Stable isotopic measurements of atmospheric CO (¹³CO, C¹⁸O) were carried out at three season in a middle size city, Mainz in Germany. CO stable isotopic compositions of car exhaust fueled by gasoline, diesel and natural gas were also measured and showed different isotopic compositions (δ¹⁸O vs. V-SMOW = 22.3 ± 0.3‰, 10.9 ± 0.8‰, 20.1 ± 1.0‰ and δ¹³C vs. V-PDB = -29.9 ± 0.3‰, -22.2 ± 1.1‰, -51.3 ± 1.5‰, respectively). The ¹⁸O/¹⁶O ratios of atmospheric CO in Mainz show a clear linear correlation with the reciprocal concentration of CO. This reveals the contribution of CO emitted from a single pollution source (δ¹⁸O = 20.7 ± 0.5‰ V-SMOW), whose isotopic composition is close to that of CO from a gasoline engine combustion. From this value and car exhaust measurements, about 14 ± 7% of CO in Mainz air is estimated to originate from diesel fuel engine combustion. The oxygen isotopic composition can be used as a good indicator of contamination from car exhausts. On the other hand, the ¹³C/¹²C ratios of CO do not show a clear relationship with the reciprocal concentration of CO.

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Element accumulation rates for 19 elements in 11 sediment cores from the Southwestern Pacific Basin have been computed. Fe, Mn, V, Co, Ni, Cu, Zn and Pb show highest accumulation rates in sediments taken in the vicinity of the East Pacific Rise. These rates reflect a hydrothermal component in the sediments but are not as high as previously reported for other oceanic spreading centres. As expected, the deposition rate of the hydrothermal component shows a steep fall-off with distance from the crest of the East Pacific Rise. Accumulation rates for the authigenic elements are generally within the range found by other authors. Ignoring the sediments in the vicinity of the East Pacific Rise, the detrital component is seen to be the dominant component in the red clays form the Southwestern Pacific Basin. On average, these clays consist of the following components (on a carbonate-free basis): detrital (92.0%), hydrothermal (0.0%), biogenic (4.9%), hydrogenous (1.6%) and residue (1.5%).

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Sulfur cycles in micro zones of sediments at a tidal flat was investigated using isotope fractionation (δ³⁴S) of sulfate, acid volatile sulfides (AVS), and pyrite. Aerobic oxidation is major driving force for the sulfur cycle in the sediments that located very close to the sediment surface (0.5 mm depth from the sediment surface) in the tidal flat. During this cycle isotopically light sulfate is accumulated. Shift of δ³⁴S values of the sulfate toward positive direction proceeds with reduction by sulfur reduction bacteria (SRB) under anoxic conditions at depths between 0.5 cm and 7 cm below the sediment surface: At the depth where the shells locate (15 cm below the sediment surface), the major sulfur compound is pyrite. The δ³⁴S values of the AVS are between those of sulfate and pyrite for sediment samples collected at both inside and outside the shells. Although sulfate δ³⁴S and pyrite δ³⁴S values are almost the same for the inside and outside of the shells, the difference of the AVS δ³⁴S values between the inside and outside is quite significant. Seasonal variation of δ³⁴S values was also observed for the AVS. Unknown sulfur oxidizing bacteria (SB), which oxidize AVS into sulfate accompanying significant sulfur isotope fractionation under anoxic conditions, may play the major role of the isotope fractionation.

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Strontium isotope ratios in whole fibrous diamonds from Zaire do not correlate with Rb/Sr ratios, but with La/Ba and La/Nd ratios. Diamonds with lower La/Ba and higher La/Nd gave higher ⁸⁷Sr/⁸⁶Sr. Leaching experiments on crushed diamonds gave lower La/Ba and higher La/Nd for water leachate and higher La/Ba and lower La/Nd for acid leachate, and more importantly, the former has higher ⁸⁷Sr/⁸⁶Sr ratios than the latter, which is in accord with the experiments of whole diamonds. The two leachates are considered to be from water-rich fluid and carbonates, respectively. It is likely that the diamonds have formed in the environment where water-rich fluid and carbonate-rich fluid or melt were mixing and that the mixing may have triggered kimberlitic magmatism.

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Oxygen isotope fractionations involving carbonates and sulfates have been controversial for a long time. There are important unresolved conflicts among the results of theoretical calculations, experimental measurements and empirical estimates. In this paper, the increment method is adapted to systematically evaluate oxygen isotope fractionations in the carbonates and sulfates. The following sequence of ¹⁸-enrichment in carbonate minerals is obtained: siderite > ankerite > magnesite ≥ dolomite > calcite > aragonite > strontianite > cerussite ≥ witherite. The sequence of ¹⁸O-enrichment in sulfate minerals is predicted as follows: anhydrite > celestite > barite > anglesite. The internally consistent fractionation factors for the systems carbonate-water and sulfate-water are acquired for a temperature range of 0 to 1200°C, which are in fair agreement with existing experimental and/or empirical data. The present calculations suggest that dolomite should behave isotopically like calcite; equilibrium fractionation between dolomite and calcite is only 0.56‰ at 25°C. Aragonite is predicted to be significantly depleted in ¹⁸O relative to calcite; equilibrium fractionation between calcite and aragonite is 4.47‰ at 25°C. It is possible that polymorphic transition from aragonite to calcite could proceed through an essentially intact oxygen structure without isotopic resetting. As a result, the temperature dependence of oxygen isotope partitioning in aragonite could be conveyed to calcite. Oxygen isotope inheritance in calcite formation by the polymorphic transition may be of critical importance in attempts to resolve dilemma involving fractionations in aragonite-calcite-dolomite-water systems.

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Carbon isotopic ratios (¹³C/¹²C) of methane, ethane and propane were analyzed for natural gases from several oil and gas fields in Niigata and Akita in Japan. A strong correlation between δ¹³C(C₂H₆) and δ¹³C(C₃H₈) was observed. This relation is well explained by a kinetic theory proposed by Chung et al. (1988). It propounds that carbon isotopic ratios of the gases are mainly decided by kinetics. on the other hand, only a weak correlation was observed between δ¹³C(CH₄) and δ¹³C(C₂H₆). The weak correlation is inferred to be due to mixing of biogenic gas that has low δ¹³C(CH₄). Further, δ¹³C of source kerogen of these gases can be calculated from δ¹³C(C₂H₆) and δ¹³C(C₃H₈). It is inferred that δ¹³C of source kerogen of the gases in Akita and Niigata are close to each other.

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Samples for lead isotope measurements are generally loaded with silica-gel as the activator, and phosphoric acid. Then, the silica-gel, sample mixture is fused into glass on the filament by passing a high current for a short instant before mass-spectrometer analysis. Here, we use a timer to control the electric power supply for the sample loading unit thus insuring a constant condition for loading. The ion beam thus obtained was found to be more stable than the conventional method. No significant change of isotopic composition was observed within a single run under this condition. The overall range of mass fractionation is insignificant for a sample size between 250 and 25 ng. Repeated analyses (n = 15) of NBS SRM-981 gave the following grand means and reproducibility: ²⁰⁶Pb/²⁰⁴Pb = 16.8908 ± 0.0026 (1σ SD); ²⁰⁷Pb/²⁰⁴Pb = 15.4285 ± 0.0025; ²⁰⁸Pb/²⁰⁴Pb = 36.4982 ± 0.0066.

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