**3. Phosphorous in water**

In the 1960s, it was discovered that aquatic ecosystems were experiencing high levels of phosphorus. Further scientific investigations revealed that this phosphorus was originating from livestock farms and concentrated agriculture located kilometers away from these water ecosystems. These areas, which are the source of phosphorus input to aquatic ecosystems, are known as concentrated polluting points. During that decade, due to advancements in technology and the creation of laws limiting the risk of pollution from these points, identifying and controlling these sources became easier. However, today, the transfer of phosphorus from unknown agricultural sources is a serious and worrying threat to the environment, as it is practically impossible to control these sources. The phosphorus eventually reaches water reservoirs, causing many problems. This results in exorbitant fees for using these waters [17, 18].

Phosphorus is lost from watersheds due to soil erosion and washing and is transferred to aquatic ecosystems through surface and subsurface runoff. When the runoff reaches surface water, the washed (dissolved) elements along with the eroded materials are emptied into these waters, creating certain problems. Sediments fill the reservoirs of dams, corrode water treatment facilities, and reduce the quality of drinking water. The elements present in these waters cause the phenomenon of enrichment, which cannot be ignored because it can cause many problems. Water enrichment causes toxic substances to be released from aquatic organisms into the water, leading to diseases in humans, with neurological problems being the most common in recent decades. The transfer of phosphorus to surface waters, deposition, and release of phosphorus from sediments into the water causes the phenomenon of surface water enrichment [19–21].

Phosphorus losses are typically observed in the following three ways in the field [22]:

a. Dissolved phosphorus and/or phosphorus bound to solid soil particlessuspended in water-created by erosion and accompanied by runoff flows, which are transferred to surface waters such as rivers and lakes.


On the other hand, the transfer of phosphorus from topsoil to surface and subsurface waters can be summarized in three mechanisms:
