3 year PhD scholarship available CRC for Water Quality and Treatment, Curtin Water Quality Research Centre and Stable Isotope and Biogeochemistry Research Group, Centre for Applied Organic Geochemistry, Department of Applied Chemistry, Curtin University of Technology, Perth, Western Australia. The use of stable isotopes for the characterisation of NOM and investigation of the different organic precursors of aquatic systems. Background: There are many different biological (e.g., algae, bacteria and macrophytes) and anthropogenic (storm water, industrial waste) sources of aquatic organics and the exact identity of the main precursors of dissolved organic carbon (DOC) often remains ambiguous. Different organic species can also impact water system to different degrees at different times. Identification of the major organic inputs to source water is crucial for catchment and reservoir strategies aimed at minimising organic loads. Such knowledge may also optimise holistic treatment protocols with respect to efficient DOC removal. Stable isotope analysis is a useful method for distinguishing the different organic inputs of natural environments. The stable isotopes of carbon, nitrogen, sulfur, oxygen, and hydrogen are commonly used in ecological and environmental research and are measured by isotope ratio-mass spectrometry (Grice, 2001, and references therein). It is quantitative and non-intrusive, without the environmental hazards of radioisotope investigations. It can provide valuable data on chemical, biological, and physical transformations of organic compounds in the environment (Grice et al., 2001). Several examples of environmental applications of stable isotopic analysis which should also be applicable to the analysis of NOM include: 1. distinguish the contributions of different organic precursors (Schouten et al., 1996; Klein Breteler et al., 2002); 2. monitor temporal and spatial variations of bioproductivity (Kuypers, 2001; Hinrichs et al., 2003) - the seasonal and spatial molecular variance of NOM in surface waters was recently monitored to assess source, transport and fate of humic and non-humic DOM (Lu et al., 2003); 3. Understand degradation and humification processes (Lu et al., 2003); 4. to chemically monitor the effect of natural bioremediation or other treatment processes on molecular composition (Steinbach et al., 2002). Traditionally conducted on bulk samples, stable isotopic analysis of individual compounds is now also possible following the advent of GCirMS (Hayes, 1983). Compound specific isotope analysis (CSIA) of individual compounds can facilitate the high resolution distinction of different organic sources. Isotopic data can compliment the measurement of molecular distributions with respect to biomarker identification. Just like the occurrence of certain biomarkers, the stable isotopic value of certain products can be diagnostic of particular organic precursors. Many naturally occurring organic compounds can derive from one or more precursors and the different source possibilities may be distinguished by their stable isotopic characteristics. Stable isotopic data may also allow the seasonal productivity of DOC precursors to be monitored, as well as provide information about the aquifer residence time of particular organic compounds (Lu et al., 2003). The load of organic precursors can vary considerably over time. Bioproductivity, for example, can vary with environmental or seasonal changes, but again little is known about the triggers or mechanism of this phenomena. The continuum of organic species may simply change with the changing rate of some source inputs, whilst specific compounds may be linked to a particular source, season or other environmental factor. The catchment environment can also impact on the composition of DOM as organic compounds will degrade at different rates. Stable isotopic analysis offers some potential for monitoring the occurrence, cause and effect of these dynamics. Description of Project: This PhD project aims to develop and test the utility of stable isotopic analysis for characterising and establishing the main precursors of DOC. Stable isotopic data of NOM will be obtained on both a whole sample and a compound specific basis to investigate the utility of stable isotope analysis for studying the source input, temporal and spatial dynamics (e.g., bioproductivity), transportation and fate of organic material in source water systems. A range of NOM samples will be studied since the chemical and physical nature of NOM is dependent on the source materials and surrounding environmental conditions, hence NOM from different locations can vary considerably in structure and behaviour. NOM fractions will be separately studied to establish the relationship between the structural moieties of NOM and specific organic precursors. A correlation of the source inputs of organics in the source waters with the subsequent occurrence of certain DBPs following treatment may also help identify which precursors are most significant with respect to DBP formation. Accurate CSIA measurements require baseline GC resolution since values are calculated from the ratio of the m/z 45 (13CO2) and m/z 44 (12CO2) peaks. That means that complex organics such as NOM often need to be separated into simplistic fractions prior to analysis. This can be achieved by chemical degradation (e.g. CuO) or off-line pyrolysis followed by column chromatography to produce less complex fractions on the basis of solubility in solvents of different polarity. New chemical and enzymatic degradation techniques, which selectively target specific structural bonds (e.g., C-N, C-O, C-S bonds), will be developed to produce relatively clean fractions suitable for compound specific isotope analysis (CSIA). The utility of stable isotope analysis for following seasonal and geographical variations of organic species will be examined. The organic composition of source waters is likely influenced by a number of variables including the catchment environment, climate, seasons, etc. NOM will be periodically collected and isolated from selected source waters to cover seasonal and climatic variations. Skills/Interests Required: First class Honours or equivalent science degree- preferably in Chemistry. Interest in analytical organic chemistry; laboratory skills in trace analysis; familiarity with and skills in pyrolysis, wet chemical methods, GC, or GCMS instrumentation; awareness of stable isotopic concepts. Overseas applicants are also welcome to apply. Contact Details for Further Information: Forward CV and 2 referees to: Assoc. Prof Kliti Grice, Stable Isotope and Biogeochemistry group, Centre for Applied Organic Geochemistry, Curtin University of Technology, Perth, WA, Australia Ph: +61 (08) 9266 2474; 0401 103 353 Fax: +61 (08) 9266 2300 www.caog.chemistry.curtin.edu.au <http://www.caog.chemistry.curtin.edu.au/> www.chemistry.curtin.edu.au <http://www.chemistry.curtin.edu.au/> www.waterquality.crc.org.au <http://www.waterquality.crc.org.au> Regards, Kliti Grice Dr Kliti Grice Associate Professor of Organic and Isotope Geochemistry ARC (QEII) Fellow Stable Isotope and Biogeochemistry Group Leader Centre for Applied Organic Geochemistry Department of Applied Chemistry Curtin University of Technology Perth 6845 WA Australia tel +61 8 9266 2474 fax + 61 8 9266 2300