Spatial and temporal variations of soil heavy metal pollution in Chinese facility agricultural land in the past 20 years

Facility agricultural land, as the cornerstone of modern agriculture, has garnered limited attention regarding the extent and spatiotemporal distribution of soil heavy metal pollution. Therefore, based on 678 research papers from 2004 to 2023, we firstly conducted a meta-analysis to evaluate the pollution levels of As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn. Secondly, we used the geo-accumulation index and potential ecological risk index to assess the risk level of soil heavy metal pollution. Then, SHapley Additive exPlanations analysis was applied to reveal the impact of soil properties on soil heavy metals. Finally, we proposed pollution remediation and improvement strategies. The results showed that (1) the average contents of eight heavy metals As, Cd, Cr, Cu, Hg, Ni, Pb, and Zn in Chinese facility agricultural land were 11.04 mg/kg, 0.85 mg/kg, 45.78 mg/kg, 54.13 mg/kg, 2.47 mg/kg, 26.07 mg/kg, 29.63 mg/kg and 142.33 mg/kg, respectively. Among them, Cd, Cu, Zn, and Hg had high accumulation levels, exceeding twice their background values. (2) Soil heavy metal pollution on Chinese facility agricultural land exhibited a spatial pattern of higher levels in the eastern and southern regions and lower levels in the western and northern regions. (3) Cu, Ni, and Zn reached high pollution levels, with elevated ecological risk areas were concentrated in South and Northwest China. (4) Soil pH and soil organic carbon exerted significant influences on the accumulation of most soil heavy metals. Our study provides a scientific basis for soil management, soil pollution remediation and control in China. • Meta-analysis was applied to assess soil heavy metal pollution in Chinese facility agricultural land over the past two decades. • Cd, Cu, Zn, and Hg had high average contents, which were twice as high as the background values. • Soil heavy metal pollution in Chinese facility agricultural land had obvious spatial heterogeneity. • Cu, Ni, and Zn had high geo-accumulation index values, and the ecological risk was higher in southern China than other regions. • Soil pH and soil organic carbon had a greater influence on soil heavy metal accumulation.