Hi Netsanet,

I can think of two reseaons:

The watershed contains a significant amount of iron-bearing soil and rock and the region gets severe rainfalls or thunderstorms, which strongly dissolve iron into the water. Or it could be the result of industrial wastes.

Hope this helps!

Ebrahim

Dear Mrs. Muluneh,

the Fe content is not abnormally high elative to what is known from the mean value of the Earth´s crust. The crucial question is simply that: What is the mineralogy of your stream sediments like? Did you investigate the stream sediment after having split it into different size fraction and did you determine especially the clay and heavy minerals? It may be geogenic and anthropogenic material which causes an increase of Fe from slags to detrital Fe-bearing minerals. All of them show different solubilities. Moreover it is essential to see whether it is a "red" or "black" river or in other words are there agents causing more oxidizing or reducing conditions. Without an answer to these essential questions it remains an area for wild speculations which will not help you make great progress in your studies.

Looking forward to your clarifications

H.G.Dill

Dear Netsanet,

I would like to try to shift the attention here a bit to dynamics through time: The discrepancy between the volume of Fe dissolved in the water of the river you're investigating and the ammount of Fe detected in the underlying soil or sediments could - in theory - be due to the Fe only being released relatively recently into the river water and thus not yet having fully accumulated in the sediment. That's just one possibility, of course. What are the most likely sources for the Fe in the river water in your assessment?

With best wishes,

Julius

Dear all,

Thank you for your suggestions. The river has a brownish color. I did not analyze ORP so I couldn't tell if the river has more oxidizing or reducing condition. Some agricultural activities are taking place around the river. Besides, the authority carries out periodic evaluation on the water quality and high Fe concentration is continually detected . I came to believe that either the geology of the area or the agricultural activities might be releasing iron to the water. And as the environmental conditions change, like pH and ORP, iron might be transferring from water to sediment and vise versa.

Thank you all!

I would like to remind you of the low solubility of Fe in its trivalent state without organic complexes as a carrier (chelates). The other part of the story is the heavy mineral aspect be it driven by arificial or natural input.

There exists a lot of questions still awaiting answers in this complex aquatic stystem.