法庭物证不同附着物上土壤的取样方法及源指示研究

土壤由于其广泛性和易于附着性等特点,在法庭物证溯源比对方面发挥着一定作用。为明确不同附着物取样方法对土壤性质的影响以及附着物上土壤的源指示作用,本研究选择在城市–城郊进行路线模拟,采集不同路段、不同环境条件下的原土,并对每个采样点进行纤维类(手套)、金属类(铁锹)和橡胶类(鞋底)附着土壤模拟。对不同附着物分别采用了干刷和水洗/滴洗两种方法进行取样,使用便携式X射线荧光光谱仪(XRF)测定土壤样品。结果表明,取样方法对纤维类和橡胶类附着土壤样品的元素含量无显著影响,但干刷法操作更方便快捷;金属类附着土壤的滴洗法优于干刷法。依据土壤元素含量和主成分分析,纤维类和金属类附着的土壤可以与其来源具有较好匹配效果;由于鞋子(橡胶类)经过较长的路线后,鞋底附着的土壤反映经过路线的综合信息,其更多情况下鞋底样品与最后经过的土壤源更相近,主成分分析结合欧氏距离对鞋底土壤源指示起到一定作用。因此,纤维类、金属类和橡胶类附着物可为未知土壤样品来源推断提供依据,对于土壤源指示有一定帮助,但实际应用中需要采用多种分析方法结合环境信息进行综合判断。本次模拟试验可为不同附着物取样方法得到的土壤样品的比对和源指示提供...

Study on Soil Sampling Methods from Different Attachments and Source Indication in Forensic Evidence

Soil plays an important role in traceability and comparison in forensic evidence due to its characteristics of extensiveness and easy adhesion. To clarify the role of sampling methods for different attachments on soil characteristics and source indication of soil, a simulation experiment was conducted for long route chosen in urban-suburbs. The original soils were collected in different road sections and under different environmental conditions. At the same time, soils attached fiber (gloves), metal (spades) and rubber (shoe soles) were simulated at each sampling point. Two methods of dry brushing and water washing/drip washing were used for sampling attached soils on different attachments. The X-ray fluorescence spectrometer (XRF) was used to analyze the element concentrations in soil samples. The results showed that the sampling methods had no significant effect on the elemental contents of soil samples attached to fiber and rubber. However, dry brushing method was more convenient and faster for operation than water washing. The drip washing was better than dry brushing for metal-attached soils. Based on soil element contents and principal component analysis, soils attached to fiber and metal had a better matching result with its source. After a longer route, soils attached to the sole reflected the combined information of the route passed, and sole samples were more similar to the last soil source passed more often. The principal component analysis combined with the Euclidean distance played a role in the indication of soil attached shoes and their sources. Therefore, the attachments of fiber, metal and rubber can provide a basis for inferring the sources of unknown soils and are helpful for soil source indication. However, proper selection and execution should be based on a variety of analytical methods combined with environmental information for comprehensive judgment. This simulation experiment can provide a basis for comparison and source indication of soil samples obtained from different attachments with proper sampling methods.