| In this dissertation, the rainwater samples collected from Guangzhou during September 2003 to August 2004 were fully and systematically investigated in terms of organic carbon content, the composition and distribution of organic matter such as aliphatics, aromatics and fatty acids. The following major conclusions can be drawn from this study:1. In the rainwater samples of Guangzhou, the contents of total organic carbon (TOC) and dissolved organic carbon varied from 0.72-16.10 mg/1 and 0.72-9.12 mg/1, respectively. The organic carbon content of the rain-particle samples (POC) was between 0.44-13.76mg/l, while the elemental carbon content of the rain-particle samples (PEC) varied between 0.02-3.02mg/l. The contents of TOC, DOC, POC and PEC are generally higher in the samples of wet-season than that in the dry season. Furthermore, the contents of TOC and DOC show certain level of negative relationship with the pH values of rainwater samples.2. The distribution pattern of n-alkanes in rainwater samples are mainly front-peak group dominated mode, rear-peak group dominated mode and flat peak group mode, while the front peak dominated double peak group mode and double peak group mode were mainly found in the rainwater particle samples. These distribution modes were closely associated with the seasonal change. The front-peak group dominated mode is mainly found in dry-season rainwater samples, while the flat-peak mode is mainly found in spring rainwater samples, and all this three modes were found in summer rainwater samples. Front-peak dominated double peak mode and double peak group mode were mainly found in the rain-particle samples, while the front-peaked dominated double peak group mode is mainly found in the rain-particle samples ofdry-season, and double peak group mode is mainly found in the rain-particle samples of wet-season. The CPI values are generally low in rainwater samples and rain-particle samples while these values are slightly higher in the dry-season's samples that that of wet-season's sample. The UCM mode in the chromatograms of Aliphatic hydrocarbons are characterized by unimodal (rainwater samples) and bimodal (rain-particle samples) for almost all samples. The distribution of n-alkanes, UCM, CPI values and their seasonal variation indicate that the vehicle emissions are the leading source of organic matter in the rainwater in Guangzhou. Moreover, the source of organic matter in the rain in wet-season may be more complex than in dry-season due to monsoon and active bacteria degradation.3. The composition and diagnostic ratios of the hopanes and steranes in rainwater samples and rain-particle samples are largely comparable with that of ambient atmospheric particles, and therefore reflected the organic contribution from the incomplete combustion of fossil fuel, that is the vehicle-related emissions.4. Phenanthrene and its alkyl derivatives are abundant in rainwater samples, as well as a certain amount of sulfur-containing and oxygen-containing PAHs. The values of the PAHs diagnostic ratios, such as MP/P, MPI, P/An, Fl/ (Fl+Py) and so on, reflect the vehicle-related emission is the major source of aromatic hydrocarbons in the rainwater. Furthermore, the ratios of BeP/(BeP+BaP) and BaA/(BaA+CT) suggest that some of aromatic hydrocarbons had experienced long-distance transportation. The seasonal variation of the PAHs composition and diagnostic ratios indicate that the organic matter could have been altered in some extent by the bacteria activity and photochemical reaction and electrochemical reaction in wet-season.5. The composition of n-alkanoic acids in the rainwater mainly indicates the contribution from the cooking emissions, while the ratios of C16:1/C16:0, C18:1/C18:0 and C18:2/C18:0 also suggest some input from the remote source via long-distance-transportation. The high plant sourced fatty acids were very limited.6. To sum up, the organic pollutants in the rainwater of Guangzhou were mainly sourced from the local vehicle emission and cooking emission, while the input from the remote sourced organics was small but significant, On the other hand, the composition and distribution of organic compounds in rainwater of Guangzhou show clearly seasonal variation. Furthermore, there are significant differences in the organic composition between the rainwater samples and rain particulates. In general, these results are important and useful for evaluating and controlling the pollution of the rain imposed to the eco-environment of the earth's surface and the air pollution, as well as for the study of material change between the earth surface and atmosphere.
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