The effects of particle breakage and abrasion—from simulated fluvial transport,on phosphorus sorption by two soils

Phosphorus sorption studies were carried out on particle size fractions of soils collected from the walls of gullies through a granitic and a sedimentary soil, as well as on particle size classes derived from breakage and abrasion of the 500 to 1400 μm components of these soils. Sorption of phosphorus by the particle size classes of the sedimentary soil was much greater than those of the granite soil, and this also applied to the particles derived from breakage and abrasion. For the original sedimentary soil, sorption of phosphorus by the particle size components was strongly associated with the iron content and less strongly associated with the aluminium content and this also applied to the particles derived from breakage and abrasion. For the granitic soil these relationships were much less precise. A period of vigorous mixing, after 165 hours of gentle mixing, caused release of a proportion of the sorbed phosphorus from all particle sizes of the original granitic soil and for most of the breakage/abrasion derived particles. The released phosphorus was re‐sorbed during a subsequent 48 hour period of settling. Relationships were evident between labile P and sorbed P for the particle size classes of the soils and treatments tested. Because particle size, lithology of the transported sediments and flow dynamics affect the distribution of phosphorus between water and sediments, they can also be expected to effect bio‐availability of phosphorus. Particle breakage and abrasion during sediment transport is another factor likely to influence the bio‐availability of P. Copyright © 1999 John Wiley & Sons, Ltd.