Rate constants for the reactions of hydroxyl and hydroperoxyl radicals with ozone

Chain decomposition of ozone by hydroxyl and hydroperoxyl radicals has been observed. The rate constant at 3000 degrees K for OH + O(3)-->HO(2) + O(2) is 8 x 10(-14) cubic centimeters per second. The rate constant for HO(2) + O(3)--> OH + 2O(2), is 3 x 10(-15) cubic centimeters per second. These results have implications concerning stratospheric ozone.     

Bulk chemical characteristics of dissolved organic matter in the ocean

Dissolved organic matter (DOM) is the largest reservoir of reduced carbon in the oceans. The nature of DOM is poorly understood, in part, because it has been difficult to isolate sufficient amounts of representative material for analysis. Tangential-flow ultrafiltration was shown to recover milligram amounts of >1000 daltons of DOM from seawater collected at three depths in the North Pacific Ocean. These isolates represented 22 to 33 percent of the total DOM and included essentially all colloidal material. The elemental, carbohydrate, and carbon-type (by (13)C nuclear magnetic resonance) compositions of the isolates indicated that the relative abundance of polysaccharides was high ( approximately 50 percent) in surface water and decreased to approximately 25 percent in deeper samples. Polysaccharides thus appear to be more abundant and reactive components of seawater DOM than has been recognized.     

Radium-226 and radon-222: concentration in atlantic and pacific oceans

Measurements of radon-222 in seawater suggest the following. The radium-226 content of surface water in both the Atlantic and Pacific oceans is uniformly close to about 4 x 10(-14) gram per liter. The deep Pacific has a concentration of radium-226 that is four times higher and the deep Atlantic a concentration twice as high as that of the surface. These distribution profiles can be explained by the same particle-settling rate for radium-226 from surface to depth for the two oceans and by a threefold longer residence time of water in the deep Pacific than in the deep Atlantic. The vertical distribution of the deficiency of radon-222 in the surface water of the northwest Pacific Ocean suggests a coefficient of vertical eddy diffusion as high as 120 square centimeters per second and a gas-exchange rate for carbon dioxide in surface water between 14 and 60 moles per square meter per year. Vertical profiles of the excess of radon-222 in near-bottom water of the South Atlantic give coefficients of vertical eddy diffusion ranging from 1.5 to more than 50 square centimeters per second.     

Nitrogen uptake, dissolved organic nitrogen release, and new production

In oceanic, coastal, and estuarine environments, an average of 25 to 41 percent of the dissolved inorganic nitrogen (NH(4) (+) and NO(3) (-)) taken up by phytoplankton is released as dissolved organic nitrogen (DON). Release rates for DON in oceanic systems range from 4 to 26 nanogram-atoms of nitrogen per liter per hour. Failure to account for the production of DON during nitrogen-15 uptake experiments results in an underestimate of gross nitrogen uptake rates and thus an underestimate of new and regenerated production. In these studies, traditional nitrogen-15 techniques were found to underestimate new and regenerated production by up to 74 and 50 percent, respectively. Total DON turnover times, estimated from DON release resulting from both NH(4) (+) and NO(3) (-) uptake, were 10 +/- 1, 18 +/- 14, and 4 days for oceanic, coastal, and estuarine sites, respectively.     

Normal atmosphere: large radical and formaldehyde concentrations predicted

A steady-state model of the normal (unpolluted) surface atmosphere predicts a daytime concentration of hydroxyl, hydroperoxyl, and methylperoxyl radicals approaching 5 x 10(8)molecules per cubic centimeter and a formaldehyde concentration of 5 x 10(10) molecules per cubic centimeter or 2 parts per billion. A radical chain reaction is proposed for the rapid removal of carbon monoxide, leading to a carbon monoxide lifetime as low as 0.2 year in the surface atmosphere.     

