Showing papers in "Pure and Applied Geophysics in 1978"
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TL;DR: This paper showed that at low normal stress the shear stress required to slide one rock over another varies widely between experiments and at high normal stress that effect is diminished and the friction is nearly independent of rock type.
Abstract: Experimental results in the published literature show that at low normal stress the shear stress required to slide one rock over another varies widely between experiments. This is because at low stress rock friction is strongly dependent on surface roughness. At high normal stress that effect is diminished and the friction is nearly independent of rock type. If the sliding surfaces are separated by gouge composed of Montmorillonite or vermiculite the friction can be very low.
3,498 citations
TL;DR: In this paper, a theory of friction is proposed that establishes a common basis for static and sliding friction, and experimental observations establish the transition from stable sliding to stick-slip to be a function of normal stress, stiffness and surface finish.
Abstract: Time-dependent increase of static friction is characteristic of rock friction undera variety of experimental circumstances. Data presented here show an analogous velocity-dependent effect. A theor of friction is proposed that establishes a common basis for static and sliding friction. Creep at points of contact causes increases in friction that are proportional to the logarithm of the time that the population of points of contact exist. For static friction that time is the time of stationary contact. For sliding friction the time of contact is determined by the critical displacement required to change the population of contacts and the slip velocity. An analysis of a one-dimensional spring and slider system shows that experimental observations establishing the transition from stable sliding to stick-slip to be a function of normal stress, stiffness and surface finish are a consequence of time-dependent friction.
1,111 citations
TL;DR: In the Entrada and Navajo Sandstones as mentioned in this paperentonite deformation bands are abundant in the San Rafael Desert, where they are important primary structures, preceding the development of large faults with displacements of several meters or tens of meters.
Abstract: Small faults with displacements of a few millimeters or centimeters are abundant in the Entrada and Navajo Sandstones, in the San Rafael Desert, Utah, where they are important primary structures, preceding the development of large faults with displacements of several meters or tens of meters. The small faults contain no surfaces of discontinuity, rather they occur as deformation bands about one millimeter and tens or hundreds of meters long, and across which the displacements are distributed. Two zones with different modes of deformation can be distinguished within a deformation band: an outer zone where the matrix, including pores and matrix material, deforms; and an inner zone, about 0.5 mm thick, where the sand grains fracture and further consolidation takes place. Fracturing of the grains is controlled by contact geometry; the grains tend to split into subgrains along lines connecting contact points between the grains. Then the angular subgrains, which are readily fractured, are further granulated and mixed with the matrix. The final product is the deformation band, with much smaller grain size, poorer sorting, and lower porosity than the original parent sandstone. The sandstone on either side of a deformation band is almost undisturbed — fractures are rare there — so that deformation is highly localized within the band. The material within a deformation band apparently strain hardens as a result of the deformation; perhaps this is why the shear displacement across a deformation band is at most a few centimeters.
469 citations
TL;DR: In this paper, three forms of fault are recognized in Entrada and Navajo Sandstones in the San Rafael Desert, southeastern Utah; deformation bands, zones of deformation band, and slip surfaces.
Abstract: Three forms of fault are recognized in Entrada and Navajo Sandstones in the San Rafael Desert, southeastern Utah; deformation bands, zones of deformation bands, and slip surfaces. Small faults occur as deformation bands, about one millimeter thick, in which pores collapse and sand grains fracture, and along which there are shear displacements on the order of a few millimeters or centimeters. Two or more deformation bands adjacent to each other, which share the same average strike and dip, form a zone of deformation bands. A zone becomes thicker by addition of new bands, side by side. Displacement across a zone is the sum of displacements on each individual band. The thickest zones are about 0.5 m and total displacement across a thick zone rarely exceeds 30 cm. Finally, slip surfaces, which are through-going surfaces of discontinuity in displacement, form at either edge of zones of highly concentrated deformation bands. In contrast with individual deformation bands and zones of deformation bands, slip surfaces accommodate large displacements, on the order of several meters in the San Rafael Desert.
387 citations
TL;DR: In this article, the average mixing ratio of methane in the troposphere was 1.41 ppm and 1.3 ppmv for the northern and southern hemisphere, respectively, which corresponds to a total amount of 4×1015 g of CH4 present in the atmosphere.
