A review of satellite, observations of atmospheric ozone

Since the first satellite ozone measurements in 1960, basically three methods have been developed: backscattered solar ultraviolet, infrared emission, and occultation. In a review article by Krueger et al. (1980, Phil. Trans. R. Soc. Lond. A296, 191), the authors examine the above satellite methods and data covering the period up to about 1980. Our purpose is to review the development of the satellite ozone methodology since about 1980 with particular emphasis on the relationship of satellite data to the continued need for ground-based observations. Finally, we look toward the future to the Upper Atmosphere Research Satellite, to be launched in about 1991, and the view that this is to be a collective experiment, not a series of independent measurements, focusing on the photochemistry and dynamics of the stratosphere.     

Estimation of chlorophyll fluorescence under natural illumination from hyperspectral data

This paper reports a series of laboratory and field measurements of spectral reflectance under artificial and natural light conditions which demonstrate that effects of natural chlorophyll fluorescence are observable in the reflectance red edge spectral region. These are results from the progress made to link physiologically-based indicators to optical indices from hyperspectral remote sensing in the Bioindicators of Forest Sustainability Project. This study is carried out on twelve sites of Acer saccharum M. in the Algoma Region, Ontario (Canada), where field measurements, laboratory-simulation experiments, and hyperspectral CASI imagery have been carried out in 1997, 1998, 1999 and 2000 campaigns. Leaf samples from the study sites have been used for reflectance and transmittance measurements with the Li-Cor Model 1800 integrating sphere apparatus coupled to an Ocean Optics Model ST1000 fibre spectrometer in which the same leaves are illuminated alternatively with and without fluorescence-exciting radiation. A study of the diurnal change in leaf reflectance spectra, combined with fluorescence measurements with the PAM-2000 Fluorometer show that the difference spectra are consistent with observed diurnal changes in steady-state fluorescence. Small canopies of Acer saccharum M. have been used for laboratory measurements with the CASI hyperspectral sensor, and under natural light conditions with a fibre spectrometer in diurnal trials, in which the variation of measured reflectance is shown experimentally to be consistent with a fluorescence signature imposed on the inherent leaf reflectance signature. Such reflectance changes due to CF are measurable under natural illumination conditions, although airborne experiments with the CASI hyperspectral sensor produced promising but less convincing results in two diurnal experiments carried out in 1999 and 2000, where small variations of reflectance due to the effect of CF were observed.     

Mapping Paleo‐Fire Boundaries from Binary Point Data: Comparing Interpolation Methods

Fire history studies have traditionally emphasized temporal rather than spatial properties of paleo‐fire regimes. In this study we compare four methods of mapping paleo‐fires in central Washington from binary point data: indicator kriging, inverse distance weighting, Thiessen polygons, and an expert approach. We evaluate the results of each mapping method using a test (validation) dataset and receiver operating characteristic plots. Interpolation methods perform well, but results vary with fire size and spatial pattern of points. Though all methods involve some subjectivity, automated interpolation methods perform well, are replicable, and can be applied across varying landscapes.     

Oxygen three-isotope fractionation lines in terrestrial silicate minerals: An inter-laboratory comparison of hydrothermal quartz and eclogitic garnet

Geochemical—and perhaps biochemical—processes may yield tell-tale proxies in rocks and minerals on the Earth or other planetary bodies, in the form of distinctive slopes of linear fractionation arrays on the oxygen three-isotope plot. It is generally recognized that kinetic and equilibrium fractionation processes are described by different mass fractionation laws. We show that coupled laser fluorination, dual-inlet IRMS procedures for oxygen three-isotope analysis of silicates, at high precision, gave reproducible accuracy for the slope value as measured independently by two different laboratories, using replicates of the same silicate samples. As far as we are aware, this is the first such inter-laboratory comparison. Hydrothermal quartz (together with one chalk flint sample) with a range in δ¹⁸O of 31‰ gave respective slope λ values of 0.5240 ± 0.0010 and 0.5242 ± 0.0010, using Prism III and MAT 253 mass spectrometers, respectively, at the Open University (OU). Errors were computed from weighted linear regression and are reported at the 95% confidence level. The comparable result obtained at the Geophysical Laboratory (GL), Carnegie Institution of Washington, was 0.5240 ± 0.0015. A MAT 252 mass spectrometer was used for the latter measurements and the oxygen extraction and purification procedures differed in detail from those used at the OU. In contrast, slopes measured for replicates of seven garnet samples, metamorphosed under high-temperature, high-pressure conditions, and spanning 20‰ in δ¹⁸O, gave 0.5262 ± 0.0008 at OU (Prism III analyses) and 0.5266 ± 0.0012 at GL.     

