Distribution Of Diatoms In The Jining Section Of The Beijing-Hangzhou Grand Canal And The Surrounding Waters Of Jining In Autumn And Winter

Objective: The cause and time of death and the place of falling into the water have always been important issues for forensic workers when dealing with corpses in the water.With the continuous updating of diatom inspection methods,the cause of death of corpses in water has been basically solved,but the time of death and the place of falling into water have become another difficult problem in forensic investigations.In this experiment,the types and quantities of diatoms in the Jining section of the Beijing-Hangzhou Grand Canal and the surrounding waters of Jining in autumn and winter are analyzed to find the differences in the distribution of diatoms in different seasons,different rivers,and different sites of the same river,thereby,to establish a diatom database.Methods: 15 sites were selected from three rivers,respectively,the Jining section of the main channel of Beijing-Hangzhou Grand Canal(River A,6 sites),the section of the Beijing-Hangzhou Grand Canal in Jining urban area(River B,6 sites),and the Jining section of Guangfu River(River C,3 sites).Water samples were collected in the autumn and winter of the sites,and qualitative and quantitative analysis of diatoms at each site were performed using graphite digestion-vacuum filtration-scanning electron microscopy.Five biological indices were applied: Species Dominance Index(Y),Shannon-Wiener Diversity Index(H '),Margalef Richness Index(dma),Pielou Uniformity Index(J),and Simpson Encounter Index(D).Analysis was performed on the species and quantity of diatoms at each site.At the same time,Wilcoxon matched-pairs signed ranks sum test,Poisson test or Wilcoxon test was used for statistical analysis of the data obtained.Results: The rivers in different seasons have roughly the same biological index,but the number of each species is different.The diatoms in the water samples in autumn and winter have significant differences in Shannon-Wiener diversity index(H '),Pielou evenness index(J),Simpson encounter index(D)and the number of diatom detected(P0.05),but no significant difference was found on the Margalef richness index(dma)(P>0.05).There was a significant difference in the amount of diatoms detected in River A and B(P <0.05),but no significant difference was found in the diversity index and evenness index.River C had statistically significant differences in diversity index,evenness index,and number of diatoms detected(P <0.05)compared with River A and B,and a unique and rare Navicula was found in River C.The types and number of dominant species in different sites in the same river are not exactly the same,and the dominance rate of thesame dominant species is completely different.Therefore,there is a difference in the species dominance among the sites.Conclusion: There is a statistical significance of the biological index difference of diatom numbers at each site in autumn and winter.Different rivers have substantial differences in the number and species of diatoms,and different rivers can be distinguished by specific rare algae as well as by statistical differences in biological indices.Significance: To establish a diatom database of Jining section of the BeijingHangzhou Grand Canal by studying the role of different biological indices in forensic diatom inspection.It provides certain reference on the time and place of falling into water for forensic analysis of drowning cases.