Pin Chang

Bio: Pin Chang is an academic researcher from University of California, Berkeley. The author has contributed to research in topics: Diffusion (business) & Grain boundary diffusion coefficient. The author has an hindex of 2, co-authored 2 publications receiving 3916 citations.

Correlation of diffusion coefficients in dilute solutions

Abstract: Equation i 1) is strictly applicable in ideal dilute solutions in which convective transport due to volume changes on mixing is negligible, and in which other possible modes of mass transfer are not operative. This paper represents an attempito generalize the relation of P to conveniently available properties of dilute solutions so as to permit estimation of diffusion coefficients for engineering purposes.

Relationship between wind speed and gas exchange over the ocean

Abstract: Relationships between wind speed and gas transfer, combined with knowledge of the partial pressure difference of CO2 across the air-sea interface are frequently used to determine the CO2 flux between the ocean and the atmosphere. Little attention has been paid to the influence of variability in wind speed on the calculated gas transfer velocities and the possibility of chemical enhancement of CO2 exchange at low wind speeds over the ocean. The effect of these parameters is illustrated using a quadratic dependence of gas exchange on wind speed which is fit through gas transfer velocities over the ocean determined by the natural-14C disequilibrium and the bomb-14C inventory methods. Some of the variability between different data sets can be accounted for by the suggested mechanisms, but much of the variation appears due to other causes. Possible causes for the large difference between two frequently used relationships between gas transfer and wind speed are discussed. To determine fluxes of gases other than CO2 across the air-water interface, the relevant expressions for gas transfer, and the temperature and salinity dependence of the Schmidt number and solubility of several gases of environmental interest are included in an appendix.

Superoxide Ion: Generation and Chemical Implications

Abstract: Superoxide ion (O2•–) is of great significance as a radical species implicated in diverse chemical and biological systems. However, the chemistry knowledge of O2•– is rather scarce. In addition, numerous studies on O2•– were conducted within the latter half of the 20th century. Therefore, the current advancement in technology and instrumentation will certainly provide better insights into mechanisms and products of O2•– reactions and thus will result in new findings. This review emphasizes the state-of-the-art research on O2•– so as to enable researchers to venture into future research. It comprises the main characteristics of O2•– followed by generation methods. The reaction types of O2•– are reviewed, and its potential applications including the destruction of hazardous chemicals, synthesis of organic compounds, and many other applications are highlighted. The O2•– environmental chemistry is also discussed. The detection methods of O2•– are categorized and elaborated. Special attention is given to the f...

Gas exchange rates between air and sea

Abstract: Gas exchange rate studies carried out in the laboratory suggest that the stagnant film model is adequate to relate the transfer coefficients of most gases between the atmosphere and sea to an accuracy of ±15%. Estimates of the average film thickness prevailing for the world ocean based on the distribution of natural radiocarbon, bomb-produced radiocarbon, and radon are in good agreement. Radon data from the BOMEX area and from station PAPA lend support to Kanwisher's suggestion that gas exchange rates should vary in proportion to the square of the wind velocity. These observations permit a number of generalizations regarding the potential of the ocean as a source and sink for trace gases to be made. They also permit the more complicated situation for carbon dioxide to be assessed. DOI: 10.1111/j.2153-3490.1974.tb01948.x

Relationship between wind speed and gas exchange over the ocean revisited

Abstract: The relationship between gas exchange and wind speed is used extensively for estimating bulk fluxes of atmospheric gases across the air-sea interface. Here, I provide an update on the frequently used method of Wanninkhof (1992). The update of the methodology reflects advances that have occurred over the past two decades in quantifying the input parameters. The general principle of obtaining a relationship constrained by the globally integrated bomb-14CO2 flux into the ocean remains unchanged. The improved relationship is created using revised global ocean 14C inventories and improved wind speed products. Empirical relationships of the Schmidt number, which are necessary to determine the fluxes, are extended to 40°C to facilitate their use in the models. The focus is on the gas exchange of carbon dioxide, but the suggested functionality can be extended to other gases at intermediate winds (≈4−15 m s−1). The updated relationship, expressed as k = 0.251 (Sc/660)−0.5 where k is the gas transfer velocity, is the average squared wind speed, and Sc is the Schmidt number, has a 20% uncertainty. The relationship is in close agreement with recent parameterizations based on results from gas exchange process studies over the ocean.