Abstract
Coastal rural areas can be a source of elemental mercury, but the potential influence of their topographic and climatic particularities on gaseous elemental mercury (GEM) fluxes have not been investigated extensively. In this study, gaseous elemental mercury was measured over Mediterranean coastal grassland located in Northern Greece from 2014 to 2015 and GEM fluxes were evaluated utilizing Monin–Obukhov similarity theory. The GEM fluxes ranged from –50.30 to 109.69 ng m−2 h−1 with a mean value equal to 10.50 ± 19.14 ng m−2 h−1. Concerning the peak events, with high positive and low negative GEM fluxes, those were recorded from the morning until the evening. Rain events were a strong contributing factor for enhanced GEM fluxes. The enhanced turbulent mixing under daytime unstable conditions led to greater evasion and positive GEM fluxes, while, during nighttime periods, the GEM evasion is lower, indicating the effect of atmospheric stability on GEM fluxes. The coastal grassland with its specific characteristics influences the GEM fluxes and this area could be characterized as a source of elemental mercury. This study is one of the rare efforts in the research community to estimate GEM fluxes in a coastal natural site based on aerodynamic gradient method.
Highlights
It has been recognized that the determination of gaseous elemental mercury (GEM) fluxes is a crucial factor to better describe the biogeochemical cycle of mercury [1,2,3]
Gaseous elemental mercury (GEM) concentrations were measured in a coastal area that is surrounded by grassland, in northeastern Greece from August to November 2014 and January 2015
The GEM concentrations at three different heights in a micrometeorological tower were handled in order to calculate GEM fluxes based on the aerodynamic gradient method
Summary
It has been recognized that the determination of gaseous elemental mercury (GEM) fluxes is a crucial factor to better describe the biogeochemical cycle of mercury [1,2,3]. The atmosphere is the main reservoir of the mercury, where chemical processes alter the form mercury via different transformation pathways and influence the characteristics of transport and deposition [4]. Atmospheric mercury is emitted from both natural and anthropogenic sources [5] and exists mainly in the gaseous elemental form (>95%), where the level of its concentration in the boundary layer corresponds to few ng m−3 and its residence time spans from six months to two years [6]. The methods that are used in order to estimate the air-sea and air-land total gaseous mercury (TGM) fluxes are grouped into enclosure and micrometeorological methods [8]. The micrometeorological (MM) methods include relaxed eddy accumulation (REA) and the flux gradient methods according to
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