Planetary Sciences: In addition to experimental sciences, Liang makes chemical characterizations for the atmospheres of astronomical bodies with astrobiology/climate interest/relevance, including sulfur chemistry on Venus, organic compounds and particulates synthesis on Titan and extra-solar planets, using models developed, customized, and integrated by the group. Chemical processes considered are not limited to gas phase chemistry but also ice phase heterogeneous chemistry occurring predominately in the outer solar system bodies. Global gross primary production quantification: The abundance variations of near surface atmospheric CO2 isotopologues (primarily 16O12C16O, 16O13C16O, 17O12C16O, and 18O12C16O) represent an integrated signal from anthropogenic/biogeochemical processes, including fossil fuel burning, biospheric photosynthesis and respiration, hydrospheric isotope exchange with water, and stratospheric photochemistry. Oxygen isotopes, in particular, are affected by the carbon and water cycles. Being a unique tracer that directly probes governing processes in CO2 biogeochemical cycles, D17O (= ln(1+d17O) - 0.516´ln(1+d18O)) provides an alternative constraint on the strengths of the associated cycles involving CO2. Applying the method, Liang’s group has successfully derived the global primary production from a completely different approach, with improvements for our knowledge of the global carbon cycle.
Geochemistry and paleo-climate: In the past years, Liang’s research group has developed two advanced techniques with precision for isotope analyses (clumped and triple oxygen isotopes), along with conventional analyses (such as dD and d18O), providing useful tools for refining our knowledge of processes in natural systems such as carbon/water cycles. With increasing collaboration with the colleagues at the Institute and facilities available, water-rock interaction can be studied from perspectives (such as Mg isotope constraint for igneous rocks which can be complemented by triple oxygen isotope analysis). It is known that interaction between the Earth’s hydrosphere and the lithosphere plays a key role in shaping the global climate, chemistry and eventually making the Earth habitable. The history of this interaction is reflected in the oxygen isotope budget of the ocean water, in particular the triple oxygen isotope composition. The oxygen isotopic composition of the ocean water is primarily buffered by the relative contribution from the high temperature hydrothermal alteration at mid-oceanic ridge and low temperature alteration at the off-axis seafloor alteration and the continental weathering. The alteration history of the oceanic crust is recorded in fragments of preserved oceanic crust called ophiolite. Therefore, a detailed study of the rocks of relevance provides opportunity to assess the isotopic budget of Earth’s hydrosphere in deep time.
Modern hydrological cycles monitoring: Precipitation is the major source of drinking water in Taiwan (a negative side of precipitation is flood), and is a single most important variable that current weather forecast and climate models cannot predict well. One main reason is due primarily to our poor knowledge of environmental conditions at which where microphysics (vapor to condensed phase of water) occurs. Thanks to the advances of laser spectroscopy, routine, real-time, and in situ water vapor isotope analysis has become possible. Along with the isotope information in precipitation, physical conditions at which microphysics occurs can be best described.
Pollution chemistry and environmental epidemiology: It is known that atmospheric photo-oxidation chemistry largely affects the production of secondary aerosols in the atmosphere, the major component of particulate matters (such as PM2.5). It is well-recognized that the production of these secondary aerosols is largely affected by ozone-mediated oxidation. Ozone has a distinctive isotope composition (from its formation mechanism) from other major oxygen atom carriers such as atmospheric oxygen (O2) and water (H2O). In ozone-mediated oxidation reactions, the unique isotope composition in ozone can be transferred to the products of oxygenation involving ozone. Particulate nitrate is one species that Liang’s group has studied. This application opens up a new direction of tackling fundamental oxidation chemistry in Taiwan. The results and conclusions arrived by a series of and the subsequent studies of PMs suggest that the commonly known oxidation pathways occurred in western countries do not apply here in Asian countries. In addition, it is known that inhaling anthropogenically-produced particulates, such as the so-called PM2.5 (particle sizes less than 2.5 mm), causes adverse effects on human cardiopulmonary and metabolic systems. An evaluation made by International Agency for Research on Cancer concludes that outdoor PM pollution is carcinogenic to humans (Group 1). While the epidemiological evidence has been substantial, the exposure data are often based on estimation of the mass concentrations of PMs obtained from fixed monitoring stations, but uncertainty exists regarding the actual exposure level, risk chemicals and the likely co-exposure of multiple pollutants. Furthermore, as the components of pollution are expected to vary depending on the sources and the climatic factors, a clear dose-response curve is often difficult to achieve. By analyzing the reactivity of the PMs, the mechanistic connections can be better identified.
