My Newcastle University students are in the final throes of writing up their assignment on the ecological health of the Ouseburn, a small tributary of the Tyne that flows through Newcastle, so I could not resist taking these photographs as my flight from Amsterdam to Bucharest was sprayed with de-icer. The primary point of the assignment is to make my students better scientists, but I like to also use it to remind them that they can never wholly isolate themselves from the systems that they study. Most of my students live in the Ouseburn catchment so they are all contributing to the problem that they are simultaneously trying to solve. And, as I set out this morning on my flight to Amsterdam, I watched de-icer being sprayed and remembered that this, too, may find its way into the Ouseburn. We are all polluters. And, these days, the polluter pays …
Newcastle Airport plays a big role in the story of the Ouseburn. It occupies quite a large site in the upper part of the catchment and has grown over the years from the humble structure which I remember from the 1980s to a major regional airport. The environmental impact increased as the airport grew in size, particularly in the winter as de-icer drained from the ‘planes, via a small tributary, into the Ouseburn. The graphs below illustrate this very well. The original de-icer was a mixture of urea and glycol. Urea breaks down rapidly to ammonia and, at its peak in 1993, the annual average concentration in this tributary was 35 milligrams – sixty times more than the current target for “good status”. Over six tonnes of urea could be applied in a single day at this time.
Trends in concentrations of nitrogen as ammonium in the Ouseburn over time. Woolsington is upstream of the airport, Airport tributary (Abbotswood Burn) receives runoff from Newcastle Airport and Jesmond Dene is about 10 km downstream from the airport. Closed symbols are annual means of data collected by the National Rivers Authority and Environment Agency; open symbols are means of data collected and analysed by Newcastle University Geography students in October (once also in February) of each year. The lower dashed line is the UK environmental standard for ammonium-N to support “good ecological status”; the upper dashed line is the threshold between “poor” and “bad” status.
The “yin” of serious pollution in the Ouseburn has, however, been offset by the “yang” of environmental management as the authorities circled around the problems, gradually learning about the river and using regulation and legislation to tackle the issues. So the graph also shows a rapid decline in ammonia concentrations in the river after 1992 as urea was replaced by a different de-icer, this time based on potassium acetate. Ammonia concentrations are now generally well within the limits required to support good status, so we should have expected to see organisms characteristic of healthy streams to re-appear.
It has not happened, alas. As is usually the way, pollution problems are multilayered, like the skins of an onion, and peeling away the first and most obvious problem only reveals further issues lurking below. In the case of the Ouseburn, the switch from urea to (glycol) created a new problem, as microorganisms in the river were able to use this organic compound as a source of energy, sucking vital oxygen out of the water in the process. You can see this in the second graph, which shows biological oxygen demand (BOD). Note how it peaks in the years just after the switch from urea. Note, too, how values fluctuate (dependent, presumably, on the severity of the winter) and, again, how the peaks exceed the current target for “good status”. But, on a positive note, more recent values are much lower, as the airport now has better facilities for handling surface water drainage.
Trends in biological oxygen demand (BOD) in the Ouseburn over time. Details as for the graph showing ammonium-N.
Even after this, however, the river is still in a state that is far from acceptable. The final graph in this post shows the state of the invertebrates in the Ouseburn (expressed as average score per taxon). This has gradually crept up over the years but, as can be seen, is still not yet at “good status”. When we empty the contents of our pond nets into trays and take a look, we see lots of pollution-tolerant water hoglouse (Asellus aquaticus) and freshwater shrimp (Gammarus pulex), bloodworms (Chironomous riparius) and leeches. There are very few of the caddis flies, stone flies or may flies that we associate with clean water (with the exception of the relatively tolerant Baetis rhodanii). There are more layers of this onion that still need to be peeled away and I will return to these in a future post.
I will finish where I began: sitting on an aeroplane that is being sprayed with de-icer. I’m an ecologist and my particular specialism means that I often need to travel around Europe. Flying is the only practical way of doing much of this but, in the process, I become part of the problem whilst hoping that I am part of the solution. I also teach part-time in a Geography department along with colleagues whose professional calling often makes international travel a necessity. It makes for some uneasy moral choices. At worst, we develop a tough veneer that insists that the good we do far outweighs the negative effects of our carbon footprints. At best … well, perhaps that is not for me to say. Maybe simply remembering that our travels mean that we are part of the problem should make us approach the systems we study with a little more humility and rather less sanctimoniousness …
Turnball, D.A. &Bevan, J.R. (1995). The impact of airport de-icing on a river: the case of the Ouseburn, Newcastle upon Tyne. Environmental Pollution 88: 321-332.