The equation goes like this Igeo = log2 [Cn/1.5Bn] where Bn is the background level of the metal n. Where are those backgrounds levels? It seems they vary from one place to another, but I'm not really sure. Some authors explains that the quantity of the index is calculated using the global shale data from Turekian and Wedepohl (1961). And others did the calculation "using Fe and grain size < 0.063 mm" and there is the funny part cause I understand nothing. Can someone please explain this to me? thank you.
Dear Hiram
I have used Muller's geochemical index several times. I have used the values of shale for this purpose. There are variety of shale! variety of people whom developed average values? However, I somehow believe that the best way is to develop local background by chemical partitioning techniques. I have done it for my area of study and the paper of such background value development is attached.
Truly yours
karbassi
Dear Hiram,
You're right, but the actual value as background level is obtained by collecting background samples. In fact, the background level for each area comes from the intact samples which indicate non-pollution level of the area. Other standards like mean element value of global shale is just a global standard when you want to compare your collected samples (especially shale samples) with. You are severely recommended to prob the study area for determining some places not to being polluted. You can also calculate pollution deposition rate after industrialization which is different for each area. Hence, maybe you need to collect sediment core samples. Thus fell free, they are only the global standards for comparing. Your aim is to determine pollution level of the study are, requiring to identify non-pollution level of the study area which is just distinguished by collecting intact samples. As well the Geochemical index introduced by Muller is on the basis of Global Shale. You can also present a modified formula regarding your study area. I mean the coefficient 1.5 in the forementioned index is not precisely generalized any area and/or any background. some times you can remove the coefficient 1.5 with respect to local background and/or attend a new coefficient for the modified formula. I hope my comments has been valuable for you.
Kind regards, MJN
· Geoaccumulation Index (Igeo) = Log2 (Cn) / 1.5 (Bn)
Cn is the concentration of metals examined in soil samples and Bn is the geochemical background concentration of metal (n) (Bn : 2.1 ppm for arsenic). Factor 1.5 is the background matrix correction factor due to lithospheric effects. The geoaccumulation index consists of seven grades or classes [20]. Class 0 (practically uncontaminated):Igeo ≤0; Class 1 (uncontaminated to moderately contaminated): 0
Review this paper: Analyzing soil contamination status in garage and auto mechanical workshops of Shashemane City: implication for hazardous waste management
Guys, I really appreciate your answers, to all of you. They were very very helpful, now it is time to apply what I learned. Greetings and thank you so much.
Good morning,
As a background value i suggest using values determined before human industrial/agricular activity. It may be possible that you have some maps with concentrations of given metals in study area.
It is better than average value for earth surface, because this indicates natural state in given area which can be variable.
La forma más segura es tomar un Núcleo de Sedimento, suficientemente profundo (+ de 1 m) en el sitio de interés y determinar los valores background del sitio.
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