Journal of Forensic Science and Medicine

REVIEW ARTICLE
Year
: 2016  |  Volume : 2  |  Issue : 2  |  Page : 107--110

A Future Perspective in Forensic Medicine in China: Diatomological Mapping of Water Bodies


Luo Zhuo, Shu Lin, Peng Song 
 Division of Forensic Science, Fujian Provincial Public Security Department, Fujian Provincial Key Laboratory of Forensic Science and Technology,Fuzhou, 350003, China

Correspondence Address:
Luo Zhuo
Department of Fujian Provincial Public Security, Forensic Science Division, 12 Hualin Road, Fuzhou 350003
China

Abstract

Diatom test (forensic diatomology) is commonly considered as the “gold standard” in the diagnosis of drowning in forensic practices. The diatomology contributes significantly not only in determining the mode of death but also in determining the site of drowning because of various distribution characterizations of diatoms in different water bodies or different seasons. Hence, it is believed that diatomological mapping will be interest to forensic pathologists in the future development. Here, we reviewed the all the studies on the distribution characterizations of diatoms in different water bodies in China recently. The present paper summarized the current situation and the limitations of the previous studies. Moreover, we suggested that it was necessary to establish a systematized and standardized diatomological mapping program nationwide. Our study also encourages diatomological mapping for forensic characterization of water bodies for a prolonged time.



How to cite this article:
Zhuo L, Lin S, Song P. A Future Perspective in Forensic Medicine in China: Diatomological Mapping of Water Bodies.J Forensic Sci Med 2016;2:107-110


How to cite this URL:
Zhuo L, Lin S, Song P. A Future Perspective in Forensic Medicine in China: Diatomological Mapping of Water Bodies. J Forensic Sci Med [serial online] 2016 [cited 2020 Nov 30 ];2:107-110
Available from: https://www.jfsmonline.com/text.asp?2016/2/2/107/177407


Full Text



 Introduction



Diatoms are a group of unicellular algae that have very useful applications in forensic investigations of drowning cases especially in establishing cause and mode of death, i.e., antemortem and postmortem drowning. The presence of diatoms in a dead body is a clear indicator of death by drowning.

The task in drowning cases remains focused mainly on establishing the cause of death and the localization of the precise site of drowning. Sometimes, drowning cases is encountered with the unclear situation on the exact site of drowning especially when drowned body is replaced to land or drowned body has dragged to a greater distance from the exact site of drowning with a swift flow of water. Another situation can also be thought when significant numbers of diatom are found in the drowned body, but they do not match with types of diatoms from reference liquid medium. In these situations, locating the site of drowning becomes the prime job of a medical examiner. Therefore, use of a diatomological database of water bodies was recommended of immense help for correlation purpose in these types of cases.

 Literature Review



To identify studies on the diatomological mapping of water bodies in China, we performed a (China Knowledge Resource Integrated Database which contains China Academic Journals Full-text Database, China Doctoral Dissertations Full-text Database, China Masters' Theses Full-text Database, China Proceedings of Conference Full-text Database and International Proceedings of Conference Full-text Database) search from the year of 2000 onward by using the keywords of “diatom,” “distribution characteristics” and “forensic medicine.” A total of 11 studies we found were in the background of the Forensic investigation. The list of references is followed [Table 1].{Table 1}

 Results



Restriction of study areas

In the total of 11 studies, 4 was launched in Shenyang, 2 in Beijing, 2 in Shanghai, 1 in Wuhan, 1 in Dongguan, and 1in Guangzhou [Figure 1]. Majority of the studies were conducted in particular administrative areas, such as counties, cities, and municipalities. Hence, the water bodies were artificially divided by administrative districts. The result showed only 1 study was built on complete water areas, in which the diatomological mapping covered two reservoirs.{Figure 1}

Variation of the study duration

According to the previous studies, we found that the average study duration was <1 year. Among them, 2 studies of 2 months, 1 of 3 months, 3 of 4 months, 1 of 6 months, and 1 of 12 months. The growth of diatom in the water bodies could be affected by various factors, including illumination, temperature, flow velocity, salinity, pH value, and so on.

Variation of water sampling

In 9 studies, diatom distribution patterns were analyzed by investigating the water bodies by using various methods: Positional water sampling (fixed space along the bank) was applied in more than 50% (6 out of 11) of the studies, and random water sampling was used in 3 studies. In addition, the depth of water sampling varied as well. 54.4% (6 out of 11 studies) of the previous studies were found that water samples were collected from 1 m underwater. Du Yu, etc.[6],[7],[9],[10] performed a series studies on the diatomological mapping in Shenyang. In their studies, the test sample in each sampling spot was mixed with the water sample collected from the surface and 20 cm underwater of the water body.

