Total mercury and methylmercury in high altitude surface snow from the French Alps

► THg, MeHg and particle concentrations increase throughout the season. ► MeHg and THg are positively correlated. MeHg and total PM10 also. ► MeHg found in the snow can be originated from atmospheric deposition process. ► MeHg production in situ by biological processes, into the snowpacks is unclear.