From Cloud Seeds to Lightning-Made Fertilizer

It’s counter-intuitive but true that water vapor has a hard time turning into water droplets without a solid or liquid surface to act as a seed.  Once liquified, water droplets can remain in a supercooled state below the freezing point in the absence of crystallization surfaces. The correct term for this “seed” is a cloud condensation nucleus, unfortunately creating the need for yet another abbreviation (CCN).

In the 1960s and 1970s James Lovelock proposed that aerosol particles which act as cloud-condensation nuclei (CCN) in the marine atmosphere are principally, perhaps almost exclusively, non sea-salt SO42- particles derived from the breakdown and oxidation of an organic compound (dimethyl sulphonio propionate) that algae used to remain isotonic with their saline environment.

The “perhaps almost exclusively” part was unfortunately never substantiated by evidence. A recent review study revealed that dust, sea salt, soot, biological particles such as pollen along with secondary organic aerosols—Lovelock’s non sea-salt SO42- —can all act as CCN. In fact, the ability of all this material to act as cloud seed depends far less on their chemical composition and more on aerosol particle size.

Another important conclusion from the review of the literature involves the impact of human activity on CCN:

Model calculations and observations in remote continental regions consistently suggest that CCN concentrations over the pristine continents were similar to those now prevailing over the remote oceans, suggesting that human activities have modified cloud microphysics more than what is reflected in conventional wisdom.

Lightning photographed by the author on July 27 in Montreal.
Lightning photographed by the author on July 27 in Montreal.

Once the droplets and ice crystals do form, rising droplets in cumulonimbus clouds collide with ice crystals. Electrons are transferred leading to the major static responsible for lightning.

The bolts of lightning, as this Nova video http://www.pbslearningmedia.org/resource/nves.sci.earth.nitrate/lightning-produces-nitrates/ explains are not very thick but are energetic enough to melt sand and break nitrogen’s triple bond. The free nitrogen atoms then attack air’s other main component, oxygen, to form nitrate, which is an important fertilizer.

Although Lovelock’s Gaia hypothesis is not backed up by observations—the algae with its byproduct aren’t single-handedly bioregulating wind patterns and eventual distribution of nutrients in the sea—there is in reality an astounding interplay of geology, biology and climate on our planet. Even in the absence of man, dust from dry lake beds and volcanoes, pollen and organics from land and microscopic sea organisms, respectively, make condensation possible, which then leads to lightning. Finally the latter forms nitrates which fertilize soil and seas,  finding their way into the proteins and genetic material of life.

Aside from highlighting the planet’s interconnections and revealing that divisions between science disciplines are often academic, the Gaia has important philosophical implications.

In Lovelock’s view humanity is peripheral, though dangerous, to the life systems of the planet. Our anthropocentric concern is to preserve the earth as we want it. Lovelock believes that ideas of stewardship of the planet are absurd and dangerous “hubris“: “We’ll never know enough…….. The answer is ’hands off”….Micro-organisms drive the system and we cannot influence them.

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