greater allocation to survival relative to growth that could affect decomposition under drought. In contrast, communities on chemically more diverse and complex shrub litter had smaller physiological differences in response to long-term drought but higher investment in resource acquisition traits across precipitation treatments, suggesting that the functional response to drought is constrained by substrate quality. Our findings suggest, for the first time in a field setting, a trade off between microbial drought stress tolerance, resource acquisition and growth traits in plant litter microbial communities.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2021

SPRUCE Outflow Chemistry Data for Experimental Plots Beginning in 2016

This data set includes the chemistry of outflow waters in the SPRUCE experiment plots located in the S1 bog of the USDA Forest Service Marcell Experimental Forest (MEF) in northern Minnesota, 40 km north of Grand Rapids. These data are post-treatment data from the warming and elevated carbon dioxide (CO2) treatments associated with the SPRUCE experiment. There are ten experimental plots in SPRUCE: five temperature treatments (+0, +2.25, +4.5, +6.75, +9°C) at ambient CO2, and the same five temperature treatments at elevated CO2 (+500 ppm). Sample collection and analyses started in March of 2016 and will continue for the duration of the experiment. Samples were analyzed for pH, specific conductivity, anion concentrations (chloride, sulfate), cation concentrations (calcium, potassium, magnesium, sodium, aluminum, iron, manganese, silicon, strontium), nutrient concentrations (ammonium, nitrate, soluble reactive phosphorus, total nitrogen, total phosphorus), and total organic carbon (TOC) concentrations. Subsets of the samples have been analyzed for natural-abundance stable isotopes of water (δ18O-H2O and δD-H2O), dissolved carbon dioxide (δ13C-CO2), and dissolved methane (δ13C-CH4), and concentrations of total mercury (Thg), methylmercury (MeHg), ferrous iron (Fe2+), ferric iron (Fe3+), dissolved inorganic carbon (DIC), and dissolved methane (CH4).

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS2010

Pilot Study for UVA-LED Disinfection of Escherichia coli in Water for Space and Earth Applications

To test the efficacy of UVA-LED disinfection, a solution of Escherichia coli was pumped through a modified drip flow reactor at a flow rate of 1 ml/min. The experiment was conducted in a controlled environment chamber to ensure that temperature did not cause disinfection. The reactor featured three wells with different treatments: UVA-LED irradiation, UVA-LEDs with Ti02, and UVA-LEDs with nanosilver. Samples from each well were taken throughout a 340 hour period, inactivated, assayed, and analyzed for E. coli disinfection. Results of the duplicate experiments indicated longer exposure times are needed for UVA-LED disinfection of E. coli in water. Further research would consider a longer sampling period and different test conditions, such as increased contact area and various flow rates.

Ragolta, Carolina↗