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Plasticulture - HYDAL POINT

Plasticulture

Plastics are everywhere – no surprise plastics are used even in agriculture – the fields are full of it – mulch foils, foil tunnels, irrigation systems. The end of life of these products is usually not taken into account. Many of these are never collected and growing amounts of plastics and microplastics in soil contribute to soil degradation and poor water retention.

Microplastics in soil

According to some estimates, soils carry 4–23 times more microplastics than oceans. However, sufficient quantitative data about microplastics is missing especially for soil ecosystems. The highest amount of microplastics were found close to roads in industry districts of Sydney – 7 weight percent. While Swiss protected forest areas contained only 0,0055 % of microplastics.1 Chinese studies report from 16 to 18760 microplastic particles in per kilogram of agricultural soil.2, 3

Sources of microplastics in soil

Plasticulture represents the main source of soil microplastics, but not the only one. Microplastics are brought also through water sources and air. Amounts of microplastics enter the soil also with sewage sludge used as fertilizer. 50 % of sewage sludge is distributed to fields. Controlled-release systems of agrochemicals can be sources of primary microplastics. In EU, it is estimated that 125–800 tons of microplastics per 1 million citizens enter the soil.4

Microplastics and soil microbiome

Fei and colleges observed loss of biodiversity in soil microbiome when 1–5 % microparticles of PE or 5 % of PVC was added.2 Their findings were confirmed in other studies.5, 6

Hydal
Fig. 1: Garden cress (Lepidium sativum). Microplastics in soil decreased germination ability of seeds. Micro- and nanoplastics accumulation in root hairs reduced root growth.

Additives

Plastics are mixtures of polymers and additives adjusting the material properties. It was shown that additives like triclosan and bisphenol A in microplastics impair viability and activity of organisms. 8, 9

References

1 Fojt, J., J. David, R. Přikryl, et al. A critical review of the overlooked challenge of determining micro-bioplastics in soil. Science of The Total Environment. 2020, 745: 140975. doi: https://doi.org/10.1016/j.scitotenv.2020.140975.

2 Fei, Y., S. Huang, H. Zhang, et al. Response of soil enzyme activities and bacterial communities to the accumulation of microplastics in an acid cropped soil. Science of The Total Environment. 2020, 707: 135634. doi: https://doi.org/10.1016/j.scitotenv.2019.135634.

3 Ding, L., S. Zhang, X. Wang, et al. The occurrence and distribution characteristics of microplastics in the agricultural soils of Shaanxi Province, in north-western China. Science of The Total Environment. 2020, 720: 137525. doi: https://doi.org/10.1016/j.scitotenv.2020.137525.

4 Nizzetto, L., M. Futter and S. Langaas. Are Agricultural Soils Dumps for Microplastics of Urban Origin? Environmental Science & Technology. 2016, 50(20): 10777-10779. doi: 10.1021/acs.est.6b04140.

5 Ren, X., J. Tang, X. Liu and Q. Liu. Effects of microplastics on greenhouse gas emissions and the microbial community in fertilized soil. Environmental Pollution. 2020, 256: 113347. doi: https://doi.org/10.1016/j.envpol.2019.113347.

6 Yan, Y., Z. Chen, F. Zhu, et al. Effect of Polyvinyl Chloride Microplastics on Bacterial Community and Nutrient Status in Two Agricultural Soils. Bulletin of Environmental Contamination and Toxicology. 2020. doi: 10.1007/s00128-020-02900-2.

7 Bosker, T., L. J. Bouwman, N. R. Brun, et al. Microplastics accumulate on pores in seed capsule and delay germination and root growth of the terrestrial vascular plant Lepidium sativum. Chemosphere. 2019, 226: 774-781. doi: https://doi.org/10.1016/j.chemosphere.2019.03.163.

8 Browne, Mark A., Stewart J. Niven, Tamara S. Galloway, et al. Microplastic Moves Pollutants and Additives to Worms, Reducing Functions Linked to Health and Biodiversity. Current Biology. 2013, 23(23): 2388-2392. doi: 10.1016/j.cub.2013.10.012.

9 Wei, W., Q.-S. Huang, J. Sun, et al. Polyvinyl Chloride Microplastics Affect Methane Production from the Anaerobic Digestion of Waste Activated Sludge through Leaching Toxic Bisphenol-A. Environmental Science & Technology. 2019, 53(5): 2509-2517. doi: 10.1021/acs.est.8b07069.