In the inorganic states iron is not very mobile. However when chelated by organic materials such as fulvic and humic acids the inorganic states are mobilized in the presence of aqueous solutions since the fulvic and humic acids work as excellent chelators that increase solubility. . For this reason, the heavy metals will tend to accumulate along with sediment and organic material. The presence of higher metal with the high organic matter does not necessarily mean those heavy metals will be absorped to cause issues in either the plants or the animals which are grown from these sediments. If the crop medium however became acidified heavy metal toxicities would be a real possibility. In any area where the gross content of heavy metals are suspect care must be taken to ensure acidification is controlled. 

Hi Nezha

Iron oxides and organic matter do not control the concentration of heavy metals in sediments.

The concentration is always the same regardless of the presence of  iron oxides, organic matter, pH or cations (when in equilibrium). Other than equilibrium is not worth mentioned.

What those parameters control  (organic matter, iron oxide, etc) is the availability of such metals and the equilibrium with the soluble phase. In other words how much of the heavy metal in the sediment will be released and how much will be bound.

Have a look a this publication:

https://www.researchgate.net/publication/273324320_Consideration_of_the_bioavailability_of_metalmetalloid_species_in_freshwaters_experiences_regarding_the_implementation_of_biotic_ligand_model-based_approaches_in_risk_assessment_frameworks

Article Consideration of the bioavailability of metal/metalloid spec...

 Dear Nezha

i hope this Theses will find your well and answer your question.

Regards

Polla

Hi,

Thank you for your prompt responses to my question

Regards

Dear researcher

You can use these files.

Regards

check this link...

https://www.google.ca/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0ahUKEwiCzIST4PXUAhWFFT4KHYAVCjkQFgglMAE&url=http%3A%2F%2Fwww.mdpi.com%2F2073-4441%2F8%2F8%2F358%2Fpdf&usg=AFQjCNEryPMhQuO22Y_JzYddVuFrjuoD7Q

Hello Nezha,

to answer your question thoroughly it is important to know which type of sediments you mean (e.g. stream sediments, lake s., residual s., marine s.). Considering your topics (Heavy Metal Pollution etc) I suppose you are dealing with and your question concerns pollution by stream and lake sediments. Originating from mining activities or industrialized areas stream sediments can contaminate vast areas of flooding plains and conaminants can be transported many hundreds of kilometers or they can be trapped in lakes. When scrutinizing heavy metal contents of sediments you have thoroughly to discriminate between geogenic and anthropogenic portions. Only the latter can be addressed as contamination. Whereas the geogenic portion occurs as stable silicates and oxides the anthropogenic portion consists of unstable bonding forms (adsorbed to e.g. clays, bound to Fe-oxides-hydroxides, bound to organic matter). High amounts of Fe-oxides-hydroxides go constantly along with high amounts of unstable heavy metal portions in the sediments (significant positive correlation). This affinity is especially true for elements which tend to form mineralizations along with Fe (like Ni, Cr, Co, Zn; As). The specific element combination is due to chemisorption or/and coprecipitation. In the very same sediment samples Pb and Cu show tendencies to be bound to organic matter. However, in this portion also sulfides occur and so these elements also could occur as sulfides. As you see your question is not so easy to be answered thoroughly and there are still many open questions in the details the solution of which still requires a lot to do. Also, the type of sediment and changes in environment must be taken in account. Possibly you will find some more ideas when looking at some of my publications archivated in RG, e.g. studies on sediments of River Elbe (Germany), River Tisza (Hungary), Pampulha Lake (Brazil), and adsorption studies on arsenic by Fe-hydroxide.

Good luck and regards D. Zachmann

Dear Nezha Mejjad,

Iron Oxide content doesn't control the availability of heavy metals in sediments. Having said that, you need to ascertain the nature and type of sediments depending on the nature and type of sorbent (in this case sediment). Remember, when you are talking about organic matter in these sediments, you must understand the fact that, equilibrium conditions are already reached. Hence, we cannot rely on such general conclusions as well..

The right way to do it is: Extract the solution from the site and impart a little bit of organic matter (exhibiting similar nature and conditions as those from the area under consideration) and see whether there is any change in the solute concentration (i.e., heavy metal ions under consideration). If there is any change i.e., decrease in the solute concentrations for the metal ions under consideration, then bingo, you have hit the chord..

Best Wishes,

Prof. Arif Ali Baig Moghal