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Zhao Z, Zhao K, Zhang T, Xu Y, Chen R, Xue S, Liu M, Tang D, Yang X, Giessen V. Irrigation-facilitated low-density polyethylene microplastic vertical transport along soil profile: An empirical model developed by column experiment. Ecotoxicol Environ Saf 2022; 247:114232. [PMID: 36308877 DOI: 10.1016/j.ecoenv.2022.114232] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/26/2022] [Revised: 10/09/2022] [Accepted: 10/23/2022] [Indexed: 06/16/2023]
Abstract
The emerging issue of microplastic pollution of agricultural soils derives from the intensive utilization of plastic mulching film. Although surface runoff may transport microplastic off-site, infiltration may also facilitate microplastic transport from surface soil to deeper depths. Microplastic comprises a relatively new category of soil contaminants, whose transport in the soil has not yet been widely studied. In this study, we investigated microplastic transport from contaminated surface soil (50 g kg-1) driven by irrigation, from permanent wilting point to saturation, and developed an empirical model to characterize the resulting accumulation of microplastic along soil profile. A soil column experiment was conducted under various treatments: the control, 1, 2 and 4 runs of irrigation. Soil samples were collected from inside and outside of soil cracks (if present) in each soil layer (0-2 cm (source layer), 2-5 cm, 5-10 cm, 10-20 cm, 20-30 cm, 30-40 cm, 40-50 cm). The results showed that with increasing irrigation runs, microplastic in the source soil layer decreased, while microplastic contents in deeper soil depths increased significantly (p < 0.05), varying from 7.03 g kg-1 in 2-5 cm to 0.29 g kg-1 in 40-50 cm soil. The microplastic content detected in soil cracks was 1.3-17.8 times higher than that detected in the soil matrix at similar depths, indicating that the transported microplastic is prone to be enriched in soil cracks. In addition, the total amount of transported microplastic increased 1.5 times after four irrigation runs, and the variations were significantly observed especially at deeper soil depths. Based on correlation analyses, data-fitted empirical models that relate cumulative microplastic to the depth of soil layer and irrigation runs indicate that irrigation-facilitated microplastic transport could be well-characterized (R2 >0.92). Further research is needed to develop an physical-based model in order to assess microplastic migration risks driven by irrigation and other agricultural management practices.
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Affiliation(s)
- Zeyu Zhao
- College of Natural Resources and Environment, and State Key Laboratory of Soil Erosion and Dryland Farming, Northwest A&F University, Yangling 712100, China
| | - Keyue Zhao
- College of Natural Resources and Environment, and State Key Laboratory of Soil Erosion and Dryland Farming, Northwest A&F University, Yangling 712100, China
| | - Taishuo Zhang
- College of Natural Resources and Environment, and State Key Laboratory of Soil Erosion and Dryland Farming, Northwest A&F University, Yangling 712100, China
| | - Yiwen Xu
- College of Natural Resources and Environment, and State Key Laboratory of Soil Erosion and Dryland Farming, Northwest A&F University, Yangling 712100, China
| | - Ronglong Chen
- College of Natural Resources and Environment, and State Key Laboratory of Soil Erosion and Dryland Farming, Northwest A&F University, Yangling 712100, China
| | - Sha Xue
- State Key Laboratory of Soil Erosion and Dryland Farming, Institute of Soil and Water Conservation, Northwest A&F University, Yangling 712100, China
| | - Mengjuan Liu
- College of Agronomy, Northwest A&F University, Yangling 712100, China
| | - Darrell Tang
- Soil Physics and Land Management Group, Wageningen University & Research, 6700AA Wageningen, the Netherlands
| | - Xiaomei Yang
- College of Natural Resources and Environment, and State Key Laboratory of Soil Erosion and Dryland Farming, Northwest A&F University, Yangling 712100, China; State Key Laboratory of Soil Erosion and Dryland Farming, Institute of Soil and Water Conservation, Northwest A&F University, Yangling 712100, China; Soil Physics and Land Management Group, Wageningen University & Research, 6700AA Wageningen, the Netherlands.
| | - Violette Giessen
- Soil Physics and Land Management Group, Wageningen University & Research, 6700AA Wageningen, the Netherlands
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