SolarBees and methylmercury

For years I jogged past Almaden Lake and biked past Guadaulpe and Almaden reservoirs, curious each time what those alien-looking contraptions were floating in the water. Half-consciously, I imagined they measured the water's temperature or chemical composition. Those "antenna," I imagined, were powered by the photovoltaic panels and transmitted the data back to a park computer.

Wrong! They're SolarBees: solar-powered water-circulation machines that prevent the harmful buildup of methylmercury in stagnant water at the bottom of the lake. The solar panels convert sunlight to electricity to power the circulation motors.

Almaden Lake is contaminated with quicksilver (mercury) originating from the New Almaden mines located 10 miles to the south, in an area now known as Almaden Quicksilver Park. The mines were open from 1847-1976. From the start of the California Gold Rush (1848-1855), mercury was used to extract gold and silver from mines in the Sierra Nevada mountains.

Mercury was used in gold mining because it dissolves gold from rock to form an amalgam of gold and mercury. The gold can then be extracted from the amalgam by heating, which causes the mercury to vaporize. The airborne mercury then condenses and falls to the ground, contaminating the land and water. At Quicksilver, mercury got into our local environment through the mercury mining process itself, not from the gold extraction process.

At Almaden Lake, elemental mercury (Hg) from the mines settles at the bottom of the lake. There, it is converted to methylmercury (CH3Hg) by the metabolic processes of naturally occurring anerobic (oxygen-hating) bacteria that live in the sediments. The methylized version of mercury gets into our food chain by being absorbed by aquatic plant life, which is then eaten by fish. The fish, of course, are eaten by birds and humans. Methylmercury is the most toxic form of mercury, and it is especially harmful to embryos. "Do not eat the fish" signs are plentiful around Almaden Lake and at the Almaden and Guadalupe Reservoirs.

SolarBees interrupt the mercury methylization process by circulating oxygen-rich water from the surface down to the oxygen-depleted regions below. The aerated (oxygenated) water inhibits the metabolic processes of anerobic bacteria that produces the methymercury. I've jogged past Almaden Lake for 13 years and I've also seen a noticable improvement in water clarity in the past few years since the SolarBees were installed. SolarBees are also in the Guadalupe and Almaden Reservoirs. Next time I'm there I'm going to check out the clarity of water there.

SolarBee: http://www.solarbee.com/
Almaden Quicksilver Park: http://www.geocities.com/almadenqs/
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