Critical Observations of Gaseous Elemental Mercury Air-Sea Exchange
| Autor: | Anna Rutgersson, Kevin Bishop, Stefan Osterwalder, Anne L. Soerensen, Erik Nilsson, Ingvar Wängberg, Jonas Sommar, Martin Jiskra, Mats Nilsson, Wei Zhu, Michelle Nerentorp, Marcus B. Wallin |
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| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Atmospheric Science
010504 meteorology & atmospheric sciences Physics::Instrumentation and Detectors Oceanography Hydrology Water Resources 010501 environmental sciences Atmospheric sciences 01 natural sciences Wind speed Atmosphere Flux (metallurgy) Open sea Environmental Chemistry 14. Life underwater Physics::Atmospheric and Oceanic Physics 0105 earth and related environmental sciences General Environmental Science Global and Planetary Change Transfer velocity Supersaturation Elemental mercury Condensed Matter::Mesoscopic Systems and Quantum Hall Effect 13. Climate action Meteorology and Atmospheric Sciences Physics::Space Physics Environmental science Astrophysics::Earth and Planetary Astrophysics Exchange model |
| Popis: | Air-sea exchange of gaseous elemental mercury (Hg-0) is not well constrained, even though it is a major component of the global Hg cycle. Lack of Hg-0 flux measurements to validate parameterizations of the Hg-0 transfer velocity contributes to this uncertainty. We measured the Hg-0 flux on the Baltic Sea coast using micrometeorological methods (gradient-based and relaxed eddy accumulation [REA]) and also simulated the flux with a gas exchange model. The coastal waters were typically supersaturated with Hg-0 (mean +/- 1 sigma = 13.5 +/- 3.5 ng m(-3); ca. 10% of total Hg) compared to the atmosphere (1.3 +/- 0.2 ng m(-3)). The Hg-0 flux calculated using the gas exchange model ranged from 0.1-1.3 ng m(-2) h(-1) (10th and 90th percentile) over the course of the campaign (May 10-June 20, 2017) and showed a distinct diel fluctuation. The mean coastal Hg-0 fluxes determined with the two gradient-based approaches and REA were 0.3, 0.5, and 0.6 ng m(-2) h(-1), respectively. In contrast, the mean open sea Hg-0 flux measured with REA was larger (6.3 ng m(-2) h(-1)). The open sea Hg-0 flux indicated a stronger wind speed dependence for the Hg-0 transfer velocity compared to commonly used parameterizations. Although based on a limited data set, we suggest that the wind speed dependence of the Hg-0 transfer velocity is more consistent with gases that have less water solubility than CO2 (e.g., O-2). These pioneering flux measurements using micrometeorological techniques show that more such measurements would improve our understanding of air-sea Hg exchange. |
| Databáze: | OpenAIRE |
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