『Abstract
In order to understand the contribution of geogenic phosphorus
to lake eutrophication, we have investigated the rate and extent
of fluorapatite dissolution in the presence of two common soil
bacteria (Pantoea agglomerans and Bacillus megaterium)
at T = 25℃ for 26 days. The release of calcium (Ca), phosphorus
(P), and rare earth elements (REE) under biotic and abiotic conditions
was compared to investigate the effect of microorganism on apatite
dissolution. The release of Ca and P was enhanced under the influence
of bacteria. Apatite dissolution rates obtained from solution
Ca concentration in the biotic reactors increased above error
compared with abiotic controls. Chemical analysis of biomass showed
that bacteria scavenged Ca, P, and REE during their growth, which
lowered their fluid concentrations, leading to apparent lower
release rates. The temporal evolution of pH in the reactors reflected
the balance of apatite weathering, solution reactions, bacterial
metabolism, and potentially secondary precipitation, which was
implied in the variety of REE patterns in the biotic and abiotic
reactors. Light rare earth elements (LREE) were preferentially
adsorbed to cell surfaces, whereas heavy rare earth elements (HREE)
were retained in the fluid phase. Decoupling of LREE and HREE
could possibly be due to preferential release of HREE from apatite
or selective secondary precipitation of LREE enriched phosphates,
especially in the presence of bacteria. When corrected for intracellular
concentrations, both biotic reactors showed high P and REE release
compared with the abiotic control. We speculate that lack of this
correction explains the conflicting findings about the role of
bacteria in mineral weathering rates. The observation that bacteria
enhance the release rates of P and REE from apatite could account
for some of the phosphorus burden and metal pollution in aquatic
environments.』
1. Introduction
2. Materials and methods
2.1. Fluorapatite seed preparation and characteristics
2.2. Biomass choice and preparation
2.3. Batch dissolution experiments
2.4. Biomass collection
2.5. Chemical analysis and data treatment
3. Results and discussion
3.1. Cell growth during apatite dissolution
3.2. Dissolved major element concentrations
3.3. Dissolution rate
3.4. Dissolved REE distribution patterns
3.5. Accounting for sorption of elements to bacteria in dissolution
reactions
4. Summary and conclusions
Acknowledgements
References