River Danube at Risk

A number of people have emailed me asking about the chemical nature of the sludge and its potential impact.  Little has been posted about the exact composition of the sludge except that it is very alkaline ( up to pH 13) and contains heavy metals including cadmium and chromium although in low concentrations.  These wastes are also generally rich in fluoride, sulphate and of course aluminate, but other metals such as nickel, manganese, lead arsenic etc. are also present.  Of course it is also rich in ferric oxide which gives the sludge its distinctive red colouration. The sludge now has entered the Danube which is 2,850 kilometers long and so provides a huge potential dilution for the pollution.  Croatia, Serbia and Romania have all begun testing the river every few hours with high pH values initially reported (pH 9-10) making ammonia a critical problem as it shifts into its unionized form.  Key impacts are suspected to be sedimentation of the solids, ammonia and aluminum toxicity (until pH neutralizes) and possible metal interactions.