Fig. 1: Spatial distribution of mercury (Hg) concentration and isotopic composition in grass foliage, roots, and soil layers.

a Site location, b Hg concentration, c δ²⁰²Hg (‰), d Δ ¹⁹⁹Hg (‰), e Δ ²⁰⁰Hg (‰). The permafrost distribution in a is from the earlier study⁷⁶. The term Rsoil means rhizosphere soil, and Soil5 is 0−5 cm depth soil, and Soil12 is 5−12 cm depth soil, and Soil17 is 12−17 cm depth soil, and Soil > 25 is the soil more than 25 cm depth. Boxplot elements in b–e show the median (midline), the interquartile range of 25% and 75% percentile (box boundaries), data points within the 1.5 × quartile range (whiskers). The letter in b, e donates the statistical difference at the 95% confidence level.