Monthly Archives: December 2019

Ocean Woes

Threats to the biosphere from changes in the oceans are real. Global warming involves not just atmospheric heating but also sea surface warming. About half the increased warming is going to the oceans. This can have wide-ranging effects, with deoxygenation at or near the top of the list of risks.

Henry’s law states that the solubility of gasses in water is inversely proportional to temperature. What this means is that warmer water holds less oxygen. Anglers in Arkansas recognize three distinct kinds of conditions for fishing. Likely the most common fishery in Arkansas is a lake where the water temperature and hence the oxygen content supports fish such as largemouth Bass, sunfish, and the like.

If you are after smallmouth bass you are unlikely to find them in a lake, at least here in Arkansas. Smallmouth bass require a higher oxygen content that is available only in cooler water – usually clear streams that flow fast enough to avoid warming from the sun. It is not uncommon to see smallmouth bass at the cooler upstream ends of creeks and largemouth at the lower, warmer reaches.

Trout are the most demanding in terms of oxygen needs. Trout only thrive in cold water with the highest oxygen concentration. Here is Arkansas that means creeks that get the majority of their flow from springs and the cold tailwaters of impoundments.

The point of this freshwater digression is to point out that the variety and number of fish in a given locale is dependent on water temperature. This is also true in the oceans. There is a reason that megafauna such as whales spend their time in the cold, oxygen-rich waters of the arctic and Antarctic regions – that’s where their food is found in abundance. As the surface of the oceans warm, we should expect changes in where fish and sea mammals alike can survive. Just that sort of change is happening and it doesn’t look good.

Cod are an extremely important commercial fish found in northern regions of both the Atlantic and Pacific Oceans. The importance of this fish alone can not be overemphasized. The coastal regions of northern Europe have depended to a large degree on access to Cod. In the middle of the twentieth century the United Kingdom and Iceland were all but at war over fishing rights to the cod in the north Atlantic near Europe.

The trouble with cod now centers in the North Pacific. Just last week, the Gulf of Alaska was closed to cod fishing for the 2020 season. Stocks have been declining for several years, not from overfishing as occurred in the Grand Banks region of the Atlantic, but from ocean warming. The Arctic is warming much faster than the rest of the planet. Glaciers are receding, arctic ice is diminishing and now fish stocks are dwindling.

In the future, it is conceivable that other more tolerant species of fish can migrate into the warming Arctic waters but for other locales, this isn’t possible. Fish currently in the tropics are already the only species tolerant of the lower oxygen concentrations. Higher temperatures will likely create fish “deserts.”

Dr. Bob Allen is Emeritus Professor of Chemistry, Arkansas Tech University

wind turbine

Size Matters/Wind Turbines

Utilization of the wind for motive power has a long and rich history. Wind-powered sailing vessels were known to ply the Nile river somewhere between 3 and 5 thousand years before the common era (BCE.) Although there is no direct evidence, it is quite possible that sailing craft could have been employed 50 thousand years ago to populate Southeast Asia and Australia.

Stationary power production in the form of lifting water has been dated to a few centuries BCE. Similarly, the wind was used for motive power to grind grain. The use of wind turbines in the Netherlands is legendary. By the 14th century CE, the Dutch were making extensive use of wind turbines to pump water out of the Rhine river basin to recover and maintain dry land. There is a reason this part of Europe is referred to as the “Low Countries.”

The history of wind for the generation of electrical energy is of course much younger. In 1877 Professor James Blythe in Glasgow, Scotland erected a 10-meter tall cloth-sailed wind turbine connected to batteries to light his cottage. Small scale isolated wind-powered electrical production has been in use around the world, including early twentieth-century Midwestern United States. Centralized power delivered via rural electrification in the 30s replaced virtually all small systems.

The modern era of electrical power production began in the 70s following the formation of the Organization of Oil Exporting Countries (OPEC) and subsequent oil price shocks and embargoes. The price of crude oil skyrocketed and shortages of gasoline forced rationing. Later years saw the federal government subsidize wind power with grants and production credits. In 1990 less than one percent of total electrical energy in the United States came from wind. Currently is over seven percent.

The real change in wind power is the size of the turbines themselves. The earliest modern turbines averaged 50 kW, enough to power only a handful of homes. Also, these early turbines were erected on derricks which made for attractive roosting sites birds, especially raptors which led to unacceptable bird kills. The development of monocoque supporting towers have greatly reduced but not eliminated bird kills.

By the start of the twenty-first century, the average turbine size increased 30 fold. These giants produce about 2 MW. Simple calculations show that the midwestern United States could easily produce all the electrical needs of the country except for the distribution problem – most Americans live near the coasts far from the windy central United States.

The real expansion of wind power will occur with off-shore installations. Most off-shore wind is now located in shallow near-coastal areas, but plans for real behemoths on floating towers are in the works. Each of these 20+ MW plants, taller than the Eiffel Tower, can provide energy for tens of thousands of homes.

Both wind energy production and potential continue to grow. The cost of energy production continues to drop and with the advent of large off-shore plants comes more reliability and less intermittency.

A Natural Reaction

Uranium is, of course, the stuff of nuclear reactors and atomic weapons, but it is also part of an intriguing detective story from 1972 that traces back to events two billion years ago – actually 4.5 billion years but at that age who’s counting.

First a little background. For either nuclear reactors or bombs, Uranium 235 is required. This isotope of Uranium has fewer neutrons in the nucleus and is present in small concentrations with U238, the most common isotope. U235 with a natural concentration of 0.72 %, must be concentrated further to make a fissile material that is used in reactors and weapons.

In the early seventies, there was something of a panic in France. France, then as now provides the lion’s share of their electricity from nuclear reactors. At the time France was buying Uranium ore called yellow cake from a mining region in the Oklo River basin in Gabon, Africa. Assays of some shipments showed that the ore was unnaturally low in U235, sometimes by as much as half the expected concentration.

During this period there was much civil unrest as the continent slowly emerged from under the yoke of colonialism. It was feared that Uranium was being stolen by a local tribe with the intention of making a crude bomb. It turns out that the problem was a rather unnatural event in nature. When scientists looked at an analysis of the shipments low in U235 they found several unnatural elements such as Americium, Curium, and Polonium.

These so-called transuranic elements were not known to exist in nature until this discovery. The only place they had been observed was as part of the waste from nuclear reactions, both controlled reactors and bombs. The French had discovered an extremely rare event, a natural nuclear reactor.

When the U235 atoms draw too close together a chain reaction occurs which produces heat. That heat is used to produce steam in nuclear reactors. In the process, the U235 reacts to turn in to other elements. Exactly the same process occurred in the Oklo River basin.

Over two billion years ago there was scant free Oxygen in the air, then along came cyanobacteria. Gradually the atmosphere changed and many minerals reacted with Oxygen. All the rusty looking soil across the planet is due to Iron Oxide which formed during this period.

In the case of Uranium, it became more water-soluble as it oxidized. In locations with rich Uranium deposits such as the Oklo River basin, this allowed for the dissolved Uranium to accumulate in shallow lakes. Over time some of these lakes became isolated and as the lakes evaporated the Uranium was concentrated. Another bacteria capable of taking the Oxygen away from the Uranium Oxide reduced the solubility even further.

When the Uranium in these pools reached critical mass – the concentration necessary for a chain reaction – the U235 fissioned producing heat and forming the transuranic elements. As the reactions proceeded the U235 was depleted. Altogether sixteen different sites in the river basin have been found to have undergone fission reactions. To date this is the only known place on earth where a natural fission reaction has occurred.

Dr. Bob Allen is Emeritus Professor of Chemistry, Arkansas Tech University.