John Hunter and John Cary from the US Department of Agriculture, at Fort Collins, Colorado have found that corn and soya bean oils provide the denitrifying bacteria that live at the bottom of the wells with a rich source of carbon.

When energy-rich oil is injected into the ground under pressure, it stays trapped in the soil. This extra food stimulates the bacteria at the oil-water interface to grow and multiply. As they do so, they break down the nitrate in the contaminated water, turning it into nitrogen, which dissolves in the water.

Fertilisers, animal manure and water treatment systems, all introduce nitrates into the groundwater. Their presence is not generally considered to be a major health threat, but if pregnant women drink water contaminated with high levels of nitrates, it can cause “blue baby syndrome”. The condition arises when the nitrate prevents oxygen from binding to the haemoglobin in red blood cells. It is not always possible to narrow down the source of nitrate pollution, which makes it difficult to tackle.

Many underground wells in the US contain much higher levels of nitrate than the accepted drinking water standard of 10 parts per million. Cary says that his oil-guzzling bacteria have reduced nitrate concentrations from 180 parts per million to between 2 and 3 parts per million in pilot experiments.

Hunter and Cary hope to carry out large-scale field trials. They also intend to find out if vegetable oil will prompt other bacteria to break down organic pollutants, such as petrol and solvents.

Staff were worried that vibrations from pile drivers during the renovations would damage the fossils. But when the specimens were removed from the wall, two of the museum’s palaeontologists, Lorraine Cornish and Adrian Doyle, noticed that many of the fossils were already in a sorry state. “One of them was crumbling so badly that it actually bowed the glass case, and we realised it was only a matter of time before it shattered glass all over the floor,” says Doyle.

Much of the damage was caused by the “rusting” of iron pyrites present in the rock and fossilised bone. The pyrites reacts with moisture in the air to produce sulphuric acid, which erodes the fossil and causes the shale and limestone rock in which it is embedded to split and crack.

Most of the specimens were removed from the gallery for restoration. But a few were too big to fit through the doors and were restored in a temporary glass laboratory in the gallery, dubbed the “goldfish bowl”. This was hugely popular with the public, who could watch the conservators at work via closed circuit TV.

The Victorians thought a shiny coating of shellac improved the look of the fossils. So before Cornish and Doyle could treat the iron pyrites decay, they had to remove a thick layer of varnish from many of the specimens by dissolving it with a solvent gel. This technique is used to restore paintings but had never been tried on fossils. The palaeontologists then applied a poultice containing ethanolamine thioglycollate, which neutralises the sulphuric acid, stabilises the iron compounds and removes the products of pyrites decay.

Cornish and her team hit a snag when they found that earlier conservators had filled gaps and cracks in some specimens with a mixture of glue and white asbestos. They also found other unexpected materials. In the 1830s, when some of the fossils were first mounted, sand and wax were used as filling material. “In one of the specimens it looks like they ran out of packing material and used anything they could find. There was newspaper, reeds, string, pebbles, cotton and horsehair – literally stuffed in to fill the gaps behind the fossil,” says Doyle.

Cornish believes the conservation project, which took three years, is the largest of its kind in the world. It is also the first time that researchers have been able to examine the fossils close up. To enable other palaeontologists to study the anatomy and bone structure of some of these creatures in detail, Cornish and Doyle agreed to cut off the heads of five of the ichthyosaurs and replace them with exact replicas. Cornish will dissolve away the shale surrounding the bones of the skulls with acid, allowing examination from both sides.

Now that the collection is back on display, Doyle has set up sensors to monitor changes in temperature and humidity inside the fossils’ display cases, to try and prevent any further decay. The mahogany cases, complete with new toughened safety glass, are secured safely to the gallery walls. So there is no longer any danger of a two-tonne stone sea dragon landing on your head.

Techniques that can clean the soil in situ, such as pumping out the groundwater or using oil-digesting bacteria, tend to remove only the shorter hydrocarbon chains which are more soluble in groundwater. The longer, heavier hydrocarbon chains often stay trapped in large droplets between the grains of soil.

