Often oxidation states are hard to tell apart, but in this case nature was kind: V (+2) is purple, V (+3) green, V (+4) blue, and V (+5) yellow.
The transition from closed to open
state often leads to extensive physical and chemical changes in the estuarine conditions, as water mixing and sediment resuspension are increased, which could result in the
oxidation of sediment acid - volatile sulfides (AVS).