Abstract: In 1972 average mixing ratio of methane in the troposphere was 1.41 ppm and 1.3 ppmv for the northern and southern hemisphere, respectively, which corresponds to a total amount of 4×1015 g of CH4 present in the atmosphere. Most is of recent biologic origin.14C analyses show that no more than 20 percent is released by fossil sources. The various ecosystems producing CH4 are discussed and the total annual production is estimated to lie between 5.5×1014 g/yr and 11×1014 g/yr. The corresponding turnover times for atmospheric CH4 range from 4 to 7 yrs. The destruction of CH4 takes place mainly in the troposphere, most probably through the reaction of CH4 + OH ↠ CH3 + H2O. About 10 percent of the CH4 is destroyed in the stratosphere. The CH4 cycle contributes on the order of 1 percent to the atmospheric carbon cycle.
227 citations
TL;DR: In this article, transient creep and semibrittle behavior of crystalline solids were analyzed at high effective confining pressure and the results showed that thermally-activated microfracturing probably dominates the creep rate.
Abstract: We review transient creep and semibrittle behavior of crystalline solids. The results are expected to be pertinent to crystalline rocks undergoing deformation in the depth range 5 to 20 km, corresponding to depths of focus of many major earthquakes. Transient creep data for crystalline rocks at elevated temperatures are analyzed but are poorly understood because of lack of information on the deformation processes which, at low to moderate pressure, are likely to be semibrittle in nature. Activation energies for transient creep at high effective confining pressure are much higher than those found for atmospheric pressure tests in which thermally-activated microfracturing probably dominates the creep rate. Empirical transient creep equations are extrapolated at 200° to 600°C, stresses from 0.1 to 1.0 kbar, to times ranging from 3.17 × 102 to 3.17 × 108 years. At the higher temperatures, appreciable transient creep strains may take place but the physical significance of the results is in question because the flow mechanisms have not been determined. The purpose of this paper is to stimulate careful research on this important topic.
140 citations
TL;DR: In this paper, the onset of dilatancy has not been identified, but most of the dilatance occurs within about 10 percent of the fracture stress difference, and the actual pore volume increase is larger in high initial porosity.
Abstract: Volume changes in geologic materials have been measured with strain gauges, cantilever displacement gauges, or through observation of either pore or total volume. When porosity is less than 0.05, compaction is small or absent; apart from elastic strains in the minerals, dilatancy predominates, beginning at 50 to 75 percent of the fracture stress difference. When initial porosity exceeds about 0.05, compaction and dilatancy may overlap. The onset of dilatancy has not been identified, but most of the dilatancy occurs within about 10 percent of the fracture stress difference. In low porosity rocks, dilatancy increases initial porosity by a factor of 2 or more; in porous rocks or granular aggregates the increase is only 20 to 50 percent. However, the actual pore volume increase is larger in rocks of high initial porosity. Hence, earthquake precursors which depend on the magnitude of dilatancy should be more pronounced in porous rocks or in fault gouge. In contrast, precursors which are based on fractional changes in some porosity-related property may be more pronounced in rocks of low initial porosity. Future work is particularly needed on constitutive relations suitable for major classes of rocks, on the effects of stress cycling in porous rocks, on the effects of high temperature and pore fluids on dilatancy and compaction, and on the degree of localization of strain prior to fracture.
139 citations
TL;DR: In this paper, all available data of the vertical ozone distribution measured with chemical sondes have been assembled and combined with one year's results from the BUV satellite to obtain the best possible information on the VNO distribution averaged over longitude as a function of season (month by month).
Abstract: All available data of the vertical ozone distribution measured with chemical sondes have been assembled and combined with one year's results from the BUV satellite to obtain the best possible information on the vertical ozone distribution averaged over longitude as a function of season (month by month). For the southern hemisphere Umkehr data have been used as a guideline in the necessary smoothing procedure. Especially in the northern hemisphere considerable adaptation to the observed latitudinal mean of the total amount was needed because most sounding stations, are situated in upper air trough positions. The results are presented as vertical distributions, as meridional cross sections of partial pressure and of mixing ratio and as partial pressure isolines as a function of latitude and season at different levels. The interaction between photochemical processes and transport resonsible for the observed distribution is briefly discussed.
