Key Takeaways & Executive Findings
- •• • Biochar application at 126.00 t·hm−2 significantly increased soil porosity and available nitrogen, phosphorus, and potassium, while reducing bulk density, enhancing soil fertility in aeolian sandy soils. • • Microplastic abundance in the 0–30 cm soil layer averaged 3459.57 pieces·kg−1, with the highest at 126.00 t·hm−2 biochar, indicating a dose-dependent accumulation effect. • • In the 30–60 cm layer, microplastic abundance averaged 3163.50 pieces·kg−1, peaking at 63.00 t·hm−2 biochar, suggesting depth-dependent transport and retention. • • Biochar application did not alter microplastic morphology; transparent, film-shaped, 0–0.5 mm particles dominated, implying biochar may facilitate microplastic retention without changing their physical characteristics.
Abstract
This study investigated the long-term effects of biochar application on physicochemical properties and microplastic accumulation in aeolian sandy soils, based on a field experiment established in 2014. After seven years of mulched cultivation, soil samples were collected from 0–30 cm and 30–60 cm depths. Biochar application significantly increased soil porosity and available nitrogen, phosphorus, and potassium contents, while reducing bulk density. At a biochar rate of 126.00 t·hm−2, soil water content was significantly reduced. Microplastic abundance averaged 3459.57 pieces·kg−1 in the 0–30 cm layer, with the highest abundance at 126.00 t·hm−2; in the 30–60 cm layer, average abundance was 3163.50 pieces·kg−1, with the highest at 63.00 t·hm−2. Microplastics were predominantly transparent, film-shaped, and 0–0.5 mm in size. The results indicate that biochar application significantly increased microplastic abundance in aeolian sandy soils, providing insights into microplastic adsorption and enrichment in agricultural ecosystems. Further research is needed to elucidate underlying mechanisms.
1. Introduction
Biochar has been widely promoted as a soil amendment to improve fertility and carbon sequestration in degraded soils. However, its long-term impact on microplastic accumulation in agricultural soils remains poorly understood, particularly in arid regions where plastic mulch is extensively used. Existing studies have focused on short-term effects or laboratory conditions, leaving a critical gap in field-scale, multi-year assessments. This study addresses this bottleneck by leveraging a long-term field trial established in 2014, providing robust data on biochar's influence on soil physicochemical properties and microplastic dynamics over seven years.
The experimental protocol systematically evaluates biochar application rates (0, 31.50, 63.00, and 126.00 t·hm−2) on aeolian sandy soil, a representative soil type in arid regions. By analyzing soil layers at 0–30 cm and 30–60 cm, the study captures both surface and subsurface effects, offering insights into microplastic vertical transport. The findings are critical for developing sustainable biochar management strategies that mitigate microplastic pollution while enhancing soil health, addressing a pressing environmental concern in intensive agriculture.
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ZHANG Yi, SUN Xia, YAN Han, KOU Tianle, YANG Zailei, TANG Guangmu, XU Wanli, JIA Hongtao (2026). Long-term Effects of Biochar Application on Physicochemical Properties and Microplastic Accumulation in Aeolian Sandy Soils. Environmental Chemistry. https://doi.org/10.7524/j.issn.0254-6108.2025010701
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Frequently Asked Questions
What is the optimal biochar application rate to maximize soil fertility without exacerbating microplastic accumulation?
The study found that biochar application at 126.00 t·hm−2 significantly increased soil nutrients and porosity, but also led to the highest microplastic abundance in the 0–30 cm layer (3459.57 pieces·kg−1). In contrast, the 63.00 t·hm−2 rate resulted in the highest microplastic abundance in the 30–60 cm layer (3163.50 pieces·kg−1). Therefore, a balanced rate, possibly around 63.00 t·hm−2, may be considered to minimize surface microplastic accumulation while still improving soil properties, though further cost-benefit analysis is needed.
How does biochar application influence the vertical transport of microplastics in aeolian sandy soils?
Biochar application altered microplastic distribution between soil layers. At 126.00 t·hm−2, microplastics were more concentrated in the top 0–30 cm, while at 63.00 t·hm−2, they were more abundant in the 30–60 cm layer. This suggests that biochar may affect soil porosity and water movement, potentially facilitating or hindering microplastic migration. The exact mechanisms require further investigation, but the data indicate depth-dependent effects.
What are the dominant characteristics of microplastics in biochar-amended aeolian sandy soils?
Microplastics were predominantly transparent, film-shaped, and 0–0.5 mm in size, regardless of biochar application. This indicates that biochar does not alter the physical form of microplastics but may enhance their retention in soil, as evidenced by increased abundance. The prevalence of film-shaped microplastics suggests a source from plastic mulch degradation.
Does biochar application significantly affect soil water content, and what are the implications for irrigation management?
Yes, at the highest application rate of 126.00 t·hm−2, soil water content was significantly reduced. This could be due to increased porosity and drainage, which may require adjusted irrigation schedules to maintain optimal moisture for crops. Lower rates (31.50 and 63.00 t·hm−2) did not significantly alter water content, suggesting a threshold effect.
What are the long-term implications of biochar-induced microplastic accumulation for soil health and food safety?
The study shows that biochar application can increase microplastic abundance in soil, which may pose risks to soil biota and potentially enter the food chain. However, the long-term effects on soil health and crop quality are not yet fully understood. Future research should focus on the bioavailability of microplastics and their interactions with soil contaminants, as well as strategies to mitigate accumulation while retaining biochar's benefits.
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