HEAVY METALS AND PLATINUM GROUP METALS (PGMS) DETERMINATION IN OYSTERS, MUSSELS AND CLAMS AS BIO-MONITORS OF THE AQUATIC SYSTEM POLLUTION

A rapid diffusion of heavy metals as environmental contaminants has called the attention to their determination. Indeed, heavy metals, together with pesticides, are very dangerous pollutants owing to their bioaccumulation and toxicity. It is therefore necessary to determine these metals at trace and ultra-trace level especially in aquatic ecosystems to establish reasonable water quality criteria. Moreover, toxic metals accumulate in certain marine species and thus enter the aquatic food chain. In particular mussels and clams, but also oysters, shrimps, fish and algae, sequestrate and concentrate several metals from their aqueous environment, possibly becoming dangerous to human health in consequence of their consumption. In particular mussels, clams and oysters, being filtering organisms - an adult organism is able to filter also up to 4-5 L h-1, depending on its weight - they require particular attention and inspections before being sold on the market. In addition to this important and fundamental aspect of public health, the determination of heavy metals in mussels and clams, that are not only filtering organisms but also sessile species, can be usefully employed for bio-monitoring campaigns, that evaluate the long-term trend of the pollution load of an aquatic ecosystem, information that evidently cannot be provided by punctual determinations. For completely mapping environmental pollution, the sampling duration and cadence are very important. In our opinion, the use of bio-monitors (mussels and clams in the present case), just proposed by several authors, but certainly not scientifically supported, is possible only in the case of a long sampling plan. In any case, the metal determination in mussels and clams evidently must be accurate, reproducible and especially it must show very low limits of detection. The present work reports and discusses the different analytical methodologies for the voltammetric and spectroscopic determination of heavy metals (copper, lead, cadmium, zinc, mercury, arsenic, selenium, tin and antimony) in oysters, mussels and clams. A separate section will be dedicated to the analytical procedure for the determination in such organisms of new emerging anthropic polluting traffic-related pollutants, i.e., the platinum group metals (platinum, palladium, rhodium, osmium, ruthenium and iridium).