114 citations
TL;DR: In this paper, the authors studied the effect of stress on the fluid permeability of geologic materials and found that flow along joints was very sensitive to effected stress changes, a fourfold change being caused by as little as 1.0 MPa.
Abstract: Stress produces dramatic changes in fluid permeability of geologic materials. An increase of nearly threefold occurred in granite at high stress, an increase of 20 percent in sandstone, and a hundredfold decrease in compacted sand. Permeability of sand and sandstone did not follow the effective stress law. Flow along joints was very sensitive to effected stress changes, a fourfold change being caused by as little as 1.0 MPa.
112 citations
Abstract: A series of stress relaxation experiments have been carried out on faulted and intact Tennessee sandstone to explore the influence of pore water on strength at different strain rates. Temperatures employed were 20, 300 and 400°C, effective confining pressure was 1.5 kb and strain rates as low as 10−10 sec−1 were achieved. Most samples were prefaulted at 2.5 kb confining pressure and room temperature. This is thought to have secured a reproducible initial microstructure.
109 citations
TL;DR: In this paper, the real area of contact has been determined, and measurements of the maximum and average surface temperatures generated during frictional sliding along precut surfaces in Tennessee sandstone have been made, through the use of thermodyes.
Abstract: The real area of contact has been determined, and measurements of the maximum and average surface temperatures generated during frictional sliding along precut surfaces in Tennessee sandstone have been made, through the use of thermodyes. Triaxial tests have been made at 50 MPa confining pressure and constant displacement rates of 10−2 to 10−6 cm/sec, and displacements up to 0.4 cm. At 0.2 cm of stable sliding, the maximum temperature decreases with decreasing nominal displacement rate from between 1150° to 1175°C at 10−2 cm/sec to between 75° to 115°C at 10−3 cm/sec. The average temperature of the surface is between 75 and 115°C at 10−2 cm/sec, but shows no rise from room temperature at 10−3 cm/sec. At 0.4 cm displacement, and in the stick-slip mode, as the nominal displacement rate decreases from 10−3 to 10−6 cm/sec, the maximum temperature decreases from between 1120° to 1150°C to between 1040° to 1065°C. The average surface temperature is 115° to 135°C at displacement rates from 2.6 × 10−3 to 10−4 cm/sec.
TL;DR: In this article, the authors show that the high and variable regional heat flow and the intense local heat discharge at volcanic centers in the Basin and Range province of the United States could be explained by regional and local variations in extensional strain rate without invoking anomalous conductive heat flow from the asthenosphere.
Abstract: In regions of tectonic extension, vertical convective transport of heat in the lithosphere is inevitable. The resulting departure of lithosphere temperature and thickness from conduction-model estimates depends upon the mechanical mode of extension and upon how rapidly extension is (and has been) taking place. Present knowledge of these processes is insufficient to provide adequate constraints on thermal models. The high and variable regional heat flow and the intense local heat discharge at volcanic centers in the Basin and Range province of the United States could be accounted for by regional and local variations in extensional strain rate without invoking anomalous conductive heat flow from the asthenosphere. Anomalous surface heat flow typical of the province could be generated by distributed extension at average rates of about 1/2 to 1%/m.y., similar to rates estimated from structural evidence. To account for higher heat flow in subregions like the Battle mountain High, these rates would be increased by a factor of about 3, and locally at active bimodal volcanic centers, by an order of magnitude more.
TL;DR: In this article, a relation between earthquake swarms and local crustal spreading is found in the San Andreas system, where faults have dominantly strike-slip motion with right-lateral displacement.
Abstract: Earthquake swarms in California are often localized to areas within dextral offsets in the linear trend in active fault strands, suggesting a relation between earthquake swarms and local crustal spreading. Local crustal spreading is required by the geometry of dextral offsets when, as in the San Andreas system, faults have dominantly strike-slip motion with right-lateral displacement. Three clear examples of this relation occur in the Imperial Valley, Coso Hot Springs, and the Danville region, all in California. The first two of these areas are known for their Holocene volcanism and geothermal potential, which is consistent with crustal spreading and magmatic intrusion. The third example, however, shows no evidence for volcanism or geothermal activity at the surface.
