Comparative analysis of weathering rate of serpentine by microbial pure culture and field burial tests: A case study

The process of mineral weathering in nature is usually accompanied by biological actions, however, current laboratory studies on pure culture weathering minerals of various microorganisms (e.g., bacteria and fungi) lack comparisons on quantitative weathering indicators such as weathering rate or capacity with each other, let alone with in situ mineral weathering in the field. In this present research, to establish weathering models under different conditions and to conduct a quantitative comparative analysis, a specimen test method was used to study the weathering ability of serpentine under different types of microorganisms in the laboratory and field conditions. The results showed that, based on the weight loss of the test specimens and the change in the con-centration of released Mg2+, the order of serpentine weathering rate was: Aspergillus niger > Esherichia coli > Bacillus subtilis > field tests. Accordingly, the amount of mineral weathering under natural conditions was compared with the amount of mineral weathering of experimentally pure cultured microorganisms and quan-titative relations were established. The weathering ability of microorganisms cultured in the laboratory is much stronger than that under field conditions, because laboratory culture conditions are more suitable for microbial growth, which is very different from the environment in which those microorganisms grow in the field being usually in the state of starvation or semi-starvation. This study is expected to provide new ideas for estimating the effects of mineral weathering in the field over a longer time scale by using short-term laboratory weathering results.