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

Abstract

Microplastics (MPs) constitute a known, undesirable contaminant of the ecosystems. Land-based pollution is considered to be an important contributor, but microplastics in the terrestrial environment remains largely unquantified. Some agriculture practices, such as plastic mulch and compost application, are suspected to be major sources of microplastics as plastics are exposed to weathering or are present in organic fertilizers. The overall aim of this research is to bridge the terrestrial plastic contamination information gap, focusing on light density microplastics in two vegetable production systems in Southeast Spain and in the Netherlands. The selected farmer in Spain used plastic mulch for more than 12 years whereas the two farmers in the Netherlands annually applied 10 t ha−1 compost for the past 7 and 20 years. Samples from two different depths were collected: 0–10 cm and 10–30 cm. High quality compost samples originating from municipal organic waste and from garden and greenhouse waste were obtained from two Dutch compost plants. All samples from both Spanish (n = 29) and Dutch (n = 40) soils were contaminated by microplastics, containing 2242 ± 984 MPs kg−1 and 888 ± 500 MPs kg−1, respectively. Compost samples from municipal organic waste (n = 9) were more contaminated than the ones from garden and green house wastes (n = 19), with, respectively, 2800 ± 616 MPs kg−1 and 1253 ± 561 MPs kg−1. These results highlight the need for studies focusing on the effects of microplastics in the environment and the need for monitoring campaigns and the implementation of thresholds to regulate the microplastic contamination.

Spatial Distributions, Compositional Profiles, Potential Sources, and Intfluencing Factors of Microplastics in Soils from Different Agricultural Farmlands in China: A National Perspective

“…It was estimated that 4–23 times more MPs annually were released to the land than to the ocean and soil could become an important sink of MPs in the long term . As one of the closest environmental media to humans, the pollution of MPs in farmland is related to food safety and has caused global concern. − Due to different experimental methods, it is difficult to accurately compare the research results of MPs in farmland across China. − There have also been studies that collected farmland soil samples nationwide. Ren collected 69 soil samples from farmland with film mulching in 12 provinces to determine the occurrence of MP pollution and analyze the contribution of agricultural film to MPs in farmland.…”

“…Many studies have focused on factors influencing MPs to better control them in farmland, such as mulching age, , soil properties such as soil organic matter, and soil types. , However, individual macroscopic and practical factors affecting MPs in farmlands have not been studied comprehensively, such as plowing frequency and recovery methods. Besides, many studies have proposed potential sources to MPs in farmland, , which are important information to reduce MPs in agricultural (farm)­lands. However, quantifying their contributions is still unclear.…”

Microplastics persist in an arable soil but do not affect soil microbial biomass, enzyme activities, and crop yield

“…Tukey contrasts were computed using functions from the emmeans 1.5.0 package (Lenth, 2020). Particle size distributions of particles <0.5 mm were compared by plotting empirical cumulative density functions and using the Kolmogorov–Smirnov test ( ks.test ), to test whether the MP particles in MP start , M1, and M17, originated from the same distribution (van Schothorst et al., 2021). Empirical cumulative density functions were calculated based on pooled samples per treatment group ( n = 4).…”

Influence of Microplastics on Seedling Growth of Blackgram under Different Soil Types

“…In modern agriculture, polyethylene (PE) film is widely employed and thus forms a significant source of MPs in soil. The mulch films disintegrate into microplastics due to sunlight, water, chemical and biological degradation [3] and gradually accumulate in the field [4,5]. In addition to mulch film fragments, MPs might also reach soil through the application of compost [6,7], organic fertilisers [8,9], sewage sludge [10][11][12], and waste water irrigation [12,13].…”