MOPPING up river pollution might not always be a good idea. A little sewage
may protect wildlife by locking up toxic metals.
George Luther of the University of Delaware in Lewes and his colleagues
examined samples from 20 rivers on the eastern seaboard of the US. They found
that sulphides, which mostly come from sewage, can “mop up” metals by
imprisoning them in sulphide clusters. The clusters trap common metals such as
iron, zinc and copper, as well as more toxic metals such as silver, cadmium and
mercury.
The complexes consist of hexagonal rings of sulphides around the
metals—structures that…
