I want to determine the activity of extractable Cu (pCu2+) and Pb (pPb2+) in the soil to evaluate their toxicity potential after some period of aging. Can someone provide a detail protocol to go about this? It will be highly appreciated.
Thanks
Mr Clement ;
Excuse me for my English is weak, but was answering a simple background on the subject .
However I can say that the scientific method to estimate the effects of toxic heavy and trace elements in the soil in four points:
1-Sampling
A - taken soil samples for most purposes to a depth of 20 cm where research showed the presence of micro-nutrients in such samples associated with plant growth and nutrient absorption.
B - preferred sampling in some cases, especially in irrigated areas within the depth 60-100 cm and special monitoring laundered nitrates and salinity. (Soil and plant analysis laboratory indicatins Written by: John Wayne et al., International Center for Agricultural Research ICARDA 2003)
2-Estimate the heavy elements
Measuring are heavy elements from the soil extracts digested by Atomic Absorption and within the wavelengths for each element by entering standard concentrations.
3- Determinants of heavy metals in the soil
I do not know a Specific determinants of certified limits allowed for the measurement of trace elements in agricultural land so it can be relied upon to compare the results of tests of soil analysis models.
However, there are accredited by the World Health Organization determinants (WHO) has been adopted .
4- values set for the concentration of heavy metals in the soil
Standard specific values:
Cadmium = 1-3
Copper = 50-140
Nickel = 30-75
Lead = 50-300
Zinc = 150-300
Mercury = 1-1.5
chrome ---
Note: The values reflected mg / kg dry matter of the soil with a PH 7-6
Source: council of europeon communities (CEC) (the source of this is supported by the World Health Organization / Regional Office for the Eastern Mediterranean / activities of the Regional Center for Environment / Amman, Jordan Health 2003 / report the use of waste water in agriculture / heuristic guide for planners ).
Dr.Clement,You may please consult the following publication
Determination of lead and cadmium concentration limits in agricultural soil and municipal solid waste compost through an approach of zero tolerance to food contamination .Saha Jayanta Kumar,Panwar,N.R. and Singh,M.V. Environ. Monit.Assess. August 07,2009 .DOI 10.1007/s10661-009-1122-3
Unless you are absolutely sure that your samples do not contain any additional toxic substance (a practical impossibility) , you will only be able to determine with the bioassay of your choice the toxicity og the whole extract. Even if you could be sure that your sample only contains Cu and Pb, you would only be able to determine the joint toxicity of copper and lead.
The attached may be of some interest for the extraction protocol
Thank you all for your comments. Actually, what I want to know is the details procedure for determination of toxicity acitivitiea of CaCl2-extractable Cu 2+ using Cole-Parker combination electrode. And subsequently determining the activities by the MINEQL+ as described by McBride and Cai (2015). I found it difficult to follow and understand their procedures.
The toxicity potential depends on the kind of green plant you want to growm, and the part of the plant you want to use. Some can store much in the roots, some also in the Wood, others transport it to the leaves and finally loose it there. Most of mobile soil fractions may correlate with plant uptake, but the slope depends on the Kind of plant and the respective organ. Copper is the metal ion which usually has the tightest bounds to humic matter - thus toxicity also depends on organic carbon. Lead is rather immobile and frequently fixed in the roots. Phosphorus fertilization fixes lead, but not the copper. If the pH gets more alkaline, fixation of lead is more pronounced than copper. A lot of Details cannot be given within a short statement. Most conclusive will be a suitable pot Experiment - but do not bias it by pH-changes from fertilization!
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