Heterogeneous phase reactions of Martian volatiles with putative regolith minerals

Summary The chemical reactivity of several minerals thought to be present in Martian fines is tested with respect to gases known in the Martian atmosphere. In these experiments, liquid water is excluded from the system, environmental temperatures are maintained below 0°, and the solar illumination spectrum is stimulated in the visible and UV using a Xenon arc lamp. Reactions are detected by mass spectrometric analysis of the gas phase over solid samples. No reacions were detected for Mars nominal gas over sulfates, nitrates, chloride, nontronite clay, or magnetite. Oxidation was not observed for basaltic glass, nontronite, and magnetite. However, experiments incorporating SO₂ gas - an expected product of volcanism and intrusive volatile release - gave positive results. Displacement of CO₂ by SO₂ occurred in all four carbonates tested. These reactions are catalyzed by irradiation with the solar simulator. A calcium nitrate hydrate released NO₂ in the presence of SO₂. These results have implications for cycling of atmospheric CO₂, H₂O, and N₂ through the regolith.     

Solar radiation incident on the Martian surface

Summary Calculations indicate that the maximum daily solar radiation reaching the Martian surface is about 325 cal/cm² during southern hemisphere summer at latitude of about 40°S. In the ultraviolet region of the spectrum, the radiation reaching the surface at wavelengths greater than 2800 Å is within 10% of the radiation incident on the atmosphere. There is significant extinction of radiation in the spectral region near 2500 Å in mid and high latitudes due to absorption of radiation by ozone; radiation reaching the surface may be reduced to one one-thousandth of that incident on the atmosphere during winter. Virtually no radiation of wavelengths less than 1900 Å reaches the surface because of absorption by the large column abundance of carbon dioxide. Daily and latitudinal distributions of radiation are presented for wavelengths of 3000, 2500 and 2000 Å.     

Possible oxidant sources in the atmosphere and surface of Mars

Summary Photolysis of H₂O in the atmosphere near the surface is a copious source of OH, HO₂, and probably superoxides, some of which are likely to condense on the surface and migrate through the pores. The processes have been modeled in detail for their atmospheric interest. The models successfully account for the rarity of CO and O₂, the notable variability of ozone, and the escape flux of hydrogen. Though only qualitative estimates can be made of surface deposition rates and lifetimes, the suggested amounts are in the range inferred by Viking. The OH rapidly destroys any organic molecules that are present as vapors.Analogous reactions involving adsorbed water have been studied by Huguenin. These processes can be driven by the much larger photon fluxes at longer ultraviolet wavelengths. The suggested explanations, and many of the experiments, make it likely that peroxides, superoxides, and adsorbed OH are all present. Both kinds of process, and their combinations, seem in principle able to explain the absence of all organic molecules and the variety of observed oxidants. Since they operate planetwide, there is a strong suggestion that the observed conditions are typical. Oases of higher than average humidity may in fact be even more hostile than the average region, because water under Martian surface conditions is anything but benign.Laboratory simulation of the atmospheric processes must pay careful attention to scaling.Curiously, similar OH densities occur at the Earth's surface, The notable differences are food for thought, and ideas about the origin of life may be particularly affected.Based on an invited paper at the Second International Colloquium on Mars, Pasadena, January 15–18, 1979     

土壤-植物下垫面对微生态环境的影响

综述了土壤植物下垫面对辐射平衡、热量条件、土壤侵蚀、土壤肥力、光能利用率等微生态环境的影响．结果表明,有植被下垫面的反射率、有效辐射、土壤热通量的日变幅和感热通量均小于荒坡裸地;坡地植草和减少翻耕次数有利于水土保持;下垫面栽种牧草可提高土壤肥力和光能利用率．这对合理开发和利用土地资源具有一定的参考价值     

Amplification of DNA bound on clay minerals

DNA adsorbs and binds on clay minerals, which provides protection to the DNA against degradation by nucleases but does not eliminate the ability of bound DNA to transform cells. These observations support the concept that 'cryptic genes' can persist in the environment when bound on particles and that the genes could subsequently be expressed if an appropriate host was transformed. The polymerase chain reaction (PCR) was used to amplify free and bound DNA from Bacillus subtilis and calf thymus. DNA bound on montmorillonite, but not on kaolinite, was amplified. However, amplification occurred when kaolinite was pretreated with sodium metaphosphate. DNA was not released from the clays during the amplification procedure. The type of clay (e.g. its structure and charges) affected amplification. Because DNA bound on clay is protected against biodegradation, the ability to amplify DNA bound on clay by the PCR has palaeontological, archaeological, and anthropological implications for the detection of 'ancient' DNA, as well as for monitoring the persistence of recombinant DNA introduced to the environment in genetically modified organisms.     

