Oil spills and chemical leaks can wreak havoc on the environment, but who is legally responsible for fixing the damage? Maria Burke investigates.

Oil spills and chemical leaks can wreak havoc on the environment, but who is legally responsible for fixing the damage? Maria Burke investigates.

Finding someone to blame for a pollution incident and, of course, someone to bear the clean-up bill, is big business in the US. Four years ago, a new term was coined to label those scientists working to determine sources of pollution. Now environmental forensics is establishing itself in Europe.

Environmental forensic scientists are knowledgeable in many areas: chemistry, physics, biology, ecology, statistics and environmental legislation to name but a few. Using tools ranging from chemical characterisation to biological markers, they try to find out where environmental contamination originated, when it happened and how it occurred. It is also important to know whether an incident was a routine release or a one-off accident. They explore the extent of the contamination, and any ecological or environmental health effects, as well as investigating any evidence of fraud. Often, they are asked to point the finger at the responsible party and act as expert witnesses in court cases.

This discipline needs its own name and shouldn’t just be called ’environmental science’, says Robert Morrison, editor of the journal Environmental Forensics. ’The "forensics" portion of the name suggests that information will be used in a litigation or legal context, as compared with more standard environmental investigations whose purpose is often to define the extent of the contamination so that it can be remediated. The potential use of environmental evidence in legal proceedings also requires a higher level of care, documentation, etc.’ Vast amounts of money can ride on determining contamination sources. Morrison has been involved with cases having financial claims stretching up to $5bn.

Environmental forensics evolved in the US earlier than the rest of the world because of environmental regulations developed in the early 1980s. These require polluters to pay for the clean-up of contaminated land, explains Morrison, who also works for DPRA Inc., a North American environmental consulting firm. They recoup their expenses by using lawsuits to establish responsibility and allocate clean-up costs to the appropriate party. In a typical case each side hires a consultant to produce a story that is defensible in law. As a result, environmental consultancies have sprung up all over the US to provide scientific experts for court cases dealing with pollution.

Perhaps the most common cases for environmental forensic scientists involve oil and petrol pollution. Researchers can distinguish between oil brands in an oil spill because of the slight differences between different manufacturers’ products, which can be detected using statistical chemical analysis and mass spectroscopy. Examining lead isotopes is another way of distinguishing between petrol brands. When making leaded petrol, manufacturers tended to use anti-knock agents from specific lead deposits that have distinctive isotopic signatures. For many years, manufacturers added lead to petrol and there is still appreciable petrol lead in the environment, explains Bill Perkins of the Institute of Geography and Earth Sciences at the University of Wales, Aberystwyth. The individual ratios of lead’s four isotopes change over time and give a ’fingerprint’ of the lead in a particular sample, he says. This technique can also be used to track lead pollution from other sources. Lead from local rock, paint and fuel all have different isotopic signatures.

The Exxon Valdez case is a classic example of environmental forensics in practice. Exxon paid around $2bn in fines after its tanker, the Exxon Valdez, ran aground in Prince William Sound, Alaska, in March 1989. But this case is still ongoing, as Stephen Mudge, a marine chemist from the University of Wales, Bangor, explains.  A ’re-opener’ clause in the settlement allowed that, if any unanticipated problems came to light, Exxon would need to pay a further $100m.

The National Oceanic and Atmospheric Administration (NOAA) in Alaska is pressing to invoke this clause and reopen the case to take into consideration the increased toxicity of sediments in the Sound, an issue that was not covered in the original settlement. NOAA says that it has evidence to show that samples of sediments taken prior to the spill had a low toxicity. This is because, it says, up to 80 per cent of the polyaromatic hydrocarbons within the sample originated from local coal. However, an ExxonMobil team argues that pre-spill samples were already highly toxic because they contained hydrocarbons mainly from natural oil residues. They see no need to reopen the case.

The Bangor University group’s remit is extremely diverse. As well as oil spills they are also investigating algal blooms in lochs in Scotland. These Clyde sea lochs near Glasgow were suffering large expanses of algal blooms, which can be toxic to fish, explains Mudge. Local fish farms were getting the blame. The theory was that excess fish food and fish waste products in the lochs were providing nutrients for a type of algae called dinoflagellates. The thriving algae proliferated to form ’red tides’.

The team sent their research ship, the Prince Madoc, up to Scotland to take core samples of the sediment at the bottom of lochs. Analysis of biomarkers for hydrocarbons allowed scientists to date the cores. ’The top half-metre of sediment was deposited after the Industrial Revolution around 1750. We know this because we could detect markers for coal burning after this point, but not before,’ says Mudge. ’There was another increase in these coal-burning markers higher up the core as the number of cars increased around the 1920s.’

