Nutrients, Toxins and Pollutants

This chapter is concerned with the different types of wetland soil as sources, sinks and transformers of nutrients, particular nutrient deficiencies and mineral toxicides that commonly arise following submergence, and the fate of pollutants that are commonly added to submerged soils, both accidentally and intentionally. 

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Although both types of pollution sources present a serious problem, point sources can be controlled, at least in principle. Nonpoint sources, however, are difficult to control. Sources and types of nonpoint pollution in impacted rivers and lakes in the United States include agriculture, land disposal, construction, hydromodification, urban runoff, and silviculture, resource extraction. The pollutants in these sources include sediment, nutrients, toxins, pesticides, salinity, and acidity (Institute, 1988). Looking at these lists, one can easily deduce that solvents play roles in the pollution of water. 

Urban runoff is the greatest cause of surface water pollution in many parts of the world. Toxins contained in runoff include pathogens, nutrients (nitrate and phosphate). 

On the other hand, more recent studies have been designed to evaluate these hypotheses as they relate to (1) natural communities as contrasted to pure cultures, (2) cell densities more characteristic of natural ecosystems than those bacterial densities commonly used in tests of pure cultures, (3) synthetic compounds acted on by only a few rather than a diversity of microbial genera or species, and (4) compound concentrations which are characteristic of environmental pollutants rather than organic nutrients included in culture media. In general, all these explanations are related mainly to (1) proliferation of small populations, (2) presence of toxins, (3) predation by protozoa, and (4) appearance of new genotypes [ 101,104,106 -108,110,111 ]. 

In both cases, a nutrient solution (blood or polluted air or water) passes through and over ceUs and is changed by the action of the colony of cells. That action removes the toxin from a pollutant. The fact that the fluid passing through the polyurethane... 

An excess of nutrients, such as phosphorus and nitrogen in polluted water, will lead to an excessive growth of plant matter in waterways and algal blooms. Besides clogging waterways and adding toxins, this extra plant material contributes to the BOD of the water. 

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