Mikroplaster på åkermark. Jes Vollertsen Professor i Miljøteknologi, Aalborg Universitet

Transkript

1 Mikroplaster på åkermark Jes Vollertsen Professor i Miljøteknologi, Aalborg Universitet

2 Development in plastic production PlasticsEurope, 2015

3 Research in microplastic has been focused on the oceans BUT The majority of production, consumption, and wasting of plastic is on land Most research on marine environment consider terrestrial and freshwater environments as a source and transport pathway of microplastic to marine systems Very few studies address microplastic in terrestrial environments

4 Plastik er mange ting Hvad tænker I på når jeg siger plastik? Men bildæk er også plastik Maling er plastik Mælkekartoner er et PE-cellulose komposit materiale Kunststof som i tøj er plastik (fx fleece = polyester) Plastik er alle de polymerer vi gør brug af Plastiks mangfoldighed giver mange udfordringer når man skal analysere

5 National estimates on microplastic literature studies and mass balances (no measurements)

6 Main sources of microplast Danish numbers

7 Mikroplastik kommer i mange størrelser Oftest defineres mikroplastik som plastik partikler mellem 5 mm og 1 μm Mikroplastik kommer i mange former Eksempler på virkelige plastik partikler μm Det store spænd i størrelse giver mange udfordringer når man skal analysere mikroplastik

8 Der er heldigvis andet end mikroplastik derude Mikroplastik er altid blandet ind i et eller andet Drikkevand, havvand, spildevand, fødevarer, dyr, jord, sediment For at analysere for mikroplastik skal man først have det ud af den matrix det er gemt i

9 Fremgangsmåde Prøver med mikroplastik Oprensning og koncentrering Jord Sediment Vandige prøver med lidt organisk stof Vandige prøver med meget organisk stof Slam Væv med højt fedtindhold osv Forskellige prøvetyper kræver forskellig oprensnings Analyse af de oprensede partikler Ikke alt man har koncentreret er plastik Forskellig metode for analyse af store stykker plastik og analyse af små stykker plastik

10 Fremgangsmåde Sampling Partikler > ca μm: Oprense matrix Fisk partikler ud med pincet og analyser enkeltvis Extracting microplastic particles from the matrix Identifying: Material Size Shape Mass Partikler < ca μm: Oprense matrix Scan et filter eller et mikroskopivindue med et specialiseret analyseudstyr

11 Analyse maskiner Partikler > ca μm Langt de fleste nyere undersøgelser af mikroplaster i verden er lavet med denne type Partikler < ca μm Kun ganske få undersøgelser i verden er lavet med denne type udstyr

12 The project Mikroplaster i kretsloppet High inlet plastic concentration Wastewater treatment processes catch plastic in the sludge and degrades/fragments some plastic Low outlet plastic concentration Most but not all plastic is recovered in the sludge Soil application No sludge 1 t/year over 30 years 3 t/year over 30 years Expectation: Plastic is degraded into finer particles and possibly reduced to sizes below our detection limits maybe it is even completely mineralized

13 Sampling of soils at Fältförsök Petersborg Soil from fields that have received: No sludge 1 ton TS/year 3 ton TS/year

14 Hvor verden er i 2018 og hvor vi startede

15 Dette studie er det første i verden af sin art Der findes ingen mätning af små stykker mikroplaster i åkermark Vi havde for et år siden lavet de første (mere eller mindre mislykkede) forsøg må at mäta mikroplaster i åkermark Vi vidste nogenlunde hvad der virker og hvad der ikke gør, men vi havde ikke metoderne på plads

16 Mikroplaster i mark metodeudvikling Fra 50 g til 500 g Fra funnel til raket Inddelt i 2 metoder 50 g g

17 Analyse metode <500 µm Wet sieving Sample Flotation/ sedimentation

18 Analyse metode <500 µm Conclusion: The analytical method has to be changed What a filter should look like at this stage Enzymatic treatment Oxidation with catalyst Something went wrong Iron flakes everywhere We had to re-develop the last part of the method because the Swedish soil did not behave like the other soils we had worked with.

19 Analysemetode >500 µm The soil was aggregated so a wet sieving was necessary Soil is dried Soil is sieved through a 8 mm, 6 mm, 4 mm, 2 mm, 1 mm and 500 μm sieve-tower

20 Analysemetode >500 µm The dry soil was floatated in ZnCl 2 The floating particles are collected Floating particles Non-floating particles The soil was cleaned in H 2 O 2 Now the particles are ready for visual sorting.

21 Step 1: Microscope analysis >500 µm

22 Step 2: ATR analysis of extracted candidates >500 µm Cellulose The particles looking like plastic (not plant material and stones) are analysed by ATR A spectrum is acquired and compared to a reference spectrum. Not perfect clean particle, cellulose is also in the PE spectrum. Often very weak signals hard to analyse

23 Results so far A field close to AAU university Number of plastic particles Range Soil A Soil B Soil C μm 0 In progress μm 0 In progress μm 5 a In progress 2 b 500 μm-1000 μm In progress In progress In progress Kg DM μm-500 μm In progress In progress In progress * No yet analysed a PE, PP, 3xPaint on wood b PET, PP Did not find plastic lager than 2000mm, but would not expect to because sludge is not expected to have such large particles. The field was relatively remote. So little direct plastic contamination (other than sludge) The field in Sweden

24 ATR analysis >500 µm We were not satisfied with all the spectra from the small ATR Some of the materials are difficult to quantify with the single point bench ATR-FTIR We will here use a more advanced approach, the slide-in ATR for the μftir This can give us a resolution down to approx. 1 μm and hence a reliable spectrum even of problematic samples

25 Mikroplaster i slam Method development: Going from 0.1 g to 5 g dry matter A lot of treatment and a lot of time!! Sludge is the most difficult matrix to prepare for analysis We have discussed this with other researchers around Europe and they agree and nobody has yet really found the solution. The method is now ready, and we can prepare sludge (it is a long and tedious process)

26 Let s play with numbers The Danish study we did showed approx g plastic per g dry matter We today believe this is over-estimated Let s assume g/g Let s assume 1 ton sludge/ha over 30 years Let s assume the plastic is distributed in the upper 0.30 m of the field Total sludge load: kg TS / m 2 = 3 kg TS m 2 Total MP load: * 3 = kg MP / m 2 The weight of 1 m 2 at a plowing depth of 0.30 m approx.: 0.3*1500 = 450 kg / m 2 Calculated MP concentration: / 450 = 7 mg/kg Is this little or much? It corresponds to the levels of many metals in soil

27 The final results of this study will be published early summer 2018 NOT THE END