Surface Water Eutrophication

In Asia, surface water eutrophication also is greatly enhanced by phosphorus from detergents and this source of pollution is still of importance in many countries. 

Silage liquids, except the liquids from clover silage, contain rather a low amount of nitrogen (0.03-0.28%) and about half of this is in the ammonia form. From the aspects of nutrients the potassium content is also significant (0.10-0.37%) whereas the quantities of other nutrients (P, Ca, Mg) are very low. Silage liquids, however, have unfavourable effects particularly on stagnant surface waters (eutrophization). 

Excess nitrogen deposition contributes not only to acidification, but can also lead to the eutrophication of soils and surface waters. 

The excessive amounts of nitrogen and phosphorus as well as heavy metals migrate with water fluxes and enter into surface waters. This is accompanied by eutrophication of surface water bodies. 

Leonov, A. V., Stygar, O. V. (2001). Mathematical modeling of organogenic material biotransformation processes for studying the conditions of water eutrophication in the Caspian Sea surface layer. Water Resources, 28(5), 532-555... 

Figure 8.35 shows the redox state and acidity of the main types of seawaters. The redox state of normal oceanic waters is almost neutral, but they are slightly alkaline in terms of pH. The redox state increases in aerated surface waters. Seawaters of euxinic basins and those rich in nutrients (eutrophic) often exhibit Eh-pH values below the sulfide-sulfate transition and below carbonate stability limits (zone of organic carbon and methane cf figure 8.21). We have already seen (section 8.10.1) that the pH of normal oceanic waters is buffered by carbonate equilibria. At the normal pH of seawater (pH = 8.2), carbonate alkalinity is 2.47 mEq per kg of solution. 

Figure 835 Mean Eh-pH values for various types of seawaters. A = normal oceanic waters B = oxidized surface waters C = euxinic basins D = eutrophic waters. Dashed line field of natural waters according to Baas Becking et al. (1960).

The situation is more complex in the region of Asia and the Pacific. Water quality has many enemies there. First, sedimentation constitutes a major cause of pollution in Asian rivers, since sediment loads are four times the world average. Secondly, hazardous and toxic waste deteriorates the water quality. It is noteworthy that lead levels in Asia s surface water are about 20 times higher than those in OECD countries. Thirdly, eutrophication is faced due to the extensive use of fertilizers in the last 30 years. But the list of problems does not end here. Asian rivers contain three times as many bacteria from human waste as the world average. Finally, urbanization and the release of untreated sewage and industrial waste to the environment are expected to cause severe water pollution problems. 

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. 

Estimation of the effects of N deposition on aquatic systems is made difficult by the large variety of forms of N found in air, deposition, watersheds, and surface waters, as well as by the myriad pathways through which N can be cycled in terrestrial and aquatic ecosystems. These complexities separate N deposition from its effects and reduce our ability to attribute known aquatic effects to known rates of N deposition. The organization of this chapter reflects this complexity. Because an understanding of the ways that N is cycled through watersheds is critical to our understanding of N effects, I begin with a brief description of the N cycle and of the transformations of N that may occur in watersheds. I then discuss the two most likely effects of N deposition (acidification and eutrophication). 

Surface water half-life for all processes, except for dilution t,/2 = 0.5 h in stream, eutrophic lake and pond and t,/2 = 600 h in oligotrophic lake, based on transformation and transport of quinoline predicted by the one-compartment model (Smith et al. 1978) ... 

Hydrolysis k(neutral) = 1.6 x 10 4 Ir1 indicating that neutral hydrolysis is unimportant, rate constants of 7.5 x 10-3, 8.99 x 10, and 1.07 x 10 3 h 1 corresponded to half-lives of 92, 771 and 648 h in natural surface water samples from eutrophic pond, dystrophic reservoir and oligotrophic rock quarry, respectively (Saleh et al. 1982 quoted, Howard 1991)... 

Nitrate from fertilisers represents a very small flux but has major implications in terms of eutrophication of surface waters. 

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