Phosphorus retention and remobilization along hydrological pathways in karst terrain.
Karst landscapes are often perceived as highly vulnerable to agricultural phosphorus (P) loss, via solution-enlarged conduits that bypass P retention processes. Although attenuation of P concentrations has been widely reported within karst drainage, the extent to which this results from hydrological dilution, rather than P retention, is poorly understood. This is of strategic importance for understanding the resilience of karst landscapes to P inputs, given increasing pressures for intensified agricultural production. Here hydrochemical tracers were used to account for dilution of P, and to quantify net P retention, along transport pathways between agricultural fields and emergent springs, for the karst of the Ozark Plateau, midcontinent USA. Up to ∼ 70% of the annual total P flux and ∼ 90% of the annual soluble reactive P flux was retained, with preferential retention of the most bioavailable (soluble reactive) P fractions. Our results suggest that, in some cases, karst drainage may provide a greater P sink than previously considered. However, the subsequent remobilization and release of the retained P may become a long-term source of slowly released "legacy" P to surface waters.
Centre for Ecology & Hydrology, Wallingford OX10 8BB, U.K.
Helen P
HP
Jarvie
Andrew N
AN
Sharpley
Van
V
Brahana
Tarra
T
Simmons
April
A
Price
Colin
C
Neal
Alan J
AJ
Lawlor
Darren
D
Sleep
Sarah
S
Thacker
Brian E
BE
Haggard
D000383:Agriculture; D005618:Fresh Water / Q000737:chemistry; D060587:Groundwater / Q000737:chemistry; D062070:Hydrology; D010758:Phosphorus / Q000032:analysis / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000032:analysis / Q000737:chemistry*
D014874:Water Pollutants, Chemical; D010758:Phosphorus