Qualitative and quantitative analysis of diatoms in Water and Lungs by SEM and Distribution of diatoms in Pearl River's water bodies in Guangzhou urban area

Objectives To evaluate the relationship between distributions of diatoms in lungs of drowned victims and in drowning medium using scanning electron microscopy, and to establish the diatom distributions in Pearl River's water bodies in Guangzhou urban area. Methods 10 white rabbits were drowned in the experiment, and the lungs of the rabbits as well as the drowning medium were collected; Moreover, the water samples of the six water bodies of Pearl River in Guangzhou urban area were collected in September (representing high-temperature months ) and December (representing low-temperature months) of 2008 respectively; qualitative and quantitative analysis of diatom using scanning electron microscopy with automated scanning mode was performed for all the samples after being processed by microwave digestion and vacuum filtration. Results There was a concordance of the types and the relative abundance of each type of diatoms in the lungs compared to the site of drowning in 100% of the cases; and the diatom distributions in the six Pearl River's water bodies in Guangzhou urban area in September and December of 2008 were then developed. Conclusion The method using scanning electron microscopy with automated scanning mode for forensic diatom analysis has the advantage of labor saving and is capable of enhancing accuracy of qualitative and quantitative diatom analysis compared to the traditional method using light microscopy, thus is of prominent application value in forensic diagnosis of drowning. Diatom distributions in the lungs of drowned victims were closely related to drowning medium, therefore, the established diatom distributions of diatoms in Pearl River's water bodies in Guangzhou urban area will be very helpful in the diagnosis of drowning for bodies recovered in these water bodies.