The Density of Hydrous Magmatic Liquids

Density measurements on several hydrous (相似文献   

Aluminum-26 and beryllium-10 in greenland ice

Activities of beryllium-10 and aluminum-26 dissolved in 200-year-old Greenland ice were found to be 18.4 (+ 8.4, - 4.8) x 10(-6) and 3.2 +/- 0.9 x 10(-7) disintegration per minute per liter, respectively. From these values and the precipitation rate (30 milliliters of water per square centimeter per year), the production rates of these isotopes are calculated to be 3.6 (+ 1.6, - 0.9) x 10(-2) and 1.7 +/- 0.5 x 10(-4) atom per second * square centimeter. These rates agree with the rates calculated for the production of these isotopes by cosmic rays in the atmosphere. Probably all the Al(26) in the ice is accounted for by such atmospheric production; however, an upper limit for the influx of cosmic dust bearing aluminum-26 is calculated at 3.2 x 10(5) tons per year for Earth. Only upper limits could be found for Al(26) and Be(10) in the undissolved particulate matter in the ice; their addition to the activities in the dissolved material leaves our conclusions unchanged.     

Temperature and surface-ocean water balance of the mid-holocene tropical western pacific

Skeletal Sr/Ca and 18O/16O ratios in corals from the Great Barrier Reef, Australia, indicate that the tropical ocean surface approximately 5350 years ago was 1 degrees C warmer and enriched in 18O by 0.5 per mil relative to modern seawater. The results suggest that the temperature increase enhanced the evaporative enrichment of 18O in seawater. Transport of part of the additional atmospheric water vapor to extratropical latitudes may have sustained the 18O/16O anomaly. The reduced glacial-Holocene shift in seawater 18O/16O ratio produced by the mid-Holocene 18O enrichment may help to reconcile the different temperature histories for the last deglaciation given by coral Sr/Ca thermometry and foraminiferal oxygen-isotope records.     

Oxygen consumption in pelagic marine sediments

Measurements in the interstitial waters of pelagic red clay and carbonate ooze sediments in the central equatorial Pacific show that the dissolved oxygen content decreases with depth and levels off at nonzero values. The supply of reactive organic carbon introduced by bioturbation limits oxygen consumption at depth in the sediment. These gradients should produce diffusive fluxes across the sediment-water interface that average about 8.8 x 10(-14) mole per square centimeter per second or 0.08 milliliter per square meter per hour.     

Beryllium-10 from the Sun

Beryllium-10 (10Be) in excess of that expected from in situ cosmic ray spallation reactions is present in lunar surface soil 78481; its presence was revealed with a sequential leaching technique. This excess 10Be, representing only 0.7 to 1.1% of the total 10Be inventory, is associated with surface layers (<1 micrometer) of the mineral grains composing 78481. This excess 10Be and its association with surficial layers corresponds to (1.9 +/- 0.8) x 10(8) atoms per square centimeter, requiring a 10Be implantation rate of (2.9 +/- 1.2) x 10(-6) atoms per square centimeter per second on the surface of the Moon. The most likely site for the production of this excess (10)Be is the Sun's atmosphere. The 10Be is entrained into the solar wind and transported to the lunar surface.     

Carbon monoxide balance in nature

Consideration of the steady-state equations for stable carbon monoxide and for radioactive carbon monoxide in the troposphere leads to the conclusion that carbon monoxide is produced at a rate of 5x10(15) grams per year, a value some 25 times greater than the rate of carbon monoxide production from combustion. The concomitant residence time for carbon monoxide is 0.1 year, in agreement with a previous estimate of Weinstock. Hydroxyl radicals are shown to account for both the production of this large amount of carbon monoxide by methane oxidation and for its removal by carbon monoxide oxidation. The average concentration of hydroxyl radicals in the troposphere required to achieve this effect is 2.3x10(6) molecules per cubic centimeter, with a daytime concentration of twice that. Levy and McConnell, McElroy, and Wofsy have deduced concentrations of hydroxyl radicals in the troposphere of the same magnitude from purely photochemical considerations, in support of this model.     