Highly diversified diatom in different water bodies and different seasons

Different distribution patterns of diatoms were found in different water bodies and different seasons even in the same location. Morphological analysis of diatoms has revealed significant variation in their shape and size. The previous studies showed the average of 22.1 species of diatoms was found in different water bodies. The dominating diatoms that have been observed in almost every water body were Centriae and Pennatae [Figure 2]. The diagram showed the average number of diatom species were found in different administrative areas from the previous data [Figure 3].{Figure 2}{Figure 3}

 Discussion



Whether the diatom test is applicable for drowning deaths is still controversial. From the forensic pathology point of view, drowning is still a difficult autopsy diagnosis, and it is usually a diagnosis of exclusion.[12] Diatoms have been found in the tissues of people who died of causes other than drowning due to their widespread distribution throughout the environment, in the soil, water supplies, food and in the air, and may be absent in the case of drowning.[13],[14] Therefore, the number and the species of diatoms found in the tissues of cadaver are useful for diagnosis of drowning death when compared with the diatoms patterns in the water bodies around.

The current situation of the diatomological mapping in China

It is obvious that previous studies of diatomological mapping were concentrated to the north of Yangtze river but fewer in the southern part of China. Nevertheless, there are plenty of water areas that have not been investigated yet, including Yangtze river basin, Zhujiang river basin, and Min river basin, etc. The diatoms in the southern area of China have rich biological populations and diverse distribution patterns, which were attributed to the dense network of rivers and lakes. For instance, from the previous data, the species of diatoms found from the water samples in Dongguan and Guangzhou were 70 and 50, respectively. Therefore, from the overall perspective, the diatomological mapping is now still at its preliminary stage in China, and studies of many unexplored water areas need to be urgently investigated.

A future prospect of diatomological mapping in forensic medicine

It has been demonstrated that studies on diatoms distribution characterizations in different water bodies and different seasons could greatly help the forensic pathologists to divert the cause of death and estimate the drowning site. Lai et al.[2] applied similarity analysis to compare the diatoms in water samples and the drowned bodies. He confirmed that similarity factor, diversity factor, and clustering analysis could be used in drowning site estimation. Even though many studies has worked on the diatomological mapping in some regions in China, there are still plenty of blank water areas. Moreover, diatoms distribution characterization investigation, so called diatomological mapping were currently accepted by more and more forensic pathologists worldwide. Ludes et al.[15] set up a regional diatom monitoring program. They compare 20 corpses who died from drowning with known drowning site and 20 corpses with unknown drowning sites. And they concluded that the diatomological mapping may be an interesting method to guide the investigations for determining the drowning site. Kakizaki et al.[16] collected different water samples from various sites around the estuaries of 2 rivers at high and low tides and observed the morphologic characterizations of diatoms. Their results showed that diatomaceous assemblages change even at the same site between low and high tides, which contributed to deducting drowning sites.

As a new interest in the field of forensic medicine, diatomological mapping is suggested to be built up as a nationwide systematic research program. Learning from the previous studies, the investigations of diatom distribution characterizations in different water bodies should be standardized. The following criterion should be carefully considered. (1) The cross-district diatomological mapping should be encouraged and spread. To archive much more systematic and complete information of the diatoms distribution characterizations in rivers, lakes, and other water bodies, the diatomological mapping program should cover the entire water area. A diatomological mapping database of, for example, the mainstream or a branch could be established. Water bodies often be found flow through several administrative areas, so the factors of regional industrialization, ecological environment, pollution, humanity, and economy may contribute to the regional differences of diatoms distribution characterizations. (2) Establishing standardized methods. The standardized methods of water sampling include how to determine the sampling points and how deep to collect the water. The standardized method may differ in different types of water bodies to minimize the artificial error. (3) Dynamic and continuous observation. Since the growth of diatoms is bound to surrounding climatic conditions, nutrient factors and some chemical properties of water, therefore, diatom community can vary in the different water body and even in the same water body in different seasons. Especially in the north area, the diatom community can vary in a long period in the same water body owing to the influence of river freeze up and thawing periods. Hence, the diatomological mapping program should contain four seasons at least. As the development of the water area and the change of the climate condition in a long time, it is also important to observe the diatoms distribution patterns dynamically and continuously.

 Conclusion



Diatomological mapping for forensic characterization in water body will be an immense help in enhancing the current knowledge of forensic diatomology and provide a useful lead to the forensic pathologists in solving the drowning cases.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.

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