Abstract

In environmental forensic investigations, soil is often considered as the evidence associated with a crime scene in court. A major challenge is minimizing the uncertainty in linking sets of matched soil to a suspected offender. This article examined the potential methods of analyzing soil bacterial communities via high throughput sequencing, which could generate information of great importance to environmental forensic investigations. Here, we simulated local, regional, and large-scale scenarios, in addition to unknown samples, to investigate the potential of using soil as physical evidence in environmental forensics. At the broad-scale, using heatmap cluster and principal coordinate analyses, we observed that the microbial communities in samples were significantly different across different spatial distances based on Bray-Curtis dissimilarity distances. In soil samples obtained within 20 m of each other, the microbial communities revealed the detailed information based on the numbers of specific operational taxonomic units (OTUs) and biomarker species. In the criminal contexts, soils can be obtained and used to decode the origin information. To trace the soil samples to their origins, we analyzed the dissimilarity distances and matched sources of suspected soil samples to simulate crime investigation activities. In our study, source tracker was used to locate the sources of samples obtained from of a shoe or a tool according to soil microbial communities, and the method could be an effective auxiliary approach in forensic soil source tracking based on microbial data. The results demonstrated that high-throughput sequencing combined with the source tracker approach could make soil a powerful source of evidence to facilitate environmental forensic investigations.

摘要

在环境法证调查中，土壤通常被视为与法庭犯罪现场有关的证据。一个主要的挑战是将匹配的土壤与犯罪嫌疑人联系起来的不确定性最小化。本文研究了通过高通量测序分析土壤细菌群落的潜在方法，这些方法可能会产生对环境法证研究非常重要的信息。在这里，除了未知样本外，我们还模拟了局部，区域和大规模场景，以调查在环境取证中将土壤用作物理证据的潜力。在大范围内，使用热图聚类和主坐标分析，我们观察到，基于Bray-Curtis不相似距离，样品在不同空间距离上的微生物群落差异显着。在彼此之间20 m之内获得的土壤样品中，微生物群落根据特定的操作分类单位（OTU）和生物标记物种类的数量揭示了详细的信息。在犯罪背景下，可以获取土壤并将其用于解码来源信息。为了追踪土壤样本的起源，我们分析了相异的距离并匹配了可疑土壤样本的来源，以模拟犯罪调查活动。在我们的研究中，根据土壤微生物群落，使用了源跟踪器来定位从鞋子或工具中获取的样品的来源，该方法可以作为基于微生物数据的法医土源追踪的有效辅助方法。结果表明，高通量测序与源跟踪器方法相结合可以使土壤成为促进环境法证研究的有力证据。