Adulteration of fuels is a major problem, especially in developing and third world countries. One such case is the adulteration of diesel oil by kerosene. This problem contributes to air pollution, which leads to other far-reaching adverse effects, such as climate change. The objective of this study was to develop a relatively easy measurement method based on an inexpensive, handheld Abbe refractometer for the detection of adulteration and estimation of the ascending order of the amount of kerosene present in adulterated samples in field conditions. We achieved this by increasing the volume of pure diesel sample in the adulterated diesel oil, and measuring the trend of refractive index change, and next, exploiting the true and ideal permittivities of the binary mixture. The permittivity can be obtained with the aid of the measured refractive index of a liquid. Due to the molecular interactions, the true and ideal permittivities of diesel–kerosene binary liquid mixture have a mismatch which can be used to screen for adulterated diesel oils. The difference between the true and the ideal permittivity is the so-called excess permittivity. We first investigated a training set of diesel oils in laboratory in Finland, using the accurate table model Abbe refractometer and depicting the behavior of the excess permittivity of the mixture of diesel oil and kerosene. Then, we measured same samples in the laboratory using a handheld refractometer. Finally, preliminary field measurements using the handheld device were performed in Tanzania to assess the accuracy and possibility of applying the suggested method in field conditions. We herein show that it is not only possible to detect even relatively low adulteration levels of diesel in kerosene—namely, 5%, 10%, and 15%—but also it is possible to monitor the ascending order of adulteration for different adulterated diesel samples. We propose that the method of increasing the volume of an unknown (suspected) diesel oil sample by adding a known authentic diesel sample and monitoring excess permittivity is useful for the screening of adulterated diesel oil in field measurement conditions.

Visual classification has been one of the major methods in the sampling and identification of microplastics. In this study, however, a commercial particle analyzer was used to image and analyze a dilute mix of microplastic particles (MPs) dispersed in filtrated and de-aerated tap water. The device provides a relatively easy and fast procedure for obtaining ultra-high-definition imaging, allowing the determination of shape, size, and number of 2D-projections of solid particles. The image analysis revealed clear differences among the studied different MPs originating from the grinding of five common grades of plastic sheets as they affect the image rendering differently, principally due to the light scattering either at the surface or in the volume of the microplastics. The high-quality imaging of the device also allows the discrimination of the microplastics from air bubbles with well-defined spherical shapes as well as to obtain an estimate of the size and number of MPs in a snapshot. We associate the differences among the shapes of the identified MPs in this study depending on the plastic type with known physical properties, such as brittleness, crystallinity, or softness.