Studies on the concentration of iron and its characteristics in reservoirs

Abstract

The iron concentration and its size fraction were investigated in 15 reservoirs which trophic levels varied from oligotrophic types to eutrophic ones. The T-Fe concentration ranged from 0.021 to 2.349 mg· 1^-1, and the average value of the concentration from the all samples (n=123) was 0. 200 mg· l^-1, The D-Fe (<0.45μm size) concentration was about 20% of T-Fe, but someti-mes appeared to be above 50% when the T-Fe concentration was relatively low. The relationship between T-Fe and Chlorophyll-a was not clear enough to obtain a specific correlation as compared with that of T-P or T-N and Chlorophyll-a. One significant factor of this scatter was the difer-ence of the iron contents between algal cell particle (0.24%) and non-algal cell particle (3. 9%).
The D-Fe (<0.45μm size) concentration showed poor relationship with DOC which was quantitative index of desolved organic matters. On the other hand, better relationship was showed with E260 or DOC/E260 value which were qualitative index of desolved organic matters.
The examination of the three fraction of iron under the size of 1.0 /μm size showed that about 20% of the iron was the size of both 1. 0-0. 45μm and 0. 45-0. 10μm, and also 60% was size of less than 0.10μm. It suggested the concentration of D-Fe must be carefully defined by the physical sieving size for the consideration of algal availability of iron.