XPS and ab initio calculation of surface states of sulfide minerals: pyrite,chalcopyrite and molybdenite

Sulfide minerals contain sulphur in a large variety of coordination environments. Consequently, the S 2p XPS of various mineral surface states undergo different shifts in binding energy (BE) relative to the bulk, depending on the charge distribution on the surface. This in turn depends on the number, type and position of the atoms on the fracture surface, which is determined by the fracture mechanism.

We have investigated three sulfide minerals: pyrite (tetrahedrally-coordinated S), chalcopyrite (tetrahedrally-coordinated S) and molybdenite (layered structure with trigonally-coordinated S). Comparison of conventional with surface sensitive synchrotron XPS shows that the S 2p spectrum displays two additional doublets at lower BE than the bulk signal for pyrite, and one doublet each at lower and at higher BE for chalcopyrite. Each of these signals is derived from surface states. Molybdenite shows no additional states. A BE shift to lower (higher) BE suggests a charge increase (decrease) on the S atoms relative to those in the bulk because of higher (lower) charge screening.

We have used ab initio density functional calculations to validate this interpretation of the experimental evidence, obtaining Mulliken population analyses for the possible fracture surfaces and comparing their charge distribution with the corresponding bulk charge distribution. Our calculations support the assignments of S 2p surface contributions as follows: the lower BE peak of chalcopyrite (160.84 eV) as under-coordinated surface S states, the higher BE peak of chalcopyrite (161.88 eV) as surface S polymers, the lowest BE peak of pyrite (161.3 eV) as surface S monomers, and the next lowest BE peak of pyrite (162.0 eV) as under-coordinated surface S dimers. The absence of any surface states in molybdenite is also confirmed by the models.     

Visualization of UV exposure of the human body based on data from a scanning UV-measuring system

In general, measurements of UV radition are related to horizontal surfaces, as in the case of the internationally standardized and applied UV index, for example. In order to obtain more relevant information on UV exposure of humans the new measuring system ASCARATIS (Angle SCAnning RAdiometer for determination of erythemally weighted irradiance on TIlted Surfaces) was developed and built. Three systems of ASCARATIS have been in operation at different locations in Bavaria for 3 years, providing erythemally weighted UV irradiation data for 27 differently inclined surfaces every 2 min. On the basis of these data virtual three-dimensional models of the human body surface consisting of about 20,000 triangles could be created and each of these triangles coloured according to its UV irradiation. This allowed the UV exposure of the human body to be visualized for any kind of body posture and spatial orientation on the basis of real measuring data. The results of the UV measurements on inclined surfaces have shown that measuring UV radiation on horizontal surfaces, as done routinely worldwide, often underestimates the UV exposure of the human skin. Especially at times of the day or year with low solar elevations the UV exposure of parts of the human skin can be many times higher than that of the horizontal surface. Examples of three-dimensional modelling of the human UV irradiation are shown for different times of the day and year, altitudes above sea level, body postures and genders. In these examples the UV hotspots can be detected and, among other things, used to inform and educate the public about UV radiation.     

Protection of Bacterial Spores in Space, a Contribution to the Discussion on Panspermia

Spores of Bacillus subtilis were exposed to space in theBIOPAN facility of the European Space Agency onboard of the Russian Earth-orbiting FOTON satellite. The spores were exposed either in dry layers without any protecting agent, or mixed withclay, red sandstone, Martian analogue soil or meteorite powder,in dry layers as well as in so-called `artificial meteorites', i.e. cubes filled with clay and spores in naturally occurring concentrations. After about 2 weeks in space, their survival was tested from the number of colony formers. Unprotected spores in layers open to space or behind a quartz window were completely or nearly completely inactivated (survival rates in most cases10^-6). The same low survival was obtained behind a thin layer of clay acting as an optical filter. The survival rate was increased by 5 orders of magnitude and more, if the spores in the dry layer were directly mixed with powder of clay,rock or meteorites, and up to 100% survival was reached in soilmixtures with spores comparable to the natural soil to spore ratio. These data confirm the deleterious effects of extraterrestrial solar UV radiation. Thin layers of clay, rock or meteorite are only successful in UV-shielding, if they are indirect contact with the spores. The data suggest that in a scenario of interplanetary transfer of life, small rock ejecta ofa few cm in diameter could be sufficiently large to protectbacterial spores against the intense insolation; however, micron-sized grains, as originally requested by Panspermia, may notprovide sufficient protection for spores to survive. The data arealso pertinent to search for life on Mars and planetaryprotection considerations for future missions to Mars.     

