title: Potential internal loading of phosphorus in a wetland constructed in agricultural land.
abstract: Wetland construction on agricultural or dairy lands could result in solubilization of phosphorus (P) stored in soils and release to the water column. To study the extent of P flux during the start-up period of a constructed wetland, intact soil-cores from areas used for dairy operations, in Okeechobee, Florida, USA were obtained and flooded with adjacent creek water. In the first 28-day hydraulic-retention period, P concentration in the water column increased several fold due to rapid P flux from impacted soils. A continuous decrease in P flux to the water column until the third hydraulic retention cycle (initial influent P concentration 0.2 mgL(-1)), and constant thereafter suggest that the effect of initial influent P upon long-term P flux from soils could be limited. The initial release maybe due to high concentration of labile P in impacted soils; however, slow dissolution of relatively stable P pools could maintain a steady flux, well above of that observed from non-impacted soils. Water soluble P along with double acid-extractable magnesium explained 76% of the variability in cumulative P flux to the water column. Apparently, co-occurrence of active adsorption-desorption phenomena due to independent maintenance of equilibrium by individual P compounds regulates P dynamics of the water column. The results indicated that equilibrium P concentration of the water column of the wetland would be above 1.3 mgL(-1), which is well above the targeted P level in the water column of the Lake Okeechobee, one of the main water bodies in the area (0.04 mg PL(-1)). This suggests construction of wetlands in agricultural lands could result to substantial internal P loading. However, preventative measures including chemical amendments, establishment of vegetative communities or flushing the initially released P may potentially stabilize the system, and maintain P removal efficiency.
authors.affiliation: Soil and Water Science Department, IFAS, University of Florida, 106 Newell Hall, P.O. Box 110510, Gainesville, FL 32611-0510, USA. hari@mail.ifas.ufl.edu
authors.forename: H K
authors.initials: HK
authors.lastname: Pant
authors.forename: K R
authors.initials: KR
authors.lastname: Reddy
mesh_terms: D000818:Animals; D002417:Cattle; D003612:Dairying; D017753:Ecosystem; D004784:Environmental Monitoring; D010758:Phosphorus / Q000032:analysis / Q000737:chemistry* / Q000302:isolation & purification; D010944:Plants; D012995:Solubility; D014873:Water Pollutants / Q000032:analysis* / Q000302:isolation & purification; D014876:Water Pollution / Q000517:prevention & control; D014881:Water Supply
chemical_list: D014873:Water Pollutants; D010758:Phosphorus