The addition of polypropylene microplastics promoted the formation of particulate organic carbon in urban green spaces

Abstract

The pollution of microplastics (MPs) in terrestrial ecosystems has drawn growing concern. Nevertheless, the influence of MPs on the fractions of soil organic carbon (SOC), particularly in urban soils, is still not well understood. Particulate organic carbon (POC) as a key component of urban soil organic carbon, is a core element for maintaining the functions of urban soil ecosystems. The effect of MPs on soil carbon dynamics was investigated by exposing soils planted with three common green plants to polypropylene microplastics (MPs) at concentrations of 0%, 0.5%, 1%, and 2% (w/w). The addition of MPs resulted in an 18.6% to 48.2% increase in SOC content. MPs notably boosted POC content by 44.2% to 101.7%, while they only increased mineral-associated organic carbon (MAOC) in soil without plants, with a range of 41.8% to 54.7%. There was a significant negative correlation between SOC and bacterial necromass carbon (BNC) in the absence of MPs, but this negative correlation disappeared with the addition of MPs. Compared with the BNC, the fungal necromass carbon (FNC) mainly contributed to the microbial necromass carbon (MNC) (about 74.6%). Bacterial communities were more sensitive to the addition of MPs than fungal communities. Structural equation model confirmed that MPs addition increases SOC content by promoting the accumulation of POC and BNC contribute to MAOC. Overall, the findings highlight the sensitive response of POC to MPs pollution, which could have a potential effect on soil carbon components in urban soil.

Graphical abstract

Keywords

microplastics / urban green space / soil carbon fraction / microbial necromass carbon

Highlight

	● MPs increased SOC content (18.6%–48.2%) by increasing POC.
	● MPs acting as a carbon source may cause the increase of POC.
	● BNC contribute to MAOC under MPs addition.
	● MPs addition changed the negative relationship between BNC and SOC.
	● Compared to BNC, FNC mainly contributed to MNC (about 74.6%).

References

[1] Andrady, A.L., Neal, M.A., 2009. Applications and societal benefits of plastics. Philosophical Transactions of the Royal Society B: Biological Sciences364, 1977–1984.

[2] Bayer, C., Mielniczuk, J., Martin-Neto, L., Ernani, P.R., 2002. Stocks and humification degree of organic matter fractions as affected by no-tillage on a subtropical soil. Plant and Soil238, 133–140.

[3] Browne, M.A., Crump, P., Niven, S.J., Teuten, E., Tonkin, A., Galloway, T., Thompson, R., 2011. Accumulation of microplastic on shorelines woldwide: sources and sinks. Environmental Science & Technology45, 9175–9179.

[4] Canedoli, C., Ferrè, C., El Khair, D.A., Padoa-Schioppa, E., Comolli, R., 2020. Soil organic carbon stock in different urban land uses: high stock evidence in urban parks. Urban Ecosystems23, 159–171.

[5] Cao, Y.X., Ma, X.Y., Chen, N., Chen, T.T., Zhao, M.J., Li, H.H., Song, Y.W., Zhou, J.C., Yang, J., 2023. Polypropylene microplastics affect the distribution and bioavailability of cadmium by changing soil components during soil aging. Journal of Hazardous Materials443, 130079.

[6] Chang, N., Chen, L., Wang, N., Cui, Q.L., Qiu, T.Y., Zhao, S.L., He, H.R., Zeng, Y., Dai, W., Duan, C.J., Fang, L.C., 2024. Unveiling the impacts of microplastic pollution on soil health: a comprehensive review. Science of the Total Environment951, 175643.

[7] Chen, J.G., Ji, C.J., Fang, J.Y., He, H.B., Zhu, B., 2020. Dynamics of microbial residues control the responses of mineral-associated soil organic carbon to N addition in two temperate forests. Science of the Total Environment748, 141318.

