Performance of a Brayton power system with a space type radiator

Test results of an experimental investigation to measure Brayton engine performance while operating at the sink temperatures of a typical low earth orbit are presented. The results indicate that the radiator area was slightly oversized. The steady state and transient responses of the power system to the sink temperatures in orbit were measured. During the orbital operation, the engine did not reach the steady state operation of either sun or shade conditions. The alternator power variation during orbit was + or - 4 percent from its mean value of 9.3 kilowatts

Potassium condensing tests of horizontal multitube convective and radiative condensers operating at vapor temperatures of 1250 deg to 1500 deg F

Potassium condensing tests of horizontal multitube convective and radiative condenser operating at vapor temperature

Field and Forage Crop Fertilization in the Trans-Pecos and Edwards Plateau Regions.

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Flow, Salts, and Trace Elements in the Rio Grande: A Review

There are increasing concerns that water quality of the Rio Grande (or Rio Bravo) may be deteriorating mainly due to the recent expansion of the maquilas program and associated population relocation into the Border area. This review was conducted to assess the state of flow, salts, and trace elements in the Texas/Mexico portion of the Rio Grande and its tributaries. The data used included published and unpublished reports by federal, state, and some local sources. The total inflow into the Texas/Mexico portion of the Rio Grande (El Paso to Brownsville) since 1969 has averaged 4.51 billion m3 (3.65 million acre-ft) annually. Approximately 60 percent of the inflow is estimated to originate from the Mexican side. The largest flow of the Rio Grande occurs below Falcon Dam at an annual rate of 3.0 billion m3 (2.43 million acre-ft). No significant yearly trend of annual flow was detected either by a linear regression or the autocorrelation analysis for the last 21 years. The Rio Conchos, the Rio San Juan, and the Rio Salado are the major tributaries from the Mexican side and account, respectively, for 20, 10, and 10 percent of the total inflow into the Rio Grande. The Devils River and the Pecos River are two of the major tributaries from Texas and account, respectively, for 7.8 and 6.1 percent of the total inflow into the Rio Grande. The highest salinity of the Rio Grande occurs in the section from Fort Quitman to Presidio (2000 to 5000 mg L-1) and at the Pecos River (2000 to 4000 mg L-1). Salinity of the Rio Grande decreases below Presidio due to the confluence of the Rio Conchos, and it currently averages 860 mg L-1 at Amistad International Reservoir. However, salinity in this segment of the Rio Grande is increasing at an annual rate of 15 to 18 mg L-1. If these trends continue, salinity at Amistad Reservoir will exceed 1000 mg L-1 by the year 2000 or will become twice the salinity level of 1969 by 2004. Salinity below Amistad has been increasing at lower rates (9 to 10 mg L-1). Salinity of the Rio Conchos, the Rio San Juan, and the Pecos River has also been increasing at an annual rate of 8.5, 21, and 38 mg L-1, respectively. Salinity is flow-dependent at the upper reach and at Brownsville. Elsewhere, salinity is largely independent of the annual flow and has not yet attained the steady state. Sodicity of the main flow of the Rio Grande is at the range where soil particle dispersion begins (SAR of 3 to 4), and that of saline tail water below Fort Quitman and the Pecos River well exceeds the stability guideline. The sodicity of the Rio Grande water usually increases with increasing salinity, and the sodium adsorption ratio reaches close to 10. The annual salt inflow into the Rio Grande between Fort Quitman and Amistad Dam is estimated at 1.84 million tons, and that between Amistad and Falcon Dam at 1.17 million tons. Saline tail water of the Federal Middle Rio Grande project and the Pecos River contributes 48 percent of the salt load to the Rio Grande above Amistad Dam, while contributing only 21 percent to the flow. These two streams plus the Rio Salado contribute 50 percent of the salt load of the Rio Grande above Falcon Dam, while contributing 26 percent to the flow of the Rio Grande. Salts have been accumulating, especially in the segments above Amistad Dam. Existing database for trace elements is rather sketchy and is often inaccurate for some elements (e.g., Hg, Ag, and Cd). Nonetheless, most data indicate that dissolved concentrations of trace elements measured for the last 10 years at six monitoring stations along the main flow of the Rio Grande are low enough to meet the EPA primary drinking water standard, the proposed EPA criteria for livestock water supply, as well as guidelines for irrigation uses. However, dissolved concentrations of Cu, Pb, Hg and Ag often exceed the EPA chronic criteria for aquatic species protection, which are considerably more stringent than those for drinking water. Elevated levels of dissolved Hg concentrations are found in the upper reach (Elephant Butte down to Presidio) and elevated levels of dissolved Cu, Pb and V in salt marshes of the Lower Rio Grande. The concentrations of Cd, Cu, and Cr in pore water of the sediments in the upper reach appear to be many times higher than those in free water. The concentrations of many metals in fish samples collected from various locations along the Rio Grande often exceed the 85th national percentile established by the U.S. Fish and Wildlife Service. There is, however, no indications of Se problems along the Rio Grande. With few exceptions, the concentrations of total recoverable metals found in the sediment samples from the Rio Grande main stream are below or at the average values established for soil samples from the western states, except for Hg and Pb. Acid digestible contents of metals in sediments appear to be poorly correlated with dissolved metals or the metal concentrations in fish. The concentration of acid-digestible trace elements (Zn, Cu, Cd, Pb, Ni, Cr, and V) in soil samples from irrigated fields in the El Paso and the Juarez Valleys show some indications of Cu, Pb, and Zn accumulation. Even so, the levels of these metals are well below toxic levels for plant growth or for animal health concerns. The alkaline nature of the Rio Grande seems to help maintain relatively low dissolved concentrations of metals in water, but metals are probably accumulating in soils and sediments. Overall, this review indicates salts to be the major constraint for full utilization of water resources in the Rio Grande and that salinity is steadily increasing, especially above Amistad Dam. In these areas, salinity of the Rio Grande already exceeds the primary drinking water standard as well as the guidelines for production of high value horticultural crops. The continuing increase in salinity of Amistad Reservoir is of a special concern, as it may exceed the primary drinking water standard by as early as the year 2000 and could adversely affect high value crop production in the Lower Rio Grande. Trace element problems in the Rio Grande are sporadic and do not seem to be wide-spread at present, except from the view of aquatic species protection. There is a need to carry out a detailed salinity projection analysis, and to improve the accuracy of trace element monitoring and assessment of bioavailability indices for various ecosystems, especially in aquatic systems. Future research should also include water management options which target reuse of saline drainage water and disposal of wastewater away from the primary waterway of the Rio Grande to curtail salinization and trace element accumulation

