Fenomenet mikroplaster har på senare tid blivit allt mer uppmärksammat i jord och sediment, varje dag kommer nya artiklar om mikroplasternas förekomst eller verkan. Intresset har ökat markant för mikroskopiska skräppartiklar i miljön. Mikroplast definieras som plastpartiklar mindre än 5 mm. Det har konstaterats ha en skadlig påverkan på organismer (Lassen et al., 2015). Det är ett stort miljöproblem som mikroplasterna skapar då det har visat sig ge skadliga effekter på vattenlevande organismer speciellt. Organismerna förväxlar mikroplaster med plankton och får i sig mikroplaster istället för föda. Det har inte gjorts större studier på hur marklevande organismer påverkas av dessa mikroplaster, men det misstänks även kunna innebära problem när slam sprids på åkermark. För att analysera mikroplaster måste dessa isoleras. Målet med detta arbete var att kunna separera dem från det övriga materialet. Detta gjordes genom att man tillsatte olika kemikalier vid olika temperaturer och förhållanden för att undersöka hur mikroplasterna påverkas av olika omständigheter. Provtagningen för sediment skedde på en och samma hamnbassäng som hade ett djup på 0 – 0,3 meter och jorden som undersöktes inköptes på Plantagen i Uppsala. Proverna delades upp i hanterbara mängder inför processen som bestod av olika steg. Det var känt sedan innan vilka kemikalier det rörde sig om, både när det gäller separationslösning och digereringsmedel. De vanligaste separationslösning var natriumklorid, kalciumklorid, zinkklorid och natriumjodid. I denna studie undersöktes dock bara natriumklorid och kalciumklorid, då både zinkklorid och natirumjodid visat sig påverka miljön negativt och eftersom det åtgår flera hundra gram salt per prov ansågs det inte nödvändigt att undersöka dessa två. Efter närmare undersökning så visade det sig att kalciumklorid hade bäst densitet på 1,4 g/cm3 vilket gjorde att oönskade partiklar sjönk till botten och de fyra vanligaste plasterna (PE, PET, PP och PVC) hade möjlighet att flyta upp till ytan. Med hjälp av separationskolonnen (se figur 2), som användes i denna studie, kunde den översta fasen enkelt dekanteras från övriga provet med hjälp av ventilen som delade upp kolonnen. Eftersom separationskolonnen inte kunde hantera stora provmängder undersöktes alternativa separationstekniker men eftersom dekanteringssteget är kritiskt så lämpade sig inte de andra alternativen. När det kommer till digereringsmedel så var det natriumhydroxid, salpetersyra och väteperoxid som undersöktes. Digereringsstegets uppgift är att lösa upp övrigt material i provmatrisen såsom organiskt material. Det var viktigt att testa en bas, en syra och ett oxidationsmedel för att veta hur plasterna reagerade. Vidare så kombinerades dessa digereringsmedel med olika temperaturer om 25 °C, 50 °C och 80 °C. I figur 3 visar diagrammet att väteperoxiden inte undersöktes vid 80 °C, det beror på att det är så pass mycket annat material i sediment och jord att riskerna var för höga, det är okänt hur häftiga reaktioner detta kan skapa. Det visade sig att salpetersyra vid 50 °C lämpade sig bäst för att lösa upp så mycket som möjligt av matrisen utan att påverka de fem vanligaste plasterna för vidare analys. Eftersom storleken på mikroplasterna sträcker sig över 0–5 mm filtrerades proverna genom tre filter. Ett grovt filter på 1 mm maskstorlek, ett filter på 100 μm och det minsta filtret på 10 μm. Den grövsta filtret kunde utvärderas visuellt med ögat och därifrån räkna antal plastpartiklar, filtret på 100 μm utvärderades under stereomikroskop och partiklarna som kunde tänkas vara plast plockades ut och sattes på en bit koltejp som fick genomgå en SEM-analys för att fastställa vilka partiklar som var plast. Sista och minsta filtret på 10 μm går igenom SEM-analysen direkt för att de är så pass små partiklar och genom att titta på sammansättningen av ämnen på enskild artikel kunde bedömningen göras ifall det var en plastpartikel, mineral eller organiskt material. / The phenomenon of micro plastics in soil and sediment has recently become more and more noticeable and every day new articles are published about the presence and effects of micro plastics. The interest has also increased significantly for micro plastic litter particles in the environment. The definition of micro plastic particles is that they are smaller than 5 mm in size. The finished and ongoing studies have shown that the micro plastics have a bad effect on the environment (Lassen et al., 2015). It has become a very big environmental problem that the micro plastics created as it has been shown to produce harmful effects on aquatic organism in particular. What happens is that the aquatic organism confuses micro plastics with plankton and they devour the micro plastics instead of food. Unfortunately, there is no major study when it comes to soil-based organism, but it can be said that they are also affected by this problem since micro plastics in soil and sediment is spread on arable land. To be able to analyze micro plastrics, these has to be isolated from other particles. This was done by adding different chemicals at different