I think Nicholas Bloom looked subject at this in the 1980's. The papers came out of UConn, Bill Fitzgerald was the other name on them, I think. There is a lot of more recent work though. Here's someone who is on ResearchGate. Maybe ask her?

https://www.researchgate.net/publication/223484907_Evasion_of_mercury_from_coastal_and_open_waters_of_the_Atlantic_Ocean_and_the_Mediterranean_Sea

Article Evasion of mercury from coastal and open waters of the Atlan...

yes, my PhD student

Emanuela Bagnato and colleagues, with flux chambers. Similar to some work in freshwater. Very difficult...analytical technology now is slow for Hg relative to other gases and properties, making fancier techniques like eddy covariance likely unusable. Chambers will give you some data...but not practical under most conditions. Most everyone uses gas exchange models, like Dr. Asher's, coupled with Hg0 measures in air and water. This of course requires making assumptions about Schmidt and other constants.

The question sounds difficult in general...has it been attempted for other gases?

I have used a Tekran instrument to do ambient air measurements here in Costa Rica. This instrument has a peripheral intended to do measurements in water too. From my point of view, the keypoint here is to have a reliable flux chamber, which is positioned on the water. I agree with the fact that gas exchange models coupled with Hg0 measures in air and water are required in this case.

You may also ask David Lean (University of Ottawa):

https://www.researchgate.net/profile/David_Lean/

Another problem remains to sample the microlayer free of contamination to get its mercury concentration. Common glass plate techniques is not suitable for trace metals, but Bill Landing (Florida State University) and his graduate student have recently developed a sampling technique using quartz glass drum.

Thank You for answers.

Most scientists mentioned above conducted their research in subsurface water not in the sea-surface microlayer. Therefore the air-sea exchange of gaseous mercury was estimated based on concentration of Hg in subsurface water, using the two-layer model developed by Liss and Slater (1974). Taking into account that:

(1) the sea-surface microlayer constitute a real interface between sea and air,

(2) the sea-surface microlayer is usually significantly enrich in dissolved gaseous mercury relative to underlying subsurface water,

(3) the sea-surface microlayer is place where photochemical and biological processes can impact Hg transformation (in particular gaseous mercury production),

I wonder why the sea-surface microlayer is not taken into account in this estimation?

I understand that the correct collection of sea-surface microlayer is difficult and time-consuming, but exchange of elemental mercury at the air-sea interface estimated without taking into account this layer could be erroneous.

In my research sea-surface microlayer was collected by means of the polyethylene Garrett screen (about 250μm in thickness), while subsurface water (0.5m depth) was collected with the bathometer. During the sampling and measurements we followed the clean techniques. Experiment with blank samples showed that the Garrett screen did not introduce contaminants into the samples. My results show that in coastal region the sea-surface microlayer was enriched in dissolved gaseous mercury by factor of 3 to 4, relative to underlying subsurface water. Likewise Hg flux from sea-surface microlayer was more than 3 times higher than from subsurface water. But can I calculate flux of Hg from microlayer using the gas transfer velocity of mercury (kw) and the Schmidt number (Sc) of mercury estimated for subsurface water? Taking into account that the sea-surface microlayer is not typical sea water but a mixture of surfactants,

I wonder if this difference in the Hg flux is resulting from the specific of the microlayer or mismatched parameters in the model?

Schmidt number depends on diffusivity and on viscosity. The microlayer may have, under certain condition, a higher viscosity, especially if samples were collected from heavy slicks. We did something similar for semivolatile organics (Wurl et al. 2007). We were inspired by the work of Zhou and Mopper (1997). More recently, He and Fu (2013) published a theoretical framework (no experimental data) on the microlayer effect in air-sea gas exchange

Hope it helps.

Wurl, Oliver, Subramanian Karuppiah, and Jeffrey Philip Obbard. "The role of the sea-surface microlayer in the air–sea gas exchange of organochlorine compounds." Science of the total environment 369.1 (2006): 333-343.

Zhou, Xianliang, and Kenneth Mopper. "Photochemical production of low-molecular-weight carbonyl compounds in seawater and surface microlayer and their air-sea exchange." Marine Chemistry 56.3 (1997): 201-213.

He, C. L., and T. M. Fu. "Air-sea ex-change of volatile organic compounds: A new model with microlayer effects." Atmos. Oceanic Sci. Lett 6 (2013): 97-102.

I apologize for such a long delay, but I had to learn about the microlayer to be able talk with you.

According to the He and Fu model I calculate the air-sea microlayer flux using the kg (equation described by Schwarzenbach et al. (2003)). In this case kg is 100 to 1000 higher than kw. In consequences, obtained air-sea flux values ​​are much too high, for me.

But I think/hope I found the solution to my problem. In few publications I found information that the presence of the soluble surfactants in microlayer causes kw suppression in the range 5–50% (average 20% in coastal zone). So I try to calculate the flux using the 80% value of kw and the Hg concentration in microlayer. As a result I get the air-sea flux about twice higher than those measured from subsurface water. I realize that this is a huge approximation. The suppression of Hg flux depends on the thickness and composition of the microlayer (ie the meteorological conditions or primary production) - I can discuss this. But obtained yearly values are consistent with mercury mass balance for my study area (Gulf of Gdansk, southern Baltic).

Do You think it is good idea? Or should I try something else?

Hi Dominika,

you may wish to look for publications of Joachim Kuß from the German Leibniz IOW. Best regards, Michael

Hi Michael,

Thank you for information. I have read these publications.