Pitt ducked through a cabin door to the galley and returned, handing Gunn a cold bottle of beer.
Gunn took several swallows and sighed. Then he said, "Okay, to answer your question. There are three key elements to our search approach. The first requires an automated micro-incubator. I use this unit to expose a tiny sample of river water into vials containing red tide samples we obtained off the coast. The micro-incubator then optically monitors the growth of the dinoflagellates. After a few hours the computer gives me an indication of how potent the concoction and how rapid the growth of the little buggers. A little play with numbers and I have a reasonable estimate of how close we're coming to the source of our problem."
"So the red tide stimulator isn't coming from Nigeria."
"The numbers suggest the source is further up the river."
Gunn moved around Pitt to a pair of square, box-like units about the size of small television sets but with doors where the screens would have been. "These two instruments are for identifying the nasty glo
b, as I call it, or a combination of globs that's behind our problem. The first is a gas chromatograph/mass spectrometer. To put it concisely, I merely take vials of river water samples and place them inside. The system then automatically extracts and analyzes the contents. The results are interpreted by our on-board computers."
"What exactly does it tell you?" asked Pitt.
"It identifies synthetic organic pollutants, including solvents, pesticides, PCBs, dioxins, and a host of other drugs and chemical compounds. This baby, I hope, will home in on the chemistry of the compound that's mutating and stimulating the red tide."
"What if the contaminant is a metal?"
"That's where the inductively coupled plasma/mass spectrometer comes in," said Gunn, gesturing at the second instrument. "Its purpose is to automatically identify all metals and other elements which might be present in the water."
"Looks similar to the other one," observed Pitt.
"Basically the same principle, but different technology. Again, I merely load the sample vials of water taken from the river, punch the start buttons, and check the performance every 2 kilometers."
"What has it told you?"
Gunn paused to rub a pair of red-rimmed eyes. "That the Niger River is carrying half the metals known to man, from copper to mercury to gold and silver, even uranium. All in concentrations above their natural background levels."
"Sifting through the scatter won't be easy," murmured Pitt.
"Finally," added Gunn, "the data is telemetered to our researchers at NUMA who review my results in their own laboratories and look for something I might have missed."
Pitt, for the life of him, couldn't see Gunn missing anything. It was plain that his friend for many years was more than just a competent scientist and analyst; he was a man who thought coldly, clearly, and as constructively as possible. He was a dedicated hard driver who didn't know the meaning of the word quit.
"Any hint yet of the toxic compound that might be our evil-doer?" Pitt asked.
Gunn finished off the beer and dropped it in a cardboard box filled with computer readout sheets. "Toxic is only a relative term. In the world of chemistry there are no toxic compounds, only toxic levels."
"Well?"
"I've identified a lot of different contaminants and naturally occurring compounds, both metal and organic. The systems are reading shocking levels of pesticides that are banned in the U.S. but are still widely used in the third world. But I haven't been able to isolate the synthetic chemical pollutants that cause the dinoflagellates to run crazy. At the moment, I don't even know what I'm tracking. All I can do is follow the bloodhounds."
"The further we go, the hotter the swill," mused Pitt. "I was hoping you might have a handle on it by now. The deeper we get into Africa, the tougher the return trip to the open sea, especially if the local military decides to nose around."
"Get used to the idea we might not find it," Gunn said irritably. "You don't realize how many chemicals are out there. The number comes to over seven million known man-made chemical compounds, and each week U.S. chemists alone create more than six thousand new ones."
"But they can't all be toxic."
"At some level most all of these chemicals will have some toxic properties. Anything is toxic if swallowed, inhaled, or injected in sufficient doses. Even water can be fatal if enough is consumed. Too much will flush out the necessary electrolytes from the body."
Pitt looked at him. "So there are no absolutes, no guarantees."
"None," Gunn shook his head. "All I know for certain is we haven't passed the spot where our doomsday plague empties into the river. Since entering the delta and passing the main tributaries of the lower Niger, the Kaduna, and Benue Rivers, the water samples have driven the dinoflagellates into a frenzy. But I haven't a clue that points to the villain. The only good news is that I ruled out bacterial microorganisms as the cause."
"How did you eliminate it?"
"By sterilizing the river water samples. The removal of bacteria didn't slow down the little buggers from proliferating one little bit."
Pitt gave Gunn a light pat on the shoulder. "If anyone can put a collar on it, Rudi, you can."