TL;DR: In this article, the global source, distribution, and fluxes of non-methane organic matter are investigated. But, the authors admit that less is known about the global sources and distribution of organic matter than any other major class of chemical substances in the atmosphere.
Abstract: Perhaps less is known about the global source, distribution, and fluxes of non-methane organic matter than any other major class of chemical substances in the atmosphere. Source strength estimates and consideration of the available concentration data suggest that the quantity of organic carbon on large particles (d>1 μm) in the global troposphere can be explained by primary emissions from anthropogenic sources and such natural sources as the ocean, crustal weathering, and forest wildfires. However, these pollution and natural sources apparently cannot account for the global tropospheric burden of small particle (d<1 μm) organic carbon. Approximately 80–160 MT/yr of small particle carbon from some additional source is required to balance this cycle. Possibilities include direct production from the leaves of vegetation and gas to particle conversion of natural and anthropogenic organic carbon compounds. The estimated production of reactive vapor phase organic compounds from natural and pollution sources is sufficient to account for the mass of this additional small particle organic carbon. However, considerably more data is required on the global distribution, source strengths, reaction pathways and rates, and removal mechanisms before an accurate description of the non-methane organic carbon cycle can be made.
TL;DR: Fault gouges have been observed in the surface outcrops, in shallow excavations, and in deep (300 meters below the surface) tunnels and mines in fault zones as mentioned in this paper.
Abstract: Fault gouges have been observed in the surface outcrops, in shallow excavations, and in deep (300 meters below the surface) tunnels and mines in fault zones. The 2-microns fractions in these fault gouges may compose a few percent to more than fifty percent of the total mass in the outcrops, and the mineralogy of the 2-microns fractions consists of a variety of clays (the common ones are montmorillonite, illite, kaolinite, chlorite, vermiculite and mixed-layer clays) and some quartz, feldspars, etc.
TL;DR: In this article, the authors used the T SiO2 for new estimates of regional heat flow where conventional data are lacking and presented a preliminary heat flow map based on equation (1).
Abstract: Application of the silica geothermometer to over 70,000 non-thermal groundwaters from the United States has shown that there is a correlation between the average silica geotemperatures for a region (T SiO2 in °C) and the known regional heat flow (q in mW m-2) of the form: (Equation) where m and b are constants determined to be 0.67°C m2 mW-1 and 13.2°C respectively. The physical significance of ‘b’ is the mean annual air temperature. The slope ‘m’ is related to the minimum average depth to which the groundwaters may circulate. This minimum depth is estimated to be between 1.4 and 2.0 km depending on the rock type. A preliminary heat flow map based on equation (1) is presented using the T SiO2 for new estimates of regional heat flow where conventional data are lacking. Anomalously high local T SiO2 values indicate potential geothermal areas.
TL;DR: In this paper, a simple model is discussed to evaluate reservoir lifetime and heat recovery factor in geothermal aquifers used for urban heating, and it is shown that reinjection of heat depleted water greatly enhances heat recovery and reservoir lifetime, and can be optimized for maximum heat production.
Abstract: Simple models are discussed to evaluate reservoir lifetime and heat recovery factor in geothermal aquifers used for urban heating. By comparing various single well and doublet production schemes, it is shown that reinjection of heat depleted water greatly enhances heat recovery and reservoir lifetime, and can be optimized for maximum heat production. It is concluded that geothermal aquifer production should be unitized, as is already done in oil and gas reservoirs.
TL;DR: In this paper, the authors reviewed many of the mechanical properties of faulted and jointed rock under pressure and temperature and in the presence of water, and found that the type of sliding motion, whether stick-slip or stable sliding, is much more affected by environmental and mineralogical factors.