The effects of wind and thermal radiation on thermal responses during rest and exercise in a cold environment

1. 1. The purpose of this study was to investigate the effects of thermal radiation and wind on thermal responses at rest and during exercise in a cold environment.

2. 2. The experimental conditions were radiation and wind (R + W), no radiation and wind (W), radiation and no wind (R), no radiation and no wind (C).

3. 3. The air temperature was −5°C. Thermal radiation was 360 W/m². Air velocities were 0.76, 1.73 and 2.8 m/s. Rectal and skin temperatures, heart rate and oxygen consumption were recorded. Thermal and comfort sensations were questioned.

4. 4. There are no significant effects of thermal radiation and wind on the physiological responses except the mean skin temperature. There are significant effects on the mean skin temperature (P < 0.01) and thermal sensation (P < 0.05).

增强的UV-B辐射对植物影响的研究

综述了国内外有关UV－B辐射对植物影响的研究现状与动态,讨论了增强的UV－B辐射对植物生长及形态结构、植物生理生化代谢、植物遗传物质、UV－B吸收物质及某些基因表达和种群及生态系统的影响。展望了增强的UV－B辐射对植物影响领域中值得深入探讨的问题。     

果胶酶高产菌种的紫外诱变选育及其培养条件的响应面法优化

以果胶酶产生菌黑曲霉EIM6为出发菌株,初始果胶酶活为14 539 U/mL,经紫外诱变反复处理,摇瓶复筛和遗传稳定性试验,最终获得一株果胶酶高产菌株EIMU2。EIMU2菌株的形态特征发生了明显的改变,相较于原出发菌株EIM6,孢子色泽更黑,孢子团也较出发菌株大,菌丝与孢子上凝结有更多的液珠。复筛后EIMU2酶活为32 161 U/mL,较原出发菌株提高了1.212倍。进一步通过响应面法对EIMU2菌株的液体发酵培养条件进行优化。优化后的培养条件为甜菜渣1.83%,花生饼粉1.69%,(NH_4)_2SO_4 0.5%,K_2HPO_4 0.3%,CaCO_3 0.2%,MgSO_4 0.15%(w/v),接种量6%(v/v),装液量21.36 mL。优化的突变菌株产酶活性进一步提高至98 794.3 U/mL,提高了2.07倍。     

Effects of artificial and solar UV-B radiation on the gravitactic orientation of the dinoflagellate, Peridinium gatunense

Abstract The effects of artificial and solar UV-B radiation on the gravitactic (formerly called geotactic) orientation of the freshwater dinoflagellate Peridinium gatunense were measured under artificial UV-B radiation and in a temperature-controlled growth chamber under solar radiation in Portugal. Circular histograms of gravitaxis show the impairement of orientation after UV irradiation. The degree of orientation, quantified using the Rayleigh test and top quadrant summation, decreased as the exposure time to the radiation prolonged. The effects of artifical UV-B radiation on orientation are stronger than those of solar radiation, probably because the radiation source emits higher fluence rates below 300 nm than found in solar radiation. After UV radiation, the gravitactic orientation under artificially increased acceleration at 2 g was drastically affected.     

Evaluation of residual soil contamination from commercial oil well drilling activities and its impact on the naturally occurring background radiation environment

Radiation exposure received by individuals living and working on a farmland contaminated with radium was evaluated by measuring the technologically enhanced radiation background using portable survey instruments and a high‐pressure ionization chamber. Analysis of selected organic compounds, metals, and radioactive material in samples of soil and water obtained from the farm demonstrate a potential risk to inhabitants that needs to be evaluated, especially for future generations living and working on this land who may not be aware of the potential hazard. The distribution of radium and several other hazardous waste materials was found to be significantly elevated in areas where sludge ponds and waste pits were formerly located. Transport of these contaminants in soil was detected by in situ measurement of radium, which may be a useful analog for determining the translocation of metals and other contaminants associated with oil well‐drilling activities. Conventional risk assessment models, using default input parameters, assume that exposure to radium in the soil is via the food chain and radon, and that inhalation of resuspended particles is less important. These models also assume that the chemical and physical characteristics of the radium contamination remain constant in time. However, under certain environmental conditions, the radium compounds will become more soluble with time, increasing their significance as a source of radiation exposure, especially as the radium will persist in soil for many thousands of years. Assessment of present and future risk to populations living and working on these contaminated lands must account for the potential change in radium solubility with time and the increased risk from both inhalation and ingestion of radium

This research describes environmental conditions found at one former well site in the Martha oil field in eastern Kentucky and identifies several important concerns related to the current and future risk associated with use of land contaminated with naturally occurring radioactive material.     

