• exchangeable inorganic nitrogen;
  • inorganic nitrogen release;
  • kinetics;
  • middle and lower reaches of Yangtze River region;
  • sediment composition


Inorganic nitrogen (IN) release kinetics and exchangeable inorganic nitrogen (EIN) of the sediments from shallow lakes in the middle and lower reaches of the Yangtze River region were investigated. The results showed that the EIN contents of the studied sediments ranged from 131 to 274 mg/kg. With the increase of the total nitrogen (TN) contents, their EIN also significantly increased. Their ratios of EIN to TN ranged from 5 to 17%, and with the increase of their TN contents, their ratios decreased. The relative contribution of NH4+-N and NO3-N to EIN ranged from 83 and 11% to 89 and 17%, respectively. The curves of the NO3-N release kinetics of the studied sediments were not completely consistent with those of IN and NH4+-N. The amounts of the IN released from sediments not only relate to their EIN contents, but also to other N fractions.