Diverted Mississippi River sediment as a potential phosphorus source affecting coastal Louisiana water quality

Abstract

Mississippi River water and associated sediment are seasonally diverted into Louisiana coastal basins to restore historic hydrologic and salinity regimes and to slow or reverse the widespread wetland loss. More river diversions are planned; however, very little research has been conducted on the potential source of phosphorous (P) of these sediments transported by the Mississippi River into the coastal areas through these diversions. In addition, the sediments have the potential to undergo changes in redox status when these significant flooding events occur. Therefore, we examined the effect of sediment redox condition on P release from newly deposited Mississippi River sediment. Sediment was collected from Big Mar Lake, the receiving water body of the Caernarvon diversion structure, through which river water is diverted into the Breton sound estuary. Sediment suspensions were incubated in the laboratory under reducing conditions, and the relation of redox conditions to P release was determined. Soluble reactive P (SRP), dissolved organic P (DOP), Fe, and Mn concentrations increased with decreasing sediment redox potential. The SRP and DOP concentrations increased 32 -and 8-fold during 20 days of anaerobic conditions. The increase in SRP and DOP availability was significantly correlated to an increase in ferrous iron with no significant relationship with Al, Ca, or Mg. While the vast majority of studies on nutrients associated with the Mississippi River diversions have focused on excess inorganic nitrogen forms (primarily NO 3 ) in the river water, this study is one of the first to demonstrate that upon reduction associated with prolonged flooding, the diverted Mississippi River suspended sediment can be a significant source of available P to the coastal basin.

Spatial and Seasonal Distribution and Transportation of Different Forms of Phosphorus in the Middle Reaches of the Yarlung Zangbo River

“…As mentioned above, SP, Fe-P, Al-P, and OP, classified in this research, are mainly derived from exogenous inputs. Ca-P and Oc-P are mainly produced locally [9][10][11][12]. Figure 7a shows that the concentration of P of this area is mainly self-generated.…”

“…IP can be further divided into soluble phosphorus, aluminum-bound phosphorus, calcium-bound phosphorus, iron-bound phosphorus and occluded phosphorus (hereafter referred to as SP, Al-P, Ca-P, Fe-P, and Oc-P, respectively). The sum of the concentrations of all forms of P is the total phosphorus (TP) concentration.The morphology of P of sediments can help us distinguish the sources of P [9,10]. According to previous research [11,12], by the method used in this research, SP, Al-P, Fe-P, and OP are considered as "external P," which may came from human activities, such as industrial wastewater, domestic sewage, and the abuse of phosphate fertilizer.…”

“…The morphology of P of sediments can help us distinguish the sources of P [9,10]. According to previous research [11,12], by the method used in this research, SP, Al-P, Fe-P, and OP are considered as "external P," which may came from human activities, such as industrial wastewater, domestic sewage, and the abuse of phosphate fertilizer.…”

Phosphorus speciation and sedimentary phosphorus release from the Gulf of Mexico sediments: Implication for hypoxia

“…Therefore, the continental margins are key zones for deposition and regeneration of P (Lebo and Sharp, 1992;Conley et al, 1995;Zhang et al, 2004). Zhang et al, 2012). Organic matter decomposition and iron oxides reduction can remobilize P from sediment and the remobilized P may precipitate as carbonates or sorbed onto iron oxides (Ingall and Jahnke, 1994;Filippelli and Belaney, 1996;Paytan and McLaughlin, 2007).…”

Comparative Study of Three Two-Stage Hybrid Ecological Wastewater Treatment Systems for Producing High Nutrient, Reclaimed Water for Irrigation Reuse in Developing Countries

“…It is well known that TP removal in constructed wetlands can be complicated due to the coupling of both organic and inorganic removal mechanisms [27] regeneration of P from organic matter back into the water column [28,29]. As a result many single treatment systems and hybrid systems have reported low TP removal rates [30,31]; in a VF-HF system with gravel, a removal of only 21% was achieved [11].…”