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Analysis of high-spatial-resolution (approximately 0.8 arcsec) methane band and continuum imagery of Neptune's relatively homogeneous Equatorial Region yields significant constraints on (1) the stratospheric gaseous methane mixing ratio (fCH4,s), (2) the column abundances and optical properties of stratospheric and tropospheric hydrocarbon hazes, and (3) the wavelength-dependent single-scattering albedo of the 3-bar opaque cloud. From the center-to-limb behavior of the 7270-angstroms and 8900-angstrom sCH4 bands, the stratospheric methane mixing ratio is limited to fCH4,s < 1.7 x 10(-3), with a nominal value of fCH4,s = 3.5 x 10(-4), one to two orders of magnitude less than pre-Voyager estimates, but in agreement with a number of recent ultraviolet and thermal infrared measurements, and largely in agreement with the tropopause mixing ratio implied by Voyager temperature measurements. Upper limits to the stratospheric haze mass column abundance and 6190-angstroms and 8900-angstroms haze opacities are 0.61 microgram cm-2 and 0.075 and 0.042, respectively, with nominal values of 0.20 microgram cm-2 and 0.025 and 0.014 for the 0.2-micrometer radius particles preferred by the recent Voyager PPS analysis of Pryor et al. (1992, Icarus 99, 302-316). The tropospheric CH4 haze opacities are comparable to that found in the stratosphere, upper limits of 0.104 and 0.065 at 6190 angstroms and 8900 angstroms, respectively, with nominal values of 0.085 and 0.058. This indicates a column abundance less than 11.0 micrograms cm-2, corresponding to the methane gas content within a well-mixed 3% methane tropospheric layer only 0.1 cm thick near the 1.5-bar CH4 condensation level. Constraints on the single-scattering albedos of these hazes include (1) for the stratospheric component, 6190-angstroms and 8900-angstroms imaginary indices of refraction less than 0.047 and 0.099, respectively, with 0.000 (conservative scattering) being the nominal value at both wavelengths, and (2) CH4 haze single-scattering albedos greater than 0.85 and 0.50 at these two wavelengths, with conservative scattering again begin the preferred value. However, conservative scattering is ruled out for the opaque cloud near 3 bars marking the bottom of the visible atmosphere. Specifically, we find cloud single-scattering albedos of 0.915 +/- 0.006 at 6340 angstroms, 0.775 +/- 0.012 at 7490 angstroms, and 0.803 +/- 0.010 at 8260 angstrom. Global models utilizing a complete global spectrum confirm the red-absorbing character of the 3-bar cloud. The global-mean model has approximately 7.7 times greater stratospheric aerosol content then the Equatorial Region. An analysis of stratospheric haze precipitation rates indicates a steady-state haze production rate of 0.185-1.5 x 10(-14) g cm-2 sec-1, in agreement with recent theoretical photochemical estimates. Finally, reanalysis of the Voyager PPS 7500-angstroms phase angle data utilizing the fCH4,s value derived here confirms the Pryor et al. result of a tropospheric CH4 haze opacity of a few tenths in the 22-30 degrees S latitude region, several times that of the Equatorial Region or of the globe. The factor-of-10 reduction in fCH4,s below that assumed by Pryor et al. implies decreased gas absorption and consequently a decrease in the forward-scattering component of tropospheric aerosols. 相似文献
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在阿根廷科尔多瓦省Pampa平原进行了地下水和黄土沉积物的地球化学研究,该地区面积约30000km~2,位于西经61°45′～63°00′,南纬31°30′～33°55′。在选择的150个地下水水样中,确定其物理化学参数和矿化度(表)1。水样中96％以上为碱性, 相似文献
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磷酸一酯（ＲＯ）Ｐ（Ｏ）（ＯＨ）２是一种强极性的有机磷化合物。研究了水体中磷酸一（１－萘）酯的富集和上色谱分析,建立了一个简便快速、高灵敏度、实用的分析方法。富集是采用固相萃取方法,选用载有十八烷基硅烷的尼龙滤膜吸附,甲醇洗脱,回收率达７２％￣７％。它的气相色谱分析选用ＢＳＴＦＡ为衍生剂,反应条件为温度６５℃,反应时间３０ｍｉｎ,获得了满意的结果。方法的最低检测限为０。０６ｎｇ。 相似文献
