Study on occurrence, estimation, and health risks of microplastics in outdoor sports venues in Chongqing

Outdoor artificial sports venues are emerging yet underestimated hotspots of urban microplastic (MP) pollution, with far-reaching ecological and human health implications, particularly in subtropical mountainous megacities. This study systematically investigated MP occurrence, emission characteristics, spatial patterns, and risks of MPs associated with plastic running tracks and artificial lawns in the main urban area of Chongqing. Rainwater runoff sampling and laboratory analyses revealed ubiquitous MP contamination across all venues. The average MP abundance in runoff from artificial lawns was 7.34 × 10 2 ± 3.72 × 10 2 particles L −1 (7.34 × 10 –1 ± 3.72 × 10 –1 particles g −1 ), which was slightly higher than that from plastic running tracks (6.52 × 10 2 ± 2.43 × 10 2 particles L −1 , 6.52 × 10 –1 ± 2.43 × 10 –1 particles g −1 ). Fibrous MPs dominated the samples collected from artificial lawns (75.23%), while fragments prevailed in plastic tracks (85.76%), with over 90% of particles being smaller than 0.5 mm. By integrating remote sensing, GIS spatial analysis, and localized emission factors adjusted for climate, usage intensity, and maintenance conditions, the total annual MP emissions from sports venues were estimated at 293.63 tons. Plastic running tracks contributed 224.09 tons, which was 3.2 times higher than those from artificial lawns (69.54 tons), corresponding to a per capita annual emission of 9.2 g. Although the MP concentration per litre in runoff from artificial turf was higher, plastic running tracks covered a substantially larger total area (3,525,781 m 2 compared with 2,606,282 m 2 for artificial turf). Consequently, the annual MP emission from plastic tracks exceeded that from artificial lawns. Spatial hotspots were concentrated within the inner ring, riverside zones, university towns, and Beibei District, and closely overlapped with densely populated and education-intensive areas. These findings provide a reference for MP management in urban outdoor sports facilities.