Koen Weytingh and his colleagues at the Technical University of Delft and De Ruiter Milieutechnologie in Halfweg, the Netherlands, have been trying out sound waves to break up the droplets containing these heavier fractions so they can be washed out.

The researchers set up two columns of wet sand contaminated with diesel fuel. They passed sound waves through one of the columns at a number of frequencies, and then compared the amount of oil that could be removed from each by pumping water through the two sand beds until no more oil emerged. Mter five days, 71 per cent of the diesel fuel was removed from the vibrated column, compared with 40 per cent in 11 days from the untreated column.

The sound waves make the oil drops vibrate at their natural frequency until they disintegrate into smaller droplets. Smaller droplets can escape more easily from the capillary forces that trap larger oil droplets in the spaces between soil grains. Once freed from the soil matrix, smaller droplets also mix more intimately with the wash water.

The range of molecules recovered from the vibrating sand bed corresponded to the normal composition of diesel oil, with hydrocarbon chains ranging from 10 to 40 carbon atoms long. So the water was indeed washing out longer molecules than usual, rather than simply removing more of the shorter compounds.

According to Weytingh, the frequency of the sound is very important. High-frequency vibrations tend to be damped by the soil and groundwater so they work only over a limited distance. But sound at too low a frequency can compress the soil. Weytingh says: “This will cause the soil to subside to such an extent that the houses which were spared demolition thanks to this technique will collapse anyway.”

Following the success in the laboratory, one of the researchers at Delft, Jaqueline Sändker, is now investigating the feasibility of incorporating sound waves in a fullscale clean-up system.

Clair Brunton and Michael Majerus of Cambridge University have found that the UV coloration of European Colias butterflies and Gonepteryx butterflies from the Canary Islands varies as much between individuals within a species as it does from one species to another. This suggests that the insects do not use the patterns to recognise fellow members of their own species, but instead may use their UV vision to judge the quality of prospective mates or opponents.

The coloration is created by ridges on the butterflies’ wing scales which reflect UV light to different degrees, resulting in bright iridescent patterns. Brunton and Majerus studied these patterns using a UV-sensitive camera. They found that there were significant differences between UV and visible patterns on the same wing, suggesting that the two types of coloration evolved separately.

To pick up all the detail of the UV patterns, they also used a spectrometer to record the overall spectrum of UV light reflected by the butterflies’ outstretched wings. These spectra revealed a huge variation in UV coloration within each species (Proceedings of the Royal Society B, vol 260, p 199).

Since the iridescent UV patterns are most marked in males, the zoologists suspect that they could either be associated with mate choice by females, or that they could be used to communicate a male’s status and quality to his rivals. Female Colias and Gonepteryx avoid mating with males which have recently mated with another female, because they produce only about 40 per cent as much sperm and seminal fluid – from which the females absorb nutrients – as “fresh” males.

The wings of males who are a few weeks older, and more likely to have mated already, reflect less UV than younger males due to wear and tear on the ridges of their wing scales. Larger males, who consequently have larger UV wing patterns, also produce more seminal fluid. So females may use the intensity and size of UV patterns to judge the reproductive quality of an approaching male.

Brunton and Majerus plan to test these ideas by examining the behavioural responses of female Colias butterflies to males with contrasting UV patterns. They intend to take fresh males and scrape off the UV-reflecting scales from the wings of some, and stick extra scales with UV patterns onto the wings of others. Since all the males will be equally fresh, the experiments should determine whether the females choose on the basis of UV patterns alone.

llya Raskin from the AgBiotech Center, Rutgers University in New Jersey, has been hydroponically growing various terrestrial crop plants, ranging from spinach to tobacco, and studying how their roots absorb and accumulate metals such as lead, zinc and chromium. The Indian mustard, Brassica juncea, was the most efficient at removing a variety of metals, accumulating up to 60 per cent of its dry weight as lead (Environmental Science and Technology, vol 29, p 1239).

Common aquatic plants like duckweed and water hyacinths have previously been used downstream of industrial plants that produce heavy metal pollutants. But these plants are inefficient at removing metals because they are small and have slow-growing roots.

