Oct 15, 2013

Do upper Penobscot Bay marine fogs carry bay-upwelled mercury to upland coastal vegetation? And air breathers?

Marine fog has been shown on the west coast to carry vaporized mercury rising from a polluted seafloor area via water upwelling onto the leaves of mainland trees and other vegetation where the fog penetrates.  How about here? 
Sears Island getting fogged
Across the  continent, the  researchers at the UC Santa Cruz released a study in 2012 Total and monomethyl mercury in fog water from the central California coast.  Peter S. Weiss-Penzias, et al found that marine fog  collectively accounted for from 7–42% of elemental mercury and from 61–99% of methylmercury in total atmospheric deposition estimated for the coastal area . (Other vectors are rain, and dry deposition.)

According to that report"These initial measurements suggest that fog precipitation may constitute an important but previously overlooked input of MMHg to coastal environments. Preliminary comparisons of these data with associated chemical, meteorological and oceanic data suggest that biotically formed MMHg from coastal upwelling may contribute to the MMHg in fog water."

While this has been shown to be the case on a portion of the California Coast, the issue has not been examined in Maine. 

However, a significant amount of the tons of mercury spilled and leaked into the lower Penobscot River by HoltraChem has made its way into the sediments of the upper Penobscot Bay, according to a court ordered study.

In areas of the upper bay where upwelling is strong, it is likely that fog in the waters off Searsport, Belfast Stockton Springs and Islesboro and Castine could be transporting mercury to terrestrial vegetation and air breathers on the shore.

There are several prominent upwelling areas in the upper Penobscot Bay that could carry out that action: According to lobsterman Mike Dassatt,  if mercury tainted sediments are dumped in the Rockland Disposal Site  prevailing bottom currents will transport it up both sides of Islesboro and back to the upper bay. If dumped in the Belfast offshore dumpsite, strong upwelling currents there would even more quickly bring methy mercury to the surface if it were in the dredge spoils dumped there.

What is to be done?  Students at Unity College are preparing to carry out a study that will determine whether mercury can be found in the vegetation of Sears Island as well as long lived intertidal organisms.  The results of that study should be revealing.

Stay tuned.

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