In order to evaluate the extent of a natural enrichment of Fe and Mn over the whole of the Hunchun Basin, the stability of Fe-Mn mineral phases, their status, the weathering rate of source materials, and soil characteristics were determined. A variety of samples were collected from sediments, soil profiles, and surface soils. In the solutions after a sequentially selective dissolution using sodium pyrophosphate (p), acid oxalate (o), and dithionite-citrate-bicarbonate (d), Si, Al and Fe were dominant in the d and p fractions, and Mn in the o and p fractions. The results showed that the existing phases and status of Fe and Mn were distinctly different, and that the abundance of amorphous Mn phases made thermodynamic calculation difficult. An application of these ferruginous weathering products was therefore made to understand basin development. The first terrace of the Hunchun River is more active than the second terrace, which can be inferred from it having a higher value in Fed/Fet. Amorphous Fe phases such as Fe(OH)3 and Fe3(OH)8 were controlling factors of Fe in the thermodynamic calculations. The transformation of the amorphous Fe phases to more stable phases was hindered by high contents of smectite and gibbsite, amorphous opaline produced from rice roots, and organic phosphate pesticides or fertilizers in soils. Source-rock deduction using water samples suggested granitic weathering. Precipitation around the Hunchun Basin is gradually becoming more acidic. Therefore, in the future it is inevitable that ecological and environmental problems related to the Fe phases mentioned above will occur in the drinking water supply for this area, especially in that of the first terrace.
Bibliographical noteFunding Information:
Acknowledgements This research was financially supported by the Brain Korea 21 Project, and also partly by the KOSΖF of Korea (grant no. 985-0400-003-2) and the NNSFC (National Natural Science Foundation of China). The authors thank Dr. Suk Ηoung Πee at the Θniversity of Tennessee for his constructive review, and would like to express their appreciation to the members of the Twelve Ζxploration Company in Hunchun City for their help in the field survey. The comments of the anonymous reviewers were greatly appreciated.
All Science Journal Classification (ASJC) codes
- Environmental Chemistry
- Water Science and Technology
- Soil Science