Eutrophication control

The most commonly used physical method for long-term eutrophication control in lakes is that of artificial destratification. This method is well tried and understood and uses either jetted water or compressed air bubbles to break down the lake stratification in the summer months. Algal growth is also affected by an increase in circulation. This is due to the artificial shading effect which results from the algae spending less time near the surface and consequently less time in the light. This technique also reduces the redox-dependent phosphorus release from sediments because the sediment surface remains aerobic. 

In order to provide a realistic approach to eutrophication control, the NRA has developed a framework for gathering the scientific evidence and for presenting the relevant information needed for consultation with all parties involved in resolving the problems. This framework includes the production of Action plans for each water on a case by case basis. The principal reason for using this approach is because the NRA is attempting to persuade external... 

Once the options have been clearly defined it will be necessary to carry out a cost-benefit analysis of each option. This has two main objectives. First, the overall cost of the project will need to be assessed to determine whether or not it is financially viable and, second, to ensure that those who will be required to incur expenditure are fully aware of the commitment needed. The financial benefits to users of the waters for recreation, fisheries, navigation, etc., are relatively easy to determine, but monetary valuation of the environmental benefits such as conservation and general amenity will be more difficult to define. As yet this aspect of the cost-benefit analysis has not been fully developed in the UK. Having determined a range of options and costs for eutrophication control in a particular catchment, consultation on the details of the Action plan with all those involved is needed before any plan can be implemented. 

It is only following the collection and collation of nutrient data from all sources, including agriculture, the appreciation of control options, and the development and implementation of Action plans , that significant progress will be made with eutrophication control in the UK. 

G.A. Codd, Cyanobacterial toxins, the perception of water quality and the prioritization of eutrophication control, Ecol. Eng., 16 (2000) 51-60. 

Most lakes affected by eutrophication will also have significant amounts of phosphorus in their sediments, which can be recycled into the water column (Section 4). The control of this source can be achieved by treating the sediments with iron salts or calcite to bind the phosphorus more tightly into the sediments. These methods have been used to some effect, but consideration has to be given to the quality of the materials used and whether or not the lake can become de-oxygenated in the summer. In the latter case this can be overcome by artificial de-stratification. 

Physical controls are generally only applicable in lakes. The infinence of river morphology on eutrophication is not sufficiently well understood to be used effectively. The exception to this would be the short-term use of high flow to reduce the retention time to levels which limit growth rates of nuisance species such as cyanobacteria. 

The above description of eutrophication has illustrated the complex nature of the problem, particularly in relation to the influence of nutrients, the multiplicity of sources of phosphorus and the spectrum of its bio-availability. Clearly, the most effective long-term solution to many of our eutrophication problems will be to reduce the nutrient load to affected waters. However, it has also been shown that, because the concentrations of available phosphorus required to impose a control on primary production is very low (e.g. 5-10/rgU total dissolved phosphorus), the reduction of nutrients from any one source alone is unlikely to be effective. 

In many ways, both Canada and the United States continue to be involved in a unique experiment of co-operative management of serious environmental issues which plague a shared international resource. Despite the institutional complexity and the history of abuse that man s activities have wrought on the Great Lakes, the experiment to restore and protect them has had several successes typhoid and cholera were eradicated eutrophication problems are now largely under control and where adequate control programs for toxic chemicals have been implemented and enforced (e.g., mercury, DDT, PCBs), there have been associated declines in concentrations in the lakes. These successes have been due in no small way to the spirit of co-operation that has continued to exist between Canada and the United States and the unique institutional arrangements entered into by the two countries. 

Bruce, J.P. The Control of Eutrophication, Technical Bulletin No. 26, Inland Waters Branch, Dep. Energy Mines and Resources, Ottawa, Canada, 1970, lOp. 

Cyanides can be fatal to fish at <1 ppm. Because of concern over the possible in vivo conversion of nitrate into carcinogenic nitrosamines, the nitrate content of drinking water must be strictly controlled. Nitrate and phosphate pollution can also cause eutrophication in still or slow-moving warm waters by stimulation of algae growth in the presence of... 

Schachtman DP, Reid RJ, Ayling SM (1998) Phosphorus uptake by plants from soil to cell. Plant Physiol 116 447-453. doi http //www.plantphysiol.org Schindler DW (1974) Eutrophication and recovery in experimental lakes implications for lake management. Science 184 897-899. doi http //www.sciencemag.org/cgi/content/abstract/184/4139/897 Schindler DW, Hecky RE, Findlay DL, Stainton MP, Parker BR, Paterson MJ, Beaty KG, Lyng M, Kasian SEM (2008) Eutrophication of lakes cannot be controlled by reducing nitrogen input results of a 37-year whole-ecosystem experiment. Proc Natl Acad Sci USA 105 11254-11258. doi http //www.pnas.org/content/105/32/l 1254.abstract Scott JT, Condron LM (2003) Dynamics and availability of phosphorus in the rhizosphere of a temperate silvopastoral system. Biol Fert Soils 39 65-73 Shane MW, Lambers H (2005) Cluster roots a curiosity in context. Plant Soil 274 101-125. doi http //dx.doi.org/10.1007/s 11104-004-2725-7... 

In this case, permeability depends only on factors that are outside the organism. Such a scenario might occur in an eutrophic lake where metal speciation is controlled by natural organic ligands forming inert complexes. 

His 40+ publications have dealt with biogeochemical processes that control the alkalinity of surface waters, the geochemisty of dilute seepage lakes, sediment chemistry, the interpretation of water-quality trends, regional analysis of water quality, modeling lake eutrophication, lake management, reservoir water quality, and nonpoint source pollution. He recently joined the faculty of the Department of Civil Engineering at Arizona State University. 

The potential for N deposition to contribute to the eutrophication of freshwater lakes is probably quite limited. Eutrophication by atmospheric inputs of N is a concern only in lakes that are chronically N-limited. This condition occurs in some lakes that receive substantial inputs of anthropogenic P and in many lakes where both P and N are found in low concentrations (e.g., Table III). In the former case the primary dysfunction of the lakes is an excess supply of P, and controlling N deposition would be an ineffective method of water-quality improvement. In the latter case the potential for eutrophication by N addition (e.g., from deposition) is limited by low P concentrations additions of N to these systems would soon lead to N-sufficient, and phosphorus-deficient, conditions. The results of the NSWS shown in Table III, for example, can be used to calculate the increase in N concentration that would be required to push N-limited lakes into P limitation (assuming total P concentrations do not change). An increase of only... 

Measurements of S cycling in Little Rock Lake, Wisconsin, and Lake Sempach, Switzerland, are used together with literature data to show the major factors regulating S retention and speciation in sediments. Retention of S in sediments is controlled by rates of seston (planktonic S) deposition, sulfate diffusion, and S recycling. Data from 80 lakes suggest that seston deposition is the major source of sedimentary S for approximately 50% of the lakes sulfate diffusion and subsequent reduction dominate in the remainder. Concentrations of sulfate in lake water and carbon deposition rates are important controls on diffusive fluxes. Diffusive fluxes are much lower than rates of sulfate reduction, however. Rates of sulfate reduction in many lakes appear to be limited by rates of sulfide oxidation. Much sulfide oxidation occurs anaerobically, but the pathways and electron acceptors remain unknown. The intrasediment cycle of sulfate reduction and sulfide oxidation is rapid relative to rates of S accumulation in sediments. Concentrations and speciation of sulfur in sediments are shown to be sensitive indicators of paleolimnological conditions of salinity, aeration, and eutrophication. 

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