College of Land Science and Technology, China Agricultural University, Beijing, 100193, China.
College of Resources and Environmental Sciences, China Agricultural University, Beijing, 100193, China.
J Environ Manage. 2022 Sep 1;317:115473. doi: 10.1016/j.jenvman.2022.115473. Epub 2022 Jun 6.
Plastic mulch is frequently used to increase crop yield, resulting in large quantities of residues accumulating in soil due to low recovery rates. However, the effects of microplastic residues from traditional and biodegradable plastic films on soil nitrogen (N) transformation and bioavailability are not well understood. Here, the main objectives were to examine the effects of micro-sized residues (diameter <5 mm) of polyethylene (PE) and biodegradable plastic mulch films (PLA) on the soil N in two contrasting soils (clay soil and sandy loam soil) in different temperatures (15 °C vs. 25 °C). Results showed that the microplastic presence showed a little effect on soil N transformation and bioavailability at 15 °C, but both microplastics significantly decreased NO, mineral N (MN), total dissolved N (TDN), the net cumulative N nitrification (Nn), and the net cumulative N mineralization (Nm) at 25 °C, indicating that microplastics decreased soil N bioavailability at elevated temperature. Meanwhile, the microplastics significantly reduced the temperature sensitivity (Q) of N mineralization. The presence of microplastics changed the composition of soil mineral N with lower relative NO and higher NH compared to the control in clay soil. The sandy loam soil was more susceptible to microplastic pollution compared to clay soil in N transformation, due to different textures and biochemistry properties in the two soils, which showed that microplastics have a significant soil heterogeneity-dependent effect on soil N processes. Therefore, the results underline that the effects of microplastic residues on soil N cycling can be partly linked to soil properties, suggesting the urgent need for further studies examining their impacts on soil nutrient cycling in different soil systems.
塑料地膜常用于提高作物产量，由于回收率低，大量残留在土壤中。然而，传统和可生物降解塑料薄膜的微塑料残留对土壤氮（N）转化和生物有效性的影响还不太清楚。本研究的主要目的是研究在两种不同温度（15°C 与 25°C）下，聚乙烯（PE）和可生物降解塑料地膜的微塑料（直径<5mm）残体对两种不同土壤（粘土和砂壤土）中土壤 N 的影响。结果表明，在 15°C 时，微塑料的存在对土壤 N 转化和生物有效性几乎没有影响，但在 25°C 时，两种微塑料都显著降低了 NO、矿质 N（MN）、总溶解 N（TDN）、净累积硝化 N（Nn）和净累积矿化 N（Nm），表明微塑料在高温下降低了土壤 N 的生物有效性。同时，微塑料显著降低了矿化 N 的温度敏感性（Q）。与对照相比，微塑料的存在降低了粘土土壤中矿质 N 的组成，使相对 NO 降低，NH 升高。与粘土土壤相比，砂壤土在 N 转化方面更容易受到微塑料污染的影响，这是由于两种土壤的质地和生物化学性质不同，这表明微塑料对土壤 N 过程具有显著的土壤异质性依赖性影响。因此，研究结果强调了微塑料残留对土壤氮循环的影响可能与土壤特性有关，这表明迫切需要进一步研究其对不同土壤系统中土壤养分循环的影响。
