1. Scope

This procedure provides for production and quantification of microplastic particles and fibers ranging in size from 100um to 300um to be used as quality control reference samples in the collection practices, preparation practices and analysis methods used on all matrices of high and low turbidity water samples including municipal sewage for determining the presence of microplastic particles and fibers. Plastic polymers of specific types are ground-up into smaller sizes, separated into desired particle and fiber size fractions and quantified for use as quality assurance and quality control reference samples. Two types of practices are proposed: 1) Mass-based microplastic standards, prepared in large batches of a simulated water matrix: Bulk quantities of reference microplastics are measured in terms of mass on a balance and added to simulated water matrix substitute. For Raman and IR, the analysis yields counts, not mass; thus an estimate would be made of the approximate number of particles per mass microplastic. This practice requires assessment of the standard deviations of both the microplastic mass / sample within the batch, as well as the equivalent number of particles per sample. 2) Count-based microplastic standards: Microplastic reference sample vials are produced for spiking water samples to test collection, preparation and analytical recovery. The vials contain a range of microplastic concentration levels in which the plastic types and morphologies of all particles in the vial have been recorded. Reference microplastics for each vial are documented with microscopy, to enable their morphologies to be checked against the particles identified in analytical lab.

Keywords

Microplastic, microplastics, polymers, PET, PE, PS, PP, HDPE, LDPE, microplastic pollution; microplastic contamination; microplastics in drinking water, microplastics in wastewater; influent; effluent; raw sewage; collection procedures; sampling procedures; quantification procedures; sample preparation; all water matrices; high turbidity waters; low turbidity waters; calibration samples, reference samples, mass-based, count-based, proficiency samples, analytical quality assurance, quality assurance, quality control, grinders,

Rationale

Microplastics are now recognized as pervasive in the environment - including wastewater effluent, the ocean water column, sediments, animal tissue and even drinking water. This pervasiveness has led to product bans for small plastics, such as microbeads used in cosmetic products, to larger plastic items that can degrade into microplastics, such as bags and straws. In addition, there are new and planned requirements to monitor microplastics in the environment, wastewater effluent and in drinking water. Implementing monitoring programs requires reliable standardized methods and best practice guidelines. Such methods enable comparison of studies, and the ability to compare quantification among sources. Although the quantification and characterization of microplastics in samples has been occurring for more than a decade, the results are not necessarily reliable or comparable because neither standard field and laboratory methods for collection and identification nor the reference materials necessary for quality assurance yet exist. The new standards will be used for QA/QC and risk assessment by local, state and federal agencies, industry, academia, and active NGOs.

The title and scope are in draft form and are under development within this ASTM Committee.