Study On The Distribution Of Diatoms In The Yangtze River And Jialing River Of Chongqing Main Districts In The Four Seasons And The Establishment Of Its Database

Objective To provide theoretical basis for judging the drowning location and time,the diatom database were established by analyzing the distribution of diatom in the Yangtze River and Jialing River of the main districts of Chongqing in four seasons.Methods According to the principle of regional segmentation,water samples were collected from 10 sampling sites in the Yangtze River Basin(Yudong Yangtze River Bridge,Masangxi Yangtze River Bridge,Egongyan Yangtze River Bridge,Dongshuimen Bridge and Cuntan Yangtze River Bridge)and the Jialing River Basin(Beidong Bridge,Ma'anshi Bridge,Shuangbei Bridge,Shimen Bridge and Yuao Bridge)in March,June,September and December of 2018,respectively.The distribution data of diatoms in different sampling sites were obtained by MD-VF-SEM,and then the corresponding database was established.Results A total of 24 genera,9 families,2 classes,and 6 orders of diatom were detected in this study,including 1 order,1 family and 4 genera of Centricae,5 orders,8 families and 20 genera of Pennatae.The numbers of diatoms in the same sampling place were different in different months,and the numbers of diatoms in different sampling places were different in the same month.The composition of diatom genera in the same sampling area was different in different months.The composition of diatom genera in different sampling sites was different in the same month.The composition of diatom genera in adjacent sampling sites was similar in the same month,but the percentage was different.There were significant difference between the Yangtze River Basin and Jialing River Basin in the distribution of diatoms by orthogonal signal correction-partial least squares discriminant analysis(OSC-PLS-DA),and there was seasonal specificity in the distribution of diatoms.The database of diatom in the Yangtze River and Jialing River of the main districts of Chongqing in four seasons has been preliminarily established,which can be viewed,compared and added information.Conclusions The samples were widely collected from various sites in different seasons which were reasonable allocated.The method of MD-VF-SEM were suitable for the identification and classification of diatoms.Diatom test can be used to diagnose drowning in actual cases.Season-specific diatom can be used to infer the season of drowning.Area-specific diatom can be used to infer the area of drowning,namely the Yangtze River Basin or Jialing River Basin.Area-specific diatom and water flow velocity can be used to infer the location and time of drowning.The database of diatom in four seasons in the main districts of Chongqing in the Yangtze River and Jialing River has abundant data and complete functions,which provides a solid theoretical basis for judging the drowning location and time of the main districts of Chongqing in the two river basins,and provides a good research basis for further enriching and expanding the database in the future.