Microplastic pollution in organic farming development cannot be ignored in China: Perspective of commercial organic fertilizer

Commercial organic fertilizer, an essential fertilizer for developing organic farming in China, has been identified as a potentially important source of microplastics (MPs) on farmland. However, little is known about the occurrence of MPs in commercial organic fertilizers and their potential ecological risks nationwide. Here, stereoscopy and laser-infrared imaging spectrometry were used to comprehensively investigate the abundance, size, type and morphology of MPs in commercial organic fertilizers collected from mainland China, assess the ecological risks, and predict MP contamination. Commercial organic fertilizers contained many MPs (8.88 ×103 to 2.88 ×105 items/kg), especially rich in small-size MPs (<100 µm), accounting for 76.53%. The highest MP pollution load value was observed in fertilizers collected from East China. Chlorinated polyethylene, polyurethane, polyethylene and polypropylene were the dominant MPs with the shape of film and fragment, concentrated in small sizes (<100 µm). The risk index (H-index) of the MPs was used to quantify the ecological risk of the MPs in the different samples, and most of the fertilizers were at level Ⅲ with high risk. Predictably, 2.32 × 1013 - 2.81 × 1016 MPs will accumulate in orchard soils after five years of fertilization, especially in South, Southwest and East China. This study provides primary scientific data on MP pollution in commercial fertilizer and the health development of organic farming.