Abstract: This paper reviews many of the mechanical properties of faulted and jointed rock under pressure and temperature and in the presence of water. At low effective confining pressures (below about 1 kilobar), the friction strength is quite variable and depends on the frictional resistance between gouge particles or asperities and on the dilatancy of the fault. At higher pressures the friction strength is nearly independent of mineralogy, temperature, and rate, at least for rocks whose friction strength is less than the failure strength. Water tends to slightly weaken the fault. The type of sliding motion, whether stick-slip or stable sliding, is much more affected by environmental and mineralogical factors. In general, stick-slip is dominant at high pressures and low temperatures, in the presence of strong minerals such as quartz and feldspar, in the absence of gouge, for lower surface roughness, and perhaps in the presence of water. The microscopic deformation mechanisms are poorly understood. At low temperatures, cataclasis dominates in rocks containing mostly quartz or feldspar, and plastic deformation in rocks containing mostly calcite or platy silicates. At high temperature most minerals deform plastically, producing a greater temperature-and rate-dependence of the friction strength. Glass has been found in some sliding surfaces in sandstone.
TL;DR: In this paper, the largest contribution to changes arises from the Pacific equatorial upwelling region, with the Indian Ocean and Atlantic contributing only small fractions to the variance, with photosynthesis contributing to a lowering of the partial pressure of CO2 in the sea.
Abstract: Changes of atmospheric CO2 concentration since 1958 are shown to be related to sea surface temperature changes. The largest contribution to changes arises from the Pacific equatorial upwelling region, with the Indian Ocean and Atlantic contributing only small fractions to the variance. It is hypothesized that the observed relationship is related to the nutrients that are brought up by upwelling cold water, with photosynthesis contributing to a lowering of the partial pressure of CO2 in the sea and thus to a greater tendency for a flux from the air to the sea.
TL;DR: In this paper, it was shown that the atmosphere near the ground contains a mixed population of pollen and spores in the 1 to 90 μm diameter range, and that long distance transport of pollen by wind is demonstrated by sampling from aircraft, and supported by much circumstantial evidence.
Abstract: The atmosphere near the ground contains a mixed population of pollen and spores in the 1 to 90 μm diameter range. Continuous sampling at Rothamsted Experimental Station at 2 m above ground level indicated concentrations averaging 12,000 m−3 over 5 summer months, but 1 million m−3 can occur for short periods. Concentrations change rapidly with locality, season, time of day or night and weather. Normally concentration in the troposphere decreases logarithmically with height. The occurrence of long distance transport of pollen and spores by wind is demonstrated by sampling from aircraft, and supported by much circumstantial evidence. Possible effects of this air spora on the atmosphere may be sought in alterations to: opacity, ionization, condensation nuclei, and sinks for minor gases.
TL;DR: In this article, a review of simple models and observations suggests that the main first-order features of active faulting may be explained by a single characteristic of crustal faults: the spatial variation of the effective frictional stress, which resists slippage on faults.
Abstract: A review of simple models and observations suggests that the main first-order features of active faulting — mechanical instability, the frequency—magnitude relations, seismic and aseismic slip, seismic radiation, incoherency and rupture stoppage — may be explained by a single characteristic of crustal faults: the spatial variation of the effective frictional stress, which resists slippage on faults. Fault offset data suggest that rupture propagation ceases in regions of high resistance which act as barriers. In these regions slippage is associated with negative stress drop. The spacing λ and the amplitude A(λ) of the barriers, as inferred from the frequency—magnitude and moment relation for earthquakes, obeys a simple statistical relation A(λ) ~ λρ. On the scale of particle motion, this variability of frictional stress provides a mechanical instability which may be associated with the concept of dynamic friction. Invariably, the rapid particle motion in the model is always preceded by accelerated creep. The particle acceleration is highly irregular, giving rise to an almost random acceleration record on the fault. The particle displacement is relatively smooth, giving rise to simple displacement time function in the far field. Rupture propagation time is approximately proportional to the gradient of frictional stress along the fault. Consequently sharp changes of this stress may cause multiple events and other long period irregularities in the fault motion.
TL;DR: In this paper, the spectral behavior of the magnetic field from the Alaskar pipeline was analyzed using data from standard geomagnetic observatories to establish the predictable patterns of temporal and spatial changes for field pulsation periods between 5 min and 4 hr.
