Breaking barriers in passive sampling: The potential of PTFE membranes in the monitoring of hydrophilic micropollutants.

Passive samplers are key tools to sample hydrophilic micropollutants in water. Two main approaches address the influence of hydrodynamics: (1) determining site-specific sampling rate (RS) by characterizing kw, the mass transfer coefficient of the water-boundary layer (WBL), and (2) reducing WBL impact using a diffusive material to control the uptake. The first requires calibration data and the second has only been achieved using fragile diffusive material. This study assesses the transfer of hydrophilic contaminants through polytetrafluoroethylene (PTFE; 30 µm thick), a new membrane material with lower sorption than commonly used polyethersulfone (PES). Combined for the first time in a Chemcatcher-like configuration, we calibrated the modified samplers for 44 micropollutants to provide RS - kw relationships for in-situ RS determination (approach 1). Micropollutants accumulated over 2000 times more on the sorbent than on PTFE. PTFE-based RS (0.027 to 0.300 L day-1) were 2.5 higher than previously reported with PES. Membrane property measurements (porosity, tortuosity) indicated that accumulation is primarily controlled by the membrane. Extrapolation indicated that using thicker PTFE membranes (≥ 100 µm) would shift uptake control entirely to the membrane in river conditions (approach 2). This finding could enable RS prediction based on contaminants properties, thus representing a significant advancement in passive sampling.

A common framework to situate digital and physical traces in time.

In this article, three main approaches to situate forensic traces in time were revisited under the prism of the Sydney Declaration and adapted to be applicable to a large range of physical and digital traces. The first approach is based on time tags which are time-based characteristics produced as the result of an activity at a specific time. They can either be directly related to time (i.e., time stamps) or indirectly (i.e., time indicators). While relatively straightforward, time tags require scientific knowledge to be correctly interpreted and to account for the risks of desynchronisation, anomalies and manipulation. The second approach is based on time dynamics and aim at measuring changes that occur as a function of time, such as caesium pulsation (i.e., on which international atomic time is based) or body cooling after death (i.e., from which time since death can be inferred). However, time dynamics phenomena are generally also influenced by other case-specific factors (e.g., environmental factors), and thus more difficult to reliably implement in practice. Finally, the third approach relies on relative sequences, using information unrelated to time, such as relative positions or dynamics of traces at the scene. As each approach has its potential and limitations, a combination of traces from different (both material and digital) sources and approaches is recommended to answer time questions in practice (When? How long? In which succession?) and enhance the reliability of the dating endeavours. It is strongly recommended to consider the principles of the Sydney Declaration when implementing or developing dating methods, as they point at potential issues that are often forgotten in forensic research and practice, such as uncertainties linked to the concept of trace, scene investigation, the asymmetry of time, the importance of context and the multiplicity of purposes. Future research should focus on improving the reliability of these dating approaches by combining and systematising their usage in investigative practice, as well as in broader intelligence processes.

Signs of how the Sydney Declaration article is received in the forensic science literature.

The Sydney Declaration is an initiative led by an informal group of forensic scientists with diverse backgrounds. It offers a vision of forensic science based on the trace, as a vestige of a past event related to security or a possible law violation. An article published in Forensic Science International (FSI) introduces to this view [1]. Our investigation delves into how the forensic science literature has received this article (the SD article), nearly two years after its publication. One of the main challenges of this exploratory study was to define the appropriate scope of forensic scientific literature, within which the SD article must be located. In general, the publishing domain is quickly evolving, with many competing players, while still being structured around standard academic disciplines. The forensic literature, meanwhile, is scattered and poorly connected. This reflects the fragmentation of practice and research in forensic science, and the difficulty of situating a scientific activity in such a way as to bring out its forensic substance. Nonetheless, the SD article fills a gap. By deciphering the critical concept of trace, it highlights how pivotal forensic science is in addressing societal challenges. Scholarly literature expresses clear quantitative interest in the SD article. It has received significant qualitative citations on multiple levels and dimensions, in a highly relevant manner and in accordance with its aim of providing a forensic foundation for various debates that have been conducted separately, notably over the last fifteen years.