The photo degradation kinetics of fenitrothion in various water media were examined under both direct and indirect photolysis with respect to degradation rate, half-life, and phototransformation kinetics of fenitrothion. The effect of fenitrothion and its photoproducts on steroid hormone biosynthesis was also investigated. The results indicate that the degradation rate of fenitrothion under indirect photolysis to which nitrate was added was faster than that of direct photolysis, in both pure and natural water. The fenitrothion half-lives under indirect photolysis were 2.67 and 4.58 h, while under direct photolysis the half-lives were 3.58 and 5.66 h for natural and pure water, respectively. The phototransformation kinetics of fenitrothion in pure water showed that the identified photoproducts, such as fenitrooxon and 3-methyl-4-nitrophenol, under both direct and indirect photolysis were almost the same. This is evidence that there is no specific degradation pathway with hydroxyl radicals under indirect photolysis in fenitrothion transformation. The 1 μM∼50 μM levels of fenitrothion and two of its photoproducts (fenitrooxon and 3-methyl-4-nitrophenol) altered the steroid hormones biosynthesis in bovine adrenal cultured cells, which suggests that both fenitrothion and its two photoproducts may be endocrine-disrupting compounds.

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Metagraywackes and metapelites from the Paleoproterozoic Birimian Supergroup in the Birim diamondiferous field, southern Ghana, were analyzed for their major and trace element contents. Compared to early Proterozoic crust, the metasedimentary rocks are enriched in ferromagnesian elements but depleted in rare earth elements (REE), high field strength elements (HFSE) (with exception of Zr), and Th. They show REE patterns similar to their Archean counterparts. The chemical data indicate that the sediments were derived from a local source of mixed felsic—mafic composition, with the latter dominating. The source rocks were the basaltic to dacitic volcanic rocks and granitoids within the Birimian greenstone belts. The chemical data further suggest their deposition in a tectonic setting comparable to modern island arcs, and that minimal old upper crust (i.e., pre-Birimian sources) was involved in their formation. The analyzed metasedimentary rocks have Eu-anomalies and Gd_N/Yb_N, Sm/Nd, Th/Sc, Cr/Sc and Cr/Th ratios that closely resemble those of their Archean counterparts, and therefore inconsistent with models suggesting abrupt compositional changes in upper crust at the Archean-Proterozoic boundary.

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Using a laser ablation-inductively coupled plasma mass spectrometer (LA-ICPMS), U-Pb age and rare earth element (REE) abundances have been determined simultaneously from a single 20 μm ablation pit of zircon. The laser ablation system utilizing 193 nm wave-length ArF excimer laser produces stable and reproducible signal intensities resulted in good precisions on measurements of element concentrations and isotopic ratios. Because of the higher energy density of the deep ultra-violet laser beam, ablation fractionation between Pb and U were reduced even with the prolonged ablation, and thus accuracy of Pb-U age was improved significantly. A chicane-type ion lens system was applied to a quadrupole-based ICPMS instrument. With the chicane ion lens, higher elemental sensitivity (4 times for light mass range and 3 times for mid to heavy mass range) and lower white background (<5 cps for light to mid mass range and <2 cps for heavy mass range) were achieved. This further improved analytical precisions for low concentration elements in samples. The ²³⁸U-²⁰⁶Pb ages for Nancy standard zircon (Nancy 91500), SHRIMP calibration standard zircon (SL13) and Antarctic zircon (PMA7) obtained in this study were 1064 ± 24 Ma, 569 ± 78 Ma and 2438 ± 101 Ma (2-sigma), respectively. Relative age differences from previous reports were 0.2%, 0.4% and 3.2% respectively, demonstrative of high reliability of the method. The REE abundances in zircon samples were calibrated using a NIST 610 glass standard reference material. The resulting REE abundance data for zircons (Nancy 91500 and SL13) show good agreement with those for literature values within the analytical precision of ∼20%. The matrix effect that may occur between the synthetic glass standard and zircon crystals is obviously smaller than the precision and thus negligible for this precision levels. The data presented here demonstrate clearly that the combination of ArF excimer laser and ICPMS equipped with the chicane ion lens has a potential to become a significant tool for zircon geochemistry.

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In order to provide a time constraint on the ¹³C-depleted kerogen formation in silica dikes that intruded 3.5 Ga greenstone from Pilbara Craton in Western Australia, we have carried out an ion microprobe U-Pb dating and rare earth element (REE) analysis of apatite from one of the dikes. Two types of apatite were identified in the dike, based on their occurrences. One is stick-shape apatites (Type 1 apatite) in secondary silica micro-veins that cut the silica dike. The other is granular apatites (Type 2 apatite) that occur in matrix of the silica dike. Occurrence in the secondary micro-veins (Type 1), non-igneous REE patterns (Type 1 and 2), chemical zoning (some of Type 1 and 2), iron sulfide within apatite (some of Type 2), and intergrowth of apatite and sulfide (some of Type 2) suggest that both types of apatite were crystallized in the silica dike. Ion microprobe U-Pb dating of Type 1 apatite did not give a well-constrained age, while Type 2 apatite yields a Tera-Wasserburg concordia intercept age of 3214 ± 140 Ma (95% confidence level, MSWD = 0.6) in a three-dimensional ²³⁸U/²⁰⁶Pb-²⁰⁷Pb/²⁰⁶Pb-²⁰⁴Pb/²⁰⁶Pb diagram, and a ²⁰⁴Pb/²⁰⁶Pb-²⁰⁷Pb/²⁰⁶Pb isochron age of 3191 ± 150 Ma (95% confidence level, MSWD = 0.5). It is difficult to judge whether the U-Pb and Pb-Pb age of Type 2 apatite is crystallization age or metamorphic age, since the estimated range of closure temperature of U-Pb system in the apatite and that of metamorphic temperature is partly overlapped. In either case, it can be safely concluded that the minimum age of the dike and kerogen is 3.2 Ga. These ages might allow the interpretation that the kerogen was produced by biological carbon fixation and/or abiological reaction at least before 3.2 Ga.

