Fertilizers algal bloom

In Chapter 28, we will consider further the effects of unintentional fertilization of coastal waters. These include development of hypoxia and blooms of harmful algae. Unfortunately, the size and persistence of coastal hypoxic zones and harmful algal blooms seems to be increasing worldwide. 

It s hard to overestimate the damage to the environment that has been wrought by agricultural intensification during the last half-century. Precious landscape features, such as prairies, wetlands, and old fencerows, have been destroyed on a massive scale. Overuse of fertilizers has polluted lakes and rivers, in many cases choking them almost to death through the proliferation of algal blooms and aquatic weeds. Pesticides are everywhere in... 

The mining of phosphate rock (mostly from terrestrially emplaced marine phosphorite deposits) for use as agricultural fertilizer has increased dramatically in the latter half of this century (F72). In addition to fertilizer use, deforestation, increased cultivation, urban and industrial waste disposal all have enhanced phosphorus transport from terrestrial to aquatic systems, often with deleterious results. For example, elevated phosphorus concentrations in rivers resulting from these activities have resulted in eutrophication in some lakes and coastal areas, stimulating nuisance algal blooms and promoting hypoxic or anoxic conditions harmful or lethal to natural populations (e.g., Caraco, 1995 Fisher et al., 1995 Melack, 1995). 

Many bodies of water become eutrophic when excess phosphate from detergents and fertilizer washes in. This overenrichment results in undesirable algal blooms. Agents that complex phosphate may allow it to be removed from treated wastewater, recovered, and reused. The first com plexing agent (7.22) (where X = S) complexes dihydrogen phosphate with a K of 820 and acetate with a K of 470 chloride, hydrogen sulfate, nitrate, and perchlorate are held much more weakly.91 The Kfor the second one with phosphate (7.23 where R is H) is 12,000.92... 

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