Microscopic local structures of Zn（Ⅱ） were studied using extended X-ray absorption fine structure （EXAFS） spectroscopy under different pH conditions. When pH

<

7.0

Zn

2+

（aq） was coordinated with six water molecules and the average Zn-O distance was measured to be 2.08A

which indicated that hydrated Zn

2+

（aq） ions were in octahedral geometry under acid conditions. Under alkaline conditions

Zn

2+

（aq） was coordinated with four water molecules and the average Zn-O distance was measured to be 1.96A

which indicated that hydrated Zn

2+

（aq） ions were in tetrahedral geometry. EXAFS results provided detailed information on the form and microscopic structure of hydrated Zn（Ⅱ） ions under different pH conditions

which were fundamental for understanding the reactivity of Zn（Ⅱ） in solutions and at particle-water interfaces.