Abstract: Batch adsorption experiment was conducted to study the effects of seawater pH, Cl^-, SO₄^2-, NO₃^- and HCO₃^- on the adsorption of cadmium on goethite. It was found that cadmium adsorption on goethite was highly pH dependent. The cadmium adsorption was suppressed by Cl^-, SO₄^2- and NO₃^- at pH 8, but enhanced by Cl^- and SO₄^2- at low pH. HCO₃^- promoted the cadmium adsorption at pH 4-10. The order of cadmium and SO₄^2- addition at pH 8 was found to strongly affect the adsorbed amount of cadmium. Much larger amount of cadmium was adsorbed on goethite when cadmium was added first, compared to the conditions when SO₄^2- was added first or when cadmium and SO₄^2- were added simultaneously.

Key words: N₂O emission, Controlled release fertilizer, Urea, Paddy field