The team analysed a suite of biomarkers such as sterols, fatty acids and fatty alcohols, which are integral parts of various organic matter including sewage, algae and terrrestrial plants. They found the biomarker for dinoflagellates started to increase in a layer dated long before fish farming started in the lochs. Mudge explained: ’the increase coincided with an increase in markers for sewage around 200 years ago. This makes sense because sewage effluents would have increased as the Glasgow population really started to expand around this time. We think the sewage contained a range of nutrients that had triggered the algal blooms.’ However, the team also found another increase in the dinoflagellate marker in sediments corresponding to the time fish farms were introduced about 40 years ago. They concluded that the fish farms had not caused the algal blooms, but were worsening the situation.

At present, his team is working on a case involving an old copper mine on Parys Mountain in Anglesey. This mine used to be one of the world’s biggest copper-producing sites, but it was abandoned in the late 18th century. Towards the end of its life, its operators built several horizontal tunnels into the mountain-side which they plugged with concrete. The plugs contained pipes with valves. Periodically, the operators would open the valves and release water that had built up inside the mine. This water was highly acidic, and contaminated with copper and iron, explains Perkins. The operators collected it in tanks containing scrap iron so they could precipitate out copper and the pigment ochre. After a while, this process became uneconomic and the mine was abandoned.

However, recently the Environment Agency and the local population became concerned that the plugs were unstable. They feared that acidic minewater could escape and flood the nearby town of Amlwch. The Environment Agency allowed the local council to pump 200 000 cubic metres of untreated water out of the mine into the Irish Sea in the first half of 2003.

In this case, the scientists know where the pollution has come from, but they don’t know how the polluted water - which contains copper, iron, aluminium, arsenic, cadmium and ochre - will affect the marine environment in the short-, medium- and long-term. Perkins’ team is using a range of marine organisms that can live for five, 10 or 15 years to act as indicators of the levels of pollutants in the sea.

To look at how pollutants are building up in marine organisms in the short-term, the team is studying mussels. They are filter feeders and their soft parts accumulate certain metals from seawater, explains Perkins.

For a more long-term picture, the team is studying brown seaweed. Perkins explains: ’This seaweed gets all its nutrients from seawater, but it is not very good at regulating its uptake of metals from solution so it will take up zinc, cadmium, lead and copper. This makes it a very good monitor of seawater. A sample of seawater gives a snapshot of what was in the sea at that spot at that time, but seaweed is fixed and gives a measure of what is in the water over a period of time. If we are able to compare samples collected before the pumping operation with those collected at different periods after the pollution we can monitor the long term effects on the marine environment.’

Andrew Ball, a microbiologist from the University of Essex, UK, provides a different slant on environmental forensics. ’In the past, before we could identify soil microorganisms, we would need to isolate and culture them from soil samples. But this would only isolate one per cent of microorganisms,’ he explains. ’Now we use molecular techniques based on amplified ribosomal DNA. This means we can routinely characterise the dominant microorganisms in a sample without the need to wait for cultures to grow.’

First, the team extracts DNA or RNA from a soil sample, purifies it and then copies it using the polymerase chain reaction (PCR) technique. Further rounds of amplification produce large numbers of identical fragments where each fragment contains the DNA region of interest, Ball explains. The trick is to use electrophoresis to tease apart different strands, where each strand roughly equals one species or strain. As one gram of soil may contain 10 000-100 000 species, the team limits itself to about a hundred of the most dominant species.

Because different soils have a different bacterial barcode, Ball believes this technique could be used in traditional forensics to characterise soils and so determine whether a person or vehicle has been to a particular spot. Jackie Horswell’s group, at the Institute of Environmental Science & Research in Porirua, New Zealand, has conducted several tests to try to establish the usefulness of this approach. They made a shoe print in a field and tested the soil stuck to the shoe. Eight months later, they revisited the exact location of the print and took more soil samples. They found that the microbial profiles of soil from the print, and soil from the shoe tread were highly similar, even over a period of eight months.

Another test involved kneeling in a field. The team took soil samples from the impression and from the kneeler’s jeans. Ball reports that the soil profiles from the left and right knees were very similar, and were identical to those from the soil taken from the jeans. These profiles were also significantly different from the profile of a soil taken from a different region, he adds.

All the evidence seems to indicate that environmental forensics will soon see an explosion of interest in Europe. If the number of environmental forensic workshops and conferences is anything to go by, then environmental forensics is a rapidly evolving science. As Morrison points out, courses in the subject are being added to academic programmes throughout the world. Bangor University, for example, started the first degree course in environmental forensics in September 2003. Morrison predicts that within the next few years, there will be PhD courses on offer, too.


Maria Burke is a freelance science writer based in St Albans, Hertfordshire, UK