[8] Chen, M., Cao, M., Zhang, W., Chen, X., Liu, H.R., Ning, Z.Y., Peng, L.C., Fan, C.H., Wu, D.M., Zhang, M., Li, Q.F., 2024. Effect of biodegradable PBAT microplastics on the C and N accumulation of functional organic pools in tropical latosol. Environment International183, 108393.

[9] Chen, M., Cao, M., Zhang, W., Chen, X., Liu, H.R., Ning, Z.Y., Peng, L.C., Fan, C.H., Wu, D.M., Zhang, M., Li, Q.F., 2024. Effect of biodegradable PBAT microplastics on the C and N accumulation of functional organic pools in tropical latosol. Environment International183, 108393.

[10] Cotrufo, M.F., Ranalli, M.G., Haddix, M.L., Six, J., Lugato, E., 2019. Soil carbon storage informed by particulate and mineral-associated organic matter. Nature Geoscience12, 989–994.

[11] Craig, M.E., Turner, B.L., Liang, C., Clay, K., Johnson, D.J., Phillips, R.P., 2018. Tree mycorrhizal type predicts within-site variability in the storage and distribution of soil organic matter. Global Change Biology24, 3317–3330.

[12] de Souza Machado, A.A., Lau, C.W., Kloas, W., Bergmann, J., Bachelier, J.B., Faltin, E., Becker, R., Görlich, A.S., Rillig, M.C., 2019. Microplastics can change soil properties and affect plant performance. Environmental Science & Technology53, 6044–6052.

[13] de Souza Machado, A.A., Lau, C.W., Till, J., Kloas, W., Lehmann, A., Becker, R., Rillig, M.C., 2018. Impacts of microplastics on the soil biophysical environment. Environmental Science & Technology52, 9656–9665.

[14] Delgado-Baquerizo, M., García-Palacios, P., Bradford, M.A., Eldridge, D.J., Berdugo, M., Sáez-Sandino, T., Liu, Y.R., Alfaro, F., Abades, S., Bamigboye, A.R., Bastida, F., Blanco-Pastor, J.L., Duran, J., Gaitan, J.J., Illán, J.G., Grebenc, T., Makhalanyane, T.P., Jaiswal, D.K., Nahberger, T.U., Peñaloza-Bojacá, G.F., Rey, A., Rodríguez, A., Siebe, C., Teixido, A.L., Sun, W., Trivedi, P., Verma, J.P., Wang, L., Wang, J.Y., Yang, T.X., Zaady, E., Zhou, X.B., Zhou, X.Q., Plaza, C., 2023. Biogenic factors explain soil carbon in paired urban and natural ecosystems worldwide. Nature Climate Change13, 450–455.

[15] Diao, T.T., Liu, R.L., Meng, Q.Y., Sun, Y.B., 2023. Microplastics derived from polymer-coated fertilizer altered soil properties and bacterial community in a Cd-contaminated soil. Applied Soil Ecology183, 104694.

[16] Ding, Z.Q., Mou, Z.J., Li, Y.P., Liang, C., Xie, Z.C., Wang, J., Hui, D.F., Lambers, H., Sardans, J., Peñuelas, J., Xu, H., Liu, Z.F., 2024. Spatial variation and controls of soil microbial necromass carbon in a tropical montane rainforest. Science of the Total Environment921, 170986.

[17] Fei, Y.F., Huang, S.Y., Zhang, H.B., Tong, Y.Z., Wen, D.S., Xia, X.Y., Wang, H., Luo, Y.M., Barceló, D., 2020. Response of soil enzyme activities and bacterial communities to the accumulation of microplastics in an acid cropped soil. Science of the Total Environment707, 135634.

[18] Fuller, S., Gautam, A., 2016. A procedure for measuring microplastics using pressurized fluid extraction. Environmental Science & Technology50, 5774–5780.

[19] Galafassi, S., Nizzetto, L., Volta, P., 2019. Plastic sources: a survey across scientific and grey literature for their inventory and relative contribution to microplastics pollution in natural environments, with an emphasis on surface water. Science of the Total Environment693, 133499.

