The photochemistry of synoptic-scale ozone synthesis: Implications for the global tropospheric ozone budget

The oxidation of nonmethane hydrocarbons represents a source of tropospheric ozone that is primarily confined to the boundary layers of several highly industrialized regions. (Each region has an area greater than one million km²). Using a photochemical model, the global tropospheric ozone budget is reexamined by including the in-situ production from these localized regimes. The results from these calculations suggest that the net source due to this photochemistry, which takes place on the synoptic scale, is approximately as large as the amount calculated for global scale photochemical processes which consider only the oxidation of methane and carbon monoxide. Such a finding may have a considerable impact on our understanding of the tropospheric ozone budget. The model results for ozone show reasonable agreement with the climatological summer distribution of ozone and the oxides of nitrogen at the surface and with the vertical distribution of ozone and nonmethane hydrocarbons obtained during a 1980 field program.     

Hydrogeological and geotechnical aspects of the Tennessee-Tombigbee Waterway

The Tennessee-Tombigbee Waterway is in the East Gulf Coastal Plain physiographic province The River and Canal sections were constructed on the floodplain of the Tombigbee River Locks and dams in this section are founded on sediments of Upper Cretaceous age, composed predominantly of sands, clays, and silts of the Eutaw and Gordo formations The 39-mile long Divide Cut was excavated through higher topography which is underlain by these same formations, along with the McShan formation of similar character Bay Springs Lock and Dam, at the south end of the Divide Cut, is founded on shale of the Hartselle formation, which is Mississippian in age Comprehensive studies and tests were made to evaluate and monitor potential impacts of the waterway on the hydrogeologic environment Observations to date show that adverse impacts are very minimal overall, and these are partially offset by beneficial effects Geologic and groundwater conditions were primary factors in the location and design of major features of the waterway During construction, extensive control of groundwater and dewatering effort was required The excavation, utilization, and disposal of over 200 million cubic yards of material, construction of 10 locks and dams, and over 80 miles of canal were accomplished essentially as planned and designed within budget and ahead of schedule     

Phase equilibria involving humite minerals in impure dolomitic limestones

The natural occurrence of critical assemblages among the phases clinohumite, calcite, dolomite, tremolite, forsterite, diopside, chlorite, and spinel in metamorphosed impure limestones, together with experimental and thermodynamic data, permits the calculation of phase equilibria governing the stability of clinohumite in terms of the variables P, T, and composition of a CO₂-H₂O-HF fluid. Equilibrium constant expressions are given for 23 equilibria that describe the stable phase relations between the above phases. Pure OH-clinohumite is considered to be metastable at relatively low pressures. The occurrence of clinohumite in natural marbles is the result of nonideal fluorine substitution which increases the stability of clinohumite. The stability field for clinohumite +calcite, governed primarily by the equilibrium 4forsterite+dolomite+H₂O = clinohumite+calcite +CO₂, expands to more CO₂-rich fluid compositions with increasing fluorine contents and decreasing total pressure. The F/(F+OH) ratio of clinohumite coexisting with calcite, dolomite, and forsterite is a sensitive indicator of the composition of the mixedvolatile fluid phase. The thermodynamic model is in good agreement with observed phase relations and can be used to gain useful information concerning the P-T-X _fluid conditions responsible for the formation of clinohumite.     

Widespread occurrence of magnesiocummingtonite in ultramafic schists,Cima di Gagnone,Ticino, Switzerland

Abundant magnesiocummingtonite (space group P2₁/m) with Mg/(Mg+Fe) ratios between 0.85 and 0.89 occurs in lenses of schistose metaperidotite enclosed in kyanite-zone rocks of the Lepontine Alps, Ticino, Switzerland. It forms prisms and needles that extend homoaxially from cores of tremolite. Coexisting magnesian phases are olivine, orthopyroxene, talc, magnesite, and chlorite. Except for γ∶z, optical and structural properties of one example fall on extrapolations of existing determinative curves. Analogous to synthetic F-clinoamphiboles, zz∶z has a maximum at approximately 0.7 Mg/(Mg+Fe). Anthophyllite, of almost identical composition, occurs in the same region, often intergrown with cummingtonite along lamellae ‖(010) and ‖(100). Cummingtonite is believed to have partially inverted to anthophyllite during cooling.     

Interpretation of the 6818.9-Å methane line in terms of inhomogeneous scattering models for Uranus and Neptune

We have obtained high-resolution spectra of Uranus and Neptune in the methane transition near 6800 Å, and in particular, the 6818.9Å feature. Calculated equivalent widths for this line using recently proposed models of the atmospheres of these two planets indicate that the C/H ratio is greater than or equal to 5 × 10^?3 below the CH₄ saturation level. This value is 12 times the solar mixing ratio. The half-widths of the computed line profiles are in agreement with the observed half-widths. Therefore, it is unnecessary to introduce an unidentified constituent with an abundance comparable to H₂, postulated recently by Belton and Hayes, and by Bergstrahl, to account for the observed line broadening.     

Depositional history of the Lagniappe Delta,northern Gulf of Mexico

The northern Gulf of Mexico continental shelf is characterized by superimposing deltas. One such delta, informally named Lagniappe, extends east of the Mississippi Delta from mid-shelf to the continental slope. This late Wisconsinan delta is adjacent to, but not associated with the Mississippi Delta complex: the fluvial source was probably the ancient Pearl and/or Mobile Rivers. The fluvially dominated Lagniappe Delta is characterized by complex sigmoid-oblique seismic-reflection patterns, indicating delta switching of high-energy sand-prone facies to low-energy facies. The areal distribution and sediment thickness of the delta were partially controlled by two diapirs.     

Predicting surf zone injuries along the Delaware coast using a Bayesian network

Natural Hazards - More than 2000 surf zone injury (SZI) events, including 196 spinal injuries and 6 fatalities, were recorded at the five most populated beaches along the 25 miles of...     

Occurrence of negative epsilon in seismic hazard analysis deaggregation,and its impact on target spectra computation

This paper investigates circumstances behind the occurrence of negative ε (the normalized difference between the spectral acceleration of a recorded ground motion and the median response predicted by a ground motion prediction equation) in probabilistic seismic hazard deaggregation. Negative ε values are of engineering interest because of their impact on the conditional mean spectrum (CMS), which is a proposed alternative to the uniform hazard spectrum (UHS) as a target spectrum for ground motion selection. In the case where target ε values from deaggregation are positive, the CMS calculation produces relatively lower response spectra than the UHS. Positive target ε values occur almost universally in active seismic regions at long return periods of engineering interest, but the possibility of negative target ε values is important because in the case of negative target ε, some relationships between the CMS and UHS would reverse. This paper describes the calculation of target ε, performs parametric studies to determine when negative ε values occur in deaggregation, and investigates the potential impact on target spectrum calculation and ground motion selection. The case studies indicate that special seismicity models and certain ground motion prediction equations have the most significant effect on ε values and a combination of these characteristics in Eastern North America creates the most likely situation for negative target ε to occur. CMS results are nonintuitive when the target ε is negative, but it is not clear that this is a common practical concern because negative target ε occurs only in well‐constrained areas. Copyright © 2011 John Wiley & Sons, Ltd.