Clouds, haze, and CH4, CH3D, HCN, and C2H2 in the atmosphere of Titan probed via 3 μm spectroscopy

Using synthetic spectra derived from an updated model atmosphere together with a continuum model that includes contributions from haze, cloud and ground, we have re-analyzed the recently published (Geballe et al., 2003, Astrophys. J. 583, L39-L42) high-resolution 3 μm spectrum of Titan which contains newly-detected bands of HCN (in emission) and C₂H₂ and CH₃D (in absorption), in addition to previously detected bands of CH₄. In the 3.10-3.54 μm interval the analysis yields strong evidence for the existence of a cloud deck or optically thick haze layer at about the 10 mbar (∼ 100 km) level. The haze must extend well above this altitude in order to mask the strong CH₄ lines at 3.20-3.50 μm. These cloud and haze components must be transparent at 2.87-2.92 μm, where analysis of the CH₃D spectrum demonstrates that Titan's surface is glimpsed through a second cloud deck at about the 100 mbar (∼ 50 km) level. Through a combination of areal distribution and optical depth this cloud deck has an effective transmittance of ∼ 20%. The spectral shape of Titan's continuum indicates that the higher altitude cloud and haze particles responsible for suppressing the CH₄ absorptions have a largely organic make-up. The rotational temperature of the HCN ranges from 140 to 180 K, indicating that the HCN emission occurs over a wide range of altitudes. This emission, remodeled using an improved collisional deactivation rate, implies mesospheric mixing ratio curves that are consistent with previously predictions. The stratospheric and mesospheric C₂H₂ mixing ratios are ∼¹⁰⁻⁵, considerably less than previous model predictions (Yung et al., 1984), but approximately consistent with recent observational results. Upper limits to mixing ratios of HC₃N and C₄H₂ are derived from non-detections of those species near 3.0 μm.     

DETERMINATION OF SEDIMENTARY RATE IN ESTUARY AND COAST BY ~(228)Th TECHNIQUE

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Seasonal and spatial distribution of nonylphenol and IBP in Saemangeum Bay, Korea

In order to investigate spatial and temporal distribution of organic pollutants in the Saemangeum Bay, organophosphorus pesticides (10), alkylphenols (8), chlorophenols (2), bisphenol A were analyzed from the surface seawater taken in 2002–2003. Most of the analytes were not detected in all stations except nonylphenol and S-benzyl-O,O-di-isopropyl phosphorothioate (IBP). Concentrations of nonylphenol and IBP ranged from ND to 298 ng/l and from ND to 1840 ng/l, respectively. The high levels of nonylphenol and IBP were found in the estuary areas of Mangyeong and Dongjin River. The levels of nonylphenol and IBP in surface seawater varied through seasons and the high levels of nonylphenol and IBP were in summer season (August). Based on real time monitoring of IBP and on correlation between concentrations of target compounds and contents of salinity in seawater, physical mixing and diffusion of seawater were found to be the major factors that affect the spatial distribution of IBP and nonylphenol in the Saemangeum Bay environment.     

Element geochemistry and cleaning potential of the No. 11 coal seam from Antaibao mining district

It has aroused great attention that the mobilization of potential toxic substance during coal mining, pro- cessing and using has serious negative influence on environment. Clearly, the coal cleaning can be prop-erly applied to removing hazardous elements or re-ducing their concentrations prior to combustion, which also is considered as an economical and effective technique in minimizing some of these problems[1]. Unfortunately, there are fairly few studies on the parti-tioning behavior of trac…     

Infrared Spectroscopy of Jupiter's Atmosphere after the A and E Impacts of Comet Shoemaker–Levy 9

Infrared spectra of Jupiter's atmosphere were obtained with the infrared spectrometer (IRS) on the 1.5-m telescope at the Cerro Tololo Inter-American Observatory (CTIO) during the first 2 days of the impacts of the fragments of Comet Shoemaker–Levy 9 (1993e). We monitored 3.51 ± 0.17 μm radiation from the impact areas, undisturbed areas, and auroral regions of Jupiter after the A and E impacts. The strong emission of a portion of the P-branch of the ν₃band of CH₄was detected on the A impact area 4 hr after the impact. H⁺₃emissions are found to be decreased at the A and E impact sites after 4 hr and 10 hr 50 min of the impacts, respectively, compared with undisturbed areas at the same latitude. The temperatures of the southern H⁺₃aurora were normal within the first several hours following the A and E impacts.     

Design of a low-cost attitude determination GPS/INS integrated navigation system

Due to their complementary features of GPS and INS, the GPS/INS integrated navigation system is increasingly being used for a variety of commercial and military applications. An attitude determination GPS (ADGPS) receiver, with multiple antennas, can be more effectively integrated with a low-cost IMU since the receiver gives not only position and velocity data but also attitude data. This paper proposes a low-cost attitude determination GPS/INS integrated navigation system. The proposed navigation system comprises an ADGPS receiver, a navigation computer unit (NCU), and a low-cost commercial MEMS IMU. The navigation software includes a fault detection and isolation (FDI) algorithm for integrity. In order to evaluate the performance of the proposed navigation system, two flight tests have been performed using a small aircraft. The first flight test confirmed the fundamental operation of the proposed navigation system and the effectiveness of the FDI algorithm. The second flight test evaluated the performance of the proposed navigation system and demonstrated the benefit of GPS attitude information in a high dynamic environment. The flight test results show that the proposed ADGPS/INS integrated navigation unit gives reliable navigation performance even when anomalous GPS data is provided and gives better navigation performance than a conventional GPS/INS unit.     