Comparison of free tropospheric western Pacific air mass classification schemes for the PEM-West A experiment

During September/October 1991, NASA's Global Tropospheric Experiment (GTE) conducted an airborne field measurement program (PEM-West A) in the troposphere over the western Pacific Ocean. In this paper we describe and use the relative abundance of the combustion products C2H2 and CO to classify air masses encountered during PEM-West A based on the degree that these tracers were processed by the combined effects of photochemical reactions and dynamical mixing (termed the degree of atmospheric processing). A large number of trace compounds (e.g., C2H6, C3H8, C6H6, NOy, and O3) are found to be well correlated with the degree of atmospheric processing that is reflected by changes in the ratio of C2H2/CO over the range of values from ∼0.3 to 2.0 (parts per trillion volume) C2H2/ (parts per billion volume) CO. This C2H2/CO-based classification scheme is compared to model simulations and to two independent classification schemes based on air mass back-trajectory analyses and lidar profiles of O3 and aerosols. In general, these schemes agree well, and in combination they suggest that the functional dependence that other observed species exhibit with respect to the C2H2/CO atmospheric processing scale can be used to study the origin, sources, and sinks of trace species and to derive several important findings. First, the degree of atmospheric processing is found to be dominated by dilution associated with atmospheric mixing, which is found to primarily occur through the vertical mixing of relatively recent emissions of surface layer trace species. Photochemical reactions play their major role by influencing the background concentrations of trace species that are entrained during the mixing (i.e., dilution) process. Second, a significant noncontinental source(s) of NO (and NOx) in the free troposphere is evident. In particular, the enhanced NO mixing ratios that were observed in convected air masses are attributed to either emissions from lightning or the rapid recycling of NOy compounds. Third, nonsoluble trace species emitted in the continental boundary layer, such as CO and hydrocarbons, are vertically transported to the upper troposphere as efficiently as they are to the midtroposphere. In addition, the mixing ratios of CO and hydrocarbons in the upper troposphere over the western Pacific may reflect a significant contribution from northern hemisphere land areas other than Asia. Finally, we believe that these results can be valuable for the quantitative evaluation of the vertical transport processes that are usually parameterized in models. Copyright 1996 by the American Geophysical Union

Characterization of the chemical signatures of air masses observed during the PEM experiments over the western Pacific

