『Abstract
　Ammonium release from sediments has significant effects on the water quality in eutrophic lakes. In this study, the ammonium release kinetics and adsorption-desorption processes were investigated in 13 sediments of 6 shallow lakes from the middle and lower reaches of Yangtze River region, China. The results show that First Order Model best described the ammonium release process, the maximal release capacity had a strong correlation with organic matter (OM), cationic exchange capacity (CEC), total nitrogen (TN) and total phosphorus (TP). But it only had a weak correlation with Fe, Ca and Al. The ammonium release capacity in more polluted sediments was higher than that in less polluted sediments. The average release rate within 0-5 min was the highest among the experimental period, the amount released within 0-5 min accounted for approximately 50-70％ of the total release capacity. he ammonium release rate had a significant and positive correlation with OM. But it did not have a strong correlation with TN, TP, Fe, Ca and Al. The ammonium potential release capacity (obtained when the water/sediment ratio was about 2,500) had strong and positive relation with OM and maximal release capacity, and it may provide useful information for the sediment release risk assessment. Henry Model best described the ammonium sorption isotherms, and ammonium adsorption-desorption equilibrium concentration can be considered as the ammonium release threshold to assess the release risk in the sediments

Keywords: Ammonium; Release; Kinetics; Lake; Sediments』

Introduction
Area description, materials and methods
　Study area and sediment sampling
　Ammonium release kinetics experiments
　ammonium potential release capacity
　Ammonium adsorption-desorption equilibrium concentration
Results and discussion
　Ammonium release kinetics
　　Ammonium maximal release capacity
　　ammonium release rate
　Ammonium potential release capacity
　Ammonium adsorption-desorption equilibrium concentration
Conclusions
Acknowledgments
References