Historical change in lake sedimentation in Lake Takkobu, Kushiro Mire, northern Japan over the last 300 years

Environmental degradation, including shallowing, deterioration of aquatic habitat and water pollution, has arisen from the inflow of fine sediment to Lake Takkobu in northern Japan. The lake has experienced gradual environmental degradation due to agricultural development, which has introduced both fine sediment and sediment-associated nutrients into the lake. We have reconstructed the history of sediment yield to Lake Takkobu in Kushiro Mire over the last 300 years and have examined trends with reference to land-use development. Fifteen lake sediment core samples were obtained, and various physical variables of lake sediments were analyzed and dated using ¹³⁷Cs and tephrochronology. The physical variables showed that all points contained mainly silt, except for two points close to the river mouths, where the mean diameter was < 35 μm. The peaks were defined as a “signal” when the physical variables were synchronous in a profile. These were created by floods and engineering works constructing drainage systems. The signal of canal construction in 1898 was detected in all core points. Lake Takkobu core samples contained two tephra layers. From the refractive indices of dehydrated glasses, the lower tephra layer was identified as Ko-c2 (1694) and the upper tephra layer as Ta-a (1739). A clear peak in the ¹³⁷Cs concentration was detected at all the sampling points, except for the site close to the Takkobu River. This site showed two peaks in the ¹³⁷Cs concentration, which was attributed to perturbation from flood events and a drainage project. The maximum ¹³⁷Cs concentration was identified as the sediment surface from 1963, enveloped by the 1962 and 1964 signals. The sediment yield averaged over the last 300 years for Lake Takkobu was reconstructed for four periods using the signal, tephra and ¹³⁷Cs as marker layers. The sediment yield under the natural erosion condition for the first two periods was 226 tons/year from 1694 to 1739 and 196 tons/year from 1739 to 1898. The development of the Takkobu watershed started in 1880s with partial deforestation and channelization in 1898, 1959, and 1962 leading to an increased sedimentation yield of 1016 tons/year from 1898 to 1963. Continued deforestation, channelization works in 1964, road construction in 1980–1990s, as well as agriculture development caused a further increase to 1354 tons/year from 1963 to 2004. Compared to the averaged natural sedimentation yield of 206 tons/year until 1898, initial land-use development in a catchment accelerated lake sedimentation, indicated by the 5-fold sediment yield. With increasing agricultural development since 1960s, sedimentation yields were highest for 1963–2004; a 7-fold increase compared with pre-impact conditions. To reduce sediment yield, riparian buffers along the rivers should be preserved or rebuilt, and sluices may function effectively during short-term periods of flooding. Environmental management policy and laws restricting uncontrolled and inappropriate land-use might help in addition to ensure longer-term environmental health by reducing the sedimentation rate.     

Recent carbon and nitrogen uptake rates of phytoplankton in Bering Strait and the Chukchi Sea

Cruises to Bering Strait and the Chukchi Sea in US waters from late June in 2002 to early September in 2004 and the Russian–American Long-term Census of the Arctic (RUSALCA) research cruise in 2004 covered all major water masses and contributed to a better understanding of the regional physics, nutrient dynamics, and biological systems. The integrated concentration of the high nitrate pool in the central Chukchi Sea was greater in this study than in previous studies, although the highest nitrate concentration (∼22 μM) in the Anadyr Water mass passing through the western side of Bering Strait was consistent with prior observations. The chlorophyll-a concentrations near the western side of the Diomede Islands ranged from 200 to 400 mg chl-a m⁻² and the range in the central Chukchi Sea was 200–500 mg chl-a m⁻² for the 2002–2004 Alpha Helix (HX) cruises. Chlorophyll-a concentrations for the 2004 RUSALCA cruise were lower than those from previous studies. The mean annual primary production of phytoplankton from this study, using a ¹³C–¹⁵N dual-isotope technique, was 55 g C m⁻² for the whole Chukchi Sea and 145 g C m⁻² for the plume of Anadyr–Bering Shelf Water in the central Chukchi Sea. In contrast, the averages of annual total nitrogen production were 13.9 g N m⁻² (S.D.=±16.2 g N m⁻²) and 33.8 g N m⁻² (S.D.=±14.1 g N m⁻²) for the Chukchi Sea and the plume, respectively. These carbon and nitrogen production rates of phytoplankton were consistently two-or three-fold lower than those from previous studies. We suggest that the lower rates in this study, and consequently more unused nitrate in the water column, were caused by lower phytoplankton biomass in the Bering Strait and the Chukchi Sea. However, we do not know if the lower rate of production from this study is a general decreasing trend or simply temporal variations in the Chukchi Sea, since temporal and geographical variations are substantially large and presently unpredictable.