Adaptive local discontinuous Galerkin approximation to Richards’ equation

We propose a spatially and temporally adaptive solution to Richards’ equation based upon a local discontinuous Galerkin approximation in space and a high-order, backward difference method in time. We cast our approach in terms of a general, decoupled adaption algorithm based upon operators. We define non-unique instances of all operators to result in an adaption method from within the general class of methods that is defined. We formally decouple the spatial adaption from the temporal adaption using a method of lines approach and limit the temporal truncation error so that the total error is dominated by the spatial component. We use a multiple grid approach to guide adaption and support the data structures. Spatial adaption decisions are based upon error and regularity indicators, which are economical to compute. The resultant methods are compared for two test problems. The results show that the proposed adaption methods are superior to methods that adapt only in time and that in cases in which the problem has sufficient smoothness, adapting the order of the elements in addition to the grid spacing can further improve the efficiency of this robust solution approach.     

Fate and effects of picric acid and 2,6-DNT in marine environments: toxicity of degradation products

The toxicity of transformation products of 2,6-dinitrotoluene (2,6-DNT) and 2,4,6-trinitrophenol (picric acid) were assessed in spiked sandy and fine-grained marine sediments and in seawater. Toxicity of pore water from sediments spiked with 2,6-DNT decreased for the macro-alga, Ulva fasciata, zoospores as biotransformation proceeded, but increased for the copepod, Schizopera knabeni, nauplii. The primary biotransformation product of 2,6-DNT, 2-amino-6-nitrotoluene, was also more toxic than the parent compound to copepod nauplii, but not to alga zoospores, in spiked seawater tests. Two biotransformation products of picric acid, picramic acid and 2,4-DNP, were more toxic than their parent compound. Porewater toxicity from picric acid-spiked sediments decreased significantly at the end of six-months incubation. Fine-grained sediment spiked with either ordnance compound had lower toxicity than its sandy counterpart after six months, suggesting faster microbial transformation in the former and production of less toxic products. Photo-transformation of 2,6-DNT in seawater resulted in a reduction in toxicity.     

Part I. Decrepitation and degassing behaviour of quartz up to 1560 °C: Analysis of noble gases and halogens in complex fluid inclusion assemblages

Stepped heating and crushing experiments have been used to investigate the noble gas and halogen degassing behaviour of quartz in detail. Samples with diverse character were selected from the Eloise and Osborne, Iron Oxide Copper Gold (IOCG) ore deposits, and the Railway Fault, 13 km south of the Mt Isa Mine, in the Proterozoic Mt Isa Inlier of northeast Australia. Quartz has been shown to have a bimodal degassing profile. The first degassing mode at temperatures of <700 °C is caused by thermally induced mechanical decrepitation of fluid inclusions. Changes in the Br/Cl, I/Cl, Ar/Cl and ⁴⁰Ar/³⁶Ar composition of gas released at different temperatures up to 700 °C can be related to the decrepitation of different types of fluid inclusion observed by microthermometry. These variations with temperature permit deconvolution of the complex fluid inclusion assemblages associated with the IOCG samples; the ultra high salinity, multi solid (MS) and liquid-vapour-daughter (LVD) fluid inclusions, with a predominantly primary origin, decrepitate at higher temperatures than lower salinity liquid-vapour (LV) and monophase (M) fluid inclusions that have a predominantly secondary origin. Three of the IOCG samples have primary MS and LVD fluid inclusions characterized by molar Br/Cl values of between 0.25 × 10⁻³ and 0.66 × 10⁻³, I/Cl between 0.37 × 10⁻⁶ and 5.0 × 10⁻⁶, ⁴⁰Ar/³⁶Ar values of <1000 and low ³⁶Ar concentrations of 0.7-1.0 × 10⁻⁶ cm³ cm⁻³H₂O. These low values are most easily explained by the involvement of halite dissolution water in IOCG genesis. One of the IOCG samples has Br/Cl of 1.3-2.0 × 10⁻³ and I/Cl of 10 × 10⁻⁶, similar to juvenile magmatic fluids in Phanerozoic Porphyry Copper Deposits. This sample also has a higher ³⁶Ar concentration of 3.5 × 10⁻⁶ cm³ cm⁻³H₂O and a slightly elevated ⁴⁰Ar/³⁶Ar of 2236. Step heating reveals limited and non-systematic variation within the more homogenous population of LV fluid inclusions from the Railway Fault. The samples have mean values of 8.1 × 10⁻³ for Br/Cl; 9.4-12 × 10⁻⁶ for I/Cl; <2000 for ⁴⁰Ar/³⁶Ar; and 4.7-4.8 × 10⁻⁶ cm³ cm⁻³H₂O for ³⁶Ar concentration. The Br/Cl values are similar to those previously reported for basinal brines present in silicic alteration at the Mt Isa Mine and the additional data can be explained by interaction of such a bittern brine with fine grained sedimentary rocks in the sub-surface. The second mode of quartz degassing occurs between 1200 and 1450 °C and releases a greater volume of gas than the first degassing mode. Several lines of evidence, including microscope observations, indicate that the gas released at high temperature is also from the fluid inclusion reservoir. However, its release may be triggered by a metastable phase transition of quartz (∼1200 °C) and caution is required in interpretation of the fluid compositions obtained at these temperatures. The data provide an improved understanding of fluid inclusion decrepitation behaviour that is different to that obtained in lower temperatures experiments designed by other workers to investigate H-isotope fractionation.