Sewage sludge is included in this section due to the high water content of such samples, which require similar pretreatment for trace-level organics to those discussed above for sediment samples. The material, however, has a high organic content and so digestion is necessary before any metal analysis is carried out. Typically, this would involve heating with concentrated nitric acid in a Kjeldahl apparatus (see Figure 5.3) and extraction of the metal ions after dilution with water.
What are the relative merits of investigating metal or insoluble organic compound pollution in a river or sea by:
(a) analysis of the water;
(b) analysis of the sediment;
(c) analysis of seaweed
(d) analysis of the fish or shellfish?
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