[20] Georgiou, K., Jackson, R.B., Vindušková, O., Abramoff, R.Z., Ahlström, A., Feng, W.T., Harden, J.W., Pellegrini, A.F.A., Polley, H.W., Soong, J.L., Riley, W.J., Torn, M.S., 2022. Global stocks and capacity of mineral-associated soil organic carbon. Nature Communications13, 3797.

[21] Guo, J.J., Huang, X.P., Xiang, L., Wang, Y.Z., Li, Y.W., Li, H., Cai, Q.Y., Mo, C.H., Wong, M.H., 2020. Source, migration and toxicology of microplastics in soil. Environment International137, 105263.

[22] Hartmann, N.B., Hueffer, T., Thompson, R.C., Hassellöv, M., Verschoor, A., Daugaard, A.E., Rist, S., Karlsson, T., Brennholt, N., Cole, M., Herrling, M.P., Hess, M.C., Ivleva, N.P., Lusher, A.L., Wagner, M., 2019. Are we speaking the same language? Recommendations for a definition and categorization framework for plastic debris. Environmental Science & Technology53, 1039–1047.

[23] Helmberger, M.S., Tiemann, L.K., Grieshop, M.J., 2020. Towards an ecology of soil microplastics. Functional Ecology34, 550–560.

[24] Hernandez, L.M., Xu, E.G., Larsson, H.C.E., Tahara, R., Maisuria, V.B., Tufenkji, N., 2019. Plastic teabags release billions of microparticles and nanoparticles into tea. Environmental Science & Technology53, 12300–12310.

[25] Huang, Y., Liu, Q., Jia, W.Q., Yan, C.R., Wang, J., 2020. Agricultural plastic mulching as a source of microplastics in the terrestrial environment. Environmental Pollution260, 114096.

[26] Huang, Y., Zhao, Y.R., Wang, J., Zhang, M.J., Jia, W.Q., Qin, X., 2019. LDPE microplastic films alter microbial community composition and enzymatic activities in soil. Environmental Pollution254, 112983.

[27] Kalčíková, G., Alič, B., Skalar, T., Bundschuh, M., Gotvajn, A.Ž., 2017. Wastewater treatment plant effluents as source of cosmetic polyethylene microbeads to freshwater. Chemosphere188, 25–31.

[28] Kim, S.W., Jeong, S.W., An, Y.J., 2021. Microplastics disrupt accurate soil organic carbon measurement based on chemical oxidation method. Chemosphere276, 130178.

[29] Lavallee, J.M., Soong, J.L., Cotrufo, M.F., 2020. Conceptualizing soil organic matter into particulate and mineral-associated forms to address global change in the 21st century. Global Change Biology26, 261–273.

[30] Li, S., Zhong, L.R., Zhang, B.W., Fan, C.Z., Gao, Y.Y., Wang, M.E., Xiao, H.N., Tang, X., 2024. Microplastics induced the differential responses of microbial-driven soil carbon and nitrogen cycles under warming. Journal of Hazardous Materials465, 133141.

[31] Liang, C., Amelung, W., Lehmann, J., Kästner, M., 2019. Quantitative assessment of microbial necromass contribution to soil organic matter. Global Change Biology25, 3578–3590.

[32] Liang, C., Schimel, J.P., Jastrow, J.D., 2017. The importance of anabolism in microbial control over soil carbon storage. Nature Microbiology2, 17105.

[33] Liu, H.F., Yang, X.M., Liu, G.B., Liang, C.T., Xue, S., Chen, H., Ritsema, C.J., Geissen, V., 2017. Response of soil dissolved organic matter to microplastic addition in Chinese loess soil. Chemosphere185, 907–917.

[34] Liu, Y.W., Zou, X.M., Chen, H.Y.H., Delgado-Baquerizo, M., Wang, C.T., Zhang, C., Ruan, H.H., 2023. Fungal necromass is reduced by intensive drought in subsoil but not in topsoil. Global Change Biology29, 7159–7172.

