The macroplastics (MaPs) and microplastics (MiPs) polluting agricultural soils raise great concerns. Unfortunately, scientists know little about the occurrence of MaPs/MiPs in soil among different farming systems. In this study, we analyzed MaPs/MiPs in soils (0‒30 cm) collected from six different farming systems (wheat-maize rotations, cotton, vegetables, permanent orchards, greenhouses with and without mulching) in Quzhou county, the North China Plain, by using fluorescence microscope and micro-Fourier transform infrared spectroscopy. The results showed that the abundance of MaPs and MiPs ranged from 0.2 to 46.8 kg ha^‒1, and 4.1×10³‒3.7×10⁴ items kg^‒1, respectively. The prominent colors of the MaPs were white and black. The predominant shape, size and chemical composition of soil MiPs were fragments (45‒62%), < 1 mm (98‒99%), and polyethylene (38‒43%), respectively. MaPs were mainly detected in the 0‒10 cm soil layer. MiP abundance in the 0‒10 cm soil layer was significantly higher than that in the 20‒30 cm soil layers among different farming systems, except for the fields with wheat-maize rotations and permanent orchards (p < 0.05). Overall, cotton fields showed the highest MaP and MiP abundance, followed by vegetable fields and orchards. Redundancy analysis revealed that tillage practices and plastic film management greatly influence the size distribution of MiPs. A strong negative correlation between large-sized plastic fractions (0.2‒1 mm) and tillage frequency was tested while the years of application of plastic films and the abundance of plastic residues showed a strong positive correlation with small-sized plastic fractions (< 0.2 mm). Our findings conclude that agricultural mulch films are an important source of MaPs and MiPs in agricultural soil and distributions are strongly influenced by agricultural management practices and farming systems. Further studies should take farming systems and farming practices into account, thereby exploring the potential mechanisms of plastic fragmentation and granularization in agricultural soil.

中文翻译：

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不同集约化耕作系统下土壤中宏观和微观塑料积累——以华北平原衢州县为例


污染农业土壤的大塑料 （MaP） 和微塑料 （MiP） 引起了极大的关注。不幸的是，科学家们对不同耕作系统之间土壤中 MaPs/MiP 的出现知之甚少。本研究采用荧光显微镜和微傅里叶变换红外光谱分析了华北平原衢州县 6 种不同耕作系统（小麦-玉米轮作、棉花、蔬菜、永久果园、有和无覆盖温室）采集的土壤 （0\u201230 cm） 中的 MaPs/MiPs。结果表明，MaPs 和 MiPs 的丰度分别为 0.2 至 46.8 kg ^hm21 和 4.1×0³\u20123.7×10⁴ 项 kg^\u20121。MaP 的突出颜色是白色和黑色。土壤 MiP 的主要形状、大小和化学成分分别为碎片 （45\u201262%）、< 1 mm （98\u201299%） 和聚乙烯 （38\u201243%）。MaPs 主要在 0\u201210 cm 土层中检测到。除小麦-玉米轮作田和永久性果园外，不同耕作系统0\u201210 cm土层的MiP丰度显著高于20\u201230 cm土层（p < 0.05）。总体而言，棉田的 MaP 和 MiP 丰度最高，其次是菜田和果园。冗余分析表明，耕作实践和塑料薄膜管理极大地影响了 MiP 的大小分布。测试了大尺寸塑料部分 （0.2\u20121 mm） 与耕作频率之间的强负相关，而塑料薄膜的应用年限和塑料残留物的丰度与小尺寸塑料部分 （< 0.2 mm） 呈强正相关。 我们的研究结果得出结论，农业地膜是农业土壤中 MaPs 和 MiPs 的重要来源，其分布受农业管理实践和耕作系统的强烈影响。进一步的研究应考虑农业系统和耕作方式，从而探索农业土壤中塑料碎片化和颗粒化的潜在机制。