Fluxes of Gaseous Elemental Mercury on a Mediterranean Coastal Grassland

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.

Air Concentrations of Gaseous Elemental Mercury and Vegetation–Air Fluxes within Saltmarshes of the Tagus Estuary, Portugal

“…In ALC, ambient Hg(0) concentrations fluctuated from 1.18 to 3.53 ng m −3 , with a mean value of 1.80 ± 0.48 ng m −3 . These air Hg(0) concentrations were similar to those found in the St. François Bay wetland in Canada (0.88-4.89 ng m −3 ) [16], a Mediterranean coastal grassland in Greece (0.63-4.44 ng m −3 ) [53], and in a wetland in southern Florida, USA (1.73 ± 0.03 ng m −3 ) [54]. However, ALC air Hg(0) concentrations were higher than those found in back- In ALC, no statistical differences (p > 0.05) were observed in air Hg(0) concentrations measured near the different types of vegetation cover.…”

Characteristics of Mercury Fluxes between Soil and Air in the Farming-Pastoral Ecotone of Songnen Grassland

“…As can be seen in Table 2, the daily mean of the mercury exchange flux during the flowering stage of the L. chinensis land area was 5.5 ± 11.0 ng•m −2 •h −1 , while during the wilting stage, the daily mean was 5.8 ± 12.5 ng•m −2 •h −1 . The mercury exchange flux values in the anthesis of the L. chinensis were found to be lower than those in the wilting stage, which was speculated to be due to the decomposition of withered plants and plant litter in the ground cover of the sheep grasslands, with the mercury in the former being released into the soil, which was then released into the atmosphere [66]. This had resulted in the mercuryreleasing effects of the soil in the wilting stage of the L. chinensis being stronger than those in the anthesis.…”