Research On Detection Methods Of Microplastics

Plastics are widely used in human social life due to their excellent acid resistance,alkali resistance,abrasion resistance,transparency and chemical stability.Affected by its own structure and properties,plastics are difficult to degrade in the natural environment.Under long-term physical,chemical or biological actions such as corrosion,oxidation,and weathering,plastics are decomposed into micron or nanometer-level fibers,films,particles,etc.These tiny particles have properties such as hydrophobicity and high specific surface area.So their surface is easy to adsorb the surrounding environmental pollutants and pathogens.It may even threaten the ecosystem through food chain transmission and enrichment.Therefore,the environmental pollution and poisoning problems received a broad beam of light from society.In this paper,based on Raman spectroscopy,infrared spectroscopy,and matrix-assisted laser analysis and ionization time-offlight mass spectrometry(MALDI-TOF MS),a method for detecting microplastics in marine organisms,liquids and soil is established.The results achieved are as follows:(1)A spectroscopic method was established to detect six types of microplastics in bivalve marine organisms,including polypropylene(PP),polyamide(PA)and others.The digestion efficiency of different digestion reagents and their influence on microplastics were explored.Among them,the use of potassium hydroxide to digest for 36 hours at 40℃ is the best digestion method for bivalve marine organisms.Furthermore,by comparing the effects of different filter membranes on filtration and spectral detection,it is determined that the economical mixed cellulose filter membrane with little influence on spectral detection is the best choice.Afterword,the detection methods of microplastics under different conditions are explored.When the particle size of microplastics is large and the sample amount is small,the micro-infrared ATR mode,imaging mode,and micro-Raman single-point detection mode are used for detection(which adapted the determination of particle above 75μm).For microplastics with small particle size but small sample volume,use the Raman microscopy single-point detection mode to test(which adapted the determination of particle above 15μm),Use Raman microscopy or infrared microscopy imaging modes for detection when the particle size is smaller or the sample volume is large(which adapted the determination of particle above 1μm).(2)A method based on cloud point extraction combined with matrixassisted laser desorption/ionization time-of-flight mass spectrometry was established to detect microplastics and nanoplastics in liquid environments.By optimizing conditions such as sample preparation methods,matrix selection,and laser energy of the instrument that affect the ionization of microplastics,this research has developed a MALDI-TOF detection method suitable for three types of microplastics:PET,PL A,and PA.And with the aid of scanning electron microscope,the particle size and quantity of microplastics and nanoplastics were analyzed.Moreover,according to this method,it was discovered that a large amount of microplastic particles were released in the teabag-PET.(3)By comparing the three solutions of water,saturated sodium chloride and saturated calcium chloride,a method for detecting networked microplastics in soil based on the saturated calcium chloride reagent combined with Fourier transform infrared spectrometer was established.And according to this method,this study analyzed the amount of mesh microplastics in Daxing District,and verified that the longer the dust-proof net was laid,the more serious the microplastic pollution.