Soil Colour and Plant-Wax Markers: Application in Forensic Investigations under Urban Subtropical Environments

Most cases involving soil in criminal investigations in Brazil have focused on the chemical and mineralogical analyses of soil fractions without including the organic matter. The organic fraction contains plant-wax markers which may be useful to “fingerprint” forensic soils due to their chemical diversity, relative longevity and resistant nature. The aim of this study was to test the long- (kilometre), medium- (metre) and short- (centimetre) scale variability of plant-wax biomarkers in a forensic context in anthropised urban soils and soils developed under subtropical conditions. Two areas from the Curitiba municipality and two areas from the Colombo municipality, Paraná State, South Brazil, were selected. Soil colour analysis was carried out to obtain reflectance data over the 360–740 nm wavelength range. Furthermore, plant-wax marker compounds (n-alkanes and fatty-alcohols) were assessed by extraction and separation into different classes and an analysis of the compounds by gas chromatography (GC/MS). The compositions of the wax-marker profiles were different in samples collected side-by-side, showing sensitivity to local variations under subtropical conditions and in areas under intense human urban disturbance. Under these conditions, biomarkers may be used in real crime scenes, even on a micrometric scale of variation.

Parks and Recreational Areas as Sinks of Plastic Debris in Urban Sites: The Case of Light-Density Microplastics in the City of Amsterdam, The Netherlands

Soils of parks and recreational areas are potential sinks of microplastics because they are under multifunctional use. The aims of this research were to quantify and determine the types and abundance of light-density microplastics in one of the most cosmopolitan cities of the world: Amsterdam, the Netherlands. Therefore, potential differences between the city districts were explored through the assessment of light-density microplastics’ concentrations in soils together with the soil properties. Microplastics were extracted from 74 soil samples. Predictions of microplastic concentrations and soil characteristics were made for the entire city by using ordinary kriging; 97% of the samples contained microplastic particles (MPPs), and on average, there were 4825.31 ± 6513.85 MPP/kg soil. A total of 21 hotspot samples were identified, and all of them contained LDPE, which represented 40.82% of the plastic types, in addition to 35.06% PAC and 15.58% natural polyamide. Other types of plastics were PP (0.19%), PS (1.30%), bioplastic (0.19%), PA (0.37%), PU (0.56), PVC (0.19%), and unidentified plastics (0.19%). There were no significant differences in MPP concentration between city districts. Our results showed that MPPs are abundant in urban soils, which represents a high risk for soil life. Further studies are required for identifying the sources of this pollution.