Raskin is now developing large-scale rhizofiltration systems to clean up polluted waste in streams. B. juncea will be grown anchored in troughs that are suspended over the contaminated water. The extensive root systems hang under the troughs immersed in the water. Once the roots are saturated with metals, they can be harvested, dried and burned, and the metals recycled from the remains.

Some cultivars of B. juncea can even tolerate the uptake of radionuclides like strontium, caesium and uranium, concentrating a hundred times more of the heavy metals in their roots than is present in the water. Raskin is currently testing these plants in the soil and water in the Chernobyl region of the Ukraine.

The most popular technique for removing heavy metals from water currently involves precipitating the metals to produce a hazardous solid waste, which is costly to dispose of. The combined cost of cleaning up heavy metal and radionuclide pollutants in surface and groundwater is estimated at over $7 billion in the US alone.

Mark Rutenberg of Neuromedical Systems, New York, developed PAPNET. He describes manual screening as “looking for a needle in a haystack”. On average, only between 3 and 5 smears out of every 100 have abnormal cells in them.

Dulcie Coleman, head of the St Mary’s cytopathology department has been evaluating PAPNET since November, comparing it with manual screening. The system will not replace human experts but will act as an extra “eye”, identifying abnormal cells that may have been missed.

With the existing system of quality control a second technician rapidly checks all negative slides, scanning each slide under the microscope for around 90 seconds. The technicians must examine thousands of cells, and they may miss abnormal ones because they “see” the cell shapes they expect to see, unintentionally converting an abnormal into a normal image.

The PAPNET system checks every cell of each slide. It selects the 128 that appear the most abnormal, and displays them on a colour monitor. These can then be checked by the technician, who refers back to the slide to decide whether or not the cells are indeed abnormal.

So far, over 1000 negative slides have been rechecked by PAPNET at St Mary’s. The results are improving as the technicians become more familiar with the system. Coleman says that they will have the results of the trials in another six months, and that the system is on target to cut the false negatives to 2 per cent.

The PAPNET system has been used in the US by Leopold Koss, of the Albert Einstein College of Medicine, New York. Koss is using it to recheck false negative smears in patients where a later smear indicated invasive cervical cancer. There were fears that these patients may have developed cancer much more rapidly than normal. But when previous negative slides were rechecked using PAPNET, the system identified abnormal cells in smears taken up to 12 years before the positive diagnosis.

D. major grows in the forests of Sarawak in Malaysia. Instead of putting roots down in the soil, which in any case contains very few nutrients, it grows on the surface of trees. Its greatest challenge is to obtain enough nitrogen and carbon while conserving water. This is where the ants come in.

The leaves of D. major are rolled up to form enclosed sacs, which are inhabited by ants of the genus Philidris. The researchers suspected that the ants provide D. major with nutrients in return for shelter To test this idea, they looked at the ratios of different isotopes of carbon and nitrogen in the plant’s tissues.

The carbon dioxide exhaled by ants contains a lower proportion of the isotope carbon-13 than atmospheric CO₂, Treseder explains. The researchers found that this was also true of the carbon in the tissues of D. major. The ants feed on insect carcasses which they drag back to the leaf sacs. This carrion and the ants’ faeces are rich in nitrogen, of which a higher proportion is nitrogen-15 than is the case for the nitrogen dissolved in rainwater. The plant’s tissues are also relatively rich in nitrogen-15.

From precise measurements of the amounts of carbon-13 and nitrogen-15 in D. major leaves, Treseder and her colleagues calculated that 39 per cent of the carbon and 29 per cent of nitrogen absorbed by the plants comes from the ants (Nature, vol 375, p 137). The carbon is simply absorbed through the leaves, but the nitrogen is taken up by roots which grow out from the stem into the accumulated debris inside the leaf sacks.

By associating with ants, D. major also conserves water. The plants absorb carbon dioxide through pores, or stomata, on the inner surfaces of the sacs, while keeping the stomata on the outside of the sacs firmly shut. Water lost through evaporation remains in the sacs and can be reabsorbed. This allows D. major to colonise hot, dry forests.