Abstract: The Alaskar pipeline is a highly conducting anomaly extending 800 miles (1300 km) from about 62° to 69° geomagnetic latitude beneath the most active regions of the ionospheric electrojet current. The spectral behavior of the magnetic field from this current was analyzed using data from standard geomagnetic observatories to establish the predictable patterns of temporal and spatial changes for field pulsation periods between 5 min and 4 hr. Such behavior is presented in a series of tables, graphs and formulae. Using 2- and 3-layer models of the conducting earth, the induced electric fields associated with the geomagnetic changes were established. From the direct relationship of the current to the geomagnetic field variation patterns one can infer counterpart temporal and spatial characteristics of the pipeline current. The relationship of the field amplitudes to geomagnetic activity indices,A
p, and the established occurrence of various levels ofA
p over several solar cycles were employed to show that about half of the time the induced currents in the pipe would be under 1 A for the maximum response oscillatory periods near 1 hr. Such currents should be of minimal consequence in corrosion effects for even a section of the pipeline unprotected by sacrificial electrodes. Of greater interest was the result that the extreme surges of current should reach over one-hundred amperes in the pipeline during high activity.
TL;DR: In this article, the authors used a servo-loading system in combination with a high resolution digital computer recording system to obtain a more realistic picture of the stick-slip mechanisms and the stress drop associated with unstable slip.
Abstract: Laboratory room temperature triaxial friction tests on sawcut granite and serpentinite specimens suggest that stick-slip at high confining pressures is preceded by dilatancy in the intact rock adjacent to the shear surface. By using a fast-reacting servo-loading system in combination with a high resolution digital computer recording system it is possible to obtain a more realistic picture of the stick-slip mechanisms and the stress drop associated with unstable slip. Fracturing in granite under biaxial loading leads to a significant anisotropy in dilation and P-wave velocity of the rock. Velocity decreases remarkably in the directions of minor principal stresses with no indication for velocity recovery before macroscopic shear fracture development.
TL;DR: In this article, a light weight cryogenic sampling device has been constructed for the measurement of atmospheric radical concentrations using condensation of atmospheric CO2 or H2O at 77 K for matrix formation and trapping of the radicals.
Abstract: With some special adaptations the technique of matrix isolation followed by detection through electron paramagnetic resonance (EPR) can also be used for the measurement of atmospheric radical concentrations. A light weight cryogenic sampling device has been constructed. It uses condensation of atmospheric CO2 or H2O at 77 K for matrix formation and trapping of the radicals. The sampler has been flown on a balloon for stratospheric sampling. First data on stratospheric, HO2 and NO2 at 32 km altitude have been obtained on a flight on 8 August 1976 and will be reported.
TL;DR: In this paper, the role of gravity waves in the troposphere is briefly discussed and reviewed, and the physical processes involved in the interaction of gravity wave with mesoscale and planetary boundary layer phenomena are discussed.
Abstract: The nature and the role of gravity waves in the troposphere is briefly discussed and reviewed. After describing some basic properties of gravity waves and their generation mechanisms, we analyze their ability to influence phase changes, trigger and organize convective cells, to produce and interact with turbulence, and to affect diffusive processes in the atmosphere. Throughout, the emphasis is placed on the physical processes involved in the interaction of gravity waves with mesoscale and planetary boundary layer phenomena. Also discussed and reviewed are those remote sensing devices which are particularly useful in revealing and measuring such waves. Finally, an attempt is made to outline possible lines of future work for the purpose of fully understanding the role of gravity waves in mesoscale and microscale dynamics.
TL;DR: In this article, a one-dimensional steady-state, stratospheric model was used to calculate ozone changes coused by atmosphric injections of NOx, N2O and chlorofluoromethanes.
Abstract: With the aid of a one-dimensional steady-state, stratospheric model we have calculated ozone changes coused by atmosphric injections of NOx, N2O and chlorofluoromethanes. Adopting the fast rate constant, for the reaction HO2+NO»OH+NO2 measured by Howard and Evenson, we calculate much smaller perturbations of the ozone layer by NOx and N2O additions than previously estimated, but about two times larger ozone reductions as a result of continued emissions of chlorofluoromethanes, CF2Cl2 and CFCl3. The model results are sensitive to adopted values for the rate coefficients for the reactions HO2+O3»OH+2O2 and OH+HO2»H2O+O2 and the eddy diffusion profile near the tropopause. More accurate assessments of ozone perturbations require the development of photochemical models that incorporate meteorological processes in more than one dimension.