Extensive observations of tropospheric trace species during the second NASA Global Tropospheric Experiment Western Pacific Exploratory Mission (PEM-West B) in February-March 1994 showed significant seasonal variability in comparison with the first mission (PEM-West A), conducted in September-October 1991. In this study we adopt a previously established analytical method, i.e., the ratio C2H2/CO as a measure of the relative degree of atmospheric processing, to elucidate the key similarities and variations between the two missions. In addition, the C2H2/CO ratio scheme is combined with the back-trajectory-based and the LIDAR-based air mass classification schemes, respectively, to make in-depth analysis of the seasonal variation between PEM-West A and PEM-West B (hereinafter referred to as PEM-WA and PEM-WB). A large number of compounds, including long-lived NMHCs, CH4, and CO2, are, as expected, well correlated with the ratio C2H2/CO. In comparison with PEM-WA, a significantly larger range of observed C2H2/CO values at the high end for the PEM-WB period indicates that the western Pacific was more impacted by "fresher" source emissions, i.e., faster or more efficient continental outflow. As in the case of PEM-WA, the C2H2/CO scheme complements the back-trajectory air mass classification scheme very well. By combining the two schemes, we found that the atmospheric processing in the region is dominated by atmospheric mixing for the trace species analyzed. This PEM-WB wintertime result is similar to that found in PEM-WA for the autumn. In both cases, photochemical reactions are found to play a significant role in determining the background mixing ratios of trace gases, and in this way the two processes are directly related and dependent upon each other. This analysis also indicates that many of the upper tropospheric air masses encountered over the western Pacific during PEM-WB may have had little impact from eastern Asia's continental surface sources. NOx mixing ratios were significantly enhanced during PEM-WB when compared with PEM-WA, in the upper troposphere's more atmospherically processed air masses. These high levels of NOx resulted in a substantial amount of photochemical production of O3. A lack of corresponding enhancements in surface emission tracers strongly implies that in situ atmospheric sources such as lightning are responsible for the enhanced upper tropospheric NOx. The similarity in NOx values between the northern (higher air traffic) and southern continental air masses together with the indications of a large seasonal shift suggests that aircraft emissions are not the dominant source. However, photochemical recycling cannot be ruled out as this in situ source of NOx. Copyright 1999 by the American Geophysical Union

An assessment of western North Pacific ozone photochemistry based on springtime observations from NASA's PEM-West B (1994) and TRACE-P (2001) field studies

The current study provides a comparison of the photochemical environments for two NASA field studies focused on the western North Pacific (PEM-West-B (PWB) and TRACE-P (TP)). These two studies were separated in calendar time by approximately 7 years. Both studies were carried out under springtime conditions, with PWB being launched in 1994 and TP being deployed in 2001 (i.e., 23 February - 15 March 1994 and 10 March-15 April 2001, respectively). Because of the 7-year time separation, these two studies presented a unique scientific opportunity to assess whether evidence could be found to support the Department of Energy\u27s projections in 1997 that increases in anthropogenic emissions from East Asia could reach 5%/yr. Such projections would lead one to the conclusion that a significant shift in the atmospheric photochemical properties of the western North Pacific would occur. To the contrary, the findings from this study support the most recent emission inventory data [Streets et al., 2003] in that they show no significant systematic trend involving increases in any O3 precursor species and no evidence for a significant shift in the level of photochemical activity over the western North Pacific. This conclusion was reached in spite of there being real differences in the concentration levels of some species as well as differences in photochemical activity between PWB and TP. However, nearly all of these differences were shown to be a result of a near 3-week shift in TP\u27s sampling window relative to PWB, thus placing it later in the spring season. The photochemical enhancements seen during TP were most noticeable for latitudes in the range of 25-45°N. Most important among these were increases in J(O1D), OH, and HO2 and values for photochemical ozone formation and destruction, all of which were typically two times larger than those calculated for PWB. A comparison of these airborne results with ozonesonde data from four Japanese stations provided further evidence showing that the 3-week shift in the respective sampling windows of PWB and TP was a likely cause for the differences seen in O3 levels and in photochemical activity between the two airborne studies. Copyright 2003 by the American Geophysical Union

Volcanic-aerosol-induced changes in stratospheric ozone following the eruption of Mount Pinatubo

Measurements of lower stratospheric ozone in the Tropics using electrochemical concentrations cell (ECC) sondes and the airborne UV Differential Absorption Lidar (DIAL) system after the eruption of Mt. Pinatubo are compared with the Stratospheric Aerosol and Gas Experiment 2 (SAGE 2) and ECC sonde measurements from below the eruption to determine what changes have occurred as a result. Aerosol data from the Advanced Very High Resolution Radiometer (AVHRR) and the visible and IR wavelengths of the lidar system are used to examine the relationship between aerosols and ozone changes. Ozone decreases of 30 percent at altitudes between 19 and 26 km, partial column (16-28 km) decreases of about 27 D.U., and slight increases (5.4 D.U.) between 28 and 31 km are found in comparison with SAGE 2 climatological values