To study differences in the effects of microorganisms on weathering of calcite and apatite, one strain of Aspergillus niger (A. niger) and one strain of Penicillium glaucum (P. glaucum), which respectively contain the mixture of calcite and apatite were cultivated for 24 days in the sucrose-potato culture medium, supernatant was taken every three days from the culture medium, followed by the determination of Ca2+ and Sr2+ contents and Sr isotopic ratios. The results of measurement showed that the Sr isotope ratios in the supernatant from the culture medium are intermediate between those of the end-member constituents calcite and apatite (0.70721-0.70861). Results of isotope mixing equations to calculation showed that in the first 15 days A. niger played a dominant role in weathering of calcite in the apatite/calcite mixture. The contribution rate of apatite for Ca2+ in the solution increased from 39.0% on the 18th day to 61.6% on the 24th day; P. glaucum played a key role in weathering of apatite in the first 3 days. Ions dissolved from apatite account for 73.9% of the total. It is known from the results of Sr isotope tracing that in the prior period of fungus cultivation A. niger plays a key role in weathering of calcite while P. glaucum plays a key role in weathering of apatite. The ability of P. glaucum to weather calcite tends to intensify progressively over time. Therefore, Sr isotope tracing can be used to accurately recognize differences in the effects of microorganisms on weathering of minerals.

Publication name	GEOMICROBIOLOGY JOURNAL　Volume: 29 　Issue: 7 　Pages: 640-647　 Published: 2012
Author(s)	Chen, S.; Lian, B.; Zheng, H. Y.; Dong, F. Q.
Corresponding author	CHEN, S  crick_chen@hotmail.com  1. Minist Educ, Key Lab Waste Solid Treatment & Resource Recycle, Mianyang 621010, Peoples R China  2. Chinese Acad Sci, State Key Lab Environm Geochem, Inst Geochem, Guiyang, Peoples R China

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