[35] Liu, Z.Q., Liu, Z.X., Wu, L.Z., Li, Y.Z., Wang, J., Wei, H., Zhang, J.E., 2022. Effect of polyethylene microplastics and acid rain on the agricultural soil ecosystem in Southern China. Environmental Pollution303, 119094.

[36] Martinez, C.E., Tabatabai, M.A., 1997. Decomposition of biotechnology by-products in soils. Journal of Environmental Quality26, 625–632.

[37] Mooshammer, M., Wanek, W., Hämmerle, I., Fuchslueger, L., Hofhansl, F., Knoltsch, A., Schnecker, J., Takriti, M., Watzka, M., Wild, B., Keiblinger, K.M., Zechmeister-Boltenstern, S., Richter, A., 2014. Adjustment of microbial nitrogen use efficiency to carbon: nitrogen imbalances regulates soil nitrogen cycling. Nature Communications5, 3694.

[38] Prăvălie, R., Nita, I.A., Patriche, C., Niculiță, M., Birsan, M.V., Roșca, B., Bandoc, G., 2021. Global changes in soil organic carbon and implications for land degradation neutrality and climate stability. Environmental Research201, 111580.

[39] Qian, Z.Y., Li, Y.N., Du, H., Wang, K.L., Li, D.J., 2023. Increasing plant species diversity enhances microbial necromass carbon content but does not alter its contribution to soil organic carbon pool in a subtropical forest. Soil Biology and Biochemistry187, 109183.

[40] Rillig, M.C., 2018. Microplastic disguising as soil carbon storage. Environmental Science & Technology52, 6079–6080.

[41] Steinmetz, Z., Wollmann, C., Schaefer, M., Buchmann, C., David, J., Tröger, J., Muñoz, K., Frör, O., Schaumann, G.E., 2016. Plastic mulching in agriculture. Trading short-term agronomic benefits for long-term soil degradation? Science of the Total Environment550, 690–705.

[42] Surendran, D., Varghese, G.K., Zafiu, C., 2024. Characterization and source apportionment of microplastics in Indian composts. Environmental Monitoring and Assessment196, 5.

[43] Vance, E.D., Brookes, P.C., Jenkinson, D.S., 1987. Microbial biomass measurements in forest soils: the use of the chloroform fumigation-incubation method in strongly acid soils. Soil Biology and Biochemistry19, 697–702.

[44] Wang, B.R., Huang, Y.M., Li, N., Yao, H.J., Yang, E., Soromotin, A.V., Kuzyakov, Y., Cheptsov, V., Yang, Y., An, S.S., 2022. Initial soil formation by biocrusts: nitrogen demand and clay protection control microbial necromass accrual and recycling. Soil Biology and Biochemistry167, 108607.

[45] Wang, J.C., Zou, Y.K., Di Gioia, D., Singh, B.K., Li, Q.F., 2020. Conversion to agroforestry and monoculture plantation is detrimental to the soil carbon and nitrogen cycles and microbial communities of a rainforest. Soil Biology and Biochemistry147, 107849.

[46] Wang, K., Liu, X.J., Chadwick, D.R., Yan, C.R., Reay, M., Ge, T.D., Ding, F., Wang, J.K., Qi, R.M., Xiao, M.L., Jiang, R., Chen, Y.L., Ma, J., Lloyd, C., Evershed, R.P., Luo, Y.M., Zhu, Y.G., Zhang, F.S., Jones, D.L., 2025a. The agricultural plastic paradox: feeding more, harming more. Environment International198, 109416.

[47] Wang, P.Y., Zhao, Z.Y., Xiong, X.B., Tao, H.Y., Guo, J.C., Hao, M., Ding, F., Ashraf, M., Fan, X.M., Yang, C.L., Irum, M., Cao, J., Wang, Y.B., Xiong, Y.C., 2025b. Microplastics boost soil multifunctionality via enhancing competitive Co-occurrence of bacterial communities in drylands. Land Degradation & Development1–15.