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Studies on elemental analysis, Fourier transform infrared spectroscopy (FT-IR) and thermal decomposition (thermogravimetry, TG; and derivative thermogravimetry, DTG) of sedimentary fulvic (FA) and humic acids (HA) from marine, estuarine, lacustrine and terrestrial environments are presented. In general, H/C and N/C atomic ratios, as well as the infrared spectra, reflected the extent of the influence of algal and/or terrestrial organic matter sources on the samples, the aquatic (both, marine and freshwater) humic substances (HS) being richer in nitrogen and more saturated, than terrestrial materials. Comparison of properties of FA and HA from the same parent sediments showed that the latter are relatively richer in nitrogen and unsubstituted aliphatic chains and poorer in carboxylic groups. FT-IR spectra showed that the nitrogen present is mostly as forming part of amide groups. Concerning thermal degradation, two main steps were observed for all samples: the first, relative to the loss of moisture, being located between 40°C and 100°C and the second between 270°C and 440°C. FT-IR spectra of the samples which had been heated to 90°C, 400°C and 900°C showed that, upon heating, the carboxyl content decreases (especially for FA), the aliphaticity decreases and the aromaticity increases (especially for HA), indicating that the 270°C-470°C degradation step might be related to decarboxylation and unsaturation losses. In spite of this, both kinds of HS, were shown to be highly thermo-resistant materials retaining most of their typical original infrared spectral features, even after being heated to 400°C.

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We report a full suite of radiogenic, nucleogenic and fissiogenic noble gas compositions obtained by step-heating experiments from early Archaean Greenland zircons. We estimated activation energy (E_a) of diffusion and closure temperatures (T_c) for radiogenic ⁴He^∗ and fissiogenic ⁸⁶Kr^∗ and ¹³⁶Xe^∗ in zircons. These data demonstrate that the combined study of (U-Th)/He and (U-Th)/Kr-Xe can provide powerful geochronological information on cooling ages and crystallization ages from the same samples.

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Cadmium partition coefficients (D_Cd) between calcitic tests of the benthic foraminifera Ammonia beccarii (Linné) and brackish water were measured from sediment free microcosms. Dissolved cadmium concentrations were prepared at 4.3, 6.4 and 9.0 nmol l^-1 at 18°C and 2.3, 5.3 nmol l^-1 at 13°C and we obtained D_Cd of 1.8 ± 0.2 (n = 7), 1.0 ± 0.1 (n = 8), 1.2 ± 0.2 (n = 19), 2.8 ± 0.6 (n = 6) and 1.0 ± 0.2 (n = 10), respectively. The values of D_Cd close to 1.0 show that foraminiferal carbonates do not lead to a cadmium segregation with the surrounding water and in the light of these data, a published biomineralization model is discussed. The hypothesis of a diffusion limited uptake of ions during the mineralization process is developed to explain D_Cd ≅ 1.0. The hypothesis is tested by calculations in the case of sea water (warm surface, S = 35 psu) and culture experiments. These calculations revealed that carbonate diffusion time are consistent with the chamber formation time usually observed in culture experiments for this species. It shows that CO₃²⁺ is the first limiting ion but does not allow us to conclude that Ca²⁺ uptake is also diffusion limited. Equations showed that ion diffusion coefficients could also control D_Cd. From cultures 2.3 and 4.3 nmol l^-1, D_Cd was 2.8 ± 0.6 and 1.8 ± 0.2, respectively. The assumption of remaining living Dunaliella cells in the food of these cultures could lead to an unexpected absorption of Cd²⁺. The hypothesis of solution mixture during experiment stoping a diffusion limited uptake, could also explain these partitioning values.

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Air samples were collected in May and June 1995 from a gas and oil field area (Niigata) and areas of no known oil and gas deposits (Ibaraki and Gunma). The concentration of nonmethane hydrocarbons were measured. The concentration of ethane and propane in the air shows a positive correlation with ethylene regardless of the distance from the natural gas deposits. The correlation shows that emission from a natural gas deposit is not the major factor controlling atmospheric hydrocarbons. Automobile emission is considered to be a major source of ethane and propane because they correlate with acetylene, which is known to be mainly emitted from automobiles. A few samples collected in the vicinity of natural gas deposits shows high ethane and propane concentrations. This is presumed to be caused by emissions from oil and gas deposits.

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