Abstract
Abstract. Microplastic and microglass particles from different sources enter aquatic and terrestrial environments. The complexity of their environmental impact is difficult to capture, and the consequences for ecosystem components, for example, the soil microorganisms, are virtually unknown. To address this issue, we performed an incubation experiment by adding 1 % of five different types of impurities (≤100 µm) to an agriculturally used soil (Chernozem) and simulating a worst-case scenario of contamination. The impurities were made of polypropylene (PP), low-density polyethylene (LDPE), polystyrene (PS), polyamide 12 (PA12) and microglass. After 80 d of incubation at 20 ∘C, we examined the soil microbial community structure by using phospholipid fatty acids (PLFAs) as markers for bacteria, fungi and protozoa. The results showed that soil microorganisms were not significantly affected by the presence of microplastic and microglass. However, PLFAs tend to increase with LDPE (28 %), PP (19 %) and microglass (11 %) in treated soil in comparison with untreated soil, whereas PLFAs in PA12 (32 %) and PS (11 %) in treated soil decreased. Interestingly, PLFAs revealed significant differences in PA12 (−89 %) and PS (−43 %) in comparison with LDPE. Furthermore, variability of bacterial PLFAs was much higher after microplastic incubation, while fungi seemed to be unaffected from different impurities after 80 d of incubation. Similar results were shown for protozoa, which were also more or less unaffected by microplastic treatment as indicated by the minor reduction in PLFA contents compared to the control group. In contrast, microglass seems to have an inhibiting effect on protozoa because PLFAs were under the limit of determination. Our study indicated that high amounts of different microplastics may have contrary effects on soil microbiology. Microglass might have a toxic effect for protozoa.
Highlights
Microplastics are used, for example, for a range of consumer products or in industrial application such as abrasives, filler, film and binding agents
The Scanning electron microscopy (SEM) images of the microplastics (PP, low-density polyethylene (LDPE), PS and polyamide 12 (PA12)) and microglass are shown in Fig. 1, illustrating the heterogenic morphology between, and within, the same type of microplastic
The observed effects are based on complex soil– impurity interactions, and studies dealing with the impact of microplastics on soil microbiology are still lacking (Rillig and Bonkowski, 2018; Zhang et al, 2019) and, to our best knowledge, published phospholipid fatty acids (PLFAs) or even deoxyribonucleic acid (DNA)-based studies are still missing
Summary
Microplastics are used, for example, for a range of consumer products or in industrial application such as abrasives, filler, film and binding agents. The identification and quantification of the sources and pathways of microplastics into the environment are highly diverse and difficult to detect. While different methods have been developed for synthetic polymer identification and quantification in sediments and water, analytical methods for soil matrices are still lacking or in an early experimental stage (e.g., Hurley et al, 2018). It is assumed that microplastics enter (agricultural) soils with soil amendments, irrigation and the use of agricultural plastic films for mulch applications and through flooding, atmospheric deposition and littering (Bläsing and Amelung, 2018; Hurley and Nizzetto, 2018; Kyrikou and Briassoulis, 2007; Ng et al, 2018; Weithmann et al, 2018). A recent study by Weithmann et al (2018) found 895 plastic particles (>1 mm) per kilogram of dry weight in digestate from a biowaste digester used as soil fertilizer after aerobic com-
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