Recipient Organization
CONNECTICUT AGRICULTURAL EXPERIMENT STATION
PO BOX 1106
NEW HAVEN,CT 06504
Performing Department
Analytical Chemistry
Non Technical Summary
Given the benefits that plastics bring to our quality of life, their use is likely to continue increasing in a variety of sectors. Microplastics have been intentionally produced or can form as plastic decomposes into smaller particles. These are light weight, cheap, durable materials in comparison to heavier weight metals and brittle ceramics. Even though there are efforts being made to replace common plastics with natural bio-degradable ones such as poly(lactic acid), this is not likely to occur in the foreseeable future. Therefore, we will continue being exposed to microplastics, including associated contaminants, during their service life and afterwards. Plastics are in contact with our food;thus, derivative microplastics may be ingested entering directly or indirectly into our diet. Whether or not this poses a risk is not completely clear yet. It has been implied that plain polymers in microplastics are not dangerous, but that the additives may represent a health threat. Additives are chemicals included in polymers to improve the microplastics' processing or performance, these can be or organic or inorganic nature. Besides being carriers of their inherent chemicals, microplastics could also be vectors for other toxic xenobiotics in the environment such as metalsor organic pollutants. Inevitably, microplastics from plastic debris will make their way to soil and agricultural systems, potentially into crops. More than 75 % of the plastic generated worldwide accumulates in the environment or in landfills. In 2015, that percentage represented ~23,595,855,840 kg of waste in the U.S. alone. Evidently, the presence of microplastics in the environment comes accompanied by an intrinsic release of their additives and a potential mobilization of other contaminants that could be carried along, becoming accessible to plants and other living organisms of a higher trophic level. The decomposition or changes in the microplastics' polymer networks (influenced by polymer type and environmental conditions) affect directly the delivery of additives. Despite current concerns about the effects of microplastics in terrestrial ecosystems, most research has been conducted in aqueous systems targeting specific marine organisms.The extensive use of plastic and its widespread distribution in the environment suggest contamination of agricultural systems with microplastics. Understanding the chemical structure of these soft materials and their ability to interact with co-existing pollutants is critical to assess and predict the toxicity and fate of microplastics additives in the environment
Animal Health Component
15%
Research Effort Categories
Basic
70%
Applied
15%
Developmental
15%
Goals / Objectives
ObjectivesThe aims of this project are to determine (1) the influence of microplastics' transformations over their additives in agricultural systems and (2) the phytotoxicity of a model plastic additive (PFBS) both in the presence and absence of a model co-contaminant (nCeO2).Objective 1. Investigate transformation processes on different microplastic types as a function of environmental aging/weathering. We will characterize the microplastics and measure the additives before and after aging. Under certain environmental conditions, we hypothesize that thermoplastics are more likely to release additives and contaminants than are thermosets. First, thermosets have more linkages in their molecular structure that may prevent leaching of their additives. Second, thermosets generally utilize additives in lesser amounts, therefore having less material to leach. Last, thermoplastics can be molecularly untangled by heat, leaving additives and retained contaminants exposed. Therefore, we expect that the polymer structure will change by the weathering exposure conditions, affecting directly the delivery of additives.Objective 2. Investigate the phytotoxicity and plant accumulation of a model plastic additive (PFBS) both in the presence and absence of a model co-contaminant (nCeO2). Our preliminary study showed that the toxicity of this plastic additive to plants could potentially be modulated by interactions with co-existing nanoceria. We hypothesize that if the analytes are present in more comparable amounts, nCeO2 may alleviate some of the phytotoxic effects of PFBS exposure.
Project Methods
Technical Approach to Objective 1. To investigate transformation processes of microplastics and their additives' release, we will evaluate two different polymer types (thermoplastics and thermosets) and age them artificially in soil-like media. The concentration will be 5 g of microplastic per 500 g of the matrix (PRO-MIX potting soil). Soil-like samples with the microplastic will be exposed to extreme regimes of light, temperature and moisture for the artificial aging process. The time points for analysis will be 0 h, 12 h, 24 h, 48 h, 7 d, 14 d and 30 d. We will look for changes in the soil-like organic matter composition, the microplastic physical/chemical polymer structure and the amount of additives present in the matrix after aging the microplastics. The microplastics' changes in structure will be analyzed by Attenuated Total Reflection Fourier Transform Infra-Red (ATR-FTIR) and electron microscopy. High resolution liquid chromatography (LC-HRMS) will be used to assess the additives within the plastic. The elemental composition of the potting mix will be determined by X-ray fluorescence (portable XRF), or by ICP-OES as required. The additives in the potting mix will be analyzed by LC-HRMS. The model thermoplastic will be polytetrafluoroethylene (PTFE, Teflon™ tape) and the model thermoset will be a polyurethane (PU) foam. The additives to be measured will be suspected PFASs from the tape and suspected PU processing aids such as amine catalysts. We will modify or develop LC-HRMS methods as needed for the analysis of additives and organic matter.Technical Approach to Objective 2. For phytotoxicity and plant accumulation assessment, we will expose radish to PFBS in the presence or absence of nCeO2 at similar concentrations (50-250 mg/kg of each chemical) in soil. Homogeneous mixtures of soil with the contaminant will be prepared by hand. Treatments will consist of 6 replicates with four plants in each pot. The experiment will be set in a greenhouse. Plants will be grown 4-6 weeks, until the control has harvestable radishes. At harvest, plants will be cleaned (rinsed in 0.01 M HNO3 followed by deionized water, DI H2O) and sectioned into roots, shoots and tuber. We will measure plant parameters such as germination, biomass, height, nutritional composition and ultrastructure by transmission electron microscopy. Samples for electron microscopy that are not prepared immediately will be cleaned at harvest and stored at -80 °C. We will evaluate if PFBS exhibits any phytotoxicity at this level and if nCeO2 influences the toxicity of PFBS. We will quantify PFBS levels in plants and soil using LC-HRMS, and if relevant, investigate PFBS phytotransformation products.