Saturday, January 13, 2007

A Paradox for Pariahs

If a chemical system at equilibrium experiences a change in concentration, temperature, or total pressure; the equilibrium will shift in order to minimize that change.
Le Chatelier's principle

China is set to overtake the US in one important respect. With a couple of years it will become the world's biggest CO2 emitter, beating the US a decade earlier than expected. And of that output, nearly two-thirds will be derived from coal. China is believed to have little oil and gas, but coal enough to power its economic surge for at least another century. It has 13 percent of the world's coal reserves.

Unfortunately much of China's coal is high sulphur, and puts out masses of sulphur dioxide, soot, and other nasty stuff. Since they are opening coal-fired power stations at the rate of one a week, and expect to double their energy consumption by 2020, this is not good news. Some reports suggest that 1,000 new coal-fired stations are planned.

Now we have an interesting paradox. China and India both high users of high sulphur coal are also the world’s biggest producers of rice and are the largest emitters of methane from wetland rice fields .

Since 1990 the worlds methane levels are stable to slightly decreasing,this in conjunction with a ten fold increase in those countries in energy consumption,what has happened?

Wetlands are a potent source of the radiatively important gas methane (CH4). Recent findings have demonstrated that sulfate (SO4 2 ) deposition via acid rain suppresses CH4 emissions by stimulating competitive exclusion of methanogens by sulfate-reducing microbial populations. Here we report data from a field experiment showing that a finite pulse of simulated acid rain SO4 2 deposition, as would be expected from a large Icelandic volcanic eruption, continues to suppress CH4 emissions from wetlands long after the pollution event has ceased. Our analysis of the stoichiometries suggests that 5 years is a minimum CH4 emission recovery period, with 10 years being a reasonable upper limit. Our findings highlight the long-term impact of acid rain on biospheric output of CH4 which, for discrete polluting events such as volcanic eruptions, outlives the relatively short-term SO4 2 aerosol radiative cooling effect.

Gauci, V., N. Dise, and S. Blake (2005), Long-term suppression of wetland methane flux
following a pulse of simulated acid rain, Geophys. Res. Lett., 32,

So what happens when we reduce sulphur in a system that has adjusted to the higher levels of acidic rain.

Acid rainfall in the Appalachian Mountains has decreased in recent years and organisms in its streams are thriving. But the environmental comeback could be creating new problems of its own, scientists say.

A drop in nitric and sulfuric acid levels in the streams is changing biological activity in the ecosystem and hiking dissolved carbon levels, scientists reported at the American Geophysical Union conference last week in San Francisco.

Dissolved carbon dioxide occurs as a result of organism respiration and decay of organic matter. It is a key source of acidity in pristine water.

"These are unexpected results," said David DeWalle, a researcher at Pennsylvania State University. "Rising amounts of carbon dioxide in streams and soil could have implications for the forest ecosystem, and the carbon balance in general."

Using Le Chatelier's principle we can predict that if we are to add a species to the overall reaction, the reaction will favor the side opposing the addition of the species. Likewise, the subtraction of a species would cause the reaction to fill the “gap” and favor the side where the species was reduced.


Post a Comment

Links to this post:

Create a Link

<< Home

Web Counters