Study On Nitrous Oxide Flux Across The Sediment-Water Interface In Estuary

The water quality of Nanjiushui River and Licun River are investigated from August 2004 to June 2005. The annual change of the nitrous oxide across the sediment-water interface and its influence factors are also studied. The conclusions are as followings.Nitrate concentration in Nanjiushui River and Licun river show a tendency to lower from upstream to downstream. The maximum of nitrate concentration all appear in December 2005 at six sampling sites and the nitrate concentration show obviously seasonal changes. The nitrite concentration in Nanjiushui River and Licun River also show obviously seasonal changes, the maximum of nitrite concentration all appear in August 2004 at six sampling sites. Nitrite concentration in Licun River also show a tendency to lower from upstream to downstream, but this tendency does not exist in Nanjiushui River. The organic carbon concentration in sediment of these two rivers does not exist obviously seasonal change. For Nanjiushui River, the maximum of organic carbon concentration appears at the lower reaches of the river; and for Licun River, the maximum of organic carbon concentration appears at the middle reaches of the river.Using NO₃^-,NO₂^-,PO₄^-,BOD₅,COD and NH₄-N as the assessment targets, the quality of Nanjiushui River and Licun River were assessed. Licun River is seriously polluted, mainly beyond the levelâ…¤. The main pollution factors are the COD_Cr and BOD₅.The quality of water does not show obvious seasonal change. The quality of water in rainy season is not significantly different from that in the dry season. Compared with Licun River, the water quality at the upper reaches of Nanjiushui River is relatively better. It was seriously polluted during summer, such as August in 2004 and June in 2005, mainly at levelâ…£. The main pollution factor is the CODCr. But during spring, autumn and winter, the water quality is much better, mainly at levelâ… .At the middle reaches and the lower reaches in Nanjiushui river, the water quality are seriously polluted, mainly beyond the levelâ…¤. The main pollution factors are the COD_Cr and BOD₅.