LI Qiong-fang¹, DONG Fa-qin², LI Qi-yan¹, DAI Qun-wei², AN De-Jun³, HENRY Teng-hui⁴

1. The School of Life Science and Engineering, Southwest University of Science and Technology, Mianyang, Sichuan 621010, China;
2. Key Laboratory of Solid Waste Treatment and Resource Recycle, Ministry of Education, Mianyang, Sichuan 621010, China;
3. Huanglong National Scenic Spot Administration, Songpan, Sichuan 623300, China;
4. Department of Chemistry, The George Washington University, Washington D. C. 20052, USA

Abstract: To explore the impact and the participation degree of biotic factors in the sedimentation process of the Huanglong travertine, the typical extracellular organic acid, citric acid, isolated from two psychrotrophic bacteria strains from Huanglong, were used as object in this study. The temperature and the pH value were simulated as those of Huanglong water environments. Scanning electron microscope (SEM) and X-ray diffraction (XRD) were used to characterize the crystal form and morphology of CaCO3 precipitation. Then calcification process and the effect of citric acid on the crystal form and morphology of CaCO3 were investigated. The results were as followed: ① High concentration, low pH value and low temperature inhibited the calcification in a certain extent. ② Calcite was obtained in the presence of citric acid, and the petaline shaped precipitation formed when the concentration of citric acid became high. ③ Thombic particles switched to ellipsoids with curved edges as the pH value increased. In summary, the typical extracellular organic acids of Huanglong psychrotrophic bacteria affected calcification rate, morphology and polymorphism of CaCO3. The results provided evidences for the biogenic theory of the Huanglong travertine.

Keywords: CaCO3 deposition Huanglong citric acid calcification rate morphology and polymorphs

*Corresponding Author, E-Mail: liqiongfang1992@126.com

Bulletin of Mineralogy, Petrology and Geochemistry Vol. 34, No.2, 2015, page 294-300