Effects of Limestone on the Dissolution of Phosphate From Sediments Under Anaerobic Condition

Abstract

This paper describes a study on the role of limestone on the dissolution of phosphates when phosphate-containing sediments are put under anaerobic conditions. Anaerobic decomposition of organic substances produces both organic acids and carbonic acids which in turn could accelerate the dissolution of the phosphates. If limestone coexisted, both phosphate and limestone would compete as receptors of hydrogen ions so as to affect the dissolution of phosphate. A small quantity of calcium hydroxyapatite, alone or mixed with limestone powder, was put in contact with an aqueous solution of acetic acid or carbonic acid and the variations in phosphate concentration were determined over time. The results showed that the phosphate concentration was remarkably low in the case of limestone presence, in comparison with the case of limestone absence. This signifies that the coexistence of limestone suppresses the dissolution of phosphate by organic acid and/or carbonic acid. Separate experiments conducted by developing an anaerobic condition, after mixing lake sediments with dried leaves and limestone, allowed us to observe that the existence of limestone suppressed the dissolution of phosphate. It seems that the limestone acts as a material sacrificing to the leaching of hydrogen ions from the acids produced under anaerobic conditions. These results show that the application of limestone might be a useful measure to prevent deterioration of water quality through eutrophication, by breaking the internal loading of phosphates in eutrophic water bodies.

Trace Elements and REY in the Muschelkalk Limestones of the Opole Silesia in Poland

“…If limestone coexisted, both phosphate and limestone could compete as receptors of hydrogen ions. They affect the dissolution of phosphate (Kim and Park 2008). Mn usually substitute Ca in carbonate minerals.…”

The resin transfer technique: An application to insect fossils in laminated limestones of the Crato Formation (Lower Cretaceous) of north-east Brazil

“…If this method were applied to arthropod fossils, the fossil may disintegrate during resin dissolution or be damaged during mechanical preparation. Additionally, vertebrate fossils are often preserved almost entirely in calcium phosphate and so 'spent' acetic acid (containing calcium acetate) or calcium orthophosphate must be added to prevent damage to the fossil during matrix dissolution (Kim and Park, 2008;Bonde and Leal, 2015). Although the insect fossils used here appeared to be preserved almost entirely in goethite, many later revealed internal soft-tissue preservation in apatite.…”

“…Here, the guidelines for using 'acetate soup', as outlined by Jeppsson et al (1985), are followed albeit with the 'topping up' solution composed of 20% 'spent' acetic acid (containing calcium acetate) and 80% 'fresh' acetic acid. On the rare use of hydrochloric acid, a similar 'soup' of spent acid and fresh acid can be used as a buffer, albeit using spent hydrochloric acid (or calcium orthophosphate) (Kim and Park, 2008;Bonde and Leal, 2015). A buffer was not required for the initial immersion of a specimen in acetic acid, as these vulnerable fossil tissues were not yet exposed.…”

“…This can generally be ignored, unless it accumulates to a level where it may contact the fossil. If there is too much insoluble material, carefully transfer the specimen into a mixture of 80% 'fresh' acid and 20% 'spent' acid to prevent partial dissolution of phosphatic minerals (Jeppsson et al, 1985;Kim and Park, 2008;Bonde and Leal, 2015;Graham and Allington-Jones, 2015).…”