Spatial Distribution and Biomonitoring of Atmospheric Mercury Concentrations over a Contaminated Coastal Lagoon (Northern Adriatic, Italy)

Federico Floreani,Nicolò Barago,Pablo Higueras,Nicola Skert,Stefano Covelli,Alessandro Acquavita

doi:10.3390/atmos11121280

Abstract

The Marano and Grado Lagoon (Northern Adriatic Sea) has been affected by mercury (Hg) contamination coming from two sources, mining activity and discharges from a chlor-alkali plant (CAP). Sediments and water contamination have been previously well characterised, but little is known about the atmospheric compartment, where Hg is easily emitted and can persist for a long time as gaseous elemental mercury (GEM). In this work, atmospheric GEM levels and its spatial distribution over the lagoon were monitored at several sites by means of both continuous discrete instrumental measurements over several months and the determination of Hg bioaccumulated in lichens (Xanthoria parietina L.). Average GEM levels varied from 1.80 ± 0.74 to 3.04 ± 0.66 ng m−3, whereas Hg in lichens ranged between 0.06 to 0.40 mg kg−1. In both cases, the highest values were found downwind of the CAP, but excluding this point, spatial patterns of Hg in the atmosphere and lichens reflected the concentration of this metal in the sediments of the lagoon, showing a decrease moving westward. These results could indicate that the lagoon acts as a secondary source of Hg into the atmosphere: future work is needed to characterise the quantity of releases and depositions at different environments inside the lagoon.

Highlights

Mercury (Hg) is a persistent pollutant of global concern due to its significant negative impact on both human and environmental health [1,2]
Gaseous elemental mercury (GEM) atmospheric levels and spatial distribution over the Marano and Grado Lagoon were monitored through direct instrumental measurements and lichen surveys, completing the recently published assessment of the occurrence of this contaminant in the area of the Gulf of Trieste [54]
The highest gaseous elemental mercury (GEM) levels in the atmosphere and Hg concentrations in lichens were recorded at the site located downwind of the chlor-alkali plant (CAP), confirming that contaminated factory buildings still represent a source of atmospheric Hg

Summary

Introduction

Mercury (Hg) is a persistent pollutant of global concern due to its significant negative impact on both human and environmental health [1,2]. Atmospheric Hg mainly consists of its elemental form, often denoted as Gaseous Elemental Mercury (GEM), which thanks to its high volatility and chemical inertness can persist in the atmosphere for 0.8 to 1.3 years [7] and can be subjected to long-range transport before being removed via depositions [8]. In this way, Hg can have an impact on remote ecosystems far from the point of emission [9,10,11]. The results of this study will be an added value to the knowledge of GEM distribution in the entire area of the Gulf of Trieste [54]

Study Area

GEM Level and Distribution

Boxplots

Scatterplot between

Conclusions