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Plastic Pollution in the Terrestrial Environment
Mismanaged plastic waste leads to plastic directly or indirectly entering terrestrial environments. There has been a significant increase of microplastic pollution due to the poor handling and disposal of plastic materials.

Plastic pollution in the form of microplastics now can be found extensively in soil. It enters the soil by settling on the surface and eventually making its way into subsoils.

When plastics degrade, they break into smaller and smaller particles, eventually becoming so small they become absorbed by plants and animals.

Researchers say that fragmentation of plastic occurs because of UV radiation and heat on plastic at the surface of soil, becoming microplastics that then move into deeper levels of soil. This process also occurs in compost. Micro plastics are formed in compost from larger plastics breaking down. Degradation of plastic can occur by photodegradation (UV light), thermal oxidation, hydrolysis, and biodegradation. Plastic can break down into a micro plastic but these processes do not all degrade plastic by a significant amount.

Effluent and sludge of wastewater contain large amounts of plastics. Wastewater treatment plants don’t have a treatment process to remove microplastics which results in plastics being transferred into water and soil when effluent and sludge are applied to land for agricultural purposes. There are several types of plastics found in sludges and soils. The most common polymer types consist of Polyester, polypropylene, polyethylene. Polystyrene, Polyacrylonitrile ,Polyamide, Polyacrylate all also occur in smaller amounts.

Several researchers have found plastic microfibers that are released when fleece and other polyester textiles are cleaned in washing machines. Studies have extracted synthetic fibers from sludge, including “fibers, fragments, films, granules, and spheres. The percentage of fibers was higher than that of other shapes in all treatments”. These fibers can be transferred through effluent to land which pollutes soil environments.

The increase in plastic and microplastic pollution in soils can cause adverse impacts on plants and microorganisms in the soil, which can in turn affect soil fertility. Microplastics affect soil ecosystems that are important for plant growth. Plants are important for the environment and ecosystems so the plastics are damaging to plants and organisms living in these ecosystems.

Microplastics alter soil biophysical properties which affect the quality of the soil. This affects soil biological activity, biodiversity and plant health. Microplastics in the soil alter a plant’s growth. It decreases seedling germination, affects the number of leaves, stem diameter and chlorophyll content in these plants. Microplastics in the soil are a risk not only to soil biodiversity but also food safety and human health. Soil biodiversity is important for plant growth in agricultural industries.

Agricultural activities such as plastic mulching and application of municipal wastes contribute to the microplastic pollution in the soil. Human-modified soils are commonly used to improve crop productivity but the effects are more damaging than helpful.

Plastics also release toxic chemicals into the environment and cause physical, chemical harm and biological damage to organisms. Ingestion of plastic doesn’t only lead to death in animals through intestinal blockage but it can also travel up the food chain which affects humans.