temperatures and conditions to investigate how the micro plastics are affected by different circumstances. The important part for the micro plastics is to stay true to its original form or shape even after going through different steps throughout the procedure. The sediment samples occurred from the same harbor basin that has a depth of 0 – 0.3 meters and the soil was purchased from Plantagen in Uppsala. The samples were divided into manageable amounts for the procedure to operate without complications. Studies have already shown that the chemicals that are best suited for both separation and digestive solution was sodium chloride, calcium chloride, zinc chloride and sodium iodide. In this study, however, only sodium chloride and calcium chloride were investigated, as both zinc chloride and sodium iodide did show a significant impact on the environment and furthermore required several grams of salt per sample thus they both got excluded from this study. After closer examination, it was clear that calcium chloride had the best density of 1.4 g/cm3 which was enough to separate the unwanted particles to fall to the bottom (sediment) and the four most common plastics e.g. PE, PET, PP and PVC, to float to the surface. The fractionating column (figure 2) used in this study, the top phase could easily be separated from the rest of the solution by closing the valve dividing the column. Since the fractionating column was unable to handle large number of samples, alternative separation techniques were investigated, but since the decantation step is critical, the other options were not fitted in this study. The next step in the procedure was digesting the rest of the materials in the matrix. The digestive agents, sodium hydroxide, nitric acid and hydrogen peroxide were investigated. The purpose of the digestion step was to dissolve other materials in the sample matrix e.g. organic material. It was important to investigate a base, an acid and an oxidant to really know how the micro plastic reacts. Furthermore, these digestives were combined with various temperature of 25 °C, 50 °C and 80 °C. The reason why hydrogen peroxide doesn’t have an 80 °C in the charts, figure 3, is because of the unknown reactions that could occur, since the samples of sediment and soil, contains a large amount of other materials. The decision was made to use nitric acid at 50 °C, it was most suitable for dissolving as much as possible without affecting the five most common plastics for further analysis. Since the size of micro plastics extends over 0 – 5 mm, the samples were filtered through three filters. A filter of 1 mm mesh size, a filter of 100 μ m and the smallest filter of 10 μ m. The biggest was easily evaluated by looking at the particles to decide which are plastics and not. The 100 μ m-filter was evaluated under stereo microscope and the particles that could be plastic were picked up and glued on a piece of carbon tape which then went through a SEM-analysis to determine which of these hand-picked particles were plastics and not. The final and smallest filter, 10 μm, passed through the SEM-analysis directly, these particles were too small to evaluate with the stereo microscope. By looking at the composition of the substances on a single particle, the assessment could be made if it was plastic, mineral or organic material. The important part with the evaluation made with the eye to identify which particle is plastic or not was by adding external stress, e.g. pressure, heat and other factors. It is known that plastics has a characteristic appearance, usually thread-shaped with a smooth surface. By gauging the, what we think is plastic, it could easy be decided if it’s a plastic or not. As we know, plastic has a trait of going back to its original state. If the particle caused by the external stress returned to its original form, it was considered a plastic, however if it remained deformed it was eliminated. The 100 μm is evaluated by stereo microscope and SEM-analysis, the particles that looks like plastic were picked up and glued on a carbon tape that was analyzed by the SEM-analysis. What made the SEM suitable for this study is that by looking at the composition of the substances on a single particle, the evaluation went quick by looking at the spectra. The smallest filter, 10 μm, was evaluated directly in the SEM-analysis. Using its electrons drawn to different particles of different composition, a spectrum could be produced and evaluated in the vase of a micro plastic or not, if the particle gave rise to carbon and oxygen alone onthe spectrum, it can be a micro plastic.
| Identifer | oai:union.ndltd.org:UPSALLA1/oai:DiVA.org:kth-233868 |
| Date | January 2018 |
| Creators | Thuné, William |
| Publisher | KTH, Skolan för kemi, bioteknologi och hälsa (CBH) |
| Source Sets | DiVA Archive at Upsalla University |
| Language | Swedish |
| Detected Language | English |
| Type | Student thesis, info:eu-repo/semantics/bachelorThesis, text |
| Format | application/pdf |
| Rights | info:eu-repo/semantics/openAccess |
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