紫外辐射对东北红豆杉鲜叶中紫杉醇及三尖杉宁碱含量的影响

分别采用254、365 nm两种波长的紫外光对东北红豆杉鲜叶进行辐射,研究了波长、辐射时间以及样品处理方式对东北红豆杉鲜叶中紫杉醇及三尖杉宁碱含量变化的影响。结果表明,东北红豆杉鲜叶经匀浆处理后接受紫外辐射,两种波长的紫外光都可以使紫杉醇及三尖杉宁碱的含量增加,但不同波长对紫杉醇及三尖杉宁碱含量提高的趋势却不相同。365 nm的紫外光辐射2 h时使紫杉醇和三尖杉宁碱含量均提高到了最大值,两种物质含量分别提高了44.6%和53.0%,而254 nm的紫外光在辐射8 h时才达到最大值,两种物质含量分别提高了39.2%和24.3%。可以选取365 nm的紫外光对东北红豆杉鲜叶水匀浆体系进行辐射,快速高效地提高鲜叶内紫杉醇和三尖杉宁碱的含量。     

Lethal and mutational effects of solar and UV radiation on Staphylococcus aureus

Strains of Staphylococcus aureus, an opportunistic pathogen commonly found on human skin, were exposed to sunlight and UV C radiation, and the lethal and mutational effects measured. Sunlight killed cells with an inactivation constant of 3×10^-5 per joule per square metre; UV C was much more lethal, giving an inactivation constant of approximately 0.1 per joule per square metre. Some strains tested showed a sensitivity to sunlight that was dependent on the growth phase of the cells, exponentially growing cells showing a greater sensitivity. Mutational effects of irradiation were measured by the appearance of mutants sensitive to methicillin following irradiation of a multiresistant strain. Mutants appeared at a frequency of 10^-3; this high frequency of mutation in the region of the mec gene has also been observed when multiresistant strains are subjected to nutritional or thermal stress. Mutants showed the same chromosomal alteration (seen in pulse-field gel electrophoresis of Smal-digested DNA) whether induced by solar or UV C irradiation.     

Antioxidant prenylated phenols of Artocarpus plants attenuate ultraviolet radiation-induced damage on human keratinocytes and fibroblasts

Two novel prenylated phenols, cyclocomunoindenol (1) and cyclocomunohexanol (2) were isolated from the cortex of roots of Artocarpus communis. Their structures were determined by spectroscopic methods. Compounds 2 and 6 revealed significant DPPH-scavenging activity with an IC₅₀ values of 435.48 ± 0.93 and 53.55 ± 8.73 μM, respectively. Compounds 1, 2, and 6 displayed significant ABTS⁺ scavenging activity with an IC₅₀ values of 164.26 ± 2.44, 227.01 ± 3.64, and 44.09 ± 0.88 μM, respectively. Compound 6 exhibited an inhibitory effect on XO activity with an IC₅₀ value of 10.91 ± 1.77 μM and the relative oxygen radical absorbance capacity (ORAC) values of 1–6, using ORAC-pyrogallol red (PGR) assay, were determined to be 0.28 ± 0.06, 0.31 ± 0.02, 0.55 ± 0.25, 0.84 ± 0.36, 0.35 ± 0.15, and 0.70 ± 0.09, respectively. Antioxidants 5 and 6 significantly attenuate UVA radiation-induced damage on human HaCaT keratinocytes and Hs68 fibroblasts. These finding showed that 1–6 may be used as antioxidants and 5 and 6 may protect skin against the adverse effects of UV radiation.     

Importance of Biologically Active Aurora-like Ultraviolet Emission: Stochastic Irradiation of Earth and Mars by Flares and Explosions

