Trends in soil mercury stock associated with pollution sources on a Mediterranean island (Majorca, Spain)

Highlights: • We analysed Hg soil spatial variability on the Majorca Island. • We found a high Hg concentration near the coal-fired power plant on Majorca. • We associate this effect with spatial patterns of Hg deposition on a local scale. • We found that most emitted Hg was deposited at distances less than 15 km. • We estimated that the Hg increase on the entire island in the last 11 years was 60 t. Hg is a global concern given its adverse effects on human health, food security and the environment, and it requiring actions to identify major local Hg sources and to evaluate pollution. Our study provides the first assessment of Hg stock trends on the entire Majorca surface, identifying major Hg sources by studying the spatiotemporal soil Hg variation at two successive times (2006 and 2016–17). The Hg soil concentration ranged from 14 to 258 μg kg⁻¹ (mean 52 μg kg⁻¹). Higher concentrations (over 100 μg kg⁻¹) were found in two areas: (i) close to the Alcudia coal-fired power plant; (ii) in the city of La Palma. During the 11-year, the total Hg stock in Majorcan soil increased from 432.96 tons to 493.18 tones (14% increase). Based on a block kriging analysis, soil Hg enrichment due to power plant emissions was clearly detectable on a local scale (i.e. a shorter distance than 18 km from the power plant). Nonetheless, a significant island-wide Hg increase due to diffuse pollution was reported. This result could be extrapolated to other popular tourist destinations in the Mediterranean islands where tourism has increased in recent decades In short, more than 60 tons of Hg have accumulated on Majorca island in 11 years.