Mass-dependent fractionation of quadruple stable sulfur isotope system as a new tracer of sulfur biogeochemical cycles

Sulfur isotope studies of post-Archean terrestrial materials have focused on the ratio ³⁴S/³²S because additional isotopes, ³³S and ³⁶S, were thought to carry little information beyond the well-known mass-dependent relationship among multiple-isotope ratios. We report high-precision analyses of Δ³³S and Δ³⁶S values, defined as deviations of ³³S and ³⁶S from ideal mass-dependent relationships, for international reference materials and sedimentary sulfides of Phanerozoic age by using a fluorination technique with a dual-inlet isotope ratio mass spectrometer. Measured variations in Δ³³S and Δ³⁶S are explained as resulting from processes involve branching reactions (two or more reservoirs formed) or mixing. Irreversible processes in closed systems (Rayleigh distillation) amplify the isotope effect. We outline how this new isotope proxy can be used to gain new insights into fundamental aspects of the sulfur biogeochemical cycle, including additional constraints on seawater sulfate budget and processes in sedimentary sulfide formation. The isotope systematics discussed here cannot explain the much larger variation of Δ³³S and Δ³⁶S observed in Archean rock records. Furthermore, Phanerozoic samples we have studied show a characteristic Δ³³S and Δ³⁶S relationship that differs from those measured in Archean rocks and laboratory photolysis experiments. Thus, high precision analysis of Δ³³S and Δ³⁶S can be used to distinguish small non-zero Δ³³S and Δ³⁶S produced by mass-dependent processes from those produced by mass-independent processes in Archean rocks and extraterrestrial materials.     

The migration and distribution of Cubans and Puerto Ricans living in the United States

A new approach to solving some of the problems that information, education, and communication (IEC) programs have been facing is proposed. The approach is based on the use of the "Appropriate Practical and Technical Information Section Cube" (APTISC). The APTISC model can systematically identify 64 different types of IEC programs. The approach logically arises from the following principles of effective IEC and should therefore be acceptable: problem-oriented, people-oriented, practical oriented, and professional-or technical-oriented. To start developing the IEC program systematically, one begins by asking the following simple questions: what is the problem; who are the people responsible for these problems; and what type of professional or technical knowledge is needed to solve the lack of knowledge, attitude, practice, or IEC capabilities (KAPI). The problem may be lack of knowledge (K), attitude (A), practice (P), of IEC capabilities (I) or any combination of them. A lack of KAPI can arise from various groups of people, and these groups must be identified. The type of professional or technical knowledge needed to solve the lack of KAPI can be divided into 4 types, i.e., technical information, technical application, technical practice, and technical supervision. For the purpose of actually developing the program the identified cube can be broken down into 4 main components: M1 = man (who is the comminicator); M2 = message (to be received by the audience); M3 = method (to transmit the message); and M4 = media (to convey the message). Each of these components has to be identified before the program can be initiated. Other supporting components can also be considered, e.g., management, material, morale, and money. These should be analyzed in relation to IEC programs being developed. It is worth considering the application of the APTISC Approach in developing IEC programs. This approach will help maximize the effectiveness of available resources by concentrating them on the areas of greastest need.     

Sulphur contents of conifer needles in Great Britain

There is currently a lack of convincing evidence linking air pollution and tree health in Great Britain. Field surveys have not revealed a clear association between the spatial distribution of crown thinning and air pollution; the crown condition of some species is apparently better in more polluted areas. This has been attributed to the confounding effects of climate, which is known to have a marked effect on crown condition. In this study, analysis of total sulphur contents of needles ofPicea sitchensis ((Bong.) Carr.),P. abies ((L.) Karst.) andPinus sylvestris (L.) reveals marked patterns that are correlated with modelled atmospheric concentrations of sulphur dioxide. Correlations with other indices of sulphur pollution, including wet and dry deposition and sulphate aerosol concentrations, are less consistent. However, no association has been found between the sulphur contents of needles and the crown densities of trees in Britain.     

The direction of fluid flow during contact metamorphism of siliceous carbonate rocks: new data for the Monzoni and Predazzo aureoles,northern Italy,and a global review

Periclase formed in siliceous dolomitic marbles during contact metamorphism in the Monzoni and Predazzo aureoles, the Dolomites, northern Italy, by infiltration of the carbonate rocks by chemically reactive, H₂O-rich fluids at 500 bar and 565-710 °C. The spatial distribution of periclase and oxygen isotope compositions is consistent with reactive fluid flow that was primarily vertical and upward in both aureoles with time-integrated flux ~5,000 and ~300 mol fluid/cm² rock in the Monzoni and Predazzo aureoles, respectively. The new results for Monzoni and Predazzo are considered along with published studies of 13 other aureoles to draw general conclusions about the direction, amount, and controls on the geometry of reactive fluid flow during contact metamorphism of siliceous carbonate rocks. Flow in 12 aureoles was primarily vertically upward with and without a horizontal component directed away from the pluton. Fluid flow in two of the other three was primarily horizontal, directed from the pluton into the aureole. The direction of flow in the remaining aureole is uncertain. Earlier suggestions that fluid flow is often horizontal, directed toward the pluton, are likely explained by an erroneous assumption that widespread coexisting mineral reactants and products represent arrested prograde decarbonation reactions. With the exception of three samples from one aureole, time-integrated fluid flux was in the range 10²-10⁴ mol/cm². Both the amount and direction of fluid flow are consistent with hydrodynamic models of contact metamorphism. The orientation of bedding and lithologic contacts appears to be the principal control over whether fluid flow was either primarily vertical or horizontal. Other pre-metamorphic structures, including dikes, faults, fold hinges, and fracture zones, served to channel fluid flow as well.