TL;DR: In this paper, the N2O content of waters in the Potomac and Merrimack Rivers was measured on a number of occasions over the period April to July 1977.
Abstract: The N2O content of waters in the Potomac and Merrimack Rivers was measured on a number of occasions over the period April to July 1977. The concentrations of dissolved N2O exceeded those which would apply in equilibrium with air by factors ranging from about 46 in the Potomac to 1.2 in the Merrimack. Highest concentrations of dissolved N2O were associated with sewage discharges from the vicinity of Washington, D. C., and analysis indicates a relatively high yield, 1.3 to 11%, for prompt conversion of waste nitrogen to N2O. Measurements of dissolved N2O in fresh water ponds near Boston demonstrated that aquatic systems provide both strong sources and sinks for atmospheric N2O.
TL;DR: A detailed assessment of the atmospheric hydrocarbon reaction system has been limited by a lack of observational information on the nature of conditions in the remote or non-urban atmosphere, as shown in this article.
Abstract: Trace concentrations of highly reactive hydrocarbons of biogenic origin have been proposed for some time as being important in aerosol formation processes in the atmosphere. More recently, assessments of potential photochemical reactions in the troposphere have proposed a role in the atmospheric ozone cycle for hydrocarbons, even for compounds such as methane that had previously been considered nonreactive. An assessment of the atmospheric hydrocarbon reaction system has been limited by a lack of observational information on the nature of conditions in the remote or non-urban atmosphere. Recent data on terpene concentrations and other biogenic hydrocarbon compounds are presented. Data on ethane and acetylene from aircraft samples taken over the north and south Pacific Ocean show concentrations in the 0.5 to 1 μ/m3 range for ethane and in the 0.05 to 0.3 μg/m3 range for acetylene. A concentration gradient is present for these compounds between the northern and southern hemisphere. A rudimentary global concentration pattern for these C2 compounds has been developed on the basis of recent data.
TL;DR: The average of the marine heat flow measurements in the Levantine Sea is 25.7 ± 8.4 mW/m2, and the heat flow on Cyprus is 28.0 ±8.0 mW /m2.
Abstract: Heat flow data from the eastern Mediterranean region indicates an extensive area of low heat flow, spreading over the whole basin of the Mediterranean east of Crete (Levantine Sea), Cyprus, and northern Egypt. The average of the marine heat flow measurements in the Levantine Sea is 25.7 ± 8.4 mW/m2, and the heat flow on Cyprus is 28.0 ±8.0 mW/m2. The estimated values of heat flow in northern Egypt range from 38.3 ± 7.0 to 49.9 ±9.3 mW/m2, apparently with no consistent trend. To the east, on the coast of Israel, the heat flow values increase, ranging from 36.6 ± 22.4 to 56.7 ± 14.2 mW/m2 along a SSE trend. The trend apparently correlates with an increase in crustal thickness, which is about 23 km at the north-west base of the Nile-Delta-cone, and close to 40 km beneath Israel.
TL;DR: In this paper, it was shown that direct nitrogen isotope measurements of atmospheric ammonia at Julich are in the expected range calculated from the δ ranges of different sources, which is explained by isotope fractionations during rainout and washout.
Abstract: Preliminary nitrogen isotope data for ammonia from animal urine, fuel combustion, fertilizer use and fertilizer factories have been measured or estimated. It turns out that direct nitrogen isotope measurements of atmospheric ammonia at Julich are in the expected range calculated from the δ ranges of different sources. For deposition of atmospheric ammonium in Julich-rain a depletion in15N with respect to atmospheric ammonia has been found which is explained by isotope fractionations during rainout and washout. In correspondence with this fractionation model are nitrogen isotope data of rain-ammonium from coastal areas, which are enriched in15N due to the fact that sea water acts as a sink for atmospheric ammonia. For Julich rain-nitrate a pronounced seasonal trend has been detected with lower15N data in spring and summer than in autumn and winter. This trend is interpreted by different nitrogen isotope data of anthropogenic and natural nitric oxides which have been measured or estimated from isotope fractionation effects during nitrification and denitrification reactions in soils. It should be possible to get better global estimations for anthropogenic and natural nitric oxides from nitrogen isotope measurements.