Physiological and climate controls on foliar mercury uptake by European tree species

Abstract. Despite the importance of vegetation uptake atmospheric gaseous elemental mercury (Hg(0)) within global Hg cycle, little knowledge exists on physiological, climatic, and geographic factors controlling stomatal Hg(0) by tree foliage. We investigate controls foliar combining measurements 3569 foliage samples across Europe with data species' traits environmental conditions. To account for accumulation over time, we normalized concentration life period from simulated start growing season to sample harvest. The most relevant parameter impacting daily was functional group (deciduous versus coniferous trees). On average, measured 3.2 times higher rates in deciduous leaves than needles same age. Across species, beech fir, at two out three forest plots more 20 samples, found a significant (p<0.001) increase values respective leaf nitrogen concentrations. therefore suggest that is controlled increasing low high nutrient content representing physiological activity. For pine spruce needles, detected linear decrease proportion time during which water vapor pressure deficit (VPD) exceeded species-specific threshold 1.2 3 kPa, respectively. surface soil (ERA5-Land) region correlated negatively pine. These findings inhibited under VPD conditions and/or due regulation conductance reduce loss dry Other parameters associated sampling sites (latitude altitude), sampled trees (average age diameter breast height), or regional satellite-observation-based transpiration product (Global Land Evaporation Amsterdam Model: GLEAM) did not significantly correlate rates. conclude activity response should be implemented model assess future cycling different anthropogenic emission scenarios warming.