Types of diatoms in China’s three major rivers and the possible application for an automatic forensic diatom test

The diatom test is the most reliable approach that provides scientific support for diagnosis of drowning. However, there are limitations, which, made forensic scientists stop using the test, such as the fact that it is time-consuming and lack of domain knowledge of the diatom identification. This study aims to find different types of diatoms that are commonly present in water bodies in China for a possible application of an automatic forensic diatom test. In total, 119 different water samples were obtained from different locations of the Yellow River, the Yangtze River and the Pearl River (China) and were analysed. About 50 ml of water of each sampling site was digested and then observed by a scanning electron microscopy. The diatom genera found in samples were recorded. Twenty-four diatom genera were found in all samples. Among them, Navicula, Nitzschia, Cyclotella, Synedra and Gomphonema were commonly presented (>70%) across the broad geographic regions. Navicula, Nitzschia, Cyclotella, Synedra and Gomphonema would be the main diatoms used in designing an automatic diatom identification system for forensic diatom test.