生物质炭可溶性有机物化学组成及生物活性意义

生物质热解炭化过程中,有机可挥发组分从固相逸出,冷凝后重新吸附于生物质炭,成为其中的可溶性有机物。生物质炭可溶性有机物化学组成复杂,主要含小分子有机物与芳香类化合物且含有丰富的官能团,具有较高的化学反应活性和生物活性,可显著地改变土壤中养分元素和污染物的形态与有效性,影响土壤微生物组成与丰度,调控作物的生长与健康。依生物质原料和热解条件的差异,生物质炭可溶性有机物的化学结构与生物活性功能也不尽相同。生物质炭可溶性有机物的生物活性意义主要表现为对生物的刺激作用,但部分生物质炭可溶性有机物可能具有一定的潜在毒性风险。通过提取生物质炭可溶性有机物可生产具有生物刺激作用的商品液体有机肥,从而实现生物质炭的分值利用。未来需要进一步加强生物质炭可溶性组分的生物活性或毒性物质的鉴定及其形成机制的研究,这对于生物质炭产品的优化是十分必要的,也是应用生物质炭尽量避免环境风险的要求。     

Dimethyl sulfide in the surface ocean and the marine atmosphere: a global view

Dimethyl sulfide (DMS) has been identified as the major volatile sulfur compound in 628 samples of surface seawater representing most of the major oceanic ecozones. In at least three respects, its vertical distribution, its local patchiness, and its distribution in oceanic ecozones, the concentration of DMS in the sea exhibits a pattern similar to that of primary production. The global weightedaverage concentration of DMS in surface seawater is 102 nanograms of sulfur (DMS) per liter, corresponding to a global sea-to-air flux of 39 x 10(12) grams of sulfur per year. When the biogenic sulfur contributions from the land surface are added, the biogenic sulfur gas flux is approximately equal to the anthropogenic flux of sulfur dioxide. The DMS concentration in air over the equatorial Pacific varies diurnally between 120 and 200 nanograms of sulfur (DMS) per cubic meter, in agreement with the predictions of photochemical models. The estimated source flux of DMS from the oceans to the marine atmosphere is in agreement with independently obtained estimates of the removal fluxes of DMS and its oxidation products from the atmosphere.     

Rapid formation of sulfuric acid particles at near-atmospheric conditions

We investigated the formation of new particles in a laboratory study, starting from H2SO4 produced in situ through the reaction of OH radicals with SO2. Newly formed particles were observed for H2SO4 concentrations above 7 x 10(6) per cubic centimeter. At 293 kelvin, a rough estimate yielded a nucleation rate of 0.3 to 0.4 particles per cubic centimeter per second for approximately 10(7) particles per cubic centimeter of H2SO4 (particle size >/= 3 nanometers). These findings are in agreement with observations from the atmosphere. The results demonstrate that under laboratory conditions similar to the atmosphere, particle formation occurs at atmospheric H2SO4 concentration levels.     

Atmospheric detection of water dimers via near-infrared absorption

Weakly bonded pairs of water molecules (H2O)2, or water dimers (WDs), may play an important role in photochemistry and climate, but the overlap of most of its spectral features with the water monomer (WM) has made detection difficult. We report on WD absorption measurements by means of atmospheric long-path (18.34 kilometers) differential optical absorption spectroscopy of the near-infrared OH stretching mode 0>f 4>b overtone transition predicted to be located near 746 nanometers. Our observation is in reasonable agreement with the known thermochemistry, calculated and measured structure, and spectroscopy (band strength, shape, and width) of the WD. The observation implies that the WD 0>f 4>b band is located at 749.5 nanometers, with a full width at half maximum of approximately 19.4 wave numbers, and that its band strength ranges between 1.23 x 10(-22) and 5.25 x 10(-22) centimeters per molecule.     

Atmospheric oxygen: isotopic composition and solubility fractionation

Atmospheric oxygen has been found to be enriched in oxygen-18 by 23.5 +/- 0.3 per mil relative to average ocean water (SMOW). Oxygen dissolved in seawater is further enriched in oxygen-18 by 0.85 per mil at 0 degrees C. The temperature dependence of the solubility enrichment is given by epsilon (per mil) = 0.85- 0.010 t ( degrees C). This result is in good agreement with earlier measurements of the solubility effect in distilled water.     

