Discussion On The Problem Of Diatom Test In Drowning Identification

Background and ObjectiveWhen conducting forensic identification of water bodies,to determine the cause of death is the primary problem.The general problem to solve is drowning during his lifetime,or postmortem into the water.Drowning(drowning)is a kind of mechanical asphyxia death,it is due to the liquid enters and blocks the airway and alveolar space,hindering gas exchange leading to hypoxia,hypercapnia and asphyxia death.In the actual case,the majority of the bodies found in water are drowning by accidents,but drowning is also one of the common means of suicide,a minority belong to homicide;and even there are bodies moved into the water to disguise the drowning scene.Therefore,the bodies in water may be related to major criminal cases,forensic identification must be carried out.Fresh corpses of drowning can show the common signs of asphyxia death,and also have some unique features of drowning such as snout fungoides bubble,aqueous emphysema etc.But in the actual investigation of forensic medicine,most of the water bodies have a high degree of corruption,the drowning phenomenon of the corpses has ceased to exist,at this time,the laboratory test on diatom is particularly important.Diatom,also known as diatoms,mostly are unicellular phytoplankton in waters to survive,a small number of diatoms are groups or filaments.Many forensic workers confirmed that diatoms can be with the water into the lungs in the drowned corpses,and through the circulation to the internal organs of the body.Therefore,we can determine whether it is the lifetime drowning through the examination of diatoms in lung and other organs.But some scholars found that diatoms can not be detected in drowned bodies.Conversely,diatoms can also be inhaled through the air and found in visceral organs of some non drowned bodies who have a long life in the diatom rich dust.And diatom residue can still be positive in internal organs for years.Therefore,some scholars take a skeptical view of the significance of the diatom test in diagnosis of lifetime drowning.According to records,when the bones of the corpse in the water are found,it can be judged to be drowning if there are the same diatom species both in the bone marrow and the water samples.But the bones of dead bodies in the water have been soaked in the water for a long time.Then,can the diatoms in the water enter the marrow of the skeleton bones directly? The above academic views have not been confirmed by systematic experiments.Therefore,it is of great practical significance to further study the diatom test.We have a systematic experiment to explore whether there are diatoms in the air,if any,how the number is and what kind are they and can they enter into the living lungs? Whether it will affect the diatom test in drowning identification? We soak different animal long bones in the river for a long time to see whether the diatoms in the water can enter into the bone marrow.Our experiment may provide a theoretical direction for the forensic identification of drowning,and it is of great significance especially for the identification of drowning in water of less diatoms(such as the drowning happened in wells and baths).Methods1 Collect the rain and snow in different seasons in Henan area during the period from January 2016 to March 2017.Rainwater collection: in different regions of Henan,select open area,the clean containers were fixed on the height of about 1.5 meters from the ground(to prevent ground soil from splashing into the containers),36 copies different seasons rain were collected.Snow collection: after heavy snow in different regions of Henan,collect clean snow from different locations(to prevent contamination of soil),a total of 20 copies snow water.Collect 10 copies dust above indoor furniture and outdoor cars in different locations in Henan Zhengzhou area(group 1),10 copies dust above indoor furniture and outdoor cars in different counties in Henan other regions(except Zhengzhou area)(group 2),10 copies dust above indoor furniture and outdoor cars in different locations in Hainan area(group 3).The collected dust was respectively dissolved in distilled water,stirred,oscillated,centrifuged,and fully mixed,and the dust water was made up of 30 parts.At the same time,collect 20 copies non drowning goat lungs,20 copies non drowning chicken lung and 120 non drowning human lungs of Henan area obtained from Zhengzhou University forensic Center.2 In this experiment,15 goat legs and 15 chicken legs were used(The goats and chicken were non drowning).They were randomly divided into control group(5 legs,non drowning without immersion group),non drowning with immersion group(10 legs).Take appropriate Jinshuihe River water in the bucket in the laboratory.The water depth in the bucket was 0.5 meters and the number of diatoms in the water was(71.73±4.01)one/10 mL,the main species of which were pennatae diatoms,and a few of them were the central diatoms.Soak the immersion group complete leg bones of different animals in the water,change the water regularly,and the soaking time was about 3 months.3 Eath group was treated with digesting organic matter with nitric acid to detect diatoms in lung tissue and bone marrow,and the water samples were directly centrifuged for several times,take sediment for the microscopic examination.4 All the experimental data can be expressed by mean ±standard deviation(? ±s).After using SPSS 19.0 statistical software carrying on normal test and homogeneity of variance test for data,single factor variance analysis(ANOVA)and LSD-t test were used to compare the mean.Use nonparametric for nonnormal distribution and variance inequality,test level ?= 0.05.Results1 Diatoms were not detected in all the 36 portions of the rainwater.Diatoms were detected in all the 20 portions of the snow water.Dozens of diatoms can be found in each slide.The amount of the diatoms was 82~126 one/100mL?g snow water,the main species of which were pennataes,among which Pinnularia and Nitzschia is most common.Diatoms were detected in all the 30 portions of the dust water.A number of diatoms can be found in each slide.The amount of the diatoms was 4~9 one/?g dust,the main species of which were pennataes,among which Pinnularia and Nitzschia is most common.Diatoms were detected in only one of the 120 cases human lungs.The amount of the diatoms was 2 /20 g tissues,of which one was pennatae diatoms and the other was central diatom.Individual diatoms were detected of the 20 cases goat lungs,the amount fluctuated between 0~2/20 g tissues,of which 1 /20 g tissues were detected in 4 cases,2 /20 g tissues were detected in 3 cases,no one was detected in the remaining 13 cases.Individual diatoms were detected of the 20 cases chicken lungs,the amount fluctuated between 0~2 /20 g tissues,of which 1 /20 g tissues were detected in 6 cases,2 /20 g tissues were detected in 2 cases,no one was detected in the remaining 12 cases.2 Diatom test results of bone marrow: Diatoms were detected in part of the 10 goat legs soaked in the river water.The amount fluctuated between 0 ~3.6/20 g bone marrow tissues,of which diatoms were detected in 6 cases and no diatom was detected in the remaining 4 cases.Diatoms were detected in part of the 10 chicken legs soaked in the river water.The amount fluctuated between 0 ~4.1/20 g bone tissues,of which diatoms were detected in 7 cases and no diatom was detected in the remaining 3 cases.Conclusions1 Diatoms exist in the air,and the majority are pennatae diatoms.But its content is few.The diatoms in the air are difficult to enter into the living lungs.Inhalation of air does not have a significant impact on the results of diatom test.2 Diatoms in the air are difficult to enter into general circulation of the living body.Diatoms in the water can enter into the marrow of animal bones.Therefore,in practical cases,if the bones of the dead are found in the water,we can not easily make the judgment that it is drowning only by detecting the same species diatoms both in bone marrow and water samples.