The biological impacts of urban runoff waters
Shutes, Robert Brian Emmerson
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Introduction: My work with the Middlesex University Urban Pollution Research Centre has been conducted in the following areas: 1 Biological Monitoring of Urban Waters (Publications 1, 3, 5, 6, 25) Conventional biological methods and hydrobiological indices used for assessing water quality have been tested in urban streams and rivers and their limitations exposed. The impact of river engineering and physical disturbance on the substrate during storm events has been shown to influence significantly the index scores in addition to pollution impacts. The recommendation to compare biological with physico-chemical assessment of water quality has also been adopted by the National Rivers Authority. A model to predict the community diversity index score for urban stream macro invertebrate biota from recorded physico-chemical parameters was satisfactory for fairly clean waters and for moderate levels of pollution but not for serious levels of pollution (1). Reference streams and ponds in Trent Country Park on the fringe of North London were used for comparison with studies of the biota of urban waters (3,5). A system of river classification using a hydrobiological score system was proposed to complement the existing National Water Council system which was essentially based on chemical criteria (6). A study of the use of indicator organisms to monitor the impact of localised discharges of urban surface runoff and storm sewer overflows was commissioned by the Water Research Centre, the results of which are reported in paper no. 14. A review of the use of macroinvertebrates and plants as bioindicators in urban aquatic systems is included in publication 25. 2 Aquatic Ecotoxicology (Publications 3, 4, 5, 6, 7, 9, 11, 12, 14, 21, 24, 26, 28, 32, 34) 2.1 Heavy Metals Innovative methods have been developed for assessing heavy metal bioaccumulation in selected macro invertebrate species in urban waters. Traditionally, toxicity tests have been conducted in controlled laboratory conditions which do not simulate the natural environment. The use of caged macro invertebrates secured to the substrate in rivers, enables a more realistic determination of bioaccumulation and mortality rates to be made. The impact of storm events and chronic exposure to contaminated water and sediment has been investigated. At a time when new ecotoxicological tests are being introduced to the UK and the EC, the research has considerable potential application as a test for heavy metal impacts and the determination of environmental standards in freshwater. (The research has been sponsored by the Water Research Centre). VI Tissue concentrations of lead, cadmium, copper and zinc in selected macroinvertebrates collected from semi-rural and urban streams and ponds are reported in papers 3, 4 and 5. The relationship between urbanisation and macro invertebrate tissue, sediment and water metal concentrations and their spatial trends along the Salmon's Brook in North London is discussed in publication 6 and compared with the results from the A veiro Lagoon and its feeding rivers in North Portugal in paper 7. Tissue metal bioaccumulation in popUlations of caged Gammarus pUlex, Asellus aquaticus and Lymnea peregra in relation to ambient sediment and water metal concentrations, metal species bioavailability and organism feeding behaviour are discussed in publication 9. A comparison of mortality and metal uptake in aquatic macroinvertebrate species in field studies and laboratory experiments and a recommendation to reduce the length and lethal limit of the traditional 96 hour LC50 test is made in papers 11, 21, 24 and 32. The impact of storm sewer overflows from a sewage treatment works on caged macro invertebrates exposed to the discharges and to the receiving waters immediately downstream is reported in publications 12, 14 and 24. Principal component analysis was used to determine combinations of caged Aselius aquaticus tissue, sediment and water metal concentrations, precipitation volumes and antecedent dry periods which explained much of the variation in organism mortality and weight (28, 34). 2.2 Hydrocarbons (Publications 15 - 20, 29) Caged macro invertebrate species have also been used to determine hydrocarbon bioaccumulation in an urban stream and the Welsh Harp reservoir, a site of special scientific interest. Sediment and water hydrocarbon concentrations and macro invertebrate community diversity have been monitored along the stream and in the reservoir to investigate the impact of an oil boom. The development of biological and chemical techniques in this unique study of an urban freshwater wetland has led to considerable interest and further publications are planned. (The research has been sponsored by English Nature, formerly the Nature Conservancy Council). Publications 15 and 16 describe a baseline study of the ecotoxicological impacts resulting from oil pollution on the Welsh Harp and one of its receiving streams. Sediment and water concentrations of alkanes and P AHs and the tissue concentrations and temporal and spatial trends in selected caged macro invertebrates and fish are reported in publications 17, 18 and 19. The bioaccumulation of hydrocarbons by macro invertebrate species in laboratory tests and the corresponding mortality rates and their comparison with the results of field studies and controlling factors are discussed in publication 20. The results of the study are summarised in paper 29. vii 3 Aquatic Macrophyte Pollution Control (Publications 10, 13, 22, 23, 27, 31, 33, 35) Heavy metal uptake by the reedmace Typha latifolia, an aquatic plant species, has been investigated in urban wetlands and in greenhouse based studies. The research has shown a high level of tolerance by Typha to heavy metals and its biofiltration ability and creation of a sediment metal sink. It has led to the introduction of Typha in pioneering designs of constructed wetlands for highway runoff treatment in the UK. (The research is ongoing and is receiving sponsorship from industry and PCFC). A comparison of the water pollution control performance of Typha latifolia in the UK and Eicchomia crassipes in China is discussed in publication 10. Further details of the study of metal uptake in Typha latifolia and its associated sediment in the Welsh Harp and two ornamental ponds and a comparison with the results of a greenhouse based metal dosing experiment are given in papers 13 and 27 and summarised in 23 and 31. An analysis of the metal and hydrocarbon uptake and biofiltration ability of different species of aquatic macrophyte in an experimental pond receiving runoff from a car park in Washington State, USA is described in report 33.