Short-term evaluation for estimating soil arsenic contamination using Pinus densiflora needles with phosphorus as a supplementary indicator

Abandoned mines release arsenic (As), which poses severe environmental and health risks through soil–plant–human exposure pathways. This study evaluated the potential use of Pinus densiflora for estimating soil As contamination and assessed whether phosphorus (P) concentration in needles could serve as a supplementary indicator. Soil samples with 33.71–3017.02 mg kg⁻¹ As concentrations and 4.90–8.55 pH were collected upstream and downstream of a mine waste dam, and first-year pine seedlings were cultivated for six months. The As accumulation patterns in 1- and 2-year-old needles were analyzed, and their relationships with soil As fractions, including total As, Olsen-extractable As, and fraction 1 + 2 of Wenzel extraction, were examined. Among the soil As fractions, Olsen-extractable As showed the strongest correlation with needle As concentrations, particularly in 2-year-old needles (r = 0.872, p < 0.001). A multiple regression model including P in 2-year-old needles to predict Olsen-extractable As, in addition to As concentration in 2-year-old needles, improved the model's explanatory power (R²) from 0.761 to 0.828 and decreased the Akaike information criterion (AIC) from 119.88 to 115.95, indicating enhanced model fitness. These findings demonstrate the potential of P. densiflora needles for soil As contamination assessment, with P serving as a valuable supplementary indicator.