Micro-organics

Understanding how micro-organic contaminants behave in aquatic systems and assessing their impact on ecosystems.

Why should we be interested?

The contamination of the natural environment with a range of natural and synthetic chemicals is an inevitable consequence of human development. The magnitude of that contamination is linked to the population density and industrial development of the land mass. According to this simple arithmetic, the UK natural environment is likely to receive a greater chemical challenge then many other countries in Europe and North America. This challenge is likely to be most striking in the UK watercourses. Not being part of a large continent, the catchments are relatively small, with limited dilution available. Many of the major urban centres in the UK are inland, and their sewage discharges into many of these water courses are of limited dilution.

The nature of the chemical challenge to the UK is changing. Changes in industrial economics, environmental regulations, and improved sewage treatment means that there will be far less exposure to the persistent and acutely toxic chemicals than in the past. Instead we now have an enormous and continually increasing consumption of chemicals from the human (and farm animal) population, ranging from cleaning products to pharmaceuticals. A proportion of these chemicals will escape treatment and be discharged into the environment. The Royal Commission on Environmental Pollution (2003) described this as "an experiment with all living things as the subject". In most cases we don’t know how these chemicals will behave, or if and how they may be harmful to aquatic ecosystems.

Which micro-organic chemicals are we concerned about?

Projects

We have examined how farm applied pesticides can reach groundwater, and at what rate they are degraded by the natural subsurface bacteria. In the UK the principal cause of endocrine disruption in fish is believed to be steroid oestrogens and we have investigated how these behave in water. With the exception of ethinyloestradiol they are readily biodegradable. The constant daily input of oestrogens and short residence times in British rivers still mean that in many locations elevated concentrations will occur that could effect fish health.

But where are these oestrogens, and at what levels will they be found? It is not practical to try to measure the steroid oestrogen concentration in every effluent and river reach. As an alternative, new prediction models have been developed and tested for steroid oestrogens. At the heart of the prediction model is a calculation of the quantity a typical human will excrete every day. When the predicted amount eliminated by wastewater treatment plant is factored in, together with the wastewater flow and receiving water dilution, then steroid oestrogen concentrations can be predicted. The combined concentrations can then be converted into high, medium and low risk factors for the receiving waters. Through collaboration with biologists, we can then attempt to predict the extent to which such a mixture of endocrine disrupters might affect fish.

We are collaborating with the Oxford University Engineering Sciences Department to develop cost-effective technology to remove oestrogens from sewage effluent. This has now reached the stage of field testing in large tanks at a real sewage works.

Some recent publications

Johnson, A.C., Belfroid, A. and Di Corcia, A. (2000). Estimating steroid oestrogen inputs to activated sludge treatment works and observations on their removal from the effluent. The Science of the Total Environment 256, 163-173.

Johnson, A.C., Besien, T.J., Bhardwaj, C.L., Dixon, A., Gooddy, D.C., Haria, A.H. and White, C. (2001). Penetration of herbicides to groundwater in an unconfined chalk aquifer following normal soil applications. Journal of Contaminant Hydrology 53, 101-117.

Johnson, A.C. and Sumpter, J.P. (2001). Removal of endocrine disrupting chemicals in activated sludge treatment works. Environmental Science & Technology 35, 4697-4703.

Johnson, A.C., White, C., Bhardwaj, C.L. and Dixon, A. (2003). The ability of indigenous microorganisms to degrade isoproturon, atrazine and mecoprop within aerobic UK aquifer systems. Pesticide Management Science 59, 1291-1302.

Johnson, A.C. and Jürgens, M.D. (2003). Endocrine active industrial chemicals: Release and occurrence in the environment. Pure and Applied Chemistry 75, 1895-1904

Johnson, A.C. and Williams, R.J. (2004). A model to estimate influent and effluent concentrations of estradiol, estrone and ethinyloestradiol at sewage treatment works. Environmental Science & Technology 38, 3649-3658.

Johnson, A.C., Llewellyn, N., Smith, J., van der Gast, C., Lilley, A., Singer, A andThompson, I.P. (2004). The role of microbial community composition and groundwater chemistry in determining isoproturon degradation potential in UK aquifers. FEMS Microbiology Ecology 49, 71-82.

Johnson, A.C., Aerni, H-R., Gerritsen, A., Gibert, M., Giger, W., Hylland, K., Jürgens, M., Nakari, T., Pickering, A., Suter, M.J-F., Svenson, A. and Wettstein, F.E. (2005). Comparing steroid estrogen, and nonylphenol content across a range of European sewage plants with different treatment and management practices. Water Research 39, 47-58.

Jürgens, M.D., Holthaus, K.I.E.,Johnson, A.C., Smith J.J.L., Hetheridge, M. and Williams, R.J. (2002). The potential for estradiol and ethinylestradiol degradation in English rivers. Environmental Toxicology and Chemistry 21, 480-488.

Wood, M., Issa, S., Albuquerque, M. and Johnson, A.C. (2002). Spatial variability in herbicide degradation in the subsurface environment of a groundwater protection zone. Pesticide Management Science 58, 3-9.

Holthaus, K.I.E., Johnson, A.C., Jürgens, M.D., Williams, R.J. and Carter, J.E. (2002) The potential for estradiol and ethinylestradiol to sorb to suspended and bed-sediments in some English rivers. Environmental Toxicology and Chemistry 21, 2526-2535.

Williams, R. J., Johnson, A. C., Smith, J. J. L. and Kanda, R. (2003) Detailed investigation of steroid oestrogen profiles along river stretches arising from sewage treatment works discharges. Environmental Science and Technology 37, 1744-1750.

Sumpter, J.P. and Johnson, A.C. (2005). Lessons from endocrine disruption and their application to other issues concerning trace organics in the aquatic environment. Environmental Science and Technology (in press).