Global Journal of Science Frontier Research, H: Environment & Earth Science, Volume 22 Issue 5

© 2022 Global Journals 1 Global Journal of Science Frontier Research Volume XXII Issue V Year 2022 44 ( H ) Version I Validation of X-Ray Fluorescence Spectrometer Technique to Determine Heavy Metal Concentrations in Soil Samples biocides like vector controls. The movement of heavy metals in the Earth’s spheres depends on temperature, direction and movement of surface waters, speed of wind and circulation of air mases. Other factors include partition coefficient, vapour pressure, polarity and molecular stability [1,2,4–6,10–12]. Deliberate soil pollution occurs through wastewater irrigation, the use of pesticides and fertilisers, animal manures, leaded paint, mine tailing, spillage of petroleum distillates, sewage sludge, coal combustion residues and waste dumping. Non- deliberate pollution can occur through the flooding or rivers and seas bringing sewage and contaminated waters to the land. This is in addition to accidents entailing vehicles conveying toxic chemicals. Microbial or chemical degradation cannot occur to heavy metals since they are non-degradable and thus remain in the soil for a very long time [1,2,4,13–16]. The ecosystem is in danger due to heavy metals entering the food chain. Their properties also affect the biodegradability of organic pollutants which causes them to become less degradable and consequently causing a twofold effect of polluting the environment. Heavy metals present in the soil cause all the biospheres to be at risk and are taken up through direct ingestions of the heavy metal or ingestions through food or water that contains the heavy metal after absorbing it. Uptake of the heavy metal may be affected by the soil property like pH, porosity, colour and natural chemistry [1,2,4,13–16]. Elements or chemicals which are not usually present, exist at higher level concentrations and cause damage to organisms, are termed as “soil pollutants”. Modern technology such as agrochemical use, together with industrialisation, has caused several contaminants to be present in soil [17]. Soil contamination can be a deliberate action, such as using animal manure, fertilizers, wastewater irrigation, waste dumping, mine tailing, pesticides, sewage sludge and much more [1,2,13,15,16,18]. Watering agricultural land with untreated sewage and wastewater is one of the main complications of adding pollutants to the soil [15,18]. Some pollutants remain in the soil since they are non-biodegradable, thus they would not be able to undergo degradation even if it is chemical or microbial [2]. The soil’s sorptive capacity is affected by the heavy metals’ bioavailability. Metal can only be up taken in the ionic form by plants and soil biota. Due to the metal’s affinity, they adsorb to surfaces of humus, calcium carbonate salts, iron and manganese hydrous oxides, together with clay minerals. Other metals can form complex compounds by having an affinity with organic molecules. A factor that affects the sorption process is pH, the less acidic the soil, the higher the sorption, whilst the higher the soil acidity, the more it is desorbed and released [17]. One of the ways to analyse the presence and concentration of heavy metals is through XRF spectrometry. Element analysis is recognised through the excitement of individual atoms through an external energy source, which goes on to release X-ray photons that emit energy or wavelength which is distinctive for each element. The energy released sets of several photons are used to identify and quantify the element present. Both solids and liquids can be analysed by the XRF, to analyse major and trace elements. Elements are identified under certain conditions through the release of distinctive radiation from the atom’s inner electronic shells. Emitted quanta of radiation release X-ray photons which have specific energies, thus allowing for the atom’s source to be identified. Since only the inner electron shells are involved during the X-ray emissions, the chemical bond is not taken into consideration. Samples have to be homogenous and refined to get good results when using powder form. Powder form has to be refined, as more than 50 µm in particle size can show errors of 50%. This is due to the variation of the extent of the X-ray penetration with energy [19,20]. II. M ethod and M aterials Five soil samples were collected from the fields of the Government Farm in G ħ ammieri. A detailed map showing the location of the samples is given in figure 1. Each sample gathered comprised of a mixture of soil from five sites; the four corners of the plot together with the centre. The soil samples were placed in sterilized labelled plastic containers (A-E) and taken to the laboratory. The soil samples were air-dried at ambient temperature after being placed in plastic trays for 48 hours. These were then homogenised and sieved using a 45 µm mesh to remove any plant matter or stones that were present in the sample. Each of the five samples was then separated into two identical batches so that five were used for the XRF and the other identical five will be sent to be tested by the ICP-MS. One set containing five samples was oven-dried for 24 hours at ~110°C using watch glasses. The process was carried out meticulously so that sample cross-contamination, as well as external contamination would not occur. The soil samples were then sieved again to make it more homogenous and finer and were then stored in sterilized plastic containers containing desiccators until further use. Concentrations of arsenic, lead, cadmium, chromium, copper, nickel, mercury, thallium and zinc were determined using the S2 Ranger Energy Dispersive X-Ray Fluorescence (EDXRF) spectrometer situated at the laboratory of the Department of Chemistry, at the University of Malta. The XRF spectrometer was calibrated before each batch of the sample was placed in the instrument. A copper disc calibration was analysed first, followed by a quality check. Each sample