Soil Pollution from Micro- and Nanoplastic Debris: A Hidden and Unknown Biohazard

Abstract

The fate, properties and determination of microplastics (MPs) and nanoplastics (NPs) in soil are poorly known. In fact, most of the 300 million tons of plastics produced each year ends up in the environment and the soil acts as a log-term sink for these plastic debris. Therefore, the aim of this review is to discuss MP and NP pollution in soil as well as highlighting the knowledge gaps that are mainly related to the complexity of the soil ecosystem. The fate of MPs and NPs in soil is strongly determined by physical properties of plastics, whereas negligible effect is exerted by their chemical structures. The degradative processes of plastic, termed ageing, besides generating micro-and nano-size debris, can induce marked changes in their chemical and physical properties with relevant effects on their reactivity. Further, these processes could cause the release of toxic oligomeric and monomeric constituents from plastics, as well as toxic additives, which may enter in the food chain, representing a possible hazard to human health and potentially affecting the fauna and flora in the environment. In relation to their persistence in soil, the list of soil-inhabiting, plastic-eating bacteria, fungi and insect is increasing daily. One of the main ecological functions attributable to MPs is related to their function as vectors for microorganisms through the soil. However, the main ecological effect of NPs (limited to the fraction size < than 50 nm) is their capacity to pass through the membrane of both prokaryotic and eukaryotic cells. Soil biota, particularly earthworms and collembola, can be both MPs and NPs carriers through soil profile. The use of molecular techniques, especially omics approaches, can gain insights into the effects of MPs and NPs on composition and activity of microbial communities inhabiting the soil and into those living on MPs surface and in the gut of the soil plastic-ingesting fauna.

Sources of Light Density Microplastic Related to Two Agricultural Practices: The Use of Compost and Plastic Mulch

“…On the other scale side, most methods studying microplastics have the lower limit of detection around 20-30 µm [53]. The detection of smaller plastics' particles remains a challenge [54].…”

Marine Waste—Sources, Fate, Risks, Challenges and Research Needs

“…Microplastics are defined as plastic debris having particles with at least one dimension <5 mm, and particles <1 µm are known as nanoplastics [ 44 , 45 , 46 ]. Microplastics (MPs) and nanoplastics (NPs) have been recently detected in the atmosphere [ 47 , 48 ], freshwater and drinking water resources [ 28 , 49 , 50 ], wastewater and sewage sludge [ 51 ], soils and plants [ 52 , 53 , 54 , 55 ], marine ecosystems [ 17 , 45 ], in human and animal organisms [ 18 , 56 , 57 ], and even in the waters of the Arctic and the Antarctic [ 2 , 3 , 58 ].…”

Microplastics Increase Soil pH and Decrease Microbial Activities as a Function of Microplastic Shape, Polymer Type, and Exposure Time

“…In addition, the chemical properties of microplastics, such as molecular chain arrangement and functional group, could impact their capacity of absorption to other chemicals like heavy metals or antibiotics (Fred-Ahmadu et al, 2020), with potential consequences on soil properties and microbial activities (Pathan et al, 2020). For example, polyethylene (PE) had high sorption capacity for phenanthrene , which along with its nitrogen heterocyclic analogues could inhibit microbial activities in soil (Anyanwu and Semple 2016).…”