水溶性有机质对茶园土壤氟形态的影响

采用元素分析与傅里叶变换红外光谱相结合的方法分析了腐熟鸡粪中水溶性有机质(dissolved organicmatter,DOM)的结构及组成,通过溶液连续提取-电位分析法分析茶园土壤中氟的形态及含量。结果表明,腐熟鸡粪DOM中C、O、H和N元素含量占元素总量的93%,其中C和O的含量大于H和N,C/H和C/N较大,C、H饱和度低,含有较多羧基、醛基、酮基等不饱和度高的物质。水溶态和有效态氟含量随外源DOM添加量的增加而降低,呈负相关关系;而土壤铁锰结合态氟、有机结合态氟含量则随外源DOM添加量的增加而升高,呈正相关关系。外源DOM的加入可降低茶园土壤水溶态和有效态氟含量,提高了铁锰结合态氟、有机结合态氟含量,降低氟的生物可利用性。     

Hubble space telescope observations of comet p/shoemaker-levy 9 (1993e)

The Hubble Space Telescope observed the fragmented comet P/Shoemaker-Levy 9 (1993e) (P indicates that it is a periodic comet) on 1 July 1993. Approximately 20 individual nuclei and their comae were observed in images taken with the Planetary Camera. After subtraction of the comae light, the 11 brightest nuclei have magnitudes between approximately 23.7 and 24.8. Assuming that the geometric albedo is 0.04, these magnitudes imply that the nuclear diameters are in the range approximately 2.5 to 4.3 kilometers. If the density of each nucleus is 1 gram per cubic centimeter, the total energy deposited by the impact of these 11 nuclei into Jupiter's atmosphere next July will be approximately 4 x 10(30) ergs ( approximately 10(8) megatons of TNT). This latter number should be regarded as an upper limit because the nuclear magnitudes probably contain a small residual coma contribution. The Faint Object Spectrograph was used to search for fluorescence from OH, which is usually an excellent indicator of cometary activity. No OH emission was detected, and this can be translated into an upper limit on the water production rate of approximately 2 x 10(27) molecules per second.     

Oceanic electric fields: perception by american eels?

American eels, long-distance migrating fish, consistently exhibited conditioned cardiac deceleration responses to electric fields as small as 0.167 x 10(-2) microampere per square centimeter in water of resistivity 4000 ohm centimeters (6.7 microvolts per centimeter) and 400 ohm centimeters (0.67 microvolt per centimeter). Fewer responses were shown at this current density (0.167 x 10(-2) microampere per square centimeter) in more saline water (40 ohm centimeters, 0.067 microvolt per centimeter) and at a lower current density (0.167 x 10(-3) microampere per square centimeter) in fresh water. Thus, eels have sufficient sensitivity to utilize geoelectric information for orientation.     

Catalytic hydration of terminal alkenes to primary alcohols

Direct catalytic hydration of terminal alkenes to primary alcohols would be an inexpensive route to industrially useful alcohols and a convenient synthetic route for the synthesis of terminal alcohols in general. The reaction between trans- PtHCl(PMe(3))(2) (where Me = CH(3)) and sodium hydroxide in a one-to-one mixture of water and 1-hexene yields a species that, at 60 degrees C and in the presence of the phasetransfer catalyst benzyltriethylammonium chloride, catalyzes selective hydration of 1-hexene to n-hexanol at a rate of 6.9 +/- 0.2 turnovers per hour. Hydration of 1-dodecene to n-dodecanol occurs at a rate of 8.3 +/- 0.4 turnovers per hour at 100 degrees C. Deuterium labeling experiments with trans-PtDCl(PMe(3))(2) show that hydration involves reductive elimination of a C-H bond. At low hydroxide concentrations (<8 equivalents), hydration of the water-soluble olefin 3-butene-1-ol to 1,4-butanediol exhibited a first-order dependence on hydroxide concentration for loss of catalytic activity. This suggests that hydroxide attacks the coordinated alkene slowly. At high hydroxide concentrations, the rate of catalysis was hydroxide-independent and first order in alkene. Substitution of coordinated water (k(1) = 9.3 +/- 0.5 x 10(-3) liters per mol per second) appears to be limitng under these conditions.