Habitable planets will be subject to intense sources of ionizing radiation and fast particles from a variety of sources--from the host star to distant explosions--on a variety of timescales. Monte Carlo calculations of high-energy irradiation suggest that the surfaces of terrestrial-like planets with thick atmospheres (column densities greater than about 100 g cm(-2)) are well protected from directly incident X-rays and gamma-rays, but we find that sizeable fractions of incident ionizing radiation from astrophysical sources can be redistributed to biologically and chemically important ultraviolet wavelengths, a significant fraction of which can reach the surface. This redistribution is mediated by secondary electrons, resulting from Compton scattering and X-ray photoabsorption, the energies of which are low enough to excite and ionize atmospheric molecules and atoms, resulting in a rich aurora-like spectrum. We calculate the fraction of energy redistributed into biologically and chemically important wavelength regions for spectra characteristic of stellar flares and supernovae using a Monte-Carlo transport code and then estimate the fraction of this energy that is transmitted from the atmospheric altitudes of redistribution to the surface for a few illustrative cases. For atmospheric models corresponding to the Archean Earth, we assume no significant ultraviolet absorbers, only Rayleigh scattering, and find that the fraction of incident ionizing radiation that is received at the surface in the form of redistributed ultraviolet in the biologically relevant 200-320 nm region (UV-C and UV-B bands) can be up to 4%. On the present-day Earth with its ultraviolet ozone shield, this fraction is found to be 0.2%. Both values are many orders of magnitude higher than the fraction of direct ionizing radiation reaching the surface. This result implies that planetary organisms will be subject to mutationally significant, if intermittent, fluences of UV-B and harder radiation even in the presence of a narrow-band ultraviolet shield like ozone. We also calculate the surficial transmitted fraction of ionizing radiation and redistributed ultraviolet radiation for two illustrative evolving Mars atmospheres whose initial surface pressures were 1 bar. We discuss the frequency with which redistributed ultraviolet flux from parent star flares exceeds the parent star ultraviolet flux at the planetary surface. We find that the redistributed ultraviolet from parent star flares is probably a fairly rare intermittent event for habitable zone planets orbiting solar-type stars except when they are young, but should completely dominate the direct steady ultraviolet radiation from the parent star for planets orbiting all stars less massive than about 0.5 solar masses. Our results suggest that coding organisms on such planets (and on the early Earth) may evolve very differently than on contemporary Earth, with diversity and evolutionary rate controlled by a stochastically varying mutation rate and frequent hypermutation episodes.     

东海表层沉积硅藻组合与环境关系研究

对东海表层沉积硅藻分析研究,共发现有103种和变种,根据其中分布特征和规律,结合因子负荷变化曲线,把东海表层沉积分为六个硅藻组合和分布区,并探讨影响硅藻分布的环境因素,为恢复古环境提供科学依据。     

pEffects of UV radiation on the ultrastructure of several red algae

The effect of ultraviolet (UV) radiation on the ultrastructure of four red algae, the endemic Antarctic Palmaria decipiens (Reinsch) Ricker and Phycodrys austrogeorgica Skottsberg, the Arctic‐cold temperate Palmaria palmata (Linnaeus) O. Kuntze and the cosmopolitan Bangia atropurpurea (Roth) C. Agardh was studied. All four species showed a formation of ‘inside‐out’ vesicles from the chloroplast thylakoids upon exposure to artificial UV‐radiation. In P. decipiens, most vesicles were developed after 8 h and in P. palmata, after 48 h of UV exposure. In B. atropurpurea, vesi‐culation of thylakoids was observed after 72 h of UV irradiation. In Ph. austrogeorgica, the chloroplast envelope and thylakoid membranes were damaged and the phycobilisomes became detached from the thylakoids after 12 h of UV exposure. Ultraviolet‐induced changes in the membrane structure of mitochondria were observed in P. decipiens and P. palmata. However, in P. decipiens they were reversible as was the damage in chloroplast fine structure after 12 h of UV treatment. Protein crystals in Ph. austrogeorgica showed degradation after exposure to UV radiation. Different methods of fixation and embedding macroalgal material are discussed. These findings give insight into the fine structural changes which occur during and after UV exposure and indicate a relationship between the species dependent sensitivity to UV‐exposure and the depth distribution of the different species.     

Effect of carbon and nitrogen input on the bacterial community structure of Neocaledonian nickel mine spoils

Neocaledonian mine spoils are considered as an extreme environment because of their edaphic conditions, which are unfavourable for life. The principal characteristics of this soil are the high nickel content (20,000 ppm) and the very low carbon (0.2%) and nitrogen (0.01%) levels, which are certainly among the major limiting factors for heterotrophic bacterial growth. The aim of this work was to determine what changes could occur in the bacterial community structure of the mine spoils when a carbon and a nitrogen source were added. Soil bacterial response to nutrient addition was examined in both the mine spoils and an agricultural soil, which is characterized by normal levels of nutrients. 16S rRNA gene clone libraries constructed to characterize changes occurring in the different soil bacterial communities showed an important selection of Actinobacteria in the mine spoils as a consequence of nutrient amendment: Actinobacteria represented 75% and 96% of the bacterial community structure after succinate and glucose addition, respectively. This was observed only in the mine spoils and is probably a consequence of the extreme environmental conditions. Carbon amendment in the agricultural soil led to an increase in Firmicutes, mainly Bacillus sp.