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The temporal variability of 210Po and 210Pb was examined in the overlying water of the Zhubi Coral Reef flat to detect nutrient-like behavior of 210Po. Different mechanisms influencing their geochemical behaviors were observed. Excess 210Po relative to 210Pb revealed an additional input of 210Po other than in situ production from 210Pb. The 210Po input comes from the reef flat sediment through diffusion. The diffusion contributes 62% of the total 210Po. This diffusion of 210Po directly highlights its nutrient-like behavior. No input, but the slight removal, of 210Pb was observed. Fractionation factors indicate that particulate matter prefers to adsorb 210Po rather than 210Pb. In combination with particulate composition, 210Po diffusion was closely related to organic matter. These results reveal that 210Po might be a potential tracer for quantifying nutrient recycling in the Coral Reef system. 相似文献
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在晚始新世早期的沉积物记录中 ,至少两次地外行星对地球的强撞击产生了至少两个紧邻的冲击抛出物散布场 (含单斜辉石类球粒散布场和北美陨石雨散布场 )。两个直径为９０～１００ｋｍ的撞击坑被认为是抛出物散布场的来源 ;切萨皮克海撞击坑和Ｐｏｐｉｇａｉ撞击坑。在某些地区计算的这两个抛出物地层相差１０ -２０ｋａ。然而 ,在大多数地区 ,由于其中的一个地层缺失或者垂向混合 ,两个地层已无法辨认。北美陨石雨散布场的玻陨石４０Ａｒ／ ３９Ａｒ测年 (两个地层的上层 )为３５．５Ｍａ。生物地层学研究揭示了这些撞击碎屑层与海洋生物的… 相似文献
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Moon HB An YR Park KJ Choi SG Moon DY Choi M Choi HG 《Marine pollution bulletin》2011,62(9):1963-1968
Reports of the occurrence and accumulation patterns of polycyclic aromatic hydrocarbons (PAHs) and synthetic musk compounds (SMCs) in marine mammals are scarce. In this study, the concentrations and accumulation profiles of PAHs and SMCs were determined in blubber from finless porpoises in Korean coastal waters. Total concentrations of PAHs and SMCs ranged from 6.0 to 432 (mean: 160) ng/g lipid weight and from 17 to 144 (mean: 52) ng/g lipid weight, respectively. Residue levels of PAHs were lower than those reported from other studies, while residue levels of SMCs were relatively higher than those reported in other studies. Naphthalene was the most abundant PAH and HHCB was the dominant SMC observed in finless porpoises. The concentrations of PAHs and SMCs were not correlated with each other, but were significantly correlated within the same chemical groups. No correlations were found between body size and residue levels of PAHs and SMCs. 相似文献
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Data on the occurrence and accumulation profiles of butyltins (BTs), including tributyltin (TBT), in marine mammals are scarce. This is the first study to investigate residue levels and accumulation patterns of BTs in cetaceans from Korean coastal waters. The total concentrations of BTs (sum of mono- to tri-butyltins) in minke whales (Balaenoptera acutorostrata) and long-beaked common dolphins (Delphinus capensis) ranged from 15.7 to 297 ng/g wet weight (mean: 100 ng/g wet weight) and from 59.0 to 412 ng/g wet weight (mean: 228 ng/g wet weight), respectively. Dibutyltin (DBT) accounted for 63% of the total BTs in all cetacean samples. Significant species-specific differences in BT concentrations, possibly due to the differences in their habitat and diet, were found between the two cetacean species. The concentrations of DBT and TBT in most cetacean samples exceeded the threshold value for cytotoxic effects in cetaceans, implying potentially adverse health risks from exposure to BTs. 相似文献
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The radionuclides (210)Po and (210)Pb were examined to trace the cycling of particulate organic carbon (POC) and particulate organic nitrogen (PON) in the Zhubi coral reef lagoon. The net export flux of POC to the open sea is 14 mg Cm(-2) d(-1). However, the net exchange of PON has not yet been observed. On average, the vertical export fluxes in the lagoon of POC and PON, as derived from (210)Po/(210)Pb disequilibria, are 43 mg Cm(-2) d(-1) and 13.8 mg Nm(-2) d(-1), respectively. The deficit of (210)Po relative to (210)Pb in particulate matter provides evidence for the degradation of particulate organic matter. According to the mass balance budgets, 310 mg Cm(-2) d(-1) and 121 mg Nm(-2) d(-1) were recycled into dissolved fractions. Based on a first-order kinetics model, the degradation rate constants of POC and PON are 0.28 and 0.30 m(-1), respectively. Thus, (210)Po and (210)Pb can quantify the cycling of carbon and nitrogen in this coral lagoon. 相似文献