For years microplastics have been regarded as a factor of global change due to its widespread presence and toxicity. Oceans and aquatic ecosystems are given plenty of attention to microplastic contamination, while in fact, microplastics within the aquatic phase are simply more obvious and easily visible, compared to soil, and not any less. Microplastics have been found in soils of a wide range of ecosystems and have been accumulating over the years because they have been persistent. The decomposition rate of microplastics in soil is not specifically determined as of current studies.
Studies have shown that microplastic adversely affects soil biota, and might change soil biophysical properties like soil aggregation, bulk density and water holding capacity. Microfibers have shown to increase root growth due to its ability to lower soil bulk density, leading to reduced penetration resistance for plant roots, and better soil aeration. However, negative effects are more. Plastic films create channels for water movement, resulting in increased water evaporation, which in turn can cause soil drying, and hence plant performance will have a negative impact.
Another aspect is regarding nanoparticles. As particle size decreases, effects on biota are not just physical. Instead it’s assumed to become more chemical and toxic. Unlike microsized particles, nanoplastic particles are taken up into the root. Current extraction and quantification methods either miss the existence of nanosized particles or don’t deliver any size information. However, nanoplastics are present within the environment, as microplastic particles fragment into smaller pieces. Damage caused by nanoparticles include alteration of the cell membrane, intracellular molecules, and generation of oxidative stress. But there is very little data for nanoplastic as of now. In cases of crops, this also means that these plastics may enter into the plant part that is used for human or livestock consumption, thus entering the food chain. Microbial communities in soil are also adversely affected due to the ability of microplastics to cause changes in soil structure, hence affecting mineralization rates, and communities of root-colonizing symbionts.
Plastic particles have a really high content of carbon, and most of this carbon usually is relatively inert, since the material does not readily decompose but it will eventually lead to microbial immobilization. Further studies are required to understand the effects of an individual plant to ecosystem level, as a function of ecosystem type, and degree and type of contamination. It is critically important to test for these effects, as plants are important players in the climate system too.
Reference: PubMed.gov
Author
