Water Pollution Through Soil Erosion

Have we ever though how nitrogen and phosphorus enters into a water body?

How these nutrients can deteriorate water-quality?

Generally, when farmers utilize inorganic chemical fertilizers on their field, they apply much more than the crop requirement. Thus excess nitrogen, phosphorus and other nutrients get washed away by the rain water and enters into the water bodies by soil erosion and runoff. 

The excess amount of nutrients accelerate the growth of macro and micro algae and aquatic plants which are usually limited by insufficient concentrations of either nitrogen or phosphorus in the water. The growth of these organisms explode when a water body contains sufficient amount of nutrients. They lead to numerous undesirable changes in aquatic ecosystem. In most freshwater, phosphorus is the limiting nutrient that can set off eutrophication and in salt water system nitrogen can cause eutrophication. 

Eutrophication - water pollution

How can eutrophication damage a water body?

Eutrophication is simply the unwanted growth of algae. Unwanted growth of algae decreases the dissolved oxygen in the water body and increase the biological oxygen demand (BOD). Besides, when they die, they add organic matter to the water. The addition of organic matter is the energy source for the micro organisms and bacteria. Thus the aerobic bacteria use up the rest dissolved oxygen and after consuming all of the dissolved oxygen, anaerobes take place and start decomposing. The anaerobic decomposition of those organic matter produces methane, hydrogen sulfide and other toxic gases which can lead to massive death and extinction of fish.

Eutrophication can transform clear, oxygen rich water into cloudy, oxygen poor, foul smelling, bad tasting and possibly toxic water. Eutrophic conditions favor the growth of Cyanobacter, blue-green algar that are mostly undesirable food for zooplankton, a major food source for fish.

Soil erosion - eutrophication

Other problems

In addition to stimulating eutrophication, nitrogen in the form of dissolved ammonia gas can be directly toxic to fish. Environmental problems caused by nitrogen are mainly associated with the movement of nitrate through drainage water. This excess nitrate can enter into the groundwater. It may also reach domestic wells.

The quantity of nitrate lost in drainage water depends on the rate of water leaching through the soil and the concentration of nitrates in that drainage water. Precipitation and irrigation rates, along with soil texture, structure influence the leaching rate. The sandy soils generally have high drainage and from this type of soils the leaching losses are huge.

What to do?

Nutrient management plan should be included in every land so check the losses and pollution. It usually focuses on nitrogen and phosphorus, the two principal nutrients that can cause ecological damage to aquatic systems. Fundamentally, the plan attempts to balance the inputs of these nutrients with their desirable outputs so as to avoid their undue accumulation on the land and to keep undesirable outputs to ecologically acceptable levels. Many scientists and policymakers believe such plans, whether voluntary or required by law, are the best and most fair approach available to limiting the eutrophication of natural waters caused by enterprises that grow plants on the land. Many land owners report that the nutrient management planning process actually saves their money by reducing their previously nrecognized waste of expensive nutrients.