Polyethylene Identification in ocean water samples by means of 50 keV energy electron beam

The study presented hereafter shows a new methodology to reveal traces of polyethylene (the most common microplastic particles, known as a structure of C_2 H_4) in a sample of ocean water by the irradiation of a 50 keV, 1 uA electron beam. This is performed by analyzing the photon (produced by the electrons in water ) fluxes and spectra (i.e. fluxes as a function of photon energy) at different types of contaminated water with an adequate device and in particular looking at the peculiar interactions of electrons/photons with the potential abnormal atomic hydrogen (H), oxygen (O), carbon (C), phosphorus (P) compositions present in the water, as a function of living and not living organic organisms with a PO4 group RNA/DNA strands in a cluster configuration through a volumetric cells grid.


Introduction
Plastic is the most common type of marine debris found in oceans and it is the most widespread problem affecting the marine environment. It also threatens ocean health, food safety and quality, human health, coastal tourism and contributes to climate change [1,2,3,4,5]. Plastic debris can come in many different shapes and sizes, but those that are less than five millimeters across (or the size of a sesame seed) are called "microplastics". One of the most common microplastic in use today is Polyethylene, with most of the known kinds having the chemical formula (C2H4)n. It is a linear, man-made, homo-polymer, primarily used for packaging (plastic bags, plastic films, geomembranes, containers including bottles, etc.).
As of 2019, over 100 million tons of polyethylene resins are being produced annually, accounting for 34% of the total plastics market. This is an emerging field of study, and not much is known yet about microplastics and their impact on the environment. The NOAA Marine Debris Program is pursuing efforts within the NOAA to research this important topic.
Different standardized field methods have been developed for the collection of microplastic samples in sediment [6,7,8,9,10,11,12,13], sand and surface water which continue to be tested.
In the end, the field and laboratory protocols will allow a global comparison of the quantity of microplastics released into the environment, which is the first step in determining the final distribution, impacts and fate of these debris.
Microplastics come from a variety of sources, including larger plastic debris that degrade into smaller and smaller pieces. In addition, microspheres, a type of microplastic, are tiny particle pieces of plastic polyethylene that are added as exfoliators to health and beauty products, such as some detergents and toothpastes passing easily through water filtration systems, posing a threat to aquatic life.
The most visible impacts of marine plastics are the ingestion, suffocation, and entanglement of hundreds of marine species. Marine wildlife such as seabirds, whales, fishes and turtles, mistake plastic waste for prey, and most die of starvation as their stomachs are filled with plastic debris. They also suffer from lacerations, infections, reduced ability to swim, and internal injuries. Floating plastics also contribute to the spread of invasive marine organisms and bacteria, which disrupt ecosystems. Plastic degrades (breaks down into pieces), but it does not biodegrade (break down through natural decomposition). This has become a problem over time, as all the plastic pieces that they have been generated over the last seven decades have steadily increased theirs presence as ppm creating a biological alteration.
According to the United Nations Environment Program, these plastic microspheres first appeared in personal care products about fifty years ago, with plastic replacing more and more natural ingredients. Until 2012, this problem was still relatively unknown, with an abundance of products containing plastic microspheres on the market and leading now, to an increase microplastic detection and identification demand.
Ocean water also contains microorganisms, live matter and not, such as viruses, bacteria, and microorganisms like plankton with a different PO4 phosphorus content [14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29]. Viruses, for example, are intracellular parasites composed of a nucleic acid surrounded by a protein coat, the capsid. Some viruses contain a lipid envelope, derived from the host, surrounding the capsid. The nucleic acid found in viruses can consist of either RNA or DNA. RNA is composed of nucleotides, each containing a sugar (deoxyribose), a Nitrogen containing Base (Adenine, Uracil, Guanine, and Cytosine), and a phosphate group PO4. Members of the family Coronoviridae measure 80-160 nm in diameter. Generally, there are 1-10 Million viruses and about 100,000 to 1 Million bacteria cells for each milliliter of ocean water.
The proposed methodology is based on a sub-atomic particles analysis and their subsequent detection, able to identify polyethylene particles in water among microorganisms. It could be an interesting research approach for the ocean studies field and for the food and beverage industries field in order to detect microplastic contamination in their products. This type of approach would make easier testing water samples and analyzing data in real time in comparison to the state of the art of others detection processes, and also allows test procedures for quality assurance in the food and beverage industries with a simple hardware.

Assumptions & Calculations
The physical model under analysis and its simulation by MCNPX Monte Carlo simulation sub atomic particles code [30,31,32] are based on an electron beam source of 50 keV and 1 µA, easily accessible from an extraction line of an industrial linear/circular particle accelerator, interacting with the water sample target. The beam energy and current have been based on cross sections considerations and radiation requirements; the beam interacts with a cylindrical sample volume, with axis on x, of ocean water of radius r=5 cm and height h=10 cm as s sample tank ( Fig. 1) which is analysed at x=10 cm through a double plates ionization chamber detector. The ocean water, taken into account is chemically known as showed in Table 1 [12].   The polyethylene particles have been described in 11 cluster configurations (Table 4)        It must be underlined that it has been taken into consideration also a benchmark model in order to evaluate a potential enrichment in microorganism, bacteria and viruses which can be alter mainly the carbonium and in particularly the phosphorus PO4 group analysis outcome; these all are analyzed on multiple "tallies" (control check volumes/surfaces) in order to evaluate energy distributions and particles mean free path (yellow squares, Fig 4). In order to do that, in the benchmark, it has been kept constant a 100-ppm polyethylene content in the ocean water    The Photon fluxes and spectra can discriminate the amount of polyethylene contamination thanks to its own "particle signature" in terms of photon flux at the detector point combined with the spectrum analysis, as reported for 30 keV, 40 keV, 50 keV.
As shown in Figs  1. the 0.7-ppm microorganisms case can be discriminated thanks to the photon flux counts at the detector evaluated on the 30 keV, 50 keV spectrum lines compared to the "ocean water+100 ppm polyethylene" at the same energy conditions.
2. the 7-ppm microorganisms case can be discriminated thanks to the photon flux counts at the detector evaluated on the 50 keV spectrum line compared to the "ocean water+100 ppm polyethylene +0.7 ppm microorganisms" at the same energy condition.
3. the 70-ppm microorganisms case can be discriminated thanks to the photon flux counts at the detector evaluated on the 40 keV, 50 keV spectrum lines compared to the "ocean water+100 ppm polyethylene +7 ppm microorganisms" at the same energy conditions. 4. the 700-ppm microorganisms case can be discriminated thanks to the photon flux counts at the detector evaluated on the 40 keV, 50 keV spectrum lines compared to the "ocean water+100 ppm polyethylene +70 ppm microorganisms" at the same energy conditions.

Summary
This study proposes a new approach to identify low contaminations of polyethylene mixed in water showing a Monte Carlo simulation performed by the MCNPX subatomic particles code evaluating the secondary photon (generated by an electron beam of 50 keV and 1 µA) energy spectra and fluxes to be revealed by an adequate detector.
Different type of contamination grades can be discriminated thanks to the their trend Vs photon/s*cm 2 evaluated on at least three energy bins:30-40-50 keV. Every single contamination is unique in its own "spectrum photon signature" and flux acting as unique identifier in the detection process so that, in combination with the microorganisms analysis can give the ppm amount of polyethylene in: ocean water, drinking/not drinking water, food/beverage processing.