"Acceptable limits" criteria of potentially toxic elements in ecological tea garden soil and priority control sources identification

Ecological tea gardens require the soil to be in an "uncontaminated" state, but the criteria for determining this status have not yet been clarified. With the increasing accumulation of potentially toxic elements (PTEs) in the soil, it is more important to emphasise that they meet "acceptable limits". Based on 318 tea garden soil samples from northern Fujian, China, this study reveals the content levels, pollution status, and specific source risks of PTEs using multivariate statistical techniques, evaluation models, and geospatial distribution analysis. The average contents of As, Cd, Cr, Hg, Pb, Cu, Ni, and Zn were 7.34, 0.078, 55.5, 0.086, 45.6, 23.0, 14.8, and 76.0 mg·kg^-1, respectively. The absolute principal component analysis-multiple linear regression model quantified three sources: natural sources (46 %), agricultural sources (25 %), and other mixed sources (29 %). Different sources contributed similarly to the comprehensive ecological risk. Considering only the total amounts of PTEs can lead to overestimation of the health risks, especially exaggerating the contribution of natural sources (approximately 45 %) to health risks. These elements can be considered to meet the "acceptable limits" status if they comply with the "Environmental Conditions for Tea Plantations" (NY/T 853-2004) or the comprehensive evaluation criteria (geo-accumulation index ≤ 3, potential ecological risk value ≤ 160, and within the acceptable range of health risks). The mixed-source risk of Cd, which had the highest probability of pollution (3.14 %), should be prioritised for control. These findings offer a new perspective on identifying PTEs pollution and prioritising control sources in ecological tea garden soils.