Hello Peter,

you need to analyse the sediment with an ICP to determine the concentration of metals in it. You have two options:

1-Partial acid digestion (with HNO3 supposed to extract the metals on the surface of sediment particles)

2-Total acid digestion (with HNO3 + HF or HCl to digest the sediment particles and be able to analyse the metals within the sediment rock).

Sometimes, if you use the elutriate for your toxicological assays (i.e. sea urchin embryotoxicity assay), you can measure the metals directly in the water phase of the sediment.

Hope it helps,

Regards,

Andrea

Dear Peter,

Background values of metals can be calculated by sediment core analysis. The sediment core collected (50 to 150 cm long, according to the condition of area, sedimentation rate, and history of the region) from the study area. Then, slicing the core with the certain interval (2, 5, 10, 15, 25, 50, 75 cm and so on) and each sub-sample analyzed for isotope dating and metal concentrations.

For example, a 75cm layer of sediment deposited 100 or 150 years ago in your area of study, and this time duration there is no or less industrial advancement was recorded in this area, thus, in this layer the metals concentrations possibly showed background metal concentrations in your area. This approach is considered to be more reasonable than a comparison with average crustal values, due to the differences in the geochemistry of a particular area.

But, if it is not possible for you, then you can also take the background values of metals from the Earth's average values of clay for sedimentary rocks reported by Turekian and Wedepohl (1961) or the average crust abundances by Taylor (1964). This is also widely used the method to determine the metal contamination in sediment.

Regards,

Asmat Siddiqui

The sediment core analysis may really not reveal the background values of metals. It is well known that as we go deeper in a sediment core the environmental deposition changes from oxic one to anoxic one. Thereby, some metals may tend to move upwards under reducing conditions (so called mobile elements such as Mn). Thus chemical partitioning techniques might be more useful for you studies. You can find many literature on chemical partitioning techniques in various published papers.