[48] Wei, J.N., Zhang, F.F., Ma, D.L., Zhang, J., Zheng, Y.L., Dong, H.P., Liang, X., Yin, G.Y., Han, P., Liu, M., Hou, L.J., 2023. Microbial necromass carbon in estuarine tidal wetlands of China: influencing factors and environmental implication. Science of the Total Environment876, 162566.

[49] Wright, S.L., Ulke, J., Font, A., Chan, K.L.A., Kelly, F.J., 2020. Atmospheric microplastic deposition in an urban environment and an evaluation of transport. Environment International136, 105411.

[50] Xiang, Y.Z., Rillig, M.C., Peñuelas, J., Sardans, J., Liu, Y., Yao, B., Li, Y., 2024. Global responses of soil carbon dynamics to microplastic exposure: a data synthesis of laboratory studies. Environmental Science & Technology58, 5821–5831.

[51] Xiao, M.L., Ding, J.N., Luo, Y., Zhang, H.Q., Yu, Y.X., Yao, H.Y., Zhu, Z.K., Chadwick, D.R., Jones, D., Chen, J.P., Ge, T.D., 2022. Microplastics shape microbial communities affecting soil organic matter decomposition in paddy soil. Journal of Hazardous Materials431, 128589.

[52] Ya, H.B., Xing, Y., Zhang, T., Lv, M.J., Jiang, B., 2022. LDPE microplastics affect soil microbial community and form a unique plastisphere on microplastics. Applied Soil Ecology180, 104623.

[53] Yuan, Y.D., Zu, M.T., Li, R.Z., Zuo, J.J., Tao, J., 2023. Soil properties, microbial diversity, and changes in the functionality of saline-alkali soil are driven by microplastics. Journal of Hazardous Materials446, 130712.

[54] Zambrano, M.C., Pawlak, J.J., Daystar, J., Ankeny, M., Cheng, J.J., Venditti, R.A., 2019. Microfibers generated from the laundering of cotton, rayon and polyester based fabrics and their aquatic biodegradation. Marine Pollution Bulletin142, 394–407.

[55] Zhang, G.H., Liu, D., Lin, J.J., Kumar, A., Jia, K.T., Tian, X.X., Yu, Z.G., Zhu, B., 2023. Priming effects induced by degradable microplastics in agricultural soils. Soil Biology and Biochemistry180, 109006.

[56] Zhang, H.X., Huang, Y.M., An, S.S., Wang, P., Xie, C.J., Jia, P.H., Huang, Q., Wang, B.R., 2024a. Mulch-derived microplastic aging promotes phthalate esters and alters organic carbon fraction content in grassland and farmland soils. Journal of Hazardous Materials461, 132619.

[57] Zhang, H.X., Huang, Y.M., Shen, J.K., Xu, F.J., Hou, H.Y., Xie, C.J., Wang, B.R., An, S.S., 2024b. Mechanism of polyethylene and biodegradable microplastic aging effects on soil organic carbon fractions in different land-use types. Science of the Total Environment912, 168961.

[58] Zhang, J.R., Ren, S.Y., Xu, W., Liang, C., Li, J.J., Zhang, H.Y., Li, Y.N., Liu, X.J., Jones, D.L., Chadwick, D.R., Zhang, F.S., Wang, K., 2022a. Effects of plastic residues and microplastics on soil ecosystems: a global meta-analysis. Journal of Hazardous Materials435, 129065.

[59] Zhang, M.Y., Liu, L.H., Xu, D.Y., Zhang, B.H., Li, J.J., Gao, B., 2022b. Small-sized microplastics (< 500 μm) in roadside soils of Beijing, China: accumulation, stability, and human exposure risk. Environmental Pollution304, 119121.

[60] Zhang, X.D., Amelung, W., 1996. Gas chromatographic determination of muramic acid, glucosamine, mannosamine, and galactosamine in soils. Soil Biology and Biochemistry28, 1201–1206.

RIGHTS & PERMISSIONS

Higher Education Press